The study is published in the May 26 advance online edition of the New England Journal of Medicine.
The randomized, multi-centre surgical trial was conducted by the Pediatric Heart Network (PHN), a National Institutes of Health sponsored consortium of eight North American institutions. The Hospital for Sick Children (SickKids) is the only Canadian member of the PHN and was the only Canadian centre out of 15 to participate in this study. The study evaluated 555 operations performed on babies born with Hypoplastic Left Heart Syndrome (HLHS).
HLHS is a complex heart defect where the left side of the heart does not form. It is the most common severe congenital heart defect, accounting for 3.8 per cent of all congenital heart defects. Children with HLHS typically undergo at least three major heart surgeries to establish a reliable flow of blood from the heart to the body, while ultimately directing blood to the lungs, without the direct assistance of the heart. The Norwood procedure, usually performed right after birth, is the most difficult to perform and has the highest risk of death.
“The risk of death during the first year, after this procedure is 29 per cent, which is why it is so important for us to find better ways to treat these babies,” says Dr. Brian McCrindle, SickKids’ principal investigator for the study, Staff Cardiologist and Senior Scientist in Child Health Evaluative Sciences and Professor in the Department of Paediatrics at the University of Toronto. “Being able to follow such a large group of patients should make a significant impact on how we will be able to care for children with HLHS in the future.”
There are two common ways to perform the Norwood procedure. The classic procedure is referred to as Norwood using a modified Blalock-Taussig shunt (MBTS). MBTS is a part of the procedure that involves placement of a connecting tube from the aorta (which directs blood to the body) to the pulmonary artery that supplies blood to the lungs. The alternate procedure is called Norwood using right ventricle-to-pulmonary artery shunt (RVPAS). RVPAS establishes blood flow to the lungs by connecting the right ventricle directly to the pulmonary artery.
With MBTS, 64 per cent of the babies survived in their first year without a transplant, while the remaining babies either required a transplant or did not survive. Seventy-four per cent of the RVPAS babies survived to the age of one without a transplant. However, RVPAS was also found to be associated with a higher rate of unintended cardiovascular interventions and complications.
“We must be cautious in interpreting these results and refrain from labeling one procedure as the better option,” says Dr. Seema Mital, Staff Transplant Cardiologist and Associate Scientist at SickKids and Associate Professor in the Department of Paediatrics at the University of Toronto. “Our early results indicate increased survival associated with RVPAS, but also suggest that this benefit may not continue past the first year of life. We are still studying how these procedures impact survival and complication rates beyond one year.”
The research also showed that patient care provided by a comprehensive interdisciplinary clinical team had an impact on results. The centres with the most experienced clinical teams had the best outcomes regardless of which operation was performed.
Doctors at SickKids’ Labatt Family Heart Centre are currently developing an alternative to the Norwood procedure that avoids the initial surgery. Instead the procedure is performed using less invasive means in the catheterization laboratory.
The study was supported by the National Heart, Lung and Blood Institute and SickKids Foundation.
The Hospital for Sick Children (SickKids) is recognized as one of the world’s foremost paediatric health-care institutions and is Canada’s leading centre dedicated to advancing children’s health through the integration of patient care, research and education. Founded in 1875 and affiliated with the University of Toronto, SickKids is one of Canada’s most research-intensive hospitals and has generated discoveries that have helped children globally. Its mission is to provide the best in complex and specialized family-centred care; pioneer scientific and clinical advancements; share expertise; foster an academic environment that nurtures health-care professionals; and champion an accessible, comprehensive and sustainable child health system. SickKids is proud of its vision of Healthier Children. A Better World.™ For more information, please visit www.sickkids.ca.
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