Outcomes of sudden cardiac arrest treated with defibrillation by emergency medical technicians (EMT-Ds) or paramedics in a two-tiered urban EMS system.

Objective: Controversy exists as to the effectiveness of defibrillation by emergency medical technicians (EMT-Ds) in reducing mortality from cardiac arrest in two-tiered EMS systems. This study was performed to assess the impact of EMT-Ds on outcome of sudden cardiac death in a small, urban, modified two-tiered EMS system.

Methods: This was a retrospective, unmatched case-control study comparing the outcomes of patients suffering sudden cardiac death treated by EMT-Ds with paramedic (EMT-P) backup with the outcomes of patients treated by EMT-Ps as first responders. Outcomes were defined as survival to the following endpoints: hospital admission, hospital discharge, and discharge with normal neurologic function (neurologic survival). Differences between groups were considered significant if p < or = 0.05 by Fisher's exact test or t-test.

Results: Three hundred twenty-two patients suffered out-of hospital sudden cardiac deaths over a three-year period and met study inclusion criteria. There were no significant differences in mean age, sex distribution, or incidence of ventricular fibrillation as the presenting rhythm between the groups. Rates of survival to admission, survival to discharge, and neurologic survival were 25.8%, 8.1%, and 5.6%, respectively. Corresponding survival rates for 46 patients treated first by EMT-Ds were 19.6%, 8.7%, and 4.3%. For 276 patients treated by EMT-Ps as first responders, the rates were 26.8%, 8.0%, and 5.8%. There were no significant differences in survival rates between the two response modes, despite a significantly shorter response interval for EMT-Ds (3.6 +/- 1.8 min, vs 4.6 +/- 2.0 min for EMT-Ps). There were likewise no significant differences in survival rates between the two response modes when only patients in ventricular fibrillation or ventricular tachycardia were considered. There were no significant differences in survival rates grouped by presenting rhythm, with the exception of 9.6% neurologic survival in witnessed ventricular fibrillation as compared with 0% in asystole.

Conclusion: EMT defibrillation had no impact on outcome of sudden cardiac death in this small, urban, two-tiered EMS system. Survival rates were similar to those reported for other such systems. However, power to detect significant differences was low, and further study is indicated. Controlled multicenter trials are recommended.