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Figure 1 Transmembrane action potentials simultaneously recorded from the epicardial (Epi), midmyocardial (M), and endocardial (Endo) regions and a transmural electrocardiogram (ECG) at basic cycle length of 2,000 ms under each study condition. (A) Control. (B) E-4031 (1µmol/l). (C) Chromanol 293B (10µmol/l). (D) 293B + E-4031 (acquired long QT syndrome [LQTS] condition). (E) Epinephrine infusion (Epine: 0.5µmol/l) under acquired LQTS condition. (F) Addition of verapamil (Verap) 2.5 µmol/l under acquired LQTS condition. (G) Further addition of Epine in the continued presence of Verap under acquired LQTS condition. Numbers at bottom of each ECG denote transmural dispersion of repolarization (ms).