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

Abstract 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 (VO 2 , VCO 2 , VE) were measured in 14 trained HTRs (T-HTRs) during exercise tests on a bicycle, on a treadmill and by Holter electrocardiography during a race. Results. Peak values observed in T-HTRs during the treadmill test were higher than those reached during the bicycle test (VO 2peak: 39.8 ± 6.9 vs. 32.5 ± 7.8 ml·kg −1 ·min −1 , p peak : 169 ± 14 vs. 159 ± 16 bpm, p 2peak and HR peak values observed were very close to the mean predicted VO 2pmax and HR pmax . The maximum heart rate during the race (HR race ) was greater than HR peak values during the treadmill test (179 ± 14 vs 169 ± 14 bpm, p race /HR pmax × 100 = 101 ± 10%). The treadmill exercise test yields more reliable data 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.