Endomyocardial biopsy (EMB) is the gold standard approach for surveillance of rejection for both adult and pediatric heart transplant patients; however, the invasive procedure requires anesthesia and periodic hospital admissions that can be disruptive to children’s lives. Seeking to find a noninvasive alternative to surveillance EMB in children, Irene D. Lytrivi, M.D., a pediatric cardiologist at NewYork-Presbyterian and Columbia, and her colleagues conducted a study that explored the performance of donor-derived cell-free deoxyribonucleic acid (dd-cfDNA) fraction testing for acute rejection and presence of donor-specific antibodies in pediatric heart transplant patients.
Below, Dr. Lytrivi discusses the need for noninvasive rejection surveillance, what the study results indicate, and how this will change care in the future.
Transitioning to a Noninvasive Surveillance Protocol
Children who have heart transplants essentially exchange one disease for another when they transition into post-transplant care. Even if their hearts are functioning well, they have to see their cardiologist multiple times a year, get blood draws, and undergo invasive surveillance monitoring. Many of them know they may eventually need another heart transplant. All of this creates a very heavy emotional toll on the children and their parents, so our goal is to do whatever we can to make their lives easier and less hospital-focused.
EMB is the gold standard method for heart rejection surveillance and is one of the safest procedures in the cardiac catheterization lab. However, the biggest problem with EMB for pediatric patients, especially small children, is that it requires anesthesia. The requirement for periodic EMBs is disruptive to their lives because they must take a day or two off from school, and they cannot participate in activities such as gym for up to a week. These children already associate the hospital with their heart transplant, so coming in for repeat invasive procedures creates anxiety in many of them.
The beauty of dd-cfDNA surveillance is that it has a very high negative predictive value. When the test is negative, you can be confident that there is no rejection.
— Dr. Irene D. Lytrivi
To mitigate the impact of surveillance EMBs on children’s quality of life, we are working toward a noninvasive surveillance protocol in which we only perform routine biopsies three to five times in the first year and one or two per year for subsequent years. We perform additional biopsies in cases of significant and persistent elevation of their dd-cfDNA, which is checked every one to three months. For the past several years, our adult heart transplant team had already been performing dd-cfDNA screening, which is a blood-based, noninvasive surveillance test that measures the fraction of dd-cfDNA released from donor cells to the patient’s total DNA. A higher fraction can be an indicator of acute rejection.
The beauty of dd-cfDNA surveillance is that it has a very high negative predictive value (NPV). When the test is negative, you can be confident that there is no rejection, and when it is positive you know there may be some type of insult to the myocardium.
Researching the Efficacy of dd-cfDNA Testing
In July 2022, we added dd-cfDNA testing to our existing rejection surveillance protocol for our pediatric heart transplant patients. Under this new protocol, newly transplanted patients and prior transplant recipients presenting for routine post-transplant rejection surveillance underwent dd-cfDNA testing. In addition, they received routine echocardiograms and donor-specific antibody testing. Donor-specific antibodies can be associated with a type of rejection called antibody-mediated, which can be harder to treat when compared to the cellular rejection.
After a year and a half of rejection surveillance monitoring with the new protocol, we conducted a retrospective, observational study that compared the previous EMB-based protocol to the new protocol to test the effectiveness of dd-cfDNA screening for ruling out acute rejection and the presence of donor-specific antibodies. We looked at patients who underwent a heart transplant before age 18 at NewYork-Presbyterian Morgan Stanley Children’s Hospital of Children’s Hospital of New York, and had their dd-cfDNA testing analyzed between July 1, 2022, and December 31, 2023. We measured episodes of acute rejection, pathology grading of EMBs temporally related to dd-cfDNA sampling, and the presence of donor-specific antibodies. We analyzed 471 samples from 192 individual patients.
A slide showing positive immunofluorescence for antibody-mediated rejection.
We found NPV of 97% for antibody-mediated rejection and NPV of 93% for the detection of donor-specific antibodies with high mean fluorescence intensity values in the absence of acute rejection. This means that not only does a negative dd-cfDNA test indicate no graft rejection, it also indicates there are no donor-specific antibodies in high concentrations that can attack the graft, which makes us even more confident that the graft is healthy.
Other findings include a significant decrease in the number of biopsies, anesthesia, and intubations performed, with a 46% reduction in biopsies per patient-year. And although we haven’t proven this yet, since adopting the new protocol, we also suspect that because we now mostly perform biopsies after we see positive cell-free DNA, we are identifying rejection earlier in the disease process.
This study demonstrates that the dd-cfDNA is a valid test to rule out acute graft rejection and can reliably replace surveillance endomyocardial biopsy.
— Dr. Irene D. Lytrivi
Study Implications
Our ultimate goal is to base our surveillance strategy for pediatric heart transplant patients on a reliable, noninvasive test and only perform biopsies when there are signs of rejection. This study demonstrates that the dd-cfDNA is a valid test to rule out acute graft rejection and can reliably replace surveillance EMB. Moreover, dd-cfDNA screening brings us closer to de-medicalizing the post-transplant experience for pediatric patients, who can get periodic dd-cfDNA testing outside the hospital.
We are now working to establish age-specific cutoff points for dd-cfDNA testing before progressing to biopsy. Currently, an abnormal dd-cfDNA value is greater than 0.2%. However, small children, who tend to receive donor hearts from much larger donors, will have less of their own DNA compared to donor DNA. In those patients, we hypothesize that even without any rejection, the fraction of dd-cfDNA will be higher than 0.2%.
We also need to explore how dd-cfDNA testing integrates into a more comprehensive testing panel that may also include molecular biopsy analysis, donor-specific antibody testing, echocardiography, and other noninvasive tests. This continuous refinement of surveillance strategies brings us closer to our goal of identifying transplant rejection and graft injury earlier in the disease process, so we can treat it aggressively before it becomes an issue for a child’s heart.
