Abstract 296: Determinants of Incidence of Ventricular Fibrillation as First Recorded Rhythm During Out-of-Hospital Cardiac Arrest and Association with Long-Term Neurological Outcomes: Observations from a Large Randomized Clinical Study

Abstract

Background: We sought to identify the factors that were associated with higher incidence of VF and survival with good neurological function in the ResQ Trial patients that compared standard cardiopulmonary resuscitation (S-CPR) versus active compression decompression CPR with an inspiratory impedance threshold device (ACD+ITD) in patients with out of hospital cardiac arrest (OHCA). Methods: A retrospective analysis of a randomized multicenter clinical study of 1655 patients with OHCA. 88.3% (106/120) of the patients discharged with good neurological function [Modified Rankin Score (MRS)≤3] had a first recorded rhythm of ventricular fibrillation/pulseless ventricular tachycardia (VF). The first rhythm was recorded in 99.4% (1645/1655) of the cases about 9.5 minutes after 911 call, on average 3 minutes after the arrival of EMS on the scene and after CPR was performed for at least 2 minutes. Results: A total of 32.8% of the patients had VF as presenting rhythm and 42.8% received bystander CPR. Presence of bystander CPR was associated with a higher VF incidence only in the S-CPR group (40.8% versus 23.1% with no bystander, p=0.001) but survival was 7.6% versus 4.6% p=0.09. Presence or absence of bystander CPR let to similar VF incidence and survival in the ACD+ITD group 36.1% versus 33.9% and 9.0% versus 8.9% respectively, p>0.2. After propensity adjustment for witnessed arrest, age <67, gender, public location, bystander CPR lost significance. In the absence of bystander CPR, ACD+ITD significantly increased the incidence of first recorded VF compared to S-CPR from 106/459 (23.1%) to 164/484 (33.9%) [OR 1.71, 95% CI (1.27, 2.30), p<0.001], and in patients with VF, return of spontaneous circulation increased from 65/459 (14.2%) to 104/484 (21.5%) [OR 1.66, 95% CI (1.16, 2.37), p=0.004], leading to an overall doubling of survival with MRS≤3 from 21/455 (4.6%) to 43/482 (8.9%) [OR 2.02, 95% CI (1.15, 3.65), p=0.009]. After propensity adjustment ACD+ITD remained a significant predictor of an MRS≤3, (p= 0.02). Conclusions: VF was the most important predictor of survival with MRS≤3. In the absence of bystander CPR, ACD+ITD increased VF incidence as the first recorded rhythm and doubled survival to hospital discharge with MRS≤3 compared to S-CPR.