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The vectorcardiographic QRSsÊ-loop findings in inferoposterior myocardial infarction
The vectorccwdiographic in inferoposterior
QRSsi-loop myocardial
findings
infarction
Thomas J. Walsh, M.D. Porfirio M. Tiongson, M.D. Elizabeth A. Stoddard, M.D. Edward Make, M.D. St. Louis, MO.
T
he purpose of this report is to describe the QRSsl?loop abnormalities observed in vectorcardiograms recorded with the Frank lead system in 153 cases of inferoposterior myocardial infarction. The terminology used in this paper to designate the various types of infarction is based solely upon the effective electrical location of the infarction.t-4 For example, an inferoposterior myocardial infarction is one whose effective electrical location is in the inferoposterior portion of the left ventricular wall. Since the infarcted myocardium is rendered electrically inert, the depolarization forces normally contributed by this region to the balance of forces which detertnine the mean instantaneous QRS spatial vectors are, in effect, subtracted frotn the electrical field of the heart (Fig. 1). It is much as though the infarction has given rise to new abnormal forces which are directed away frotn the electrical site of the infarction, and which produce the characteristic QRS abnormalities of infarction in the appropriate leads of the electrocardiogram. It is evident that a method of terminology such as this, based as it is upon changes in the balance of electrical forces produced by the heart, makes it possible to avoid for the most From
the Department vascular Laboratory, Received for publication
516
part the not infrequent discrepancies which have been noted in the past between the anatomic location and the electrical ntanifestations of a given type of myocardial infarction. In accordance with the terminology just described, it is possible to distinguish the following types of inferoposterior myocardial infarction: (1) diaphragmatic (inferior) infarction, (2) posterolateral myocardial infarction, (3) diaphragtnatic-posterolateral myocardial infarction, and (4) strictly posterior tnyocardial infarction. Material
and
methods
The cases selected to be included in this study series had to satisfy the following requirements: (1) There had to be clinical data indicative of arteriosclerotic and atherosclerotic heart disease with recent or past tnyocardial infarction; and (2) the conventional QRS criteria for the electrocardiographic diagnosis of recent or healed inferoposterior tnyocardial infarction had to be satisfied in each instance. These criteria are listed below. A. Diaphragmatic infarction: a Q wave in Lead III of 0.04-second duration with a depth exceeding 2.5 per cent of the atnplitude of the following R wave, if present;
of Medicine, Washington University Barnes Hospital, St. Louis, MO. Sept. 6. 1961.
School
of Medicine,
and
the Heart
Station
and
Cardio-
VCG QRSsl?loop
in inferoposterior
myocardial
infarction
517
A. NORMAL Left
Ventrick
‘Activation
wove front
I at
6. AFTER
0.02scc.0f Interval
QRS
sec.
of QRS
Interval
DIAPHRAGMATIC
at 0.02rec.of Interval
at 0.04
INFARCTION
QRS
at
0.04
L. Interval
of QRS
Fig. 1. The hypothesized mechanism of the QRS abnormalities in myocardial infarction. In this schematic figure the heart is shown in frontal view; the interventricular septum has been omitted for the purpose of simplification. In each part of this figure the resultant or mean instantaneous QRS vector (IZV) is the resultant of two component vectors. The efferent limb of the planar QRS loop, determined by the resultant or mean 0.02~second and mean 0.04-second instantaneous vectors, is represented by a solid curved line, and the dashed line which completes the planar loop corresponds to the afferent limb of the loop. A depicts the course of events during the initial 0.04-second of the ventricular activation process in the normal heart. B demonstrates the effects of diaphragmatic infarction on the resultant vectors and planar QRS loop. Note that the resultant vectors in this part of the figure are obtained by vector addition of the preinfarction resultant vectors and component vectors, equal in magnitude but opposite in direction to those normally produced by the infarcted wall of the left ventricle.
and a Q wave in Lead aVF satisfying either of the criteria of width and depth just described, preferably b0th.j B. Posterolateral myocardial infarction: an R wave in Lead Vr of 0.04-second or more duration and an R/S amplitude ratio in that lead equal to or exceeding 1; and a Q wave in Lead V6 with a width of 0.04 second or more and a depth exceeding 15 per cent of the total QRS amplitude in this lead.4 (This latter criterion was considered to be optional and was not satisfied in all
electrocardiograms in the cases of posterolateral myocardial infarction). C. Diaphragmatic-posterolateral infarction: the combined criteria listed above for the preceding two types of inferoposterior myocardial infarction.4 D. Strictly posterior myocardial infarction: the presence in Leads Vln or Vr of any of the following QRS configurationsrSR’, a notched or slurred R, or an RS configuration with an R/S amplitude ratio equal to or greater than l.d
518
Walsh,
247% Heart J. April. 1963
Tiongson, Stoddard, and Make
Table I. The extreme, usual,* and average orientations of the mean O.OZ-second, maximal mean,t and terminal meant instantaneous vectors of the QRSs& loop in 100 normal vectorcardiograms recorded with the Frank lead system Horizontal
0"
Mean 0.02-second instantaneous QRS vector
+60” +‘U1o”
Masimal mean instantaneous QRS vector
-10” +Fo”
Terminal mean instantaneous QRS vector
-120” to -60”
-25” +Fo”
+65” to t11.5”
- 150” to 0”
+110” to - 150”
+5”
§
%
+.W +90°
5
to +130°
+20° to +50°
+90° to -110”
-90” to +30°
+15” +3.Y
10 +55” +20° to -20”
I
*Kange of variation in orientation in 85 per cent of the vectorcardiograms. tcorresponding approximately to the mean 0.04~second instantaneous QRS vector. tCorresponding approximately to the mean 0.06~second instantaneous QRS vector. $Because of the extremely wide range of variation in orientation of the terminal mean instantaneous QRS vector, the average orientation of this vector is not listed because it would have little significance. Note: The order in which the range of variation in orientation of a given vector is given in degrees is such that the range in orientation is meant to be read in a clockwise direction in any given plane of projection.
