CLINICAL AND ELECTROCARDIOGRAPHIC CORRELATES OF EXERCISE-INDUCED ATRIAL-FIBRILLATION - A CASE-CONTROL STUDY

Clinical and electrocardiographic correlates of atrial fibrillation (AF) induced during routine exercise testing were examined in a case-control study. With the use of a prospective data base 11,730 consecutive exercise tests in 7,273 patients were reviewed. AF developed in 14 patients during exercise and in 9 patients during recovery (total incidence 0.3%). The mean age was 62 (range 36-76) years, and most patients were male (87%). AF was sustained (> 30 s) in 17 patients. The median duration of AF was 233 s. Atrial premature activity, including atrial tachycardia, often (13 patients) preceded AF. In 6 patients (26%) no structural heart disease was apparent. Compared with controls, matched for age, sex, and test indication, AF patients used less beta blockers (9 vs. 43%; p <0.05) and had a higher maximal heart rate (144 vs. 127 beats/min; p <0.05). Also, ischemic responses to exercise were observed more often in these patients (26 vs. 6%; p <0.05). These findings indicate that most patients with exercise-induced AF have associated cardiac disorders, foremost ischemic heart disease. In a subset of patients, however, symphathetic activation per se appears to play an important role.