EXERCISE-INDUCED 2ND-DEGREE ATRIOVENTRICULAR-BLOCK

In this report we describe 2 patients with exercise-induced, second-de gree atrioventricular (AV) block. Case 1 was a 49-year-old man with no rmal AV conduction at rest but who developed dyspnea on exertion. Trea dmill testing showed an exercise-induced 2:1 AV block. Electrophysiolo gic study (EPS) demonstrated rate-dependent, presumably intrahissian, AV block. Case 2 was a 31-year-old woman with first-degree AV block an d complete right bundle branch block with dyspnea on exertion and occa sional syncope. She had twice undergone surgical patch closure of an o stium primum atrial septal defect. Exercise testing induced type II se cond-degree AV block. Atrial pacing during EPS did not disclose rate-d ependent type II AV block, but disopyramide induced second-degree AV b lock.