Resynchronization in a patient with normal systolic function & intermittent left bundle branch block with recurrent left ventricular failure.

A 50 year old lady presented with recurrent hospitalizations for Left ventricular failure (LVF) associated with rate related left bundle branch block (LBBB). Though the baseline ECG at rates less than 90bpm demonstrated narrow QRS, normal LV systolic function and no LV dysynchrony, at rates greater than 90bpm, LBBB was noted with concurrent LV dyssynchrony. After multiple hospitalizations with LVF, as a last resort, cardiac resynchronization therapy (CRT) was performed. At 22 months' follow up the patient continues to be asymptomatic.