Long-term outcomes among out-of-hospital cardiac arrest survivors with reversible vs. non-reversible causes.

Aims: A reversible cause of out-of-hospital cardiac arrest (OHCA) is vaguely defined in international guidelines as an identifiable transient or potentially correctable condition. However, studies evaluating long-term outcomes of patients experiencing OHCA due to reversible and non-reversible causes are lacking. We aimed to determine differences in long-term outcomes in OHCA survivors according to different aetiology.

Methods and results: From the British Columbia Cardiac Arrest registry, adults with non-traumatic OHCA (2009-2016) surviving to hospital discharge were identified. Patients were categorized by OHCA aetiology combining reversibility and underlying ischaemic aetiology. The primary outcome was a composite of all-cause mortality, recurrent OHCA, or re-hospitalization for sudden cardiac arrest or ventricular arrhythmias. Using the Kaplan-Meier method and multivariable Cox regression models, we compared the risk of the composite outcome according to different OHCA aetiology. Of 1325 OHCA hospital-discharge survivors (median age 62.8 years, 77.9% male), 431 (32.5%) had reversible ischaemic, 415 (31.3%), non-reversible ischaemic, 99 (7.5%), reversible non-ischaemic, and 380 (28.7%), non-reversible non-ischaemic aetiologies. At 3 years post discharge, the Kaplan-Meier event-free rate was highest in patients with a reversible ischaemic aetiology [91%, 95% confidence interval (CI) 87-94%], and lowest in those with a reversible non-ischaemic aetiology (62%, 95% CI 51-72%). In multivariate analyses, compared with non-reversible non-ischaemic cause, reversible ischaemic cause was associated with a significantly lower hazard ratio (HR; 0.52, 95% CI 0.33-0.81), reversible non-ischaemic cause with a significantly higher HR (1.53, 95% CI 1.03-2.32), and non-reversible ischaemic cause with a non-significant HR (0.92, 95% CI 0.64-1.33) for the composite outcome.

Conclusion: Compared to other aetiologies, the presence of a reversible ischaemic cause is associated with improved long-term OHCA outcomes.