E-4031 is a methanesulfonanilide class III antiarrhythmic agent that prolongs cardiac action potential duration by blocking ERG K+ channels (IC50 = 29 nM)

At baseline, APD was longer in LQT1 than in LMC rabbits in LV apex and RV mid. Erythromycin and E-4031prolonged APD in LQT1 and LMC rabbits in all positions. However, erythromycin-induced percentaged APD prolongation related to baseline (%APD) was more pronounced in LQT1 at LV base-lateral and RV mid positions (100 μM, LQT1, +40.6 ± 9.7% vs. LMC, +24.1 ± 10.0%, p<0.05) and E-4031-induced %APD prolongation was more pronounced in LQT1 at LV base-lateral (0.01 μM, LQT1, +29.6 ± 10.6% vs. LMC, +19.1 ± 3.8%, p<0.05) and LV base-septal positions. Moreover, erythromycin significantly increased spatial APD dispersion only in LQT1 and increased triangulation only in LQT1 in LV base-septal and RV mid positions. Similarly, E-4031 increased triangulation only in LQT1 in LV apex and base-septal positions[1]

Hearts of adult female transgenic LQT1 and wild type littermate control (LMC) rabbits were Langendorff-perfused with increasing concentrations of HERG/IKr-blockers E-4031 (0.001-0.1 μM, n=9/7) and APD, APD dispersion, and triangulation were analyzed[1].