US2229698A - Electrocardiograph - Google Patents

Description

Jan. 28, 1941- v H. E. HOLLMANN I 12,229,698 v ELECTROCARDIOGRAPH I June 2 I I i L i /R T; 'l l A E I I I 7 2 Ji'ans ATTORNEY.

IYNVENTOR.I

Jan. 28, 1941 H. a HOLLMANN ELECTROCARDIOGR'APH Filed June 5'15, 193*! 2 Sheets-Sheet 2 .10 r INVENTOR n5 firacbiwllmnn'n AT ORNEY I Patented Jan. 28, 1941 I 2,229,698 nLao'raoosnmoanarn Bans Erich 'Hollmann, Berlin-Idchterfelde, Germany, assignor to Radio Patents Corp, New York, N. Y., a corporation or New York Application June 15, 1937,,Serial No. 148,325

In Germany July '1, 1936 '1 Claims. (c1. lac-2.06)

The present invention relates to electrocardiographs as used in the medical sciences for observation and/or registry of the minute potential variations between various points of the human 6 body causedby the action of the heart, and objects of the invention are to provide a novel means for and a method of producing electrocardiograph records.

As is well known, electrocardiographs depend for their action upon the fact that the action of the heart in the human or animal body is accompanied by voltage impulses known as biological action voltages or potentials of the order of about .001 volt between the limbs such as between the right and left arms or between the arms and legs. By studying the characteristics of such impulses when they are recorded as continuous waves by an electric oscillograph on a light sensitivesurface, such as the luminescentrscreen' of a cathode ray oscillograph or a photographic film or paper strip, physicians are enabled to determine certain facts concerning the function and condition of the heart. a

According to an improved method and system of electrocardiography, various points of the body are tapped by means of suitable electric connectors strapped to the patient to observe and/or record variations of the reaction potentials between these points.

According to a well established method known as the Einthoven system-it has become customary. to use the following tappings or leads as they will be referred to hereinafter tor the purpose of this specification for drawing several action voltages from the body of a patient? 4 Lead 1: between right arm" to left arm Lead 11: between right arm to leit'leg Lead III: between left arm to left le 40 By simultaneously observing the potential fluctuations between these points, valuable conclusions can be drawn on the function and condition of the heart. 1

-As is understood, however, other tappings or leads may be used, such as between difierent points of the breast encircling the heart, or between the breast and the back and others.

An object of the present invention is the provision 01 a novel" method or and system for electro-" cardiography especially adapted to the'Einthoven system of derivin action voltages from the patient enabling a direct indication and/or recording of the action voltages and their relation to each other. 1

Another object is the provision of an electrocardiograph adapted to produce a direct indication and/or record of the'electrical axis of the heart and its various positions during each palpitation or heart beat cycle.

Further objects and aspects of the invention 5 will become more apparent irom the followin detailed description taken with reference to the accompanying drawings iorming a part of this specification andwherein- Figures 1 and 2 are theoretical diagrams ex- 19 planatory oi the function and operation oi the invention,

Figure 3 illustrates an electrocardiograph recording system comprising a cathode ray oscillo graph designed and constructed in accordance 15 with the invention,

Figure 4 is'a. theoretical diagram explanatory of the function-of Figure 3.

Figure 5 illustrates a modification of a deflect ing system for a cathode ray osciliograph for use 20 in ,an arrangement according to Figure 3,

/Figure 6- shows an electrocardiogram system of the type according to the invention combined ,"with means for additionally producing the ordinary electrccardiographic records by means of a as single oscillograph device,

Figure 7 is a partial view of a modified cathode ray cscillograph constructed in accordance with the invention showing the use oi magnetic defleeting means I Similar reference characters identity similar elements throughout the different views of the drawings.

