The Pediatric Heart Network trial comparing outcomes in 549 infants with single right ventricle (RV) undergoing a Norwood procedure randomized to modified Blalock-Taussig shunt (MBTS) or right ventricle-to-pulmonary artery shunt (RVPAS) found better one-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 (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 RV ejection fraction was <50% at all intervals for both groups and was higher in the RVPAS group post-Norwood (49±7 vs. 44±8%, P<0.001), but was similar by 14 months. Tricuspid and neo-aortic regurgitation, diastolic function, and pulmonary artery and arch dimensions were similar in the two groups at all intervals. Neo-aortic annulus area (4.2±1.2 vs. 4.9±1.2 cm2/m2), systolic ejection times (214.0±29.4 vs. 231.3±28.6 msec), neo-aortic flow (6.2±2.4 vs. 9.4±3.4 L/min/m2), and peak arch velocity (1.9±0.7 vs. 2.2±0.7 m/sec) were lower at both interstage exams in RVPAS compared to MBTS (P<0.001 for all), but all were similar at 14 months.
Indices of cardiac size and function after the Norwood procedure are similar for MBTS 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 #
NCT00115934, URL: http://clinicaltrials.gov/ct2/show/NCT00115934
Keywords: hypoplastic left heart syndrome, Norwood, echocardiography, single ventricle