Growth of the pulmonary anulus and pulmonary arteries after the Blalock-Taussig shunt

Abstract

Twenty-one children with tetralogy of Fallot were studied angiocardiographically before a palliative Blalock-Taussig anastomosis (mean age, 15 ± 2.2 months) and again 28.9 ± 8.52 months later. When the initial ratio between the diameter of the pulmonary anulus and that of the descending thoracic aorta (D PA /D Desc Ao ) was less than 1.0, it increased by 0.19 ± 0.178 after anastomosis (p = 0.002). When initially it was less than 0.7, it increased by 0.34 ± 0.125. Mean pulmonary artery pressure after shunting (presumably determined by the magnitude of the shunt) is related to the magnitude of increase in the relative size of the pulmonary anulus (r = 0.48; p = 0.07). The ratios of right (D RPA ) and left pulmonary artery diameters (D LPA ) to D Desc Ao also increased in the interval, 0.14 ± 0.190 for D RPA /D Desc Ao (p = 0.004) and 0.13 ± 0.244 for D LPA /D Dec Ao (p = 0.03). The ipsilateral (relative to the Blalock-Taussig shunt) artery enlarged to the same degree as the contralateral pulmonary artery. Calculations using Alfieri and colleagues’ equation indicate that the enlargement of right pulmonary artery and left pulmonary artery was sufficient to predict significantly lower right ventricular peak pressure after intracardiac repair than would have been measured after the initial catheterization. This, plus the increase in D PA /D Desc Ao , suggests that an initial palliative Blalock-Taussig anastomosis in infants with small pulmonary anuli and small right and left pulmonary arteries might allow later complete repair to be done, with the result being a somewhat lower right ventricular pressure after repair and possibly with a lower incidence of transannular patching than if performed primarily.