Delayed angioplasty with stenting after myocardial infarction restores blood flow but does not improve ventricular function compared with medical therapy alone, according to a late-breaking clinical trial presented at the American Heart Association meeting.

The Total Occlusion Study of CAnada (TOSCA)-2 was a sub-study involving 381 Canadian and international patients enrolled in the Occluded Artery Trial (OAT), the largest randomized, controlled trial on late reperfusion.

The OAT study chair reported that their trial reached a similar surprising conclusion: Late reperfusion (3 to 28 days after acute myocardial infarction) failed to reduce cardiovascular complications during three years of follow-up.

TOSCA-2 resulted in a few surprises, said Vladimir D?avik, MD, TOSCA-2 study chair and director of the cardiac catheterization laboratory and interventional cardiology at the University Health Network in Toronto, Canada.

“Interestingly, there appeared to be less heart enlargement, or dilation, in the percutaneous coronary intervention group,” said Dzavik. “Dilation of the heart’s chambers after a heart attack is bad. Still, OAT showed no benefit at an average of three years of follow up. Yet, we’ve shown here that the amount of blood these (treated) hearts pump with each beat is more normal.”

TOSCA-2, which began as an independent study and joined OAT in the late 1990s, compared how patients’ hearts responded mechanically after either late reperfusion or treatment with medication alone. Before OAT, no large studies examined whether late reperfusion would benefit patients.

“The beauty of OAT is that it’s a large study and can actually answer the clinical endpoint question,” Dzavik said. “But a large study often can’t look at the mechanism of why something happened. It’s too expensive to do angiograms at follow up on more than 2,000 patients to see if the arteries remained open and to do studies on heart function. That’s the beauty of TOSCA-2.”

The primary endpoints in this study were whether the reopened infarct-related arteries (IRA) would stay open for one year and whether the ejection fraction would improve in angioplasty patients compared with patients who were managed with medication alone.

In the intervention group, 93 percent of infarct-related arteries were reopened via late reperfusion and 83 percent of those remained open for one year compared with 25 percent in the medication cohort. However, the ejection fraction was similar for both groups after one year.

“Clinically there’s no benefit to mortality, recurrent heart attack or heart failure (the OAT endpoints) at the end of three years, so we are all wondering if it might take longer for percutaneous coronary intervention to show a benefit,” he said, explaining that the researchers hope to keep following this group of patients.

The OAT trial found a non-significant but disturbing trend toward a higher rate of recurrent infarctions with angioplasty. “But they are very small infarcts and haven’t translated to any problematic outcome clinically,” D?avik said. “Could it be that if you leave an artery closed and it stays closed, there is no heart attack, but if you reopen it, the artery has a chance to close again and cause a second heart attack?”