Effect of right ventricular anatomy on the cardiopulmonary response to exercise. Implications for the Fontan procedure.

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Abstract
Incorporation of the right ventricle (RV) into the pulmonary circulation of patients with tricuspid atresia undergoing a Fontan procedure has been advocated. The consequences of this approach on the exercise function of these patients was studied by examining the effects of progressive and steady-state bicycle exercise tests performed by 11 patients with right atrial (RA)-RV Fontan anastomoses, seven patients with RA-pulmonary artery (PA) Fontan anastomoses, 13 patients after repair of tetralogy of Fallot, and 34 normal control patients. All patients were in New York Heart Association class I. The exercise function of the patients undergoing RA-RV and RA-PA Fontan procedures were similar. The achieved peak work loads 60% and 67% of control and peak oxygen consumptions 60% and 64% of control, respectively. Both groups also displayed excessive ventilation, elevated dead space/tidal volume ratios, and depressed cardiac output during steady-state exercise. In contrast, tetralogy of Fallot patients achieved peak work loads and oxygen consumptions 83% of control and maintained normal cardiac outputs and dead space/tidal volume ratios during steady-state exercise. These results suggest that the presence of an RV within the pulmonary circulation of the Fontan patient does not result in improved exercise function. This may be due to the development of obstructive gradients across the RA-RV conduits during exercise or to the RV's negative effect on left ventricular compliance. Moreover, in contrast with the postoperative tetralogy of Fallot patient, the hypoplastic RV of tricuspid atresia may not have sufficient myocardium to assume the active pumping function required by exercise.