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Victims with shock-able initial arrest rhythms (ventricular fibrillation or pulse-less ventricular tachycardia, VF/VT) have much better outcomes from out-of-hospital cardiac arrest (OHCA) than those with non-shock-able initial rhythms (pulse-less electrical activities, PEA or asystole). Prompt defibrillation is believed pivotal to terminate lethal shock-able arrest rhythms. In the study, we were to identify those factors which were associated with likelihood of shock-able rhythms first recorded when out-of-hospital cardiac arrest occurred.
A multicenter, secondary, retrospective and observational analysis was performed on all adult non-traumatic OHCA in the Resuscitation Outcome Consortium (ROC) RIMED study from June 2007 through November 2009. Of a total of 17177 OHCA cases in PRIMED study, 13421 of them were enrolled in this study when those OHCA patients with DNR order, or initial rhythms unknown, or arrest caused by obvious cause were excluded. We reported their demographics and episode characteristics for all enrolled cases. A multivariable logistic regression was employed to identify factors which were associated with likelihood of VF/VT recorded as shock-able initial arrest rhythms.
Among 13421 adult non-traumatic OHCA cases with initial rhythms recorded, 3227 (26.3%) of them had shock-able rhythms, while 9894 (73.7%) patients were in non-shock-able rhythms. Of the OHCA with shock-able arrest rhythms, 1850(52.5%) obtained return of spontaneous circulation (ROSC) in the field, while 912 (25.9%) survived to hospital discharge. On the other hand, 2489(25.2%) of the OHCA with non-shock-able arrest rhythms obtained ROSC in the field, while 325 (3.3%) of them survived to hospital discharge. Multivariable regression analysis revealed those factors which indicated likelihood of shock-able rhythms recorded were: age(OR:992,95%CI 0.989-0.994,p=0.000), male gender (OR0.554, 95%CI 0.504-0.609,p=0.000), white race (OR:0.486, 95%CI 0.308-0.768,p=0.002), Hispanic (OR:0.582,95%CI 0.470-0.719,p=0.000),episode in home residence (OR0.424, 95%CI 0.361-0.499,p=0.000), healthcare facilities (OR0.272, 95%CI 0.192-0.387,p=0.000) or residential institution (OR0.153, 95%CI 0.166-0.202,p=0.000), episodes in public building (OR:0.651,95%CI 0.466-0.909,p=0.012), place of recreation (OR1.725, 95%CI 1.239-2.401,p=0.001), arrest witnessed by EMS (OR1.625, 95%CI 1.352-1.953,p=0.000) or bystander (OR3.192, 95%CI 2.911-3.501,p=0.000) and those with bystanders CPR (OR1.438, 95%CI 1.312-1.575,p=0.000), pre-hospital response time(OR:0.953,95%CI 0.935-0.973,p=0.000).
Some demographics and pre-hospital characteristics were proved associated with likelihood of shock-able arrest rhythms first recorded in OHCA victims, which might help installation of accessible defibrillation devices so as to deliver prompt shock.