Newswise — Results of an expanded, bold clinical trial that treats heart attack patients with a reduced-dose, clot buster in the back of an ambulance en route to a hospital has led to a new discovery by researchers at The University of Texas Health Science Center at Houston (UTHealth): giving the drug can lessen the time the heart suffers damage to under two hours, significantly improving outcome.

“We’ve known for a while that after the first three hours of a heart attack, much of the damage is already done. But more recent data is making it clearer that it’s really the first two-hour period that is most critical ,” said James J. McCarthy, M.D., assistant professor of emergency medicine at the UTHealth Medical School and director of the Emergency Center at Memorial Hermann-Texas Medical Center. “In this study, we compared how many patients we could treat in the first two hours compared to conventional strategies. What we found is that very few patients could be treated in the first two hours without initiating treatment before they arrived in the hospital, and by doing so we could decrease the amount of heart damage that occurs.”

McCarthy presented the latest results of the study, “A Coordinated Pre-Hospital Initiated Thrombolytic Strategy Coupled with Urgent PCI Dramatically Reduces Time to Treatment for STEMI Patients,” on Nov. 13, 2010 during the 2010 American Heart Association’s (AHA) Scientific Sessions Conference in Chicago. This research, a collaboration of UTHealth, Memorial Hermann Heart & Vascular Institute-Texas Medical Center and the Houston Fire Department, builds on a previous smaller study.

“If they wait an hour to call 911—the national average is two hours—and it takes another hour for them to get to the hospital, they are already outside that two-hour mark,” McCarthy said. “Even at top performing hospitals, it can take 50 minutes to get treated. The AHA standard is 90 minutes. We are discovering more and more that time is heart.”

During a heart attack, an artery to the heart is blocked. The heart muscle does not die immediately, but the likelihood of debilitating damage—and death—goes up the longer the artery stays blocked. Physicians including cardiology pioneers at UTHealth discovered 30 years ago that the artery could be opened quickly by delivering a clot-buster (a thrombolytic medicine) into the affected artery via a catheter.

The UTHealth study, called Pre-Hospital Administration of Thrombolytic Therapy with Urgent Culprit Artery Revascularization (PATCAR), takes treatment a step further by giving the patient a lower dose of a clot-busting drug intravenously (IV) before they arrive at the hospital. Early results published in 2008 ( showed that in 82 percent of patients who received the IV drug in the ambulance, the artery was already partially re-opened. In addition, the size of the heart attack was reduced by 50 percent and there was a 50 percent reduction on mortality. That study included 73 patients.

The most recent results included a total of 314 patients. Of those, 278 were treated with pre-hospital, clot-busting medication. The remaining 36 were ineligible for the medication and became the control group. The time to treatment initiation within two hours was 74 percent of the pre-hospital medication group versus just 17 percent of the non-pre-hospital medication group.

“Results from this larger group of patients also relieved worries about complications of giving the clot-buster, such as strokes and bleeding, which were not more likely to occur,” McCarthy said. “We are hopeful that further randomized testing will reveal that this could result in a new standard of care for heart attack patients.”

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2010 American Heart Association’s (AHA) Scientific Sessions Conference