The U.S. Food and Drug Administration has placed regadenoson, the most widely used pharmcologic stress agent in the U.S., on its quarterly list of products to monitor, the agency announced. The agent has shown a potential link to myocardial infarction (MI) and death.

The drug, manufactured under the name Lexiscan, is used in myocardial perfusion imaging for patients who cannot exercise for a normal stress test. According to the Lexiscan website, about half of patients who undergo cardiac stress testing are unable to exercise adequately. The agent is used in seven out of 10 pharmacologic stress SPECT MPI procedures in the U.S.

The agency received reports suggesting a link between regadenoson and MI and death during the second quarter of 2013. Now the agency will investigate whether there is indeed a causal connection. If it does find a connection, the agency would likely collect more data, leading to a label revision or risk-evaluation.

Lexiscan's safety warnings already note the risk of MI, and that the drug can cause serious or fatal cardiac arrest, abnormal heart rhythms, and that it should not be given to patients who have certain abnormal heart rhythms.

The FDA notes that adding a drug to its watch list does not mean that it's dangerous or that it should stop being prescribed.