*Purpose: The use of induction therapy after cardiac transplantation remains highly variable, not only in terms of which agent is used, but whether it is used at all. Further, while the dose of basilixmab is standardized, many dosing regimens can be used for anti-thymocyte globulin (ATG). Although the Internal Thoracic Organ Transplant Registry collects data regarding use of induction, including ATG, it does not capture the total dosage received by patients. We sought to characterize the experience at our center using reduced dose of ATG and the subsequent development of allograft rejection and severe infection.

*Methods: We conducted a retrospective analysis of all orthotopic cardiac transplants performed at our center from January 2014 through April 2019 (excluding dual organ). Patients receiving ATG were given 1-3 mg/kg in total. All patients followed the same protocol for tacrolimus, mycophenolate and prednisone. The primary outcome was the composite endpoint of ISHLT ≥2R rejection and infections requiring either anti-infective medication or hospitalization (including bacterial, fungal or viral) within the first 12 months following transplant. Additionally, we assessed infection which developed after a treated rejection.

*Results: 57 patients met the inclusion criteria, of those 29 received ATG (between 1 and 5 total doses, mean =2.5 doses, 1.9 mg/kg total ATG), 11 received basiliximab and 17 received no induction (28 total). Outcome data are displayed in Table 1. In the ATG group, 6 developed a ISHLT ≥2R rejection, 7 developed a severe infection (46% of the total with either complication). In the non-ATG group, 10 patients had a confirmed rejection and 9 developed severe infection (68% of the total). The most common infection was symptomatic CMV requiring antiviral treatment (50% of the total infections). Of those treated for rejection, 3/6 (50%) in the ATG group, 4/10 (40%) in the non-ATG group developed a severe infection in the 12 months following treatment of rejection. There was no significant difference between the groups with respect to rejection or infection alone, but the combined outcome was significantly less likely to occur in the ATG group (p = 0.04). 1 year survival was identical in both groups (100%).

*Conclusions: Allograft rejection and infection create significant morbidity in the first year after cardiac transplant. Although ATG is a more potent immunosuppressive agent than basiliximab, this data suggests that a reduced dosage of ATG may be able to decrease risk of significant rejection without increasing the rate of severe infections. Further studies are needed to confirm this finding.

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