Several studies have shown that rapid defibrillation is the single most important intervention that improves outcomes in patients with out-of-hospital cardiac arrest with ventricular fibrillation. However, in many areas of the country, rapid access to defibrillation is not available, and typical survival rates after cardiac arrest are 10 percent or less. Bunch and associates report on follow-up of patients with access to rapid defibrillation after cardiac arrest and its effect on long-term survival and quality of life.
In Rochester, Minn., emergency response personnel have been equipped with automatic defibrillators since 1990. Between November 1990 and December 2000, 330 out-of-hospital cardiac arrests occurred. Two hundred patients (61 percent) presented in ventricular fibrillation, 72 patients in asystole (22 percent), and 58 patients (18 percent) in pulseless electrical activity. Of the 200 patients presenting with cardiac arrest and ventricular fibrillation, 84 (42 percent) survived at least to the point of hospital discharge. All study patients were defibrillated within 10 minutes of the emergency call to 9-1-1. Timing was verified by comparing the dispatch time to internal clocks on the defibrillator devices. A greater likelihood of survival was noted in younger patients and those whose arrest was witnessed. A history of hypertension, digoxin use, or a need for epinephrine during the resuscitation event conferred a higher mortality risk.
The average length of follow-up after cardiac arrest was 4.8 years. Among the 84 patients who were discharged from the hospital, 60 persons (71 percent) were still alive at the end of the follow-up period. Intact neurologic status was present in 79 of the discharged patients (94 percent). Quality of life was assessed by the overall performance category score and showed good overall capability (score of 1) in 74 patients (88 percent of survivors). Overall mortality during the follow-up period after hospital discharge was no different in those with out-of-hospital cardiac arrest compared with age-matched, sex-matched, and disease-matched control subjects.
The authors conclude that rapid defibrillation within 10 minutes for patients with out-of-hospital cardiac arrest who are found in ventricular fibrillation is associated with survival to hospital discharge in about 40 percent of subjects. Most of these survivors were neurologically intact, with a good quality of life.
editor's note: Using different denominators can greatly influence the appearance of study results. The authors in this study based their numbers for long-term survival (quoted at 30 percent) and intact neurologic status (quoted at 40 percent) on the larger group of all patients with ventricular fibrillation arrest, many of whom died within minutes to hours of the cardiac event. No physician expects rapid defibrillation to save all patients with cardiac arrest. The general concern relates to the portion of initial survivors who would have neurologic damage or a very limited life span after defibrillation. If we focus on those who survived the defibrillation event, somewhat reassuring numbers are available from this study. Almost 75 percent of the survivors were still alive at five-year follow-up, and intact neurologic status with good quality of life was present in over 90 percent of the survivors.—B.Z.