Rhythm-specific associations between low-flow time and short-term outcomes after out-of-hospital cardiac arrest (OHCA)

Low-flow time (LFT) – time from cardiopulmonary resuscitation (CPR) to return of spontaneous circulation (ROSC) – is a well-established prognostic predictor in resuscitated out-of-hospital cardiac arrest (OHCA) patients. Yet, its interplay with initial rhythm and how this duration determines survival and neurological recovery remain uncertain.

Using a national OHCA registry, we examined rhythm-specific associations between LFT and short-term clinical outcomes.

We analyzed adult (≥16 years), witnessed OHCAs who survived to hospital admission between 2010 to 2021. Our primary outcome was poor neurological recovery at hospital discharge as assessed by Cerebral Performance Category (CPC); CPC of 3-5 reflected poor neurological status. Our secondary outcome was in-hospital mortality. Stratified by initial rhythm (shockable, pulseless electrical activity [PEA] and asystole), we compared differences in LFTs using non-parametric tests and performed multivariable logistic regression for poor neurological recovery and mortality, adjusting for pre-specified Utstein covariates.

Among 3,094 included patients (median age of 63 years, 70.1% males), 38.3% had shockable rhythm. Patients who presented with an initial shockable rhythm had a median (interquartile range [IQR]) LFT of 14.5 (5.5-30) minutes, while those with initial non-shockable rhythms had a median LFT of 28 (19-36) minutes. Longer LFT was consistently associated with CPC3-5 and mortality regardless of rhythm (p<0.001) (Figure 1). In adjusted models, each minute increase in LFT conferred 7-20% higher odds of CPC3-5 and 8-11% higher odds of mortality. Shockable OHCAs retained measurable chances of neurological recovery up to ~50 min of LFT, whereas outcomes of PEA and asystole plateaued beyond ~20 min and ~10 min of LFT respectively (Figure 2).

LFT exerts rhythm-specific associations with neurological recovery and survival among witnessed, resuscitated OHCA who survived to hospital admission. Shockable OHCAs display greater resilience to prolonged resuscitation. Integrating rhythm-specific time-to-ROSC into field and emergency-department algorithms may refine prognostication, optimize resource use, and support shared decision-making during prolonged resuscitation.Figure 1  Figure 2