Role of repolarizaion duration and transmural dispersion of repolarization for occurrence of torsade de pointes

    LIU Nian, ZHOU Qiang, RUAN Yanª²Fei, PU Jun, ZHANG Cunª²Tai

    Department of Vasocardiology, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430030, China

    ¡¾Abstract¡¿ AIM: To investigate the role of repolarization duration and transmural dispersion of repolarization (TDR) for the occurrence of torsade de pointes (TdP). METHODS: Thirtyª²two rabbits were divided into four groups: lowª²concentration sotalol group (10 ¦Ìmol/L), highª²concentration sotalol group (100 ¦Ìmol/L), lowª²concentration quinidine group (1 ¦Ìmol/L) and highª²concentration quinidine group (10 ¦Ìmol/L). With the monophasic action potential (MAP) recording technique, MAP of epicardium, midmyocardium and endocardium were simultaneously recorded by specially designed plungeª²needle electrodes across the left ventricular free wall of rabbit hearts purfused by Langendorff method. Monophasic action potential duration (MAPD), TDR, early afterdepolarization (EAD) and TdP were observed. RESULTS: Sotalol induced concentrationª²dependent prolongation of MAPD in all the three layers of ventricular myocardium and TDR. Eight rabbits developed EAD and six developed TdP in highª²concentration sotalol group. Only four developed EAD in lowª²concentration sotalol group whereas no rabbit developed TdP. Quinidine induced concentrationª²dependent prolongation of MAPD in all the three layers of ventricular myocardium and reverse concentrationª²dependent increase of TDR. Seven rabbits developed EAD and one developed TdP in highª²concentration quinidine group. Six developed EAD and four developed TdP in lowª²concentration quinidine group. CONCLUSION: The risk for the development of TdP is chiefly related to the increase in TDR rather than the prolongation of the repolarization duration. ......