Mechanism of torsades de pointes

The top panels A-F are examples of epicardial isochrone maps obtained from the surface of the anterior left ventricular (LV) wall and free wall of the right ventricle (RV) during an episode of quinidine-induced torsades de pointes. Each map corresponds to a QRS deflection of the surface ECG and simultaneous monophasic action potential (MAP). Early afterpotentials (EADs) result in triggered activity (panels A-C) which is followed by a long episode of spiral-like reentry (panels D-F). Panel C shows the first reentrant wave which is not stationary, but gradually shifts upward and to the right. This is associated with a gradual decrease in the QRS complex amplitude.