IL33744A

IL33744A - Bifocal demand pacemaker a water-soluble composition comprising sufadimidine and pyrimethamine

Info

Publication number: IL33744A
Application number: IL33744A
Authority: IL
Original assignee: Abic Ltd; American Optical Corp
Priority date: 1969-03-26
Filing date: 1970-01-20
Publication date: 1973-03-30
Also published as: AT302522B; DE2010724B2; NO126899B; DE2010724C3; NL7003205A; US3595242A; NL155453B; BE747983A; DK130771B; BR7017673D0; DK130771C; JPS4940992B1; IL33744A0; FR2040175A5; GB1307912A; SE356903B; CH534524A; ES377899A1; DE2010724A1

Description

■»τρ ia-π Bifocal demand pacemaker AMERICAN OPTICAL CORPORATION C: -32030 the past to treat this disorder. | For such patients, however, it would' be better, to .provide atrial' 'stimulation to thus control both the atrial and ventricular rates,.: with the additional benefit of the natural atrio.-ventricular sequence. But such atrial stimulation woul,d leave the patient, unprotected from unpredictable . AV block. Thus, provision should also be made' for ventricular stimulation if it becomes necessary. ·. ,. ,.

Both types, of pacing could be accomplished with the use of two individual, pa emakers. But even if they are combined in a single, package many problems must be| overcome, especially if a demand-type operation is desired. One of the most obvious problems concerns- the timing sequence of the two types of pacing. ' ■ ■ . . ' ■ ' .f. ■ - ·. It is a general object of my invention to provide a : ! . I ' ·■ ■ ■' · bifocal pacemaker for atrial as well as ventricular stimulation, which preferably is of the demand; type, j In accordance with the principl !es of my invention the first function of the pacemaker is to generate an atrial' stimulat- ing impulse. After . a predetermined Ίtime interval, the. pacemaker j functions to generate 'a ventricular 'Stimulating- impulse. Three ! electrodes are provided -- a neutral electrode] an electrode for' atrial stimulation and an electrode for ventricular stimulation.

I In the illustrative embodiment of the invention, the ventricular I electrode also serves to detect the occurrence :of a ventricular j contraction. ' ■ .'' ■ '·'; ! ·■ '' ■ .

! The pacemaker exhibits two time-out or escape intervals.

( The ventricular escape interval is 160-250 milliseconds longer ; than the ' atrial escape interval. The ventricular escape, interval ■ ; is greater than the normal interval between two heartbeats (as in a conventional demand pacemaker) . ■ The atrial escape' interval is greater than;:the normal interval between atrial and. ventricular beats (P to R) , but less than the normal inter-beat interval (R to R) transistors, a positive pulse is to the base of transistor TSv Transistor T6 conducts and' capacitor 57 discharges through it. Thus, although the capacitor was previously . charging to the level whic would have, resulted in the generation, of an impulse, it is discharged and a new time-out interval begins. This arrangement insures that an impulse · is not generated if a . natural heartbeat has occurred. .The time-out interval is such that impulses are generated with ,an inter-pulse interval slightly' in excess of the desired natural inter-beat interval. Only if a natural heartbeat is missin is -.a stimula't'ing impulse generated.

The remaining transistors in th!e circuit serve to prevent conduction of transistor T6 in the presence of. noise. In the ' presence of noise .it would otherwise be possible for transistor T6. to conduct and prevent the generation lof an impulse even though one is required'. For this' reason, whe the pacemaker detects extraneous noise, transistor- T6 is prevented, from operating -and impulses- are delivered at & fixed rate. Ά more complete description of the operation of the circuit of FIG. 1 is set forth in my above- . '. ■''· ' . 1'j · . I ■ ■ identified . j! ' j The .illustrative embodiment of (the invention is derived by adding the circuit elements .and ..conductors shown in heavy lines in- FIG. 1, and combining the circuits of■ FIGS-, j 1 and 3, as shown in- FIG. 4. The circuit of FIG. 3 is in almost jail respects identical to the circuitry on the right side of FIG. 1. The various elements in the circuit, of FIG. 3 are designated by the same- numerals as the equivalent elements 'in FIG. 1" with the addition of prime symbols. Conductor 80 :c'ouples potentiometer 35' and resistor -59' to a terminal of battery 7 just as potentiometer and resistor- 5'9 are coupled' to' the same terminal in FIG. 1.

