Clinical significance of exercise-induced bundle branch block.

To evaluate the diagnostic significance and long-term follow-up data of patients with exercise-induced bundle branch block (BBB), 10,176 consecutive patients' exercise test data were reviewed and 50 patients found to have exercise-induced BBB. Clinical, exercise test and arteriographic data were analyzed along with follow-up data during a mean of 43 months. Of the 50 patients, 37 had exercise-induced left BBB and 13 had exercise-induced right BBB. Significant coronary artery disease (CAD) was diagnosed in 26 of 37 patients (70%) with exercise-induced left BBB and in all 13 patients (100%) with exercise-induced right BBB. In patients who underwent coronary arteriography, data demonstrated a high prevalence of proximal left anterior descending disease (17 of 20, 85%). Follow-up data revealed that exercise-induced BBB was associated with a 36% (18 of 50) incidence of coronary events, including 16 patients who underwent coronary artery bypass grafting and 2 hospitalized for congestive heart failure. Results indicated that exercise-induced BBB was infrequent and occurred primarily in association with CAD, had a high prevalence of proximal left anterior CAD, infrequently had similar onset and offset heart rates, was reproducible and associated with a greater incidence of coronary artery bypass grafting than had been previously reported, although the incidence of cardiac events was similar to those investigations.