Table II. Orientation of the mean 0.02-second and maximal mean instantaneous vectors of the QRSs2 loop in diaphragmatic myocardial infarction
Mean 0.02~second instantaneous QRS vector Maximal mean instantaneous QRS vector
I
Horizontal
~ Usual
/ Average
-10
/ Extreme1 Usual - 20”
+55” +?o”
+%o”
- 50”
- 100” -40”
+Fo”
+t200”
All of the vectorcardiograms included in this study series were recorded with the corrected lead system of Frank.‘j The left sagittal projections of vectorcardiograms obtained with the Frank lead system have been transposed into their mirror-image “right sagittal” counterparts. Reference frames for each planar projection of the vectorcardiogram are depicted in Fig. 2. It should be noted that, when the range of variation in orientation of a vector in a given projection of the vectorcardio-
Frontal
Right sagittal
I
1 Average
! 1 Extreme/ Usual
- 120” to -10”
-70”
0” to -180”
- 130” to 0”
+lloO to - 150”
+80” to - 100”
- 10”
+170°
/ Average
-80”
i
Extreme f5” to - 150” - 100”
f15” +‘6”o”
gram is cited, the range in degrees is expressed so as to read in a clockwise direction in the appropriate reference frame. In evaluating the QRSsl? loops in the vectorcardiograms in inferoposterior myocardial infarction, the authors preferred to adopt a semiqualitative approach rather than a strictly quantitative approach since this seemed to offer certain practical advantages and at the same time did not seem to present any significant handicap in the interpreting of these vectorcardio-
VCG QRSsl? loop in inferoposterior
myocardial
infarction
519
(1) the orientations of the mean 0.02second and maximal mean instantaneous vectors of the planar QRS loops; (2) the direction of inscription of the planar QRS loops; and (3) the presence or absence of an abnormal concavity in the efferent or afferent limbs of the planar QRS loops. Results
Normal
control vectorcard iograms (100
cases). The specific findings in the normal control vectorcardiograms which are represented in Table I and Fig. 3 can be summarized as follows: (1) Normally, the initial deflection of the QRSsl? loop was written to the right, anteriorly, and either inferiorly or superiorly, and, in a given planar projection, generally had the same direction of inscription as the QRS loop itself. (2) The mean 0.02-second instantaneous vector of the QRSsl? loop generally occupied the left, anterior, and inferior octant. (3) The maximal mean instantaneous vector of the QRSsl? loop was normall? oriented inferiorly, to the left, and either slightly anteriorly or slightly posteriorly. (4) The horizontal QRS loop of the normal vectorcardiogram was invariably inscribed counterclockwise, and the right sagittal loop was invariably inscribed clockwise. The frontal QRS loop in general tended to be inscribed counter-
Fig. 2. Planar reference frames for the vectorcardiographic QRSsl? loop, as if viewed from the right, anterior, and slightly superior. Note that the right sagittal plane, rather than the left sagittal, is utilized in this study.
grams. Thus, no effort was made to measure accurately the magnitude of the vectors, although this was assessed in a qualitative way. In the main, the following features of the planar QRS loops of the vectorcardiograms in cases of inferoposterior myocardial infarction and of a control group of vectorcardiograms were studied :
Table III. Orientation of the mean O.OZ-second, maximal, and terminal mean instantancom vectors qf the QRSs,$ loop in posterolateral myocardial infarction ~ Horizontal
l:sual ~
+ 140” to + 100”
RIaximal mean instantaneous QRS vector
0”
*‘IX= extreme range
j Extwm
1
Vsual
saziftal
Frohzl
~
/ ,i,,gl,,,,,,,Ii,,il
1 Ertreme
I
Mean 0.02-second instantaneous QRS vector
Terminal mean instantaneous QRS vector
Average
Right
+ 110”
,‘Yoo”
-20” +‘6”o”
+so” to - 140”
- 10”
0”
$10” +?o”
+?o”
-10”
0” to - 160”
+50 +%o”
- 150 -T&o
-20”
+110”
$65” -?40°
*
-6”,o
-&
+2s0
0” to - 120”
t
*
+‘6”o”
+150° t
f10 180”
180” t
*
of variation in orientation of the terminal instantaneous vector of the QRS& of the wide limits of variation. of the extremely wide range of variation in orientation of the terminal mean instantaneous of this vector is not listed because it would have little significance.
+?o”
loop
is nnt presented
in this
instance
the average
orienta-
because
tHecause tion
QRS
vector.
520
Am. Heart J. Aflril, 1962
Walsh, Tiongson, Stoddard, and Massie
NORMAL
F
RS
H
DMI ( 72 Cos
~Usual orientation m Usual orientation Usual orientation -
of meon
0.02
of moximal
second instontoneous mean instantanecus
of mean 0.06
Average orientations loops, as determined
secand (terminal
vector
vector
of planar ORS loop.
of planar
1 instantoneous
QRS loop.
vector
of planar ORS loop
of the corresponding mean instantaneous vectors of planar from all VCGs in the specific infarction group in question.
ORS
Fig. 3. The usual range and average orientations of the mean 0.02-second and maximal mean instantaneous vectors of the QRS& loop in normal vectorcardiograms and vectorcardiograms of diaphragmatic myocardial infarction (DMI). The usual range and average orientations of the mean 0.06~second instantaneous vector of the QRS& loop are shown only for the normal control group of vectorcardiograms. H: Horizontal projection. RS: Right sagittal projection. F: Frontal projection.
clockwise the more nearly its maximal vector paralleled the 0 degree axis, and to be inscribed clockwise the more nearly its maximal vector approached the f90 degree axis. (5) The efferent or outgoing limb of the QRSsl? loop was usually outwardly convex, whereas the afferent limb was less consistently outwardly bowed. Diaphragmatic myocardial infarction (72 cases). Infarction of the diaphragmatic or inferior wall of the left ventricle leads to a predominance of electrical forces directed superiorly, and these unbalanced forces are present during the first 0.04-second of ventricular activation. Thus, as one might anticipate, the abnormal, superiorly directed QRS forces in diaphragmatic infarction affect the vectorcardiographic QRSsl?
loop principally in its right sagittal and frontal projections. The QRSsl?-loop findings observed in the vectorcardiograms in cases of diaphragmatic myocardial infarction were as follows (Table II and Figs. 3 and 4) : (1) The mean 0.02second instantaneous vector of the QRSsE loop was deviated superiorly; its average orientation in the horizontal projection was +55 degrees, in the right sagittal projection, - 70 degrees (normal + 15 degrees), and in the frontal projection, -80 degrees (normal +30 degrees). Although there was some overlapping of the extreme ranges of variation in orientation of the mean 0.02second instantaneous QRS vectors in the right sagittal and frontal projections of normal vectorcardiograms and of those
I’CG QRSs,!? loop in inferoposterior
which showed diaphragmatic myocardial infarction, there was no overlapping of the usual range of variation in orientation of this vector.* (2) The mean maximal instantaneous QRS vector tended to oca more posterior and less inferior CLl]Qorientation in diaphragmatic myocardial infarction than normally, but this feature was not found to be useful diagnostically. The average orientation of the mean maximal instantaneous vector was - 40 degrees in the horizontal projection (nor*“Usual“ range cases.
of orientation
is the range
in 85 per
cent
of the
myocardial
infarction
521
ma1 +5 degrees), + 170 degrees in the right sagittal projection (normal f90 degrees), and +15 degrees in the frontal projection (normal +35 degrees). There was significant overlapping of the extreme and, to a lesser extent, the usual ranges of orientation of the mean maximal instantaneous QRS vector in the vectorcardiograms of diaphragmatic myocardial infarction and in normal vectorcardiogranis. (3) In almost one half of the vectorcardiograms of patients with diaphragmatic infarction there was some abnormality in the direction of inscription of the right sagittnl projec-
Fig. 3. Electrocardiographic and vectorcardiographic findings in a patient \vith a recent diaphragmatic myocardial infarction. Note the large superiorly directed early deflection of the right sagittal QRS loop and the reversed inscription of the frontal QRS loop. These findings are indicative of diaphragmatic infarction, whereas the superiorly directed TSR loop is compatible with diaphragmatic ischemin. There is no S-T vector.