Conductor SI couples the base of transistor T7 to the other terminal of battery. 7 just as the base of transistor T7 in FIG. 1 is coupled to this terminal. Conductor 82 couples the base o \ transis-tor Τ·β·' to- the- right side of capacitor 53, just as the ' base of transistor T6 in FIG. 1 is. coupled to the right side of the-- capacito . Conductor S3:·, serves to provide a common neutral for the. circuits of FIGS. 1 and 3. 1 Finally, conductor 84 serves to extend a signal to disable FET switch 92, as will be described ■ I, ■ · ' . Ί 11 below. ■ '·..·". ' Electrode E3 in FIG. 3 is , implanted' in the patient's heart to stimulate his atria. The circuit of FIG. 3 functions ust as does the circuit on the right side of FIG. 1, except that · - i each stimula ing impulse results in an atrial contraction rather. than a ventricular contraction. Capacitor 57' charges through .. .. ■ '.. ■ . V . : :■·. . . j! ' . ^ . potentiometers 35' and 37'.· After a predetermined interval, when the capacitor' voltage has reached; the . level required to control conduction of transistors T7 ' and T8', the two transistors conduct and forward bias the base- emitter] junction of transistor ■ " - "· ·: . -'■); ■ - ' '| ■ ■ . · ■ T9' . The charge on capacitor 65' flows through transistor T9' and electrodes E2 and E3. The width of each pulse is determined ! by the setting of potentiometer 37' which; determines the time. ; required for capacitor 57' to discharge through transistors T7 ' i x I I j and T8'.. The inter-pulse interval is .determined by the .settin j of potentiometer 35' which., determines the, time jrequired for I capacitor 57' to charge to the level- which causes transistors i T7 '■ and T8' to conduct. ..; ί | Any pulse delivered through capacitor 53 as a result of I the detection of an R wave causes transistor T6' to conduct along j with transistor T6. At the same time that capacitor 57 discharges ' through transistor Τβ,. capacitor 56' discharges through transistor T6'. In such an event, the time-out period of the circuit of FIG. - 3 is not concluded and an atrial stimulating pulse is not generated. Instead, the time-out . begins once again.

·; The time-out intervals of 600 milliseconds and 800 •milliseconds /shown in FIG. 5 are not critical. Considerable flexibility is possible. Generally, the time-out interval for the circuit of. FIG.. 3' should be such that an impulse is generated at electrode. E3; some, time between the-. P- and R waves following- a. previous R wave. The time-out interval for the circuit of FIG. 1 should be such that an impulse is -generated at electrode El at a time after the last R wave which exceeds . the' desired period between natural heartbeats.,, . . ^ : ■' ' . ·' ; ■ It is thus seen that the pacemaker of the invention' ' · - . ■ I · . .· . · serves to correct for the condition known| as atrial bradycardia at the same time that it protects againstj ventricular asystole. Although the invention has been described! with reference to a particular, embodiment,, it..is to bje understood, that this embodimen is merely' illustrative of the application1 of the principles of th ■ ' ■ · ''' I ■ invention. Numerous modifications, may· beji made therein and other. arrangements may . be devised' without ! departing from the spirit and ■■ ■ '·! ' ■ ·■ " Γ ■ · ! scope of. the invention. 'j ] Ί .· ; natural heartbeat does not take 'place by the end of: time-ou period a s imulating impulse ' is, generated. For the proper opera-, tion of a demand pacemaker, the pacemaker circuitry must · ! determine if a natural heartbeat has occurred. The largest magnitude' electrical signal generated by the heart activity is . the QRS complex corresponding to,ventricular contraction. To determine whether a natural heartbeat has occurred, an electrode is generally coupled to a ventricle. Since in most cases ventricular stimulation, is required, the same electrode can be used for both stimulating the ventricles and detecting a natural heartbeat, as disclosed in my aforesaicL; patent.

In the presence of noisej, erroneous operation of , a demand pacemaker of this type can take place. The noiseimay result in the generation of an electrical signal on the ventri- : cular electrode, and the pacemaker circuitryj may treat, this noise as indicative of a natural heartbeat and inhibit the generation of a stimulating impulse even ; if One Is} required . In my Israel Patent No. 51473 >, '. I -1951 an improved demand pacemaker is disclosed. In this · . improved demand pacemaker, in the presence of noise the pacemake time-out period is not interrupted. Continuous stimulating impulses are generated, . even if they are not required. It is ; '{'. . ' '," ' . I.. ;· : , : ■ . . ' ·····' '■: better to provide an impulse even if it is not required than it is not to provide an impulse if' it is required.

There are many patients- with symptomatic atrial · bradycardia even though they have normal AV conduction... In such a patient, the slo .atrial rate causes the ventricular, rate to transistors, a positive pulse is delivered to the base of · ..'·.< transistor T6. · Transistor T6 conducts and capacitor 57 discharges through, it. Thus, although the capacitor was previously! : charging to the Level which would have. resul.ted in the' eneration. of an impulse, it¾'is discharged and. new time-out interval begins;. This arrangement insures that an impulse is not generated if a. natural heartbeat has occurred. The time-out interval is -such ■ that impulses are generated with an inter-pulse interval slightly' in excess of the desired natural inter-beat interval. Only if natural heartbeat is missing is a stimulating impulse generated. :.

