A model of prehospital death from ventricular fibrillation following myocardial infarction.

Current efforts to reduce prehospital cardiac mortality focus more on deployment of specially equipped ambulances than on reduction of patient or ambulance delays. To evaluate this strategy, we needed to find a method that would isolate the separate effects of patient delay, ambulance delay, and the resuscitative capability of the ambulance. Using published data, we have generated a mathematical model of death from ventricular fibrillation following myocardial infarction that shows the relationship among these three factors. Analyses based on the model indicate that the potential life saving impact of a defibrillation-equipped ambulance is severely limited due to typical patient response patterns. If the ambulance arrives ten minutes after the onset of infarction, defibrillation capabilities will reduce prehospital mortality from 6 percent to 2 percent. After a more typical delay of 60 minutes, the mortality rises sharply to 13 percent for an unequipped ambulance. With a delay of this length, defibrillation capabilities reduce mortality only to about 12 percent.