The usefulness of vectorcardiography Vectorcardiography in the early diagnosis of acute myocardial infarction: Preliminary report LEONARD MENNEN, D.O. Kansas City, Missouri This paper is a preliminary report technical problem in receiving laboratory re- of experience with a panoramic sults promptly, and valuable time may elapse before the seriousness of the patients condi- vectorcardiograph in confirming the tion is known. presence or absence of acute myocardial When such procedures give only equivocal infarction when the initial results, one searches for a more comprehensive electrocardiogram was equivocal. and sophisticated method of studying the vec- The theoretical basis for tors produced by the heart. vectorcardiography is discussed. Three This paper will relate preliminary experi- ence using a panoramic vectorcardiograph to cases are reported to illustrate the confirm the presence of acute myocardial in- usefulness of vectorcardiography. The farction when the initial electrocardiogram was depolarization changes that occur inconclusive. when myocardial activity is altered are pointed out. Vectorcardiography is Basis for vectorcardiography still in the embryonic stage and there Vectorcardiography is a theoretical advance- ment over the electrocardiogram for the follow- are technical difficulties and lack of ing reason : The electric field of the heart agreement on such factors as the exists in three-dimensional space and there- most efficacious lead system. In this fore must be expressed as such. One can predict study vectorcardiography has been a three-dimensional synthesis from the given found to be a useful tool in the electrocardiogram curves, but only within lim- evaluation of acute myocardial its, since precise vector synchronism cannot be attained. infarction. Its value in other instances A minimum of three physical leads will rep- of altered myocardial activity is under resent true X, Y, and Z electrical co-ordinates. continuing study. This is necessary for accurate measurements of the X, Y, and Z components of the dipole vector.2 To form the frontal plane vectorcardiogram, one lead representing the X co-ordinate is used The importance of early diagnosis of acute myocardial infarction has been stressed re- peatedly. Electrocardiography and laboratory _1_ studies have aided clinical determination of 1 altered myocardial activity. However, the H ---I--0- z-H---t- --- T electrocardiogram does not always substan- r tiate the diagnosis, and the laboratory studies, Frontal Sagittal Horizontal namely serum enzymes, are often elevated in Fig. 1. non-cardiac diseases. Frequently there is a 494/70 centripetal t R (vertex) i II (R loop) S i T .. ■ ---7 % .- . .. • Alba.-- .. , %..?I 4,- centrifugal I (Q loop) Fig. 2. Components of the vectorcardiographic loop. Fig. 4. Admission electrocardiogram of patient in Case 1. Fig. 3. Mobile panoramic vectorca/rdiograph used in study. ueiuieu uy analyzing ine imam 5 posiLion.- as the horizontal axis input, and a second lead The sagittal plane is formed by using the representing the Y axis is used as the vertical lead representing the Z component and the axis input to an oscilloscope. When this is lead representing the Y component as the two accomplished, the X input and the Y input act perpendicular signal inputs to the same cath- simultaneously upon the beam and cause the ode ray tube beam.2 beam to be displaced in an XY graphic pat- The horizontal plane projection of the dipole tern. At any one instant during the cardiac vector is obtained by utilizing a lead which cycle the XY axis of the dipole vector can be represents the X and Z components of the Journal AOA/vol. 66, January 1967 495/71 R R Frontal plane — Horizontal plane-- I A S A Horizontal plane Rt. sagittal plane A I Fig. 5. The vectorcardiogram of patient in Case I shows a disappearance of the Q loop in. the horizontal plane indicating a loss of the normal first septal vector. In the same plane (upper right and, for greater magnifica- tion, lower left) the centrifugal limb of the R loop has lost its normal configuration and is rotated backward, suggesting necrosis to the anterior and lateral regions of the free left ventricular wall. The J-point is also dis- placed. The sagittal plane demonstrates significant posterior displacement of the initial vectorial forces. In the frontal plane abnormal rotation is also noted. These findings were interpreted as representing an acute myo- cardial infarction involving the middle and lower portions of the interventricular septum, and the anterior and lateral regions of the free left ventricular wall. dipole vector as perpendicular signal inputs to rectangular systems and the modifications by the same cathode ray tube beam. In a similar Grishman and Frank. manner, the frontal (XY), sagittal (ZY), and Orthogonal lead systems differ from those horizontal (XZ) plane projections of the di- based on the equilateral triangle by having pole vector may be obtained throughout the their lead electrodes formed perpendicular to cardiac