The researchers on Monday said their study, published in the journal Circulation, should reassure surgeons who have advised patients to avoid taking aspirin in the days before surgery because they feared it could cause bleeding.
"Aspirin reduces clotting of the blood, so it can help prevent a heart attack or stroke by making it less likely a clot will form and block an already narrowed artery," said Dr Scott Wright, a cardiologist at the Mayo Clinic in Rochester, Minnesota, who led the study.
"However, many surgeons who are concerned about excessive bleeding due to inadequate clotting have advised their patients to stop taking aspirin in the days before their operation. We designed this study to provide guidance on whether continuing aspirin therapy in the days before surgery is beneficial or risky."
The researchers studied 1636 patients getting heart bypass surgery in 2000, 2001 and 2002.
They found that 1.7% of those patients who took aspirin in the five days before surgery died in the hospital afterwards, compared to 4.4% of those who did not.
Those who took aspirin did not have a greater risk of excessive internal bleeding, Wright's team found.
"The study further confirms aspirin's benefits for patients with known cardiovascular disease. It also shows there is no increased risk of bleeding, which eliminates the main reason why physicians and surgeons would ask patients to discontinue aspirin therapy," Wright said.