The conditions created by the three leads in accordance with the Einthoven principle may be best understood by consideringthe tapping points atthe limbs as the corners oi? an equilateral triangle containing the heart in its center. This is shown in Figure [wherein-13;, represents the tapping point at the right arm, L the tapping point at the left arm, and B the tapping point at one 01 the legs such as the left leg, whereby the leads or potential differences between these points are represented by the ccnnectinglines I, H, m or these points. Since the exciting action through the muscular system or the heart pro (seeds from the base to the top during each contraction, the heart has a definite electrical ems determined by :the connecting: line between the points of -greatest.biological potential diflereuce which connecting line coincides approidmately with the. anatomical axis of the heart. From the Einthoven lead triangle. the relative magnitudes of the separate action voltages produced by the .individual leads may be determined for which as purpose it is only necessary to project a voltage vector A in the direction of the electrical heart axis whose length is preferably equal to the maximum potential difference during the so-called initial peak of the heart beat curve (a1, a: and E3) upon the three sides of the lead triangle as shown at A1, A2, A1. In case of normal position of the heart, such as shown-in Figure 1, the electrical axis of the heart is approximately parallel to the lead II, while the derivation III supplies the weakest potential component. If the heart vector within the triangle has a anatomical position of the heartmay be obtained on the basis of a simple geometrical scheme, suchf as is not always possible by means 01 X-ray re-' cording or other methods.

, For the practising physician, it is highly incon venient and cumbersome to carry out separately foreach patient the vectorial summation of def inite instantaneous values obtained from the three Einthoven leads on the basis of the'sch'eme shown in Figure 1. To, overcome thisinconvenience it has'been proposed to 'applytwo of the action voltages to separate deflecting systems of a cathode ray oscillographarranged with their axis at a right angle whereby a kind. of Lissajou figure is obtained upongt'he viewing or recording screen who'se"shape"depends 'on the phase displacement between theaction voltages being recorded and from the mainaxis of which certain, conclusions may be drawn on theanatomical orientation of the heart. In'order to fully complete the analogy with the Einthoven system, the coordinates of the recording system should fornrangles similar to those of the equilateral lead triangle. I This obviously simple method, however, has a serious disadvantage V preventing its general adoption in practice. .For better illustration the following case will be considered. It is assumed thatthe electron beam in the cathode ray oscillograph is deflected in 'twoj'rectangular coordi' nates by potentials supplied by the leads I and II. Assumingiurther a speciflc case as illustrated in Figure Zcorresponding to'the so-called "situs inversus or inverted position of the heart axis, the action voltage supplied by lead 11 might be equal to zero, while the voltages supplied by the leads I and II might be equal to each other. If the deflecting systems of the oscillograph are connected as mentioned above, that is, it lead 111 is entirely disconnected, no potential is produced'bylead II so that the el'ectron'beam is deflected only by the potential produced by lead I. As a result, the electron beam is deflected in one direction only which has no relation what soever to the direction oi the heart vector-or the anatomical position of the heart to be determined. These conditions are substantially the same if in place of rectangular coordinates do fleeting systems oriented at a 60 angle areused. A determination-0f the position of the heartis thus impossible under the circumstances de-@ scribed. r b

In order to obtain. a Lissaio'u flgure in the above case, it would be necessary to connect the deflecting systems to the leads. I and'III. From this, however, it follows that this method is not absolutely reliable but subject to the discretion on the part of the physician who may choose e s o diasnosins urposes. As a result, the clinical value of this different position or is" rotated, the relative magnitudes and the polarity oi the separate leads will vary -accordingl From the above it is seen that a clear picture. oi' then,:Einthoven leads or in other ray or other recording beam is deflected by the three action voltages simultaneously and in ditrical heart vector in such a manner that arbitrary combinations are impossible. 'the'new method employs three deflection simultaneouslyin three directions forming angles of Accordingly,

60, with each other and cooperating with the words, the cathode l5 rections forming angles of 60.

