J. ELECTROCARDIOLOGY, 8 (4) 335-342

Relation of Left Ventricular Contractile Patterns in Coronary Artery Disease to the Electrocardiogram and Vectorcardiogram BY JOSEPH HILSENRATH,M.D., FAROUK TABRAH, M.D., ROBERT I. HAMBY, M.D. AND IRWIN HOFFMAN, M.D.

SUMMARY

t i e n t s with left v e n t r i c u l a r h y p e r t r o p h y , normal QRS-abnormal T and normal QRS-T on ECG-VCG, 65-70% had synergy. However, 30-35% had asynergy in various combinations not suspected from the ECG or VCG. Coronary artery disease severity was less pronounced in patients with synergy t h a n with asynergy and single vessel disease was more common in the former, 47% versus 18-30% in the latter. However, coronary artery disease severity was the same for all ECG-VCG groups except for anterior plus inferior infarction patterns where it was most severe.

Two hundred t h i r t y patients with coronary artery disease (CAD) were studied with left ventriculography, coronary arteriography, e l e c t r o c a r d i o g r a p h y (ECG) and vectorcardiography (VCG) to determine how well left v e n t r i c u l a r (LV) c o n t r a c t i l e d e f e c t s could be predicted from the ECG-VCG patterns and how this was related to the coronary disease location and severity. Of 124 patients with infarction patterns on ECG-VCG about 50% had LV contractile defects localized to the corresponding ECG-VCG abnormalities, i.e., antero-apical a s y n e r g y with anterior infarction patterns, inferior asynergy with inferior infarction patterns, or antero-apical plus inferior asynergy with anterior plus inferior patterns. About 20% in each infarction group had unexpected synergy on ventriculography except for patients with dorsal infarction patterns (synergy in 68%) who are discussed as a special problem. Another 25-30% of patients had more extensive contractile a b n o r m a l i t y t h a n indicated by the ECG-VCG patterns. In 106 pa-

Classical QRS abnormalities of infarction are not reliable predictors of coronary artery obstruction as d e m o n s t r a t e d by selective coronary a r t e r i o g r a p h y 1-3 or post m o r t e m e x a m i n a t i o n . 4 The incidence of such false positive diagnoses, depending upon the clinical characteristics of the population studied, m a y be as high as 50% in the case of anterior infarction patterns 1'2 and 30% in the case of inferior i n f a r c t i o n p a t t e r n s . 8 The present s t u d y is concerned with t h e value of the electrocardiogram or v e c t o r c a r d i o g r a m in predicting localized defects of left ventricular contractility. It is widely believed and reported t h a t ECG infarction patterns rather accurately predict localized ventricular contractile defects to closely corresponding areas of the left ventricle. 5's It is our experience, reported herein, t h a t accurate correlation is present only in about 50% of patients presenting with QRS evidence of infarction. The remaining patients have either no left ventricular contractile defect at all or more extensive asynergy t h a n would be predicted by the ECG or VCG.

From the Department of Medicine, Cardiology Division, Long Island Jewish-Hillside Medical Center, New Hyde Park, New York 11040 and the School of Medicine, Health Sciences Center, State University of New York at Stony Brook, Stony Brook, New York 11790. Reprint requests to: Joseph Hilsenrath, M.D., Department of Medicine, Division of Cardiology, Long Island Jewish-Hillside Medical Center, New Hyde Park, NY 11040. 335

