Objective: Partial normalization of the heart rate (HR) response can take place some time after heart transplantation (HTx), but the extent to which this occurs, its time course, and functional significance remain unclear.
Design: Seventy-seven heart transplantation patients underwent an exercise test at approximately 1, 6, and 12 mos after heart transplantation, consisting of a resting period, a submaximal exercise test, and a maximal exercise test with stair climbing, followed by a recovery period. An HR monitor was used for continuous surveillance of HR.
Results: During the follow-up, HR at rest did not change, whereas all other HR parameters obtained during and after exercise improved, demonstrating a more rapid increase, a higher peak, and a more rapid decline in HR after stopping exercise. Age-predicted maximum HR at baseline was 73% ± 9%, improving to 83% ± 10% at 6 mos (P < 0.001) and to 90% ± 10% at 12 mos (P < 0.001), whereas the Chronotropic Response Index at baseline was 0.49 ± 0.15, improving to 0.67 ± 0.17 at 6 mos (P < 0.001) and to 0.81 ± 0.23 at 12 mos (P < 0.001).
Conclusions: Partial normalization of HR was achieved by 71% of heart transplantation patients at 12 mos, with significant changes occurring within 6 mos in most subjects. These findings should contribute to reducing the exercise restrictions that apply to the denervated heart.