TUESDAY, June 21 (HealthDay News) -- Only 11 percent of patients who experience a potentially deadly type of heart attack and who need to be transferred to another hospital for procedures such as balloon angioplasty or stent placement are transferred within the recommended time of 30 minutes.

Instead, a new study finds the average time patients waited to be transferred was over an hour, a delay that researchers say may increase the risk of death.

ST-segment elevation myocardial infarction, or STEMI, is one of the most serious types of heart attacks.

Angioplasty and stent placement are known as percutaneous coronary intervention (PCI), which is the preferred method of restoring blood flow in patients with STEMI. However, about 75 percent of hospitals in the United States aren't able to perform acute PCI, which means that many patients with STEMI have to be transferred to another hospital, according to background information in the study.

Researchers analyzed data from 14,821 STEMI patients who were transferred from one hospital to another for primary PCI between January 2007 and March 2010. The median duration of time from arrival to discharge at the first hospital (door-in to door-out [DIDO] time) was 68 minutes.

Only 1,627 of the patients (11 percent) had a DIDO time of 30 minutes or less, while 56 percent had a DIDO time of more than 60 minutes and 35 percent had a DIDO time of more than 90 minutes.

The death rate for patients with a DIDO time of 30 minutes or less was 2.7 percent, compared with 5.9 percent for those with a DIDO time of more than 30 minutes, found Dr. Tracy Y. Wang, of Duke University Medical Center, and colleagues.

Their study appears in the June 22/29 issue of the Journal of the American Medical Association.

More information

The American Heart Association has more about heart attack.