336

HILSENRATH ET AL

MATERIALS AND METHODS Two hundred thirty patients were studied. All patients were referred because of angina pectoris. The procedure included a 12-lead ECG, a Frank system VCG, 7 right and left heart catheterization, coronary and left ventricular angiograms. VCGs were displayed using a Hewlett-Packard amplifier and visoscope. The loops were photographed with a Polaroid camera. The oscilloscope had a sensitivity of 1 mv=5 cm. Hemodynamic studies were performed after an overnight fast after all drugs were discontinued for at least 24 hours with patients in the supine position. Right and left heart catheterizations were performed on all patients. The right heart studies were performed using standard Cournand catheters with a platinum tip electrode. The left heart chambers were evaluated by the t r a n s s e p t a l technique or retrograde approach through either the femoral artery percutaneously or brachial artery cutdown procedure. Pressures were recorded on an Electronics-for-Medicine oscillographic recorder, Model DR-12 utilizing Statham P23D strain gauges. The mid-thoracic position was used as the zero pressure reference. Selective coronary and left ventricular cineangiography were performed in all patients by methods previously described. 8 Left ventricular angiograms were performed in the right anterior oblique projection and obtained by injecting 0.75 ml per kilogram of 90% sodium meglumine diatrizoate into the left ventricle. Cineangiograms were taken with a 35 mm camera at 60 frames/sec. The cine films were projected with a 35 mm projector (Vanguard Instrument Corporation) for evaluating contractile patterns. Left ventricular contractile patterns were evaluated only in beats not preceded by a ventricular premature beat. The contractile patterns were evaluated by superimposing a tracing of the end-systolic silhouette onto the enddiastolic silhouette. Electrocardiographic and vectorcardiographic criteria used have been described previously. 1'~9 Severity of coronary artery disease obstruction was classified from the arteriogram TM as Grade 0 for no obstruction, Grade 1 for slight irregularity to 30% narrowing, Grade II for 30-50% narrowing, Grade III for 50-90% narrowing, Grade IV obstruction greater than 90% but not complete, Grade V total occlusion with distal filling by collateral flow and Grade VI total occlusion without distal filling by collaterals. Grades III to VI were considered significant. Patients who showed no significant coronary artery disease, that is, all vessels with Grades 0-11, were excluded from the study, as were patients with rheumatic valvular, congenital or primary myocardial heart disease regardless of the presence of complicating coronary artery disease. The 230 patients studied had at least Grade III-VI disease of one or more major coronary arteries. Left ventricular contractile patterns were classified as suggested by Herman and Gorlin. ~1 Normal left ventricular contraction was defined as synergy. Localized abnormal left ventricular contraction was defined as asynergy. A s y n e r g y included asyneresis and akinesia. Regional contractile abnormalities were classified into three groups: antero-apical, infero-posterior, and antero-apical plus infero-posterior. For each patient a coronary

disease score was obtained by adding together the Grade associated with each of the three major coronary arteries, maximal score being 18. The criteria used for identifying the dorsal infarction were more stringent than any published so far. 8 We required either an anterior duration of 50 msec or more, anterior posterior voltage ratio of 1.5 or more, or an anterior voltage of 0.6 mv or more. In addition, QRS evidence of anterior, inferior or lateral infarction excluded patients from the true dorsal myocardial infarction group.

RESULTS T h e E C G - V C G m a t e r i a l was classified into 7 groups. F o r t y (17%) of t h e 230 cases h a d a n t e r i o r i n f a r c t i o n p a t t e r n s . Forty-five (20%) had i n f e r i o r i n f a r c t i o n p a t t e r n s , and 27 (12%) h a d c o m b i n e d a n t e r i o r plus inferior i n f a r c t i o n p a t t e r n s . T w e l v e (5%) h a d p u r e dorsal infarct i o n p a t t e r n s . S e v e n t e e n (7%) h a d l e f t v e n t r i c u l a r h y p e r t r o p h y , 36 (16%) h a d normal QRS a n d a b n o r m a l T, and 53 (23%) h a d n o r m a l QRS and T p a t t e r n s .

