Heart Rate Responses During Exercise by Dominant Ventricle in Pediatric and Young Adult Patients With a Fontan Circulation.

BACKGROUND

Patients with univentricular physiology palliated with the Fontan operation have multiple late cardiovascular and extracardiac complications, including autonomic dysfunction. Despite the observation, little is known about autonomic function driving exercise-related heart rate responses in Fontan patients and whether dominant ventricle subtype or underlying cardiac anatomy affects heart rate responses during exercise.

METHODS

We performed a retrospective chart review of all single ventricle patients palliated with a Fontan operation who underwent a maximal effort cardiopulmonary exercise test at Cincinnati Children's Hospital Medical Center from 2013 to 2018.

RESULTS

One hundred and three Fontan patients aged 16.7 ± 5.5 years were included in this study. Although both the systemic right (n = 38) and systemic left (n = 65) ventricle groups demonstrated chronotropic incompetence, there were no differences between the groups in maximal heart rate (167.5 ± 17.4 vs 169.6 ± 20.9 bpm, P = 0.59), heart rate reserve (87.3 ± 22.6 vs 96.8 ± 25.7, P = 0.06) nor chronotropic index (70 ± 13% vs 74 ± 20%, P = 0.19). In addition, there were no differences between the groups in heart rate recovery at 1, 3, 5, and 10 minutes. Interestingly, patients with hypoplastic left heart syndrome (n = 34) had lower heart rate reserve (84.76 ± 22.8 vs 96.38 ± 26.75, P = 0.04) and chronotropic index (70.5 ± 12.5% vs 76.3 ± 13.2%, P = 0.04) compared with patients with tricuspid atresia (n = 42).

CONCLUSIONS

Fontan patients commonly have chronotropic incompetence, diminished heart rate reserve but with preserved heart rate recovery. Although there is overall no difference in chronotropy in Fontan patients based on dominant systemic ventricle, there is a difference between patients with hypoplastic left heart syndrome and those with tricuspid atresia.