Improved diagnostic value of combined time and frequency domain analysis of the signal-averaged electrocardiogram after myocardial infarction

Background Time domain analysis (TD) of the signal-averaged electrocardiogram (SAECG) presents higher incidence of false positives in inferior myocardial infarction (MI), whereas spectral turbulence analysis (STA) suffers from higher incidence of false positives in anterior MI. We investigated the hypothesis that combined TD and ST (TD+STA) analysis of the SAECG could improve its predictive accuracy for major arrhythmic events (MAE) after MI. Methods Signal-averaged electrocardiograms were prospectively recorded 10.1 ± 2.6 days after acute MI in 602 patients. Time domain analysis and ST were performed using standard parameters and criteri for abnormality. For the combined TD+ST model, stepwise discriminant analysis was utilized to optimize prediction of MAE. Receiver operating characteristic curves were utilized to optimize cutoff values for each SAECG parameter separately, and also for the combined TD+ST model. Results During one-year follow-up period, 38 patients had MAE: 14 sustained ventricular tachycardia, 2 resuscitated ventricular fibrillation and 22 sudden cardiac deaths. The total predictive accuracy of combined TD+ST (89.9%) was significantly higher than TD (75.1%) or ST (77.6%). The negative predictive accuracy of all three analyses was high (98%). The positive predictive accuracy of TD (19.6%) or ST (18.3%) was quite low, and significantly improved to 35.8% by combined TD+ST analysis. The positive predictive accuracy of TD+ST improved to 51.2% in patients with left ventricular ejection fraction <40%. Conclusions Combined TD+ST analysis of the SAECG significantly improves its prognostic ability for MAE in post-MI patients compared with TD or ST analyzed separately.