Anterior Wall Infarction Patterns F o r t y p a t i e n t s whose E C G s and VCGs m e t s t a n d a r d c r i t e r i a for a n t e r i o r wall infarction, and whose coronary arteriograms showed s i g n i f i c a n t c o r o n a r y a r t e r y disease, u n d e r went ventriculography. Antero-apical asynergy, entirely approp r i a t e to t h e E C G - V C G p a t t e r n observed, was seen in 21 of the 40 p a t i e n t s (52%) (Table I). H o w e v e r , 8 p a t i e n t s (20%) d e m o n s t r a t e d perfectly n o r m a l left v e n t r i c u l a r contractile patterns. In 10 p a t i e n t s (25%) infero-posterior a s y n e r g y was p r e s e n t in addition to t h e expected a n t e r o - a p i c a l contractile defect. In a single p a t i e n t (2.5%) o n l y isolated inferop o s t e r i o r a s y n e r g y was d e m o n s t r a t e d b y a v e n t r i c u l o g r a m while t h e antero-apical region was e n t i r e l y n o r m a l . A v e r a g e c o r o n a r y a r t e r y d i s e a s e score in t h e s u b g r o u p s described above is also p r e s e n t e d in T a b l e I. E i g h t p a t i e n t s w i t h s y n e r g y had a n a v e r a g e c o r o n a r y disease score of 7.2 in c o n t r a s t to 8.4, 11.0 and 10.2 for the p a t i e n t s w i t h anteroapical, infero-posterior and combined a s y n e r g y respectively. T h e s e v e r i t y of individual vessel i n v o l v e m e n t shows the m o s t sev e r e l y diseased vessel for t h e a n t e r i o r wall i n f a r c t i o n group to be t h e left a n t e r i o r descending a r t e r y w i t h a n a v e r a g e score of 4.6. Single vessel disease occurred in 16 p a t i e n t s , double in 16 and triple disease in 8.

Inferior Wall Infarction Pattern F o r t y - f i v e p a t i e n t s h a d ECGs and VCGs which satisfied s t a n d a r d c r i t e r i a for inferior wall i n f a r c t i o n (Table II). Of these, 25 (55%) p r e s e n t e d left v e n t r i c u l a r a s y n e r g y isolated to t h e infero-posterior wall. This r e p r e s e n t e d "bullseye" a c c u r a c y of prediction. H o w e v e r , 9 J. ELECTROCARDIOLOGY. VOL. 8. NO. 4_ 1~75

337

CAD AND ECG-VCG PATTERNS

TABLE I Ventriculographic and Coronary Artery Data in Patients with Anterior Myocardial Infarction Patterns on ECG and VCG AMI

40 Cases

//Pts.

%

S

D

T

Av. Score

RCA

LAD

LCA

8

20

4

4

-

7.2

2.5

3.6

1.1

Asynergy A-AP

21

52

10

7

4

8.4

2.3

5.1

1.1

Asynergy A-AP+lnf-Post

10

25

2

4

4

10.2

3.1

4.9

2.2

1

3

-

1

-

11.0

5.0

0

6.0

16

16

8

9.0

2.9

4.6

1.5

Synergy

Asynergy Inf-Post TOTAL

40

AMI = anterior myocardial infarction, A-AP = antero-apical, Inf. = inferior, Post = posterior, S = single vessel disease,

D = double vessel disease, T = triple vessel disease, AV. Score = the sum of scores of the 3 major coronary arteries as defined in the methods section, RCA = disease score in the right coronary artery, LAD = disease score in the left anterior descending artery, LCA = disease score in the left circumflex artery.

TABLE 2 Ventriculographic and Coronary Artery Data in Patients with Inferior Myocardial Infarction Patterns on ECG and VCG IMI

45 Cases

# Pts.

%

S

D

Synergy

9

20

7

1

Asynergy A-AP

3

7

1

Asynergy A-AP+I nf-Post

8

18

Asynergy Inf-Post

25

55

TOTAL

45

Av. Score

RCA

LAD

LCA

1

6.6

3.1

2.7

1.0

0

2

10.0

3.0

4.0

3.0

2

3

3

10.0

5.1

2.6

2.7

6

9

10

10.0

4.7

2.3

3.1

16

13

16

9.6

4.3

2.3

2.6

p a t i e n t s of t h e 45 (20%) had normal left ventricular contractile patterns. In 8 patients (18%) antero-apical asynergy was present in a d d i t i o n to t h e e x p e c t e d i n f e r o - p o s t e r i o r asynergy. In 3 other patients (7%) the contractile pattern of the infero-posterior wall was normal, but an isolated contractile defect was noted in the antero-apical area. The average coronary disease score for the 9 patients with normal left ventriculograms was 6.6, in contrast to 10.0 in the 36 others with various locations and degrees of left ventricular asynergy (Table II). The distribution of coronary artery disease and number of vessels involved is also demonstrated. The right coronary artery with an average score of 4.3 was the most severely diseased vessel.