The remaining transistors in the circuit serve to prevent conduction of transistor T.6 in the presence of noise. In the ' · presence of noise it would -otherwise be possible for transistor T6 to conduct and prevent the generation jof an impulse eve though one is required. For this : eason, when the pacemaker detects extraneous noise, transistor Ί$ is prevented, from operating and impulses are. delivered at a fixed rate. A more complete description of the operation of the circuit- of FIG. I1 is set forth in my above-- ■ 'Patent ■ ■ " !. ... · ' . ·; .' ' ■■·.' .': identified &ρρίάθΏ¾-»οι¾. . . ,: ■ . ,' ■ ■ . '. ■ " ·!· · ' i' . . . ··■ .·■ '.'·,,; :' ' ·!'■.'.·' The .illustrative embodiment of ithe invention is derived by adding the circuit elements and conductors shown in heavy lines in FIG. 1, and combining- th½ circuits of FIGS .j 1. and 3> as: shown > in FIG. 4. The circuit of lG. 3 is in almost1 all respects identical to the circuitry on the right side of FIG. 1.. The various elements in the circuit, of FIG. 3 are designated b the same numerals as the equivalent elements in FIG. 1 with the . addition of prime symbols. (Conductor 80 icouples potentiometer 35' . and res-istor 59' to a terminal,* of battery 7 just as potentiometer ' ,35 and resistor- 59 are coupled t the same terminal in FIG.. 1.

Conductor 81 couples the base, of transistor T7V, to the other terminal of battery 7 just as the base of; transistor T7 in FIG. 1 . • is coupled to this terminal. Conductor 82 couples the base ol transis-tor Τ6·' to- the right side of capacitor 53, just as . the base of transistor T6 in FIG. 1 is. coupled to the right side of the capacitor. Conductor 03- serves to provide a common neutral for the. circuits of FIGS. \ and 3. 'Finally, conductor 84 serves to extend. a signal to disable FET switch 92, as will be described ■ below. I- . ' '' ! ' Electrode E3 in FIG. 3 is implanted in the patient's heart to stimulate his atria. The circuit of FIG. 3 functions . ' ■ ' ' just as does the circuit on the' right side of FIG. 1, except that. > · ' · ί .' . .. .' ·' .each stimulating impulse results in an atrial contraction rather. than a ventricular contraction. Capacitor 571 ; charges through' potentiometers 35' and 37·. After a predetermined interval, when the capacitor voltage has reachedjthe level required to control conduction of transistors T7' and Τ8', the two transistors •conduct and forward bias the base- emitterj junction of transistor T9'. The charge on capacitor 65' flows through transistor T91 * and electrodes E2 and E3. The width of each pulse is determined' by the setting of potentiometer 37' whichj determines the time . required for capacitor 57' to discharge through transistors T7 · and- T81. Th inter-pulse interval is determined by the settin of potentiometer 35· which, determines the time required for I capacitor 57 * tc( charge to the level which causes transistors I T7 ' and TO' to conduct. '·','":'· '■':■.'■■!' ■'■[■ ' I. Any pulse delivered through. capacitor 53 as a result of j. the detection of. an R wave causes transistor T6' to conduct along i with transistor T6. At the. same time that capacitor 57' discharges ί through transistor T6, capacitor- 56.' discharges through transistor . T6'. In such an event, the time-out period of the, circuit of FIG. : 3 is not . concluded and an atrial stimulating pulse is not generated. Instead, the time-out . egins once again. contraction.

It should be noted that ' if the heart beats naturally, there will be no ventricular stimulation by the pacemaker; . Howeyer,. there will be atrial stimulation because the 600 millisecond time-. v. out interval of the circuit' of/ FIG. i3 is less than the natural inte pulse interval. But in the'.event a ;natural atrial contraction does . not take place, the atrial stimulation is required in order that the heart function more efficiently. : The ventricular stimulation, · of course," is provided to correct any AV block.- A normal ventricular contraction can occur approximately 120-160 milliseconds after the ' atrial stimulation.. The ventricular time-out period in the circuit . of FIG. 3 is 200 milliseconds longer than] the atrial time-out period in the circuit of FIG. 1; sufficient tune is· allowed for ' a natural ventricular contraction before a entricular stimulating impulse is generated. In general the.ventricular time- out, period should exceed • ··',· ♦ . ; t ..· · ··' J ; · · · the atrial time-out period by 160!- 250 milliseconds. ·.. · · ■ .. ■ . ■ ■ < ..!■■ , .·■ ! . . ! ■ . ·.· ■ · V It should also be .noted that the operation of the circuit- of FIG. '3 is keyed to the detectipn'of a ventricular contraction by .the circuit of FIG. 1. It is highly desirable to key the circuit of FIG. 3 to the beating- of .the patient1 s heart -- were a free- running generator provided to stimulate' the atria, the . timing of the beating of the patient's heart might be seriously .

