*Purpose: Dd-cfDNA (AlloSure, CareDx; Brisbane, CA) has been demonstrated to detect allograft injury after heart transplantation in a large and diverse patient cohort in the United States; however, little is known about the association between donor and recipient demographic characteristics and dd-cfDNA results in the early post-transplant period.

*Methods: Among heart transplant recipients enrolled in the SHORE registry, we identified clinically stable patients with longitudinal dd-cfDNA results and no history of rejection within the first post-transplant year. Univariate and multivariate analysis was used to evaluate the impact of donor/recipients variables on the median dd-cfDNA results over the first 3 months after transplant (3mAS). Not all donor/recipient variables were available for every analysis performed.

*Results: Among the 609 patients meeting criteria for inclusion in our analysis, 189 had results within the first 3 months; 3mAS was 0.053% (IQR: 0.028 – 0.098). No differences were observed in 3mAS when patients were stratified by the gender/race of either donor or recipient [Figure 1]. No correlation with recipient age was seen, however, a weak but statistically significant correlation was observed between 3mAS and donor age (Pearson’s r: 0.178, p = 0.014) [Figure 2], though 3mAS for the oldest recipients (aged 51 – 70) remained relatively low (0.047%, IQR: 0.029-0.083). In a multivariate model including all donor and recipient variables (gender, age, and race), none of the covariates significantly predicted 3mAS, and overall model performance was poor (R² = 0.059).

*Conclusions: Our investigation did not identify clinically significant associations between donor/recipient demographics (age, race, or gender) and early post-transplant dd-cfDNA levels in stable heart transplant recipients. The impact of other donor/recipient characteristics merits additional study; however, our findings support the notion that clinically significant elevations in the early post-transplant period represent either active or evolving alloimmune injury.

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