Monday June 2 6:47 PM EDT

-- Antioxidant vitamins -- especially vitamin E -- may help improve the results of coronary bypass surgery and treatment with clot-dissolving drugs during a heart attack, a study suggests.

Findings from a new test that measures free-radical activity when blood flow is restored to the heart point to "oxidant stress" as a likely cause of subsequent heart trouble in some patients.

Free radicals are volatile molecules that develop during exposure to oxygen, such as would be encountered during "reperfusion," when the flow of oxygen-rich blood again reaches the heart when an arterial blockage is cleared or after heart surgery. Experiments have associated a build-up of free radicals with tissue injury.

According to scientists at the University of Pennsylvania Medical Center in Philadelphia, such an increase occurring during cardiac reperfusion could explain serious heart trouble or heart failure that often occurs during this period of renewed blood supply.

In a report in the June 3 issue of the journal Circulation, the researchers describe a new test that measures urine levels of the biochemical called 8-epi PGF2-alpha -- a compound that results from a free radical attack on fatty acids in cell membranes.

Among those tested in a series of studies were heart patients at Mater Hospital in Dublin, Ireland, and at the Hospital of the University of Pennsylvania. These included heart attack victims treated with the clot-buster streptokinase and patients undergoing bypass surgery. Others were people with stable angina (chest pains).

In the heart attack patients, urinary levels of 8-epi PGF2-alpha jumped immediately following streptokinase therapy to more than 2 1/2 times those of angina patients and healthy volunteers.

In the bypass patients, levels of the chemical were measured prior to, during, and after the operation. When blood flow was at its maximum, levels were almost triple what they were before the operation. These returned to normal 24 hours after the operation.

The researchers note the findings may lead to the development of antioxidant treatments -- drugs or vitamins -- for heart patients that might prevent possible tissue damage from free radicals.

"Using this approach, we can rationally evaluate precise doses of antioxidant vitamins or drugs with the aim of suppressing the free-radical mechanism during reperfusion, and then seeing whether there are benefits for patients," says senior study author Dr. Garret A. FitzGerald. "Once we've defined the appropriate doses, we will be able to assess whether giving these compounds before surgery leads to improved outcomes."