Post-exercise heart rate, blood pressure and oxygen uptake dynamics in pediatric patients with Fontan circulation: Comparison with patients after right ventricular outflow tract reconstruction

Background Post-exercise heart rate (HR) and oxygen uptake (V˙O2) recover more slowly in patients with the Fontan circulation, but little is known about the determinants of the delayed recovery. Purpose To evaluate the post-exercise cardiovascular dynamics and clinical profiles in these patients. Methods and results We studied 51 Fontan patients (14±4 years) (atriopulmonary connection, APC=18 and total cavopulmonary connection, TCPC=33) and compared the results with 34 patients after right ventricular outflow tract reconstruction (RVOTR) with identical exercise capacity and arterial baroreflex sensitivity (BRS) (15±4 years) and with 26 controls (14±4 years). There were no differences in post-exercise HR or V˙O2 declines between the Fontan and RVOTR groups. Although the systolic blood pressure (SBP) decline was delayed in the RVOTR group (p<0.01), its early decline in the Fontan group was rapid and equivalent to that in controls. In Fontan patients, BRS had a great impact on early HR decline (p<0.05) and early V˙O2 decline was determined by peak V˙O2, age and cardiac index (p<0.05–0.001). TCPC and lower BRS were the main determinants of the slower SBP decline (p<0.05). In another study of repeated paired exercise tests before and after Fontan operation, post-exercise SBP decline became greater after the operation (p<0.07). Conclusions In the Fontan group, post-exercise HR and V˙O2 declines are markedly delayed and are determined by cardiac vagal nervous activity, exercise capacity and age, respectively. Despite identical impaired hemodynamics and exercise capacity, post-exercise SBP decline is greater in the Fontan group, especially after APC, than in the RVOTR patients.