718

10.

lL.

12.

13.

14.

15.

cardiography and Electrocardiography. Chi-
cago, The Year Book Publishers, Inc., 1960,
pp. 313, 333.

Meyers, G. B., Kiem, H. A., anp Himarzxa,
T.: VI. Correlation of electrocardiographic
and pathologic findings in posterolateral in-
farction. Am, Heart J. 38: 837, 1949.

Watsu, T. J., Tioncson, P. M., Stopparp,
E. A, AND Mass, E,: The  vector-
cardiographic QRSsE-loop findings in infero-
posterior myocardial infarction. Am. Heart J.
63: 516, 1962.

Tuttocu, J. A.: The electrocardiographic fea-
tures of high posterolateral myocardial in-
farction. Brit. Heart J. 14: 379, 1952.

Trancuesi, J., Terxema, V., Epam, M., Boc-
CALANDRO, I., BocaNeora, J., AND PILEGGI,
‘The vectorcardiogram in dorsal or posterior
myocardial infarction. Am. J. Cardiol. 7: 505,
1961.

Levy, L., anv Hyman, A. L.: Difficulties in the
electrocardiographic diagnosis of myocardial
infarction. Am. Heart J. 39: 243, 1950.

Exex, S. R., ALLENSTEIN,. B. J., KornsLurs,
A. W., Grirrits, G. C., anp Levinson, D. C.:
The spatial vectorcardiogram in myocardial
infarction typified by prominent R waves in

16.

VA

18.

19,

20.

21.

24,

PERLOFF

leads aVy and V,. Am. Heart J. 47: 477,
1954.

Rorurerp, E. L, Bernsrew, A., WACHTEL, F.
W., anp Karten, W. S.: The vectorcardio-
gram in direct posterior wall myocardial in-
farction. Am. J. Cardiol. 7: 496, 1961.

Worrr, L., Matsor, K. S., anp Rican, J. L.:
The diagnosis of posterior myocardial infarc-
tion, Am. Heart J. 46: 21, 1953.

Scuerus, L., aD GrisHMan, A.: Spatial vec-
torcardiography: Myocardial infarction. Am.
Heart J. 42: 24, 1951.

GrisHman, A., ScHeRus, L., AND Lasser, Ri:
Spatial vectorcardiography. Am. J. Med. 14:
184, 1953.

Scrrertis, L., Lasser, R. P., AND GRISHMAN, A.:
Spatial vectorcardiography: The normal vec-
torcardiogram. Am, Heart J. 42: 235, 1951.

Prvercer, H.: The normal orthogonal electro-
eardiogram and vectorcardiogram. Circulation
17; 1102, 1958.

Grant, R. P.: Clinical Electrocardiography.
New York, McGraw-Hill, 1957, p. 51.

. Navas, A.: Pediatric Cardiology. Philadelphia,

W. B. Saunders, Company, 1963, p. 63.
Grant, R. P.: Mechanisms of QRS prolongation
in man. Am. J. Med. 21: 534, 1956.

Circulation, Volume XXX, November 1964


POSTERIOR MYOCARDIAL INFARCTION

or R/S ratios of one or over. These categories
included some normal children, some cases of
complete right bundle-branch block, the Wolff-
Parkinson-White syndrome with anteriorly direct-
ed delta wave, right ventricular hypertrophy, and
some normal adults.

709

Results
The data in the infarct group are sum-
marized in table 2.
In all cases studied with extra chest leads
(table 2) the posterior Q area extended well

Figure 2
Extra chest leads.
Table 2
Electrocardiographic Data in the Infarct Group
No cases Per cent cases,

0.04-sec. R Vy 15/20 1
0.04-sec. R Vz 20/20 100
0.04-sec. R in rt. ant. chest leads 9/10 90
0.04-sec. Q in It. post. chest leads 9/10 90
Slur descending limb R V, 6/20 30
Slur descending limb R V, 2/20 10
V, R/S=1 12/20 60
V, B/S=1 19/20 95
Frontal QRS <5 mm. 3/20 15
No abnormal Q waves 11/20 55
Q 2, 3, VF 6/20 30
Q1, VL 2/20 10
Q 2, 3, VF, 1, VL 1/20 5
Upright T V, 10/20 50
Isoelectric T V, 6/20 30
Inverted T V, 4/20 20
Frontal T < 2 mm, 8/20 40
ST. depression V; 4/20 20
ST depression V2 4/20 20
Frontal axis +-70° 1/20 5
Frontal axis -+-15° to +45° 9/20 45
Frontal axis 0° to —15° 10/20 50

