Supraventricular tachyarrhythmia (SVT) is a common complication of coronary artery bypass grafting. Four hundred twenty-four cases of coronary artery bypass grafting were retrospectively reviewed and 64 patients (15%) were identified who had clinically significant SVT. Sixty randomly selected arrhythmia-free patients served as controls. The arrhythmia group differed from the control group in age (62 +/- 8 years vs 57 +/- 8 years p less than 0.0001), radiographic cardiomegaly (19 of 64 patients with arrhythmia vs 6 of 60 control subjects, p less than 0.01), and echocardiographic left atrial enlargement (16 of 38 vs 6 of 37 control subjects, p less than 0.025). No significant differences existed regarding sex of the patient, prior myocardial infarction, reduced ejection fraction, history of congestive heart failure, occurrence of perioperative myocardial infarction or pericarditis, or pump time. The relative risk of SVT developing in patients 60 years or older was 1.91; in patients 60 years or older with cardiomegaly, 2.39; in patients 60 years or older with left atrial enlargement, 3.29; and in patients 60 years or older with cardiomegaly and left atrial enlargement, 3.47. Thus, it may be possible to select patients at relatively higher risk of having SVT who could especially benefit from preventive measures.