:. . ■·' ' ' '. ' ' · ! ·' ' I ■'·'■■"'" ■' affected. While the natural . timing might change, the circuitry timing would be invariant. For this reason, capacitor 57'. is discharged following any beating of j the patient's heart. Theoretically,; it might be possible to detect an atrial contraction, ■that is, to detect, the P wave, and to discharge capacitor 57'. before its time-out is completed so that an atrial stimulating . impulse would not be generated if it is not required. However, it, : is exceedingly dif icult to detect the P wave due to its' small magnitude as compared to the . this reason, in the .

BIFOCAL DEMAND PACEMAKER This invention relates to pacemakers, and more particularly to demand pacemakers for use with patients exhibiting symptomatic atrial bradycardia and unpredictable AV block. · . ' ■.' ' ' . : , ■. '. '_ ·■ The electrical activity of a normal heart begins with a nerve impulse generated by a bundle of fibers located · in the sinoatrial node. T,he impulse spreads across the. two atria while they contract and speed the flow of blood^ into the1- entricles underneath .them. The atrial activity of the heart corresponds, to the P wave Ln an electrocardiogram trace.. The. electrical impulse continu≥s to spread across the atrioventricular (AV) node, which in turn stimulates the jleft and right ventricles,.. Typically, an interval of approximately 120-160 millisecpnds; '■-elapses between atrial and 'ventricular stimulation. ' The " ventricular activity corresponds to the QRS portion of the ·' electrocardiogram, and typically has a duration of 80 milliseconds ■ · ■ i : · . |:- ■! ·.· ·. '· ■ ■' - Toward the end of each heartbeat, . the ventricular muscles •repolarize, and this portion of the' electrical activity of the heart corresponds to the T wave in the electrocardiogram.

Of the two types of ; contractions, the ventricula . is far 'more important than the atrial. The atrial contractions . cause the ventricular contractions to bej more efficient; the ventricular contractions are more effective! if the ventricles are fir filled with blood. While a patient' can survive without proper . atrial action, he cannot sur i e, without1 ventricular contractions. the past to treat t is sor er, For suc pat ents, oweverjit. ' would be better, to .provide atrial 'Stimulation to thus control, bot the atrial and ventricular rates, with the additional benef t or th natural atrio-ventricular sequence. But such atrial stimulation would leave the patient,, unprotected from unpredictable- AV block'. Thus, provision should also be made 'for ventricular stimulation if, it becomes necessary.

. Both types of pacing could be accomplished with 'the, ■ ' use of two individual, pacemaker's.- But even if they are combined ; in a single. package many problems must bej overcome, .especially . if a demand-type operation is desired..' One of the most obvious ·; problems concerns the timing sequence of the two types of pacing..

It is a general object of my invention to provide a bifocal pacemaker for atrial as well as ventricular stimulation, which preferably is of the demand type. \ In accordance wit the principljes of imy invention the first function of. the pacemaker is tio generate jan atrial stimulating impulse.' After a, redetermined itime interval, the pacemaker- functions to generate a ventricular stimulating' impulse. Three electrodes are provided -- a neutral electrode, an electrode for." atrial stimulation and an electrode for ventricular , stimulation.

In the illustrative embodiment of the invention, the ventricular -electrode also serves to detect the occurrence jof a ventricular contraction/ 1 · , · ;.

The pacemaker exhibits two time-out or escape intervals.

The ventricular escape interva is l!60-250 milliseconds longer than th 'e!a·t■-ri.al escape..inte.rval; 'Thre. vent.ricular escap,e,-i■rf!t■er■val is greater than the normal interval betvreen two heartbeats (as, in a conventional demand pacemaker). The atrial escape interval · is greater than: the normal interval betvreen atrial and ventricular beats (P to R) ,· but less than the normal inter-beat interval (R to R) 1 - transistors, a positive pulse is delivered to the base of. · : .'·' transistor TS.. Transistor Ύ6 conducts and capacitor 57 dis- '.'· charges through it. Thus, £.1though the capacitor was previously, charging to the Level which-j ould have, resul.ted in the generation.,, of an impulse, it "is discharged and a new time-out interval begins:. This arrangement insures that an impulse is not generated if a \· natural heartbeat has occurred. The time-out interval is -such that impulses are generated with 'an inter-pulse interval slightly' in excess of the desired natural inter-beat interval. Only if a .'-..· natural heartbeat is missing iS a stimulating impulse generated.