Circulation, Volume XXX, November 1964



714

Figure 7

Case 19, table 1. Autopsy specimen showing infarc-
tion of the left ventricle immediately below the left
atrial attachment adjacent to the interventricular sep-
tum, See figure 6 for electrocardiograms,

The Q waves were recorded well to the
left of the midline in contrast to normal sub-
jects in which posterior Q areas have been
found to lie on the right side of the chest
with little or no extension beyond the mid-
line.§ The extra chest leads were helpful in
corroborating the information contained in
lead V; but generally did not contain addi-
tional diagnostic information.

Consideration was given to the possibility
that a decrease in amplitude of the limb
lead QRS might accompany the anterior shift
in electromotive force. Amplitudes of 5 mm. or
less were considered abnormally small.1 Only
15 per cent of the infarct tracings had frontal

PERLOFF

plane QRS amplitudes of less than 5 mm.
(table 2) although in two of the acute in-
farcts the limb lead QRS voltage decreased
when compared with control tracings (figs.
3, 4, and 8).

Eleven of the infarct tracings contained no
abnormal Q waves (table 2) and were be-
lieved to represent examples of isolated
strictly posterior infarction. The most frequent
associated abnormal Q area was diaphrag-
matic (six cases) (fig. 6). Lateral infarction
coexisted in two instances and both lateral
and diaphragmatic infarction coexisted in
one instance (fig. 8). These observations in-
dicate that although strictly posterior myo-
cardial infarction can occur as an isolated
lesion,!": 1718 it often occurs in association
with diaphragmatic or lateral infarction.1*"*

As the QRS electrical axis shifts leftward in
the frontal plane, it also tends to shift pos-
teriorly in the horizontal plane.2? The more
leftward the limb lead axis, the less con-
spicuous are the R.waves in leads V; and Ve.
It follows that broad or tall right precordial R
waves assume greater diagnostic importance
in the presence of leftward deviation of the
QRS electrical axis. It is significant that the
frontal plane electrical axes were between
+45° and —-15° in 95 per cent of the infarct
tracings in this series.

The T wave is characteristically directed
away from the area of infarction. In a strictly
anterior infarct, the T wave in V; should be
inverted (fig. la). In a strictly posterior in-
farct,!° 12.18 this T wave should be upright
(figs. la, 4, 6, and 8). The majority of cases
(table 2) had T waves in V, that were up-
right (50 per cent) or isoelectric (30 per
cent). However, T waves were upright in
Vi in 20 per cent of the normal tracings
(table 3). Furthermore, it should be antici-
pated that the upright T waves of acute
posterior infarction (fig. 8) might become
isoelectric or inverted when the infarct heals.
Despite these limitations, an anterior shift in
the T wave is a valuable sign of strictly pos-
terior infarction ** 1*?* especially when trac-
ings before infarction are available for com-
parison (figs. 3, 4, 6, and 8).

Circulation, Volume XXX, November 1964



POSTERIOR MYOCARDIAL INFARCTION

stance there was an area of left ventricular
infarction immediately below the atrioventric-
ular sulcus adjacent to the interventricular
septum. In the latter case (strictly posterior)
the infarcted area was limited in extent and
was associated with ventricular aneurysm. In
the other three cases, the infarcted areas
were more extensive and the electrocardio-
grams displayed diaphragmatic and lateral Q
areas in addition to the increase in duration
and height of the R wave in Vi.

Lead Vi was normal in five subjects. One
had autopsy evidence consistent with acute

Figure 4

Case 6, table 1. Upper, vectorcardiogram after infarc-
tion illustrating the anterior ORS shift in the horizon-
tal plane. Lower. Electrocardiogram after infarction
for comparison with figure 3. Note absence of patho-
logic Q waves. Lead V, now manifests an R wave of
0.04 second with slurred descending limb. Right pre-
cordial leads display upright T waves and the R/S
ratio in V, has increased to one.

