Background Cardiac acute rejection (AR) is a risk factor for poor outcomes, however there are limited risk prediction models to stratify patients for death or sustained LV dysfunction. This study assesses the prognostic utility of percentage donor-derived cell-free DNA (%dd-cfDNA) at the diagnosis of AR for poor outcomes.

Methods The prospective multicenter GRAfT study enrolled heart transplant recipients and collected serial plasma samples to quantitate %dd-cfDNA. AR was defined as acute cellular rejection (ACR), antibody-mediated rejection (AMR), as well as biopsy-negative AMR (donor-specific antibody positivity with LV dysfunction). AR was classified as mild-to-moderate (ACR grade 2 or AMR grade 1) or severe (ACR grade ≥3, AMR grade ≥2, or DSA+/LV dysfunction) and further stratified by a %dd-cfDNA threshold of 0.25%. Regression models assessed the association between AR and %dd-cfDNA levels at the AR diagnosis with the primary composite outcome of sustained LVEF decline <50% and/or death.

Results The study included 275 patients and 3,190 %dd-cfDNA assessments. Over the median of 4.6 (IQR 1.8 - 5.0) years follow-up, 51 patients experienced the composite outcome of death or prolonged EF reduction, and 75 patients developed AR, including 16.2% patients with ACR, 9.4% with pathologic AMR, and 6.6% with DSA+/LV dysfunction. Thirty-two (42.7%) patients had severe AR and 43 (57.3%) had mild-to-moderate AR. Severe—but not mild-to-moderate— AR was associated with an increased risk of the primary composite endpoint (HR = 5.17, 95% CI 2.38 − 11.3, p < 0.001). Among those with severe AR, a %dd-cfDNA level greater than 0.25% at diagnosis was associated with a higher risk of the primary outcome (HR, 6.06, 95% CI, 1.78– 20.6; p = 0.004). Percent dd-cfDNA remained elevated in severe AR patients with adverse outcomes.

Conclusion Severe AR with high %dd-cfDNA levels is associated with an increased risk of poor outcomes, offering novel prognostic utility.

What is New?

Percent donor-derived cell-free DNA (%dd-cfDNA) can risk stratify cardiac transplant patients with severe acute rejection for death and/or prolonged EF reduction

Percent dd-cfDNA remain persistently elevated in patients with severe acute rejection who develop poor outcomes, which could reflect ineffective treatment.

In the contemporary era of cardiac transplantation, acute rejection defined by biopsy or by donor specific antibodies plus LV dysfunction is associated with poor outcomes

What are the Clinical Implications?

Percent dd-cfDNA could serve as a bedside tool to risk stratify patients with severe acute rejection for poor outcomes.

Trends of %dd-cfDNA could serve to monitor response to treatment for severe acute rejection.

Percent dd-cfDNA levels at diagnosis of rejection could be leveraged for patient selection in clinical trials to test novel therapies or treatment strategies.

The authors have declared no competing interest.

Genomic Research Alliance for Transplantation Study, NCT02423070, ClinicalTrials.gov

This research was supported in part by the Intramural Research Program of the National Institutes of Health (NIH). The contributions of the NIH authors were made as part of their official duties as NIH federal employees, are in compliance with agency policy requirements, and are considered Works of the United States Government. However, the findings and conclusions presented in this paper are those of the authors and do not necessarily reflect the views of the NIH or the U.S. Department of Health and Human Services.

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The details of the IRB/oversight body that provided approval or exemption for the research described are given below:

The institutional review boards of all centers and the NHLBI approved the study, and patients provided their informed consent before enrollment. This study adheres to the principles of the Declaration of Helsinki and the ISHLT statement on Transplant Ethics.

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