"But they may not know that some of these substances could pose a hazard when taken with certain heart medications, and if they don't tell their doctors, the risk may go undetected,'' said Kline-Rogers, who presented the results before the American College of Cardiology meeting in Atlanta.
The study involved 145 patients who had been hospitalized for heart attack or angina within the past six months before being surveyed by phone last year. The questionnaire was designed by cardiologists, nurses and researchers at the university's Complementary and Alternative Medicine Research Center.
Seventy-four percent of the patients used complementary-alternative therapy, with 60 percent using supplements, vitamins, or herbs and 43 percent using mind-body practices like yoga or body-manipulation techniques like massage. Many used both supplements and various mind-body techniques.
Most said they used the alternative therapies to help them heal or ease their symptoms.
But particularly troubling was that 31.8 percent of the patients were taking at least one blood-thinning prescription medication and one dietary supplement that could also reduce clotting.
Most heart patients have a prescription to take aspirin or other blood thinners to prevent clotting and reduce the risk of heart attack or stroke. But supplements such as ginkgo biloba, ginseng, garlic, vitamin E, fish oil or coenzyme Q10 also have anticoagulant effects, but don't have doses that have been carefully controlled or studied.
In addition to the threat of uncontrolled bleeding from doubling up on blood thinners, health professionals worry that there may be other interactions between supplements and drugs.
Fortunately, 75 percent of those taking supplements, vitamins or herbs told their doctors what they were taking. The rest either didn't think it was necessary, didn't want to discuss it, or said their doctors didn't ask.
"We need to encourage patients to be cautious, learn the risks, and share information with their health providers,'' Kline-Rogers said, adding that clinicians also need to be more curious about what alternative medicines their patients are using.
The researchers noted that other complementary or alternative medicine approaches ranging from prayer, meditation, and yoga to chiropractic and acupuncture don't pose any specific hazard when combined with conventional heart treatments.
Kline-Rogers and her colleagues are now working on a larger study of heart patients. This study would repeat the original questions, but also ask about the intake of beverages, such as green tea and red wine, that can also affect clotting, and inquire if they have experienced minor bleeding symptoms.