US2659363A

US2659363A - Electrocardiovectographic device

Info

Publication number: US2659363A
Application number: US108119A
Authority: US
Inventors: Brosselin Michel
Original assignee: USINES GALLUS SOC
Current assignee: DITE USINES GALLUS Ste; USINES GALLUS SOC
Priority date: 1948-08-03
Filing date: 1949-08-02
Publication date: 1953-11-17
Anticipated expiration: 1970-11-17

Description

Nov. 17, 1953 M.'BROSSEL|N ELECTROCARDIOVECTOGRAPHIC DEVICE Filed Aug. 2, 1949 Patented Nov. 17, 1953 ELEGTROCARDIOVECTOGRAPHIC DEVICE Michel Brosselin, Courbevoie, France, assignor to Socit dite: Usines Gallus (Societe Anonyme), 'Courbevoie, France, a French corporation Application August 2, 1949, Serial No. 108,119

Claims priority, application France August 3, 1948 7 Claims.

The present invention relates to electrocardiographs and particularly to apparatus for producing on the screen of a cathode ray tube an image characteristic of the cardiac vector of a person whose heart is being examined.

An electrocardiograph is apparatus for studying the electrical activity of the heart. The heart exhibits electrical activity because the myocardium, i. e. the muscular substance of the heart, carries a negative charge when it is activated and a positive charge when it is resting or has recovered. When both activated and resting mus cle is present at the same time in difierent portions of the heart, the difierence in potential between the two induces an electrical field. This field permeates the body and can be detected by means of electrode plates on or inside the body. The part of the body that is closer to the resting or recovered muscle is influenced by the positive pole of the field while that part of the body which is closer to the activated muscle is influenced by the negative pole. The electrical field changes from instant to instant, both in force and direction, as the activation or recovery proceeds over the heart. The potential picked up by electrodes in contact with the body changes accordingly. By suitably placed electrodes, it is possible to determine both the direction and the magnitude of the electrical force thus generated in the body.

In order to study the electrical activity of the heart, it is convenient to use a vector which is called the cardiac vector or electrical axis of the heart. A vector is a quantitative and graphic representation of a force, in this case an electrical force. The cardiac vector thus represents the electrical force of the heart. Its symbol is an arrow, the length of which is proportional to the magnitude of the force and the direction of which is the direction of the force. The leading tip of the arrow indicates the orientation of the positive pole of the electrical force. As indicated above, the electrical force is continually changing and hence the vector representing it is an instantaneous vector.

The electrical activity of the heart is acornplicated process which is still not fully understood. In order to deal with it in a practical manher, it is advisable to resort to simplification. For one thing, the electrical activity may be considered as arising from a single source. Actually, electrical activity is occurring simultaneously in different parts of the heart but, for the sake of simplification, it may be averaged up and summated so as to be condensed into a single focus which is considered as being the center of the heart. This focus is thus considered to be the sole origin of the electrical field which permeates the body and may hence be considered as the point of origin of a vector representing the electrical force of that field.

It is an object of the present invention to provide improved apparatus for producing a visual representation or record of the cardiac vector of a person whose heart is being examined. By studying the characteristics of the cardiac vector, doctors are able to determine useful facts concerning the functioning and condition of the heart.

The objects, advantages and characteristics of the apparatus in accordance with the invention will be understood more fully from the following description and claims in coniunction with the accompanying drawings, in which:

Fig. 1 is a diagrammatic illustration of the manner in which the direction and magnitude of a cardiac vector are determined.

Fig. 2 is a schematic diagram of apparatus in accordance with the invention.

Fig. 3 shows a curve obtained with the apparatus.

