Response time for half the heart attack patients in US hospitals is too slow, according to doctors.

"This doesn't mean we're missing people once in a while, says senior author Harlan Krumholz of Yale University. "It means that the majority of people are not being treated within the time recommended for good care."

The worst time to have a heart attack is after business hours or on weekends, the study shows, especially for patients who need emergency angioplasty. In that procedure, doctors guide a balloon-tipped wire to the site of the blockage and open the balloon to clear out the artery.

"There's a difference between off hours and regular hours no matter which type of hospital you're talking about," says Lawton Cooper of the National Heart, Lung, and Blood Institute, the study's sponsor.

Reopening Clogged Arteries

Researchers based their analysis on information from 100,000 heart attacks logged into the National Registry of Myocardial Infarction from 1999 to 2004. All of the patients in the study had blockages in arteries that supply the heart, not rhythm disturbances that can cause cardiac arrest. Doctors attempted to reopen their clogged arteries with either clot-busting drugs or by emergency angioplasty.

Studies have shown that angioplasty is more effective than using clot-dissolving drugs. But clot busters are used more often, because angioplasty must be done in a high-tech catheter lab by trained personnel. About 20% of hospitals can handle emergency angioplasty, experts say.

A total of 68,439 of the patients in the study were given clot-busters. Just 45% of those who arrived at the hospital during business hours were treated within the half-hour set by American Heart Association (AHA) guidelines. Only 40% of those who arrived after hours were treated within 30 minutes, says the study in the August 17 issue of the Journal of the American Medical Association.

Lag Time Greatest for Angioplasty Patients

Balloon angioplasty was used in 33,647 patients. Just under 50% of those whose heart attacks occurred during business hours were treated within the 90 minutes recommended by AHA. After hours, only 25% were treated that quickly.

After-hours delays were much shorter for patients who were treated with drugs than for those treated with angioplasty. Clot-busters were given within 33 minutes of getting to the hospital during regular hours and within 44 minutes after hours.

The "door to balloon" times for angioplasty patients rose from 95 minutes during business hours to 116 minutes after hours.

"The 90-minute guideline is very difficult to achieve, and not because we're sitting around smoking and sipping mint juleps, says Christopher White, director of cardiology at New Orleans' Ochsner Clinic. "We try hard. We fly down and get these guys out of the ER. We're 92, 93 minutes on average.

Timely Care Too Costly?

"But the cath lab isn't waiting for you to have a heart attack. We have to react."

Keeping a catheter lab waiting for patients costs more than many hospitals can afford, White adds.

"New Orleans is a good example. We have 11 hospitals. If one hospital did every heart attack, it could be set up 24-7. But we do maybe five heart attacks a week. For five heart attacks a week, I can't staff my cath lab full time."