522
Walsh, Tiongson,
z4m. Heart I. Afiril, 1962
Stoddard, and Lassie
-35.
-25’
SPMI
mltsuol m
-
orientation
of mean
Usual
orientation
of moximol
Usual
orientation
of mean
Average orlentotlons loops, OS determined
F
RS
H 0.02
second mean
0.06
mstantaneous
instantaneous
second
vector vector
(terminal
of plonor
of planar
1 instantoneous
of the corresponding meon lnstantoneous from all VCGs in the specific infarction
ORS loop. QRS loop.
vector
of plonor
vectors of planar group in question.
QRS loop ORS
Fig. 5. The usual range and average orientations of the mean 0.02-second, maximal mean, and mean 0.06-second instantaneous vectors of the QRSsl? loop in vectorcardiograms of posterolateral (PLMI), diaphragmatic-posterolateral (D-PLMI), and strictly posterior myocardial infarction (SPMI).
tion of the QRSsI? loop. Thus, in about one sixth of the cases the loop was inscribed entirely counterclockwise; in over 25 per cent of the cases the right sagittal loop was inscribed counterclockwise/clockwise. In almost 20 per cent of the cases the proximal portion of the loop was inscribed clockwise, and the distal portion was inscribed counterclockwise. In the remaining third of the vectorcardiograms the right sagittal loop was inscribed entirely clockwise. In over 50 per cent of the vectorcardiograms of diaphragmatic infarction the frontal QRS loop was inin scribed entirely clockwise, whereas
almost an additional one third of the cases the proximal portion of the frontal loop was inscribed clockwise and the distal was inscribed counterclockwise. portion In the other 7 cases out of the total group with counterclockwise-inscribed frontal loops the efferent limb of the loop was invariably bowed superiorly, usually with clockwise inscription of its initial deflection.
Posterolateral myocardiab infarction
(22
cases). Infarction which involves the posterolateral wall of the left ventricle is characterized by unbalanced QRS forces which are directed anteriorly and to the
VCG QRSsl? loop in inferoposterior
right and are responsible for the following changes in the QRS& loop (Table III and Figs. 5 and 6): (1) The mean 0.02second instantaneous QRS vector was observed to be displaced to the right and anteriorly; its average orientation was +llO degrees in the horizontal projection (normal +60 degrees), and 180 degrees in the frontal projection (normal +30 degrees). Again, there was slight overlapping of the extreme ranges of variation of orientation of the mean 0.02-second instantaneous vectors in the vectorcardiograms of posterolateral myocardial infarction and in the corresponding normal vectorcardiograms, but this was of even less significant degree than in the vectorcardiograms of diaphragmatic infarction. Moreover, the relative magnitude of the anterior component of the mean 0.02-second instantaneous vector in posterolateral myocardial infarction seemed to be greater than in the normal control group of vectorcardiograms.
myocardial
infarction
523
(2) There was significant anterior and medial displacement of the maximal mean instantaneous QRS vector in posterolateral myocardial infarction; the average orientation of this vector in the horizontal projection was +50 degrees (normal +5 degrees), and in the frontal projection, +85 degrees (normal +35 degrees). In only 2 of the 22 cases of posterolateral myocardial infarction was the horizontal QRS loop (or its proximal portion) inscribed clockwise. In 3 of the vectorcardiograms the proximal part of the horizontal QRS loop was inscribed counterclockwise, and the distal portion was inscribed clockwise. It is of interest that in 4 of the 22 vectorcardiograms the right sagittal QRS loop (or its proximal portion) was inscribed counterclockwise. Diaphragmatic - posterolaterab Tyocardial infarction (13 cases). The QRSsE loop in vectorcardiograms of cases of combined diaphragmatic - posterolateral myocardial
Fig. 6. The electrocardiogram and vectorcardiogram in recent posterolateral myocardial infarction. The mean 0.02-second instantaneous vector of the horizontal QRS loop is oriented at about +130 degrees in the horizontal reference frame, and the long axis or maximal mean instantaneous QRS vector is displaced markedly anteriorly and medially in the horizontal plane. The large rightwardly and anteriorly directed Tsl? loop in the horizontal plane is compatible with posterolateral myocardial ischemia.
524
Walsh, Tiongson,
Am. Heart J. 1962 A#&,
Stoddard, and Alassie
Fig. 7. Electrocardiographic and vectorcardiographic findings in old diaphragmatic-posterolateral myocardial infarction. The characteristic findings of each component type of infarction are quite distim-tive and easily recognizable.
infarction showed the features distinctive of each of the two cotnponettt tl-pes of infarction (Table IV and Figs. 5 and 7). 1. The mean 0.02-second instantaneous QRS vector was directed, on the average, along the +115 degree axis in the horizontal projection, along the -35 degree axis in the right sagittal projection, and along the -125 degree axis in the frontal projection. 2. The average orientations of the maximal mean instantaneous QRS vectors of the planar QRS loops were +45, -90, and +120 degrees, in the horizontal, right sagittal, and frontal projections of the vectorcardiogram, respectively. 3. Itt 5 of the 13 vectorcardiograms the horizontal QRS loop was inscribed entirel!, clockwise; in 3 of the vectorcardiograms the right sagittal projection (or its proximal portion) was inscribed counterclockwise, and in 11 of the 13 vectorcardiogratns the frontal QRS loop (or its proximal portion) was inscribed clockwise.
4. In general, it can be said that the single niost characteristic feature of the QRSsl? loop in combined diaphragmaticposterolateral mlrocardial infarction is the presence of an abnormally large early deflection of the loop to the right, anteriorly, and superiorly.
Strictly postrrior j-M case.s).