T

ferior infarction (Table III). Fourteen of these (52%) demonstrated the expected ventriculographic pattern - - antero-apical as well as infero-posterior asynergy. However, 6 patients (22%) presented perfectly normal left ventriculograms. Four others (15%) showed only isolated antero-apical asynergy, and 3 (11%) showed only isolated inferior asynergy. The average coronary disease score for the 6 patients with left ventricular synergy was 10.5 as compared to 14.5, 12.0, and 11.7 in the 21 p a t i e n t s w i t h a n t e r o - a p i c a l , i n f e r o posterior, and combined a s y n e r g y respectively. The distribution of coronary artery disease severity and n u m b e r of vessels involved is also demonstrated.

Anterior Plus Inferior Infarction Pattern

Isolated Dorsal Wall Myocardial Infarction Pattern

Twenty-seven patients met standard ECG-VCG criteria for anterior as well as in-

Twelve patients met stringent criteria (see Methods) for isolated dorsal wall myocardial

J. ELECTROCARDIOLOGY, VOL. 8, NO. 4, 1975

338

HILSENRATH ET AL

TABLE 3 Ventriculographic and Coronary Artery Data in Patients with Anterior Plus Inferior Myocardial Infarction Patterns on ECG and VCG AMI + IMI

27 Cases

# Pts.

%

S

D

Synergy

6

22

1

2

Asynergy A-AP

4

15

2

14

52

2

3

11

Asynergy A-AP+lnf-Post Asynergy I nf-Post TOTAL

-

27

5

Av. Score

RCA

LAD

LCA

3

10.5

4.5

3.0

3.0

2

2

14.5

5.0

4.7

4.7

5

7

11.7

3.8

4.9

2.9

2

1

12.0

5.0

5.0

3.0

11

13

11.8

4.3

4.4

3.1

infarction. Only 2 patients (6%) demonstrated isolated contractile defects in the inferoposterior segment of the left ventricle in the right anterior oblique view. Two additional patients presented an inappropriate contractile defect in the antero-apical area. The remaining 8 patients (68%) all presented with normal left ventricular contractile function. The results in this group were so striking and so unexpected as to require a major rethinking of the ECG-VCG problem of "true" dorsal wall myocardial infarction. The data in 12 p a t i e n t s w i t h dorsal wall ECG-VCG infarction patterns is included in Table 4. Our thoughts on the significance of the results of this group, and a possible explanation, are presented in the discussion section.

T

ing any criteria for myocardial infarction. Of these 17 patients, 11 (69%) had normal left ventricular contractile patterns. However, 3 (15%) had localized infero-posterior asynergy, a n d one p r e s e n t e d w i t h a n t e r o - a p i c a l asynergy. Two additional patients (12%) pres e n t e d left v e n t r i c u l o g r a m s i n d i c a t i n g infero-posterior as well as antero-apical asynergy (Table 5). In the group with synergy, the average coronary disease score was 8.6 in contrast to 14, 10.0 and 9.5 for patients with anteroapical, infero-posterior and combined asynergy. Distribution of coronary artery disease and n u m b e r of vessels involved is demonstrated in Table 5.

QRS Normal, T Abnormal Pattern Thirty-six patients presented normal QRS complexes but abnormal T-waves, suggesting ischemia in various myocardial areas, or T-wave abnormalities due to drugs. Of these

Left Ventricular Hypertrophy Pattern Seventeen patients presented ECGs and VCGs satisfying standard criteria for left ventricular hypertrophy, but without meet-

TABLE 4 Ventriculographic and Coronary Artery Data in Patients with Dorsal Myocardial Infarction Patterns on ECG and VCG # Pts.

