FIGURE 1.

Stylized examples of afterdepolarizations occurring in the single canine myocyte. Figure shows both membrane potentials and contraction for each situation. (Left) DAD (^∗) induced by the β-adrenergic agonist isoproterenol (ISO); (Middle) illustrates an EAD (#) induced by augmentation of the late sodium current, using ATX-II; (Right) illustrates that under certain conditions both types of afterdepolarizations can be seen in the same action potential. In this particular example, blockade of the potassium current, I_Ks, together with β-adrenergic stimulation are the proarrhythmic treatment and it can be seen that an early aftercontraction initiates prior to the upstroke of the EAD.