Figure 4. K_V7.1 and K_V11.1 are crucial for determining the length of the cardiac action potential.

a, Illustration of ventricular action potential (AP) and electrocardiogram (ECG) showing effects of Long- and Short-QT syndrome as well as pharmacological modulators of K_V7.1 (IKs) or K_V11.1 (hERG) on AP duration and length of QT interval. Inhibition of K_V7.1 and K_V11.1 produces prolongation of ventricular AP duration which is similar to what occurs in acquired or hereditary Long QT syndrome. Activators of K_V7.1 or K_V11.1 reduce the duration of cardiac action potential which is manifested as a shorter QT interval b, K_V7.1 inhibitors: (23), azimilide (Procter & Gamble)¹²⁸,¹²⁹; (24), HMR1556 (Sanofi-Aventis)¹³⁴; (25), L768,673 (Merck)¹³⁸. Azimilide has been shown to reduce atrial fibrillation (AF) in clinical trials¹²⁸,¹²⁹, while HMR1556 and L768,673 are effective in dog models of AF. K_V7.1 activators: (26), niflumic acid¹³⁹; (27), mefenamic acid¹³⁹; (28), L384,373 (Merck)¹⁴¹.