Effects of Left Bundle Branch Block on Left Ventricular Function in Apparently Normal Subjects

To determine the independent effects of left bundle branch block (LBBB) on global and regional left ventricular (LV) function we performed equilibrium radionuclide angiocardiography at rest in 3 patients with chronic LBBB (group I, mean age 53.6 years and in 6 patients with intermittent LBBB (group II, mean age 41.5 years). All patients were judged to have an apparently normal heart. In 2 of 3 patients of group I a LV ejection fraction lower than 50% was observed, and in all 3 patients septal motion abnormalities were present. In all patients of group II the global LV ejection fraction was normal during normal conduction and decreased during LBBB; the inferoapical regional ejection fraction decreased in 5 of 6 cases and the posterolateral regional ejection fraction in 3 of 6 cases. Moreover, septal hypokinesis was observed both during normal and abnormal conduction in all group II patients. These findings seem to confirm that LBBB, chronic or intermittent, is able to deteriorate LV performance at rest, even in patients with an otherwise normal heart.