The influence of 45 variables on risk of postoperative supraventricular tachycardia was evaluated by univariate and multivariate analysis of data from 800 consecutive patients who underwent isolated coronary artery bypass during a 6-year interval. Postoperative supraventricular arrhythmias occurred in 186 patients (23%) but did not contribute to any of the six early deaths (30-day mortality rate, 0.8%). Mean (+/- standard deviation) length of hospital stay was longer (9.8 +/- 5.7 versus 8.3 +/- 3.5 days; p less than 0.0001) and mean age was older (65 versus 60 years; p less than 0.002) in patients with postoperative supraventricular tachycardia than in those with regular rhythm. Risk of supraventricular tachycardia was increased in patients with a history of atrial arrhythmias (45% versus 22%; p less than 0.002) or premature atrial contractions on the preoperative electrocardiogram (48% versus 22%; p less than 0.002). Multiple logistic regression analysis identified age 65 years or more, history of atrial arrhythmia or preoperative premature atrial contractions, and preoperative left ventricular end-diastolic pressure 20 mm Hg or more as independent predictors of postoperative supraventricular tachycardia. Six percent of patients converted to sinus rhythm spontaneously; 82% of patients converted within 1.1 +/- 1.9 days after onset of supraventricular tachycardia on treatment with digoxin or beta-adrenergic blocking drugs or both. Only 10% of patients with supraventricular tachycardia required electrical cardioversion. We conclude that the risk of supraventricular tachycardia after coronary artery bypass is influenced by patient-related variables and is effectively managed by conventional therapy. Prophylactic treatment should be reserved for elderly patients, especially those who have atrial arrhythmias or have preoperative left ventricular end-diastolic pressure 20 mm Hg or more.