According to a well established method of elec trocardiography known as the Einthoven system, three electrodes are secured in contact with the body of a patient being examined, the electrodes being located at the following points:

1. Right arm, herein designated as R.

2. Left arm, herein designated as L.

3. Left leg, herein designated as F.

For simplicity of calculation, the points at which the three electrodes are located may be considered as the corners of an equilateral triangle with the heart located at the center of the triangle. The electromotive forces between the electrodes at any instant may be represented by three component vectors lying on the sides of the equilateral triangle and hence disposed at an angle of to one another. Thus, as illustrated in Fig. 1, the electromotive force between points L and R may be represented by a vector 61, the electromotive force between points R and F may be represented by a vector as and the electromotive force between points F and L may be represented by a vector es. By vectorially adding the component vectors e1, c2 and e3, there is obtained a resultant vector This resultant vector represents the cardiac vector or electrical axis of the heart. In order that the resultant or central vector E may be taken as originating at the center 0 of the triangle (which represents the center of the heart) the component vectors e1, c2 and 62 are plotted on the sides of the triangle starting the respective vectors and the electromotive forces that these vectors represent.

As will be seen from the foregoing explanation in conjunction with Fig. 1, it is possible, theoretically, to take individual readings of the voltages between respective pairs of the electrodes to ascertain the values of the component vectors e1, es and eg and then plot the resultant vector E. However, since the values are constantly changing, graphical determination of the cardiac vector in this manner is not practical. It is therefore an object of the present inven tion to provide apparatus which will provide a visual representation of the instantaneous cardiac vector.

In accordance with the invention, electrometive forces obtained from the body are amplified and applied to a cathode ray tube or oscillograph in such manner as to produce an image which is characteristic of the central cardiac vector. The apparatus thus obtains the cardiac vector instantaneously from the component vectors representing the electromotive forces between pairs of electrodes. However, when using three electrodes, positioned in accordance with the Einthoven system, as described above, the component vectors are not perpendicular to one another and can hence not be applied directly to a cathode ray tube or oscilloscope having pairs of deflecting plates disposed at right angles to one another. It will be understood that a cathode ray tube'of the conventional kind having horizontal and vertical plates operates on the Cartesian system of coordinates, the deflection of the cathode beam by the vertical pair of plates representing the ordinate and the deflection by the horizontal pair of plates representing the abscissa of the system. It is an object of the invention to provide an electrical device which effects the required mathematical correction that is necessary in going from a system of oblique component vectors to the Cartesian system so as to obtain a correct synthesis of the cardiac vector.

As the vector or (Fig. l) is horizontal, the corresponding electromotive force can be applied directly (with suitable amplification) to a cathode ray tube to produce proportional horizontal deflection of the cathode beam. However, the electrornotive forces represented by the vectors cc and c3 cannot be applied directly to the cathode ray tube since they are neither vertical nor horizontal. In order to obtain a correct synthesis of the cardiac vector E, it is necessary to apply a voltage proportional to the horizontal component e1 to the horizontal deflecting plate of a cathode ray tube and to apply to the vertical deflecting plates a voltage proportional to the vertical component of the vector E, represented in Fig. 1 by the line Org. The value of the vertical component of vector E may be determined mathematically, reference being had to Fig. 1

O20i=OV and 0157:0102-902 (LOlVO being drawn as 60 and LgOO: being drawn as 30) Ob C2 11 60 sine and tan 30- #5 Therefore:

The Einthoven relation gives us besides:

ez=e1+ca (2) By substituting this value for e: in Equation 1:

Hence, in order to reproduce the cardiac vector E on a cathode ray tube, it is necessary to have a horizontal deflection, i. e. a deflection in the direction of the X axis. proportional to e1 and a vertical'deflection, i. e. a deflection in the direction of the Y axis proportional to l+ 3 #5 Thus, the vectorial synthesis of the cardiac vector E may be obtained solely from the two component vectors e1 and 63.

