CA1223306A - Method and apparatus for diagnosis of coronary artery disease - Google Patents
Method and apparatus for diagnosis of coronary artery diseaseInfo
- Publication number
- CA1223306A CA1223306A CA000431615A CA431615A CA1223306A CA 1223306 A CA1223306 A CA 1223306A CA 000431615 A CA000431615 A CA 000431615A CA 431615 A CA431615 A CA 431615A CA 1223306 A CA1223306 A CA 1223306A
- Authority
- CA
- Canada
- Prior art keywords
- slope
- coronary artery
- artery disease
- exercise
- subject
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Landscapes
- Measuring Pulse, Heart Rate, Blood Pressure Or Blood Flow (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
Method and apparatus for recurrently obtaining a measure of the systolic slope of the blood pressure wave in a subject's artery during a range of physical activity. or exercise, are dis-closed. A plot, or record, of the slope measurements versus heart beat rate, point in an exercise protocol. or the like, is provided from which subjects having coronary artery disease (CAD) may be distinguished from subjects without CAD.
Method and apparatus for recurrently obtaining a measure of the systolic slope of the blood pressure wave in a subject's artery during a range of physical activity. or exercise, are dis-closed. A plot, or record, of the slope measurements versus heart beat rate, point in an exercise protocol. or the like, is provided from which subjects having coronary artery disease (CAD) may be distinguished from subjects without CAD.
Description
~33~)~
RELATED PATENT
The sub;ect matter of this application is related to United Stfltes Patent No. 4,408,614 entitled "BLOOD PRESSURE MEASUREMENT WIT~I
KOROTKOV SOUND ARTIFACT INFORMATION DETECTION AND REJECTION", assigned to the same assignee as the present invention.
_CKGROUND OF THE INVENTION
Numerous means for obtaining blood pressure measurements are known including both invasive and noninvasive means. A number of noninvasive measuring means are disclosed in an article by C.S. Weaver, J.S. Eckerley, P.M. Neugard~ C.T. Warnke, J.B. Angell, S.C. Terry and J. Robinson, entitled "A Study of Non-invasive Blood Pressure Measurement Techniques" presented at a conference held at Stanford University in September, 1978 and published by the Society of Photo~Optical Instrumentation Engineers.
The use of pulse rate and rhythm measurements as well as measurements of systolic and diastolic blood pressure in the diagnosis of cardiovascular disease has long Been known. Electro-cardiograph (ECG~ measurements also are of well known diagnosticsignificance in heart disease. However, to-date, the value of the use of measurements of the systolic slope of arterial blood pressure waves of a subject before, during and af~er exercise as compared to such me2surements obtained from a healthy person has not been recognized in the diagnosis of coronary artery disease (CAD).
SUMMARY OF THE INVENTION AND_OBJECTS
An object of the present invention is the provision of improved diagnostic method and apparatus for the improved diagnosis of coronary artery disease.
An object of the present invention i8 the provision of im-proved diagnostic method and apparatus of the above-mentioned type which provides a measure of heart contractility of a subject dur-ing a range of exercise.
The above and other objects and advantages of this invention are obtained by recurrently obtaining a measure of the time rate of change in the intra-arterial pressure of a subject during systole (i.e. systolic slope of blood pres~ure waves in an artery of a subjeot) before, during and after exercise performed by the subject. Actual values of these measurements at di~erent times in the exercise protocol, as well as certain changes therein dur-ing the exercise protocol are determined and compared to corres-ponding measurement~ obtained from persons without known CAD for diagnosis af CAD in ths subject.
One means for obtaining recurrent ~easures of the systolic slope of the arterial blood pre sure waves includes the use of an inflatable cuff which is inflatable to a pressure above 6ystolic pressure and deflatable to a pressure below diastolic pressure. A
pressure transducer is connected to the inflatable cuf~f for gener-20 ating a signal which i8 a function of cuff pressure. A micro-phone aetects Korotkov sound6 during defla~ion of the ouff, and electrodes attached to the subject pick-up electrocardiograph signals. A K-sound detector detects Korotkov sounds from the microphone and an R-wave peak detector detects the peak of the 25 ECG R-wave. The K-sound and R-waYe signals from the dete tors are conYerted to signals for use by a computer, and the pre~sure transducer output i~ converted to di~ital form for transfer to the 3~
computer and ~torage in the computer memory. The R-wave and X-sound signals may be supplied as interrupt signals to the co~puter~
with the time of arrival of such signals being stored in the com-puter memory. Alternatively, ECG and/or Korotkov sound waveforms 5 may be digitized and input to software R-wave and/or K-sound de-tectors in the computer with the time of arrival of the software detected R-waves and/or K-sounds being stored in the computer mem-ory. The time intervals between the time of arriv~l of the R-wave signals and the associated K-sound signals durîng a cuff deflation are determined by the computer and ths resultant RK intervals and associatad cuff pressures are stored in the computer memory. ~he RK intervals are processed to discriminate betwean true Korotkov sounds and artifacts. Using minimum mean-squared fitting tech-niques, a straight line is *itted by th~ computer to the collec-tion of true RK interval versus cuff pressure points, which linehas a slope inversely proportional to the systolic slope of the arterial blood pre~sure wave. During a range of exercise a plural-ity of such "RK-slope" measurements are obtained~ These measure-ments, and changes therein, obtained during an e~ercise protocol 20 are compared to corresponding measurements and change~ therein o`o-tained from healthy subjects for the diagnosis of coronary artery disease (CAD) in the subject.
BRIE~ DESCRIPTION OF THE DRAWINGS
The in~ention will be better understood from the following 25 dssoription when considered with the accompanying drawings. In th~
drawings, wherei~ like reference characters refer to tha sa~s parts in the several view~l ~33~3~
Fig. 1 is a plot of an electrodardiographic signal and an associated arterial blood pressure wave showing RK intervals;
measurement~ of which are made using the system shown in Fig. 3 Figs. 2A and 2B each show graphical representations of arterial blood pr~ssure waves at different -times during a range of exercise for subjects without and with, respectivaly, coronary artery disease;
Fig. 3 is a simplified block diagram of a sy3tem for re-currently obtaining a measure of the systolic slope of a blood pressure wave and for displaying said measurements, which system embodies the present invention;
Fig. 4 is a plot of RK interval as a function of cuff pressure for use in explaining the operation of the system shown in Fig. 3~
Figs. 5A -5D are graphs o~ measurements of slope versus heartbeat rate fox sub~ects with no known coronary artery disease Figs. 6A-6D are graphs which are similar to those shown in Fig9. 5A-5D for subjects Xnown to have coronary artery disease;
Fig. 7 is a flow chart for use in explaining operation of 20 the 8y8tem shown în Fig. 3~
Fig. 8 shows graphs of measurement~ of "RK-slope" versus time for a subj~ct with and a subject without coronary artery dis ease; and Fig. 9 shows details of a step of the ~low chart of Fig. 7 25 wherein various parameters of the systolic slope mea~urements are . employed by the computer for use in identifying subjects with CAD.
~2;~3~
Reference first i8 made to Fig~ 1 wherein portions of an electrocardiograph signal 10 and associated brachial artery pre3-sure wave 12 are shown. In accordance with the present invention, recurrent measurements o~ the systolic slope of the pressure wave are made during an exercise routine. Measurements of the slope together with measurements of certain changes therein which occur during ~he course of an exercise protocol are evaluated based on corresponding measurements obtained from other subjects with and without known coronary artery disease (CAD~ for diagno3is of -the 10 disease. Various methods for obtaining a measure of the systolic slope are known in the art, including those described in the above~
mentioned Weaver et al article. Apparatus of this invention which makes use of one of the slope-measuring methods disclosed in the article iB shown in Fig. 3 and described below. First, however, systolic slopes of subjects without CAD and subjects with CAD shown in Figs. 2A and 2B, respectively, will be described, together with some differences therein useful in the diagnosis of CAD. The sys-tolic slopes depicted in Pig. 2B are representative of many, but not all, types of CAD, and are shown for purposes of illustration only.
Systolic slope portions of pressure waves obtained before, dur-ing and after ~xercise stress are depicted in Figs. ZA and 2B.
For purposes of description, the same refer nce characters arP
used in ~igs. 2A and 2B ~or pressure pulses obtained at the same relative time during an exercise protocol, except for the use of a~ the suffi2es A and B in Pigs, 2A and 2B, respectively. ~he at rest, be~ore exercise, wave~ are identi~ied by reference characters 20A and 20B. ~oth of these waves show systolic and diastolic pressures which are considered to be within normal ranges thereof.
~Z23~6 The systolic slope of the waves, however, differ, with the systolic slope o~ pressure wave 20A being greater than that of pressure wave 20B. Typically, the pre-exercise, resting. systolic slope fo~
subjects with CAD is less than that of subjects without CAD.
Pressure waves 22A-1~ 22A-2 and 22A-3 shown in Fig. 2A are typical of those observed after 2, 4 and 6 minutes, respectively, of exercise. For the subject without CAD, it will be seen that the systolic slope slowly increases with increasing exercise.
Although not seen in Fig. 2A, with increasing exercise the systolic 10 slope generally increases to a maximum value, and remains sub-stantially at said value during continued exercise.
As seen in Fig. 2B, representative pressure waves ~4~
24B-2 and 24B-3 during exercise ~or a subject with CAD show an increase in the systolic slope with ~xercise, followed by a de-15 crease therein with further exercise. When the left ventriclecontracts, not all of the blood is ejected therefrom~ Typically, when a subject i8 at rest, only 50 parcent is eject~d. Th~ ejec-tion percentage, divided by 100, i8 the ejection fra~tion (EF).
