Congenital Heart Defect and Failure

Congenital Heart Defects

Congenital heart defects are structural abnormalities of the heart that are present at birth. According to the American Heart Association, roughly 36,000 infants are born with some type of heart defect annually. Doctors have identified at least 18 different types. Here is a description of some of the most common types:

• Ventricular septal defects. A ventricular septal defect (VSD) is a hole in the wall that separates the left and right sides of the lower chambers in the heart. It is the most common type of congenital heart defect, accounting for 14 to 16 percent of all cases.

• Tetrology of Fallot. This condition involves four types of problems: (1) a ventricular septal defect, (2) an obstruction in the circulation from the heart to the lungs, (3) abnormal positioning of the aorta, and (4) thickening of the muscle surrounding the lower right chamber of the heart. Tetrology of Fallot accounts for 9 to 14 percent of congenital heart defects.

• Transposition of the great arteries. In this condition, the positions of the blood vessels feeding the heart and lungs are reversed. Deoxygenated blood from the body flows back to the heart (rather than to lungs for a fresh supply of oxygen) and oxygenated blood travels back to the lungs. Survival is only possible if a baby has an abnormal opening in the wall between the left and right sides of the heart, which allows some oxygenated blood to mix with the deoxygenated blood going back to the body. Transposition of the great arteries accounts for about 10 to 11 percent of congenital heart defects.

• Coarctation of the aorta. This is a narrowing of the aorta, the main blood vessel carrying oxygenated blood from the heart to the body. It is the cause of about 8 to 11 percent of congenital heart defects.

• Atrioventricular septal defects. An atrioventricular septal defect (ASD) is a hole in the wall separating the left and right sides of the upper chambers in the heart. It accounts for 4 to 10 percent of all congenital heart defects.

Congenital Heart Defect and Heart Failure

Many congenital heart conditions require immediate surgery to save the baby’s life. Eventually, some babies who survive develop heart failure (the inability of the heart to pump enough blood to meet the needs of the body). The National Heart, Lung and Blood Institute (NHLBI) estimates, each year, about 350 infants with congenital heart disease develop heart failure.

Peter Wearden, M.D., Ph.D., Pediatric Thoracic Surgeon with Children's Hospital of Pittsburgh/UPMC, says the only long-term solution for heart failure in an infant or child is a heart transplant. Transplants are highly successful and have an 85 percent survival rate at one year. However, because of the infant’s size, they need a heart from a young donor, and there are not enough hearts available for all those who need them. According to the NHLBI, nearly 60 infants and young children on the heart transplant waiting list die before a donor heart becomes available.

One option for some young patients is ECMO (extracorporeal membrane oxygenator), an external device that pumps oxygenated blood through the body. However, ECMO can’t be used long-term because its use is associated with an increased risk for infections, bleeding and neurological impairment.

Development of Heart Pumps for Kids

Older children and adults with end stage heart failure may be supported with a ventricular assist device (VAD), a type of implantable pump that helps circulate blood through the body. A VAD may be used until a donor heart becomes available or until the weakened heart recovers and is able to once again function on its own.

There are no approved VADs for infants and small children. Wearden says the biggest obstacle is a child’s size. An adult heart is about the size of a fist, whereas a child’s heart may only be the size of a walnut. Getting miniaturized components in a device that will operate safely and smoothly has been a challenge. On top of that, major research companies have limited interest in developing heart pumps for infants and small children because there isn’t a big market for the devices.

The National Institutes of Health has granted $23.6 million to four contractors with the goal to develop and start preclinical testing of pumps for infants aged one to six months. The program is called Pumps for Kids, Infants, and Neonates, or PumpKIN. Devices in development are based on technology used in current VAD and ECMO models.

Researchers in Pittsburgh are testing a device called PediaFlow. It’s about the size of an AA battery and operates with a high speed rotor. The rotor floats by magnetic levitation to reduce the risk of forming blood clots. Oxygenated blood is pulled from the left ventricle (the weakened pumping chamber) and forced into the aorta. From there, the blood flows on through the body. The rate of flow can be varied to accommodate infants of different sizes and needs.

Currently, the pumps being designed through PumpKIN are still in development stages. Wearden hopes the PediaFlow will be ready for human clinical trials within three years. Other PumpKIN participants are Ension, Inc. in Pittsburgh, The University of Maryland in Baltimore and Jarvik Heart, Inc. in New York City.

For information about NIH studies for children with congenital heart disease, click here.

source: wsoctv