The remaining transistors in the circuit serve to prevent conduction of transistor T6 in the presence of noise. In the ' · presence of noise it would otherwise be possible for transistor T6 to conduct and prevent the generation !of an impulse even though one is required. For this reason, when the pacemaker .detects extraneous noise, transistor T6 is prevented, from operating and impulses are- delivered at a fixed rate. J'A more complete description of the operation of the circuit of FIG. I1 is set. forth in my above- Patent ' ;.. · . j; i . identified The illustrative embodiment of Ithe invention is derived . ■ i; 1 by adding the circuit elements and conductors shown in heavy lines in FIG. 1. and combining the circuits of FIGS.;1 and 3, as shown ■ ■· ·· ■ · . ' ' ί . J ; ■ in FIG. 4. The circuit of FIG. 3 is in almost'all respectsj identical to the circuitry on the right side of FIG. 1. The various elements in the circuit, of FIG. 3 are designated by the same numerals as the equivalent elements in FIG. 1 with the addition of prime symbols. Conductor 80 couples potentiometer 35' and resistor 59' 'to a terminal of battery 7 just as potentiometer 35 and resistor 59 are coupled to the same terminal in FIG. 1.

Conductor 81 couples the base ..of transistor T7 '. to the other terminal of batter 7 just as the base of transistor T7 in. FIG. ' 1 is coupled to this terminal. Conductor 82 couples the base oJ . transistor Τ6·' to- the righ s de of capacitor 53, just as the. · base of transistor T6 in FIG.11 is. coupled to the right side of th© capacitor. Conductor 03- ierves to provide a common neutral , for the. circuits of FIGS. I ajjid 3.. Finally, conductor 84 serves '. to extend a signal to disable FET switch 92. as will be described \ ■ \ below.

Electrode E3 in FIGJ' 3 is implanted in the patient's heart to stimulate his atria, j The circuit of FIG. 3 functions just as does the circuit on ,the: right side of FIG. 1, except that each -stimulating impulse results in' an atrial contraction rather than a ventricular contraction. Capacitor 57' charges throu-gh . potentiometers 35' and 37'. After a predetermined interval, when the capacitor voltage has reachedj the level required to control conduction of transistors T7 ' and-T8', the two transistors . ; j · ' · . ■ ; ' · ■ |. · - I ■ conduct and forward bias the base-emitter! junction of transistor T9". The charge on capacitor 65' j flows through transistor T9' ? and electrodes E2 and E3. The'width of each pulse is determined by the setting of potentiometer 37' whichj|deteimines the time required for capacitor 57' to discharge through transistors T7 ' and T8'. The inter-pulse .interval j is determined by the setting of potentiometer 35· which. determines the. time jrequired for capacitor 57' t1 charge to the level which causes transistors T7' and TO' to conduct. · , ' ; : ■ ' ! ■·· - .* .' i . · Any pulse delivered through capacitor 53 as a result ;o · .·. '. . · . - ! · ' , - · ■. ' ■■ j .. the detection of. an R wave causes transistor Τβ' to conduct al n with transistor T6. At the same time that capacitor 57 discharges through transistor T6, capacitor 56' discharges through transistor T6'„ In such an event, the time-out period of the circuit of FIG. 3 is riot . concluded and an atrial stimulating pulse is not ,: ,.' enerated.. Instead the time-out . be ins once a ain. contraction. ·; ^ ■ > ;'. ' I It should be noted that if the heart beats naturally, ] · there will be no ventricular stimulation by the pacemaker. However, ' j 'there will be atrial stimulation because the 600 millisecond time- 1 . out interval of the circuit of" FIG. - 3 is less than the natural inter- - i pulse interval . But in the event a _ natural atrial contraction does . ! not; take place, the atrial stimulation is required in order that the - ; heart function more efficiently. ; The ventricular stimulation, - of . course, is provided to correct any AV block. A normal ventricular contraction can occur approximately 120-160 milliseconds after the · atrial . stimulation.. The ventricular time-out period in the circuit : : of FIG . 3 is 200 milliseconds longer than! the atrial time-out period . in the circuit of FIG. 1 ; sufficient timej is- allowed for a natural . ventricular contraction" before a ventricular stimulating impulse is generated . In general, the; ventricular time-out period should exce< the atrial time- but period by 160!-250 milliseconds .

