Figure 4.
Effect of dofetilide on the single cell action potential of different cell types. Black lines represent the baseline action potential of endocardial, midwall, epicardial, and Purkinje cells without drugs, yellow to red lines represent the modified action potential at drug concentrations of 1x, 5.7x, and 30x. By blocking the rapid delayed rectifier potassium current IKr, dofetilide prolongs the plateau of the action potential and increases the overall action potential duration. This effect increases with increasing concentration, from yellow to red. Beyond a critical concentration, endocardial and midwall cells experience early afterdepolarizations and become self-oscillatory, orange and red lines. Epicardial and Purkinje cells display no signs of early afterdepolarizations within the simulated concentration range.