Stress testing in patients one year after orthotopic cardiac transplantation

To evaluate the circulatory response of the denervated heart to exercise, the authors studied 15 patients with an orthotopic transplanted heart (TH). Mean age was 48 +/- 10 (range twenty-five to sixty-two) years. All patients underwent a symptom-limited bicycle stress testing following a continuous protocol increasing the work load by 30 watts every three minutes. Exercise test was performed 16 +/- 9 months after operation. Fifteen healthy subjects matched for age were used as the control group. There were significant differences (p less than 0.01) in heart rate, at rest, peak exercise, and at five minutes of the recovery period, in maximal oxygen consumption (VO2 max) and in duration of exercise between TH patients and controls. Synchronization between recipient and donor sinoatrial nodes was observed in 10 of 15 patients. A case of silent myocardial ischemia was also observed in a patient with vasculitis and acute rejection. In conclusion, the lack of neural control in TH patients allows them to maintain a normal resting cardiac output but precludes attaining a normal maximum oxygen uptake, despite a normal contractile state. The high resting heart rate due to parasympathetic denervation constitutes an important limiting factor for an adequate chronotropic reserve. Functional capacity of transplanted patients is slightly impaired, but it does not preclude a good quality of life.