title: Three-phase model of cardiac arrest: time-dependent benefit of bystander cardiopulmonary resuscitation.
abstract: Evidence has suggested that the pathophysiology of ventricular fibrillation cardiac arrest may consist of 3 time-sensitive phases: electrical, circulatory, and metabolic. We performed a retrospective cohort study of adults in a metropolitan county who had had witnessed ventricular fibrillation arrest before emergency medical services were undertaken to investigate this 3-phase model with regard to bystander cardiopulmonary resuscitation (CPR). We hypothesized that the survival benefit from bystander CPR depends on the collapse-to-shock interval, with the highest benefit occurring during the circulatory phase. The collapse-to-shock interval was a priori grouped into 4 categories: 1 to 5, 6 to 7, 8 to 10, and > or = 11 minutes. We used logistic regression analysis to assess whether the association between CPR and survival to hospital discharge depended on the collapse-to-shock interval category. Of the 2,193 events meeting the inclusion criteria, 67.0% had received bystander CPR. The average collapse-to-shock interval was 8.2 +/- 2.8 minutes. The survival rate was 33.4%. A higher likelihood of survival was associated with bystander CPR (odds ratio [OR] 1.41, 95% confidence interval [CI] 1.15 to 1.73) and a shorter collapse-to-shock interval (OR -1.84, 95% CI 1.62 to 2.10, for each additional SD of 2.8 minutes less) after adjustment. The beneficial association of CPR increased as the collapse-to-shock interval increased (p = 0.05 for interaction). The bystander CPR was associated with an OR of survival of 0.96 (95% CI 0.64 to 1.46) for a 1- to 5-minute collapse-to shock interval, OR of 1.25 (95% CI 1.00 to 1.58) for a 6- to 7-minute interval, OR of 1.62 (95% CI 1.25 to 2.11) for an 8- to 10-minute interval, and OR of 2.11 (95% CI 1.32 to 3.37) for an > or = 11-minute interval. The results of this investigation support a phased model of ventricular fibrillation arrest. The findings suggest that the transition from the electrical to circulatory phase may occur at about 5 minutes, and the circulatory phase may extend to 15 minutes.
authors.affiliation: Department of Medicine, University of Washington School of Medicine, Seattle, Washington, USA. cgilmore@u.washington.edu
authors.forename: Christina M
authors.initials: CM
authors.lastname: Gilmore
authors.forename: Thomas D
authors.initials: TD
authors.lastname: Rea
authors.forename: Linda J
authors.initials: LJ
authors.lastname: Becker
authors.forename: Mickey S
authors.initials: MS
authors.lastname: Eisenberg
mesh_terms: D000368:Aged; D016887:Cardiopulmonary Resuscitation / Q000379:methods*; D005260:Female; D005500:Follow-Up Studies; D006323:Heart Arrest / Q000209:etiology / Q000401:mortality / Q000628:therapy*; D006801:Humans; D008297:Male; D008875:Middle Aged; D008962:Models, Theoretical; D016017:Odds Ratio; D012189:Retrospective Studies; D012307:Risk Factors; D015996:Survival Rate / Q000639:trends; D016896:Treatment Outcome; D014693:Ventricular Fibrillation / Q000150:complications* / Q000503:physiopathology