WESTON, Fla. -

After his sister underwent surgery for a pacemaker, Ken Wurtenberg worried about his own heart.

When an electrocardiogram and echocardiogram came back irregular, his doctor recommended a nuclear stress test.

"I was a little apprehensive at first because the word 'nuclear' kind of got to me and I had a great concern about side effects," said Wurtenberg. "I'm very much holistic and I don't take an prescriptions, any kinds of meds, those things, but when it's necessary, you gotta do things like that."

The Food and Drug Administration recently warned that two drugs used in nuclear stress tests -- Lexiscan (regadenoson) and Adenoscan (adenosine) -- may carry a greater risk of a heart attack and death than previously believed.

"We are not the FDA and we cannot get a response from the FDA of why they think that other than the FDA says pay attention to this -- we're concerned about safety, we'll pay attention to it and we'll do the education that we need to do to get this done," said Dr. David Wolinsky, a cardiologist at Cleveland Clinic Florida.

The FDA's adverse event database reports 32 cases of heart attacks and 56 deaths following the use of the two drugs.

Wolinsky said those cases are out of more 2.5 million stress tests performed.

"I do not think people should be afraid. I think the risk that's been reported is very, very low," he said.

Wolinsky said a nuclear stress test should only be ordered for patients suspected of having a moderate to high risk of heart disease and a low risk of complications.

"My feeling is always I don't order a test on a patient until I know what I'm going to do with the results," he said. "What am I going to do if it's positive, what am I going to do if it's negative and go over the relative risks and benefits."

Read more about appropriate uses of nuclear stress tests.