Survival rate and factors associated with 1-month survival of witnessed out-of-hospital cardiac arrest of cardiac origin with ventricular fibrillation and pulseless ventricular tachycardia: the Utstein Osaka project

OBJECTIVE: We reassessed 1-month survival of patients with witnessed out-of-hospital cardiac arrest (OHCA) of cardiac origin with ventricular fibrillation (VF) or pulseless ventricular tachycardia (VT) in Osaka, Japan, and identified factors associated with 1-month survival using updated data from 1998 to 2004 collected based on the Utstein Style. METHODS: Using the Utstein Osaka Project database, we analyzed 1028 cases which met the following criteria: (1) patient age 18 years or older; (2) presumed cardiac origin based on the definition of the Utstein Style; (3) witnessed by citizens; (4) VF or pulseless VT at the time of arrival of the ambulance. The main outcome measure was survival at 1 month after collapse. Variables to develop a predictive model for 1-month survival were selected by stepwise logistic regression. RESULTS: Survival at 1 month was 19.6%. Factors retained in the final logistic regression were age, sex, type of witness, and time interval from (a) ambulance call receipt to cardiopulmonary resuscitation (CPR) by the ambulance crew; (b) ambulance call to defibrillation; (c) CPR by the ambulance crew to hospital arrival. Area under the receiver-operating characteristic curve for the model developed with the six variables was 0.738 and Hosmer-Lemshow goodness-of-fit p-value was 0.94. CONCLUSION: We successfully developed a model to estimate the probability of 1-month survival using variables easy to collect in the early phase of resuscitation, and this model would help physicians and family members predict the likelihood of 1-month survival of OHCA patients on admission.