Temporal trends in out-of-hospital cardiac arrest with an initial non-shockable rhythm in Singapore

Abstract

Aim: Out-of-hospital cardiac arrest (OHCA) with an initial non-shockable rhythm is the predominant form of OHCA in adults. We evaluated its 10-year trends in epidemiology and management in Singapore.

Methods: Using the national OHCA registry we studied the trends of 20,844 Emergency Medical Services-attended adult OHCA from April 2010 to December 2019. Survival to hospital discharge was the primary outcome. Trends and outcomes were analyzed using linear and logistic regression, respectively.

Results: Incidence rates of adult OHCAs increased during the study period, driven by non-shockable OHCA. Compared to shockable OHCA, non-shockable OHCAs were significantly older, had more co-morbidities, unwitnessed and residential arrests, longer no-flow time, and received less bystander cardiopulmonary resuscitation (CPR) and in-hospital interventions (p < 0.001). Amongst non-shockable OHCA, age, co-morbidities, residential arrests, no-flow time, time to patient, bystander CPR and epinephrine administration increased during the study period, while presumed cardiac etiology decreased (p < 0.05). Unlike shockable OHCA, survival for non-shockable OHCA did not improve (p < 0.001 for trend difference). The likelihood of survival for non-shockable OHCA significantly increased with witnessed arrest (adjusted odds ratio (aOR) 2.02) and bystander CPR (aOR 3.25), but decreased with presumed cardiac etiology (aOR 0.65), epinephrine administration (aOR 0.66), time to patient (aOR 0.93) and age (aOR 0.98). Significant two-way interactions were observed for no-flow time and residential arrest with bystander CPR (aOR 0.96 and 0.40 respectively).

Conclusion: The incidence of non-shockable OHCA increased between 2010 and 2019. Despite increased interventions, survival did not improve for non-shockable OHCA, in contrast to the improved survival for shockable OHCA.

Keywords: Non-shockable rhythms; Out-of-hospital cardiac arrest; Survival; Trends.

Fig. 1

Patient selection. Selection of adult, EMS-attended OHCA in Singapore from April 2010 to December 2019. Blue box indicates OHCA patients captured by the national OHCA registry. Red box indicates final study population. Abbreviation: OHCA, out-of-hospital cardiac arrest.

Fig. 2

Temporal trends of adult, EMS-attended OHCA. This figure shows the temporal trends of adult EMS-attended OHCA in Singapore, stratified by rhythm type where (a) and (b) show incidence and outcomes, (c) and (d) show patient and event characteristics, and (e) and (f) show interventions. Incidence was calculated per 100,000 population and adjustment for age was performed using direct method, based on World Health Organisation population data. TTM and PCI are expressed as proportions of OHCA subgroup (adult, EMS-attended OHCA who survived to hospital admission). Abbreviation: EMS, Emergency Medical Services; OHCA, out-of-hospital cardiac arrest; ROSC, return of spontaneous circulation; CCI, Charlson Comorbidity Index; CPR, cardiopulmonary resuscitation; TTM, targeted temperature management; PCI, percutaneous coronary intervention.

Fig. 3

Predictors of survival and neurological outcome for non-shockable OHCA. This figure shows the predictors of survival to hospital discharge for non-shockable OHCA. EMS-witnessed OHCA and non-shockable OHCA with no subtype (PEA vs asystole) were excluded from the analysis. This model included clinically relevant and statistically significant interaction terms such as bystander CPR and arrest location, bystander CPR and no-flow time. Time to patient refers to the interval, in minutes, between time call received by the dispatch center and the time of patient contact by either the ambulance or rapid responder dispatched via the same dispatch center. * indicates significant predictors of discharge with good neurological outcomes (CPC 1 or 2) for non-shockable OHCA. Abbreviations: OHCA, out-of-hospital cardiac arrest; BCPR, bystander cardiopulmonary resuscitation; PCI, percutaneous coronary intervention; OR, odds ratio; CI, confidence interval; CPC, Cerebral Performance Category.