Apparatus for obtaining this synthesis is shown schematically in Fig. 2. Voltages equal or proportional to er and ea are applied either directly or'after equal amplification to'input terminals, I, l and 2, 2,"respectively, of the apparatus, the'terminals I and 2"being connected together and suitably grounded. Thus; input terminals l and l" are connected; respectively, to the electrodes at points R and L (Fig. 1) while input terminals 2 and 2' are connected, respectively, to electrodes at points F and L, it being understood that suitable preamplification may be interposed between the electrodes and the input terminals. A potentiometer P is connected across the input terminals land I and a similar potentiometer P1 is'connected across the

input terminals

2 and 2. The sliding contact oi the potentiometer P is approximately at the middle of the resistance so that the output voltage of the potentiometer is proportional to The sliding contact of the potentiometer P1 is near the end of the resistance to which the input terminal 2 is connected so that the output voltage of the potentiometer P1 is proportional to the entire input voltage e3. It will be seen that, if the input voltages er and ea were equal, the output voltage of potentiometer P1 would be twice that of the potentiometer P.

The sliding contact of the potentiometer P is connected by conductors 3 and 4 to the grids of identical amplifier tubes 5 and 6. The sliding contact of the potentiometer P1 is connected to the grid of an amplifier tube 1. The cathodes of the amplifier tubes 5, 6 and "I are connected through resistances n, r: and Ta, respectively,

to ground. The plate of amplifier tube 5 is connected through a load resistance T4 to a high voltage supply indicated at HT, The plates of amplifler tubes 6 and l are connected to a common terminal 8 and to a high voltage supply HT through a common load resistance r5.

Assuming equal amplification by the amplifier tubes 5, s and 1, the output voltage of tube 5 will be proportional to while the combined output voltage of tubes 6 and I will be proportional to gi-es Multiplying both quantities by 2', in order to simplify them, the output voltage of tube 5 may be considered as being proportional to 61 While the combined output voltage of tubes 5 and 1 may be considered as being proportional to (Bi-F283.

The common terminal 8 of the plates of tubes 6 and l is connected through a condenser 9 to one end of a potentiometer it which serves as a voltage divider, the opposite end of which is connected by a conductor 25 to an acceleration anode it of a cathode ray tube 2!) having a screen 25 and. a cathode 22. The sliding contact of the voltage divider it is connected by a conductor 23 to one of the vertical deflecting plates ll of the cathode ray tube 29, The sliding contact of the voltage divider it! is set so as to divide the voltage (cpl-2e? by the square root of 3, so that the voltage applied to the vertical deflecting plates i of the cathode ray tube is The plate of the amplifier tube 5 is connected through a condenser E2 to one end of a potentiometer E3 the opposite end of which is con nected by conductor is to the acceleration anode it of the cathode ray tube 28. The sliding contact of the potentiometer i3 is connected by conductor 2% to one of the horizontal defleeting plates it of the cathode ray tube. The purpose of the potentiometer I3 is to compensate for the fact that the horizontal deflecting plates are nearer the acceleration anode l6 than are the vertical deflecting plates 5 I. It is known that the pair of plates positioned nearest the anode produces a greater deflection than the pair of plates farther away from the anode if the potentials applied to the plates are equal. In other words, the cathode ray tube is more sensitive to the deflection plates nearer the anode. To equalize the sensitivities of the two pairs of plates, the voltage applied to the plates nearer the anode, i. e. the horizontal deflecting plates is, is appropriately reduced by the potentiometer l3.

It will thus be seen that an amplified voltage, proportional to the component vector 61, is applied to the horizontal deflecting plates M of the cathode ray tube 2c while an amplified voltage proportional to the function is applied to the vertical deflecting plates. The horizontal deflection of the cathode beam is hence proportional to the vector e1 while the vertical deflection is proportional to The resultant deflection of the cathode beam thus represents in direction and magnitude the central cardiac vector E.