%

S

D

Synergy

8

68

4

2

Asynergy A-AP

2

16

Asynergy A-AP+I nf-Post

0

-

Asynergy Inf-Post

2

4

DMI

12 Cases

TOTAL

12

T

Av. Score

RCA

LAD

LCA

2

8.2

2.9

2.4

3.0

1

3

10.0

4.5

3.0

2.8

3

5

9.4

3.4

2.6

2.9

16

J. ELECTROCARDIOLOGY. VOL. 8. NO. 4. 1975

CAD AND ECG-VCG PATTERNS

339

TABLE 5 Ventriculographic and Coronary Artery Data in Patients with Left Ventricular Hypertrophy Patterns on ECG and VCG LVH

17 Cases

H Pts.

%

S

D

Synergy

11

65

5

1

Asynergy

1

6

-

Asynergy A-AP+I nf-Post

2

12

1

Asynergy Inf-Post

3

17

TOTAL

Av. Score

RCA

LAD

LCA

5

8.6

3.5

3.0

2.2

-

1

14.0

5

5

4

-

1

9.5

4

3.5

2.0

1

2

10.0

4.3

2.3

3.3

2

9

9.4

3.8

3.1

2.5

-

17

6

36 patients, 24 (66%) had normal left ventricular contractile patterns. Ten patients (28%) had an antero-apical asynergy and one patient had localized infero-posterior asynergy. In an a d d i t i o n a l s i n g l e p a t i e n t , inferoposterior as well as antero-apical asynergy was present (Fig. 6). The average coronary artery disease score for the 24 patients with synergy was 7.8 as compared to 9.3 for the patients with anteroapical asynergy.

T

bined a s y n e r g y respectively. The anteroapical asynergy group demonstrated average coronary disease scores similar to the group with ventricular synergy.

Ventriculographic Pattern Of the 230 patients in this study, in 104 with synergy, the average coronary artery disease score was 7.9 (Table VIII), in contrast to 9.2, 10.9 and 10.9 for patients with anteroapical, infero-posterior or combined asynergy respectively. Single vessel disease occurred in 49 (47%) of patients with synergistic ventriculograms b u t in only 7 (18%) and 7 (19%) with antero-apical plus infero-posterior and infero-posterior asynergy respectively. On the other hand, significant (greater than 50% occlusion) multiple vessel disease occurred more frequently with asynergy.

QRS-T Normal Pattern Fifty-three patients presented with completely normal ECGs and VCGs. Of these 53, 38 (72%) had normal left ventricular contractile patterns (Fig. 7). However, 9 patients (17%) presented with antero-apical asynergy, and 4 (7%) showed isolated infero-posterior asynergy. In two patients, infero-posterior as well as anteroapical asynergy were demonstrated by ventriculography. The overall coronary disease score was 7.8 for the 38 patients with synergy, and 7.4, 11.0 and 10.0 for patients with antero-apical, infero-posterior and com-

DISCUSSION The present study has certain limitations inherent in the method utilized to evaluate c o n t r a c t i l e p a t t e r n . T h e left v e n t r i c u l a r angiograms were performed only in the right

TABLE 6 Ventriculographic and Coronary Artery Data in Patients with Normal QRS and Abnormal T Patterns on ECG and VCG QRS NML - T Abnml

# Pts.

%

S

D

Synergy

24

66

8

10

6

Asynergy A-AP

10

28

2

5

Asynergy A-AP+I nf-Post

1

3

-

-

Asynergy Inf-Post

1

3

TOTAL .I I:=1I:=~TI:::I(hr,ARRI(31 (3~Y VOI

36

T

Av. Score

RCA

LAD

LCA

7.8

3.3

2.2

2.3

3

9.3

2.6

3.9

2.6

1

13.0

3,0

5.0

5.0

1

-

-

4.0

4.0

0

0

11

15

10

8.9

3,2

2.8

2.5

R NO_ 4 1.q75

340

H I L S E N R A T H ET A L

TABLE 7 Ventriculographic and Coronary Artery Data in Patients with Normal QRS + T Patterns on ECG and VCG QRS - T Nml

Synergy

# Pts.

%

S

D

T

Av. Score

RCA

LAD

LCA

38

72

20

10

8

7.8

3.3

2.6

1.9

Asynergy A-AP

9

17

4

3

2

7.4

2.6

3.1)

