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Impact of Initial Shunt Type on Cardiac Size and Function in Children With Single Right Ventricle Anomalies Before the Fontan Procedure: The Single Ventricle Reconstruction Extension Trial
Study Questions:
What is the impact of shunt type at time of the Norwood procedure on right ventricular (RV) size and function in children with single RV congenital heart disease?
Methods:
This study was an extension of the SVR (Single Ventricle Reconstruction) trial, in which infants were randomized to a Norwood procedure using either the modified Blalock-Taussig shunt (MBTS) or RV-to-pulmonary artery shunt (RVPAS). Patients underwent echocardiography at 14 months and again prior to the Fontan procedure (33 ± 9.6 months). Echocardiographic indices included RV size and function, neoaortic and tricuspid valve annulus dimensions and function, and aortic size and patency.
Results:
Echocardiograms were available at both time points for 240 subjects, of which 114 had undergone MBTS and 126 RVPAS. There were no differences in echocardiographic indices at the time of the 14-month study. Patients in the MBTS group had stable indexed RV volumes and ejection fraction at the pre-Fontan echocardiogram. Patients in the RVPAS group had increased RV end-systolic volume (55.00 ± 17.84 as compared with 49.11 ± 14.47, p = 0.004) and decreased RV ejection fraction (41 ± 7 as compared with 44 ± 7, p = 0.004 on the pre-Fontan study). Other indices of RV function remained stable regardless of shunt type.
Conclusions:
The authors concluded that initial shunt type influences pre-Fontan RV function in survivors with single RV anomalies, with greater RV ejection fraction deterioration after RVPAS shunt.
Perspective:
This study provides additional evidence that the early benefits of the MBTS are not without later cost in terms of RV function. Reproducible assessment of RV function remains a challenge, and is one of the primary limitations of this study. The initial study reporting outcomes in the SVR extension trial (Newburger JW, et al., Circulation 2014;129:2013-20) showed no survival benefit at 3 years, with greater need for catheter interventions in the RVPAS group. It is important to note that the mean ejection fraction of all patients is abnormal, in the low 40s, highlighting the necessity of close follow-up of ventricular function in all single RV patients. The development of therapies for optimization of RV function remains a priority.
Keywords: Survivors, Child, Tricuspid Valve, Norwood Procedures, Ventricular Function, Right, Follow-Up Studies, Fontan Procedure, Blalock-Taussig Procedure, Echocardiography
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