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September 15, 1999

Improving Survival Following Out-of-Hospital Cardiac Arrest

Author Affiliations

Margaret A.WinkerMD, Deputy EditorIndividualAuthorPhil B.FontanarosaMD, Interim CoeditorIndividualAuthor

JAMA. 1999;282(11):1033-1034. doi:10-1001/pubs.JAMA-ISSN-0098-7484-282-11-jac90008

To the Editor: Phase 2 of the Ontario Prehospital Advanced Life Support (OPALS) study1 prospectively assessed the effectiveness of interventions for out-of-hospital cardiac arrest (OHCA). The improvement in survival from phase 1 to phase 2 illustrates the importance of system optimization in the treatment of OHCA.

However, the authors' statement that "phase 2 has clearly shown the effectiveness of an inexpensive program of rapid defibrillation" is not supported by the data. In fact, there was no difference in survival for patients initially found to have ventricular fibrillation (VF) or ventricular tachycardia (VT) (10.0% vs 11.9%; P=.17). The appropriate denominator for assessing the impact of rapid defibrillation is the population that would benefit from this intervention—patients who have VF or VT. It was only after the inclusion of all patients with cardiac arrest (including those with pulseless electrical activity and asystole) that a significant difference in survival was found. Although patients with pulseless electrical activity or asystole may have benefited from shorter response times and higher rates of cardiopulmonary resuscitation, they could not have benefited from defibrillation, rapid or not. Shorter response times may lead to a higher incidence of VF; however, as the authors point out, this did not occur with phase 2 of the OPALS study. This is further evidence that rapid defibrillation was not the primary reason for the improvement in survival during phase 2.

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