According to one embodiment of the invention, a cathode ray oscillograph is used comprising three'deflecting' systems each' controlled by one of the action-voltages drawn from the patient's body and related according to the Einthoven or any equivalent diagram. The three deflecting systems are successively or simultaneously passed by the electj'ron'beam-insuch a manner that the resultant deflection of the luminous recording spot produced on the fluorescent screen of the oscillograph is determined by the vectorial sum oi the instantaneous values of the action voltages applied to the deflecting systems. I "For'the recording of the biological action potentials by means of a cathode ray oscillograph, it is necessary to provide an amplifier for increasing the heart action potentials (which are of the order of. one milivolt) sufficiently to effect the'd'eflection of the electron beam. Great difliculties areoften' experienced in practice due to the fact that'the highly sensitive amplifier having itsinput connected to the patient who acts as an antenna is-liable to pick up a great amount of interference or disturbing potential variations originating either from the 60 cycle house lighting'systems or from other sources of disturbance such as high frequency medical devices. dia- 3 thermy or X-ray and other electrical apparatus. By grounding the system, a certain protection against interference may "be obtained, but under circumstances the ground connection by which a deflnite 'reference point is established inthe interfering field may'result in a substantialincrease of the disturbance-potentials applied to the system to such an extent as to render the records obtained substantially unintelligible. In

- order to reduce disturbances of this kind. it was necessary heretofore to carry out the observation or registry 01' the action potentials in an electrostatically screened room or a so-called Faraday cage, or it no screened room was available, to

screen thepatientby 'a metallic or metal fabric 0 cover. All these expedients, however, involve great difllculties in practice besides being expen siveand not affording ,a complete protection as the fcase'oi a metal ,iabricscreen surrounding the patient.' Moreover, the latter is impossible apparatus is small compared with the extension of a disturbing field, the origin of which isusually at a far distance so thatthe interfering field in the vicinity of the patient. and the apparatus may be regarded as homogeneous. From this it follows that the disturbing potentials wherever they enter the patient or the apparatus may be assumed to be of equal phase. In order to separate the disturbancepotentials' from the action potentials produced by the heart, the arrangement is made such that the action potentials are applied to a differential or push-pull amplifier and that the indicator or recording device 'is also connected in differential fashion between the outputs of the amplifiers. In this manner only the potentials produced by the heart action are applied to the inputof the amplifiers while the equally phased disturbance potentials, although they may be considerably amplified, are mutually balanced by the differential action of the indicator or recording device.

In my copending application Serial No. 58,048, filed January 8, 1936, now Patent No. 2,133,140 issued October 11, 1938, there is disclosed a method by which the Einthoven action potentials may be amplified and recordedfby the aid of only two amplifiers each serving to amplify one of the action potentials while the third potential is represented as the sum or difference of the two former and serves to operate an o'scillo graph connected between the output circuits of this purpose the amplifiers In an arrangement of this type. the difierential principle is employed only for the third potential and in fact substantially no interference peaks appear in the corresponding record. The other derivations or potentials, however, which are directly amplified and recorded aresubject to interference to the full'extent.

By the present application a new method and system is proposed for utilizing the differential principle for a triple electrocardiograph system which has the further advantage of a. considerable saving of amplifiers and other parts For both the input and output circuits of the three amplifiers are arranged in star connection while the deflecting systems of the cathode ray oscillograph are also arranged in.