EF can be measured by injecting a radioactive solution into the 20 blood and then "photographing" the left ventricle with a radio-nuclide camera at a rate of approximately 30 to 40 photographs per second. These photograph~ allow the size of the left ventricle to be determined at a number of points during a heart beat, ~rom whic~
determinations of EF can be calculated. Except for a dangerous 25 technique whereby an X-ray dye is injected directly into the coronary arteries, ~F measurements during exercise heretofore have provided the most accurate ~lown indicators of CAD~ Typically, a healthy subject's EP will gradually increase during ~xercise, while that ~f a subject with CAD, fir3t will in r~ase, and then 3~ decreases. It is commonly believed that thi~ decrease i8 due to a ~3~6 decrease in heart contractility. A lower heart contractility lowers the systolic slope o~ the pressure pulse in the brachial artery. Simultane~us radio-isotope EF and systolic slope measure-ments have been made on subjects with and without CAD and the above-5 described correlation between the ~F and slope measurements ha~been observed.
After exercise other ditferences in the changing systolic slope patterns between healthy subjects and subjects with CAD
often are observed, and are illustrated in Figs. 2A and 2B. Pres-10 sure waves 24A-1, 24A-2 and ~4A-3 are typical of a healthy subject observed 2, 4 and 6 minutes, respectively, after exercise.
Immediately following exercise, the sy~tolic slope remains sub-stantially the same as the slope immediately before the end Or exorcise, and then 910wly decreases with tima to the pre-exercise, 15 resting slope. This patte~n i3 in contrast to that observed in many subjects with CAD wherein, after exercise, the systolic slopa often decreases beneath the pre-exercise, resting, slope before returning to such pre-exerciss slope. Pressure wave 24B-3 in Fig.
2B, at 6 minutes after exercise, is seen to have a systolic slope 20 lass than that of the pra-exercisa wava 20B. As noted above, such a low systolic slope corr~lates with low heart contractility arid low EF and represents an immediate dangerous physical condition.
It here will be noted that although measurements are obtained at corresponding times in the exercise routines for Figures 2A and 25 2B, di~erent effort may be expended by the subject~ during the exercise portion o~ th~ routines. In Figs. 5A-5D ~nd 6A-6D plots o~ measurements o~ systolic alope as a function o~ heart beat ratq are shown wl~ich proYide the phy~ioian with an indication of the amount o~ e~ort exert~d by each subject during the exercise rou~
30 tine.
33~
As noted above, various means are known for measuring blood pressure, and the time-derivative of pressure during the systolic alope which provides a measure of the 910pa. Apparatus ~or obtain-ing a measure of the systolic ~lope of the blood pressure wave em-5 bodying the present inYention i9 shown in Fig. 3, to which refer-enc0 now i9 made. The illustrated apparatus includes an inflatable cuff 30 for encircling a subject's limb, such as upper arm , and a pressure source 32 connected to the cuff through a pressure con-troller 34. Guff pressure i~ sensed by a pressure transducer 36, the analog output from which is connected through an amplifier 38 to the input of an analog to digital converter 40 for conversion to digital signal ~orm. The digitized cuff pressure signal is con-nected through a digital multiplexer 42 to a computer 44 which in-cludes memory 44A where cuff pressure signals obtained during a 15 cuf~ deflation temporarily are 3tored for use in computing a measure of the systolic slope of blood pressure waves during said deflation.
With the cuff 30 attached to the upper arm of the subject, the cuff is inflated to a pressure above systolic pxessure. ~hen, 20 as the cuff pressure is decreased, the first Korotkov sound appears at the systolic pressure, and the last at the diastolic pressure.
A microphone 46 picks up the Korotkov sound (K-sound) at a plural-ity of cuff pressures between systolic and diastolic. The micro-phone output signal i8 amplifi0d by amplifier 48, and the ampli-25 fier output i8 supplied both to a signal converter 50 and to a~-aound detector 52. The converter 50 simply may include a one-~3~
sho-t for ~enexation o~ a pulse output in response to an amplified K-sound output ~rom amplifier 48, which pulse output is connected to the multiplexer 42. The K-sound detector 52 distinguishes be-tween true K-sound and artifact~, and produces an output in re-sponse to said true K-sounds, which output is connected to an addre~s input of the multiplexer. In the presence of an output from the K-sound detector, the output from the convarter 50 is connected through the multiplexer 42 to an interrupt input of the computer 44 to produce a K-sound timing 3ignal which, together with an associated R-wave timing signal, provides a measure o~ the RK
interval.
ECG electrodes 60 attached to the subject's body pick up ECG slgnal~ which are amplified by amplifier 62 and then supplied to a converter 64 and to an R-peak detector 66. As with converter lS 5~ the converter 64 also may incluae a one-shot for generation of a pulse output in response to the R-wave component of the ampli-fied ECG signal. ~he pulse output from the converter 64 i9 con-nected to the multiplexer 42 for connection as an interrupt input to the computer 44. The R-peak detector detect~ tha R-wave of the 20 ECG signsl while discriminating against noise and other component~
such as the P and T wave component~. The R-peak detector output i8 supplied as an addrass input to the multiplexer 42 for connec-tîon of the output from the converter 64 to an interrupt input of the computer 44 when an R ~ave i8 detected. The difference in 25 time between the arriYal of an R wave input ~nd associated K-sound 3ignal at the interrupt inputs to the computer provides a meas~re ~3~6 o~ the RK interval, which int~rval is tempor~rily ~torsd in the computer momory 44A ~or use with other such R~ interval ~alues obtained at di$f~rent ou~f pre~sures for u~e in calculatlng a value rclated to th~ ~y~tolio ~lopa Or the ~ubj~ctls arterial 5 blood pPesaure wavs.
Another address input for the multiplexer 42 i~ obtained from the computer 44 through a eontrol unit 70. Under control o~
unit 70, the m~ltiplexer 42 i~ ~witchcd for connection o~ cuff pressure signala ~rom the A/D convsrter 40 to the computer 44.
10 Also, multiplexer addr~s~ input in~ormatlon i8 supplied to the computer 44 through the ~ontrol unlt 70 ~or U8e by the computer in controlling operatian of the multiplexer. A keyboard 72 may be included ror manual aupply Or inrcr~ation to the computer, 3~ch ~8 the nama o~ ths sub~ect to be tested, ~acts concerning ths ~ub~aot, ~nd various points in the e~arci~e protocol including the staxt and and Or the c~ercise portion the~eof. D~ta di~play and record-ing unit 74 may be used to display nd/or record systolic slope information at di~f~rent axercise lavels of the ~ub~ect. ~a will becom~ apparent, u~ing the ~K int~rval and cu~r pre~sure in~orma-tion, the oo~puter ~ay bæ progra~d to eo~put~ ~ystolic an~ dia~-tolic blocd pressure~ which ~alu~8 al~o ~ay be displayed and/or recorded by unit 74. A system Or the type ohown in Fi~. 3 ror measuring systolio and diaatolic blood pr~s~ura i8 ~hown in the above-mentioned We~r at al art~cla entitled ~ Study of Non~in-
RELATED PATENT
The sub;ect matter of this application is related to United Stfltes Patent No. 4,408,614 entitled "BLOOD PRESSURE MEASUREMENT WIT~I
KOROTKOV SOUND ARTIFACT INFORMATION DETECTION AND REJECTION", assigned to the same assignee as the present invention.
_CKGROUND OF THE INVENTION
Numerous means for obtaining blood pressure measurements are known including both invasive and noninvasive means. A number of noninvasive measuring means are disclosed in an article by C.S. Weaver, J.S. Eckerley, P.M. Neugard~ C.T. Warnke, J.B. Angell, S.C. Terry and J. Robinson, entitled "A Study of Non-invasive Blood Pressure Measurement Techniques" presented at a conference held at Stanford University in September, 1978 and published by the Society of Photo~Optical Instrumentation Engineers.
The use of pulse rate and rhythm measurements as well as measurements of systolic and diastolic blood pressure in the diagnosis of cardiovascular disease has long Been known. Electro-cardiograph (ECG~ measurements also are of well known diagnosticsignificance in heart disease. However, to-date, the value of the use of measurements of the systolic slope of arterial blood pressure waves of a subject before, during and af~er exercise as compared to such me2surements obtained from a healthy person has not been recognized in the diagnosis of coronary artery disease (CAD).
SUMMARY OF THE INVENTION AND_OBJECTS
An object of the present invention is the provision of improved diagnostic method and apparatus for the improved diagnosis of coronary artery disease.
An object of the present invention i8 the provision of im-proved diagnostic method and apparatus of the above-mentioned type which provides a measure of heart contractility of a subject dur-ing a range of exercise.
The above and other objects and advantages of this invention are obtained by recurrently obtaining a measure of the time rate of change in the intra-arterial pressure of a subject during systole (i.e. systolic slope of blood pres~ure waves in an artery of a subjeot) before, during and after exercise performed by the subject. Actual values of these measurements at di~erent times in the exercise protocol, as well as certain changes therein dur-ing the exercise protocol are determined and compared to corres-ponding measurement~ obtained from persons without known CAD for diagnosis af CAD in ths subject.
One means for obtaining recurrent ~easures of the systolic slope of the arterial blood pre sure waves includes the use of an inflatable cuff which is inflatable to a pressure above 6ystolic pressure and deflatable to a pressure below diastolic pressure. A
pressure transducer is connected to the inflatable cuf~f for gener-20 ating a signal which i8 a function of cuff pressure. A micro-phone aetects Korotkov sound6 during defla~ion of the ouff, and electrodes attached to the subject pick-up electrocardiograph signals. A K-sound detector detects Korotkov sounds from the microphone and an R-wave peak detector detects the peak of the 25 ECG R-wave. The K-sound and R-waYe signals from the dete tors are conYerted to signals for use by a computer, and the pre~sure transducer output i~ converted to di~ital form for transfer to the 3~
computer and ~torage in the computer memory. The R-wave and X-sound signals may be supplied as interrupt signals to the co~puter~
with the time of arrival of such signals being stored in the com-puter memory. Alternatively, ECG and/or Korotkov sound waveforms 5 may be digitized and input to software R-wave and/or K-sound de-tectors in the computer with the time of arrival of the software detected R-waves and/or K-sounds being stored in the computer mem-ory. The time intervals between the time of arriv~l of the R-wave signals and the associated K-sound signals durîng a cuff deflation are determined by the computer and ths resultant RK intervals and associatad cuff pressures are stored in the computer memory. ~he RK intervals are processed to discriminate betwean true Korotkov sounds and artifacts. Using minimum mean-squared fitting tech-niques, a straight line is *itted by th~ computer to the collec-tion of true RK interval versus cuff pressure points, which linehas a slope inversely proportional to the systolic slope of the arterial blood pre~sure wave. During a range of exercise a plural-ity of such "RK-slope" measurements are obtained~ These measure-ments, and changes therein, obtained during an e~ercise protocol 20 are compared to corresponding measurements and change~ therein o`o-tained from healthy subjects for the diagnosis of coronary artery disease (CAD) in the subject.
