abstract
Background. We sought to identify the factors that were associated with higher incidence of ventricular fibrillation and survival with good neurologic function in the ResQTrial, which 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 1,655 patients with OHCA. 88.3% (106/120) of the patients discharged with good neurologic function (modified Rankin score [MRS] ¡Â3) had a first recorded rhythm of ventricular fibrillation/pulseless ventricular tachycardia (VF). The first rhythm was recorded in 99.4% (1,645/1,655) of the cases about 9.5 minutes after the 9-1-1 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 the presenting rhythm and 42.8% received bystander CPR. The 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 led 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 years, gender, and public location, bystander CPR lost significance. In the absence of bystander CPR, ACD+ITD significantly increased the incidence of first-recorded VF compared with S-CPR from 106 of 459 patients (23.1%) to 164 of 484 patients (33.9%) (odds ratio [OR] 1.71, 95% confidence interval [CI] 1.27, 2.30, p < 0.001), and in patients with VF, return of spontaneous circulation increased from 65 of 459 patients (14.2%) to 104 of 484 patients (21.5%) (OR 1.66, 95% CI 1.16, 2.37, p = 0.004), leading to an overall doubling of survival with MRS ¡Â3 from 21 of 455 patients (4.6%) to 43 of 482 patients (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 ¡Â3 (p = 0.02). Conclusions. VF was the most important predictor of survival with MRS ¡Â3. In the absence of bystander CPR, ACD+ITD increased VF incidence as the first-recorded rhythm and doubled survival to hospital discharge with MRS ¡Â3 compared with S-CPR.
