By Richard Lenti

Heart attack patients who receive a blood transfusion have a greater risk of dying or suffering a second heart attack according to a new study published in the Archives of Internal Medicine.

Researchers found the risk of death was 12 percent higher for people who received transfusions during a heart attack compared to those who did not. They also were twice as likely to have another heart attack.

Doctors often order blood transfusions for heart attack patients with anemia to help deliver oxygen to the heart. But researchers say there’s been insufficient study on the benefits and risks of the practice, leaving doctors with little guidance on whether or not to order the transfusions.

A team led by Saurav Chatterjee, MD, of Brown University, evaluated ten studies carried out between 1966 and 2012 involving more than 200,000 heart attack patients. One study was a randomized trial; the others were observational studies.

“One of the things that struck us is that there were very few studies in evidence of transfusion at all,” Chatterjee said. “In our case, though, we found that the effect was pretty consistently harmful across the spectrum of studies, spectrum of time, and spectrum of patients that were enrolled in the individual studies. “

While some transfusions are necessary, like when a patient’s suffers both a heart attack and bleeding, Chatterjee said they also increase the risk of blood clotting when platelets clump together or an inflammatory immune response to the introduction of a “foreign” source into the body.

“What we found is that the possibility of real harm exists with transfusion,” Chatterjee said. “It is practiced in emergency departments all across the United States. I think it is high time that we need to answer the question definitively with a randomized trial.”

But Chatterjee also cautions that transfusions should not be stopped altogether for anemic heart attack patients. He says doctors must continue exercising their clinical judgment, at least until results from a large, well-designed randomized trial can be produced.

“Before a definitive trial is out there, we should be conservative, especially considering the high risk of harm,” he said.

In a commentary also appearing Archives of Internal Medicine, Dr.Jeffrey Carson of the University of Medicine and Dentistry of New Jersey and Dr. Paul Hébert of the Ottawa Hospital Research Institute, question the study’s conclusion.

“Do blood transfusions kill more patients with an acute myocardial infarction (heart attack) than anemia? Chatterjee and colleagues would have you believe that they do. We remain unconvinced,” they wrote.

Carson and Hébert say that because of the study’s many limitations, doctors should not use its findings to justify or limit the use of red blood cells. But, like Chatterjee, they also called for more studies to be done.

“We can now appreciate how little reliable information is available to inform clinical and policy decisions involving red blood cell transfusions in patients with acute coronary syndrome,” they said.

“Given that real risks and potential benefits exist as to how we choose to use the valuable resource of blood transfusion, we believe that high-quality research is long overdue.”