Cardiomyoplasty is a surgical procedure aimed at assisting the left ventricle during ejection. We describe the long-term effects of cardiomyoplasty on peak exercise capacity, with serial assessments for up to 3 years after operation. Sixteen patients (12 in New York Heart Association class III and 4 in class IV) were enrolled. The mean left ventricular ejection fraction was 18 +/- 8%. Bicycle exercise tests with respiratory gas analysis were performed preoperatively and 6, 12, 18, 24, and 36 months after operation. Mean follow-up was 12 +/- 5 months (range 6 to 24). At 6 months, peak oxygen consumption and the ventilatory threshold were unchanged (from 17.8 +/- 5.8 to 15.8 +/- 5.3 ml/min/kg, and from 12.1 +/- 2.7 to 11.4 +/- 3.4 ml/min/kg, respectively). Ventilation at 50 W, viewed as an index of polypnea at submaximal exercise, was also unchanged. Serial assessment of exercise capacity thereafter showed no changes. However, ejection fraction tended to increase from 18 +/- 8% to 21 +/- 9% (p=0.08) and 14 patients reported an improvement in their functional status, resulting in a significant change in New York Heart Association functional class (3.3 +/- 0.5 to 2.2 +/- 0.4 at 6 months and 2.4 +/- 0.4 at the last visit, p <0.005) and improvement in quality-of-life scores. Thus, cardiomyoplasty does not appear to increase peak exercise capacity in the long term, despite an improvement in the left ventricular ejection fraction. Symptoms and quality of life, however, appear to improve. This may be related in part to an insufficient number of assisted systoles during exercise, persistent deconditioning, or changes in pulmonary mechanics.