Although clinicians have long been uncertain about the benefits of blood transfusions in patients with heart attacks, a study by Yale investigators has found that they significantly improve chances for survival.

“Our principal finding is that a low hematocrit on admission is associated with higher mortality rates in elderly heart attack patients,” said principal investigator Harlan M. Krumholz, M.D., associate professor of medicine (cardiology) and epidemiology. “However, blood transfusions, when given to these patients, can significantly decrease their mortality risk. This is the first study to highlight the important link between anemia, blood transfusion and mortality among elderly patients hospitalized for a heart attack.”

Krumholz and researchers at Brown University Medical School, Yale’s Department of Epidemiology and Public Health and the Yale-New Haven Hospital Center for Outcomes Research and Evaluation conducted a retrospective study of 78,964 Medicare beneficiaries 65 years and older who were hospitalized with acute myocardial infarction. After categorizing patients on the basis of their hematocrit levels, the researchers then explored links between transfusions and 30-day mortality. “Surprisingly, we found that 43.4 percent of elderly patients hospitalized with a heart attack are anemic, or have a blood count below 39 percent, at the time of admission,” said co-author Saif S. Rathore, M.P.H., a lecturer in the Department of Internal Medicine.

The study also found that the most severely anemic patients were twice as likely to die within 30 days as those who were not anemic. Despite the higher mortality risk, fewer than a quarter of the patients with clinically significant anemia received a blood transfusion.

“Our data indicate that blood transfusions provided to elderly anemic patients can significantly reduce their risk of short-term mortality,” said Krumholz. “Most promisingly, our data indicate that this benefit is observed in elderly patients with blood count levels as high as 33 percent, a higher level than previously considered by clinicians. These data are particularly compelling given the lack of clinical guidelines concerning hematocrit levels at which to transfuse elderly patients with heart disease.”

The study was published in the October 25 issue of The New England Journal of Medicine. In an editorial accompanying the study, Lawrence T. Goodnough, M.D., and Richard G. Bach, M.D., of the Washington University School of Medicine, underscored the importance of these findings. “For the first time, we have evidence that patients with a specific clinical presentation are affected adversely by the underuse of transfusion,” Goodnough and Bach wrote. Based on this research, they suggested “that hematocrit levels should be maintained above 33 percent in patients who present with acute myocardial infarction.”

“We certainly feel that our findings should result in a change in clinical practice,” said first author Wen-Chih Wu, M.D., a teaching fellow in internal medicine (cardiology) at Brown University.