Ventricular endocardial leads in left bundle branch block and left ventricular hypertrophy: Correlation with the vectorcardiogram and electrocardiogram

1. (1) Thirty-one patients were studied by left endocardial and precordial leads, 14 with left ventricular hypertrophy, 5 with left ventricular hypertrophy and incomplete left bundle branch block, 2 with equivocal findings, 2 with complete left bundle branch block, and 8 with other diagnoses. 2. (2) The differentiation between left bundle branch block and left ventricular hypertrophy by the electrocardiogram and vectorcardiogram proved to be unsatisfactory in many cases. 3. (3) The endocardial lead appeared to be most useful in establishing the diagnosis of left bundle branch block when an initial positive deflection was demonstrated in the left ventricle.