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Figure 2 Electrophysiological Recordings of Electrical Remodeling and Proarrhythmia in the CAVB Dog

Representative electrophysiological recordings obtained from an anesthetized chronic AV block (CAVB) dog before and after 4 weeks of electrical remodeling. (A) idioventricular rhythm at 0 and 4 weeks. (B) Torsades de pointes (TdP) arrhythmia after proarrhythmic challenge with dofetilide at 4 weeks. In all tracings, ECG leads II and AVR and left and right ventricular monophasic action potential (LV and RV MAP, respectively) recordings are shown. From top to bottom, RT, RR, QRS, duration of LV and RV MAP, and activation time (all ms) are indicated. Horizontal and vertical calibrations represent 1 s (paper speed 10 mm/s) and 1 mV for ECG recordings and 20 mV for MAP signals. Four weeks of AV block caused prolongation of RT and LV and RV MAP durations (A, right side). Dofetilide reproducibly induced TdP in this (B) and 6 other CAVB dogs. Abbreviations as in Figure 1.