PROGRESSION TO COMPLETE ATRIOVENTRICULAR-BLOCK IN A PATIENT WITH BUNDLE-BRANCH REENTRY TACHYCARDIA

A 38-year-old man with no significant structural heart disease suffere d from one episode of wide QRS tachycardia. The electrocardiogram show ed 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 tachycardi a was inducible with programmed stimulation and displayed a QRS morpho logy of complete left bundle branch block. It was characterized by an atrioventricular dissociation, a cycle length of 280 ms, and an H defl ection preceding each QRS complex. Pacing from the right ventricular a pex at a cycle length of 270 ms entrained the tachycardia, while at a cycle length of 260 ms, the tachycardia was terminated. Four years lat er, 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 m s. Second-degree infrahisian block developed at an atrial paced cycle length of 700 ms. There was no induction of tachycardia with programme d stimulation before or after isoproterenol. The patient was treated w ith an implantation of a permanent pacemaker.