It is therefore possible, in accordance with the invention, to use a cathode ray tube having two pairs of deflecting plates disposed at right angles to one another and yet produce an image characteristic of the central cardiac vector from two component vectors disposed at an angle of less than to one another. As will be seen from the example described above, this is achieved by applying to one pair of deflecting plates an amplified voltage proportional to one of said component vectors while applying to the other pair of plates an amplified voltage proportional to the algebraic sum of one of the component vectors and a multiple of the other of said component vectors divided by a trigonometric function of the angle between said component vectors.

In the foregoing description, the central cardiac vector E was obtained from the component vectors c1 and as. It can be obtained in a similar manner from component vectors c1 and ea or component vectors c2 and es, or from other component vectors disposed at an angle of less than 90 to one another, the potentiometers and other components of the apparatus being set in accordance with the mathematical relationship of the component vectors, as illustrated by the example described above.

From the foregoing description, it will be un derstood that the resultant deflection of the cathode beam represents, in direction and amplitude, an instantaneous cardiac vector. The spot made by the cathode beam on the screen at any instance thus represents the tip of a vector originating at the central point 0. The curves C1 and C2 in Fig. 3 represent curves traced by the tip of the vector during a cycle in the functioning of the heart, To facilitate study of the vector cardiogram thus produced, the cathode ray tube may be rotated about its longitudinal axis so that the vector E shown in Fig. 3 coincides with the vertical axis OY.

To avoid blurring of the image on the screen of the cathode ray tube due to successive images being superposed on one another, the horizontal plates of the cathode ray tube are preferably connected to a conventional sweep circuit (not shown) to impart to the image a sweeping movement the speed of which is proportional to the frequency of the phenomenon being investigated, e. g. 25 to 75 mm. per second.

By thus applying to the deflecting plates of a cathode ray tube suitably amplified component voltages obtained from electrodes in contact with the body, there is obtained an image characteristic of the cardiac vector of a person being examined. By employing a screen capable of strong afterglow, the path of the spot produced by the cathode beam on the screen of the cathode ray tube can still be seen several seconds after the beam has passed and a visible curve traversing the screen is thus obtained.

I claim:

1. In an electrocardiograph for producing a pattern characteristic of the central cardiac vector from two component vectors derived from electromotive forces in the body of a person being examined and disposed at an angle of less than ninety degrees to one another, a cathode ray tube having two pairs of deflecting plates disposed at right angles to one another, means for obtaining voltages proportional to said component vectors, means for amplifying one of said voltages and applying it to one of said pairs of plates, means for amplifying the other of said voltages, circuit means for algebraically adding one of said amplified voltages and a multiple of the other, and circuit means for dividing said sum by a trigonometric function of said angle and applying said divided voltage to the other of said pairs of plates.

2. In an electrocardiograph for producing a pattern characteristic .of the central cardiac vector from two component vectors, er and es, derived from electromotive forces in the body of a person being examined and disposed at an angle of approximately sixty degrees to one another, a cathode ray tube having two pairs of deflecting plates disposed at right angles to one another, means including an amplifier for applying to one of said pairs of plates a voltage proportional to the vector 21, means including an amplifier for providing a voltage proportional to two times the vector as, circuit means for adding the voltage proportional to the vector 61 and the voltage proportional to two times the vector 63, and circuit means for dividing the sum of said last mentioned voltages by the square root of three and applying the resulting voltage to the other of said pairs of plates.

3. In an electrocardiograph for producing an image characteristic of the central cardiac vector from two component vectors derived from electromotive forces in the body of a person being examined and disposed at an angle of less than ninety degrees to one another, a cathode ray tube having a screen, means for producing a cathode ray and two pairs of deflecting plates disposed at right angles to one another, means including an amplifier for applying to one of said pairs of plates a voltage proportional to one of said component vectors, means including an amplifier for providing a voltage proportional to a multiple of the other of said component vectors, circuit means for adding said two voltages, and circuit means for dividing the sum of said two voltages by a trigonometric function of the angle between said component vectors and applying the resulting divided voltage to the other of said pairs of plates, the voltages applied to said plates acting to deflect the cathode ray to produce said image on said screen.

