Impaired chronotropic response limits exercise tolerance in peritoneal dialysis and renal transplant patients

Abstract

BACKGROUND: Chronotropic incompetence (CI), defined as blunted increase in heart rate (HR) during exercise, has been accepted as an independent predictor of cardiovascular mortality. Little is known about its prevalence in peritoneal dialysis (PD) and renal transplant (RT) patients. This study aimed to investigate the prevalence of CI and its relationships with exercise intolerance in these patients. METHODS: Ambulatory PD and RT patients were recruited for treadmill stress test using modified Bruce protocol. Exercise duration and HR response was recorded. Maximum age-predicted HR was defined as (220-age). Heart rate reserve was defined as difference between peak heart rate achieved during exercise and resting heart rate. Chronotropic response (CR) to exercise was evaluated by the percentage of heart rate reserve ([peak HR-resting HR/maximal age predicted HR-resting HR]x100%). RESULTS: 86 patients (mean age 51.72±8.78 years, male 53.5%) were included in this study. RT patients had significantly longer exercise duration than PD patients (10.01±3.59 min Vs 6.26±3.16 min, P=0.000). Both PD and RT patients demonstrated blunted HR response to exercise. PD patients had significantly lower maximum heart rate than RT patients (75.34±13.67% Vs 86.57±23.56% of age-predicted HR respectively, p=0.009). CR was also significantly lower in PD than RT patients (58.64±24.11% Vs 79.73±43.54%, p=0.008). CI (i.e. CR<80%) was noted in 28 (64%) PD and 15 (36%) RT patients respectively. CONCLUSIONS: Chronotropic incompetence was more prevalent in PD than RT patients and such difference might account for the discrepancy in their exercise tolerance.