BRIE~ DESCRIPTION OF THE DRAWINGS
The in~ention will be better understood from the following 25 dssoription when considered with the accompanying drawings. In th~
drawings, wherei~ like reference characters refer to tha sa~s parts in the several view~l ~33~3~
Fig. 1 is a plot of an electrodardiographic signal and an associated arterial blood pressure wave showing RK intervals;
measurement~ of which are made using the system shown in Fig. 3 Figs. 2A and 2B each show graphical representations of arterial blood pr~ssure waves at different -times during a range of exercise for subjects without and with, respectivaly, coronary artery disease;
Fig. 3 is a simplified block diagram of a sy3tem for re-currently obtaining a measure of the systolic slope of a blood pressure wave and for displaying said measurements, which system embodies the present invention;
Fig. 4 is a plot of RK interval as a function of cuff pressure for use in explaining the operation of the system shown in Fig. 3~
Figs. 5A -5D are graphs o~ measurements of slope versus heartbeat rate fox sub~ects with no known coronary artery disease Figs. 6A-6D are graphs which are similar to those shown in Fig9. 5A-5D for subjects Xnown to have coronary artery disease;
Fig. 7 is a flow chart for use in explaining operation of 20 the 8y8tem shown în Fig. 3~
Fig. 8 shows graphs of measurement~ of "RK-slope" versus time for a subj~ct with and a subject without coronary artery dis ease; and Fig. 9 shows details of a step of the ~low chart of Fig. 7 25 wherein various parameters of the systolic slope mea~urements are . employed by the computer for use in identifying subjects with CAD.
~2;~3~
Reference first i8 made to Fig~ 1 wherein portions of an electrocardiograph signal 10 and associated brachial artery pre3-sure wave 12 are shown. In accordance with the present invention, recurrent measurements o~ the systolic slope of the pressure wave are made during an exercise routine. Measurements of the slope together with measurements of certain changes therein which occur during ~he course of an exercise protocol are evaluated based on corresponding measurements obtained from other subjects with and without known coronary artery disease (CAD~ for diagno3is of -the 10 disease. Various methods for obtaining a measure of the systolic slope are known in the art, including those described in the above~
mentioned Weaver et al article. Apparatus of this invention which makes use of one of the slope-measuring methods disclosed in the article iB shown in Fig. 3 and described below. First, however, systolic slopes of subjects without CAD and subjects with CAD shown in Figs. 2A and 2B, respectively, will be described, together with some differences therein useful in the diagnosis of CAD. The sys-tolic slopes depicted in Pig. 2B are representative of many, but not all, types of CAD, and are shown for purposes of illustration only.
Systolic slope portions of pressure waves obtained before, dur-ing and after ~xercise stress are depicted in Figs. ZA and 2B.
For purposes of description, the same refer nce characters arP
used in ~igs. 2A and 2B ~or pressure pulses obtained at the same relative time during an exercise protocol, except for the use of a~ the suffi2es A and B in Pigs, 2A and 2B, respectively. ~he at rest, be~ore exercise, wave~ are identi~ied by reference characters 20A and 20B. ~oth of these waves show systolic and diastolic pressures which are considered to be within normal ranges thereof.
~Z23~6 The systolic slope of the waves, however, differ, with the systolic slope o~ pressure wave 20A being greater than that of pressure wave 20B. Typically, the pre-exercise, resting. systolic slope fo~
subjects with CAD is less than that of subjects without CAD.
Pressure waves 22A-1~ 22A-2 and 22A-3 shown in Fig. 2A are typical of those observed after 2, 4 and 6 minutes, respectively, of exercise. For the subject without CAD, it will be seen that the systolic slope slowly increases with increasing exercise.
Although not seen in Fig. 2A, with increasing exercise the systolic 10 slope generally increases to a maximum value, and remains sub-stantially at said value during continued exercise.
As seen in Fig. 2B, representative pressure waves ~4~
24B-2 and 24B-3 during exercise ~or a subject with CAD show an increase in the systolic slope with ~xercise, followed by a de-15 crease therein with further exercise. When the left ventriclecontracts, not all of the blood is ejected therefrom~ Typically, when a subject i8 at rest, only 50 parcent is eject~d. Th~ ejec-tion percentage, divided by 100, i8 the ejection fra~tion (EF).
EF can be measured by injecting a radioactive solution into the 20 blood and then "photographing" the left ventricle with a radio-nuclide camera at a rate of approximately 30 to 40 photographs per second. These photograph~ allow the size of the left ventricle to be determined at a number of points during a heart beat, ~rom whic~
determinations of EF can be calculated. Except for a dangerous 25 technique whereby an X-ray dye is injected directly into the coronary arteries, ~F measurements during exercise heretofore have provided the most accurate ~lown indicators of CAD~ Typically, a healthy subject's EP will gradually increase during ~xercise, while that ~f a subject with CAD, fir3t will in r~ase, and then 3~ decreases. It is commonly believed that thi~ decrease i8 due to a ~3~6 decrease in heart contractility. A lower heart contractility lowers the systolic slope o~ the pressure pulse in the brachial artery. Simultane~us radio-isotope EF and systolic slope measure-ments have been made on subjects with and without CAD and the above-5 described correlation between the ~F and slope measurements ha~been observed.
After exercise other ditferences in the changing systolic slope patterns between healthy subjects and subjects with CAD
often are observed, and are illustrated in Figs. 2A and 2B. Pres-10 sure waves 24A-1, 24A-2 and ~4A-3 are typical of a healthy subject observed 2, 4 and 6 minutes, respectively, after exercise.
Immediately following exercise, the sy~tolic slope remains sub-stantially the same as the slope immediately before the end Or exorcise, and then 910wly decreases with tima to the pre-exercise, 15 resting slope. This patte~n i3 in contrast to that observed in many subjects with CAD wherein, after exercise, the systolic slopa often decreases beneath the pre-exercise, resting, slope before returning to such pre-exerciss slope. Pressure wave 24B-3 in Fig.
2B, at 6 minutes after exercise, is seen to have a systolic slope 20 lass than that of the pra-exercisa wava 20B. As noted above, such a low systolic slope corr~lates with low heart contractility arid low EF and represents an immediate dangerous physical condition.
It here will be noted that although measurements are obtained at corresponding times in the exercise routines for Figures 2A and 25 2B, di~erent effort may be expended by the subject~ during the exercise portion o~ th~ routines. In Figs. 5A-5D ~nd 6A-6D plots o~ measurements o~ systolic alope as a function o~ heart beat ratq are shown wl~ich proYide the phy~ioian with an indication of the amount o~ e~ort exert~d by each subject during the exercise rou~
30 tine.
33~
As noted above, various means are known for measuring blood pressure, and the time-derivative of pressure during the systolic alope which provides a measure of the 910pa. Apparatus ~or obtain-ing a measure of the systolic ~lope of the blood pressure wave em-5 bodying the present inYention i9 shown in Fig. 3, to which refer-enc0 now i9 made. The illustrated apparatus includes an inflatable cuff 30 for encircling a subject's limb, such as upper arm , and a pressure source 32 connected to the cuff through a pressure con-troller 34. Guff pressure i~ sensed by a pressure transducer 36, the analog output from which is connected through an amplifier 38 to the input of an analog to digital converter 40 for conversion to digital signal ~orm. The digitized cuff pressure signal is con-nected through a digital multiplexer 42 to a computer 44 which in-cludes memory 44A where cuff pressure signals obtained during a 15 cuf~ deflation temporarily are 3tored for use in computing a measure of the systolic slope of blood pressure waves during said deflation.
With the cuff 30 attached to the upper arm of the subject, the cuff is inflated to a pressure above systolic pxessure. ~hen, 20 as the cuff pressure is decreased, the first Korotkov sound appears at the systolic pressure, and the last at the diastolic pressure.
A microphone 46 picks up the Korotkov sound (K-sound) at a plural-ity of cuff pressures between systolic and diastolic. The micro-phone output signal i8 amplifi0d by amplifier 48, and the ampli-25 fier output i8 supplied both to a signal converter 50 and to a~-aound detector 52. The converter 50 simply may include a one-~3~
sho-t for ~enexation o~ a pulse output in response to an amplified K-sound output ~rom amplifier 48, which pulse output is connected to the multiplexer 42. The K-sound detector 52 distinguishes be-tween true K-sound and artifact~, and produces an output in re-sponse to said true K-sounds, which output is connected to an addre~s input of the multiplexer. In the presence of an output from the K-sound detector, the output from the convarter 50 is connected through the multiplexer 42 to an interrupt input of the computer 44 to produce a K-sound timing 3ignal which, together with an associated R-wave timing signal, provides a measure o~ the RK
interval.
