SILVER SPRING, Md. -- Two agents used in cardiac nuclear stress tests may carry a greater risk of heart attack and death than previously believed, the .
Analysis of the agency's uncovered reports of 32 cases of myocardial infarction and 56 deaths following use of and in cardiac stress tests. Besides MI, the event reports also listed cardiac and cardiorespiratory arrests, ventricular arrhythmias, and respiratory abnormalities.
"When reported, these adverse events tended to occur within 6 hours following Lexican or Adenoscan administration. A few deaths occurred when Lexiscan or Adenoscan was administered with exercise stress testing, which is not an FDA approved use of the drugs," the agency said.
Most of the events occurred with regadenoson, but the FDA said the data were too limited to detect a meaningful difference between the two agents' risk levels.
Labels on these drugs previously mentioned an increased risk of MI and death; this information will now be expanded with new recommendations for usage.
Specifically, regadenoson and adenosine should be avoided in patients with signs or symptoms of unstable angina or cardiovascular instability, the FDA said. Patients should be screened for these conditions and other contraindications, and cardiac resuscitation equipment and trained staff should be on hand before administering these agents.
The FDA noted that alternative agents for use in cardiac stress tests include (approved for this purpose) and (not approved but available off-label).
Regadenoson and adenosine are similarly acting arterial vasodilators, which aid in identifying coronary arteries with obstructed flow. They cause blood to flow preferentially through relatively unoccluded vessels, and consequently less through obstructed vessels. In vulnerable patients, this may lead to MI, the FDA said.