Background - It is well known that cardiopulmonary resuscitation (CPR) should be attempted as early as possible after out-of-hospital cardiac arrest (OHCA). However, it is unclear about the impact of time to CPR on OHCA outcome by first documented rhythm (pulseless ventricular tachycardia/ventricular fibrillation [pVT/VF], pulseless electric activity [PEA], and asystole). Methods and Results - We enrolled 257 354 adult witnessed OHCA patients between 2007 and 2012 from a prospective nationwide population-based cohort database in Japan. We evaluated relationships between time from collapse to first CPR and neurologically favorable 1-month survival defined as Glasgow-Pittsburg cerebral performance category 1 or 2 by first documented rhythm after witnessed OHCA. We used logistic model for the estimation of prognosis. The number of OHCA patients with pVT/VF, PEA, and asystole were 38 661, 96 906, and 121 787, respectively. The overall neurologically favorable 1-month survival rates were 21.3% in patients with pVT/VF, 2.7% PEA, and 0.6% asystole. The proportion of asystole increased as the time from collapse to CPR delayed, whereas those of pVT/VF and PEA decreased (trend P<0.001). Estimated incidences of end-point after OHCA became lower as first CPR delayed irrespective of type of first documented rhythm, but were different by the rhythm. The average percentage point decreases in neurologically favorable 1-month survival probability for each incremental minute of CPR delay were 8.3%, 4.4%, and 6.4% for patients with pVT/VF, PEA, and asystole, respectively. Conclusions - The OHCA outcome differed by time to first CPR and first documented rhythm. Shortening of time to first CPR is crucial for improving the OHCA outcome.
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