Pulmonary Annulus Growth After the Modified Blalock-Taussig Shunt in Tetralogy of Fallot

Background In tetralogy of Fallot (TOF), it is well known that postoperative pulmonary regurgitation reduces right ventricular function during long-term follow-up. Complete repair without a transannular patch should help avoid pulmonary regurgitation. Recently, primary complete repair has been preferred to the staged repair with use of a Blalock-Taussig shunt (BTS) even in neonates or small infants; however, little has been reported about the influence of a BTS on pulmonary annular growth. Methods We examined 40 patients with TOF or double-outlet right ventricle with pulmonary stenosis. Twenty-one patients received a BTS before complete repair, whereas 19 patients underwent primary complete repair. Pulmonary annular size was measured by echocardiography before BTS, complete repair, or both, and ventricular volume was measured by cardiac catheterization. Results There were no significant differences in complete repair age or body size between the groups. Pulmonary annulus sizes in the BTS group were smaller than those in the primary repair group (Z score, −5.1 ± 2.5 vs −3.7 ± 1.8). After the BTS, significant annular growth (Z score, −2.8 ± 2.1) was observed ( p = 0.0028), with a significant increase in left ventricular end-diastolic volume ( p = 0.015). When patients with severe pulmonary stenosis (Z score > −7.0) were excluded, pulmonary annular preservation at complete repair was achieved in 64.7% (11/17) of the BTS group and 36.8% (7/19) of the primary repair group ( p = 0.088). Conclusions The BTS increased the pulmonary annular size and the left ventricular volume during the 6 months before complete repair, resulting in preservation of the pulmonary valve function.