ECG electrodes 60 attached to the subject's body pick up ECG slgnal~ which are amplified by amplifier 62 and then supplied to a converter 64 and to an R-peak detector 66. As with converter lS 5~ the converter 64 also may incluae a one-shot for generation of a pulse output in response to the R-wave component of the ampli-fied ECG signal. ~he pulse output from the converter 64 i9 con-nected to the multiplexer 42 for connection as an interrupt input to the computer 44. The R-peak detector detect~ tha R-wave of the 20 ECG signsl while discriminating against noise and other component~
such as the P and T wave component~. The R-peak detector output i8 supplied as an addrass input to the multiplexer 42 for connec-tîon of the output from the converter 64 to an interrupt input of the computer 44 when an R ~ave i8 detected. The difference in 25 time between the arriYal of an R wave input ~nd associated K-sound 3ignal at the interrupt inputs to the computer provides a meas~re ~3~6 o~ the RK interval, which int~rval is tempor~rily ~torsd in the computer momory 44A ~or use with other such R~ interval ~alues obtained at di$f~rent ou~f pre~sures for u~e in calculatlng a value rclated to th~ ~y~tolio ~lopa Or the ~ubj~ctls arterial 5 blood pPesaure wavs.
Another address input for the multiplexer 42 i~ obtained from the computer 44 through a eontrol unit 70. Under control o~
unit 70, the m~ltiplexer 42 i~ ~witchcd for connection o~ cuff pressure signala ~rom the A/D convsrter 40 to the computer 44.
10 Also, multiplexer addr~s~ input in~ormatlon i8 supplied to the computer 44 through the ~ontrol unlt 70 ~or U8e by the computer in controlling operatian of the multiplexer. A keyboard 72 may be included ror manual aupply Or inrcr~ation to the computer, 3~ch ~8 the nama o~ ths sub~ect to be tested, ~acts concerning ths ~ub~aot, ~nd various points in the e~arci~e protocol including the staxt and and Or the c~ercise portion the~eof. D~ta di~play and record-ing unit 74 may be used to display nd/or record systolic slope information at di~f~rent axercise lavels of the ~ub~ect. ~a will becom~ apparent, u~ing the ~K int~rval and cu~r pre~sure in~orma-tion, the oo~puter ~ay bæ progra~d to eo~put~ ~ystolic an~ dia~-tolic blocd pressure~ which ~alu~8 al~o ~ay be displayed and/or recorded by unit 74. A system Or the type ohown in Fi~. 3 ror measuring systolio and diaatolic blood pr~s~ura i8 ~hown in the above-mentioned We~r at al art~cla entitled ~ Study of Non~in-
2~ ~asive Blood Pr~s~ure ~ea3urement ~echniquse.
3~
~ow~ver, the relationship between systolic slope as a ~unction of exercise ~tress and CAD is not disclosed in the article, nor are means for the diagllosis o CAD using measurements of the systolic slope, and changes in the slope, disclosed therein.
Reference again is briefly made to Fig. 1 wherein the re-lationship between systolic slope of the blood pressure wave 12 and RK interval is shown~ The RK interval, i.e. the time inter-val between the occurrence of the R wave peak and the associated K-sound, is maximum at systolic pressure and minimum at diastolic 1O pressure. As the cuff pressure is decreased from systolic, the RE interval also decreases. As is well understood, the K-30unds are of maximum amplitude intermediate the uppsr and lower ends of the systolic slope and gradually decrease to zero at systole and diastole.
.
~ ~23~
During cuff deflation, a plurali-ty of RK interval measure-ments are obtained, and 8 plot of such measurements as a function of cuff pressure i~ shown in Fig. 4 to which reference now is made. There, a straight line 80 is shown ~itted through the series S of points using minimu~ mean-sguared error fitting techniques readily implemented by use of the computer. The slope, ~ RX-interval / ~pressure, Or the line iæ inversely proportional to the systolic slope of the blood pressure wa~e, as depicted in Fig.
1 and, there~or, provides a measure of the systolic ~lope of the 10 blood pre~sure wava. Obviously, as the systolic slope increases, the slope o~ line 80 decreases, and vice ~ersa. It here will be noted that in the above-mentioned Weaver et al article, the slope of the straight line 80 is determined and utilized in a progr~m for di~tinguishing bet~een true Korotkov ~ounds and artifacts. The lS maximum and minimum cu~ pres~ures at which true ~orotkov sounds ~re obtained provide a ~easure o~ the systol~c and diastolic blood pressures, respectively~ as seen in Flg. 4. The same process disc~osed in the Weaver et al article may be used in the present invention to distingui~h between true Korotkov sounds and arti-20 facts in order that a true measure o~ the systoIic slope ~ay b~obtained. It here will be noted that knowledge o~ the systolic and diastolio blood pressures is not required in ths practice of the present inYention. There~ore, in the use o~ the apparatus of Fig. 3, the slope o~ th~ line 80 may ~e established using only 25 points ad~acent the center of the line 80, and not those adjacent .
33~6 the opposite ends thereof where the Korotkov sounds are much weaker. Of cour3e, the apparatus may be used for measuring systol~
ic and diastolic blood pre3sures, and such pressures may be dis-played and/or recorded or stored along with the diastolic slope measurements, if desired. Since the present invention i8 not æpecifically directed to the method of distinguishing between true Korotkov sounds and artifacts, it will be understood that such artifacts are removed by suitable processing of the signals from the detector 52, and that points in the plot of Fig. 4 to which the straight line 80 is fitted are obtained using true KorotXov sounds, not artifacts.
For each cuf~ deflation a series of points are obtained, as shown in Fig. 4, through which the straight line 80 is fitted.
The slope of such line is readily calculated by the computer.
15 Using the times of occu~nce of the R-peak waves, the time inter-val between ad~acent R-peak waves i8 determined, and the recipro-cal thereof i8 calculated to provide a measure of heart rate dur-ing the cuff deflationO During an exercise cycl~, or protocol, the above-described operation iB repQ~sd whereby a plurality of 2~ values of slope a~ a function of heart beat measurement, or of time, are obtained, ~hich values may be displayed and/or recorded at display and/or recording un;t 74 of Fig. 3. In the present application, the the RK interval versus cuff pressure slope (i.e.
slope of line 80 of Fig. 4) is referred to as RK slope, for con-25 ~enience.
~;~Z33~6 Re~srence now i8 made to Figs. 5A-5D and Figs. 6A-6D
wherain records o~ the type which may be provided by the present ~ystem are ~hown. In particular, the slope o~ the traight line ~itted to the measured points for sach cuf~ deflation (i.e. RX
slope) as a ~unction of he~rt rate i9 plotted. Dat~ for these plots of Figs. 5A-~B was obtained from four healthy subjects having no known CAD while thoss of Figs. 6A-6D have CAD. The symbol X marks the point obffained with the subject at rest, before Qxercise. Points obtained during exercise are identified by the symbol ~, and tho~e obtained after exercise are identified by the ~ymbol 0. Points for the plots were obtained at two-minute intervals, which intervals may be programmed in the computer 44, or enter0d through the keyboard 72. It will be understood that substantially continuous measurements may be made. and plotted, 15 there being no requirement ~or the two-minute spacing between measurement3. A clock 44B, shown in Fig. 3, is included to pro-vide time measurements.
From Figs. 5A-5D, it will be noted that tha RX intexral/
cu~f pressure slope (RKslope) for the ~our healthy sub~ects at 20 rest, before exercise, is within the range of approximately .6 to 1.5. For subjects with known CAD, the resting slope generally equals or exceeds 2, a~ aeen in Fig3. 6A-6C. Since sys-tolic BlOpe i8 inversely related to thP illustrated slope, it will be seen that the resting systolic ~lope ~or a subject with known CAD
is generally equal to or les~ than .5. Xowever, in Fig. 6D, the sub~ect with CAD is shown to havs a normal Rtarting ~lope o~
approximately 1.
~2.2~33~6 During exercise, the RK slope for healthy subject3 de-crea~.es substantially exponentially to a value slightly above zaro, as shown in Figs. 5A-5D. Sinca the RK 310pe i8 inversely proportional to the systolic slope o~ the blood pressure wave, 5 this indicates that the ~ystolic 810pe increases to near-vertical.
The undulating nature of the plot o~ RK slope shown in Fig. 5B
during e~ercise is not typical of healthy Fubjects.
For CAD subjects, the RK slope also generally decreases during exercise, a~ ssen in Figs. 6A, 6~ and 6C but neYer reaches 10 levsls as low as those reached by healthy subjects. In one CAD
case, illustrated in Figs. 6D, there was essentially no change in slope during the entire cycle whibh too is unlike the change in slope observed in hsalthy subjects.
After exercise, the R~ slope for healthy subjects, shown in 15 Figs. 5A-5D9 810wly returns to the pre-exerciae level, while r~-maining generally wlthin the upper and lower limits xeached during exercise. For most subjects with CAD (Figs. 6A-6C) the slope rapidly ri~es during the post-exercise period. Often, the post-exercise ~lope exceeds the pre-exercise slope, as seen in Figs.
20 6A-6~, which means that tha syst~icF.lope of the brachial artery pulse is low, as is the ejection fraction EP. As mentioned a~ove, in the one CAD case illustrated in Fig. 6D, the post_exercise slope did not signi~icantly changs.
3~3~
Although the operation of the system shown in Fig. 9 for obtaining a m~asure of the 8y8tolic slope during an exercise cycle i9 believed to be apparent, a brie~ description thereof with ref-erence to the rlow chart of Fig. 7 now will be provided. rarious operation~ indicated therein are under control of the computer 44, responsive to programming instructions contained in memory 44A.
Obviously, one or more progr = ing steps may be involved in the actual imp].ementation of the indicated operation. Since the programming o~ such step3 for the indicated operationa i~ well 10 within th0 skill of th~ average programmer, a complete program li~ting is not reguired and i8 not included herein.
