Little outcomes data have been published comparing hybrid and Norwood stage 1 procedures for newborns with critical left ventricular outflow tract obstruction (LVOTO), but a prospective analysis of more than 500 operations over 9 years reported that while the Norwood has better survival rates overall, hybrid procedures may improve survival in low-birth-weight newborns.

“Although lower birth weight was identified as an important risk factor for death for the entire cohort, the detrimental impact of low birth weight was mitigated, to some degree, for patients who underwent a hybrid procedure,” said Travis Wilder, MD , of the Congenital Heart Surgeons’ Society (CHSS) Data Center, and his coauthors. They reported their findings in the January 2017 issue of the Journal of Thoracic and Cardiovascular Surgery ( 153:163-72 ).

Their study involved a cohort of 564 neonates prospectively enrolled with critical left ventricular outflow tract obstruction who underwent Norwood stage 1 procedures at 20 CHSS institutions and hybrid procedures at 11 centers during 2005-2014. The Norwood group had either the modified Blalock-Taussig shunt (NW-BT) (232) or a right ventricle–to-pulmonary artery conduit (NW-RVPA) (222) while 110 had the hybrid procedure. Fourteen centers enrolled 10 patients or more in the study. Of those patients who had an initial hybrid operation, 24% were converted to a Norwood operation.

Norwood operations involve major surgical reconstruction along with exposure to cardiopulmonary bypass (CPB), with either deep hypothermic circulatory arrest (DHCA) or regional cerebral perfusion, during aortic arch reconstruction. Previous reports have linked CPB to postoperative hemodynamic instability, complications, and death ( Ann Thorac Surg. 2009 Jun;87:1885-92 ). “In addition, the early physiological stress imposed on neonates after Norwood operations raises concerns regarding adverse neurodevelopment,” Dr. Wilder and his coauthors wrote.

Dr. Wilder and his coauthors pointed out that the hybrid procedure has emerged to avoid CPB and DHCA or regional cerebral perfusion and the potential resulting physiologic instability. “In this light, hybrid palliation may be perceived as a lower-risk alternative to Norwood operations, especially for patients considered at high risk for mortality,” the researchers said. Despite that perception, the actual survival “remains incompletely defined,” they said.

The overall average 4-year unadjusted survival for the entire study population was 65%, but those who had the NW-RVPA procedure had significantly improved survival (73%) vs. both the NW-BT (61%) and the hybrid groups (60%).

Those who had the hybrid procedure were older at stage 1 (12 days vs. 8 and 6 days, respectively for NW-BT and NW-RVPA) and had lower birth weight (2.9 kg vs. 3.2 kg and 3.15 kg, respectively). Hybrid patients also had a higher prevalence of baseline right ventricle dysfunction, were more likely to have baseline tricuspid valve regurgitation, and had a lower prevalence of aortic and mitral valve atresia.

For all patients, birth weight of 2.0-2.5 kg had a strong association with poor survival, Dr. Wilder and his coauthors reported, but the drop-off in survival for low-birth-weight neonates was greater in the Norwood group than in the hybrid group. “This finding suggests that hybrid procedures may offer a modest survival advantage over NW-RVPA at birth weight less than or equal to 2.0 kg and over NW-BT at birth weight less than or equal to 3.0 kg,” the researchers said.

Dr. Wilder and his coauthors had no financial relationships to disclose.