It should also be noted, that the . operation of the circuit- of FIG. '3 is keyed to the detection of , a ventricular contraction by . the circuit of FIG. 1.' It is highly des irable to key the .,! :, ;, circuit of FIG. 3 to the beating- of. ;the; p tient' s heart - - were i '■I a free- running generator provided to stimulate' the atria, the timing of the beating of the patient ' s heart might be seriously- , affected . While the natural timing^ might change, the circuitry · , . ; timing would be invariant . For this reason, capacitor 57 ' is discharged following any beating .of J the patient' s heart . Theore- · tically, it might be possible to detect an atrial contraction, that is , to detect the P wave, and to discharge capacitor 57 ' before its time-out is completed so that an atrial st imulating / ·.' " <■■ impulse would not be generated if it is not required . However, it , is exceedingly difficult to detect the P.,' wave due to its. small ' " magnitude as compared to the R wave . - For this reason, in the . 33744/2 ·

Claims

1. A pacer comprising terminal means for connection to a patient's heart for atrial stimulation, terminal means for connection to said patient's heart for ventricular stimulation, means for detecting the beating of said patient's heart, means for generating an electrical stimulus on said atrial terminal means following a first predetermined time interval after the detection of the last beating of said patient's heart, and means for generating an electrical stimulus on said ventricular terminal means following a second predetermined time interval after the detection of the last beating of said patient's heart.

2. A pacer in accordance with claim 1 wherein said second predetermined time interval is longor than said first predetermined time interval.

3. A pacer in accordance with claim 2 wherein said first predetermined time Interval is shorter than the normal interval between successive R-waves in the electrocardiographic waveform of said patient and is longer than tiie normal interval between an R-wave and the next -wave In the electrocardiographic waveform of said patient.

4. A pacer in accordance with claim 3 wherein said second predetermined time interval is longer than the normal interval between successive R-wages in the electrocardiographic waveform of said patient.

5. A pacer in accordance with claim 4 wherein said second predetermined time interval is longer than said

6. A pacer in accordance with claim 4 wherein said atrial and ventricular terminal means together include only three electrodes†

7· A pacer in accordance with claim 2 wherein said second predetermined time interval is longer thanthe normal interval between successive R-waves in the electrocardiographic waveform of said patient, and further including means for disabling the operation of said detecting means during the generation of an electrical stimulus on said atrial terminal means*

8· A pacer in accordance with claim 7 further including means for controlling said atrial and ventricular generating means to generate said respective electrical stimuli independent of the operation of said detecting means in the presence of noise which would otherwise be confused with the beating of said patient's heart.

9. A pacer in accordance with claim 7 wherein said second predetermined time interval is longer than said first predetermined time interval by 160-250 milliseconds.

10. A pacer in accordance with claim 4 wherein said detecting means is connected to said ventricular terminal means, and further including means for disabling the operation of said detecting means durin the generation of an electrical stimulus on said atrial terminal means.

11. A pacer in accordance with claim 2 wherein said detecting means is connected to said ventricular terminal means·

12. A pacer in accordance with claim 11 wherein said atrial and ventricular terminal means together Include

13· A pacer in accordance with claim 2 further including means for controlling said atrial and ventricular generating means to generate said respective electrical stimuli independent of the operation of said detecting means in the presence of noise which would otherwise be confused with the beating of said patient's heart*

14. A pacer comprising terminal means for connection to a patient's heart for atrial stimulation, terminal means for connection to said patient's heart for ventricular stimulation, a first timing circuit Including first means for generating an electrical impulse on said atrial terminal means, a second timing circuit includin second means for generating an electrical Impulse on said ventricular terminal means, means for detecting a beating action of said patient·s heart, and means responsive to the operation of said detecting means for resettin said fitfst and said second timing circuits.

15· A pacer in accordance with claim 14 wherein said detecting means is operative to detect a Ventricular contraction of said patient's heart,

16. A pacer in accordance with claim 14 wherein the period of said first timing circuit is shorter than the normal interval between two successive R-waves in the electrocardiographic waveform of said patient.

17. A pacer in accordance with claim 16 wherein the period of said first timing circuit is longer than the normal interval between an R-wave and the next P-wave in the electrocardiographic waveform of said patient.

18. A pacer in accordance with claim 17 wherein the "

19. A pacer in accordance with claim 16 wherein the period of said second timing circuit is longer than the normal interval between successive R-waves in the electrocardiographic waveform of said patient.

20, A pacer in accordance with claim 14 wherein the period of said second timing circuit is longer than the normal interval between successive R-waves in the electrocardiographic waveform of said patient,

21, A pacer in accordance with claim 18 further including means for preventing the resetting of said first and second timing circuits responsive to the operation of said detecting means in the presence of noise which would otherwise be confused with a beating action of said patient's heart,

22. A pacer in accordance with claim 14 further includin means for preventin the resetting of said second timing circuit responsive to the operation of said detecting means in the presence of noise which would otherwise be confused with a beating action of said patient ^s heart,,

∑ .,.. A pacer in accordance with claim 21 wherein said atrial and ventricular terminal means together include only three electrodes,

24, A pacer in accordance with claim 14 wherein said atrial and ventricular terminal means together include only three electrodes,