m,yocardid znfarction
1. The niean 0.02-second instantaneous vector of the QRSsi? loop was not significantl\displaced in niost of the vectorcardiograms; its average orientation was +50 degrees in the horizontal projection, + 15 degrees in the right sagittal projection, and +30 degrees in the frontal projection (Table 1’ and Figs. 5 and 8). 2. Ott the other hand, the maximal nteatt instantaneous QRS vector frequently tended to be oriented slightly tnore anteriorly than in nornial vectorcardiograms. The average orientation in the horizontal projection was observed to be +20 degrees, itt the right sngittal projection, f70
VCG QRS&
loop in inferoposterior
degrees, and in the frontal projection, $20 degrees. 3. Even more striking in the frequency of its presence was a terminal deflection of the QRSsl? loop, the maximum instantaneous vector of which was oriented at about +175 degrees in the horizontal projection (normal, approximately - 80 degrees), at about - 70 degrees in the right sagittal projection (normal - 170 degrees), and at 180 degrees in the frontal projection (normal, about -60 degrees). 4. As a general rule, the horizontal QRS loop in strictly posterior myocardial infarction showed, at the least, anterior bowing of its afferent limb and a right posterior terminal deflection. 5. Three points which should be stressed in regard to the QRSsl? loop in strictly posterior infarction are listed below. A. Strictly posterior infarction is characterized primarily by a change in the second half of the QRSsl? loop. Inasmuch as the posterobasal wall of the left ventricle normally is activated quite late in the QRS interval, it is possible that infarction of this region of the heart has its electrical
myocardiab infarction
effects deferred to a correspondingly later period of the ventricular activation sequence. On the other hand, an intraventricular conduction defect produced by the infarction cannot be excluded as an alternative explanation for the delayed abnormalities of the QRSsl? loop in this type of infarction. B. Although not infrequently the long axis of the QRSsl? loop (i.e., the maximal mean instantaneous or mean 0.04-second vector) may be rotated anterior to its normal orientation, the main diagnostic change consists, more often than not, of one or a combination of the following findings: anterior bowing of the afferent limb of the loop; a right posterior terminal deflection; or a partial or complete change in direction of inscription of the QRSsi? loop in the horizontal and/or right sagittal projection. C. Approximately 50 per cent of the horizontal QRS loops (14 of the 46 cases of strictl\posterior infarction) exhibited either a clockwise or clockwise/counterclockwise direction of inscription, whereas an additional 20 per cent of the cases displayed horizontal QRS loops with a coun-
--. Harizontal
I
Right
lx
UI
525
Sapittal aVR
Frontal aVL
aVF
Fig. 8. The electrocardiogram and vectorcardiogram in a recent strictly posterior myorardial infarction. Note that the main QRS&-loop abnormalities of diagnostic importance involve the afferent limb and terminal portion of the loop. Thus, there is anterior displacement of the afferent limb of the horizontal QRS loop and a clockwise-inscribed terminal deflection of the loop to the right, posteriorly, and superiorly.
526
Walsh, Tiongson, Stoddard, and A4assie
Table IV. Orientation of the mean O.OZ-second, maximal, and terminal mean instantaneous vectors of the QRS& loop in diaphragmatic-posterolateral myocardial infarction Horizontal
R&hi - -----
lima1 Mean 0.02-second instantaneous QRS vector
+90°
Maximal mean instantaneous QRS vector
+loO
Terminal mean instantaneous QRS vector
-170” to - 60”
II Aoevage
Extreme
Lszlal
+90°
-60”
+‘P,oO
-t;Oo
-30”
j-50”
I_--
/ Average
+lls” +?30°
Frontal
sagittal __-
1 Extreme
-3.5”
-t45”
-160”
+40°
- 140°
+:020°
t
:eoO
-‘500~
*
+90” to -120”
Horizontal
Maximal mean instantaneous QRS vector Terminal mean instantaneous QRS yector
*The
extreme range of variation limits of its variation.
.4verage
$20”
+5”
0”
,‘Yoo”
+20°
-10”
+20°
t
+To”
+3s0
loop
is not presented QRS vector,
-6”oo
in orientation
sagiftal
just reported in this study indicate that
- 30” f30”
:9”Y
$-?O”
-5” to -150”
$10”
+to” - 20” +20°
+“4”o”
+‘6”o”
+60” -70”
instantaneous
orienta-
Frontal
-10”
*
-6”oo
+tO”
of the terminal
the average
of the
/ A wrag$ZL~Z~(,,i,;.,I,.,
+6”o”
*
because
mean instantaneous
I
+ 150” +17s0
*
f l”oo”
+70°
+?o”
+‘690°
*
-40°
+20°
- 150”
+‘6”o”
+ls”
+“9”o”
$0
-40” t
-10”
+50°
terclockwise/clockwise inscription. In the right sagittal projection, the QRS loop in 8 of the 46 cases had an entirely clockwise inscription, and 7 cases showed a clockwise/counterclockwise direction of inscription. The observations vectorcardiographic
l:sual
-170”
-2.5” -‘;po~
Right
Extreme
/ Edreme
- 125”
$)o
of the mean O.OZ-second, maximal, and terminal IGOP in strictly posterior myocardial infarction
l~sual
1 Average
- 90”
extreme range of variation in orientation of the terminal instantaneous vector of the QRS& wide limits of its variation. tBecause of the extremely wide range of variation in orientation of the terminal mean instantaneous tion of this vector is not listed because it would have little significance.
Mean 0.02-second instantaneous QRS vector
L’sual
- 70” to -20”
*The
Table V. Orientation vectors qf the QRSsfi
j
vector
of the QRSsfi
loop
is omitted
180”
because
*
of the wide
the various types of inferoposterior infarction are characterized by deviation of certain mean instantaneous vectors of the QRS& loop away from the effective electrical site of the infarction. As one might anticipate, the mean instantaneous vectors of the QRSsl? loop which are affected by an infarction are those which appear during that portion of the QRS interval when the infarcted heart muscle normally undergoes
Volume .Sumber
63 4
VCG QRSsI? loop in inferoposterior
activation. Moreover, the postinfarction mean instantaneous vectors of the QRSsI? loop generally acquire not only an abnormal direction but also an increased magnitude as well. The mean 0.02-second instantaneous vector of the QRSsI? loop is the vector which is primarily affected in the various types of inferoposterior infarction, whereas the maximal or mean 0.04-second vector less frequently exhibits diagnostic changes. The principal exception to the previous statement is the case of strictly posterior myocardial infarction, which is characterized vectorcardiographically by abnormalities of the later portions of the QRSsl? loop. Two alternative explanations for this finding were cited earlier in this paper. Summary
1. The QRS&-loop findings have been described in vectorcardiograms recorded with the Frank lead system from 100 subjects without clinically detectable heart disease and from 153 patients with inferoposterior myocardial infarction. 2. In the vectorcardiograms of cases of diaphragmatic (inferior), posterolateral, and diaphragmatic-posterolateral infarction, the abnormality most consistently
myocardial
,infarction
527
observed was deviation of the mean 0.02second instantaneous vector, and, to a lesser extent, the maximal or mean 0.04second instantaneous vector, of the planar QRS loops away from the effective electrical site of the infarction. 3. In casesof strictly posterior infarction the QRSsE loop displayed an anterior deviation of the maximal or mean 0.04second and subsequent instantaneous QRS vectors. REFERENCES 1. Grant, R. P., and Murray, R. H.: QRS complex deformity of myocardial infarction in the human subject, Am. J. Med. 17587, 1954. 2. Gardberg, N., and Levy, L.: I and II-The QRS complex of the electrocardiogram in myocardial infarction, with remarks on methods of recording, AK HEART J. 51501 and 654, 1956. 3. Grishman, A., and Scherlis, L.: Spatial vectorcardiography, Philadelphia, 1952, W. B. Saunders Company. E., and Walsh, T. J.: Clinical vector4. Massie, cardiography and electrocardiography, Chicago, 1960, The Year Book Publishers, Inc. 5. Goldberger, E.: Unipolar lead electrocardiography and \-ectorcardiography, ed. 3, Philadelahia. 19.53. Lea & Febieer. 6. F&k, E.: .qln accurat: clinically practical system for spatial vectorcardiography, Circulation 13:736, 1956.