either star or delta and connected to the output circuits of the amplifiers. Anarrangement of this type designed and constructed in accordance with the invention is illustrated diagrammatically by Figure 3. In the latter there is shown a cathode ray'oscillograph comprising an evacuated vessel 20 having mounted therein an arrangement for producing a concentratedelectron beam 1' known as .an electron gun and consisting in the example shown of a cathode 2| which may be a directly heated or indirectly heated cathode surrounded by a pre-conbentration cylindrical electrode 22 negatively biased with respect to the cathode in a known manner. The thus produced electron beam emitted from the cathode is further concentrated or focussed by means of an electron optical lens system of any known type, consisttured acceleration electrodes 23 and 24 which are suitably positively biased with respect to the cathode so as to produce a sharply concentrated electron beam impinged upon the luminescent screen 21 applied to the opposite wall of the tube or arranged inany other suitable manner. Any other known ray generating system may be provided, the details thereof having been omitted from the disclosure and drawings for the sake 'fiers shown at ing in the example illustrated of a pair of. aperof simplicity and as present invention. There are further shown three pairs of electrostatic deflecting plates 25- 26, 25'26, 25"-26" arranged with their axes forming angles of 60 with each other and serving to effect deflection of the electron beam simultaneously in three directions in accordance with the respective action potentials drawn from the patient at the points R, L and B in the manner described hereinabove. Before application to the deflecting plates 25-26, 25 26',.24"- 26",,the potentials are amplified by means oil separate amplifiers such as vacuum tube amplilfl, l0 and I0", respectively, for which purpose the tapping points R, L and B are connected to the grids or input electrodes i3, I3 and l3,.respectively, ofthe amplifiers in the manner shown. The. cathodes, ,II and I1 of'the amplifiersare connected to ground at l8 or to any other reference point of the system through a switch l6 and a biasing battery ll the purpose of which will be described later.

cuit represented by the leads between the points not forming part of the R, L and B. The star points or anodes of the amplifiers Hi, l0 and iii" are connected to the junction points between successive deflecting plates of the three deflecting systems of the cathode ray oscillograph connected in delta in the example illustrated. For the latter purpose, plate 26 of the first deflecting system is connected to, plate 25 of the second deflecting system, the junction point thereof being connected to the anode l2, plate 26'v of the second deflecting system is connected to the plate 26 of the third system and the junction therebetween is connected to the anode l2', while the plate 25" of the third system is connected to the plate 25 of the first system and their junction is connected to the anode 12". In this manner by connectingboth the input and output circuits ofthe amplifiers in star and by furthe'r connecting the deflecting systems of the cathode ray oscillograph in concatenated fashion to the out-' put circuits of'the amplifiersonly the potential diiferences between the points R, L and B are effective in causing the deflection in the electron beam while all other equally phased potentials applied to the input of the amplifiers such as the undesirable disturbance or interfering potentials are eliminated by the difierential action in all three amplifying and recording channels.

As is understood, any desired number of amplifying stages as well as any suitable type of amplifying circuit may be used for the purpose of the'invention, one amplifying stage having been shownonly for simplicity of the disclosure and drawing.

Referring to Figured, the deflection of the electron beam in an arrangement of the type according to Figure 3 is further illustrated. The case considered corresponds substantially to the general case shown by Figure 1 wherein the vector of the electrical heart voltage A forms an angle a with the horizontal or lead I. The re-' sulting deflection of the electron beam caused by the individual componentsAl, A2, M which as pointed out are obtained by projecting the vector A upon the sides of the equilateral tri-' angle is found by vectorially adding the components Al, A2, A3 at angles of 60. By this geometrical summation a resulting vector S as shown in Figure 4 is obtained including an angle a: with the horizontal or derivation I. It canbe shown by a detailed theoretical analysis as presented in an'article appearing in Zeitschrift fiir Instrumentenkunde" V0. 47, 1937, No. 4, espe cially on pages 149. 156and 157, of which the inventor is co-author that the two vectors A and S are parallel or in other words, that the angle at is equal to the angle a as shown in the diagram so that the vector S appearing upon the screen of the oscillograph directlyindicates the direction of the electrical axis of the heart. The analysis further shows that this law which has been demonstrated purely graphically in Figure 4 applies to all possible cases and for all positions of the electrical heart vector.

As seen from the diagram, the length of the resulting vector S differs from the length of the heart vector A. It is found that the two vectors have a constant ratio of S ill-1.0 I l which is independent of the angle a. This may be taken into account in the calibration of the device.

