Coexistence of a bradycardia- and tachycardia-dependent bundle branch block.

Aberrant ventricular conduction is a rare phenomenon as compared with the more frequently occurring antrioventricular conduction disturbances. It leads to widening of the QRS complex, which is either due to a complete or functional block in one of the bundle branches or a block within the intramyocardial conduction system itself. Mechanisms that are potentially involved in the genesis of aberrant ventricular conduction are sudden shortening of cycle length (tachycardia-dependent phase III), antegrade block with retrograde concealed conduction, or bradycardia-dependent block (enhanced phase IV). In this paper, we present a patient with aberrant ventricular conduction with the occurrence of a tachycardia-dependent, as well as a bradycardia-dependent bundle branch block, which is an even rarer phenomenon.