Eight Fontan patients (4 male/4 female) without pacemakers and 12 healthy volunteers (5 m/7 f) with minimum age of 18 years were recruited. HR was measured by Holter-electrocardiogram. HRV was measured in supine position and after orthostatic challenge. The power of the high frequency (HF: 0.15 Hz–0.4 Hz) and low frequency (LF: 0.04 Hz–0.15 Hz) bands was analysed by fast-Fourier transformation. HR recovery was determined at 30 s and 60 s after termination of a maximal exercise test.
In both supine and standing position, total power, HF and LF power were reduced in Fontan patients compared to controls (by approximately a factor of 10) while there was no differences in LF/HF power ratio. Response to orthostatic challenge was blunted in absolute power but normal in relative power. HR recovery was not different between groups.
Fontan patients have greatly reduced HRV, a blood-pressure dependent marker of CANA, but normal HR recovery, a blood pressure independent marker of vagal reactivation, suggesting that vagal activity may be normal, and only vascular capacitance reduced.