The initial type of a Norwood shunt influences pre-Fontan right ventricular (RV) remodeling during the second and third years of life in survivors with single RV anomalies, but with greater right ventricular ejection fraction deterioration after right ventricle-to-pulmonary artery shunting (RVPAS), according to a study published Nov. 3 in the Journal of the American College of Cardiology.

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It is estimated that there are approximately 2,000 babies born with hypoplastic left heart syndrome (HLHS), a rare congenital heart anomaly, in North America each year. Reporting the first successful surgical palliation of the condition was William Norwood in the early 1980s. Continuing on the path left by the Single Ventricle Reconstruction (SVR) trial, which compared the outcomes of the first stage of palliation of HLHS based on shunt type, a new investigation helmed by principal investigator Peter Frommelt, MD, Medical College of Wisconsin, sought to identify shunt-related differences in echocardiographic findings at 14 months and ≤ six months pre-Fontan in survivors of the Norwood procedure.

Comparing two-dimensional and Doppler echocardiographic indices of RV size and function, neo-aortic and tricuspid valve annulus dimensions and function, and aortic size and patency at 14.1 ± 1.2 and 33.6 ± 9.6 months in 240 subjects randomized to a Norwood procedure using either the modified Blalock-Taussig shunt (MBTS) or RVPAS (114 MBTS; 126 RVPAS), results showed that at 14 months, all indices were similar between shunt groups. In the 14-month to pre-Fontan echocardiogram, the MBTS group had stable indexed RV volumes and ejection fraction, while the RVPAS group had increased RV end-systolic volume (p =0.004) and decreased RV ejection fraction (p = 0.004). Both treatment groups were similar in respect to showing decline in indexed neo-aortic valve area, >mild neo-aortic valve regurgitation (<5 percent at each time), indexed tricuspid valve area, and ≥moderate tricuspid valve regurgitation (<20 percent at each time).

The authors note that the study “provides a unique opportunity for longitudinal assessment of a large, high-risk cohort of children born with single right ventricle anomalies as they progress through staged surgical palliation.” They add that “review of other echocardiographic indices that characterize ventricular function in this cohort did not provide a clear picture of RV failure in the RVPAS survivors prior to Fontan, which suggests that conclusions about the shunt-influenced health of the RV may require additional longitudinal follow-up.”

As Rajesh Shenoy, MBBS, FACC, and Ira A. Parness, MD, FACC write in a coinciding editorial, “the authors are commended for presenting unique and important data stemming from the medium-term follow up of patients from the original cohort of the SVR study. Ongoing follow-up of this cohort will yield important data upon which pediatric heart specialists can base the choice of surgical modality for initial HLHS palliation. Although the field is challenged by the continual evolution of alternate surgical approaches [...] this study represents a notable step forward in the quest for outcomes based decision making in this highly complex field.”

Keywords: Infant, North America, Follow-Up Studies, Heart Defects, Congenital, Tricuspid Valve Insufficiency, Decision Making, Wisconsin, Pulmonary Artery, Survivors, Norwood Procedures, Echocardiography, Doppler, Aortic Valve, Blalock-Taussig Procedure, Hypoplastic Left Heart Syndrome, Stroke Volume, Ventricular Function, United States

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