1.8

Asynergy A-AP+I nf-Post

2

4

-

2

-

11.0

2.0

5.0

4.0

Asynergy Inf-Post

4

7

-

3

1

10.0

4.5

2.1)

4.2

24

18

11

8.1

3.2

2.7

2.2

TOTAL

53

anterior oblique projection and as such only the anterior, apical and inferior walls could be evaluated. Biplane cineangiography would probably have been more appropriate for the present study, since this would have afforded the opportunity to evaluate the posterolateral and septal walls of the left ventricle. Thus, the correlation of the ECG and VCG with the left ventricular contractile pattern may underestimate the true relationship. It should be pointed out that biplane angiographic studies in other patients indicate that septal wall abnormalities are always associated with contractile abnormalities of the anterior or apical wall. The patients in the present series represent a select group since all were referred because of angina pectoris. All drugs were discontinued for at least 24 hours prior to the angiographic studies and no patients had any ang i n a p e c t o r i s before or d u r i n g t h e left ventricular angiographic study. Previous reports have indicated good correlations between ECG-VCG infarction patt e r n s and regional a b n o r m a l i t i e s of left ventricular systolic motion. ~,1~13,25 However, only about 50% of our patients with infarction patterns have ventriculographic abnormalities which corresponded closely to the ECGVCG patterns. About 20% of the patients with infarction patterns proved to have perfectly n o r m a l v e n t r i c u l o g r a m s . These areas of infarction may have resulted in ventricular contractile defects so small as to be undetectable by present ventriculographic techniques. The possibility of "pseudo infarction," as seen in patients with valvular and primary myocardial disease 1-z seems less likely, as such a diagnosis would be ruled out by the hemodynamic data. In the remaining 25-30% of patients with ECG-VCG infarction patterns, the ventriculograms displayed either more extensive deficits t h a n anticipated or ventriculographic

abnormalities were noted in areas not corresponding to the areas of infarction on ECGVCG. For example, 3 (7%) of patients with inferior wall infarction p a t t e r n s demonstrated only antero-apical asynergy by ventriculography. In the case of ECG-VCG patterns of left ventricular hypertrophy, normal QRS with abnormal T, or normal QRS with normal T, the correlation with expected left ventricular synergy was better. About 70% of patients in these groups did indeed have perfectly normal left ventricular contractile patterns. However, the remaining 30% displayed either single or multiple areas of poor left ventricular contractility, not predictable from the ECG or the VCG. Two explanations seem possible in u n d e r s t a n d i n g v e n t r i c u l a r asynergy inappropriate to the corresponding QRS infarction pattern, or in patients with no infarction patterns at all. First, previous infarction may indeed have taken place affecting electrically silent areas of the left ventricle so that abnormal systolic motion results despite QRS complexes not exhibiting characteristic signs of infarction. This seems unlikely in view of the large areas of asynergy observed in these patients. Gunnar et a114 have shown that infarctions on post mortem examination may be expected to result in ECG-VCG QRS abnormalities in 92% of cases. Second, the area of contractile defect may be secondary to myocardial ischemia and thus be potentially reversible with improved myocardial perfusion 15 as obtained by saphenous vein bypass grafting. ~6'~7 Such temporary ventricular asynergy has been observed during anginal attacks, either spontaneous is induced by coronary dye injection TM or by atrial pacing. 2~ The coronary artery grading system used s permitted us to evaluate the severity of coronary artery obstruction in the presence or absence of ventricular contractile defects. In J. ELECTROCARDIOLOGY, VOL. 8. NO. 4. 1975

CAD AND ECG-VCG PATTERNS

341

TABLE 8 Relation of Veotriculogram to Coronary Artery DiseaseSeverity ECG-VCG

# Pts.

Av. Score

S

D

T

Synergy

104

7.9

49 (47%)

30 (29%)

25 (24%)

Asynergy A-AP

50

9.2

15 (30%)

18 (36%)

17 (34%)

Asynergy A-AP+lnf-Post

39

10.9

7 (18%)

