Does Initial Shunt Type for the Norwood Procedure Affect Echocardiographic Measures of Cardiac Size and Function During Infancy?

Abstract

Background— The Pediatric Heart Network trial comparing outcomes in 549 infants with single right ventricle undergoing a Norwood procedure randomized to modified Blalock-Taussig shunt 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 up to 14 months of age. Methods and Results— A core laboratory measured indices of cardiac size and function from protocol exams: early after Norwood procedure (age 22.5±13.4 days), before stage II procedure (age 4.8±1.8 months), and at 14 months (age 14.3±1.2 months). Mean right ventricular ejection fraction was <50% at all intervals for both groups and was higher in the RVPAS group after Norwood procedure (49±7% versus 44±8%; P <0.001) but was similar by 14 months. Tricuspid and neoaortic regurgitation, diastolic function, and pulmonary artery and arch dimensions were similar in the 2 groups at all intervals. Neoaortic annulus area (4.2±1.2 versus 4.9±1.2 cm 2 /m 2 ), systolic ejection times (214.0±29.4 versus 231.3±28.6 ms), neoaortic flow (6.2±2.4 versus 9.4±3.4 L/min per square meter), and peak arch velocity (1.9±0.7 versus 2.2±0.7 m/s) were lower at both interstage examinations in the RVPAS compared with the modified Blalock-Taussig shunt group ( P <0.001 for all), but all were similar at 14 months. Conclusions— Indices of cardiac size and function after the Norwood procedure are similar for modified Blalock-Taussig shunt and RVPAS by 14 months of age. Interstage differences between shunt types can likely be explained by the physiology created when the shunts are in place rather than by intrinsic differences in cardiac function. Clinical Trial Registration— URL: http://www.clinicaltrials.gov . Unique identifier: NCT00115934.