With the cuff 30 and transduceri 46 and 60 properly Recured to the subject/ the te~t is ~tarted as indica-ted by START
step l.OO, at which time system power i8 -turned on or a rQset operation is performed, by means not shown. Initialization step 102 includes initial setting o~ counters, register3 and the llk~
in the computer 44. Information concerning the sub~ect, such a~
the sub~ect'3 name, may be entered through the keyboard 72 at 3tep 104. At step 106, the stage, or portion, o~ the exerci e 20 cycle to be atarted by the subject iR entared by ~eans o~ the keyboard. For example, st the beginning o~ the te~t, the word "pre-exerc1se" may be entexed.
2;:~3~
With the subject on a treadmill, stationary bicycle, or the like, cu.ff in~lation s-tep 108 is entered whereln the cuff 30 is inflated under contxol of the computer to a pressure above systolic blood pressure through operation o~ the cuff pressure controller 34 to occlude blood ~low in the brachial ~rtery. Next, at step 110, the cu~ pressure is reduced to a pres~ure at~which true Korotkov, or artifact, sound3 are first detected, which, for true Korotkov sounds, i9 the sy~tolic blood pressure. At this point, the cuff pressure i~ entered into the computer memory 44A through 10 use of tran~ducer 36, amplifier 38, A/D converter 40 and digital multiplexer 42, as indicated by step 112.
Next, at step 114, an R-peak wave is detected and its time o~ arrival is entered in the computer memory. The time of arrival o~ an associated Korotkov sound also is entered into the computer memory. As noted above, in addition to the detection of true Eorotkov sounds, ~he ~-sound detèctor 52 may also respond to art-ifacts, in which case the time of arrival of such artifacts also is entered into the computer memory. For any ~iven R-peak wave the time of arrival Or the true K-sound and that of one or more rtifacts may be stored.
At ~tep 116, the RK-interval i~ calculated, and the RK-interval value, or values, are stored (~tep 118) with the ~80Cia-ted cuf~ pressure. The cuff pressure, at 3tep 120, i~ then ra-~uced an incremental amount o~, ~a~ 4mmHg. The deci~ion step 122 25 next is performed to datermine whether or not outputs are produced ~rom the K-sound detector 52. If not, it i~ known that cu~ pres-~ure hae been reduced beneath diastolic pre~sure. If the decision i~ af~irmative, i.e~ that ~-~ounds are 3~6 still being datected, ~tep 112 is again entered, whereupon the new reduced cuff pressure value i8 stored, together with new assocI~ted RK-interval values. When cuff pressure is reduced below diastolic pressure at which time K-sounds no lon~er are detected, decision step 122 is negativP, and step 124 i8 entered whereupon heart rate is calculated using a count of the R-peak waves. The heart rate is calculated for the preceeding period between cuff in~lation and cuff deflation during which a series of RK-intervals at declining cuff pressures i obtained. At step 126, true Korotkov sounds are distinguished from artifacts, and such artifacts are daleted ~rom further processing. In any system~
including the present, in which Korotkov sounds ara detected, other sounds also are detected by the K-sound detector, particularly when the subject i~ exercising and such artifacts must be elimin-15 ated from the true Korotkov sounds in order to obtain an accuratemeasure of the systolic ~lope. As noted above, algorithms for discrimin~tlng between true Korotkov sounds and artifacts are included in the above-mentioned Weaver e~ al article.
Using a minimum mean-squared algorithm, a straight line is 20 fitted to the RK intervals obtained ~rom true XorotXov sound~ as indicated at step 128, and the slope of said line i~ calculated at step 130. At step 132, using the slope calculated at ~tep 1~0 and heart rate calculated at step 124, a point i8 recorded on a slope ~ersu~ heart rate plot (o. a type ~hown in Figs. 5A-5D and 25 6A-6D). The decision st~p 134 then i~ entexPd at which point a decision i~ made a~ to whether or not the te~t is to be continued.
Keyboard switches, not shown, may ba included ~or ~anual entry o~
the d0cision into the computer 44. I~ the decision is rade to continue the te~t, step 106 is reentered, at which point the - 30 operator, or physician, may enter tha next ~tage in the exarci~e ~233~
cycle, such as "exercise". The subject then begin3, or continues, that portion of the exercise cycle, and another measure of systol-lc slope is made and added to the plot. If the test is over, step 136, is entered at which point an analy~is is ~ade of the plot by the physician to determine whether or not the plot differs from those of healthy 3ubjects for diagnosis of CAD. The test and diagnosis ends at step 138. It here will be noted that certain steps of the flow chart may be performed in different order.
A number of parameters of, or derived from, the plot of the 10 ~easure of systolic slope (here, RX-interval/cuff pre~sure slope) versus heart rate, time, exercise protocol, or the like, may be used for obtaining a value indicati~e of the subject's heart con-dition. Pertinent parameters which may be obtained from a plot of RK-slope versus time, include the follow~g, some o~ which have 15 been de~cribed above:
1. Resting RK Slops, prior to ex0rcise, 2. Rate at which the RK slope decreases during a period of time immediately following the start of exercise, ~ . Slope of the RK slope versus time plot at the beginning 20 f exercise~
~ow~ver, the relationship between systolic slope as a ~unction of exercise ~tress and CAD is not disclosed in the article, nor are means for the diagllosis o CAD using measurements of the systolic slope, and changes in the slope, disclosed therein.
Reference again is briefly made to Fig. 1 wherein the re-lationship between systolic slope of the blood pressure wave 12 and RK interval is shown~ The RK interval, i.e. the time inter-val between the occurrence of the R wave peak and the associated K-sound, is maximum at systolic pressure and minimum at diastolic 1O pressure. As the cuff pressure is decreased from systolic, the RE interval also decreases. As is well understood, the K-30unds are of maximum amplitude intermediate the uppsr and lower ends of the systolic slope and gradually decrease to zero at systole and diastole.
.
~ ~23~
During cuff deflation, a plurali-ty of RK interval measure-ments are obtained, and 8 plot of such measurements as a function of cuff pressure i~ shown in Fig. 4 to which reference now is made. There, a straight line 80 is shown ~itted through the series S of points using minimu~ mean-sguared error fitting techniques readily implemented by use of the computer. The slope, ~ RX-interval / ~pressure, Or the line iæ inversely proportional to the systolic slope of the blood pressure wa~e, as depicted in Fig.
1 and, there~or, provides a measure of the systolic ~lope of the 10 blood pre~sure wava. Obviously, as the systolic slope increases, the slope o~ line 80 decreases, and vice ~ersa. It here will be noted that in the above-mentioned Weaver et al article, the slope of the straight line 80 is determined and utilized in a progr~m for di~tinguishing bet~een true Korotkov ~ounds and artifacts. The lS maximum and minimum cu~ pres~ures at which true ~orotkov sounds ~re obtained provide a ~easure o~ the systol~c and diastolic blood pressures, respectively~ as seen in Flg. 4. The same process disc~osed in the Weaver et al article may be used in the present invention to distingui~h between true Korotkov sounds and arti-20 facts in order that a true measure o~ the systoIic slope ~ay b~obtained. It here will be noted that knowledge o~ the systolic and diastolio blood pressures is not required in ths practice of the present inYention. There~ore, in the use o~ the apparatus of Fig. 3, the slope o~ th~ line 80 may ~e established using only 25 points ad~acent the center of the line 80, and not those adjacent .
33~6 the opposite ends thereof where the Korotkov sounds are much weaker. Of cour3e, the apparatus may be used for measuring systol~
ic and diastolic blood pre3sures, and such pressures may be dis-played and/or recorded or stored along with the diastolic slope measurements, if desired. Since the present invention i8 not æpecifically directed to the method of distinguishing between true Korotkov sounds and artifacts, it will be understood that such artifacts are removed by suitable processing of the signals from the detector 52, and that points in the plot of Fig. 4 to which the straight line 80 is fitted are obtained using true KorotXov sounds, not artifacts.
For each cuf~ deflation a series of points are obtained, as shown in Fig. 4, through which the straight line 80 is fitted.
The slope of such line is readily calculated by the computer.
15 Using the times of occu~nce of the R-peak waves, the time inter-val between ad~acent R-peak waves i8 determined, and the recipro-cal thereof i8 calculated to provide a measure of heart rate dur-ing the cuff deflationO During an exercise cycl~, or protocol, the above-described operation iB repQ~sd whereby a plurality of 2~ values of slope a~ a function of heart beat measurement, or of time, are obtained, ~hich values may be displayed and/or recorded at display and/or recording un;t 74 of Fig. 3. In the present application, the the RK interval versus cuff pressure slope (i.e.
slope of line 80 of Fig. 4) is referred to as RK slope, for con-25 ~enience.
~;~Z33~6 Re~srence now i8 made to Figs. 5A-5D and Figs. 6A-6D
wherain records o~ the type which may be provided by the present ~ystem are ~hown. In particular, the slope o~ the traight line ~itted to the measured points for sach cuf~ deflation (i.e. RX
slope) as a ~unction of he~rt rate i9 plotted. Dat~ for these plots of Figs. 5A-~B was obtained from four healthy subjects having no known CAD while thoss of Figs. 6A-6D have CAD. The symbol X marks the point obffained with the subject at rest, before Qxercise. Points obtained during exercise are identified by the symbol ~, and tho~e obtained after exercise are identified by the ~ymbol 0. Points for the plots were obtained at two-minute intervals, which intervals may be programmed in the computer 44, or enter0d through the keyboard 72. It will be understood that substantially continuous measurements may be made. and plotted, 15 there being no requirement ~or the two-minute spacing between measurement3. A clock 44B, shown in Fig. 3, is included to pro-vide time measurements.
From Figs. 5A-5D, it will be noted that tha RX intexral/
cu~f pressure slope (RKslope) for the ~our healthy sub~ects at 20 rest, before exercise, is within the range of approximately .6 to 1.5. For subjects with known CAD, the resting slope generally equals or exceeds 2, a~ aeen in Fig3. 6A-6C. Since sys-tolic BlOpe i8 inversely related to thP illustrated slope, it will be seen that the resting systolic ~lope ~or a subject with known CAD
is generally equal to or les~ than .5. Xowever, in Fig. 6D, the sub~ect with CAD is shown to havs a normal Rtarting ~lope o~
approximately 1.
