*Purpose: BK polyomavirus (BKV) is a quiescent polyomavirus that is present in approximately 80% of the population and can reactivate in immunocompromised patients and impair renal function. It is a common complication after renal transplant but less understood in other solid organ transplant recipients. The aim of this study is to assess the prevalence and morbidity associated with BKV in heart transplant recipients.

*Methods: 49 heart transplant recipients from a single institution were enrolled. Baseline characteristics were compared between BK+ (defined as any positive urine or blood screen) and BK- patients (Table 1). Outcomes of interest were viruria, viremia, rejection defined as ISHLT ≥ 2R and/or AMR ≥ 1, dnDSA (de novo donor specific antibodies), and AlloMap and AlloSure (CareDx, Brisbane, CA) results.

*Results: Of the 49 patients enrolled, 10 developed BK as above. Baseline characteristics including age, sex, race, CMV serostatus, and renal function were well matched. During the first year, the incidence of rejection and development of dnDSA was similar between BK- and BK+ groups 10.5% vs 11.1% (p=0.91), 15.8% vs 22.2% (p=0.19), respectively. Median AlloMap and AlloSure results were similar in the BK- group and BK+ groups: AM 28.0(18.0, 39.0) vs 32.0(23.0, 38.0), p=0.337; AS (0.12(0.12, 1.0) vs 0.12(0.12, 0.15)), p=0.229. Finally, the cumulative incidence of the composite outcome (rejection, dnDSA, death) was not different between groups (Figure 1).

*Conclusions: We did not find clinically significant differences in AlloMap or AlloSure in heart transplant recipients with BK versus those without. Similarly, the incidence of a composite outcome was not different. These findings should reassure the community on the presence of BK in heart transplant recipients, however need to be validated in larger cohorts.

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