ENALAPRIL DOES NOT ENHANCE EXERCISE CAPACITY IN PATIENTS AFTER FONTANPROCEDURE

Background Angiotensin-converting enzyme inhibitors improve exercise c apacity in adults with congestive heart failure by decreasing systemic vascular resistance and improving ventricular diastolic function. Pat ients who have undergone the Fontan procedure have decreased cardiac o utput, increased systemic vascular resistance, abnormal diastolic func tion, and decreased exercise capacity compared with normal people. Met hods and Results To test the hypothesis that afterload reduction thera py alters hemodynamic variables and augments exercise capacity in pati ents after a Fontan procedure, we compared the results of graded exerc ise with maximal effort from 18 subjects (14.5+/-6.2 years of age, 4 t o 19 years after Fontan procedure) in a randomized, double-blind, plac ebo-controlled crossover trial using enalapril (0.2 to 0.3 mg.kg(-1).d (-1), maximum 15 mg). Each treatment was administered for 10 weeks. Di astolic filling patterns at rest were assessed by Doppler determinatio n of the systemic atrioventricular valve flow velocity at the conclusi on of each therapy. No difference was detected in resting heart rate, blood pressure, or cardiac index. Diastolic filling patterns were also similar. Exercise duration was not different (6.4+/-2.6 [enalapril] v ersus 6.7+/-2.6 minutes [placebo]). The mean percent increase in cardi ac index from rest to maximum exercise was slightly but significantly decreased in subjects after 10 weeks of enalapril therapy (102+/-34% [ enalapril] versus 125+/-34% [placebo]; P<.02). At maximal exercise, ca rdiac index (3.5+/-0.9 [enalapril] versus 3.8+/-0.9 L.min(-1).m(2) [pl acebo]), oxygen consumption (18.3+/-9 [enalapril] versus 20.5+/-7 mL.m in(-1).kg(-1) [placebo]), minute ventilation (57.5+/-17 [enalapril] ve rsus 55.4+/-19 L/min [placebo]), and total work (247+/-181 [enalapril] versus 261+/-197 W [placebo]) were not different. Conclusions We conc lude that enalapril administration for 10 weeks does not alter abnorma l systemic vascular resistance, resting cardiac index, diastolic funct ion, or exercise capacity in patients who have undergone a Fontan proc edure.