QRSsi-loop myocardial
findings
infarction
Thomas J. Walsh, M.D. Porfirio M. Tiongson, M.D. Elizabeth A. Stoddard, M.D. Edward Make, M.D. St. Louis, MO.
T
he purpose of this report is to describe the QRSsl?loop abnormalities observed in vectorcardiograms recorded with the Frank lead system in 153 cases of inferoposterior myocardial infarction. The terminology used in this paper to designate the various types of infarction is based solely upon the effective electrical location of the infarction.t-4 For example, an inferoposterior myocardial infarction is one whose effective electrical location is in the inferoposterior portion of the left ventricular wall. Since the infarcted myocardium is rendered electrically inert, the depolarization forces normally contributed by this region to the balance of forces which detertnine the mean instantaneous QRS spatial vectors are, in effect, subtracted frotn the electrical field of the heart (Fig. 1). It is much as though the infarction has given rise to new abnormal forces which are directed away frotn the electrical site of the infarction, and which produce the characteristic QRS abnormalities of infarction in the appropriate leads of the electrocardiogram. It is evident that a method of terminology such as this, based as it is upon changes in the balance of electrical forces produced by the heart, makes it possible to avoid for the most From
the Department vascular Laboratory, Received for publication
516
part the not infrequent discrepancies which have been noted in the past between the anatomic location and the electrical ntanifestations of a given type of myocardial infarction. In accordance with the terminology just described, it is possible to distinguish the following types of inferoposterior myocardial infarction: (1) diaphragmatic (inferior) infarction, (2) posterolateral myocardial infarction, (3) diaphragtnatic-posterolateral myocardial infarction, and (4) strictly posterior tnyocardial infarction. Material
and
methods
The cases selected to be included in this study series had to satisfy the following requirements: (1) There had to be clinical data indicative of arteriosclerotic and atherosclerotic heart disease with recent or past tnyocardial infarction; and (2) the conventional QRS criteria for the electrocardiographic diagnosis of recent or healed inferoposterior tnyocardial infarction had to be satisfied in each instance. These criteria are listed below. A. Diaphragmatic infarction: a Q wave in Lead III of 0.04-second duration with a depth exceeding 2.5 per cent of the atnplitude of the following R wave, if present;
of Medicine, Washington University Barnes Hospital, St. Louis, MO. Sept. 6. 1961.
School
of Medicine,
and
the Heart
Station
and
Cardio-
VCG QRSsl?loop
in inferoposterior
myocardial
infarction
517
A. NORMAL Left
Ventrick
‘Activation
wove front
I at
6. AFTER
0.02scc.0f Interval
QRS
sec.
of QRS
Interval
DIAPHRAGMATIC
at 0.02rec.of Interval
at 0.04
INFARCTION
QRS
at
0.04
L. Interval
of QRS
Fig. 1. The hypothesized mechanism of the QRS abnormalities in myocardial infarction. In this schematic figure the heart is shown in frontal view; the interventricular septum has been omitted for the purpose of simplification. In each part of this figure the resultant or mean instantaneous QRS vector (IZV) is the resultant of two component vectors. The efferent limb of the planar QRS loop, determined by the resultant or mean 0.02~second and mean 0.04-second instantaneous vectors, is represented by a solid curved line, and the dashed line which completes the planar loop corresponds to the afferent limb of the loop. A depicts the course of events during the initial 0.04-second of the ventricular activation process in the normal heart. B demonstrates the effects of diaphragmatic infarction on the resultant vectors and planar QRS loop. Note that the resultant vectors in this part of the figure are obtained by vector addition of the preinfarction resultant vectors and component vectors, equal in magnitude but opposite in direction to those normally produced by the infarcted wall of the left ventricle.
and a Q wave in Lead aVF satisfying either of the criteria of width and depth just described, preferably b0th.j B. Posterolateral myocardial infarction: an R wave in Lead Vr of 0.04-second or more duration and an R/S amplitude ratio in that lead equal to or exceeding 1; and a Q wave in Lead V6 with a width of 0.04 second or more and a depth exceeding 15 per cent of the total QRS amplitude in this lead.4 (This latter criterion was considered to be optional and was not satisfied in all
electrocardiograms in the cases of posterolateral myocardial infarction). C. Diaphragmatic-posterolateral infarction: the combined criteria listed above for the preceding two types of inferoposterior myocardial infarction.4 D. Strictly posterior myocardial infarction: the presence in Leads Vln or Vr of any of the following QRS configurationsrSR’, a notched or slurred R, or an RS configuration with an R/S amplitude ratio equal to or greater than l.d
518
Walsh,
247% Heart J. April. 1963
Tiongson, Stoddard, and Make
Table I. The extreme, usual,* and average orientations of the mean O.OZ-second, maximal mean,t and terminal meant instantaneous vectors of the QRSs& loop in 100 normal vectorcardiograms recorded with the Frank lead system Horizontal
0"
Mean 0.02-second instantaneous QRS vector
+60” +‘U1o”
Masimal mean instantaneous QRS vector
-10” +Fo”
Terminal mean instantaneous QRS vector
-120” to -60”
-25” +Fo”
+65” to t11.5”
- 150” to 0”
+110” to - 150”
+5”
§
%
+.W +90°
5
to +130°
+20° to +50°
+90° to -110”
-90” to +30°
+15” +3.Y
10 +55” +20° to -20”
I
*Kange of variation in orientation in 85 per cent of the vectorcardiograms. tcorresponding approximately to the mean 0.04~second instantaneous QRS vector. tCorresponding approximately to the mean 0.06~second instantaneous QRS vector. $Because of the extremely wide range of variation in orientation of the terminal mean instantaneous QRS vector, the average orientation of this vector is not listed because it would have little significance. Note: The order in which the range of variation in orientation of a given vector is given in degrees is such that the range in orientation is meant to be read in a clockwise direction in any given plane of projection.
