AMplitude Spectral Area (AMSA) is associated with one-year survival with good neurological outcome in out-of-hospital cardiac arrest

Background Patients resuscitated from Out-of-Hospital Cardiac Arrest (OHCA) with shockable rhythms are reported to have better survival rates. Amplitude spectral area (AMSA) of ventricular fibrillation (VF), a surrogate for the metabolic status of the myocardium, can predict shock success and return of spontaneous circulation (ROSC). There is minimal evidence regarding its role in predicting survival from OHCA, and the evidence that exists is limited to survival at discharge. Purpose To test the hypothesis that the first, the maximum, the minimum and the average values of AMSA are associated with one-year survival with good neurological outcome in OHCA patients. Methods All the OHCAs with at least one shockable rhythm, that occurred from January 2015 to December 2020 and collected from an Utstein-style database, were considered. AMSA values were calculated by retrospectively analyzing the data collected by the monitors/defibrillators used and by using a 2-second pre-shock ECG interval. The first, the maximum, the minimum and the average AMSA values during resuscitation were computed. Data were analyzed by using Cox regression analysis. Results 250 patients (84% male, median age 67 [57-77] years) with at least one computable AMSA value were included; 12% achieved ROSC and 9.4% survived at one year with good neurological outcome, defined as Cerebral Performance Category (CPC) ≤ 2. The first, the maximum, the minimum and the average values of AMSA were higher in patients alive one year after OHCA with CPC≤2 (first: 11.6 [9.9-14.7] vs 7.8 [5.1-11.8]; max: 15.4 [12-20] vs 9.9 [6.2-14.4]; min: 9.9 [8.5-12.2] vs 6.1 [4.3-9.6]; avg: 12.5 [10.7-15.2] vs 8.3 [5.5-12]; all p <0.01). These values showed similar areas under the curve of the receiver operating characteristic (ROC) curve for one-year survival with good neurological outcome (first: 0.77; max: 0.76; min: 0.78; avg: 0.78, p=ns). In univariable model, the survival probability with good neurological outcome was significantly lower in the first tertile (T1) of AMSA compared to the third one (T3; p<0.05; figure). In multivariable analysis, after correction for sex, presence of bystander CPR, age, EMS arrival time, witnessed status, OHCA location, the use of mechanical CPR and the total amount of epinephrine administrated, AMSA was significantly associated with probability of death or poor neurologic outcome [HR 0.5 (95%CI 0.3-0.9), p=0.03]. Conclusions This is the first study to evaluate the association between AMSA values and one-year survival with good neurological outcome. We found that AMSA is independently associated with one-year survival with­ good neurological outcome in OHCA patients and that the first, the maximum, the minimum and the average of AMSA values all have similar prediction power in survival rate with CPC≤2.