(FORTUNE Magazine) – The single most critical factor in saving the life of a heart attack victim is how quickly blood resumes flowing through the coronary artery. The longer the heart goes without blood, the greater the damage. So your chance of surviving a heart attack is highest in places that have well-organized, well-equipped emergency medical services (EMS). According to Odelia Braun, medical director of the California Center for Pre-Hospital Research and Training, the best have 911 telephone links, ambulances and fire engines with defibrillation paddles for restoring heartbeats, and paramedics who accompany the ambulance and administer intravenous drugs if necessary. What's the best U.S. city to have a heart attack in? Virtually every medical authority agrees that Seattle is No. 1. Says Braun: ''Seattle pioneered in quick-response defibrillation and community classes in cardiopulmonary resuscitation. It has a sophisticated system, where the highest-trained personnel go out on the most critical calls. Paramedics send EKGs ahead by phone to physicians at the hospital, and administer appropriate clot- dissolving drugs while the patient is still in the ambulance.'' Braun also gives top marks for emergency medical services to Austin, Texas; Columbus, Ohio; Eugene, Oregon; Houston; Milwaukee; Pittsburgh; Phoenix; and Salt Lake City. Urbanites aren't the only lucky ones. Braun considers EMS outstanding in most of rural Iowa and some parts of Kansas.