Does MI type matter when it comes to transfusion strategy for patients with MI, anaemia?

In patients with acute myocardial infarction (MI) and anaemia, a restrictive blood transfusion strategy may potentially result in poorer outcomes for those with type 1 but not those with type 2 MI, according to a study.

Researchers analysed data from the Myocardial Ischemia and Transfusion (MINT) trial to determine whether the effects of transfusion varied among patients with a type 1 or a type 2 MI and anaemia. The outcomes were death or MI at 30 days.

The analysis included 3,415 patients with MI and anaemia, of which 1,460 had type 1 and 1,955 had type 2 MI. These patients were randomly allocated to a restrictive (threshold, 7–8 g/dL) or a liberal (threshold, 10 g/dL) transfusion strategy.

The primary outcome of death or MI occurred in 16 percent of patients with type 1 MI and in 15.4 percent of those with type 2 MI. The incidence of the primary outcome was notably higher among patients with type 1 MI who underwent a restrictive vs liberal transfusion strategy (18.2 percent vs 13.8 percent; relative risk [RR], 1.32, 95 percent CI, 1.04–1.67).

Among patients with type 2 MI, on the other hand, the incidence of the primary outcome did not differ between those who underwent the restrictive and those who underwent the liberal transfusion strategies (15.8 percent vs 15.1 percent; RR, 1.05, 95 percent CI, 0.85–1.29).

The test for a differential effect did not show a statistically significant interaction between transfusion strategy and MI type (p=0.16).