Abstract 13454: Does Initial Shunt Type for the Norwood Procedure Impact Echocardiographic Measures of Cardiac Size and Function During Infancy? The Single Ventricle Reconstruction Trial
Background: A recent Pediatric Heart Network trial comparing outcomes in infants with single right ventricle anomaly undergoing a Norwood procedure randomized to either modified Blalock-Taussig shunt (MBTS) or right ventricle-pulmonary artery shunt (RVPAS) found better 1-year transplant-free survival in those who received RVPAS. We sought to compare the impact of shunt type on echocardiographic indices of cardiac size and function at specific intervals up to 14 months in this cohort.
Methods: An echo core lab measured indices of systolic, diastolic and global ventricular function, ventricular and vascular dimensions, neo-aortic/tricuspid annular dimensions, valvar function, and neo-aortic flow patterns from protocol exams at 3 post-operative time intervals: early after Norwood (22.4±13.5 days of age), before the Stage II palliation (4.8±1.8 months) and at 14 months of age (14.3±1.2 months).
Results: There were 271 acceptable studies in each shunt group at baseline. Mean RV ejection fraction was low (<50%) at all intervals for both groups and was higher in the RVPAS group post-Norwood (48.5±7.6 vs 44.5±7.6%, p<0.0001), but was similar by 14 months (154 MBTS, 180 RVPAS). Severity of tricuspid and neo-aortic regurgitation, measures of RV diastolic function, and pulmonary artery and arch dimensions were similar in the two groups at all intervals. Neo-aortic annular area (4.2±1.1 vs 4.9±1.2 cm2/m2), systolic ejection times (215.4±30.3 vs 229.3±28.4 ms), indexed neo-aortic flow (6.4±2.6 vs 9.2±3.4 L/min/m2), descending aortic retrograde fraction (0 vs 39%), and peak aortic arch gradient (1.9±0.7 vs 2.2±0.7 m/s) were significantly lower at both interstage intervals in RVPAS compared to MBTS (all p<0.001), but these measurements also were similar at 14 months.
Conclusion: Indices of RV function, cardiac and vascular dimensions, valvar dimensions and function and neo-aortic flow patterns post-operatively in survivors of the Norwood procedure are similar for MBTS and RVPAS types by 14 months of age. Interstage differences in neo-aortic annular size and flow patterns between shunt types can likely be explained by the different physiologies created when the shunts are in place rather than by intrinsic differences in myocardial and valvar function.
- © 2011 by American Heart Association, Inc.