How Organ Shortages Affect the Smallest of Heart Transplant Patients

The ongoing shortage of donor hearts for children who need them stems from multiple causes, including a lack of donor awareness, organ allocation issues, and not enough organs that are of sufficient quality to transplant.

Currently, new hearts for kids are still hard to find, and they are even scarcer for babies. Infants are particularly hard to match with a heart. Donor hearts must be a close genetic match to the patient, the right size (a newborn’s heart is about as big as a walnut), and disease-free.

“We don’t like to see the tragedy of another kid having to die to save a kid’s life—and fortunately, infants don't die very often,” says John David Cleveland, MD, Attending Cardiothoracic Surgeon in the Heart Institute at Children’s Hospital Los Angeles. “But this means there is an even greater shortage of donor hearts for infants who need them, and there is not much flexibility on organ size for our smallest patients."

Infants left in the organ transplant gap

Children who have heart failure are kept alive until transplant by specialized intravenous drugs and a variety of “bridge” technologies, including ventricular assist devices (VADs) such as the PediMag or Berlin Heart—mechanical pumps that help the heart circulate blood to the body—and even the intensive heart and lung support of extracorporeal membrane oxygenation (ECMO). Although these bridge methods can support adults and older children, they don’t work well for the smallest babies. They are not sized properly or responsive enough to support tiny hearts and delicate vasculature long term.

According to the most recent national figures from the Scientific Registry of Transplant Recipients (SRTR), in 2023, 1,248 children aged 17 years or younger were on the waiting list for a heart.

Of those:

• 26% were between 1 to 5 years old.
• 21.1% were younger than 1 year old.

Among those waiting for a heart transplant who were removed from the list, 72.4% received a transplant, 8.5% died, and 3.8% were considered too sick to undergo transplant.

These very sick babies have the worst outcomes on VADs, which is the only alternative that we have to keep them alive until transplant. In fact, 60-70% die within the first 3 months on VAD support due to high rates of strokes and bleeding, and another 30% will develop a major infection during their time on mechanical support.

 Dr. John David Cleveland

The transplant outlook gets even more complicated for infants under 1 year of age born with certain severe congenital heart conditions, such as single ventricle heart disease in which a lower chamber of the heart is undeveloped, and types of hypoplastic left heart syndrome, a congenital heart defect where the left ventricle is severely underdeveloped.

Infants born with these congenital heart conditions must survive an average of at least 4 to 6 months on mechanical heart (VAD) support before they receive a donor heart. “These very sick babies have the worst outcomes on VADs, which is the only alternative that we have to keep them alive until transplant,” says Dr. Cleveland.

“In fact, 60-70% die within the first 3 months on VAD support due to high rates of strokes and bleeding, and another 30% will develop a major infection during their time on mechanical support. And children kept alive on mechanical support must remain in an ICU for several months while waiting for a heart."

Making more organs available

The pediatric organ donation system sprawls across 50 states and more than 100 pediatric heart centers and has many different participants who must coordinate to get a heart to a child who needs one. Physicians and researchers are working on multiple initiatives to improve the organ distribution and allocation system, including incorporating artificial intelligence to reduce the number of donated organs that are not transplanted. These include more recent techniques in transplanting hearts from donors with different blood types (called ABO-incompatible, or ABOi), that have made more donor hearts available for newborns and children.

Technologies for preserving transplanted organs that are available for adult hearts are not yet approved for pediatric-sized hearts, so children’s hospitals that perform heart transplants still preserve donor organs with a solution and transport them in coolers on ice.

Despite all efforts to increase the available supply of organs, there are still not enough hearts available for children with end-stage heart failure that cannot be fixed surgically. ”We hope that ongoing reforms of the organ transplant system will make more donated organs available for our patients,” says Dr. Cleveland. “These babies have no real alternative to help them through the waitlist, unless the time to transplant radically shortens. In the meantime, we keep working on developing realistic strategies to better support the tiniest of our patients until a human heart becomes available.”