U.S. health officials said on Friday they requested a strong "black box" warning on Bristol-Myers Squibb Co's Definity and General Electric Co's Optison about reports of serious cardiopulmonary reactions after people were injected with the imaging agents.

Ten deaths have been reported with Definity and one with Optison, the U.S. Food and Drug Administration said. Four of the 11 reported deaths were caused by cardiac arrest during infusion or within 30 minutes.

The agency said it also has received 190 reports of serious reactions following administration of Definity and nine after injection of Optison.

The products are given to some patients undergoing an echocardiogram to help doctors get a better view of the heart.

Some patients were also being treated with other medications that could have contributed to their deaths, the FDA said.

The agency said the manufacturers had agreed to add the new warning, which says not to use the products in patients with heart problems that could put them at risk for serious reactions. It also advises monitoring patients for 30 minutes.

Definity had 2006 sales of about $65 million. Optison was recalled by GE Healthcare in November 2005 because of manufacturing problems. The company said last month it hoped to relaunch the product this year.

Bristol-Myers spokesman Tony Plohoros said the new label should help ensure patient safety and that the company would be contacting its field staff and doctors about the changes.

"We believe that Definity still has significant medical value when used properly and in accordance with the label," he said.

A spokesman for GE Healthcare could not be reached for comment.

The products are made from gases enclosed in tiny capsules of protein or fatty material. They can help doctors visualize the borders of the heart more clearly and identify abnormalities.

(Reporting by Lisa Richwine and Kim Dixon)