Effect of intermittent left bundle branch block on left ventricular performance in the normal heart.

The effect of left bundle branch block on left ventricular performance was studied in a patient with rate-dependent left bundle branch block and an otherwise normal heart. The timing of left heart events, hemodynamic pressures and indexes of left ventricular contractility were determined during normal intraventricular conduction and during left bundle branch block. The results indicate that in the normal heart left bundle branch block has no significant effect on left ventricular performance.