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 (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. Conclusion 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

Risk Factors for Death or Heart Transplant for Patients with Right Ventricular Dysfunction After the Norwood Procedure: A Secondary Analysis of the Single Ventricle Reconstruction Trial

“…Multiple secondary analyses have been published using this dataset. Examples include evaluation of the interstage mortality (Ghanayem et al 2012), risk factors for death or transplant in the intermediate term (Tweddell et al 2012) and 3 years term (Newburger et al 1993), as well as shunt type effect on the cardiac function, ventricular size (Frommelt et al 2012), and ventricular deformation (Hill et al 2015). However, the group of patients with ventricular dysfunction has not been evaluated separately.…”

“…However, the group of patients with ventricular dysfunction has not been evaluated separately. This dataset, in addition to providing access to the largest cohort of infants with HLHS post-Norwood procedure, also affords the opportunity for serial protocolized quantitative assessment of right ventricular function (Frommelt et al 2012). All the SVR trial echocardiograms were done at protocolized times and were all read by the same expert at a core lab (Ohye et al 2008), with potentially better accuracy for the ventricular dysfunction cohort selection.…”

“…Figure 6). RVFAC expresses the percentage change of the calculated right ventricular areas between the enddiastole right ventricular area (the end of the part of the cardiac cycle when the heart relaxes, when the heart is at its biggest) and end-systole right ventricular area (the end of the cardiac contraction, when the heart is at its smallest) (Pavlicek et al 2011; P. C. Frommelt et al 2012).…”

“…In the SVR trial (Frommelt et al 2012), the volumes were obtained from the right ventricular area measured on the transverse apical 4-chamber view at the level of the tricuspid annulus ( Figure 6) as well as the right ventricular cavity length measured on the subcostal sagittal view ( Figure 7). Then right ventricular volumes were calculated using the biplane pyramidal method (Helbing et al 1995) and ejection fraction is obtained using the In the SVR cohort, the average right ventricle ejection fraction (RVEF) (46 % +/-9 %) and area fraction change (35 % +/-9%) were calculated to be low and that throughout the 14 months follow-up (Frommelt et al 2012). The incidence of moderate right ventricular dysfunction, assessed visually, has been recently shown to peak at three to six months post-Norwood procedure with an incidence of 11 % +/-3 % (Wilder, McCrindle, et al 2015b).…”

“…The infants enrolled in the SVR trial underwent echocardiograms on a preset schedule, which included the following time points: before the Norwood procedure (baseline), post-Norwood procedure, pre-stage II, and 14 months of age. For this secondary analysis, we defined ventricular dysfunction if it was present on the postNorwood echocardiograms, which were done after the Norwood procedure at a mean age of 22.5 +/-13.4 days post-Norwood procedure (Frommelt et al 2012). …”