Stress Testing in Patients One Year After Orthotopic Cardiac Transplantation

Abstract

To evaluate the circulatory re sponse of the denervated heart to ex ercise, 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-lim ited 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 < 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 dura tion of exercise between TH patients and controls.

Synchronization between recipi ent and donor sinoatrial nodes was observed in 10 of 15 patients. A case of silent myocardial ischemia was also observed in a patient with vascu litis 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 nor mal maximum oxygen uptake, de spite a normal contractile state. The high resting heart rate due to para sympathetic 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.