~2.2~33~6 During exercise, the RK slope for healthy subject3 de-crea~.es substantially exponentially to a value slightly above zaro, as shown in Figs. 5A-5D. Sinca the RK 310pe i8 inversely proportional to the systolic slope o~ the blood pressure wave, 5 this indicates that the ~ystolic 810pe increases to near-vertical.
The undulating nature of the plot o~ RK slope shown in Fig. 5B
during e~ercise is not typical of healthy Fubjects.
For CAD subjects, the RK slope also generally decreases during exercise, a~ ssen in Figs. 6A, 6~ and 6C but neYer reaches 10 levsls as low as those reached by healthy subjects. In one CAD
case, illustrated in Figs. 6D, there was essentially no change in slope during the entire cycle whibh too is unlike the change in slope observed in hsalthy subjects.
After exercise, the R~ slope for healthy subjects, shown in 15 Figs. 5A-5D9 810wly returns to the pre-exerciae level, while r~-maining generally wlthin the upper and lower limits xeached during exercise. For most subjects with CAD (Figs. 6A-6C) the slope rapidly ri~es during the post-exercise period. Often, the post-exercise ~lope exceeds the pre-exercise slope, as seen in Figs.
20 6A-6~, which means that tha syst~icF.lope of the brachial artery pulse is low, as is the ejection fraction EP. As mentioned a~ove, in the one CAD case illustrated in Fig. 6D, the post_exercise slope did not signi~icantly changs.
3~3~
Although the operation of the system shown in Fig. 9 for obtaining a m~asure of the 8y8tolic slope during an exercise cycle i9 believed to be apparent, a brie~ description thereof with ref-erence to the rlow chart of Fig. 7 now will be provided. rarious operation~ indicated therein are under control of the computer 44, responsive to programming instructions contained in memory 44A.
Obviously, one or more progr = ing steps may be involved in the actual imp].ementation of the indicated operation. Since the programming o~ such step3 for the indicated operationa i~ well 10 within th0 skill of th~ average programmer, a complete program li~ting is not reguired and i8 not included herein.
With the cuff 30 and transduceri 46 and 60 properly Recured to the subject/ the te~t is ~tarted as indica-ted by START
step l.OO, at which time system power i8 -turned on or a rQset operation is performed, by means not shown. Initialization step 102 includes initial setting o~ counters, register3 and the llk~
in the computer 44. Information concerning the sub~ect, such a~
the sub~ect'3 name, may be entered through the keyboard 72 at 3tep 104. At step 106, the stage, or portion, o~ the exerci e 20 cycle to be atarted by the subject iR entared by ~eans o~ the keyboard. For example, st the beginning o~ the te~t, the word "pre-exerc1se" may be entexed.
2;:~3~
With the subject on a treadmill, stationary bicycle, or the like, cu.ff in~lation s-tep 108 is entered whereln the cuff 30 is inflated under contxol of the computer to a pressure above systolic blood pressure through operation o~ the cuff pressure controller 34 to occlude blood ~low in the brachial ~rtery. Next, at step 110, the cu~ pressure is reduced to a pres~ure at~which true Korotkov, or artifact, sound3 are first detected, which, for true Korotkov sounds, i9 the sy~tolic blood pressure. At this point, the cuff pressure i~ entered into the computer memory 44A through 10 use of tran~ducer 36, amplifier 38, A/D converter 40 and digital multiplexer 42, as indicated by step 112.
Next, at step 114, an R-peak wave is detected and its time o~ arrival is entered in the computer memory. The time of arrival o~ an associated Korotkov sound also is entered into the computer memory. As noted above, in addition to the detection of true Eorotkov sounds, ~he ~-sound detèctor 52 may also respond to art-ifacts, in which case the time of arrival of such artifacts also is entered into the computer memory. For any ~iven R-peak wave the time of arrival Or the true K-sound and that of one or more rtifacts may be stored.
At ~tep 116, the RK-interval i~ calculated, and the RK-interval value, or values, are stored (~tep 118) with the ~80Cia-ted cuf~ pressure. The cuff pressure, at 3tep 120, i~ then ra-~uced an incremental amount o~, ~a~ 4mmHg. The deci~ion step 122 25 next is performed to datermine whether or not outputs are produced ~rom the K-sound detector 52. If not, it i~ known that cu~ pres-~ure hae been reduced beneath diastolic pre~sure. If the decision i~ af~irmative, i.e~ that ~-~ounds are 3~6 still being datected, ~tep 112 is again entered, whereupon the new reduced cuff pressure value i8 stored, together with new assocI~ted RK-interval values. When cuff pressure is reduced below diastolic pressure at which time K-sounds no lon~er are detected, decision step 122 is negativP, and step 124 i8 entered whereupon heart rate is calculated using a count of the R-peak waves. The heart rate is calculated for the preceeding period between cuff in~lation and cuff deflation during which a series of RK-intervals at declining cuff pressures i obtained. At step 126, true Korotkov sounds are distinguished from artifacts, and such artifacts are daleted ~rom further processing. In any system~
including the present, in which Korotkov sounds ara detected, other sounds also are detected by the K-sound detector, particularly when the subject i~ exercising and such artifacts must be elimin-15 ated from the true Korotkov sounds in order to obtain an accuratemeasure of the systolic ~lope. As noted above, algorithms for discrimin~tlng between true Korotkov sounds and artifacts are included in the above-mentioned Weaver e~ al article.
Using a minimum mean-squared algorithm, a straight line is 20 fitted to the RK intervals obtained ~rom true XorotXov sound~ as indicated at step 128, and the slope of said line i~ calculated at step 130. At step 132, using the slope calculated at ~tep 1~0 and heart rate calculated at step 124, a point i8 recorded on a slope ~ersu~ heart rate plot (o. a type ~hown in Figs. 5A-5D and 25 6A-6D). The decision st~p 134 then i~ entexPd at which point a decision i~ made a~ to whether or not the te~t is to be continued.
Keyboard switches, not shown, may ba included ~or ~anual entry o~
the d0cision into the computer 44. I~ the decision is rade to continue the te~t, step 106 is reentered, at which point the - 30 operator, or physician, may enter tha next ~tage in the exarci~e ~233~
cycle, such as "exercise". The subject then begin3, or continues, that portion of the exercise cycle, and another measure of systol-lc slope is made and added to the plot. If the test is over, step 136, is entered at which point an analy~is is ~ade of the plot by the physician to determine whether or not the plot differs from those of healthy 3ubjects for diagnosis of CAD. The test and diagnosis ends at step 138. It here will be noted that certain steps of the flow chart may be performed in different order.
A number of parameters of, or derived from, the plot of the 10 ~easure of systolic slope (here, RX-interval/cuff pre~sure slope) versus heart rate, time, exercise protocol, or the like, may be used for obtaining a value indicati~e of the subject's heart con-dition. Pertinent parameters which may be obtained from a plot of RK-slope versus time, include the follow~g, some o~ which have 15 been de~cribed above:
1. Resting RK Slops, prior to ex0rcise, 2. Rate at which the RK slope decreases during a period of time immediately following the start of exercise, ~ . Slope of the RK slope versus time plot at the beginning 20 f exercise~
4. Increase in RK slope during exercise,
5. Change in RK slope two minutes after exercise ends, 5. Rat0 of change in the RK~slope a~t0r two minutes after exercise ends, and 7. Highest v~lue of RK slope a~ter ex0rcise.
~223~
Typical relative values of the parameters for persons ~ith-out CAD and persons with CAD are given in table I below wherein the parameter numbers correspond to those in the above list of parameters.
S Table I - Typical Relative Parameter Values Parameter ~ Subjects W/O Subject.s with CAD CAD
.
l ~ow High ~ ~arge Small 3 Small Large 4 No Increase Small Increase Decrease Increase
~223~
Typical relative values of the parameters for persons ~ith-out CAD and persons with CAD are given in table I below wherein the parameter numbers correspond to those in the above list of parameters.
S Table I - Typical Relative Parameter Values Parameter ~ Subjects W/O Subject.s with CAD CAD
.
l ~ow High ~ ~arge Small 3 Small Large 4 No Increase Small Increase Decrease Increase
6 Small Large
7 Small Iarge Reference now is made to Fig. 8 wherein a graph, or plot, of measurements of RK 510pe versus time for a subject without CAD
and a subject with CAD are shown, which graph is readily available as an output from the computer. Parameters l and 3-7 are identi-fied cn the graph of the subject with CAD. It will be noted that - 20 the slope o~ the graph during the first seYeral minutes of exer-cise changes substantially exponentially for the subject without CAD. On the other hand, the slope of the graph for the subject with CAD during the same initial time period is substantially constant for approximatel~ two minutes, then abruptly decreases.
25 This rate of decrease of the slope is employed in the evaluation of paramete~ 2.
~33~6 For each of the parameters, threshold values may be set, or ~stablished from an examination of data from a large number of subjects. For example, the threshold for ~arameter 1, the resting RK-slope prior to exercise, is set between the average for persons with CAD and the average for persons without CAD. From an examin-ation of Figs. 5A through 5D for healthy subjects the average resting RK-slope before exercise is on the order of 1.2, and from Figs. 6A through 6D for subjects with known CAD, the a~erage rest-ing slope is on the order of 2.5. A threshold value between these averages of, say 1.8 may be employed~ ~his, and thresholds for the other parameters are stored in the computer memory. For para-meter 1, the computed resting RK-slope i9 compared to the 1.8 threshold value and, if it is less than the threshold it is con-sidered normal. If, as a result of the comparison, the pzrameter is above the threshold, or cut-point, a value of 1 (one~ may be assigned thereto, and if it i~ below the threshold, a value of -1 may be assigned thereto. These outputs are weighted according to the importance o~ the parameter in the diagnosis; with negative weights being assigned to parameters where necessary. The weights~
~0 values for the various parameters simply may be added to provide an overall ~igure indicative of the condition of -the subject's coronary arteries. ~his figure, together with the individual weighted values may be read out from the ~omputer. Such a system i9 well adapted for screening large numbers of subjects ~or CAD.
