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Am J Emerg Med. 2017 Feb;35(2):206-213. doi: 10.1016/j.ajem.2016.10.042. Epub 2016 Oct 25.

Conversion to shockable rhythms during resuscitation and survival for out-of hospital cardiac arrest.

Author information

Saw Swee Hock School of Public Health, National University of Singapore, Singapore. Electronic address:
Singapore Institute for Clinical Sciences, Agency for Science, Technology and Research, A*STAR, Singapore.
Department of Emergency Medicine, Singapore General Hospital, Singapore.
Emergency Medicine Residency Program, SingHealth Services, Singapore.
Dubai Corporation for Ambulance Services, Dubai, United Arab Emirates.
Emergency Department, Tan Tock Seng Hospital, Singapore.
Department of Emergency and Trauma, Hospital Sungai Buloh, Selangor, Malaysia.
Critical Care Medical Center, Osaka National Hospital, Osaka, Japan.
Epidemiology Department, Singapore Clinical Research Institute Pte Ltd, Singapore.
Department of Emergency Medicine, Singapore General Hospital, Singapore; Health Services and Systems Research, Duke-NUS Graduate Medical School, Singapore.



In out of hospital cardiac arrest (OHCA), the prognostic influence of conversion to shockable rhythms during resuscitation for initially non-shockable rhythms remains unknown. This study aimed to assess the relationship between initial and subsequent shockable rhythm and post-arrest survival and neurological outcomes after OHCA.


This was a retrospective analysis of all OHCA cases collected from the Pan-Asian Resuscitation Outcomes Study (PAROS) registry in 7 countries in Asia between 2009 and 2012. We included OHCA cases of presumed cardiac etiology, aged 18-years and above and resuscitation attempted by EMS. We performed multivariate logistic regression analyses to assess the relationship between initial and subsequent shockable rhythm and survival and neurological outcomes. 2-stage seemingly unrelated bivariate probit models were developed to jointly model the survival and neurological outcomes. We adjusted for the clustering effects of country variance in all models.


40,160 OHCA cases met the inclusion criteria. There were 5356 OHCA cases (13.3%) with initial shockable rhythm and 33,974 (84.7%) with initial non-shockable rhythm. After adjustment of baseline and prehospital characteristics, OHCA with initial shockable rhythm (odds ratio/OR=6.10, 95% confidence interval/CI=5.06-7.34) and subsequent conversion to shockable rhythm (OR=2.00,95%CI=1.10-3.65) independently predicted better survival-to-hospital-discharge outcomes. Subsequent shockable rhythm conversion significantly improved survival-to-admission, discharge and post-arrest overall and cerebral performance outcomes in the multivariate logistic regression and 2-stage analyses.


Initial shockable rhythm was the strongest predictor for survival. However, conversion to subsequent shockable rhythm significantly improved post-arrest survival and neurological outcomes. This study suggests the importance of early resuscitation efforts even for initially non-shockable rhythms which has prognostic implications and selection of subsequent post-resuscitation therapy.

[Indexed for MEDLINE]

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