The significance of an absent or a small initial positive deflection in the precordial lead

Abstract

1. 1. The initial positive deflection in the precordial lead (Q-wave of old, R-wave of new technique) was absent in 2.7 per cent of 4,500 consecutive hospital patients and was small (2 mm. or less) in 3.9 per cent. 2. 2. In two-thirds of the patients, absence of this deflection was associated with recent or old coronary thrombosis and anterior wall infarction, and in one-fifth, with coronary artery disease alone, with or without hypertension. 3. 3. The initial positive deflection was also absent in 14 cases diagnosed as acute and chronic glomerulonephritis, rheumatic and syphilitic valvular disease, pneumothorax, Graves' disease, and acute myocarditis. There was no evidence of myocardial infarction in these cases. 4. 4. In patients with an M or W-shaped QRS complex precordial leads obtained from other positions on the chest wall usually demonstrated absence of the initial positive deflection. This holds frequently when a large initial negative deflection precedes a large positive deflection. 5. 5. Absence of this deflection was permanent in the majority of cases even when an abnormal T 4 and abnormal standard leads returned to normal. 6. 6. Absence of the initial positive deflection was accompanied by an abnormal T 4 in 54 per cent of cases. 7. 7. Of the patients with a small initial positive deflection 7.5 per cent had no clinical evidence of cardiovascular disease. The remainder suffered from coronary thrombosis (29 per cent), coronary artery disease with or without hypertension (37 per cent), rheumatic valvular disease (17 per cent), miscellaneous heart involvement (12 per cent). These included cases of intraventricular or bundle-branch block. 8. 8. In only one-fifth of these patients was there an associated abnormal T-wave in the precordial lead. A small initial positive deflection was significant when followed by an intrinsic deflection of at least 10 mm. 9. 9. In a large group of cases with anterior wall infarction, diagnosed electrocardiographically or at autopsy, the initial positive deflection was absent in more than one-half, small in one-sixth, and normal in one-third. In posterior wall infarction this deflection was rarely absent but was frequently small. 10. 10. In 26 patients with a small initial positive deflection, myocardial infarction was found 15 times. Only one case showed normal heart muscle. 11. 11. Comparison of the ordinary method of recording the precordial lead with the “zero potential” method of Wilson revealed no practical advantage of the latter as far as diagnosis was concerned.