A further advantage of the arrangement according to the invention compared with the previously described arrangement using only .two derivations for producing a Lissajou figure, aside from its universal applicability and increased efliciency, is the fact that the direction of the heart vector S as observed is substantially independent of any phase displacement between the separate action potentials. While, as :is well known, the main aXis of a normal Lissajou figure produced by deflections in two directions depends on the phase relation between the deflecting potentials, this is not the case in an arrangement and method according to the invention based on the Einthoven voltage diagram wherein the ab solute sum of the three derivation vectors at any time is equal to zero. On the basis of this,general relation the effect of any phase shift between the separate action potentials such as caused by the time delay in the connecting lines and the like is substantially eliminated ascan be proven by detailed analysis.

For the purpose of .clinical'diagnosis, the prin ciple underlying the new method implies that the vector 8 should be a straight line provided that the heart vector during the contraction of the heant retains a.,flxed direction. The latter-assumption is by no means fulfilled anatomically since the paths along which-theexci-ting action progresses are not along a straight line but are more or less curved depending on the anatomical structure of the muscular system of the, heart, Thus, if the direction of the deflection of theelectron beam during the initial peak of a heart beat cycle as shown at a1, a2, a: in, Figure 1 varies or rotates, there is no longer produced'a straight line upon the luminescent screen, but rather: a curved line as shown at s in Figure 3 which shows the progress of the exciting action through the heart muscular system. This phenomenon enablesthe physician to recognize disturbances in the function of the heart and propagation'of the exciting action in a most simple manner which has not been possible with any one of the devices and methods heretofore known in the art.

In order to simultaneously observe and/or record the instantaneous values ofthe action potentials or heart beat curves as shown in'ai, a2, a: in Figure 1 in additiori to the indication and/or recording of the electrical heart axis and its rotation during theindividual palpitations or heart beat cycles, the novel method maybe combined with an arrangement comprising three separate oscillographs for individually recording the action potentials, or a multi-gun'oscillograph tube may be provided for this purpose of the type described in my above mentioned copending application.

In the construction of a cathode ray oscillograph of the type shown in Figure 3 care should be taken that all three deflecting system have an equal deflecting sensitivity. Since the systems are displaced in the direction of the electron beam this can be obtained by varying the length of the deflecting plates or the distance between cooperating plates to compensate for the different leverage or distance from the center of the deflecting fields to the luminescent screen. In order to check the balance or sensitivity of deflection'of the separate systems including equality of gain of the ampliflersfthe key I 6 is provided which when depressed will apply a small testing potential supplied bythe battery I! between the star point or the cathodes of the amplifier and ground. If the amplifiers and deflecting systems are balanced, the electron beam should remain in its zero position independently of whether the key I8 is depressed or in its open position since no potential difference is introduced in this case in one of the sides of the triangle and since only the average potentials at the corners of the in put and output triangles are lifted and depressed uniformly.

Referring to Figu're5, there is shown asimplified arrangement for effecting a triple deflection of the electron beam in accordance with the invention wherein equald'eflecting sensitivity is obtained. According to this embodiment the three deflecting plates, 30 and 30" connected to the anodes l2, l2 and i2" of the amplifiers, respec tively, are arranged so as to form the sides of an equilateral triangle. As long as the deflection of the electron beam is small compared with the distance' between the plates, which practically is always the case in view of the increased beam leverage in a construction of this type, the operation of a triple "plate deflecting system of this type is substantially the same as in the case of separate deflecting systems shown in Figure 3. Only after the electron beam has been deflected from its zero position to such an extent as to enter the marginal zones of the deflecting fleld disturbances, are fleld distortions observed. Otherwise, the function and vectorial summation in the case of a triple plate systemof this type is substantially the same as in the 'case ofv three separate plate systems shown in the previous illustration.

While there has been shown a cathode ray oscillograph'for illustration of the novel principle and arrangement according to the invention, it is understood that any other suitable type of oscillograph known for the recording of Lissajou figures or the like may be employed for the purposes of the invention.