25, A pacer in accordance with claim 18 wherein the period of second timing circuit exceeds the period of said first timing circuit by 160-250 milliseconds.. ·.*-·' to a patient*s heart for atrial stimulation, terminal means for connection to said patient's heart for ventricular stimulation, means for detecting a beating action of said patient's heart, means for applying an electrical impulse to said atrial terminal means following a first predetermined time interval after the detection of the last beating action of said patient's heart, and means for applying an electrical impulse to said ventricular terminal means following a second predetermined time interval after the application of said electrical impulse to said atrial terminal means only in the absence of the detection of a beating action of said patient's heart following the generation of said electrical impulse on said atrial terminal means during said second predetermined time interval,,, 27. A pacer in accordance with claim 26 wherein said detecting means is operative to detect a ventricular contraction of said patient's heart, and further including means for disabling the operation of said detecting means during the application of an electrical impulse to said atrial terminal means. 28. A pacer in accordance with claim 27 wherein said first predetermined time interval is longer than the normal interval between an R-wave and the next P-wave in the electrocardiographic waveform of said patient. 29. A pacer in accordance with claim 28 wherein said first and second predetermined time intervals are within respective ranges such that with the proper beating of said patient's heart an R-wave in said electrocardio* 30. A pacer In accordance with claim 26 wherein said first predetermined time interval is shorter than the normal interval between successive R-waves in the electrocardiographic waveform of said patient and said second predetermined time interval is longer than said normal interval, 31 A- acer in accordance with claim 30 wherein said first predetermined time interval is longer than the normal interval between an R^-wave and the next P-wave ■■.'·. in the electrocardiographic waveform of said patient* 32. A pacer comprising terminal means for connection to a patient's heart for atrial and ventricular stimulation, means for detecting the beating of said patient's heart, means controlled by the operation of said detecting means for generating electrical stimuli in a predetermined timing sequence on said terminal means for stimulating said atrium and said ventricle, 33. A pacer as recited in claim 32 , and wherei said detecting means includes means for preventing erroneous detection of an atrial contraction as an apparent ventricular contraction, IS/rub 33744/2 - 13· A pacer in accordance with claim 2 further including means for controlling said atrial and ventricular generating means to generate said respective electrical stimuli independent of the operation of said detecting means in the presence of noise which would otherwise be j confused with the beating of said patient* s heart* 14. A pacer comprising terminal means for connection to a patient's heart for atrial stimulation, terminal means for connection to said patient's heart for ventricular stimulation, a first timing circuit including first means for generating an electrical impulse on said atrial terminal means, a second timing circuit including second means for generating an electrical impulse on said ventricular terminal means* means for detecting a beatin aotlon of said patient's heart, and means responsive; to the operation of eaid deteoting means for resetting said fi*at and eaid second timing circuits, 15. A pacer in accordance with claim 14 wherein said detecting means is operative to detect a ventricula contraction of said patient's heart. 16. .. A pacer in accordance with claim 14 wherein the period of said first timing circuit is shorter than the normal interval between wo successive R-wavee in the electrocardiographic waveform of said patient*. 17* A paoer in accordance with claim 16 wherein the . period of said first timing circuit is longer than the normal interval between an R-wave and the next P-wave in the electrocardiographic waveform of said patient* 18* A paoer in accordance with claim 17 wherein the

26· A aoe com riein terminal means for oonneotion 33744/2 to a patient's heart or atrial stimulation, terminal means for connection to said patient's heart for ventri- oular stimulation! means for detecting a beating action of said patient*s heart, means for applying an electrica impulse to said atrial terminal means following a first predetermined time interval after the deteotion of the last heating action of eaid patient's heart* and means for applying an electrical impulse to said ventricula terminal means following a second predetermined time interval after the application of said electrical impulse to said atrial terminal means only,in the absence of the detection of a beating action of said patient*s heart . following the generation of eaid eleotrical impulse on said atrial terminal means during said second predetermined time interval,

