A simulation study of Torsade de Pointes with M cells

Recent studies have reported the relation between Torsade de Pointes (TdP) and midmyocardial (M) cell function associated with long QT syndrome. To in vestigate this relation, we conducted a simulation study with a three-dimen sional (3D) heart model incorporating M cells in the anterolateral areas of the model. Parameters of premature cycle-length dependent shortening of ac tion potential duration (APD) and conduction velocity for the M cells were adjusted to induce tachyarrhythmias of TdP type. Under a basic pacing cycle length of 1,000 msec at the sinus node, four successive premature beats of 160-ms interval were generated 300 ms after the first sinus pacing. Settin g lower conduction velocity and longer APD to M cells induced sustained TdP -like tachyarrhythmia resembling ECG findings. TdP could not be induced wit hout the presence of M cells. This study suggests that TdP might be caused by reentry around M cells and dispersive refractory areas due to prolonged APD and slow conduction velocity.