It is furthermore possible to use a single amplifier in "place of three separate amplifiers in conJunction with a pair of synchronous switching devices periodically connecting the input and output circuits ofthe amplifier with the points R-L, ,B'and L B and the corresponding deflecting systems, respectively, at .a rate which is high ordinary electrocardiographic record upon a.

moving light sensitive strip such as a Photographic film or bromide paper, whereupon the first deflecting system is rendered inactive and the three action potentials derived from the Einthoven tap points are applied to a second triple deflecting arrangementaccording to the.

present'invention for producing a record of the electrical heart axis on the same recording strip, thereby to supply the physician with direct detailed information regarding both the instantaneous values of the heart action potentials as well as their functional relation on one and the same record in a most simple and easy manner and by means of a single recording apparatus.

There is shown in Figure 6 a cathode ray oscillograph substantially similar as shown in Figure 3, but provided with a triple deflecting system comprising deflecting Y plates 30, 30' and 30" similar to those shown in Figure 5. In addition to the triple deflecting system there are provided a pair of parallel deflecting plates 3| and 32 serving to produce a record of the instantaneous values or heart beat curves. Numerals 33 and 31 represent a pair of switching devices which are' preferably mechanically coupled such as indicated at 36. The device 33 has a pair of movable contacts 34 and 35 arranged to cooperate with four pairs of stationary contacts l---l, 2-2, 3-3 and 4-4, connected tov the anodes l2 l2 and I2" on the one hand, and to the deflecting plates 3! and 32 on the other hand in the manner shown. The switching device 31 is; provided with three movable contacts 38, 33 and 40 arranged for cooperation with two sets of stationary contacts l-l-l, 2-2-2 and connected to the anodes l2, l2 and [2! on the one hand, and to the triple deflecting plates 30, 30' and 33'? on the other hand in the manner shown. 'In the positions l-l, 2-2, and 3-3, of the switch 33, the action potentials I, H and III are successively connected to the deflecting plates such as shown at M, 0.2 and a3 in Figure 1 may be recorded upon a' moving light sensitivestrip or film 42 by means of a lens 4| in a known manner. At the same time the plates 33, 30' and 30" are connected to ground I3 by the position of the contacts 38, 39 and 30 of switch 31 'as shown in the drawings. If the contacts 34 and 35 are moved to position 4-4 and grounded, the contacts 33, 39 and 40 are moved into position 2-2-2 whereby the amplified action potentials are applied to the triple deflecting system 30, 30' and 30" and a record is produced on the fluorescent screen indicating the position and rotation of the electrical axis of the heart in the manner- I0, 40' and 40'' 31 and 32 whereby normal electrocardiographic' records 5 any other desired records may be groduced in succession by means of a system of this type upon the same viewing screen and/or record strip.

In place of electrostatic deflection, the oathode ray beam may bedeflected by means of a magnetic field in a known manner. Thus, the electrostatic deflecting plates 3| and 32 may be replaced by a pair of magnetic field coils arranged on the outside of the tube in a manner well known. Furthermore, in place of the triple deflecting plate system, three magnetic field coils may be provided with their axis arranged at 60 and connected in, star with the common star point leading to the positive pole of the anode potential source and with the open terminals directly connected to the anodes of the amplifiers such as illustrated. in Figure 7.

While I have described my invention with specific reference to the method'of operation and arrangement of parts and circuits disclosed and shown herein for illustration, it is understood that the novel concept, and underlying idea of the invention is susceptible of numerous variations and modification-s coming within the broad scope and spirit of the invention as defined in the appended claims. The specification and drawing are accordingly to beregarded in an illustrative rather than in a limiting sense.

