Late complete atrioventricular block complicating radiofrequency catheter ablation of a left posteroseptal accessory pathway.

A patient with AV reentrant tachycardia underwent radiofrequency catheter ablation for interruption of a left posteroseptal accessory pathway (AP). During the RF current application, he developed transient complete left bundle branch block which lasted for 2 minutes. The following day the patient developed permanent complete AV block. This case indicates that great care should be taken when performing RF ablation for this AP site.