A U.S. Food and Drug Administration spokeswoman said the agency is preparing a warning about the dangers of drugs used to enhance heart-related diagnoses.

   The FDA has been investigating reports of deaths and serious cardiopulmonary reactions in patients who took drugs designed to assist in diagnosing heart problems with ultrasound imaging machines, the Wall Street Journal reported Monday.

   The injected drugs, which include Definity, manufactured by Bristol-Myers Squibb Co. of New York, and Optison, from General Electric Co., Fairfield, Conn., contain microscopic gas-filled spheres that allow for sharper pictures to be taken of a patient's heart during an echocardiography procedure.

   The FDA spokeswoman said the agency will alert the healthcare industry about "these serious risks and... provide guidance regarding the safe use" of the drugs. 

   She said the drug makers have also agreed to update their labels to reflect the risks.

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