Background: After orthotopic heart transplantation (HTX), heart rate variability and response
to exercise is impaired in most cases. Surgical interruption of autonomic innervation
of the heart results in higher resting heart rates and lower peak heart rates compared
with healthy patients. Although several studies on the effect of sports have been
performed on adult heart transplant recipients, none of them displays pediatric patients.
We report on the case of a 14-year-old orthotopic heart transplant recipient (November,
2018) with implantation of a DDDR pacemaker due to intermittent third degree AV-block
(October 2019) and the remarkable improvement of his cardiorespiratory exercise values
due to substantial increase of regular sports activities during a period of 16 months.
Assessment was performed by cardiopulmonary exercise testing (CPET) on a treadmill
(TM).
Method: From February 2020 to July 2021, a now 14-year-old boy with orthotopic HTX in November
2018 underwent two cardiopulmonary exercise tests on a TM. First CPET was performed
using a modified Bruce protocol. For the second CPET, we used an age- and fitness-adapted
protocol without inclination of the TM. Sports activities during this time were highly
increased from occasional sports at the beginning to daily biking, boxing, and trampolining
after 16 months.
Results: Within 16 months of highly increased physical activity, we noticed higher values
for heart rate at VO2 peak (154 vs. 172/min) and VO2 peak itself (33 vs. 43 mL/min/kg).
Percentage heart rate recovery raised from 1.2% versus 2.9% (1 minute) to 12.2 versus
22.7% (5 minutes). The O2 pulse at VO2 peak increased from 13 to 15 mL, VEmax from
84.1 to 126.1 L/min, and tidal volume from 1.31 to 1.79 L. Maximum effort was given
with RER values ≥ 1.1 for both tests. Heart rate at rest fell from 101 to 89/min.
Conclusion: As previously described, peak heart rate in pediatric HTX patients raises by 2.0
bts/min/year and exercise capacity measured by VO2 peak improves over time. The increase
of peak heart rate and VO2 peak exceeded our expectations, eventually displaying a
faster response on sports in pediatric patients, potentially providing evidence for
progressed graft reinnervation. This case report underlines the importance of supervised
training and its evaluation by CPET in pediatric heart transplant patients. Surely,
further studies are needed but maybe we could start to encourage OUR PATIENTS to run
for their lives instead of us.