Circulation, Volume XXX, November 1964

711

postero-diaphragmatic infarction and four had
vectorcardiograms considered diagnostic of
isolated strictly posterior infarction. The
B/S ratios in lead V2 were 14 to 2.5 in these
five subjects. The T waves in lead V2 were
upright in all five. The R wave in lead Ve
was 0.04 second in four cases and 0.035 sec-
ond in one (acute infarct, autopsied). There
was a slur on the descending limb of the R
wave in lead V2 in two subjects. The frontal
plane QRS electrical axes were +30° to +40°
in three subjects and —5° to —30° in the
other two.

The data in the normal group are sum-
marized in table 3,

Discussion

The dorsal or infra-atrial portion of the
left ventricle may be anatomically oriented
posteriorly just to the left of the vertebral
column (fig. 1). Infarction in this area, by
causing loss of posteriorly directed electrical
forces, can produce a recognizable anterior
shift in the QRS loop of the vectorcardiogram
(fig 1b).1°-2° In the electrocardiogram, there
may be an accompanying increase in dura-
tion and amplitude of the R wave in lead
Vi.710 12,15 The T wave may become up-
right !° 12,18 and, in the acute stage, the ST
segment may be depressed.® * *® Thus, lead
V; becomes the mirror image of an anterior
infarction (fig. la)’ and the more familiar
“infarct pattern” appears in posteriorly
placed V leads”: 12 (fig. 1b).

Strictly posterior myocardial infarction is
considered to be relatively uncommon.** Its
true incidence is difficult to assess since the
electrocardiographic diagnosis is not routine-
ly made. When posterior infarction occurs as
an isolated lesion, pathologic Q waves do
not appear in the standard electrocardio-
gram.®-® When the combination of either
postero-diaphragmatic or postero-lateral in-
farction occurs, the extent of the infarcted
area may be misjudged. Finally, signs of re-
infarction may be overlooked in the electro-
cardiogram of a subject who experiences a
strictly posterior infarct in the presence of a
previous diaphragmatic or lateral infarct.



710

PERLOFF

Table 3
Electrocardiographic Data in 100 Normal Controls

0.04-sec, R wave V,
0.04-sec. R wave Va

Slur descending limb R wave V,
Slur nadir S wave V,

Slur ascending limb $ wave V,
Slur descending limb R wave V,
Slur nadir S wave V>

Slur ascending limb $ wave Vz
V, B/S=1

Ve, R/STM=1

Upright T V,

Upright T V,

0.04-sec. R V, with frontal axis +45° to +60°
0.04-sec. R Vy with frontal axis +45 to +60°

V2 R/S=1 with frontal axis +45 to 460°

Unequivocal 0% borderline 4%
Unequivocal 3% borderline 10%
1%

3%

Be

3%

2%

0%

0%

12%

20%

95%

75% (3/4 cases)

39% (5/13 cases)

58% (7/12 cases)

Figure 3

Case 6, table 1. Electrocardiogram before infarction (history of angina) for
comparison with figure 4. Note absence of pathologic Q waves. Small R
waves and inverted T waves appear in leads V, and V,.

to the left of the vertebral column (posi-
tions 1 through 15, fig. 2) but generally not
as far as the angle of the scapula (positions
13 through 20). The Q area on the left side
of the chest was relatively large. In normal
subjects, posterior Q areas have been de-
scribed on the right side of the chest with
little or no extension to the left of the mid-

line.* Such extensions when present were
found to occupy relatively limited areas lo-
cated high in the back.6

In the four autopsied subjects (table 1)
the electrocardiographic designations of in-
farction were postero-diaphragmatic in two,
postero-lateral-diaphragmatic in one, and
strictly posterior in one. In each in-

Circulation, Volume XXX, November 1964


POSTERIOR MYOCARDIAL INFARCTION

oo

OTE BREE

Figure 6

Case 19, table 1. Upper. Electrocardiogram before infarction for comparison
with tracing below. Note absence of pathologic Q waves. Small R waves and
shallow T waves appear in leads V, and V,. Lower. Electrocardiogram after
infarction. Pathologic Q waves of diaphragmatic infarction are now present
in leads II, HII, and VF. In addition, leads V, and V, now manifest the an-
terior ORS shift of strictly posterior infarction. The R waves in these leads
have become broad and tall and the T waves have increased in amplitude.
See figure 7 for autopsy location of infarction.

