The MINT trial, which included 3504 patients with acute MI and anemia, shows a trend favoring liberal transfusion, indicating a potential for improved outcomes.
New data from a trial of more than 3500 patients suggests a more liberal transfusion strategy could improve outcomes in patients with acute myocardial infarction and anemia.
Results, which were presented at the American Heart Association Scientific Sessions 2023, suggest the MINT trial failed to meet its primary endpoint of statistical significance for the composite of all-cause death and recurrent heart attack through 30 days, but results pointed to a nonsignificant trend toward benefit for those in the liberal transfusion group, with a primary event occurring among 16.9% and 14.5% of the restrictive and liberal transfusion groups, respectively.1
“Low red blood count or anemia is common among people hospitalized with heart attack,” said study investigator Jeffrey L. Carson, MD, provost, distinguished professor of medicine and Richard C. Reynolds chair in general internal medicine at Rutgers Robert Wood Johnson Medical School.2 “We believe our results suggest a more liberal transfusion approach may be beneficial for these patients without significant risk.”
Funded by the National Heart, Lung, and Blood Institute, the Myocardial Ischemia and Transfusion (MINT) trial was designed with the intent of expanding the current evidence base for future guidelines on transfusion strategies in patients with myocardial infarction. An open-label, interventional trial conducted at 144 sites in the United States, Canada, France, Brazil, New Zealand, and Australia, MINT randomized patients with myocardial infarction and a hemoglobin level of less than 10 g per deciliter to a restrictive transfusion strategy or a liberal transfusion strategy, which were defined as a hemoglobin cutoff for transfusion of 7 or 8 g/dL and a hemoglobin cutoff for transfusion of less than 10 g/dL, respectively.1
For inclusion in the trial, patients were required to be at least 18 years of age with STEMI or NSTEMI and a hemoglobin level of less than 10 g/dL within 24 hours of randomization. Investigators noted patients with type 1, 2, 4b, or 4c myocardial infarction were eligible for enrollment.1
In total, 3504 underwent randomization and were included in the study’s primary analysis. This cohort had a prerandomization mean hemoglobin level was 8.6 g/dL, a mean age of 72.1 years, and 45.5% were women. Investigators noted type 2 and type 1 myocardial infarction made up the majority of the cohort—accounting for 55.8% and 41.7% of the overall cohort, respectively.1
Patients included in the trial were followed for 30 days for a primary composite endpoint of myocardial infarction of death at 30 days. The trial also included multiple prespecified secondary outcomes, such as individual components of the primary outcome and a composite of death, myocardial infarction, ischemia-driven unscheduled coronary revascularization, or readmission to the hospital for an ischemic cardiac condition within 30 days.1
Upon analysis, results indicated the mean number of red-cell units transfused was 0.7 (Standard Deviation [SD], 1.6) and 2.5 (SD, 2.3) in the restrictive-strategy and liberal-strategy groups, respectively. Further analysis suggested the restrictive strategy group had a mean hemoglobin level was 1.3 to 1.6 g/dL less than the liberal strategy group 1 to 3 days after randomization.1
Analysis of the primary outcome suggested myocardial infarction or death from any cause at 30 days occurred among 16.9% of restrictive strategy group and 14.5% of the liberal strategy group, which correlates to crude risk ratio (RR) of 1.16 (95% Confidence Interval [CI], 1.00 to 1.35). Upon adjustment for site and incomplete follow-up in 57 patients, results suggested those in the restrictive transfusion group had a 15% increase in risk of a primary outcome event.1
Additional analysis of outcomes indicated death occurred among 9.9% of the restrictive-strategy group and 8.3% of the liberal strategy group (RR, 1.19; 95% CI, 0.96 to 1.47) while myocardial infarction occurred among 8.5% and 7.2% of the patients, respectively (RR, 1.19; 95% CI, 0.94 to 1.49).1
“The study results require a nuanced interpretation. While the trial did not produce a statistically significant difference between the two transfusion strategies for the primary outcome, the results suggest the possibility of liberal transfusion benefits without undue risk,” Carson said.2 “The MINT results suggest a liberal transfusion strategy may be the most prudent approach for patients with heart attack and anemia.”