Contrast-enhanced cardiac MRI may help determine whether children who have had heart transplants are showing early signs of rejection, according to results of a pilot study published July 12 in the Journal of Heart and Lung Transplantation. The technique could reduce the need for these patients to undergo an invasive coronary angiogram every one to two years.

Physicians have relied on angiography to assess pediatric heart transplant patients for transplant coronary artery disease (TCAD), which is the primary complication that limits survival among this population.

However, repeat coronary angiogram can be problematic for these patients. “Many of these children have undergone so many operations, we have lost access to their big blood vessels,” Charles E. Canter, MD, professor of pediatrics at Washington University in St. Louis (WUSTL), Mo., said in a release. “Sometimes it’s impossible to do catheterization procedures on them.”

Samuel A. Wickline, MD, professor of medicine, cardiology division at WUSTL, and colleagues hypothesized that cardiac MR would reveal differences in coronary wall signaling intensity between transplant recipients with angiographic evidence of TCAD and those without such evidence.

The study included 29 heart transplant patients and eight healthy children who served as controls. The transplant patients underwent standard coronary angiograms as part of their normal care. They also had MRIs of the coronary arteries to examine whether the noninvasive method correlated with the degree of coronary artery disease found in the angiograms. The eight children who served as controls underwent only MRI. Researchers assessing the MRI results were blinded to the results of patients’ angiograms.

Although all of the transplant patients’ angiograms showed evidence of plaque build-up, only six were diagnosed with coronary artery disease. Contrast-enhanced MR also indicated inflamed arteries and heart muscle in these six patients, compared to both the transplant patients without coronary disease and the healthy controls. The 23 transplant patients without coronary disease showed greater coronary wall contrast-to-noise ratio than the healthy participants.

The researchers noted the noninvasive method may not be appropriate for all pediatric heart transplant patients, particularly children with a metallic stent, vessel coils or severe renal insufficiency. It also may be challenging to use cardiac MR among infants and young children due to their higher resting heart rates and need for sedation.  

“The results of this pilot study were very promising,” Canter said. The researchers have planned additional studies to confirm and refine the results. “I think eventually this could be used as a screening technique, not so much to eliminate, but to reduce, the number of angiograms,” Canter predicted.