Circulation, Volume XXX, November 1964

713



et-(G

The Recognition of Strictly Posterior
Myocardial Infarction by Conventional
Scalar Electrocardiography

By Josep K. Peatorr, M.D.

Circulation, Volume XXX, November 1964



716

A decrease in amplitude of the T waves in
the limb leads has been described as an ac-
companiment of the anterior T shift.7 In
this series (table 2) 40 per cent of the T
waves in the limb leads were less than 2 mm.,
which was considered the lower limits of
normal."

The ST segment typically deviates toward
an area of acute myocardial infarction. Ele-
vations of the ST segments in leads V, and
V2 are therefore found in acute anterior in-
farction (fig. la) and depressions in these
leads can be anticipated in acute posterior
infarction® 1°12 (figs.. la and 8, table 2).
Persistence of this acute shift in the ST seg-
ment is an electrocardiographic sign of ven-
tricular aneurysm. One patient in this series
manifested persistent ST-segment depressions
in the right precordial leads (fig. 9) and at
autopsy had an isolated posterior ventricular
aneurysm.

Five patients in the infarct group (one

PERLOFF

autopsied) had a normal lead V,. In this
group lead: V2 manifested‘ the 0.04-second R
waves and increased R/S ratios consistent
with posterior infarction. However, the in-
cidence of similar R and T-wave changes in
the normal V2 (table 3) limited the diagnos-
tic usefulness of this lead. It may be signifi-
cant that in all five of these patients the limb
lead electrical axis was leftward (+40° to
—30°). These observations, though limited,
suggest that the diagnosis of posterior in-
farction might be suspected when Vz includes
the combination of broad tall R waves with
slurred descending limbs, upright T waves,
and ST-segment depressions in the presence
of leftward deviation of the limb lead elec-
trical axis.

Lead V; may manifest R waves of 0.04
second or R/S ratios equal to or greater than
one in five other categories of electrocardio-
grams, Of these categories the normal child 2*
poses no diagnostic problem. Complete right

Figure 9
Case 2, table 1. Note in lead V, the 0.04-second R wave with slurred
descending limb, the R/S ratio in V, greater than one, and the marked

ST-segment depressions in V,.,. At autopsy the patient had strictly posterior
infarction (old) with posterior ventricular aneurysm.

Circulation, Volume XXX, November 1964


POSTERIOR MYOCARDIAL INFARCTION

Figure 8

Case 3, table 1. Upper. Electrocardiogram before infarction for
éomparison with tracing below. Note absence of pathologic Q
waves. Small R waves and inverted T waves appear in leads V,
and V,. Lower. Electrocardiogram of acute infarct. Q waves in
leads I, V1, and V,., have increased in duration and a Q wave has
appeared in lead II. In addition, there is a striking anterior shift
in the QRS manifested by broad, tall R waves in the right pre-
cordial leads, In leads V, and V, the ST segments are now de-
préssed and the T waves upright. Patient autopsied.

Circulation, Volume XXX, November 1964

715



712

PERLOFF

OSTERIOR _

ae

Figure 5

Case 6, table 1. Extra right anterior chest leads showing R waves of 0.04
second with slurred descending limbs. Extra posterior chest leads with Q
area to the left of the midline. See figure 2 for lead placements.

The lectrocardiographic diagnosis of
strictly posterior infarction depends princi-
pally upon the detection of an abnormal an-
terior shift in the QRS (figs. 1b, 3, and 4).
According to the data in this study (table 2),
the abnormal anterior shift was most fre-
quently manifested by 0.04-second R waves
in leads V; (75 per cent) and V2 (100 per
cent) (figs. 3 through 5). Lead V, was the
more dependable of the two, since R waves
of 0.04-second in V; occurred in only four of
the normal tracings (table 3). The anterior
QRS displacement was further reflected by
an R/S ratio of one or more in leads V; (60
per cent) and Vz (95 per cent) (table 2,
figs. 6 through 8). Again lead V, was the
more dependable of the two since R/S ratios
of this magnitude were not found in V; in
any of the normal tracings (table 3). R waves
of abnormal duration or amplitude in V, were
particularly reliable signs when tracings be-
fore infarction were available for comparison
(figs. 3, 4,6, and 8).

