In Search of the Ideal Pulmonary Blood Source for the Norwood Procedure: A Meta-Analysis and Systematic Review

Abstract

A clear consensus regarding the optimal source of pulmonary blood flow in patients with hypoplastic left heart syndrome undergoing the Norwood procedure is lacking. A literature search was undertaken to identify relevant articles from 2005 to 2012 using "Norwood, stage 1 palliation," "Modified Blalock Taussig shunt (MBTS)," "right ventricle-to-pulmonary artery shunt (RV-PAS)" alone or in combination. Three end points were selected: early/stage 1 mortality, interstage mortality, and interstage total/shunt intervention. A total of 20 articles, including 19 observational studies and 1 randomized trial (MBTS, n=1,343; RV-PAS, n=1,028), met the inclusion criteria. Mortality after stage 1 was 22% in the MBTS cohort and 16% in RV-PAS cohort. A pooled analysis showed no difference in early mortality between the two groups (risk ratio [RR], 1.20; 95% confidence interval [CI], 0.99 to 1.45; p=0.07). On pooling data from contemporary series (similar era) of 8 studies (MBTS, n=709; RV-PAS, n=631), to minimize variability in surgical and postoperative management practices, early mortality in both cohorts was comparable (RR, 1.14; 95% CI, 0.89 to 1.45; p=0.29). Interstage mortality was 13.8% and 4.6% in the MBTS and RV-PAS cohorts, respectively, and was significantly lower for RV-PAS (RR, 2.85; 95% CI, 1.65 to 4.89; p<0.00002). However, patients with MBTS had fewer shunt interventions (RR, 0.55; 95% CI, 0.44 to 0.68; p<0.001; I2=00%). Our pooled analysis demonstrated no survival benefit for the MBTS or RV-PAS in patients undergoing the Norwood procedure. There appears to be an advantage with the RV-PAS with regard to interstage mortality at the cost of an increased rate of shunt intervention.