Progression to complete atrioventricular block in a patient with bundle branch re-entry tachycardia.

A 38-year-old man with no significant structural heart disease suffered from one episode of wide QRS tachycardia. The electrocardiogram showed a PR interval of 0.20 second and a QRS duration of 0.10 second. His bundle recording revealed an HV interval of 90-100 ms. The tachycardia was inducible with programmed stimulation and displayed a QRS morphology of complete left bundle branch block. It was characterized by an atrioventricular dissociation, a cycle length of 280 ms, and an H deflection preceding each QRS complex. Pacing from the right ventricular apex at a cycle length of 270 ms entrained the tachycardia, while at a cycle length of 260 ms, the tachycardia was terminated. Four years later, the patient presented with complete atrioventricular block with a wide QRS escape rhythm. An electrophysiologic study conducted while he was in 1:1 atrioventricular conduction showed an HV interval of 100 ms. Second-degree infrahisian block developed at an atrial paced cycle length of 700 ms. There was no induction of tachycardia with programmed stimulation before or after isoproterenol. The patient was treated with an implantation of a permanent pacemaker.