A slur or notch occurred on the descend-

ing limb of the R wave in lead Vi in 30 per
cent of the infarct tracings (table 2, figs. 1b,
4, and 5). Others have called attention to
this type of notching®® which appears to
coincide with an abrupt change in direction
of the QRS vector loop (fig. 4). In the nor-
mal subjects a similar slur was found in only
one of the tracings (table 3). The presence
of a notch on the descending limb of the R
wave in V; might therefore be considered a
helpful minor sign in posterior infarction.

R waves of 0.04 second were commonly
found in one or more of the extra right
precordial leads (table 2, figs. 2 and 5). The
morphology of these R waves was generally
similar to lead V; including slurring of the
descending limb (fig. 5). Q waves of 0.04
second were commonly found in the extra left
posterior chest leads * 3? between the spine
and the scapula (figs. 2 and 5). These Q
areas reflected the loss of posteriorly direct-
ed electrical forces and were diametrically
opposite the right anterior chest leads-where
0.04-second R waves were recorded (fig. Ib).

Circulation, Volume XXX, November 1964


PERLOFF

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Circulation, Volume XXX, November 1964


POSTERIOR MYOCARDIAL INFARCTION

707

Figure 1

a, Upper. Schematic illustration of strictly anterior infarction producing a
Q wave, ST-segment elevation, and T-wave inversion in lead V,. Lower.
Schematic illustration of strictly posterior infarction producing a tall, broad
R wave, ST-segment depression, and upright T wave in lead V,. The
familiar “infarct pattern” (Q wave, ST-segment elevation, and T-wave in-
version) is recorded posteriorly. b, Upper. Schematic illustration of a normal
horizontal plane vectorcardiogram with lead V,. b, Lower. Schematic illus-
tration of a horizontal plane vectorcardiogram in strictly posterior infarction
with lead V, and a diametrically opposite posterior lead.

electrocardiographic or vectorcardiographic infer-
ence and cannot be accurately determined an-
atomically,

Three patients had symptoms and serum en-
zyme evidence of acute infarction, eight had his-
tories of prior infarction, and eight had typical
histories of angina or coronary insufficiency. One
patient, a 29-year-old man, had received a se-
vere blow in the precordium while boxing 1 year
prior to this study. The posterior left ventricu-
lar infarct in this case was believed to have been
caused by the “contrecoup” effect of the anterior
blow. Twelve-lead scalar electrocardiograms were
available before and after infarction in three in-
stances. Multiple electrocardiograms (between
three and five) were obtained in 12 additional
patients. In 10 subjects extra chest leads were
taken with the electrodes placed as illustrated
in figure 2. Flat electrodes permitted these trac-
ings to be recorded with the patient in the
same supine position used when the 12 conven-
tional leads were taken.

Circulation, Volume XXX, November 1964

The area of infarction was considered to be
strictly posterior in 11 patients, postero-dia-
phragmatic in six, postero-lateral in two, and
postero-lateral-diaphragmatic in one. None of the
patients had clinical evidence of right ventricu-
lar hypertrophy, pulmonary embolism, or chron-
ic lung disease.

Control electrocardiograms were studied as fol-
lows. Three observers independently reviewed
250 adult electrocardiograms indexed as “within
normal limits.” One hundred of these tracings
interpreted as normal by all three observers
were used for analysis of the duration of the
R wave, the R/S ratio, the incidence of slurring
of the R or S waves, and the frequency of up-
right T waves in leads V, and V2 and for an-
alysis of the mean frontal plane QRS electrical
axis, There was no clinical evidence of heart
disease in this group.

Selected electrocardiograms were also exam-
ined in five, other categories in which lead V;
might manifest initial R waves of 0.04-second



The Recognition of Strictly Posterior

Myocardial Infarction by Conventional
Scalar Electrocardiography

By Josep K. Pertorr, M.D.

