Transient left bundle branch block and intraventricular dyssynchrony as a cause of reversible left ventricular dysfunction: The "in vivo" documentation of spontaneous electrical remodeling.

Spontaneous resolution of non-rate-dependent left bundle branch block (LBBB) has been rarely reported. We present the case of a 74-year-old woman admitted with pulmonary edema, a newly diagnosed LBBB and severe left ventricular (LV) dysfunction. Five months later, the patient was asymptomatic, the ECG recording showed complete regression of the LBBB to narrow QRS and LV function completely recovered. However, at one-year follow-up LBBB reappeared together with mild LV dysfunction. Spontaneous resolution of LBBB may be responsible for LV electrical and mechanical reverse remodeling in dyssynchronopathies.