Cardiorespiratory responses to exercise after repair of the univentricular heart

The purpose of this study is to evaluate cardiorespiratory responses to exercise in patients with univentricular heart according to the type of repair used. Forty-three patients with univentricular heart were divided into three groups: 15 preoperative patients (group A), 18 who had Fontan repair (group B) and 10 who had ventricular septation (group C). Group C was further divided into two subgroups, 7 with normal atrioventricular valve function (group C1) and 3 with atrioventricular valve regurgitation (group C2). Cardiorespiratory variables were determined after performance of cardiopulmonary exercise testing. One-hundred-and-twenty-five healthy subjects, age 5-26 years, served as controls. Oxygen uptake in group C1 at both ventilatory threshold and peak exercise was highest in all groups of univentricular heart (P < 0.05), while peak oxygen uptake in group C1 was significantly lower vs controls (P < 0.001), and that in group B was significantly higher than that for group A. Although chronotropic incompetence was noted in all groups of univentricular heart, marked improvements in both the relationship between heart rate and oxygen uptake and in the ventilatory efficiency were observed after definitive repair. While ventilatory efficiency was still impaired in group B, there was no significant difference between that in group C1 and the control group. When patients with univentricular heart of the left ventricular type (Van Praagh's type A single ventricle) were analyzed separately, superior cardiorespiratory response after ventricular septation was also found. In view of these findings, the ventricular septation procedure is preferred to the Fontan method in patients with univentricular heart when morphological conditions are suitable for this procedure so as not to make residual complications, such as significant atrioventricular valve regurgitation.