When the rate of supraventricular impulses arriving at the AV node or ventricle is less than the intrinsic rate of the ectopic pacemaker, a ventricular escape beat may occur.  The QRS complexes of a ventricular escape beat are broad (≥ 120 ms) and can have a LBBB or RBBB morphology at a rate of 20-40 bpm.

12 Lead EKG Title