The Pediatric Heart Network’s (PHN) Single Ventricle Reconstruction Trial (SVR) randomized infants with single right ventricles (RV) undergoing a Norwood procedure to a modified Blalock-Taussig or RV-to-pulmonary artery shunt. This report compares RV parameters in the two groups using 3-dimensional echocardiography (3DE).
Methods and Results
3DE studies were obtained at 10/15 SVR centers. Of the 549 subjects, 314 underwent 3DE studies at one to four time points (pre-Norwood, post-Norwood, pre-stage II, and 14 months) for a total of 757 3DEs. Of these, 565 (75%) were acceptable for analysis. RV volume, mass, mass:volume ratio, ejection fraction (EF), and severity of tricuspid regurgitation did not differ by shunt type. RV volumes and mass did not change after the Norwood, but increased from pre-Norwood to pre-stage II (end-diastolic volume [EDV, ml]/body surface area [BSA]1.3, end-systolic volume [ESV, ml]/BSA1.3 and mass[g]/BSA1.3 mean difference [95% confidence interval] = 25.0 [8.7, 41.3], 19.3 [8.3, 30.4], and 17.9 [7.3, 28.5], then decreased by 14 months (EDV/BSA1.3, ESV/BSA1.3 and mass/BSA1.3 mean difference [95% confidence interval] = −24.4 [−35.0, −13.7], −9.8 [−17.9, −1.7], and −15.3 [−22.0, −8.6]. EF decreased from pre-Norwood to pre-stage II (mean difference [95% confidence interval] = −3.7% [−6.9%, −0.5%]), but did not decrease further by 14 months.
We found no statistically significant differences between study groups in 3DE measures of RV size and function, or magnitude of tricuspid regurgitation. Volume unloading was seen after stage II, as expected, but EF did not improve. This study provides insights into the remodeling of the operated univentricular RV in infancy.
Clinical Trial Registration
URL: http://www.clinicaltrials.gov. Unique identifier: NCT00115934.