Systemic ventricular outflow obstruction progresses after the Fontan operation.

To evaluate the course of systemic ventricular outflow obstruction after the Fontan operation, the records of 57 hospital survivors of that procedure were reviewed. Ventricular outflow obstruction was identified in 7 patients (group 1) and was absent in 50 patients (group 2). Overall, the ventricular outflow gradient in group 1 was 6.3 +/- 2.9 mm Hg (mean +/- standard error) before the Fontan operation and 7.6 +/- 3.9 mm Hg at hospital discharge. Ventricular outflow obstruction subsequently progressed to 80.1 +/- 17.3 mm Hg (range, 33 to 165 mm Hg; p < 0.02) a mean of 28 months postoperatively. One patient died of severe progressive ventricular outflow obstruction. Group 1 did not differ from group 2 in age, ventricular morphology, presence of a subaortic outflow chamber, prior shunt, or length of follow-up. Compared with group 2, however, patients in group 1 more commonly had an aorta arising from a hypoplastic ventricle (p < 0.001) and had undergone prior pulmonary artery banding (p = 0.005). We conclude that systemic ventricular outflow obstruction occurs commonly after a Fontan procedure (incidence, 12%; 70% confidence interval, 9% to 18%) and is a progressive lesion.