[Reevaluation of the electrocardiographic criteria of left anterior hemiblock associated with lower infarction]

A vectocardiographic (VCG) study of 90 consecutive cases of acute inferior myocardial infarction (IMI) was carried out by Frank's method. The overall incidence of intraventricular block was 40% and that of left anterior hemiblock (LAH) 20% (18 cases). The ECG features of the 18 cases of LAH-acute IMI and of the 55 cases of isolated acute IMI were compared with those of 100 cases of confirmed chronic IMI comprising 50 cases of isolated infarction-LAH (on VCG) and with 50 cases of isolated LAH (clinical and VCG diagnosis). The incidence of the six following electrocardiographic criteria were studied: 1) terminal negative forces in Lead II and positive forces in AVR with left axis deviation 2) W-shaped appearances in Leads II and AVF, 3) initial notching in Leads II, III and AVF, 4) abnormal growth of the R wave from Lead II to Lead III, 5) combinations of the four preceding criteria taken two by two, 6) the association of 3 of the 4 preceding criteria (from 1 to 4).

A) Acute IMI: 1) isolated infarction: criteria 1 - 7%; 2 - 2%; 3 - 5%; 4 - 2%; 5 - 4%; 6 - 0%; 2) IMI - LAH: 33%, 56%, 61%, 17%, 50%, 6%, respectively. B) Chronic IMI: 1) isolated infarction: criteria 1 - 4%; 2 - 8%; 3 - 6%; 4 - 10%; 5 - 8%; 6 - 0%; 2) IMI - LAH: 72%, 22%, 60%, 74%, 42%, 44%, respectively. C) Isolated LAH: criteria 1 - 80%; 2 - 0%; 3 - 4%; 4 - 20%; 5 - 20%; 6 - 0%.

Some of the ECG criteria studied were relatively sensitive and were suggestive of the association IMI - LAH, but VCG was much more sensitive and specific. Therefore, the incidence of LAH associated with acute IMI is probably underestimated by ECG alone.