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Bridging The Gap

Image of Dr. Minoo Kavarana in surgery as he places a reversible pulmonary artery band into a pediatric patient.
Dr. Minoo Kavarana places a reversible pulmonary artery band into a pediatric patient.

MUSC’s heart failure team uses novel approach to help pediatric patients

By Celia Spell

As the organ responsible for taking blood from the body and enriching it with oxygen before recirculating it, the heart provides a vital function for human existence. Any problem with the muscles involved could deprive the body of the circulating blood, and therefore oxygen, that it needs to carry on.

Both ventricles keep the heart functioning and circulating blood, but the left ventricle is the one responsible for supplying blood to the rest of the body while the right ventricle sends blood to the lungs. In left sided heart failure, or left ventricular dysfunction (LVD), the left pump cannot keep up with the body’s demands.

Heart failure in general, and especially LVD, has been widely studied and treated in adults but not in children, so physicians take the data that is available and combine it with their clinical experience to treat infants, young children and even teenagers with LVD.1

Children can be born with heart defects that then lead to heart failure when attempts at surgical repair and medical intervention do not work. They can also develop heart failure from a viral infection, but it is rare, and children are more likely to recover with temporary help.

“Most young patients with congestive heart failure will likely need a heart transplant,” said Minoo Kavarana, M.D., a pediatric cardiothoracic surgeon at MUSC Children’s Health. But after hearing about a new procedure in Germany, Kavarana talked with the rest of the team about bringing it to the Southeast.

It takes an average of 2 to 6 months for a child on the transplant list to find a heart, and many are too sick to wait that long. Historically, surgeons have implanted assist devices into the chamber that needs help pumping blood. While these devices do not remove the need for a transplant, they give the child more time to wait for a heart to become available. They also provide the chance to recover function in their other organs as well as improve their nutrition and overall condition, which makes them a better candidate for a transplant.

Many assist devices are initially designed for adults and then modified to treat children; however, this can lead to infants with assist devices (such as the Berlin heart) having a high risk of complications that may lead to stroke.2 Studies that indicated a high incidence of embolic stroke, bleeding and infection with assist devices led the heart failure team at MUSC to look into a new procedure: reversible pulmonary artery banding (PAB).

As one of the first centers in the country to offer the procedure, MUSC brings a new treatment option to parents. The procedure involves placing a band around the main pulmonary artery, the vessel which carries blood from the right ventricle to the lungs for oxygenation. By increasing the pressure in the artery, the band causes the partition between the right and left sides of the heart, the ventricular septum, to alter its orientation toward the left. This slight change provides more support to the valves and pumping chambers on the left side of the heart.

Abnormally high pressure on the left side of the heart can shoot from the normal range of 5-10 millimeters of mercury (mm) to 20-30 mm, but with PAB this pressure can drop to 10-20 mm.

This decrease in pressure may allow the physician to wean these pediatric patients off both the ventilator and medications required to support their blood pressure and then sometimes even send them home. The key to the procedure’s success is the patient’s type of heart failure. If the patient’s condition also affects the right ventricle, the pulmonary artery band would put too much pressure on the right side of the heart, so physicians don’t consider the reversible PAB an option in this case.

While the procedure has been performed only a few times at MUSC for children with LVD, some have recovered and are no longer on the transplant list, and others have used the pulmonary artery band in place of assist devices while waiting for a transplant to become available.

“We like to think of this procedure as either a bridge to transplantation or even a bridge to recovery,” said Kavarana.

MUSC, Loma Linda University and Texas Children’s Hospital are among the first institutions in the United States to use this heart failure treatment technique for LVD in infants. The heart failure team at MUSC explored the technique due to its minimally invasive nature when compared to assist devices, its reversibility and the fact that the child’s heart does not need to be stopped during surgery.

“The next step is to look into an adjustable band known as a Flo Watch,” said Kavarana. “It could be adjusted as the child’s blood pressure and condition change.” The heart failure team at MUSC is currently working with Clemson University to assess the band in a computational flow model and then in animal models before its use in the clinic.

References

1. Jayaprasad N. Heart Views. 2016;17(3):92–99. doi:10.4103/1995-705X.192556.

2. Adachi I, et al. J Thorac Dis. 2015; 7(12):2194–2202. doi:10.3978/j.issn.2072-1439.2015.12.61.