LECTROCARDIOGRAPHIC _ terminol-

ogy commonly refers to inferior or
diaphragmatic infarction as “posterior.”!>
Strictly posterior infarction as a separate en-
tity (fig. la) is generally not mentioned.‘
Inclusion of this category permits identifica-
tion of five individual locations of infarction:?
diaphragmatic, lateral, apical, strictly anterior,
and strictly posterior.

Myocardial infarction _characteristically
produces Q waves of abnormal duration in
one or more of the 12 standard electrocardio-
graphic leads..? These Q waves are written
because the initial portion of the QRS is
directed away from the area of inert myocar-
dium. If this inert area is electrically posterior
(fig. la), the initial forces will be directed
anteriorly (fig. 1b) (perpendicular to the
frontal plane) and no abnormal Q waves will
appear in either limb or chest leads.*-* Be-
cause of this absence of pathologic Q waves,
strictly posterior infarotion is one of the most
commonly overlooked _ electrocardiographic
abnormalities. Textbooks of electrocardiog-
raphy, with few exceptions,” * contain little
or no reference to this category.'* Although
some authors have commented upon individ-
ual changes that might occur in right pre-
cordial leads,* 1°15 others have stated that
diagnostic signs do not appear in the electro-
cardiogram as a rule.!**8 On the other hand,
the vectorcardiographic recognition of strict-
ly posterior infarction is generally ac-

From the Department of Medicine, Georgetown
University School of Medicine, Division of Cardiol-
ogy, Georgetown University Hospital, Washington,
D.C.

Supported by a Federal Aviation Agency Grant
FAA-2050 and by a United States Public Health
Service Research Career Program Award No. 5-K3-
He-14,009-03 and Grant HE-08390.

706

cepted.®: 11, 18. 15-20 This study was undertaken
in order to determine whether the diagnosis
of strictly posterior infarction could be estab-
lished by conventional scalar electrocardiogra-

phy.

Materials and Methods

Twenty cases were studied, 15 male and five
female, with an average age of 55 years and a
range of 29 to 80 years (table 1). In 16 cases
the diagnoses were based on orthogonal vector-
cardiograms and electrocardiograms with use of
Schmitt’s corrected SVEC III leads. Narrow
ranges of normal have been established with this
corrected lead system, and quantitative data on
the normal orthogonal vectorcardiogram and elec-
trocardiogram are available.*4 The following in-
formation was utilized:24 (1) R/S ratio in lead
Z-range 0.10 to 1.32, (2) R duration in lead
Z—range 0.022 to 0.054 second, mean and one
standard deviation 0.038 +: 0.008 second. These
data permit accurate detection of an abnormal
anterior shift in QRS. In four cases verification
of the diagnosis of strictly posterior infarction
was based on autopsy evidence. These patients
died before vectorcardiograms could be obtained.
Proof rests on the validity of attempting to re-
late the gross anatomic site of infarction to the
clinical ‘electrocardiogram. It is recognized that
the anatomic names given to the areas of in-
farction properly relate to the location of al-
tered electrical activity transmitted to the body
surface and do not necessarily indicate the re-
gion of the heart that has been infarcted. Never-
theless, in each of the four postmortem speci-
mens the left ventricle was infarcted immediate-
ly below the atrioventricular sulcus adjacent to
the interventricular septum (fig. 7), a location
consistent with the pathologic-electrocardiograph-
ie correlations of others.1°.12 This dorsal or
infra-atrial portion of left ventricle represents
an area that is most likely to be oriented pos-
teriorly in the living subject. Loss of electrical
forces in this region offers a reasonable explana-
tion for an anterior shift in the QRS. It is further
recognized that the degree of inferior or lateral
extension necessary to produce associated dia-
phragmatic or lateral infarction is basically an

