Columbus, OH - March 2016
Pediatric heart surgeons typically have a choice of shunt type in stage 1, or Norwood, palliation for children with hypoplastic left heart syndrome (HLHS). The right ventricle to pulmonary artery (RVPA) conduit has been shown to have better outcomes than the modified Blalock-Taussig (MBT) shunt in the first year after the Norwood procedure. But that advantage disappears thereafter, and the RVPA conduit may carry a greater risk for early intervention or progressive right ventricular dysfunction over time.
A recent multi-institution study, published in The Journal of Heart and Lung Transplantation, has given heart teams another piece of information to consider regarding RVPA and MBT shunts: the RVPA conduit provides a potential survival advantage over the MBT shunt when a transplant is needed in the first few months of life.
“Once the patient is transplanted, there is no difference,” says Robert J. Gajarski, MD, senior author of the study and Section Chief of The Heart Center at Nationwide Children’s Hospital. “It’s the period waiting for a transplant that is the issue. MBT shunt patients are listed for transplant earlier, and their outcomes tend to be worse.”
Using the Pediatric Heart Transplant Study consortium database, the authors identified 190 children younger than 6 years of age who were diagnosed with HLHS, were listed for heart transplantation and had undergone Norwood palliation. The cohort included 111 patients with the RVPA conduit and 79 with the MBT shunt.
The MBT group members were younger at listing for transplant (median age 1.3 years vs. 1.8 years), had a lower median weight, were more likely to be mechanically ventilated and were less likely to have reached Stage 2 (Glenn) palliation. Among all of the patients listed for transplant, 3-month survival was lower for the MBT group than the RVPA group (74 percent vs. 91 percent).
The decreased survival is likely driven by the youngest MBT patients, the ones listed before Glenn palliation (which commonly occurs between 4 and 6 months of age). Glenn physiology has been shown to be more stable, and once Glenn palliation occurred, outcomes were comparable between the MBT and RVPA groups.
The need for a heart transplant is not usually predictable prior to Norwood palliation. A surgeon may reasonably choose the MBT shunt, and then find later that a transplant is necessary. Knowing that MBT shunt patients can fare worse while waiting may give the transplant team some insight in supporting those patients, says Dr. Gajarski, who is also a professor of Pediatrics at The Ohio State University College of Medicine.
“The goal of care for the managing team then becomes optimizing the infant’s clinical status by minimizing heart failure symptoms and maximizing nutrition,” he says. “Other strategies might include blood group incompatible listing, which carries no increased risk to the patient, or early conversion to Glenn physiology if the perioperative risk is acceptable.”
The study may also have implications for the United Network for Organ Sharing and their heart allocations for higher risk infants, Dr. Gajarski says.
Nationwide Children’s is known for its innovative “hybrid approach” for HLHS palliation, which delays the need for neonatal heart-lung bypass and its potential adverse effects on growth and development until a child is 4 to 6 months of age, when this risk may be reduced. Not enough hybrid cases were part of the study cohort to be analyzed, Dr. Gajarski says.
Carlo WF, West SC, McCulloch M, Naftel DC, Pruitt E, Kirklin JK, Hubbard M, Molina KM, GajarskiR. Impact of initial Norwood shunt type on young hypoplastic left heart syndrome patients listed for heart transplant: A multi-institutional study. The Journal of Heart and Lung Transplantation. 2015 Oct 30. [Epub ahead of print]