Researchers Suggest Black Box Warning Not Appropriate for Ultrasound Contrast: Presented at ACC

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Title: Researchers Suggest Black Box Warning Not Appropriate for Ultrasound Contrast: Presented at ACC
URL: http://www.pslgroup.com/dg/21F12A.htm
Doctor's Guide
April 3, 2008

By Ed Susman

CHICAGO -- April 3, 2008 -- A large retrospective analysis of patients who received commercially available contrast agents did not see any more serious adverse events than those seen among patients who did not receive contrast during cardiac ultrasound scans.

"We believe our data should persuade the [United States] Food and Drug Administration [FDA] to reconsider their Black Box warning on the use of commercially available ultrasound contrast agents," said Melda S. Dolan, MD, Associate Research Professor of Cardiology, Saint Louis University, St. Louis, Missouri.

The FDA requested the warning on the contrast agents as a result of reports of 11 deaths since 1997, including 4 deaths that occurred within 30 minutes of use of the contrast agents.

Dr. Dolan reported on the data in an oral late-breaker report on March 31 here at the American College of Cardiology (ACC) 57th Annual Scientific Session.

"We still use these agents at our hospitals," she said. "However, we are very careful about following these patients carefully after the contrast study is completed. There are many hospitals where the extra staff is not available to monitor these patients, and at those facilities the use of the contrast agents is falling off."

About 20% to 30% of cardiac patients require echocardiography because they are unable to undergo a proper stress testing due to various problems, such as body habitus, chest wall deformities, lung disease, or heavy smoking, Dr. Dolan said. Since their approval, about 2 million doses of the commercially approved ultrasound contrast agents -- perflutren protein type A microspheres injectable suspension and perflutren lipid microspheres -- have been administrated, she added.

Dr. Dolan said the FDA warning suggests curtailment of the use of contrast agents in patients presenting with acute coronary syndromes, respiratory failure, arrhythmias, and pulmonary diseases. "These are the patients who need these studies the most," she said.

In the retrospective analysis, Dr. Dolan and colleagues at Saint Louis University and the University of Nebraska compared outcomes among patients who underwent resting echocardiography and compared adverse effects for the 24,000 who received contrast agents and the 6,000 matched patients who did not receive contrast agents. The researchers looked for cases of death or nonfatal myocardial infarction attack after 30 minutes and after 24 hours, she explained.

There was 1 death and 3 nonfatal heart attacks among the population who received contrast agents. The death occurred in a patient with renal failure who had been hospitalised before doctors requested an echocardiography to determine if the patient's deterioration was being caused by emboli. The patient succumbed 22 hours later on hospital day 12, Dr. Dolan said.

Among patients who did not require contrast, there was 1 death and 7 nonfatal myocardial infarcts. "The difference between these groups was not clinically meaningful," she said. "We felt we were right on the money in having predicted that there was no significant difference in outcomes over whether contrast agents were used or not."

In another part of the study, the researchers assessed the clinical value of contrast agents in diagnosis of cardiac diseases. Scanning images taken with contrast agents and without them were compared with images derived from angiography to determine presence of reperfusion.

Sensitivity compared with angiography was 81% with contrast and 73% without contrast. Dr. Dolan said the difference between contrast and noncontrast images was not statistically significant.

What was significant was the ability of the ultrasound scans to predict outcomes. Patients who showed normal wall motion and normal reperfusion had a 95% event-free survival at 3 years. If wall motion was normal and reperfusion was abnormal, survival was 85% without events. If there was abnormal wall motion and abnormal reperfusion, survival dipped to 69% (all P < .05).

[Presentation title: Safety and Efficacy of Commercially Available Ultrasound Contrast Agents in a Clinical Setting. Abstract 409-5]

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