Which Shunt Best for Repairing Congenital Heart Defects?

A new study compares two surgical strategies for repairing the severely underdeveloped heart, the most common severe congenital heart defect.

Infants born with a critically underdeveloped left side of their hearts require three surgeries to correct the problem. The first stage involves the Norwood Procedure, which is used to form a connection that delivers blood from the heart to the pulmonary arteries, to pick up oxygen. This can be done by two procedures; the traditional version uses a modified Blalock-Taussig shunt (MBTS), which connects the aorta the pulmonary artery; the modified procedure uses a right ventricle to pulmonary artery (RV-to-PA) shunt to connect the functioning right ventricle to the pulmonary artery.

Researchers at the University of Michigan Medical School (Ann Arbor, USA) and other members of the international Pediatric Heart Network conducted a 15-center trial involving 555 infants (61% male) who were randomized to receive either the RV-to-PA shunt or MBTS procedure. The initial results of the study found that at 12 months, significantly more babies survived without requiring a heart transplant with the RV-to-PA shunt (74%) compared to the MBTS (64%). The RV-to-PA shunt, on the other hand, had more complications, necessitating 240 interventions (87.6 for every 100 babies), such as adjusting the shunt or using stents to keep it open; far fewer cardiovascular interventions were needed--183, or 66.5 for every 100 babies--in the MBTS group. However, at an average of two years, the transplant-free survival advantage of RV-to-PA (68%) over MBTS (62%) had diminished and it was no longer significant. The study was presented at the American Heart Association (AHA) scientific sessions, held during November 2009 in Chicago (IL, USA).

"Early results seem to favor the RV-PA shunt, but by two years there is no longer any survival advantage. It is still unknown which will turn out to be better over the long term,” said lead author Richard Ohye, M.D., an associate professor of surgery at the U-Mich. "Ongoing surveillance as these children grow and undergo the final surgical procedure will be very important to determine the proper roles of the shunts.”

Both shunt procedures have theoretical advantages and disadvantages. The downside of the MBTS is that it takes blood away from the arteries feeding the heart muscle. The RV-to-PA shunt does not do this, but requires an incision into the single working ventricle, creating scarring that might interfere with later function.

Related Links:
Michigan Medical School
Pediatric Heart Network