Alternans-like phenomena due to filtering of electrocardiographic data

Sudden cardiac death (SCD) is the leading cause of cardiovascular mortality in industrialized countries. Repolarization alternans phenomena seem to provide a noninvasive marker for the risk of SCD caused by life threatening arrhythmias. Some definitions have been proposed in the literature in order to quantify the extend of alternans. There is, however, no standard procedure to quantify alternans. A computational investigation is used to show how high pass filtering, which is a commonly applied method to suppress base line oscillations of the ECG, may induce and modify repolarization alternans phenomena. It is concluded that this fact has to be considered if one undertakes studies analyzing T-wave alternans in patient data.