The ergometric test after a heart transplant: its usefulness and limits

Aim of this study was to analyze the cardiovascular response to graded physical exercise in patients who have undergone cardiac transplantation and to assess the ability of exercise stress testing in early detection of coronary artery disease. We studied 114 transplanted subjects (100 men and 14 women, mean age 46.6 +/- 11.3 years), who performed exercise stress testing 6 months after bypass and then every 6 (+/- 1) months during a 5-year follow-up. Variations of hearth rate (HR), systolic blood pressure (SBP), heart rate-pressure product (RPP) values and exercise stress tolerance were studied both in basal and maximum workload conditions. Mean HR values at basal conditions (103.9 +/- 11.3 b/min at 6 months and 89 +/- 12.7 b/min at 60 months, p < 0.05) and maximum workload tolerance (67.7 +/- 20.4 W at 6 months and 100 +/- 17 W at 60 months, p < 0.05) were significantly different at the beginning and at the end of follow-up. SBP values both at basal conditions and at peak exercise had always been constant. Exercise was stopped for leg muscle fatigue in 92% and dyspnea in 7% of the subjects; isolated T-wave and ST segment changes were found in 29.8% and in 10.5% of the patients respectively, whereas 11.4% exhibited both ST-T variations. Angiographic examination (performed in 80/114 patients) showed significant coronary disease (stenosis > 50%) in 8, coronary atherosclerosis (CAD) of minor degree in 4 and provoked spasm in 2 subjects. In this subgroup exercise stress testing induced ischemic ECG changes (ST segment depression > or = 1 mm) without angina in 1 patient, ST-T segment variations only in 5 and no electrocardiographic alterations (negative tests) in 2 patients. Four subjects with CAD and 1 with coronary spasm induced by angiography showed isolated ST segment and T-wave changes. Our work demonstrated that exercise stress testing plays a relevant role in the study of the denervated heart response to dynamic exercise. The rise in workload tolerated, observed in our population, seems to be related to time elapsed from surgery, improvement in clinical conditions, psychological stability and patient's confidence in his own abilities. The tolerance to exercise 6 months after graft seems to predict the quality of performance in the following tests. Our angiographic results reveal a low sensitivity of the exercise stress test in detecting CAD in this population according to traditional electrocardiographic criteria for myocardial ischemia