in the landmark REALITY trial.
Randomized trial data already support a restrictive transfusion strategy in patients undergoing cardiac and noncardiac surgery, as well as in other settings. Those trials deliberately excluded patients with acute myocardial ischemia.
Cardiologists have been loath to adopt a restrictive strategy in the absence of persuasive supporting evidence because of a theoretic concern that low hemoglobin might be particularly harmful to ischemic myocardium. Anemia occurs in 5%-10% patients with MI, and clinicians have been eager for evidence-based guidance on how to best manage it.
“Blood is a precious resource and transfusion is costly, logistically cumbersome, and has side effects,” Philippe Gabriel Steg, MD, chair of the REALITY trial, noted in presenting the study results at the virtual annual congress of the European Society of Cardiology.
REALITY was the first-ever large randomized trial of a restrictive versus liberal transfusion strategy in acute MI. The study, which featured a noninferiority design, included 668 stable patients with acute MI and anemia with a hemoglobin of 7-10 g/dL at 35 hospitals in France and Spain. Participants were randomized to a restrictive strategy in which transfusion was withheld unless the hemoglobin dropped to 8 g/dL or less, or to a conventional liberal strategy triggered by a hemoglobin of 10 g/dL or lower. The transfusion target was a hemoglobin level of 8-10 g/dL in the restrictive strategy group and greater than 11 g/dL in the liberal transfusion group. In the restrictive transfusion group, 36% received at least one RBC transfusion, as did 87% in the liberal transfusion study arm. The restrictive strategy group used 414 fewer units of blood.
The two coprimary endpoints were 30-day major adverse cardiovascular events and cost-effectiveness. The 30-day composite of all-cause mortality, reinfarction, stroke, and emergency percutaneous coronary intervention for myocardial ischemia occurred in 11% of the restrictive transfusion group and 14% of the liberal transfusion group. The resultant 21% relative risk reduction established that the restrictive strategy was noninferior. Of note, all of the individual components of the composite endpoint numerically favored the restrictive approach.
In terms of safety, patients in the restrictive transfusion group were significantly less likely to develop an infection, by a margin of 0% versus 1.5%. The rate of acute lung injury was also significantly lower in the restrictive group: 0.3%, compared with 2.2%. The median hospital length of stay was identical at 7 days in both groups.
The cost-effectiveness analysis concluded that the restrictive transfusion strategy had an 84% probability of being both less expensive and more effective.
Patients were enrolled in REALITY regardless of whether they had active bleeding, as long as the bleeding wasn’t deemed massive and life-threatening. Notably, there was no difference in the results of restrictive versus liberal transfusion regardless of whether active bleeding was present, nor did baseline hemoglobin or the presence or absence of preexisting anemia affect the results.
Dr. Steg noted that a much larger randomized trial of restrictive versus liberal transfusion in the setting of acute MI with anemia is underway in the United States and Canada. The 3,000-patient MINT trial, sponsored by the National Institutes of Health, is testing the superiority of restrictive transfusion, rather than its noninferiority, as in REALITY. Results are a couple of years away.
“I think that will be an important piece of additional evidence,” he said.
Discussant Marco Roffi, MD, didn’t mince words.
“I really love the REALITY trial,” declared Dr. Roffi, professor and vice chairman of the cardiology department and director of the interventional cardiology unit at University Hospital of Geneva.
He ticked off a series of reasons: The trial addressed a common clinical dilemma about which there has been essentially no prior high-quality evidence, it provided convincing results, and it carried important implications for responsible stewardship of the blood supply.
“REALITY allows clinicians to comfortably refrain from transfusing anemic patients presenting with myocardial infarction, and this should lead to a reduction in the consumption of blood products,” Dr. Roffi said.
He applauded the investigators for their success in obtaining public funding for a study lacking a commercial hook. And as a clinical investigator, he was particularly impressed by one of the technical details about the REALITY trial: “I was amazed by the fact that the observed event rates virtually corresponded to the estimated ones used for the power calculations. This is rarely the case in such a trial.”
Dr. Roffi said the REALITY findings should have an immediate impact on clinical practice, as well as on the brand new 2020 ESC guidelines on the management of non–ST-elevation ACS issued during the ESC virtual congress.
The freshly inked guidelines state: “Based on inconsistent study results and the lack of adequately powered randomized, controlled trials, a restrictive policy of transfusion in anemic patients with MI may be considered.” As of today, Dr. Roffi argued, the phrase “may be considered” ought to be replaced by the stronger phrase “should be considered.”
During the discussion period, he was asked if it’s appropriate to extrapolate the REALITY results to patients undergoing transcatheter aortic valve replacement, among whom anemia is highly prevalent.
“I think this is a different patient population. Nevertheless, the concept of being restrictive is one that in my opinion now remains until proven otherwise. So we are being very restrictive in these patients,” he replied.
Asked about possible mechanisms by which liberal transfusion might have detrimental effects in acute MI patients, Dr. Steg cited several, including evidence that transfusion may not improve oxygen delivery to as great an extent as traditionally thought. There is also the risk of volume overload, increased blood viscosity, and enhanced platelet aggregation and activation, which could promote myocardial ischemia.
The REALITY trial was funded by the French Ministry of Health and the Spanish Ministry of Economy and Competitiveness with no commercial support. Outside the scope of the trial, Dr. Steg reported receiving research grants from Bayer, Merck, Servier, and Sanofi as well as serving as a consultant to numerous pharmaceutical companies.