Changes of right ventricular size and function in neonates after valvotomy for pulmonary atresia or critical pulmonary stenosis and intact ventricular septum

Abstract

Right ventricular end-diastolic and stroke volumes were calculated from orthogonal subcostal echocardiographic images in 24 neonates (mean weight ± SD 3.4 ± 0.4 kg) with pulmonary atresia (n = 18) or critical pulmonary stenosis (n = 6) and intact ventricular septum before and at an average of 5 days and then 19 days after pulmonary valvotomy. The preoperative echocardiographic volume determinations were compared with the respective angiographic determinations. In addition, the endocardial area outlines of the left and right ventricles were obtained by planimetry from an end-diastolic frame taken in the apical four-chamber view.End-diastolic and stroke volumes calculated by the echocardiographic method (y) correlated closely with those calculated by the angiographic method (x); the regression equations were y = 1.02 × −0.13 (r = 0.95, SEE ± 0.45 ml) and y = 1.16 × −0.15 (r = 0.89, SEE ± 0.38 ml), respectively. All except one infant had right ventricular hypoplasia before valvotomy with an end-diastolic volume of 16.6 ± 6.4 ml/m2(44.5 ± 17.3% of normal). Right to left ventricular area ratio was 0.56 ± 0.09 (normal 0.95). Five days after valvotomy, right ventricular end-diastolic volume decreased to 10.6 ± 4.6 ml/m2(p < 0.05) and stroke volume decreased from 8.3 ± 3.5 to 5.5 ± 2.8 ml/m2(p < 0.05). Nineteen days after valvotomy, right ventricular end-diastolic volume and right to left ventricular area ratio had increased to their respective preoperative values; right ventricular stroke volume had increased further to 10.4 ± 3.9 ml/m2(p < 0.05).These findings indicate that right ventricular volume can be calculated accurately by two-dimensional echocardiography and that these measurements can be used serially in patients with pulmonary atresia and intact septum. Right ventricular end-diastolic and stroke volumes decrease early after decompression of the outflow obstruction. Therefore, an additional temporary source of auxiliary pulmonary blood flow may be necessary to support the neonate who undergoes relief of right ventricular outflow tract obstruction. Echocardiographic calculation of end-diastolic and stroke volume and right to left ventricular area ratios may aid in determining when the prostaglandin infusion to maintain ductus patency might be discontinued.