The Effect of Restrictive vs Liberal Blood Transfusion Strategy on Subsequent Myocardial Infarction Type

BACKGROUND: Data on the differential impact of interventions on subsequent myocardial infarction (MI) type are limited. OBJECTIVES: This post-hoc analysis was done to evaluate the 30-day rate of subsequent MI by type (ie, type 1 and 2) among patients enrolled in the MINT (Myocardial Ischemia and Transfusion; NCT02981407) trial. METHODS: Subdistribution HRs and cumulative incidences of subsequent MI types were computed using Fine-Gray subdistribution models that accounted for the competing risk of death and other MI types, if applicable. Effect modification of treatment strategy by index MI type was tested using log-binomial regression models. RESULTS: Among 3,504 MINT trial patients, 275 (7.8%) had a 30-day subsequent MI, of which 118 (43%) were type 2 MI, 79 (28%) were uncertain MI type, 40 (15%) were type 4 MI, and 38 (14%) were type 1 MI. The rate of subsequent type 2 MI in patients randomized to the restrictive vs liberal transfusion was 3.5% (n = 61) vs 3.2% (n = 57) (HR: 1.07; 95% CI: 0.74-1.53) as compared with a subsequent type 1 MI rate of 1.3% (n = 23) vs 0.9% (n = 15) (HR: 1.53; 95% CI: 0.80-2.94). CONCLUSIONS: Among patients with MI and anemia, subsequent MI occurred within 30 days in 7.8% of patients, with type 2 MI occurring 3 times more often than type 1 MI. A differential effect of the restrictive vs liberal transfusion strategy on the type of subsequent MI (eg, type 1 vs type 2) was not observed.