Ventricular dysrhythmias in patients undergoing coronary artery bypass graft surgery: Incidence, characteristics, and prognostic importance

Abstract

To determine the incidence and characteristics of ventricular dysrhythmias (premature ventricular contractions >30/min, ventricular tachycardia ≥3 beats, and ventricular fibrillation) and whether a relationship exists between ventricular tachycardia and myocardial ischemia in patients undergoing coronary artery bypass graft surgery, we continuously monitored 50 patients for 10 perioperative days using two-lead electrocardiography. Electrocardiographic changes consistent with ischemia were defined as a reversible ST depression ≥1.0 mm, or ST elevation ≥2.0 mm from baseline, lasting at least 1 minute. Ventricular dysrhythmias developed in 10% of patients preoperatively and in 16% intraoperatively before bypass surgery. The highest incidence occurred postoperatively, with ventricular dysrhythmias developing in 66% of patlents (22% to 44% of patients on any postoperative day 0 to 7). Premature ventricular contractions were >30/hr in 6% of patients preoperatively, in 8% intraoperatively before bypass, and in 34% postoperatively (6% to 23% of patients on any postoperative day). Twenty-nine patients (58%) developed 76 verified episodes of ≥3 beats of ventricular tachycardia. Ventricular tachycardia occurred in 6% of patients preoperatively (four episodes), in 8% of patients intraoperatively prior to bypass (four episodes), and 54% of patients postoperatively (5% to 21% on any postoperative day). No patient developed ventricular fibrillation. All postoperative ventricular tachycardia episodes (after tracheal extubation) were asymptomatic. Postoperatively, 48% of patients developed ischemia, compared with 12% preoperatively and 10% intraoperatively before bypass surgery. Only 5 of 68 (7%) postoperative ventricular tachycardia episodes occurred within 3 hours of an ischemic episode. None of the five adverse cardiac outcomes were preceded by ventricular tachycardia. We conclude that perioperative ventricular dysrhythmias are common and sllent, and are most prevalent in the postoperative period; however, postoperative ventricular tachycardia usually is not associated with myocardial ischemia or with an adverse cardiac outcome.