Long-term sequential changes in exercise capacity and chronotropic responsiveness after cardiac transplantation

Area of Science:

• Cardiology
• Transplantation Medicine
• Exercise Physiology

Background:

• Orthotopic cardiac transplantation improves peak exercise capacity early on.
• However, heart rate (HR) response during exercise remains abnormal due to cardiac denervation, characterized by a reduced HR rise and subnormal peak exercise HR.
• The study investigated if cardiac reinnervation improves chronotropic responsiveness and exercise capacity over time.

Purpose of the Study:

• To evaluate the long-term changes in chronotropic response to exercise and maximal exercise capacity after cardiac transplantation.
• To determine if cardiac reinnervation occurs and improves physiological responses to exercise between 1 and 5 years post-transplant.

Main Methods:

• Retrospective analysis of serial peak symptom-limited cardiopulmonary exercise tests in 57 cardiac transplant recipients up to 5 years post-transplant.
• Comparison with 33 control subjects without heart disease and pre-transplantation data from 41 patients.
• Assessment of peak oxygen consumption, peak exercise HR, and HR increment from rest to peak exercise.

Main Results:

• One year post-transplantation, peak oxygen consumption increased by 43% compared to pre-transplantation levels.
• Maximal exercise capacity and HR response to exercise remained subnormal compared to control subjects.
• No further improvements in peak exercise capacity, peak exercise HR, or HR increment were observed up to 5 years post-transplantation.

Conclusions:

• Peak exercise capacity and chronotropic responsiveness are suboptimal one year after cardiac transplantation.
• There is no significant improvement in these parameters between 1 and 5 years post-transplantation.
• Functionally significant cardiac reinnervation does not appear to occur in this timeframe, indicating persistent chronotropic incompetence.