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FDA warns drugs given with cardiac stress tests may lead to heart attacks

The chemical agents used for cardiac stress tests that look for signs of heart disease may in fact trigger heart attacks in patients, the Food and Drug Administration warned Wednesday.

The side effect is rare but serious, and related to two specific injectable drugs: Lexiscan and Adenoscan, which are both manufactured by Astellas Pharma US.

A typical cardiac nuclear stress test measures blood flow to the heart muscle at rest and also during stress, which is usually recreated through having patients exercise while hooked up to electrodes connected to an electrocardiogram (EKG). The EKG measures the electrical signals behind heartbeats, and a radioactive dye is injected into the bloodstream once maximum exercise levels are reached, which are then looked at under an X-ray to check for blockages or problems with blood flow.

However, some people can’t exercise adequately for the test to work, and in that case, they are given an injectable drug that increases blood flow to the heart muscle to stimulate exercise, the Mayo Clinic notes.

Lexiscan and Adeonscan are two such drugs, and now the FDA is warning doctors to avoid using them in patients with signs or symptoms of unstable angina or heart problems because they might be at risk for a serious reaction.

When injected, the drugs cause blood to flow to the healthier, unblocked arteries. But when they do that, it reduces blood flow to the blocked artery, which can lead to a fatal heart attack, according to the FDA.

The agency says trained medical staff with resuscitation equipment like a defibrillator should be on hand before administrating either of these drugs.  The drugs’ labels will be changed to reflect these warnings.

“We recommend that health care professionals and their patients discuss any questions or concerns,” the FDA said in its safety announcement.

Astellas told Reuters it has been working with the FDA to ensure healthcare practitioners are aware of the latest safety information.

"Changes to product labels are not uncommon," the company said in a statement to Reuters. "Lexiscan and Adenoscan have been determined by the FDA to be safe and effective when use is consistent with the approved indications."

Dr. Suzanne Steinbaum, director of women and heart disease at Lenox Hill Hospital in New York City, told CBSNews.com that this new warning won’t change how she practices medicine, because patients who can’t even get on a treadmill and exercise for reasons other than injury are likely already at high risk for heart disease.

Instead, “they should be in the cath lab if their heart needs to be looked at.”

A cardiac catheterization lab at a hospital can check blood flow in arteries and the chambers of the heart, through angiography procedures, where a dye is injected into the artery and X-rayed to look for blockages.

Cardiac stress tests should only be given to people who are at intermediate risk for heart disease, Steinbaum added.

“Every warning like this makes doctors pause,” she said. “I think it's just bringing attention to the fact that if these medications have to be used, we really need to be sure we’re choosing the right patients to get it.”

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