Figure 6.

A, Circumflex coronary artery occlusion induced repolarization alternans, preceding ventricular fibrillation (VF). Alternans voltage and K_score estimated from body surface as well intracardiac right ventricular (RV), left ventricular (LV), and coronary sinus (CS) unipolar leads. The beginning of the occlusion is marked by a vertical line. B, One observes a significant increase of alternans voltage and K_score, for several minutes, preceding the onset of VF in both surface and LVCS leads. Red line indicates alternans voltage and K_score thresholds for the respective leads (N=17). VT/VF indicates ventricular tachycardia/ventricular fibrillation. * denotes presence of significant repolarization alternans, defined as at least 1 min of data with both alternans voltage and K_score greater than their respective thresholds, in at least one lead, in a 5 min window before the event.