Concerns with delayed right ventricle dysfunction have offset the early survival advantages after Norwood procedure with right ventricle to pulmonary artery conduit (NW-RVPA) over the Norwood with Blalock-Taussig shunt (NW-BT) in newborns with left ventricular outflow tract obstruction, but a recent report provides evidence that RV function between the two procedures is comparable for up to six years.
Reporting in the January issue of the Journal of Thoracic and Cardiovascular Surgery (J Thorac Cardiovasc Surg. 2015 Dec;150:1440–52), investigators for the Congenital Heart Surgeons’ Society (CHSS) trial found that NW-RVPA has better overall six-year survival and superior right ventricle function in the short term after surgery than NW-BT. The study involved 454 newborns with critical left ventricular outflow tract obstruction (LVOTO) in the CHSS database who had Norwood stage-1 from 2005 to 2014. Propensity matching paired 169 NW-RVPA patients with the same number of NW-BT patients for comparison. CHSS along with the Hospital for Sick Children in Toronto provided funding for the study.
Dr. Travis J. Wilder
“For neonates with critical LVOTO and similar baseline characteristics undergoing a Norwood stage-1 operation, the six-year overall survival and transplant-free survival were significantly better after NW-RVPA vs. NW-BT,” said Dr. Travis J. Wilder and his colleagues from the Hospital for Sick Children in Toronto.
Key questions the study sought to answer involved the clinical implications of the small variations in RV function between the two procedures, as well as the association between Norwood procedures and tricuspid valve regurgitation (TR) and overall survival.
Overall six-year survival was 70% for the NW-RVPA group vs. 55% for the NW-BT group. Right ventricle dysfunction rates three months after the procedure were lower for the NW-RVPA group, 6% vs. 16%, but rates of late RV dysfunction were less than 5% for both groups. Likewise, rates of moderate or greater TR at two years were lower in the NW-RVPA group: 11% vs. 16%.
Rates of Fontan operation after six years were higher among the NW-RVPA group (54% vs. 49%), as were transplantation rates (6% vs. 2%). Overall, 2% converted to a biventricular repair, but only after NW-RVPA; and seven patients who had NW-RVPA underwent a tricuspid valve repair, compared with four in the NW-BT group.
“For all survivors not undergoing transplantation or biventricular repair, the prevalence of late moderate or greater RV dysfunction and TR were similar between NW-BT and NW-RVPA at six years, without evidence of increased RV dysfunction for patients who underwent NW-RVPA,” Dr. Wilder and his colleagues said.
Consistent with previous studies, the CHSS study showed an early risk of death after a Norwood stage-1 operation, which may be due to a greater prevalence of significant RV dysfunction as the operation transitions from stage 1 to stage 2, Dr. Wilder and his coauthors said. “Although causation between these two time-related events cannot directly be made, it suggests that poor RV function contributes to early hazard for death,” they said.
The authors acknowledge a number of limitations with their study: the variation in the quality of echocardiogram reports from the multiple institutions involved, the inability of propensity matching to account for unmeasured factors and the influence of center and surgeon volume among participating sites. They also said that the ventriculotomy the NW-RVPA involves can lead to late aneurysm, arrhythmias, and ventricular failure. The adverse effects of ventriculotomy on long-term RV function “may not become apparent for years,” Dr. Wilder and his coauthors said.
Dr. Wilder presented a report of the original results at the 2015 American Association for Thoracic Surgery Annual meeting.
The authors had no relationships to disclose.