Quickly moving heart attack patients from one hospital to another that can provide optimal care for their condition can mean the difference between life and death – but nine out of 10 patients wait longer than recommended, according to a nationwide study published in the Archives of Internal Medicine.

People who have had a heart attack often need the artery that’s blocking blood supply to the heart cleared, and a stent placed to keep the artery open. But less than a quarter of U.S. hospitals are equipped to perform stenting 24 hours a day, so patients often need to be transferred to other facilities.

The national goal is to have a patient moved to a more sophisticated facility within 30 minutes after arrival at the first hospital. A heart patient’s risk of dying increases by 56 percent when transfer time exceeds 30 minutes, researchers noted.

“The longer the heart is deprived of blood flow, the more damage is done,” said Dr. Harlan Krumholz of Yale School of Medicine, who worked on the study.

Researchers analyzed 2009 data from some 14,000 patients at over a thousand hospitals throughout the U.S. Over half the patients waited more than hour before being transferred, and one-third waited 90 minutes or more.

Hospitals in New Hampshire, Kansas and Minnesota transferred patients the fastest – within 43 minutes or less. Hospitals in Wyoming, Hawaii and West Virginia were the slowest, taking almost four hours or longer to move heart patients.

Earlier research shows about 50,000 people in the U.S. have stenting performed more than a day after a heart attack, at a point when it is no longer helpful.