Hypoplastic left heart syndrome (HLHS) is a rare but serious form of congenital heart disease that leaves the left pumping chamber (ventricle) of the heart severely underdeveloped. Children born with HLHS can’t pump enough oxygenated blood from their heart to the rest of their body and need surgery as soon as possible to survive. Treatment ultimately involves three corrective surgeries throughout the infant and toddler years.
The first surgery, known as the Norwood procedure, is the riskiest of the three. Ideally performed within the first week of life, the procedure re-routes the heart’s plumbing to ensure enough oxygenated blood is circulated while the child grows big enough for the second surgery. A device called a graft is used to connect the fully-functional right ventricle to the aorta, bypassing the stunted left ventricle, for proper blood flow. However, with each ventricular contraction, the graft gets squeezed, which can cause it to shift or lose its shape over time. Repeat interventions to adjust the graft are often needed.
Thinking outside the box
A sturdier graft did exist, designed for adults with kidney failure who needed help with blood flow in their arms and/or legs. “Doctors started to notice that the grafts they were using would often get smushed or kinked inside the body,” says Christopher Baird, MD, a cardiac surgeon at the Boston Children’s Hospital Heart Center, who specializes in valve disease. “So they added a structural ring to provide more stability.”
Pediatric cardiac surgeons soon took interest in this new graft, sensing the potential application for HLHS patients. Beginning in 2009, a handful of pediatric cardiac centers, including Boston Children’s, began using the ring-reinforced graft for Norwood procedures.
“The internal, reinforcing rings help the device better retain its position within the heart, decreasing the need for a repeat intervention,” says Baird. So far, the new version, in use at Boston Children’s since 2009, seems to be improving patient outcomes—at least within the first year of life.
In a recent paper published in the Journal of Thoracic and Cardiovascular Surgery, Baird and his colleagues James Bentham, MD, PhD, Audrey Marshall, MD, Diego Porras, MD, and Rahul Rathod, MD, compared infants who had received standard grafts with infants given ring-reinforced grafts. They looked at mortality rates, intervention rates and overall heart health indicators at the one year post-surgery mark.
Across both groups, no marked difference was found in mortality rates by age one year. But when it came to the number of interventions that occurred within that first year, there was a substantial difference: 69 percent of patients with the standard conduit had a repeat intervention as opposed to 35 percent of patients with the ring-reinforced conduit.
Furthermore, the ring-reinforced group exhibited higher pulse pressures and improved pulmonary artery growth—both signs of improved heart health—when compared with the standard group.
“It’s our current standard of care at the Heart Center to use this new version,” says Baird.
Further research is needed to determine whether the new graft’s benefits remain constant throughout the second and third HLHS surgeries, and whether there is any residual ventricular impairment.
“We are always improving upon our surgical techniques, and these results suggest that a reinforced graft may be better at preserving heart function,” says Marshall. The fact that standard grafts did not correlate with higher mortality is comforting—but saving patients from repeat interventions is also pretty great.