Some signal of benefit found for liberal transfusion strategy for anaemic heart attack patients

Adopting a liberal blood transfusion strategy in patients with acute myocardial infarction (AMI) and anaemia does not appear to do much in terms of reducing the risk of AMI recurrence or death compared with a restrictive transfusion strategy, although there appears to be a hint of benefit, as shown in the results of the phase III MINT trial.

Moreover, “potential harms of a restrictive transfusion strategy cannot be excluded,” according to investigators led by Dr Jeffrey Carson from Rutgers Robert Wood Johnson Medical School in New Brunswick, New Jersey, US.

In MINT, the primary outcome of a composite of myocardial infarction or death at 30 days did not significantly differ between a strategy that involved administering transfusions when haemoglobin levels fell below 7 or 8 g/dl (restrictive) and a strategy aimed at maintaining haemoglobin levels ≥10 g/dl (liberal; 16.9 percent vs 14.5 percent, respectively; risk ratio [RR], 1.15, 95 percent confidence interval [CI], 0.99–1.34; p=0.07). [Carson JL, et al, AHA 2023]

Death was slightly more common among patients in the restrictive strategy group than among those in the liberal strategy group (9.9 percent vs 8.3 percent; risk ratio, 1.19, 95 percent CI, 0.96–1.47), as was MI (8.5 percent vs 7.2 percent; risk ratio, 1.19, 95 percent CI, 0.94–1.49).

“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 in a statement.

“[A] liberal transfusion strategy may be the most prudent approach for patients with heart attack and anaemia,” Carson spoke of the findings.

Not quite a home run

During an AHA press conference, Dr Martin Leon of NewYork-Presbyterian/Columbia University Irving Medical Center in New York, New York, US, stated, “The definitive home-run statistical endpoint was not quite achieved, but so many of the things are more in favour of a more liberal transfusion strategy, that that will likely be the general interpretation [of the trial].”

For example, a drop from 5.5 percent to 3.2 percent in the rate of cardiovascular death is notable, Leon continued.

“The final conclusion is that this is not definitely superior to employ in all patients a liberal strategy, but I think it will be interpreted that the effect size is somewhat small but meaningful. The liberal strategy will probably be the dominant strategy in most patient cohorts, as the point estimates are very consistent,” he pointed out.

More work needed

MINT included 3,504 patients (average age 72 years, 55 percent men) recruited from 144 hospitals across the US, Canada, France, Brazil, New Zealand, and Australia. These patients had a heart attack and haemoglobin concentration levels <10 g/dL, which was below the normal threshold (12–13 g/dL). Many of these patients had other health conditions, including a history of heart attack (33 percent), heart failure (30 percent), diabetes (54 percent), and kidney disease (46 percent).

Of the patients, 1,749 comprised the restrictive transfusion group and 1,755 comprised the liberal transfusion group. The mean number of red-cell units that were transfused was 0.7 and 2.5 in the respective groups. On days 1 to 3 after randomization, the mean haemoglobin level was lower by 1.3–1.6 g/dL in the restrictive-strategy group than in the liberal-strategy group. 

“Low red blood count or anaemia is common among people hospitalized with heart attack,” Carson noted. “Future research is needed to further resolve the controversy around transfusion decisions for [this population].”