4. In an electrocardiograph for producing an image characteristic of the central cardiac vector from two component vectors derived from electromotive forces in the body of a person being examined and disposed at an angle of less than ninety degrees to one another, a cathode ray tube having a screen, means for producing a cathode ray and two pairs of deflecting plates disposed at right angles to one another, means for equalizing the sensitivity of the two pairs of plates, means including an amplifier for applying a voltage proportional to one of said component vectors to one of said pairs of plates, means including an amplifier for providing a voltage proportional to a multiple of the other of said component vectors, circuit means for adding said two voltages, circuit means for dividing the sum of said two voltages by a trigonometric function of the angle between said component vectors and means for applying the resulting voltage to the other of said pairs of plates.

5. In an electrocardiograph for producing an image characteristic of the central cardiac vector from two component vectors derived from electromotive forces in the body of a person being examined and disposed at an angle of less than ninety degrees to one another, a cathode ray tube having a screen, means for producing a cathode ray and two pairs of parallel deflecting plates, the plates of one pair being in planes perpendicular to the planes of the plates of the other pair, means for obtaining voltages proportional to each of said component vectors, means for amplifying one of said voltages, means for applying said amplified voltage to one of said pairs of plates, means including an amplifier for obtaining a voltage proportional to a multiple of the other of said voltages, circuit means for adding to the voltage thus obtained a voltage equal to the first mentioned amplified voltage, circuit means for dividing the sum of said last mentioned voltages by a trigonometric function of the angle between said component vectors and means for applying the resulting divided voltage to the other of said pairs of plates.

6. In an electrocardiograph for producing an image characteristic of the central cardiac vector from two component vectors derived from electromotive forces in the body of a person being examined and disposed at an angle of less than ninety degrees to one another, a cathode ray tube having a screen, means for producing a cathode ray and two pairs of parallel deflecting plates, the plates of one pair being disposed at right angles to the plates of the other pair, terminals for receiving a first voltage proportional to one of said component vectors, a voltage divider connected across said terminals, first and second amplifiers connected in parallel to the output or" said divider, means including a variable voltage divider for applying the output of said first amplifier to one of said pairs of plates, terminals for receiving a second voltage proportional to the other of said component vectors, a voltage d vider connected across said last mentioned terminals, a third amplifier connected to the output of said last mentioned divider, means connecting the outputs of the second and third amplifiers to a common terminal and means including a variable voltage divider connecting said common terminal with the other of said pairs of plates.

7. In an electrocardiograph for producing an image characteristic of the central cardiac vector from two component vectors derived from electromotive forces in the body of a person be ing examined and disposed at an angle of less than ninety degrees from one another, a cathode ray tube having two pairs of deflecting plates disposed at right angles to one another, means for providing a first voltage proportional to one of said component vectors, means for amplifying said voltage including first and second amplifiers connected in parallel with one another, means for applying the output of said first amplifier to one of said pairs of plates, means for providing a second voltage proportional to the other of said component vectors, a third amplifier for amplifying said second voltage, means connecting the outputs of the second and third amplifiers to a common terminal and means including a variable voltage divider connecting said common terminal with the other of said pairs of FOREIGN PATENTS plates. Number Country Date MICHEL BROSSELIN- 424,162 Great Britain Feb. 15, 1935 OTHER REFERENCES A method of analyzing the electrocardiogram, by Hubert Mann, volume 25, N0. 3, of N her Name Date the ATOhIVSS of Internal Medicine, pages 282 to 2 Heller Sept 10 1940 294, inclusive, of the issue of March 1920. A 2:229698 Honmann Jan 23 1941 10 copy of this work is available in Division 55 of the 2 2 4 15 s et 1 A 25 1942 United States Patent Office.

References Cited in the file of this patent 5 UNITED STATES PATENTS