~223~
It will bs apparent that the parAmeter values may be obtained directly from the plot or graph of the R~-slope versus time and that manual calculation may be employed in tha evaluation, Alternatively, the computer is well adapted for performing such calculations. In Fig. 9, to which re~erence now i3 made, detail~
for the block 136 of the Fig. 7 flow chart are shown for computer evaluation of the RK-slope V8 time information obtained during an exeroise routine of a subject. Parameters 1-7 are determined and/
or evaluat~d and weighted at steps 136-1 through 136-7, respective 1O ly, and at step 136-8 the weighted values are summed, and the results are displayed.
It here will be noted -that a nonlinear discriminant func-tion which i3 not suitable for manual analysis also may be includ-ed in an algorithm for computer avaluation of measured data.
Of course, the invention i9 not limited to the above-de~-cribed algorithmic process. For example. the abova-described parameters can be weighted to indicate the relative abnormality of the heart condition. ~hese weighted values may be summed and the total compared to a cut-point for an indication of a normal or 20 an abnormal condition. Again, Ruch an e~aluation may be per$ormed manually or by the computer based on the data obtained during the exercise routine.
Heart rate can be substituted for time in the above anal-yses. All of the parameters except parameter 2 are de~ined as 25 above. For use with the plot involving heart rate, parameter 2 ie defined as the constant c when the ~unctlon S(r) = Ke~~r ~Z~3~
is ~it to the RK slope versus heart rate data points, where S(r) is the slope, r is the ra~e, and K i5 another constant.
The invantion having been described in detail in accordance with requirements of the patent statutes, various other changes and modifications will suggest themselves to those skilled in the art. Since the slope of RK interval as a function of cuff pre~sure i9 a function of systolic slope, it may be converted to systolic slope which may be plotted aæ a function of time, heartbeat rate, or the like. Another obvious change includes the use of a manually inflatable cuff rather than the illustrated arrangement wherein cuff inflation and deflation are under control of the computer.
Also, as mentioned above and described in the above mentioned Weaver et al article, systolic and diastolic blood prassure meas-urements may be obtained from cuff pressure measurements made when true Korotkov sounds are first heard during a cuff deflation, and are last heard, and these pressures also may be displayed and/or recorded. A~ noted above, the operation of the present apparatu~
does not depend upon determination o~ systolic and diastolic blood pressures.
Also, it will be apparent that inputs may be supplied to the computer from the exercise davics, or the like, u6ed by the subject whereby thc work performed by the subject throughout the exercise cycle may be recorded.
,, .
~2233~
Also, it wi~l be apparent that means other than interrupt inputa may be used to input the time of occurance of the R-peak wave and Korotkov sound to the computer. Either a general purpose or dedioated computer may be employed. Also, a recording of the 5 necessary inputs may be made, and the recording played back to provide the computer inputs. Additionally, it will be apparent that other blood pressure transducers and systems may be used from which a measure of the systolic slope may be obtained, includ-ing, for example, invasive devices. It is intended that the above 10 and other such changes and modifications shall fall within the apirit and scope o$ the invention defined in the appended claims.
and a subject with CAD are shown, which graph is readily available as an output from the computer. Parameters l and 3-7 are identi-fied cn the graph of the subject with CAD. It will be noted that - 20 the slope o~ the graph during the first seYeral minutes of exer-cise changes substantially exponentially for the subject without CAD. On the other hand, the slope of the graph for the subject with CAD during the same initial time period is substantially constant for approximatel~ two minutes, then abruptly decreases.
25 This rate of decrease of the slope is employed in the evaluation of paramete~ 2.
~33~6 For each of the parameters, threshold values may be set, or ~stablished from an examination of data from a large number of subjects. For example, the threshold for ~arameter 1, the resting RK-slope prior to exercise, is set between the average for persons with CAD and the average for persons without CAD. From an examin-ation of Figs. 5A through 5D for healthy subjects the average resting RK-slope before exercise is on the order of 1.2, and from Figs. 6A through 6D for subjects with known CAD, the a~erage rest-ing slope is on the order of 2.5. A threshold value between these averages of, say 1.8 may be employed~ ~his, and thresholds for the other parameters are stored in the computer memory. For para-meter 1, the computed resting RK-slope i9 compared to the 1.8 threshold value and, if it is less than the threshold it is con-sidered normal. If, as a result of the comparison, the pzrameter is above the threshold, or cut-point, a value of 1 (one~ may be assigned thereto, and if it i~ below the threshold, a value of -1 may be assigned thereto. These outputs are weighted according to the importance o~ the parameter in the diagnosis; with negative weights being assigned to parameters where necessary. The weights~
~0 values for the various parameters simply may be added to provide an overall ~igure indicative of the condition of -the subject's coronary arteries. ~his figure, together with the individual weighted values may be read out from the ~omputer. Such a system i9 well adapted for screening large numbers of subjects ~or CAD.
~223~
It will bs apparent that the parAmeter values may be obtained directly from the plot or graph of the R~-slope versus time and that manual calculation may be employed in tha evaluation, Alternatively, the computer is well adapted for performing such calculations. In Fig. 9, to which re~erence now i3 made, detail~
for the block 136 of the Fig. 7 flow chart are shown for computer evaluation of the RK-slope V8 time information obtained during an exeroise routine of a subject. Parameters 1-7 are determined and/
or evaluat~d and weighted at steps 136-1 through 136-7, respective 1O ly, and at step 136-8 the weighted values are summed, and the results are displayed.
It here will be noted -that a nonlinear discriminant func-tion which i3 not suitable for manual analysis also may be includ-ed in an algorithm for computer avaluation of measured data.
Of course, the invention i9 not limited to the above-de~-cribed algorithmic process. For example. the abova-described parameters can be weighted to indicate the relative abnormality of the heart condition. ~hese weighted values may be summed and the total compared to a cut-point for an indication of a normal or 20 an abnormal condition. Again, Ruch an e~aluation may be per$ormed manually or by the computer based on the data obtained during the exercise routine.
Heart rate can be substituted for time in the above anal-yses. All of the parameters except parameter 2 are de~ined as 25 above. For use with the plot involving heart rate, parameter 2 ie defined as the constant c when the ~unctlon S(r) = Ke~~r ~Z~3~
is ~it to the RK slope versus heart rate data points, where S(r) is the slope, r is the ra~e, and K i5 another constant.
The invantion having been described in detail in accordance with requirements of the patent statutes, various other changes and modifications will suggest themselves to those skilled in the art. Since the slope of RK interval as a function of cuff pre~sure i9 a function of systolic slope, it may be converted to systolic slope which may be plotted aæ a function of time, heartbeat rate, or the like. Another obvious change includes the use of a manually inflatable cuff rather than the illustrated arrangement wherein cuff inflation and deflation are under control of the computer.
Also, as mentioned above and described in the above mentioned Weaver et al article, systolic and diastolic blood prassure meas-urements may be obtained from cuff pressure measurements made when true Korotkov sounds are first heard during a cuff deflation, and are last heard, and these pressures also may be displayed and/or recorded. A~ noted above, the operation of the present apparatu~
does not depend upon determination o~ systolic and diastolic blood pressures.
Also, it will be apparent that inputs may be supplied to the computer from the exercise davics, or the like, u6ed by the subject whereby thc work performed by the subject throughout the exercise cycle may be recorded.
,, .
~2233~
Also, it wi~l be apparent that means other than interrupt inputa may be used to input the time of occurance of the R-peak wave and Korotkov sound to the computer. Either a general purpose or dedioated computer may be employed. Also, a recording of the 5 necessary inputs may be made, and the recording played back to provide the computer inputs. Additionally, it will be apparent that other blood pressure transducers and systems may be used from which a measure of the systolic slope may be obtained, includ-ing, for example, invasive devices. It is intended that the above 10 and other such changes and modifications shall fall within the apirit and scope o$ the invention defined in the appended claims.
Claims (19)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. Apparatus for use in the diagnosis and/or screening of subjects for coronary heart disease comprising:
an inflatable cuff adapted to encircle a subject's arm;
means for inflating and deflating said cuff without a range of pressures within which Korotkov sounds are produced;
pressure transducer means responsive to cuff pressure and having an output signal related thereto;
electrode means for sensing electrocardiographic signals from the subject;
R-wave peak detector means for detecting the peak of the R-wave in the electrocardiographic signals;
transducer means for sensing Korotkov sounds during a cuff deflation;
Korotkov sound detecting means for detecting Korotkov sounds in the output from said Korotkov sound transducer means;
means responsive to the outputs from said pressure transducer, R-wave peak detector, and Korotkov sound detector means for producing a signal representative of the systolic slope of blood pressure waves during a cuff deflation;
means for recurrently obtaining said signals representative of systolic slope during different periods of an exercise cycle performed by the subject from which changes in slope during said exercise cycle are used in diagnosing and/or screening subjects having coronary artery disease.
an inflatable cuff adapted to encircle a subject's arm;
means for inflating and deflating said cuff without a range of pressures within which Korotkov sounds are produced;
pressure transducer means responsive to cuff pressure and having an output signal related thereto;
electrode means for sensing electrocardiographic signals from the subject;
R-wave peak detector means for detecting the peak of the R-wave in the electrocardiographic signals;
transducer means for sensing Korotkov sounds during a cuff deflation;
Korotkov sound detecting means for detecting Korotkov sounds in the output from said Korotkov sound transducer means;
means responsive to the outputs from said pressure transducer, R-wave peak detector, and Korotkov sound detector means for producing a signal representative of the systolic slope of blood pressure waves during a cuff deflation;
means for recurrently obtaining said signals representative of systolic slope during different periods of an exercise cycle performed by the subject from which changes in slope during said exercise cycle are used in diagnosing and/or screening subjects having coronary artery disease.
