Restrictive versus Liberal Transfusion in Myocardial Infarction - A Patient-Level Meta-Analysis

Abstract

Background: Clinical guidelines have concluded that there are insufficient data to provide recommendations for the hemoglobin threshold for the use of red cell transfusion in patients with acute myocardial infarction (MI) and anemia. After the recent publication of the Myocardial Infarction and Transfusion (MINT) trial, we performed an individual patient-level data meta-analysis to evaluate the effect of restrictive versus liberal blood transfusion strategies.

Methods: We conducted searches in major databases. Eligible trials randomly assigned patients with MI and anemia to either a restrictive (i.e., transfusion threshold of 7-8 g/dl) or liberal (i.e., transfusion threshold of 10 g/dl) red cell transfusion strategy. We used individual patient data from each trial. The primary outcome was a composite of 30-day mortality or MI.

Results: We included 4311 patients from four trials. The primary outcome occurred in 334 patients (15.4%) in the restrictive strategy and 296 patients (13.8%) in the liberal strategy (relative risk [RR] 1.13, 95% confidence interval [CI], 0.97 to 1.30). Death at 30 days occurred in 9.3% of patients in the restrictive strategy and in 8.1% of patients in the liberal strategy (RR 1.15, 95% CI, 0.95 to 1.39). Cardiac death at 30 days occurred in 5.5% of patients in the restrictive strategy and in 3.7% of patients in the liberal strategy (RR 1.47, 95% CI, 1.11 to 1.94). Heart failure (RR 0.89, 95% CI, 0.70 to 1.13) was similar in the transfusion strategies. All-cause mortality at 6 months occurred in 20.5% of patients in the restrictive strategy compared with 19.1% of patients in the liberal strategy (hazard ratio 1.08, 95% CI, 1.05 to 1.11).

Conclusions: Pooling individual patient data from four trials did not find a definitive difference in our primary composite outcome of MI or death at 30 days. At 6 months, a restrictive transfusion strategy was associated with increased all-cause mortality. (Partially funded by a grant from the U.S. National Heart, Lung, and Blood Institute [R01HL171977].).

Figure 1.

Transfusion Threshold Trials in Patients with Acute Myocardial Infarction.

Figure 2.

Primary and Secondary 30-Day Outcomes. Risk difference models using random effects did not converge for bacteremia and we report risk difference estimates that did not use random effects for that outcome. CI denotes confidence interval; DVT, deep venous thrombosis; MACE, major adverse cardiac events; MI, myocardial infarction; PE, pulmonary embolism; and RR, relative risk. Arrow indicates lower limit of confidence interval extends beyond 0.5.

Figure 3.

Cumulative Incidence of Death or Myocardial Infarction at 30 Days and All-Cause Death at 180 Days. The rate of death or MI at 30 days was 15.4% in the restrictive transfusion strategy and 13.8% in the liberal transfusion strategy. The rate of all-cause death at 30 days was 9.3% in the restrictive transfusion strategy and 8.1% in the liberal transfusion strategy. The rate of all-cause death at 180 days was 20.5% in the restrictive transfusion strategy and 19.1% in the liberal transfusion strategy. CI denotes confidence interval; MI, myocardial infarction; and RR, relative risk.

Figure 4.

Subgroup Analysis for Primary Outcome of Death or Myocardial Infarction at 30 Days. Risk difference models using random effects did not converge for the subgroup age and subgroup random assignment hemoglobin. For each of these, we report risk difference estimates that do not use random effects. CI denotes confidence interval; MI, myocardial infarction; NSTEMI, non-ST-segment elevation myocardial infarction; STEMI, ST-segment elevation myocardial infarction; RBC, red blood cell; and RR, relative risk. Arrow indicates upper limit of confidence interval extends beyond 2.0.