Key Points:
- The MINT trial found that among patients with acute MI and anemia, those randomized to a liberal transfusion strategy had lower rates death or MI at 30 days compared to a restrictive strategy; this result approached but did not reach statistical significance.
- This prespecified subgroup analysis found that the restrictive strategy resulted in a higher rate of death or MI in patients with Type 1 but not Type 2 MI, however the p-value for interaction was not significant.
- Further research is needed, as this analysis was likely underpowered to detect a clinically significant differential response to transfusion strategy based on MI type.
The Myocardial Ischemia and Transfusion (MINT) tested a restrictive transfusion strategy (Hgb threshold 7-8g/dL) versus a liberal transfusion strategy (Hgb threshold 10g/dL) among patients with acute myocardial infarction (MI) and anemia.1 The primary outcome of death or MI at 30 days was higher in the restrictive arm, but it did not reach the pre-specific cut off for statistical significance (RR 1.15, 95% CI 0.99-1.34), suggesting a potential benefit to a liberal transfusion strategy. Because the underlying pathophysiology of Type I and Type II MI are different, they might have a differential response to the transfusion strategies tested in MINT.
On April 7, 2024, the principal results of the “Restrictive Versus Liberal Transfusion in Patients with Type 1 or Type 2 MI: A Prespecified Subgroup Analysis of the MINT Trial” were presented at ACC Scientific Sessions 2024. The purpose of this analysis was to evaluate the effects of a restrictive versus liberal transfusion strategy in MINT patients by MI type.
Overall, 3,415 MINT participants were included in this analysis: 1460 with a Type 1 MI and 1955 with a Type 2 MI. The average age was 72 years. Hemoglobin levels at hospital day 3 were similar in Type 1 and Type 2 patients were similar. Among patients with Type 1 MI, those in the restrictive arm had higher rates of death or MI than those in the liberal arm (RR 1.32 [95% CI 1.04-1.67]). No significant difference in the primary outcome was seen among patients with Type 2 MI (RR 1.05 [0.85-1.29)]). However, the p-value for interaction was 0.16, indicating that there was the differential effect of transfusion strategy based on MI type was not statistically signficant.
This was a subgroup analysis, hence it was likely underpowered to detect clinically meaningful differential effects. In addition, index MI type was classified by enrolling cite, not a central adjudication process, and the treatment team was not masked to the assigned transfusion strategy.
Andrew P. DeFilippis, MD, MSc, of Vanderbilt University Medical Center concluded: “These inconclusive results require further study…Although the results of this analysis do not provide statistical certainty, the results inform clinicians in the treatment of patients with acute MI and anemia. A restrictive transfusion strategy may be harmful, particularly in those with Type 1 MI.”
- Carson JL, Brooks MM, Hébert PC, et al. Restrictive or Liberal Transfusion Strategy in Myocardial Infarction and Anemia. New England Journal of Medicine. 2023;389(26):2446-2456. doi:doi:10.1056/NEJMoa2307983