TUESDAY, Aug. 17 (HealthDay News) -- Deaths from a severe type of heart attack rise by about 10 percent for every hour of delay between the time the patient calls for an ambulance and the time that patient is treated in the hospital, a new European study finds.

Researchers in Denmark analyzed data from Danish medical registries on 6,209 patients taken by ambulance to three major hospitals for an ST-segment elevation myocardial infarction (STEMI), a particularly serious type of heart attack caused by a blocked artery, between January 2002 and December 2008.

In patients with such heart attacks, the longer the artery is blocked, the more heart muscle that is damaged and the greater the chances of death, explained study author Dr. Christian Juhl Terkelsen, a cardiologist at Aarhus University Hospital in Denmark.

During a median follow-up period of 3.5 years, about 15.4 percent of patients died in the group that waited less than an hour from the time they called for an ambulance to the time they were being treated at the hospital, compared to 23.3 percent of those treated in up to two hours; 28.1 percent of those treated within just over two to three hours; and 30.8 percent of those treated within three to four hours.

Previous research has focused on delays in such care (called door-to-balloon delay, since the preferred treatment is known informally as balloon angioplasty), the researchers noted. But this study is the first to document that delays from the moment the patient calls for an ambulance increases the risk of death, Terkelsen said.

"Our message is we should focus on all health-care system delays, which often starts with the call for the ambulance," Terkelsen said.

The study is published in the Aug. 18 issue of the Journal of the American Medical Association.

The three hospitals included in the study were high-volume centers that offer primary percutaneous coronary intervention (PCI), also known as balloon angioplasty, in which a catheter is threaded into the artery and a balloon at the end is inflated to help widen it. Usually, when the tube is removed, a stent, or wire mesh structure, is left behind to prevent the artery from narrowing again.

All the patients were treated within 12 hours by PCI, and 2 percent of them were pretreated with clot-busting drugs to restore blood flow.

In Denmark, PCI became the recommended treatment for STEMI heart attacks in 2003, according to the study. Research shows that PCI is more effective than older treatments, such as clot-dissolving medications, Terkelsen said.

But in the United States, not every hospital is equipped to do PCI, said Dr. Christopher Granger, director of the cardiac care unit at Duke University Medical Center.

Even hospitals that do offer PCI don't necessarily have the medical staff on hand 24-7 to get it done quickly, Granger said.

That makes it critical to get to the right sort of hospital -- one that has a "catheterization lab" in which staff can be activated quickly when a STEMI patient is on route, Granger said.

A key step in activating the "cath lab" is making sure that paramedics can diagnosis the heart attack en route, Granger said. To do this, ambulances need to be equipped with 12-lead electrocardiogram (ECG) machines, which can diagnosis the telltale signs of STEMI.

While all ambulances in Denmark have 12-lead electrocardiogram, the same can't be said of all U.S. ambulances, Granger said.

Even when STEMI is diagnosed by first responders, it is not ideal to rush a patient to a hospital that doesn't offer PCI.

"The time from the 911 call until the artery is opened is a very powerful, independent predictor of long-term survival," Granger said. "The faster you get to a hospital that has the ability to PCI, the better your chances of living."

About 400,000 people in the United States have a STEMI heart attack annually, according to the American Heart Association, which is working with hospitals and emergency medical services to develop more coordinated, regional systems of care for heart attacks. Called Mission:Lifeline, the program calls for a new approach to improve outcomes, including training first responders to use 12-lead electrocardiograms and protocols that instruct responders to consider bypassing hospitals that don't offer PCI for those able to perform PCI quickly, even if the hospital is further away.

"What's clear is you should do pre-hospital diagnosis. You should reroute patients to hospitals that can provide PCI quickly, within 30 minutes," Juhl said. "And when patients arrive, they should not go to emergency room, the intensive care unit or the coronary care area. They should go directly to the cath lab."

Patients also need to be aware they should call 911 if they are experiencing the signs of a heart attack, which can include squeezing chest pain, shortness of breath and fatigue, Granger said.

More information

The American Heart Association has more on heart attacks.