Table II. Orientation of the mean 0.02-second and maximal mean instantaneous vectors of the QRSs2 loop in diaphragmatic myocardial infarction
Mean 0.02~second instantaneous QRS vector Maximal mean instantaneous QRS vector
I
Horizontal
~ Usual
/ Average
-10
/ Extreme1 Usual - 20”
+55” +?o”
+%o”
- 50”
- 100” -40”
+Fo”
+t200”
All of the vectorcardiograms included in this study series were recorded with the corrected lead system of Frank.‘j The left sagittal projections of vectorcardiograms obtained with the Frank lead system have been transposed into their mirror-image “right sagittal” counterparts. Reference frames for each planar projection of the vectorcardiogram are depicted in Fig. 2. It should be noted that, when the range of variation in orientation of a vector in a given projection of the vectorcardio-
Frontal
Right sagittal
I
1 Average
! 1 Extreme/ Usual
- 120” to -10”
-70”
0” to -180”
- 130” to 0”
+lloO to - 150”
+80” to - 100”
- 10”
+170°
/ Average
-80”
i
Extreme f5” to - 150” - 100”
f15” +‘6”o”
gram is cited, the range in degrees is expressed so as to read in a clockwise direction in the appropriate reference frame. In evaluating the QRSsl? loops in the vectorcardiograms in inferoposterior myocardial infarction, the authors preferred to adopt a semiqualitative approach rather than a strictly quantitative approach since this seemed to offer certain practical advantages and at the same time did not seem to present any significant handicap in the interpreting of these vectorcardio-
VCG QRSsl? loop in inferoposterior
myocardial
infarction
519
(1) the orientations of the mean 0.02second and maximal mean instantaneous vectors of the planar QRS loops; (2) the direction of inscription of the planar QRS loops; and (3) the presence or absence of an abnormal concavity in the efferent or afferent limbs of the planar QRS loops. Results
Normal
control vectorcard iograms (100
cases). The specific findings in the normal control vectorcardiograms which are represented in Table I and Fig. 3 can be summarized as follows: (1) Normally, the initial deflection of the QRSsl? loop was written to the right, anteriorly, and either inferiorly or superiorly, and, in a given planar projection, generally had the same direction of inscription as the QRS loop itself. (2) The mean 0.02-second instantaneous vector of the QRSsl? loop generally occupied the left, anterior, and inferior octant. (3) The maximal mean instantaneous vector of the QRSsl? loop was normall? oriented inferiorly, to the left, and either slightly anteriorly or slightly posteriorly. (4) The horizontal QRS loop of the normal vectorcardiogram was invariably inscribed counterclockwise, and the right sagittal loop was invariably inscribed clockwise. The frontal QRS loop in general tended to be inscribed counter-
Fig. 2. Planar reference frames for the vectorcardiographic QRSsl? loop, as if viewed from the right, anterior, and slightly superior. Note that the right sagittal plane, rather than the left sagittal, is utilized in this study.
grams. Thus, no effort was made to measure accurately the magnitude of the vectors, although this was assessed in a qualitative way. In the main, the following features of the planar QRS loops of the vectorcardiograms in cases of inferoposterior myocardial infarction and of a control group of vectorcardiograms were studied :
Table III. Orientation of the mean O.OZ-second, maximal, and terminal mean instantancom vectors qf the QRSs,$ loop in posterolateral myocardial infarction ~ Horizontal
l:sual ~
+ 140” to + 100”
RIaximal mean instantaneous QRS vector
0”
*‘IX= extreme range
j Extwm
1
Vsual
saziftal
Frohzl
~
/ ,i,,gl,,,,,,,Ii,,il
1 Ertreme
I
Mean 0.02-second instantaneous QRS vector
Terminal mean instantaneous QRS vector
Average
Right
+ 110”
,‘Yoo”
-20” +‘6”o”
+so” to - 140”
- 10”
0”
$10” +?o”
+?o”
-10”
0” to - 160”
+50 +%o”
- 150 -T&o
-20”
+110”
$65” -?40°
*
-6”,o
-&
+2s0
0” to - 120”
t
*
+‘6”o”
+150° t
f10 180”
180” t
*
of variation in orientation of the terminal instantaneous vector of the QRS& of the wide limits of variation. of the extremely wide range of variation in orientation of the terminal mean instantaneous of this vector is not listed because it would have little significance.
+?o”
loop
is nnt presented
in this
instance
the average
orienta-
because
tHecause tion
QRS
vector.
520
Am. Heart J. Aflril, 1962
Walsh, Tiongson, Stoddard, and Massie
NORMAL
F
RS
H
DMI ( 72 Cos
~Usual orientation m Usual orientation Usual orientation -
of meon
0.02
of moximal
second instontoneous mean instantanecus
of mean 0.06
Average orientations loops, as determined
secand (terminal
vector
vector
of planar ORS loop.
of planar
1 instantoneous
QRS loop.
vector
of planar ORS loop
of the corresponding mean instantaneous vectors of planar from all VCGs in the specific infarction group in question.
ORS
Fig. 3. The usual range and average orientations of the mean 0.02-second and maximal mean instantaneous vectors of the QRS& loop in normal vectorcardiograms and vectorcardiograms of diaphragmatic myocardial infarction (DMI). The usual range and average orientations of the mean 0.06~second instantaneous vector of the QRS& loop are shown only for the normal control group of vectorcardiograms. H: Horizontal projection. RS: Right sagittal projection. F: Frontal projection.
clockwise the more nearly its maximal vector paralleled the 0 degree axis, and to be inscribed clockwise the more nearly its maximal vector approached the f90 degree axis. (5) The efferent or outgoing limb of the QRSsl? loop was usually outwardly convex, whereas the afferent limb was less consistently outwardly bowed. Diaphragmatic myocardial infarction (72 cases). Infarction of the diaphragmatic or inferior wall of the left ventricle leads to a predominance of electrical forces directed superiorly, and these unbalanced forces are present during the first 0.04-second of ventricular activation. Thus, as one might anticipate, the abnormal, superiorly directed QRS forces in diaphragmatic infarction affect the vectorcardiographic QRSsl?
loop principally in its right sagittal and frontal projections. The QRSsl?-loop findings observed in the vectorcardiograms in cases of diaphragmatic myocardial infarction were as follows (Table II and Figs. 3 and 4) : (1) The mean 0.02second instantaneous vector of the QRSsE loop was deviated superiorly; its average orientation in the horizontal projection was +55 degrees, in the right sagittal projection, - 70 degrees (normal + 15 degrees), and in the frontal projection, -80 degrees (normal +30 degrees). Although there was some overlapping of the extreme ranges of variation in orientation of the mean 0.02second instantaneous QRS vectors in the right sagittal and frontal projections of normal vectorcardiograms and of those
I’CG QRSs,!? loop in inferoposterior
which showed diaphragmatic myocardial infarction, there was no overlapping of the usual range of variation in orientation of this vector.* (2) The mean maximal instantaneous QRS vector tended to oca more posterior and less inferior CLl]Qorientation in diaphragmatic myocardial infarction than normally, but this feature was not found to be useful diagnostically. The average orientation of the mean maximal instantaneous vector was - 40 degrees in the horizontal projection (nor*“Usual“ range cases.
of orientation
is the range
in 85 per
cent
of the
myocardial
infarction
521
ma1 +5 degrees), + 170 degrees in the right sagittal projection (normal f90 degrees), and +15 degrees in the frontal projection (normal +35 degrees). There was significant overlapping of the extreme and, to a lesser extent, the usual ranges of orientation of the mean maximal instantaneous QRS vector in the vectorcardiograms of diaphragmatic myocardial infarction and in normal vectorcardiogranis. (3) In almost one half of the vectorcardiograms of patients with diaphragmatic infarction there was some abnormality in the direction of inscription of the right sagittnl projec-
Fig. 3. Electrocardiographic and vectorcardiographic findings in a patient \vith a recent diaphragmatic myocardial infarction. Note the large superiorly directed early deflection of the right sagittal QRS loop and the reversed inscription of the frontal QRS loop. These findings are indicative of diaphragmatic infarction, whereas the superiorly directed TSR loop is compatible with diaphragmatic ischemin. There is no S-T vector.
