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Objective In out-of-hospital cardiac arrest (OHCA) with ventricular fibrillation (VF) the frequency-based waveform characteristic, amplitude-spectral area (AMSA) is associated with hospital discharge and good neurological outcome, yet AMSA is also known to increase in response to chest compressions (CC). In addition to rate and depth, well performed CC provides good chest recoil without leaning, reflected in the release velocity (RV). We hypothesized that AMSA is associated with hospital discharge and good neurological outcome independent of CC quality. Methods OHCA patients (age≥18), with initial rhythm of VF from an Utstein-Style database were analyzed. AMSA was measured prior to each shock, and averaged for each subject (AMSA-avg). Primary endpoint was hospital discharge and secondary endpoint was a good neurological outcome. Univariate and stepwise multivariable logistic regression, and receiver–operator–characteristic (ROC) analyses were performed. Factors analyzed were age, sex, witnessed status, time from dispatch to monitor/defibrillator application, number of shocks, first shock AMSA (AMSA 1 ), AMSA-avg, averaged pre-shock pause, CC rate, depth, and RV. Results 140 subjects were analyzed. Hospital discharge was 31% and with good neurological outcome in 24% (77% of those discharged). AMSA-avg ( p p =0.002), and age ( p =0.029) were independently associated with hospital discharge, with a non-significant trend for witnessed status ( p =0.069), with AUC=0.846 for the multivariate model. For good neurological outcome, AMSA-avg ( p =0.001) and RV ( p =0.001) remained independently significant, with AUC=0.782. Conclusion In OHCA with an initial rhythm of VF, AMSA-avg and CC RV are both highly and independently associated with hospital discharge and good neurological outcome.

In retrospective swine and human investigations of ventricular fibrillation (VF) cardiac arrest, the amplitude-spectral area (AMSA), determined from the VF waveform, can predict defibrillation and a return of spontaneous circulation (ROSC).We hypothesized that an algorithm using AMSA in real time to direct postshock chest compression (CC) duration would shorten the time to ROSC and improve neurological outcome in a swine model of VF cardiac arrest with acute myocardial infarction (AMI) or nonischemic myocardium.AMI was induced by occlusion of the left anterior descending artery. VF was untreated for 10 min. Animals were randomized to either traditional resuscitation with 2 min of CC after each shock or to an AMSA-guided algorithm where postshock CCs were shortened to 1 min if the preshock AMSA exceeded 20 mV-Hz.A total of 48 animals were studied, 12 in each group (AMI vs. normal, and traditional vs. AMSA-guided). There was a nonsignificant shorter time to ROSC with an AMSA-guided approach in AMI swine (17.2 ± 3.4 vs. 18.5 ± 4.7 min, p = NS), and in normal swine (13.5 ± 1.1 vs. 14.4 ± 1.2, p = NS). Neurological outcome was similar between traditional and AMSA-guided animals. AMSA predicted ROSC (p0.001), and a threshold of 20 mV-Hz gave a sensitivity of 89%, with specificity of 29%.Although AMSA predicts ROSC in a swine model of VF arrest in both AMI and normal swine, a waveform-guided approach that uses AMSA to direct postshock CC duration does not significantly shorten the time to ROSC or alter neurological outcome.

BackgroundPrevious investigations of out-of-hospital cardiac arrest (OHCA) have shown that the waveform characteristic amplitude spectral area (AMSA) can predict successful defibrillation and return of spontaneous circulation (ROSC) but has not been studied previously for survival.ObjectivesTo determine whether AMSA computed from the ventricular fibrillation (VF) waveform is associated with pre-hospital ROSC, hospital admission, and hospital discharge.MethodsAdults with witnessed OHCA and an initial rhythm of VF from an Utstein style database were studied. AMSA was measured prior to each shock and averaged for each subject (AMSA-avg). Factors such as age, sex, number of shocks, time from dispatch to monitor/defibrillator application, first shock AMSA, and AMSA-avg that could predict pre-hospital ROSC, hospital admission, and hospital discharge were analyzed by logistic regression.ResultsEighty-nine subjects (mean age 62 ± 15 years) with a total of 286 shocks were analyzed. AMSA-avg was associated with pre-hospital ROSC (p = 0.003); a threshold of 20.9 mV-Hz had a 95% sensitivity and a 43.4% specificity. Additionally, AMSA-avg was associated with hospital admission (p < 0.001); a threshold of 21 mV-Hz had a 95% sensitivity and a 54% specificity and with hospital discharge (p < 0.001); a threshold of 25.6 mV-Hz had a 95% sensitivity and a 53% specificity. First-shock AMSA was also predictive of pre-hospital ROSC, hospital admission, and discharge. Time from dispatch to monitor/defibrillator application was associated with hospital admission (p = 0.034) but not pre-hospital ROSC or hospital discharge.ConclusionsAMSA is highly associated with pre-hospital ROSC, survival to hospital admission, and hospital discharge in witnessed VF OHCA. Future studies are needed to determine whether AMSA computed during resuscitation can identify patients for whom continuing current resuscitation efforts would likely be futile.

We appreciate the thoughtful letter to the editor by Drs Shiyovich, Gerovich, and Katz. We examined whether an association exists between when chest compressions (CC) are resumed after a shock that defibrillates ventricular fibrillation (VF) and when VF may recur after that shock, in a cohort of witnessed cardiac arrest victims in Arizona. We used 2 main statistical analyses. We first used regression analysis to see whether there was a relationship between CC resumption and VF recurrence. This test considered all VF refibrillations (n=166), and no relationship to CC resumption was found, and furthermore, the randomness is visually apparent in the scatter diagrams of Figure 3. Second, we looked at the risk of VF recurrence in the first 30 …

Background— Prior investigation of out-of-hospital cardiac arrest has raised the concern that ventricular fibrillation (VF) recurrence may be triggered by chest compression (CC) resumption. We investigated predictors of VF recurrence after defibrillation, including timing of CC resumption. Methods and Results— Patients with witnessed out-of-hospital cardiac arrest and initial rhythm of VF from an Utstein-style database were analyzed. For each shock that defibrillated VF, CC resumption and VF recurrence times were determined. Shocks were classified according to postshock rhythm. Factors (age, sex, time from dispatch to monitor/defibrillator application, and CC resumption) that could predict VF recurrence were analyzed. CC resumption was categorized into groups: CC1, 1 to 5 seconds; CC2, 6 to 10 seconds; CC3, 11 to 30 seconds; and CC4, >30 seconds. Eighty-eight subjects were analyzed, with a total of 285 shocks, with 226 shocks that achieved asystole (n=102), organized rhythm (n=120), or monomorphic ventricular tachycardia (n=4). After a successful shock, CC resumption occurred at a median (interquartile range) of 8 (5–18) seconds. VF recurred after 166 shocks (74%) and recurred within 30 seconds in 69 shocks. There was no significant relationship between VF recurrence and factors analyzed including CC resumption time, nor stratified by postshock rhythm. The hazard ratios (HRs) for VF recurrence within 30 seconds for later CC groups (CC2, CC3, and CC4) relative to early CC resumption (CC1) were as follows: HR(CC2)=1.05 ( P =0.9); HR(CC3)=1.75 ( P =0.1); and HR(CC4)=0.67 ( P =0.4). Conclusions— VF recurrence within 30 seconds of a defibrillatory shock was not dependent on timing of CC resumption in patients with witnessed arrest and initial rhythm of VF.