I claim:

1. In an electrocardiograph, means for drawing a plurality of action voltagesfrom different tapping points of a patient forming'a ring connected multi-phase system with the heart inthe oentre,. means for amplifying said voltages, a cathode ray oscillograph comprising means for producing a concentrated electron beam and a plurality of deflecting arrangements adapted to deflect said electron beam in diflerent directions related substantially as the lines connecting said tapping points, means for impressing each of the amplified action potentials upon one of said deflecting arrangements to deflect said beam ac-. cording to the vectorial sum of the instantaneous values of the voltage vectors of said multi-phase system, a further deflecting arrangement for defleeting said electron beam in a single direction, and a switching arrangementbetween the output of said amplifying means and said deflecting arrangements for recording each of said action voltages independently'by said second deflecting arrangement" and for recording the-vectorial resultant oi all of said-action voltages by said first deflecting arrangements.

tapping points of a patient forming a ring connected multi-phase system with the heart in the center, means for amplifying said voltages, a

cathode ray oscillograph comprising means for producing a concentrated electron beam and a first deflecting arrangement adapted to deflect said electron beam in diflerentdirections related substantially as the lines connecting said tapping points, means for impressing the amplified action potentials upon one of saiddeflecting arrangements to deflect said beam according to the vectorial sum of the voltage vectors of said multi-- phase system, a second deflecting arrangement for deflecting said electron, am in a single direction, means comprisingis tching means between said tapping points and said first and second deflecting arrangements for temporarily rendering ineflective said first deflecting means and for successively controlling said further defleeting arrangement by the individual action voltages, and a luminescent screen impinged'by said electron beam.

3 An electrocardiographic recording system comprising leads for drawing three'component action potentials from tapping points on both arms and one leg of a patient, means for equally amplifying the action potentials drawn, a cathode ray oscillograph comprising means for producing, accelerating and iocussing an electron beam and three. deflecting systems oriented relative to one another so as to deflect said beam simultaneouslyin three directions at to one another, a luminescent screen arranged to be impinged by said beam, and means for impressing each of the amplified action potentials upon a separate deflecting'system, to produce a resultanttrace on said screen indicative of the instantaneous orientation' of the electrical heart axis during the cardiac cycle.

4. An electrocardiographic recording system comprising leads for drawing three component action potentials from tapping points on both arms and one leg of a patient, a triple-amplifier having each of its input electrodes excited by a separate one 01' the action potentials drawn, a cathode ray oscillograph comprising means for producing, accelerating and focussing a concentrated electron beam and three pairs of electrostatic deflecting plates having axes relatively oriented at 60 from one another, said deflecting plates being connected in star, aluminescent screen arranged to be impinged by said beam, and coupling connections fromeach of the star points of'said deflecting plates to a separate one of the output electrodes of said triple amplifier to simultaneously deflect said beam by said component action potentials, to produce a resultant trace upon said screen indicative of the instantaneous orientation of the electrical heart axis during the cardiac cycle.

5. An electrocardiographic recording system comprising leads for drawing three component action potentials from tapping points on both arms and one of the legs oi a patient, a cathode ray oscillograph comprising means for producing, accelerating and focussing a concentratedelectron beam and three electrostatic deflecting plates arranged in the form of an equilateral triangle, a luminescent screen arranged to be impinged during the cardiac cycle.

by said beam, and coupling connections from each of'said plates to a separate one of the output electrodesof said amplifier to simultaneously deflect said-beam by said component action potentials, to produce a resultant trace upon said screen indicative of the instantaneous orienta tion of the electrical heart axis during the cardiac cycle.

6. An electrocardiographic recording system comprising leads for drawing three component action potentials from tapping points on both for controlling each of the deflecting systems by a separate one of the amplified action potentials supplied by saidamplifler, to

produce a resultant trace upon said screen indicative of the instantaneous orientation of the electrical heart axis 7.. An electrocardiographic recording system comprising leads for drawing three component action potentials from tapping points on the body of a patient substantially equidistant from and equally angularly spaced with respect to the heart, means for equally amplifying the action potentials drawn, a cathode ray oscillograph comprising means for producing, concentrating and focussing an electron beam and three defleeting systems oriented relative to one another so as to deflect said beam simultaneously in three directions at 60. to one another, a luminescent screen arranged to be impinged by said beam, and means for impressing each of the amplified component action potentials upon a separate one of said deflecting systems, to produce a resultant trace on said, screen indicative of the instantaneous orientation of the electrical heart axis during the cardiac cycle,

HANS ERICH HOLLMANN.

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