Background: One way of defining an individual’s heart effort is to calculate the maximum heart rate to be expected given their age, but the reinnervation seen in patients who have received heart transplants makes for different calculations from patients who have suffered heart failure. The purpose of this study is to evaluate heart rate dynamics (rest, peak and percentage of predicted heart rate for age) in heart transplant patients compared to optimized beta-blocked heart failure patients during a treadmill cardiopulmonary exercise test.
Methods: Twenty two (81% male, 46 ± 12 years) sedentary heart failure patients and 15 (47% male, 44 ± 13 years) sedentary heart transplant patients performed a treadmill cardiopulmonary exercise test between 10 am and 3 pm. Heart failure optimization was considered 50 mg/day or more of carvedilol, with a resting heart rate of between 50 and 60 bpm.
Results: Basal heart rate was lower in heart failure patients (58 ± 5 bpm) compared to heart transplant patients (93 ± 11 bpm; p < 0.0001). Similarly, the peak heart rate (percentage of the maximum predicted for age) was lower in heart failure patients (60 ± 13%) compared to heart transplant patients (80 ± 12; p < 0.0001). Maximum respiratory exchange ratio did not differ between the groups (1.05 ± 0.06 in heart failure patients and 1.11 ± 0.1 in heart transplant patients; p = 0.08). Moreover, the heart rate reserve between heart failure (49 ± 22) and heart transplantation (46 ± 16%) was not different (p = 0.644).
Conclusions: No patient reached the maximum heart rate predicted for their age during a treadmill cardiopulmonary exercise test. The heart rate reserve was similar between groups. A heart rate increase in heart transplant patients during cardiopulmonary exercise test of more than 80% of the maximum age-adjusted value should be considered an effort near the maximum.