Circulation, Volume XXX, November 1964


POSTERIOR MYOCARDIAL INFARCTION

bundle-branch block? and the Wolff-Parkin-
son-White syndrome with anteriorly directed
delta wave, while readily recognizable in
themselves, may not permit the electrocardio-
graphic diagnosis of coexisting posterior in-
farction. This is the only type of infarct QRS
deformity in the electrocardiogram which is
obscured by right bundle-branch block,?*
since the conduction defect is in itself associ-
ated with a broad R wave in Vi. Disease
states associated with right ventricular hy-
pertrophy should be excluded by careful
clinical evaluation.!* From the electrocardio-
graphic point of view, upright T waves in
lead V,"* and leftward deviation of the limb
lead. electrical axis are exceptional in right
ventricular hypertrophy but common in pos-
terior infarction. Occasionally it may be dif-
ficult to distinguish a normal from an abnor-
mal 0.04-second R wave in V; in the adult.
In the normal tracings R waves of 0.04 second
in V, tended to occur with frontal plane
axes greater than +45° (table 3). A right-
ward shift in the limb lead axis may normally
be associated with a relatively anterior shift
in the QRS analogous to the electrical axes
of the child.®:?.?* It appears that the more
vertical the electrical axis, the more likely
is the normal occurrence of an R wave of 0.04
second in V,.

Summary

This study was undertaken in order to
determine whether the standard scalar elec-
trocardiogram contains sufficient information
to permit the recognition of strictly posterior
myocardial infarction. Sixteen patients were
selected on, the basis of vectorcardiographic
evidence and four on the basis of autopsy
evidence. One hundred normal adult electro-
cardiograms served as controls. The data in-
inate that strictly posterior infarction causes
\ R waves of 0.04 second in V, and in
contiguous right anterior chest leads with up-
right T waves and, in the acute phase, ST-
segment depressions, (2) Q waves of 0.04
second in an area. posteriorly between the
spine and the left scapula, (3) R/S ratios
equal to or greater than one in V; and Va, (4)

Circulation, Volume XXX, November 1964

717

slurring of the descending limb of the R
wave in lead V, due to abrupt change in
QRS direction, and (5) no pathologic Q
waves in the standard 12 leads unless dia-
phragmatic or lateral infarction coexists. Ex-
tra chest leads derived from the right anterior
and left posterior thorax serve principally to
corroborate the diagnoses. R waves of 0.04
second or R/S ratios equal to or greater than
one in lead V; were also found in the normal
child, complete right bundle-branch block,
the Wolff-Parkinson-White syndrome with
an anteriorly directed delta wave, right ven-
tricular hypertrophy, and an occasional nor-
mal adult especially with vertical frontal
plane electrical axis. Attention to these differ-
ential diagnoses and to the foregoing mani-
festations of strictly posterior infarction facil-
itate its recognition by conventional scalar
electrocardiography.

Acknowledgment

The vectorcardiograms were taken and interpreted
in the laboratory of Dr. Hubert V. Pipberger. The
author is most grateful to Dr. Pipberger for his inter-
est and advice and for his critical review of the
manuscript. The author further acknowledges Dr.
Robert P. Grant, for his invaluable suggestions when
the study was first begun.

References

1, Lepescuxin, E.: Modern Electrocardiography.
Baltimore, The Williams & Wilkins Co., 1951,
pp. 140, 351.

2. Gouppencer, E.: Unipolar Lead Electrocardiog-
raphy and Vectorcardiography. Ed. 3. Phila-
delphia, Lea & Febiger, 1953.

3. BERNREITER, M.: Electrocardiography. Ed. 2.
Philadelphia, J. B. Lippincott Company, 1963.

4. Barker, J.: The Unipolar Electrocardiogram.
New York, Appleton-Century-Crofts, Inc.,
1952.

5. Katz, L. N.: Electrocardiography. Philadelphia,
Lea & Febiger, 1946.

6, Dimonp, E. G., ScuLesincer, P., AND LuNa,
R. L.: Electrocardiography. Kansas City,
Corinth Press, 1961.

7. Grant, R. P., anp Estes, E, H.: Spatial Vector
Electrocardiography. Philadelphia, The Blakis-
ton Co., 1951, p. 117.

8. Granv, R. P., AND Murray, R. H.: QRS com-
plex deformity of myocardial infarction in the
human subject. Am. J. Med. 17: 587, 1954.

9. Massie, E., anp Watsu, T. J.: Clinical Vector-