An overcrowded ER does not seem to delay patients in getting an emergency procedure to stop a heart attack in progress -- at least at one U.S. hospital, a new study finds. Over the past couple of decades, the number of emergency rooms in the U.S. has dropped by about one-quarter, even as the number of patients visiting them has climbed. That often equals ER overcrowding and research suggests it's taking a toll. A recent study of California ERs, for instance, found that elderly heart attack patients had a higher death rate when their nearest hospital was on a high level of "diversion" -- meaning the ER was so crowded it was turning ambulances away. And some research, though not all, has suggested that when heart attack patients arrive at a crowded ER, their care may be slowed down -- whether they require an invasive procedure or blood-clot-dissolving drugs.