cycle2 (Fig. 1). one another.3 Proper magnification of the loops is of the We have found the Frank and Grishman utmost importance so that every component systems to be the most convenient technically. may be adequately studied. Our vectorcardio- We are still experimenting with other lead graph gives magnification from 50 millivolts systems and are particularly interested in the per centimeter to 1 millivolt per centimeter, "balanced bipolar system" used by Lamb, and related to the oscilloscope input sensitivity. the McFee and Parungao system. Lambs sys- Many lead reference systems have been tem has a major advantage of obtaining large, devised to measure X, Y, and Z components. clear signals because of its high signal-to-noise Basically there are two types. One type of ratio. It also measures the vectors representing system is based on the Einthoven equilateral the atria more accurately than other available triangle and includes those devised by Milo- systems. The McFee and Parungao system vanovich, Jouve, Vastesaeger, and the "equi- supposedly has the advantage of eliminating lateral tetrahedron" system suggested by Wil- the inaccuracy or error in the location of an- son. The other consists of orthogonal lead terior and lateral thoracic electrodes. systems. These include Duchosal and Sulzers The components of the vectorcardiographic 496/72 ei I , i. ,,. Arl -agnAmeas ItitiligliallAtIfilli Mini Elwell 1111E,r5ItTgif Itegilial 4,.4.16,fa,,,Agt SPPRITHIP illkel$Mitall IMiklutlilltelll L,!lli,diffftitliON: WPM MX Nil Min ::, A 44, Ittifilallffinni Nei n Cate i AVM . 11,f,NutfmimitiN fflgill 111111tEglik , *atilbill. ,grimaggikrufArtvf RI Malin .rfftern ttIlliMilla AlE04414111P4111 Aolfiklhiellith:1410::Tairr ION ,01010e4M;firtilt41011/11 11814114411141111114.ALIR MR SOMBIJAREUtegt 4910E44-J111111111111011Mt 4 30110341111111fifilt,IMElk • ,41:04NeleSEIt red? filligliing TIP TM 1.10tgA. lPlinliiMP 1414 lite,,t 1P.,4, 4 ., • loop are the QRS, T, and P loops (Fig. 2, left). 3r,110P llitill4PlItO ' Ora; tio$ The Q loop (Fig. 2) corresponds to the re- gs sultant vectors produced by the activation of - 41044.,,r,§1MMICIO ' Yft00:1:4:MiritifAii the middle and lower third of the interven- 40441441! tricular septum belonging predominantly to the left septal, inferior, and right anterior * •.. septal masses. The R loop (Fig. 2) represents #4: .foiiiNgage imatmainon, the resultant vectors produced by the activa- NinfitittWillittkint tion of the free left ventricular wall. It con- raw la'cfAKIANKTOnef4f1 ormarmwhi sists of two segments : A—The initial or cen- ink famidifla trifugal limb (Fig. 2, left) is produced by the activation in the apical segment. This includes the anterior and lateral surfaces at the middle and lower regions. B—The final or centripetal segment corresponds to activations at the mid- -Avow.AA4 dle and upper thirds of the posterior, high somatim lateral, and posterolateral regions. At the 7.7.a junction of the initial and final portions of the f1004,60PIO5PE2ZOI irrOrliite QRS loop a vertex is noted (Fig. 2, left). This la P. is due to the activation in the lateral free left T.41: ventricular wall at its thickest region.4 The S loop (Fig. 2) is actually a portion of the centripetal segment of the QRS loop. It represents the activation within the basal por- tions of the heart. This includes the high pos- terior portions of the left ventricular wall, high portions of the right septal mass, and the free right ventricular wal1.4 The P loop (Fig. 2, left) reflects the activa- tion of the atria, and the T loop (Fig. 2, left) depicts the repolarization of the ventricles.4 In order to use the vectorcardiograph as a useful clinical instrument, one must under- stand the vectorcardiographic changes which occur when myocardial activity is altered. In 0 sY: . 444,4 this preliminary report, discussion will be sontomarf limited to the depolarization changes noted in 41,101110NOR an acute myocardial infarction. The repolari- zation abnormalities reflected by the T loop are not specific for myocardial infarction and therefore will not be mentioned. Necrotic tissue does not produce an action Fig. 6. Serial electrocardiograms of patient in Case 1. Journal AOA/vol. 66, January 1967 497/73 /RLL ,10.f“ R /AO y 1 \ ...a Frontal plane — 3 ‘/ I P Roc R Avg /4— 36 Horizontal plane A Fig. 7. Admission electrocardiogram of patient in Case 2. S current and therefore contributes little to the configuration of the vectorcardiograph loop.4 It is this absence of vectorial forces at the site P of necrosis that is responsible for the changes in the magnitude and configuration of normal loop morphology. Materials and methods Rt. sa6ittal plane A fully mobile panoramic vectorcardiograph was used (Fig. 3). This instrument not only Fig. 8. The vectorcardiogram of patient in Case 2 records the standard frontal, horizontal, and demonstrates an abnormally oriented Q loop, most sagittal planes, but any azimuth and elevation noticeable in the right sagittal plane where it is pro- longed upward and anteriorly.