Infants born with congenital heart disease (CHD) who undergo a surgical procedure with a right ventricle-pulmonary artery (RV-PA) shunt are more likely to survive their first year and not require a heart transplant than those who have the procedure with the traditional approach, a modified Blalock-Taussig (MBT) shunt, based on the SVR trial published in the May 27 issue of the New England Journal of Medicine. However, after the first year, the two surgical procedures yield similar results.
In the first North American, multicenter, randomized trial of surgical therapy for CHD patients, the SVR (Single Ventricle Reconstruction) trial enrolled 549 newborns with CHD to compare two surgical procedures that are commonly used to treat babies born with only the functioning right ventricle to determine whether one procedure improves outcomes more than the other.
A few small studies of the RV-PA shunt have suggested that it provides better survival and other outcomes than the MBT shunt, the authors said. However, they noted that randomized clinical trials have not been conducted to demonstrate whether one procedure is better than the other.
The SVR Trial, led by Richard G. Ohye, MD, head of pediatric cardiovascular surgery division at the University of Michigan in Ann Arbor, was conducted at 15 North American clinical sites that are part of the National Heart, Lung and Blood Institute’s (NHLBI) Pediatric Heart Network
In general, three surgeries are needed to treat a single right ventricle, according to the study authors. The first procedure, the Norwood procedure, is usually performed within the first two weeks of life and is one of the highest risk procedures in congenital heart surgery. A shunt is implanted to provide a connection for blood to flow from the heart to the blood vessels in the lungs, or pulmonary arteries, so that blood can pick up oxygen and release carbon dioxide. Children later undergo a second surgery at four to six months of age; and the third procedure, known as the Fontan procedure, at 18 to 36 months.
According to the researchers, the operations are staged to allow the child to grow large enough that the corrective procedures can be performed. However, heart transplantation may be required for children with single ventricles when surgery and other treatments fail.
In the SVR trial, Ohye and colleagues randomly assigned participants shortly after birth to receive one of two types of shunts for their initial surgery, as part of the Norwood procedure. About half of the newborn participants received a MBT shunt, which places the shunt from a branch off of the aorta. The other participants received the newer type of RV-PA shunt, which is placed between the right ventricle and the pulmonary arteries.
The researchers followed study patients for at least 14 months, evaluating the number of deaths and heart transplantations in each group at one year, as well as the number of complications linked to each type of shunt.
"We found that the RV-PA shunt improved the chances of being alive without a heart transplant one year after surgery. However, the benefit appears to be limited to the first 12 months, as the two shunts showed similar results after about two years," said Ohye.
The researchers reported that after 12 months, 74 percent of infants with the RV-PA shunt survived and didn't need a heart transplant, compared to 64 percent of infants with the MBT shunt. The newborns with the RV-PA shunt, however, had significantly more complications requiring additional interventions, for example, insertions of stents or balloons to keep the shunt open.
Other outcomes, such as the size and pumping ability of the right ventricle at 14 months, were similar in the two groups of participants, the investigators reported.
“We are continuing to follow these children, and this longer follow-up will be important to determine which shunt is truly superior in the long run," Ohye said. The researchers are conducting a follow-up study to analyze the effects of the procedures in children two to six years of age.
In a preliminary analysis of participants after an average follow up of 32 months, they found similar outcomes in the group of participants with the RV-PA shunt compared to the MBT shunt.
The trial is supported by a grant from the NHLBI, which is part of the National Institutes of Health.