Pulseless Electrical Activity Heart Rate and Survival After Out-of-Hospital Cardiac Arrest by Arrest Etiology

Among out-of-hospital cardiac arrest (OHCA) patients presenting with pulseless electrical activity (PEA) and a presumed primary cardiac cause, higher heart rates are associated with improved outcomes. Whether this association holds in OHCA with a presumed non-cardiac etiology (e.g., trauma, poisoning, drowning) remains unknown. This study aimed to evaluate whether arrest etiology modifies the relationship between PEA heart rate and survival, and to characterize this association in patients with OHCA due to a presumed non-cardiac cause.

This cohort study used data from the ROC Cardiac Epistry 3, which includes OHCA patients from 11 North American sites between 2011 and 2015. Patients who were untreated, younger than 18 years, presented in asystole, or had paramedic-witnessed arrests were excluded. The primary outcome was survival to hospital discharge. Patients were categorized into seven groups based on initial PEA heart rate (1–20 bpm, 21–40 bpm, […], ≥120 bpm) and were compared with patients presenting with an initial shockable rhythm. Associations were assessed using multivariable logistic regression models. With a sample size exceeding 15,000 patients, the study had over 95% power to detect an interaction effect corresponding to an odds ratio of 1.1, assuming that 50% of outcome variance was explained by covariates in the model and using a two-sided alpha of 0.05.

Among 120,306 registry patients, 18,540 met inclusion criteria (female: 5,469 [29%]; mean age: 66 years; PEA: 7,746 [42%]; initial shockable rhythm: 10,794 [58%]; OHCA due to a non-cardiac cause: 865 [5%]; OHCA due to a presumed primary cardiac cause: 17,675 [95%]). A significant interaction was observed between arrest cause and the association between PEA heart rate and survival (p<0.001). Among patients with a non-cardiac cause, those with PEA≥80 bpm had higher survival odds than those with an initial shockable rhythm (adjusted odds ratio [AOR] from 4.66 [95%CI: 2.17-9.58] to 37.70 [4.50-316.09]). Conversely, in patients with a presumed primary cardiac cause, PEA<100 bpm was associated with lower survival odds of survival than an initial shockable rhythm (AOR from 0.15 [95%CI: 0.11-0.21] to 0.55 [0.41-0.75]).

PEA heart rate is a strong predictor of survival in OHCA patients with a presumed non-cardiac cause. Pseudo-PEA may be more common in this population.