Does right ventricular outflow tract damage play a role in the genesis of late right ventricular dilatation after tetralogy of Fallot repair?

BACKGROUND: The aim of this study was to determine the relative role of pulmonary insufficiency and right ventricular outflow tract damage in the genesis of late symptoms related to right ventricular dilatation.
METHODS: In a retrospective study we compared the late outcomes of patients who had undergone operations known to generate pulmonary insufficiency, namely, transventricular repair of tetralogy of Fallot and pulmonary commissurotomy for isolated pulmonary stenosis.
RESULTS: In our institution, between 1964 and 1984, a total of 44 patients were found to have had an isolated pulmonary commissurotomy and 189 survived a transventricular repair of tetralogy of Fallot. Of these patients, 134 had patching of the right ventricle and 55 direct closure of a right ventriculotomy. Follow-up was 94% complete after a mean of 22 +/- 7 years. On echocardiography, patients with isolated commissurotomy had similar degrees of moderate and severe pulmonary insufficiency as tetralogy of Fallot patients who had a right ventricular patch (p > 0.2). However, freedom from adverse events related to right ventricular dilatation was far better (log rank p < 0.001) in patients with isolated commisurotomy.
CONCLUSIONS: Pulmonary insufficiency is not the only determinant of late symptomatic right ventricular dilatation after repair of tetralogy of Fallot. Pulmonary insufficiency seems much more deleterious in patients who have had right ventricular outflow tract patching. Long-term pulmonary insufficiency alone is responsible for a slight degree of right ventricular dilatation, but symptoms may develop much later if the contractility of the pulmonary infundibulum is preserved. The pulmonary infundibulum may be essential for right ventricular ejection, and for maintaining pulmonary valve competence.