Last October the FDA placed a black box warning on ultrasound contrast agents used to improve the quality of echocardiograms. The warning was issued after reports of four deaths and serious reactions occurring shortly after or during the infusion.

A black box warning is given to drugs that carry significant risk of serious or even life-threatening adverse effects. The warning placed on ultrasound contrast agents was issued without a formal examination of the risks and benefits of using them, said Dr. Melda Dolan, an associate professor of cardiology at the St. Louis University School of Medicine.

Dolan's research shows the contrast agents are safe and withholding their use -- which has occurred since the FDA issued the warning -- would make diagnosis of life-threatening heart disease more difficult.

"Based on the results of our study, we believe the FDA should reconsider its stance on contrast agents because the benefits outweigh the potential, although not established, risk," said Dolan.

Dolan presented the research findings last week in Chicago during the 57th annual American College of Cardiology Scientific Session.