522
Walsh, Tiongson,
z4m. Heart I. Afiril, 1962
Stoddard, and Lassie
-35.
-25’
SPMI
mltsuol m
-
orientation
of mean
Usual
orientation
of moximol
Usual
orientation
of mean
Average orlentotlons loops, OS determined
F
RS
H 0.02
second mean
0.06
mstantaneous
instantaneous
second
vector vector
(terminal
of plonor
of planar
1 instantoneous
of the corresponding meon lnstantoneous from all VCGs in the specific infarction
ORS loop. QRS loop.
vector
of plonor
vectors of planar group in question.
QRS loop ORS
Fig. 5. The usual range and average orientations of the mean 0.02-second, maximal mean, and mean 0.06-second instantaneous vectors of the QRSsl? loop in vectorcardiograms of posterolateral (PLMI), diaphragmatic-posterolateral (D-PLMI), and strictly posterior myocardial infarction (SPMI).
tion of the QRSsI? loop. Thus, in about one sixth of the cases the loop was inscribed entirely counterclockwise; in over 25 per cent of the cases the right sagittal loop was inscribed counterclockwise/clockwise. In almost 20 per cent of the cases the proximal portion of the loop was inscribed clockwise, and the distal portion was inscribed counterclockwise. In the remaining third of the vectorcardiograms the right sagittal loop was inscribed entirely clockwise. In over 50 per cent of the vectorcardiograms of diaphragmatic infarction the frontal QRS loop was inin scribed entirely clockwise, whereas
almost an additional one third of the cases the proximal portion of the frontal loop was inscribed clockwise and the distal was inscribed counterclockwise. portion In the other 7 cases out of the total group with counterclockwise-inscribed frontal loops the efferent limb of the loop was invariably bowed superiorly, usually with clockwise inscription of its initial deflection.
Posterolateral myocardiab infarction
(22
cases). Infarction which involves the posterolateral wall of the left ventricle is characterized by unbalanced QRS forces which are directed anteriorly and to the
VCG QRSsl? loop in inferoposterior
right and are responsible for the following changes in the QRS& loop (Table III and Figs. 5 and 6): (1) The mean 0.02second instantaneous QRS vector was observed to be displaced to the right and anteriorly; its average orientation was +llO degrees in the horizontal projection (normal +60 degrees), and 180 degrees in the frontal projection (normal +30 degrees). Again, there was slight overlapping of the extreme ranges of variation of orientation of the mean 0.02-second instantaneous vectors in the vectorcardiograms of posterolateral myocardial infarction and in the corresponding normal vectorcardiograms, but this was of even less significant degree than in the vectorcardiograms of diaphragmatic infarction. Moreover, the relative magnitude of the anterior component of the mean 0.02-second instantaneous vector in posterolateral myocardial infarction seemed to be greater than in the normal control group of vectorcardiograms.
myocardial
infarction
523
(2) There was significant anterior and medial displacement of the maximal mean instantaneous QRS vector in posterolateral myocardial infarction; the average orientation of this vector in the horizontal projection was +50 degrees (normal +5 degrees), and in the frontal projection, +85 degrees (normal +35 degrees). In only 2 of the 22 cases of posterolateral myocardial infarction was the horizontal QRS loop (or its proximal portion) inscribed clockwise. In 3 of the vectorcardiograms the proximal part of the horizontal QRS loop was inscribed counterclockwise, and the distal portion was inscribed clockwise. It is of interest that in 4 of the 22 vectorcardiograms the right sagittal QRS loop (or its proximal portion) was inscribed counterclockwise. Diaphragmatic - posterolaterab Tyocardial infarction (13 cases). The QRSsE loop in vectorcardiograms of cases of combined diaphragmatic - posterolateral myocardial
Fig. 6. The electrocardiogram and vectorcardiogram in recent posterolateral myocardial infarction. The mean 0.02-second instantaneous vector of the horizontal QRS loop is oriented at about +130 degrees in the horizontal reference frame, and the long axis or maximal mean instantaneous QRS vector is displaced markedly anteriorly and medially in the horizontal plane. The large rightwardly and anteriorly directed Tsl? loop in the horizontal plane is compatible with posterolateral myocardial ischemia.
524
Walsh, Tiongson,
Am. Heart J. 1962 A#&,
Stoddard, and Alassie
Fig. 7. Electrocardiographic and vectorcardiographic findings in old diaphragmatic-posterolateral myocardial infarction. The characteristic findings of each component type of infarction are quite distim-tive and easily recognizable.
infarction showed the features distinctive of each of the two cotnponettt tl-pes of infarction (Table IV and Figs. 5 and 7). 1. The mean 0.02-second instantaneous QRS vector was directed, on the average, along the +115 degree axis in the horizontal projection, along the -35 degree axis in the right sagittal projection, and along the -125 degree axis in the frontal projection. 2. The average orientations of the maximal mean instantaneous QRS vectors of the planar QRS loops were +45, -90, and +120 degrees, in the horizontal, right sagittal, and frontal projections of the vectorcardiogram, respectively. 3. Itt 5 of the 13 vectorcardiograms the horizontal QRS loop was inscribed entirel!, clockwise; in 3 of the vectorcardiograms the right sagittal projection (or its proximal portion) was inscribed counterclockwise, and in 11 of the 13 vectorcardiogratns the frontal QRS loop (or its proximal portion) was inscribed clockwise.
4. In general, it can be said that the single niost characteristic feature of the QRSsl? loop in combined diaphragmaticposterolateral mlrocardial infarction is the presence of an abnormally large early deflection of the loop to the right, anteriorly, and superiorly.
Strictly postrrior j-M case.s).