15 (38%)

17 (44%)

Asynergy Inf-Post

37

10.9

7 (19%)

16 (43%)

14 (38%)

78 (34%)

79 (34%)

73 (32%)

TOTAL

230

each group studied, except one, the overall coronary artery disease score was lowest in the patients with synergy and highest in patients with left ventricular contractile defects (Tables I-VIII). For all 104 patients with synergy, regardless of ECG or VCG patterns, the average coronary score was 7.9, while in the 126 patients with asynergy, the average scores ranged from 9.2 to 10.9 (Table VIII). In individual patients, however, the coronary disease score itself is not a reliable predictor of asynergy. Nevertheless, patients with anterior, anterior plus inferior, and inferior infarction patterns have severe disease of the appropriate arteries in all cases as corroborated by high coronary artery disease scores (Tables I-VIII), no matter what the contractile pattern on ventriculography. One patient with an anterior infarction pattern had a normal LAD but severely diseased RCA and LCA (Table I). Single vessel disease is far more likely in p a t i e n t s w i t h s y n e r g y (47%) t h a n w i t h asynergy (18-30%). Furthermore, single vessel disease is less likely to be associated with an infarction pattern (Tables I-VII) than with normal QRS complexes. Still, significant (greater than 50% occlusion) single vessel disease is not uncommon with anterior wall infarction patterns, 16/40 (40%), and 16/45 (36%) with inferior infarction patterns, but in only 3/27 (11%) with combined anterior plus inferior infarction patterns. Unexpected results were found in the ventriculograms of patients whose ECG-VCG records were consistent with true dorsal myocardial infarction. Only 2 of the 12 patients studied demonstrated infero-posterior asynergy, as might be predicted from the ECG and VCG (Table IV). The majority of patients (68%) presented with perfectly normal left ventricular contractile patterns. Clearly, some other explanation for prominent anterior QRS forces in patients with severe I r-I ~ ' ( " T l ~ ( ' ~ ( h A l : i l h l ( h l

N(~V

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coronary disease is needed besides the conventional interpretation of true posterior infarction. In two very striking cases, to be reported separately, an ECG-VCG picture of true dorsal infarction was presented with classical a n g i n a pectoris. The coronary angiograms showed only localized disease in the anterior descending artery, and ventriculograms demonstrated only anterior asynergy. After saphenous bypass grafting in one p a t i e n t , an e x t e n s i v e a n t e r o l a t e r a l infarction developed, while in the other a s p o n t a n e o u s closure of the a n t e r i o r descending artery developed, producing extensive antero-septal myocardial infarction. In both cases, prominent right precordial R waves disappeared while anterior infarction patterns resulted. Clearly, the patients did not have right ventricular hypertrophy which may also result in prominent anterior forces. Dorsal infarction likewise was not responsible. Since conduction delays may shift QRS forces left and superior (as in left anterior hemiblock), right and inferior (as in left posterior hemiblock21), markedly posterior (as in left bundle branch block), and rightward (as in right bundle branch block22), we consider the possibility that the anterior shift seen in some of our patients may be the result of localized anterior conduction delay. Some experimental and anatomical evidence supports this view. Van Dam et a123 have demonstrated localized conduction delay in the hypertrophied septum of patients with hypertrophic subaortic stenosis, and they believe that such delay is in fact responsible for the prominent early right anterior QRS forces seen in many of these patients. Demoulen et a124 have demonstrated anatomically that the left conducting system is more complex than a simple bifascicular diagram would indicate, and that strictly anterior fascicles are indeed present in many patients. It is our view that ischemia of these anterior fascicles of the left bundle system may occasionally result in

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conduction delay in the most ant er i or portion of th e left v e n t r i c u l a r free wall with the r e s u l t i n g shift of QRS anterior and left. Such a shift would result in prominent precordial R waves and a m a r k e d l y anterior position of the QRS loop in the horizontal plane, simulating the p a t t e r n of "dorsal infarction" or right v e n t r i c u l a r hypertrophy.

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J. ELECTROCARDIOLOGY, VOL. 8, NO. 4. 1975