Predictive value of amplitude spectrum area of ventricular fibrillation waveform in patients with acute or previous myocardial infarction in out-of-hospital cardiac arrest

Background Amplitude spectrum area (AMSA) of ventricular fibrillation (VF) has been associated with survival from out-of-hospital cardiac arrest (OHCA). Ischemic heart disease has been shown to change AMSA. We studied whether the association between AMSA and survival changes with acute ST-elevation myocardial infarction (STEMI) as cause of the OHCA and/or previous MI. Methods Multivariate logistic regression with log-transformed AMSA of first artifact-free VF segment was used to assess the association between AMSA and survival, according to presence of STEMI or previous MI, adjusting for resuscitation characteristics, medication use and comorbidities. Results Of 716 VF-patients included from an OHCA-registry in the Netherlands, 328 (46%) had STEMI as cause of OHCA. Previous MI was present in 186 (26%) patients. Survival was 66%; neither previous MI (P = 0.11) nor STEMI (P = 0.78) altered survival. AMSA was a predictor of survival (ORadj: 1.52, 95%-CI: 1.28–1.82). STEMI was associated with lower AMSA (8.4 mV-Hz [3.7–16.5] vs. 12.3 mV-Hz [5.6–23.0]; P < 0.001), but previous MI was not (9.5 mV-Hz [3.9–18.0] vs 10.6 mV-Hz [4.6–19.3]; P = 0.27). When predicting survival, there was no interaction between previous MI and AMSA (P = 0.14). STEMI and AMSA had a significant interaction (P = 0.002), whereby AMSA was no longer a predictor of survival (ORadj: 1.03, 95%-CI: 0.77–1.37) in STEMI-patients. In patients without STEMI, higher AMSA was associated with higher survival rates (ORadj: 1.80, 95%-CI: 1.39–2.35). Conclusions The prognostic value of AMSA is altered by the presence of STEMI: while AMSA has strong predictive value in patients without STEMI, AMSA is not a predictor of survival in STEMI-patients.