m,yocardid znfarction
1. The niean 0.02-second instantaneous vector of the QRSsi? loop was not significantl\displaced in niost of the vectorcardiograms; its average orientation was +50 degrees in the horizontal projection, + 15 degrees in the right sagittal projection, and +30 degrees in the frontal projection (Table 1’ and Figs. 5 and 8). 2. Ott the other hand, the maximal nteatt instantaneous QRS vector frequently tended to be oriented slightly tnore anteriorly than in nornial vectorcardiograms. The average orientation in the horizontal projection was observed to be +20 degrees, itt the right sngittal projection, f70
VCG QRS&
loop in inferoposterior
degrees, and in the frontal projection, $20 degrees. 3. Even more striking in the frequency of its presence was a terminal deflection of the QRSsl? loop, the maximum instantaneous vector of which was oriented at about +175 degrees in the horizontal projection (normal, approximately - 80 degrees), at about - 70 degrees in the right sagittal projection (normal - 170 degrees), and at 180 degrees in the frontal projection (normal, about -60 degrees). 4. As a general rule, the horizontal QRS loop in strictly posterior myocardial infarction showed, at the least, anterior bowing of its afferent limb and a right posterior terminal deflection. 5. Three points which should be stressed in regard to the QRSsl? loop in strictly posterior infarction are listed below. A. Strictly posterior infarction is characterized primarily by a change in the second half of the QRSsl? loop. Inasmuch as the posterobasal wall of the left ventricle normally is activated quite late in the QRS interval, it is possible that infarction of this region of the heart has its electrical
myocardiab infarction
effects deferred to a correspondingly later period of the ventricular activation sequence. On the other hand, an intraventricular conduction defect produced by the infarction cannot be excluded as an alternative explanation for the delayed abnormalities of the QRSsl? loop in this type of infarction. B. Although not infrequently the long axis of the QRSsl? loop (i.e., the maximal mean instantaneous or mean 0.04-second vector) may be rotated anterior to its normal orientation, the main diagnostic change consists, more often than not, of one or a combination of the following findings: anterior bowing of the afferent limb of the loop; a right posterior terminal deflection; or a partial or complete change in direction of inscription of the QRSsi? loop in the horizontal and/or right sagittal projection. C. Approximately 50 per cent of the horizontal QRS loops (14 of the 46 cases of strictl\posterior infarction) exhibited either a clockwise or clockwise/counterclockwise direction of inscription, whereas an additional 20 per cent of the cases displayed horizontal QRS loops with a coun-
--. Harizontal
I
Right
lx
UI
525
Sapittal aVR
Frontal aVL
aVF
Fig. 8. The electrocardiogram and vectorcardiogram in a recent strictly posterior myorardial infarction. Note that the main QRS&-loop abnormalities of diagnostic importance involve the afferent limb and terminal portion of the loop. Thus, there is anterior displacement of the afferent limb of the horizontal QRS loop and a clockwise-inscribed terminal deflection of the loop to the right, posteriorly, and superiorly.
526
Walsh, Tiongson, Stoddard, and A4assie
Table IV. Orientation of the mean O.OZ-second, maximal, and terminal mean instantaneous vectors of the QRS& loop in diaphragmatic-posterolateral myocardial infarction Horizontal
R&hi - -----
lima1 Mean 0.02-second instantaneous QRS vector
+90°
Maximal mean instantaneous QRS vector
+loO
Terminal mean instantaneous QRS vector
-170” to - 60”
II Aoevage
Extreme
Lszlal
+90°
-60”
+‘P,oO
-t;Oo
-30”
j-50”
I_--
/ Average
+lls” +?30°
Frontal
sagittal __-
1 Extreme
-3.5”
-t45”
-160”
+40°
- 140°
+:020°
t
:eoO
-‘500~
*
+90” to -120”
Horizontal
Maximal mean instantaneous QRS vector Terminal mean instantaneous QRS yector
*The
extreme range of variation limits of its variation.
.4verage
$20”
+5”
0”
,‘Yoo”
+20°
-10”
+20°
t
+To”
+3s0
loop
is not presented QRS vector,
-6”oo
in orientation
sagiftal
just reported in this study indicate that
- 30” f30”
:9”Y
$-?O”
-5” to -150”
$10”
+to” - 20” +20°
+“4”o”
+‘6”o”
+60” -70”
instantaneous
orienta-
Frontal
-10”
*
-6”oo
+tO”
of the terminal
the average
of the
/ A wrag$ZL~Z~(,,i,;.,I,.,
+6”o”
*
because
mean instantaneous
I
+ 150” +17s0
*
f l”oo”
+70°
+?o”
+‘690°
*
-40°
+20°
- 150”
+‘6”o”
+ls”
+“9”o”
$0
-40” t
-10”
+50°
terclockwise/clockwise inscription. In the right sagittal projection, the QRS loop in 8 of the 46 cases had an entirely clockwise inscription, and 7 cases showed a clockwise/counterclockwise direction of inscription. The observations vectorcardiographic
l:sual
-170”
-2.5” -‘;po~
Right
Extreme
/ Edreme
- 125”
$)o
of the mean O.OZ-second, maximal, and terminal IGOP in strictly posterior myocardial infarction
l~sual
1 Average
- 90”
extreme range of variation in orientation of the terminal instantaneous vector of the QRS& wide limits of its variation. tBecause of the extremely wide range of variation in orientation of the terminal mean instantaneous tion of this vector is not listed because it would have little significance.
Mean 0.02-second instantaneous QRS vector
L’sual
- 70” to -20”
*The
Table V. Orientation vectors qf the QRSsfi
j
vector
of the QRSsfi
loop
is omitted
180”
because
*
of the wide
the various types of inferoposterior infarction are characterized by deviation of certain mean instantaneous vectors of the QRS& loop away from the effective electrical site of the infarction. As one might anticipate, the mean instantaneous vectors of the QRSsl? loop which are affected by an infarction are those which appear during that portion of the QRS interval when the infarcted heart muscle normally undergoes
Volume .Sumber
63 4
VCG QRSsI? loop in inferoposterior
activation. Moreover, the postinfarction mean instantaneous vectors of the QRSsI? loop generally acquire not only an abnormal direction but also an increased magnitude as well. The mean 0.02-second instantaneous vector of the QRSsI? loop is the vector which is primarily affected in the various types of inferoposterior infarction, whereas the maximal or mean 0.04-second vector less frequently exhibits diagnostic changes. The principal exception to the previous statement is the case of strictly posterior myocardial infarction, which is characterized vectorcardiographically by abnormalities of the later portions of the QRSsl? loop. Two alternative explanations for this finding were cited earlier in this paper. Summary
1. The QRS&-loop findings have been described in vectorcardiograms recorded with the Frank lead system from 100 subjects without clinically detectable heart disease and from 153 patients with inferoposterior myocardial infarction. 2. In the vectorcardiograms of cases of diaphragmatic (inferior), posterolateral, and diaphragmatic-posterolateral infarction, the abnormality most consistently
myocardial
,infarction
527
observed was deviation of the mean 0.02second instantaneous vector, and, to a lesser extent, the maximal or mean 0.04second instantaneous vector, of the planar QRS loops away from the effective electrical site of the infarction. 3. In casesof strictly posterior infarction the QRSsE loop displayed an anterior deviation of the maximal or mean 0.04second and subsequent instantaneous QRS vectors. REFERENCES 1. Grant, R. P., and Murray, R. H.: QRS complex deformity of myocardial infarction in the human subject, Am. J. Med. 17587, 1954. 2. Gardberg, N., and Levy, L.: I and II-The QRS complex of the electrocardiogram in myocardial infarction, with remarks on methods of recording, AK HEART J. 51501 and 654, 1956. 3. Grishman, A., and Scherlis, L.: Spatial vectorcardiography, Philadelphia, 1952, W. B. Saunders Company. E., and Walsh, T. J.: Clinical vector4. Massie, cardiography and electrocardiography, Chicago, 1960, The Year Book Publishers, Inc. 5. Goldberger, E.: Unipolar lead electrocardiography and \-ectorcardiography, ed. 3, Philadelahia. 19.53. Lea & Febieer. 6. F&k, E.: .qln accurat: clinically practical system for spatial vectorcardiography, Circulation 13:736, 1956.