Association of Electrocardiographic Repolarization Variability and Atrial Depolarization Variability with the Risk of Sudden Cardiac Death and with Myocardial Fibrosis.

The aims of the present research were to assess the association of temporal variability of electrocardiographic spatial heterogeneity of repolarization and the association of temporal variability of electrocardiographic spatial heterogeneity of atrial depolarization, specifically in relation to heart rate variability (HRV) with the risk of sudden cardiac death (SCD). Additionally, the relationship between spatial heterogeneity of electrocardiographic repolarization and spatial heterogeneity of atrial depolarization with arrhythmic substrate represented by ventricular fibrosis was evaluated.
The standard deviation of T-wave heterogeneity (TWH-SD) was significantly higher when analyzed from five consecutive beats of the standard 12-lead ECGs in 200 SCD victims with autopsy-confirmed coronary artery disease (CAD) than in 200 age- and sex-matched controls with angiographically confirmed CAD. Temporal variability of spatial heterogeneity of atrial depolarization analyzed from five consecutive beats of the standard 12-lead ECG in 1236 patients with CAD, specifically in relation to 24 hour HRV, was significantly associated with the risk of SCD/sudden cardiac arrest (SCA) even after relevant adjustments, but not with non- sudden cardiac death or non-cardiac death. Spatial heterogeneity of ventricular repolarization and spatial heterogeneity of atrial depolarization analyzed from the standard 12-lead electrocardiogram of 378 victims of unexpected SCD were significantly associated with ventricular fibrosis.
The present observations show that increased short-term variability of electrocardiographic repolarization heterogeneity is associated with SCD in patients with CAD and that temporospatial heterogeneity of electrocardiographic atrial depolarization, specifically when combined with cardiac autonomic regulation, independently predicts the risk of SCD in CAD patients. Increased electrocardiographic spatial heterogeneity of repolarization and spatial heterogeneity of atrial depolarization are associated with arrhythmic substrate represented by ventricular fibrosis partly explaining the mechanism behind their prognostic significance.

Keywords: atrial depolarization, cardiac autonomic regulation, electrocardiography, myocardial fibrosis, P-wave morphology, P-wave, sudden cardiac death, temporal variability, T-wave morphology, T-wave, ventricular repolarization