Chronotropic competence in endurance trained heart transplant recipients: heart rate is not limiting factor for exercise capacity

Objectives. The purpose of this study was to show that the chronotropic potential of the well trained heart transplant recipient (HTR) does not limit exercise capacity. Background. Chronotropic incompetence is considered to be the main limiting factor of the functional capacity of heart transplant recipients. However, no systematic study had been published on patients who had spontaneously undergone heavy endurance training for several years. Methods. Heart rate (HR) and respiratory gas exchanges (VO2, VCO2, VE) were measured in 14 trained HTRs (T-HTRs) during exercise tests on bicycle, on treadmill and by Holter electrocardiography during race. Results. Peak values observed in T-HTRs during the treadmill test were higher than those reached during the bicycle test (VO2peak: 39.8 ± 6.9 vs. 32.5 ± 7.8 ml·kg−1·min−1, p < 0.001; HRpeak: 169 ± 14 vs. 159 ± 16 bpm, p < 0.01). During treadmill exercise VO2peak and HRpeak values observed were very close to the mean predicted VO2pmax and HRpmax. The maximum heart rate during the race (HRrace) was greater than HRpeak values during the treadmill test (179 ± 14 vs 169 ± 14 bpm, p < 0.01) and slightly above the mean predicted values (HRrace/HRpmax × 100 = 101 ± 10%). The treadmill exercise test yields more reliable dat than does the bicycle test. Conclusions. Extensive endurance training enables heart transplant recipients to reach physical fitness levels similar to those of normal sedentary subjects; heart rate does not limit their exercise capacity.