In order to evaluate the effect of aortic valve replacement on the incidence of ventricular arrhythmias in patients with aortic valve disease, 24-hour ambulatory electrocardiographic recordings were obtained before surgery in 96 patients without coronary artery disease (aortic stenosis n = 50, combined aortic stenosis and regurgitation n = 19 and aortic regurgitation n = 27). Following aortic valve replacement, repeat recordings were obtained after 13 +/- 4 days and 18 +/- 7 months. Ventricular arrhythmias were in all cases classified according to Lown and were compared with clinical, echocardiographic and hemodynamic data. Preoperatively, ventricular premature beats were observed in 85 patients (89%) and were frequent (greater than 30 ventricular premature beats/hour) in 20 (21%). Multiformity was found in 27 (28%), couplets in 18 (19%) and ventricular tachycardia in 11 (11.5%). The occurrence of ventricular arrhythmias was not related to the type or severity of valve lesions. Patients with severe ventricular arrhythmias (Lown class 3 or 4: 37%) had a greater thickness of their interventricular septum 13.9 +/- 2.5 mm, vs 11.7 +/- 2.6 (p less than 0.05); a higher LV mass 176 +/- 34 g/m2, vs 134 +/- 39 (p less than 0.05) and a lower left ventricular ejection fraction 47 +/- 12%, vs 57 +/- 11, (p less than 0.01). Two weeks postoperatively, the incidence and severity of ventricular arrhythmias had increased: ventricular premature beats were noted in 92% and were severe in 50%. No correlation was found between ventricular arrhythmias and preoperative or operative data. Eighteen months after surgery, ventricular premature beats were still observed in 81% of patients but remained frequent in 7% only. Severe ventricular arrhythmias were noted in 27%. Patients with severe ventricular arrhythmias had at the time of this late recording a lower radionuclide left ventricular ejection fraction 57 +/- 14%, vs 73 +/- 9 (p less than 0.02) and a higher enddiastolic diameter 63 +/- 15 mm, vs 48 +/- 7, (p less than 0.01). This study indicates that ventricular arrhythmias are common in patients with aortic valve disease. The severity of arrhythmias is influenced by the LV consequences of valve lesion both pre- and late postoperatively. The frequency and severity of ventricular arrhythmias increase early after surgery and do not correlate with preoperative or operative data.