Cumulative weight-based rabbit antithymocyte globulin dosing for induction in heart transplantation: Impact on outcomes.

Background: Optimal dose of rabbit antithymocyte globulin (rATG) for heart transplantation (HTx) induction remains uncertain. We conducted a retrospective analysis to assess the effect of cumulative rATG weight-based dosing in HTx induction. Methods: We retrospectively analyzed a total of 340 primary HTx patients (1983-2018) receiving a fixed rATG dose (125 mg daily for 3 days). Patients were retrospectively categorized based on cumulative rATG exposition: group A (<4.5 mg/kg), group B (4.5-7.5 mg/kg), and group C (>7.5 mg/kg). The primary composite outcome (death, acute rejection, and infection) and its components were evaluated at 24 months using absolute incidence, Kaplan-Meier survival curves, and Cox modeling. Results: Group A had a non-significant lower incidence of the primary composite end-point (A: 76.8%, B: 83.7%, C: 96.2%; p = 0.075), primarily driven by lower infections, with group B having significantly better survival for the primary composite end-point than group C on Kaplan-Meier curves (B vs C log-rank p = 0.044). Group B had lower mortality than group C (p = 0.012). Lower incidence of infection in group A compared to group B (p = 0.035) was also noted. No significant difference was observed in acute rejection episodes. Conclusions: At 24 months post-HTx, our findings suggest that a cumulative rATG dosing of 4.5 to 7.5 mg/kg offers the best balance of AR, mortality, and infection, mainly by reducing the risk of infections and to a lesser degree mortality, without increasing AR. A cumulative dose of <4.5 mg/kg offers the lowest risk of infection, with 4.5 mg/kg likely representing the intersection dose.