2. Apparatus as defined in Claim 1 including means for displaying said signals representative of systolic slope.
3. Apparatus as defined in Claim 2 wherein the display provided by said display means includes a plot of said signals representative of systolic slope versus heart rate of the subject.
4. Apparatus for use in the diagnosis and/or screening of subjects for coronary artery disease comprising:
an inflatable cuff adapted to encircle a subject's arm;
means for inflating and deflating said cuff within a range of pressures within which Korotkov sounds are produced;
pressure transducer means responsive to cuff pressure and having an output signal related thereto;
electrode means for sensing electrocardiographic signals from the subject;
R-wave peak detector means for detecting the peak of the R-wave in the electrocardiographic signals;
transducer means for sensing Korotkov sounds during a cuff deflation;
Korotkov sound detecting means for detecting Korotkov sounds in the output from said Korotkov sound transducer means;
means responsive to the outputs from said pressure transducer, R-wave peak detector, and Korotkov sound detector means for producing a signal representative of the systolic slope of blood pressure waves during a cuff deflation;
means for recurrently obtaining said signals representative of systolic slope during different periods of an exercise cycle that includes aerobic exercise performed by the subject;
means for evaluating changes in slope occurring during said exercise cycle for diagnosing and/or screening subjects having coronary artery disease.
an inflatable cuff adapted to encircle a subject's arm;
means for inflating and deflating said cuff within a range of pressures within which Korotkov sounds are produced;
pressure transducer means responsive to cuff pressure and having an output signal related thereto;
electrode means for sensing electrocardiographic signals from the subject;
R-wave peak detector means for detecting the peak of the R-wave in the electrocardiographic signals;
transducer means for sensing Korotkov sounds during a cuff deflation;
Korotkov sound detecting means for detecting Korotkov sounds in the output from said Korotkov sound transducer means;
means responsive to the outputs from said pressure transducer, R-wave peak detector, and Korotkov sound detector means for producing a signal representative of the systolic slope of blood pressure waves during a cuff deflation;
means for recurrently obtaining said signals representative of systolic slope during different periods of an exercise cycle that includes aerobic exercise performed by the subject;
means for evaluating changes in slope occurring during said exercise cycle for diagnosing and/or screening subjects having coronary artery disease.
5. Apparatus as defined in Claim 1 wherein said means for producing a signal representative of the systolic slope of blood pressure waves includes:
means for accumulating a plurality of cuff pressure values and associated RK intervals comprising the time between the occurrence of an output from said R-wave peak detector means and the associated Korotkov sound signal from said Korotkov sound detecting means; and means for fitting a straight line to said RK intervals and associated cuff pressure values obtained during a cuff deflation, the slope of which straight line is inversely proportional to the systolic slope of the blood pressure wave.
means for accumulating a plurality of cuff pressure values and associated RK intervals comprising the time between the occurrence of an output from said R-wave peak detector means and the associated Korotkov sound signal from said Korotkov sound detecting means; and means for fitting a straight line to said RK intervals and associated cuff pressure values obtained during a cuff deflation, the slope of which straight line is inversely proportional to the systolic slope of the blood pressure wave.
6. Apparatus as defined in Claim 5 including display means for displaying a plot of the slope of said straight line versus heart rate.
7. Apparatus as defined in Claim 4 wherein a systolic slope which increases then decreases during aerobic exercise is evaluated by said evaluating means as being indicative of coronary artery disease in the subject.
8. Apparatus as defined in Claim 4 wherein a systolic slope after aerobic exercise which is less than the pre-exercise systolic slope is evaluated by said evaluating means as being indicative of coronary artery disease in the subject.
9. Apparatus as defined in Claim 4 wherein a rate of change of systolic slope approximately two minutes after aerobic exercise is terminated which is greater than that for individuals without coronary artery disease is evaluated by said evaluating means as being indicative of coronary artery disease in the subject.
10. Apparatus as defined in Claim 4 wherein a rate of change of systolic slope during a period of time immediately following the start of aerobic exercise that is less than that for individuals without coronary artery disease is evaluated by said evaluating means as being indicative of coronary artery disease.
11. Apparatus as defined in Claim 4 wherein a systolic slope during the initial portion of the aerobic exercise segment of the exercise cycle is less than that for individuals without coronary artery disease is evaluated by said evaluating means as being indicative of coronary artery disease in the subject.
12. Apparatus as defined in Claim 4 wherein a systolic slope after aerobic exercise which is less than that for individuals without coronary artery disease is evaluated by said evaluating means as being indicative of coronary artery disease.
13. Apparatus for use in the diagnosis and/or screening of subjects for coronary artery disease comprising:
means for obtaining measurements of the systolic slope of an arterial blood pressure wave of the subject during different periods of an exercise cycle which includes pre-exercise rest, aerobic exercise on a treadmill, stationary bicycle, or the like, and post-exercise rest portions;
means for evaluating changes in slope occurring during said exercise cycle for diagnosing and/or screening subjects having coronary artery disease.
means for obtaining measurements of the systolic slope of an arterial blood pressure wave of the subject during different periods of an exercise cycle which includes pre-exercise rest, aerobic exercise on a treadmill, stationary bicycle, or the like, and post-exercise rest portions;
means for evaluating changes in slope occurring during said exercise cycle for diagnosing and/or screening subjects having coronary artery disease.
14. Apparatus as defined in Claim 13 wherein a systolic slope which increases then decreases during aerobic exercise is evaluated by said evaluating means as being indicative of coronary artery disease in the subject.
15. Apparatus as defined in Claim 13 wherein a systolic slope after aerobic exercise which is less than the pre-exercise systolic slope is evaluated by said evaluating means as being indicative of coronary artery disease in the subject.
16. Apparatus as defined in Claim 13 wherein a rate of change of systolic slope approximately two minutes after aerobic exercise is terminated which is greater than that for individuals without coronary artery disease is evaluated by said evaluating means as being indicative of coronary artery disease in the subject.
17. Apparatus as defined in Claim 13 wherein a rate of change of systolic slope during a period of time immediately following the start of aerobic exercise that is less than that for individuals without coronary artery disease is evaluated by said evaluating means as being indicative of coronary artery disease.
18. Apparatus as defined in Claim 13 wherein a systolic slope during the initial portion of the aerobic exercise segment of the exercise cycle is less than that for individuals without coronary artery disease is evaluated by said evaluating means as being indicative of coronary artery disease in the subject.
19. Apparatus as defined in Claim 13 wherein a systolic slope after aerobic exercise which is less than that for individuals without coronary artery disease is evaluated by said evaluating means as being indicative of coronary artery disease.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000431615A CA1223306A (en) | 1983-06-30 | 1983-06-30 | Method and apparatus for diagnosis of coronary artery disease |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000431615A CA1223306A (en) | 1983-06-30 | 1983-06-30 | Method and apparatus for diagnosis of coronary artery disease |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1223306A true CA1223306A (en) | 1987-06-23 |
Family
ID=4125595
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000431615A Expired CA1223306A (en) | 1983-06-30 | 1983-06-30 | Method and apparatus for diagnosis of coronary artery disease |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1223306A (en) |
-
1983
- 1983-06-30 CA CA000431615A patent/CA1223306A/en not_active Expired
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| US5211177A (en) | Vascular impedance measurement instrument | |
| US5241966A (en) | Method and apparatus for measuring cardiac output | |
| US9204857B2 (en) | System and method for monitoring hemodynamic state | |
| KR100609927B1 (en) | - Apparatus for Non-Invasive Cuffless Continuous Blood Pressure Determination | |
| US5054493A (en) | Method for diagnosing, monitoring and treating hypertension | |
| US4899758A (en) | Method and apparatus for monitoring and diagnosing hypertension and congestive heart failure | |
| CN101765398B (en) | Assessment of preload dependence and fluid responsiveness | |
| US20010016690A1 (en) | Method for diagnosing, monitoring and treating hypertension and other cardiac problems | |
| CN109730663B (en) | Blood pressure evaluation method based on pulse wave conduction velocity nonlinear analysis | |
| US4649929A (en) | Method and apparatus for diagnosis of coronary artery disease | |
| US20060224070A1 (en) | System and method for non-invasive cardiovascular assessment from supra-systolic signals obtained with a wideband external pulse transducer in a blood pressure cuff | |
| US10004473B2 (en) | Heart rate detection method and device using heart sound acquired from auscultation positions | |
| US4819654A (en) | Method and apparatus for diagnosis of coronary artery disease | |
| WO1992006633A1 (en) | Method and apparatus for measuring cardiac output | |
| EP1646313A1 (en) | Method and system for evaluating cardiac ischemia based on heart rate fluctuations | |
| WO1985000279A1 (en) | Method and apparatus for diagnosis of coronary artery disease | |
| CA1223306A (en) | Method and apparatus for diagnosis of coronary artery disease | |
| Freithaler et al. | Smartphone-Based Blood Pressure Monitoring via the Oscillometric Finger Pressing Method: Analysis of Oscillation Width Variations Can Improve Diastolic Pressure Computation | |
| Jobbágy et al. | Blood pressure measurement at home | |
| EP0150176A1 (en) | Blood pressure measurement with korotkov sound artifact information detection and rejection. | |
| Fan et al. | Clinical analysis for cardiovascular disease by calculating stiffness index, cardiac output from pulse wave | |
| Jobbágy et al. | Accurate blood pressure measurement at home | |
| Wang et al. | The Effects of Filtering PPG Signal on Pulse Arrival Time-Systolic Blood Pressure Correlation | |
| CN115316968A (en) | Systolic pressure measuring device and method based on real-time pulse wave signals | |
| Botzer et al. | Dynamic QT-RR relationships in 12 lead ecg in patients with coronary artery disease |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |