Since its introduction to the field of cardiac catheterization, the Melody valve opened up a whole new era in congenital heart valve interventions.
The innovative valve allows for pulmonary valve replacement using transcatheter techniques which are less invasive than surgery and have shorter recovery times. It delays the need for surgery, and in some cases allows us to avoid surgery altogether.
Unfortunately, only about 15 percent of congenital heart disease patients who need a pulmonary valve replacement are candidates for a Melody valve. This is because the Melody valve only expands to 22mm in diameter, and most patients have a right ventricular outflow tract that is much larger.
Finding ways to bring the benefits of transcatheter pulmonary valve replacement to more patients has become a major focus of the Heart Center’s Interventional Catheterization Program.
A broader range of options
“We have a few strategies right now for addressing the rest of this patient population,” says Diego Porras, MD, a cardiologist in the Heart Center’s Interventional Catheterization Program.
First of all, we have stretched the Melody valve a bit more and have been successful at extending its diameter beyond the standard 22mm. This seems to work well, at least when expanded to 24 or even 26 mm.
In patients with very large right ventricular outflow tracts and high surgical risks, we have also started performing a hybrid procedure. This requires a small anterior thoracotomy but avoids cardiopulmonary bypass. Through the anterior thoracotomy, the main pulmonary artery is plicated or banded. The valve is then delivered percutaneously and seated inside the reduced segment of pulmonary artery. Three patients have undergone this procedure to date with good short-and mid-term results.
The team has also recently started placing the Edwards SAPIEN valve, which was developed for aortic valve replacement in older adults. Although not designed for the pulmonary position, or for use in children, this approach has proven adaptable, and a recent trial in the US showed good short term outcomes using this valve in the pulmonary position.
“The SAPIEN valve comes in sizes up to 29 mm in diameter, greatly expanding our options,” says Porras. “However,” he adds, “the majority of patients have outflow tracts that are quite large, so it is important to continue to work on devices that are designed specifically for that population.”
Another valve that has been under investigation is the Medtronic native outflow valve tract device. This is a large, self-expanding stent in the shape of an hourglass, with a valve mounted in the middle section. It is specifically designed for patients with dilated outflow. Boston Children’s was part of the initial feasibility clinical trial, which also included Sick Kids Hospital in Toronto, Canada, and Nationwide Children’s in Columbus, Ohio. The device has been redesigned and will be undergoing further clinical testing in the near future.
All in all, the Heart Center’s Cardiac Catheterization Program is getting closer to its goal of expanding options for transcatheter pulmonary valves for patients with congenital heart disease. “Although we have come a long way,” says Porras, “further research and innovation will help us achieve our ultimate goal of offering this type of minimally invasive strategy to the majority of patients in need. “