27. A pacer in accordance with claim 26 wherein said detecting means is operative to deteot a ventricular contraction of said patient's heart, and further includin means for disabling the operation of said detecting means during the application of an electrical impulse to said atrial terminal means* 26· A pacer ia accordance with claim 27 wherein eaid first predetermined time interval is longer than the normal interval between an R-wave and the next P-wave in the electrocardiographic waveform of said patient* 29· A pacer in accordance with claim 28 wherein said first and second predetermined time intervals are withi respective ranges Such that with the proper beating of said patient's heart an R-vave in eaid electrocardio 33744/k ■ & CLAIMS 1. A pacer comprising terminal means for connection to a patient's heart for atrial stimulation, , terminal means for connection to said patient's heart for ventricular stimulation, means for detecting the heating o said patient's heart, means for generating an electrical stimulus on said atrial terminal means following a first predetermined time interval: fter the detection of the last beating of1 said patient's heart, and means for generating an electrical stimulus on said ventricular terminal means following a second predetermined time interval after the detection of the last beating of said patient's heart, 2. A pacer in accordance with claim 1 wherein said' second predetermined time interval is longer than said first predetermined time interval. 3· A pacer in accordance with claim 2 wherein said first predetermined time interval is shorter than the normal interval between successive R-waves in the electrocardiographic waveform of said patient and is longer than t:ie. normal interval between an R-wave and the next P-wave in the electrocardiographic waveform of said patient. 4. A pacer in accordance with claim 3 wherein said second predetermined time interval- is longer than the normal interval between successive R-wages in the electro-cardiographicpwaveform of said patient. 5. A pacer in accordance with claim 4 wherein said second predetermined time interval is longer than said first redetermined time interval b 160-2 0 milliseconds. ," " · ' ■ ■■'. 33744/ 6* A pacer in accordance with claim 4 wherein said atrial and ventricular terminal means together inolude only three electrodes· 7· A pacer in accordance with claim 2 wherein said eeoond predetermined time interval is longer thanthe normal interval between* successive R-waves in the electrocardiographic waveform of said patient, and further including means for disabling the operation of said detecting means during the generation of an eleotrloal stimulus on said atrial terminal means. 8. A pacer in acoordanoe with olaim 7 further including means for controlling said atrial and ventrloular generating means to generate said respective electrical stimuli independent of the operation of said detecting means in the presence of noise which would otherwise be oonfuoed with the beating of said patient's heart* 9. A pacer in acoordanoe with claim 7 wherein said second predetermined time interval is longer than said first predetermined time interval by 160-250 milliseconds, 10· A paoer in accordance with olaim 4 wherein said detecting means is bonnected to said ventricular terminal means, and further including means for disabling the operation of said detecting means during the generation of an electrical stimulus on said atrial terminal means* 11. A pacer in accordance with olaim 2 wherein said detecting means is oonneoted to said ventricular terminal means* j · 12* ' A paoer in accordance with claim 11 wherein said atrial and ventrloular terminal means together inolude ■■■ .- ." --..ν:·' 33744/2' ■ ; · / :; 1 ■ , ; :/■ ■ ν'·': -: 13· A pacer in accordance with claim 2 further in-; eluding means or controlling said atrial and ventricular ' generating means to generate said respective eleotrioal ' stimuli independent of the operation of said detectin ..· ;■: means in the presence of noise which would otherwise be confused with the beating of said patient's heart* 14· A pacer comprising terminal means for connection to a patient's heart for atrial stimulation, terminal means for eonneotion to said patient's hear for ventricular stimulation, a first timing circuit including first means - for generating an eleotrioal impulse on said atrial terminal means* a second timing circuit including second i means for generating an eleotrioal impulse on said ventricular terminal means, means fo deteoting a beating j aotion of said patient's hear , and means responsive · to the operation of said detecting means fo resettin said first and said second timing circuits* : ' 15* A paoer^in accordance with olalm 14 wherein said detecting means Is operative to deteot a ventricular 'contraction of said patient's heart* ; ¾ 16· i i A paoer in accordance with claim 14 wherein the ·:.. period of said first timing circuit is shorter than the normal Interval between two successive R-waves in the ' electrocardiographic waveform of said patient* 17· A paoer in accordance with claim 16 wherein the period of said first timing oirouit is longer than the [■ normal interval between an R-wave and the next P-wave in the electrocardiographic waveform 6f said patient* 18* A .paoer in accordance with claim 17 wherein the 33744/2 to a patient's heart for atrial stimulation, terminal means for connection to aaid patient's heart for ventri- oular stimulation, means for detecting a beating ac ion of said patient's heart, means for applying an electrical impulse to said atrial terminal means following a first predetermined time interval after the detection of the last beating action of said patient's heart, and means for applying an electrical impulse to eaid^ ventricular terminal means following a second predetermined time interval after the application of said eleotrical impulse to said atrial terminal means only,in the absence of the detection of a beating action of said patient'B heart following the generation of said eleotrical impulse on said atrial terminal means during said second prede tennined time interval,, 27* A pacer i 'accordance with claim 26 wherein said detecting means is operative to detect a ventricular contraction of said patient's heart, and further including means for disabling the operation of said detecting means during the. application of an electrical impulse to said atrial terminal means.

28. A pacer in accordance with claim 27 wherein said first predetermined time interval is longer than the normal interval between an R-wave and the next P-wave in the eleotroeardiographio waveform of said patient* 29· A pacer in accordance with claim 28 wherein said first and second predetermined time intervals are withi respective ranges such that with the proper beating of said patient's heart an R-wave in said electrocardio-