Initial electrical frequency predicts survival and neurological outcome in out of hospital cardiac arrest patients with pulseless electrical activity.

BACKGROUND: Outcome is generally poor in out of hospital cardiac arrests (OHCA) with initial non-shockable rhythms. Termination of resuscitation rules facilitate early prognostication at the scene to cease resuscitation attempts in futile situations and to proceed advanced life support in promising conditions. As pulseless electrical activity (PEA) is present as first rhythm in every 4th OHCA we were interested if the initial electrical frequency in PEA predicts survival.

METHODS: All patients >18 years of age with non-traumatic OHCA and PEA as first rhythm between August 2013 and August 2015 from the Vienna Cardiac Arrest Registry were included in this retrospective observational study. Defibrillator and epidemiological data from the emergency medical system as survival data were processed considering the initial electrical activity in PEA and 30 days survival.

RESULTS: Out of 2149 OHCA patients, a total of 504 PEA patients were eligible for analyses. These patients were stratified into 4 groups according the initial electrical frequency in PEA: 10-24/min, 25-39/min, 40-59/min, >60/min. Compared to a frequency >60/min all other subgroups were associated with higher mortality especially those with an initial electrical frequency 10-24 (adjusted OR 0.56 (0.39-0.79) p = .001 for each category chance). QRS duration in PEA did not influence outcome. Patients in the >60/min group showed a 30-days-survival rate of 22% and a good neurological outcome in 15% of all patients - comparable to shockable cardiac arrest rhythms.

CONCLUSION: Regardless of other resuscitation factors, higher initial electrical frequency in PEA is associated with increased odds of survival and good neurological outcome.