Association between Conversion to Shockable Rhythms and Survival with Favorable Neurological Outcomes for Out-of-Hospital Cardiac Arrests

Abstract

Background

The initial cardiac rhythm in out-of-hospital cardiac arrest (OHCA) portends different prognoses and affects treatment decisions. Initial shockable rhythms are associated with good survival and neurological outcomes but there is conflicting evidence for those who initially present with non-shockable rhythms. The aim of this study is to evaluate if OHCA with conversion from non-shockable (i.e., asystole and pulseless electrical activity) rhythms to shockable rhythms compared to OHCA remaining in non-shockable rhythms is associated with better survival and neurological outcomes.

Method

OHCA cases from the Pan-Asian Resuscitation Outcomes Study registry in 13 countries between January 2009 and February 2018 were retrospectively analyzed. Cases with missing initial rhythms, age <18 years, presumed non-medical cause of arrest, and not conveyed by emergency medical services were excluded. Multivariable logistic regression analysis was performed to evaluate the relationship between initial and subsequent shockable rhythm, survival to discharge, and survival with favorable neurological outcomes (cerebral performance category 1 or 2).

Results

Of the 116,387 cases included. 11,153 (9.6%) had initial shockable rhythms and 9,765 (8.4%) subsequently converted to shockable rhythms. Japan had the lowest proportion of OHCA patients with initial shockable rhythms (7.3%). For OHCA with initial shockable rhythm, the adjusted odds ratios (aOR) for survival and good neurological outcomes were 8.11 (95% confidence interval [CI] 7.62-8.63) and 15.4 (95%CI 14.1-16.8) respectively. For OHCA that converted from initial non-shockable to shockable rhythms, the aORs for survival and good neurological outcomes were 1.23 (95%CI 1.10-1.37) and 1.61 (95%CI 1.35-1.91) respectively. The aORs for survival and good neurological outcomes were 1.48 (95%CI 1.22-1.79) and 1.92 (95%CI 1.3 − 2.84) respectively for initial asystole, while the aOR for survival in initial pulseless electrical activity patients was 0.83 (95%CI 0.71-0.98). Prehospital adrenaline administration had the highest aOR (2.05, 95%CI 1.93-2.18) for conversion to shockable rhythm.

Conclusion

In this ambidirectional cohort study, conversion from non-shockable to shockable rhythm was associated with improved survival and neurologic outcomes compared to rhythms that continued to be non-shockable. Continued advanced resuscitation may be beneficial for OHCA with subsequent conversion to shockable rhythms.

Disclosure statement

Prof Ong has a licensing agreement and patent filing (Application no: 13/047,348) pending with ZOLL Medical Corporation for a study titled ‘Method of predicting acute cardiopulmonary events and survivability of a patient’. All other authors have no commercial associations or sources of support that might pose a conflict of interest.

Acknowledgments

Pan-Asian Resuscitation Outcomes Study Clinical Research Network Participating Site Investigators: Ho RH (Chonnam National University Medical School and Hospital, Gwangju, Korea), P Khruekarnchana (Rajavithi Hospital, Bangkok, Thailand), J Supasaowapak (Rajavithi Hospital, Bangkok, Thailand), BSH Leong (National University Hospital, Singapore), NE Doctor (Sengkang General Hospital, Singapore), LP Tham (KK Women’s & Children’s Hospital, Singapore), MYC Chia (Tan Tock Seng Hospital, Singapore), HN Gan (Changi General Hospital, Singapore), SO Cheah (Urgent Care Clinic International, Singapore), WM Ng (Ng Teng Fong General Hospital, Singapore), DR Mao (Khoo Teck Puat Hospital, Singapore), KD Wong (Hospital Pulau Pinang, Penang, Malaysia), K Sarah (Hospital Sungai Buloh, Selangor, Malaysia), R Rao (GVK Emergency Management and Research Institute, Telangana, India), M Vimal (GVK Emergency Management and Research Institute, Telangana, India), Gaerlan FJ (Southern Philippines Medical Center, Davao, Philippines), B Velasco (East Avenue Medical Center, Manila, Philippines), SA Zhou (Zhejiang Provincial People’s Hospital, Zhejiang, China), W Cai (Zhejiang Provincial People’s Hospital, Zhejiang, China), N Khan (Aga Khan University Hospital, Karachi, Pakistan), DN Son (Bach Mai Hospital, Hanoi, Vietnam), DA Nguyen (Bach Mai Hospital, Hanoi, Vietnam), YY Ng (Tan Tock Seng Hospital, Singapore), A Shalini (Emergency Medical Services Department, Singapore Civil Defence Force, Singapore), T Tagami (Nippon Medical School Tama Nagayama Hospital, Tokyo, Japan), S AlQahtani (National Ambulance, Abu Dhabi, United Arab Emirates), M El Sayed (American Beirut Hospital, Beirut, Lebanon). We would like to thank the late Susan Yap from the Department of Emergency Medicine, Singapore General Hospital for her support and coordination of the study. We would also like to thank Patricia Tay from the Singapore Clinical Research Institute for her role as secretariat for the PAROS network.

Additional information

Funding

This work was supported by the National Medical Research Council, Clinician Scientist Awards, Singapore (NMRC/CSA/024/2010 and NMRC/CSA/0049/2013), Ministry of Health, Health Services Research Grant, Singapore (HSRG/0021/2012) and Laerdal Foundation (20040). AFWH was supported by the Estate of Tan Sri Khoo Teck Puat (Khoo Clinical Scholars Programme), Khoo Pilot Award (KP/2019/0034), Duke-NUS Medical School and National Medical Research Council (NMRC/CS_Seedfd/012/2018).