When and Where Does the Reentry Start in Long-QT Syndrome? - A Computer Simulation Study

Reentry is the main form of arrhythmia. To know when and where the reentry starts in Long QT Syndromes (LQTS) and its relation with M cells distribution, the Luo-Rudy dynamic ionic model (LRdOO) of the mammalian ventricular action potential (AP) was used in a two dimensional transmural tissue sheets simulation. LQTS was simulated by reducing the membrane conductance of I_Ks for LQT1 and I_Kr for LQT2, and by altering the steady-state inactivation of the fast sodium current I_Na for LQT3. The endocardium was paced 10 times at a constant basic cycle length (BCL) of 500 ms (S1), and following a 2000 ms pause, a S2 stimulus was applied, or also a S3 stimulus was applied. The simulation was processed by changing shape, size and position of M cell domain, and S2S3 interval. We found that pause induced early after depolarization (EAD) started reentry near the boundary between endocardial domain and M cells domain. Only S3 stimulus that located in vulnerable windows could form reentry. The started position of the reentry depended upon the distribution of island of M cells and the position of extrasystole.