Purpose: The aim was to compare, through the literature, the biphasic waveforms regarding the first shock efficiency in Out of Hospital Cardiac Arrest (OHCA).
Materials and Methods: This work was carried out in two stages: a selection of the literature and a retrospective study evaluating first shock efficacy. 52 articles were provided by a systematic research on PubMed and Science Direct. After a selection by the title, the abstract and a last thorough reading, 6 studies reporting only cases with
initial ventricular fibrillation (iVF) were selected.
Eligible patients presented a non-traumatic OHCA, an iVF and were shocked by emergency professionals. For each patient, we collected the witness-status, call-to first-shock delay, bystander cardiopulmonary resuscitation (CPR) and survival to hospital discharge. First shock success was defined as termination of iVF 5 seconds after the shock. Success rates from this study and the literature were compared using a two-tailed chi2 test. A p-value<0.05 was considered statistically significant.
Results: From 01/01 to 31/12/17, 363 patients were included. All the first shock efficacies and confounding factors are reported on the table 1. According to these results no study provides statistically significant different result (p≥0.05). Among the 38 patients without defibrillation success 21 (55.3%) had a recurrent VF (refibrillation at least 1 second after the shock artefact) and 17 (44.7%) a persistent VF (refibrillation before the end of the shock artefact).
Conclusion: Although the disparities between the studies, first shock efficacies are mainly located within 85-95% for a selected energy of 120-200J.

4 - First shock efficacy of out-of-hospital cardiac arrest defibrillation