Final answer:
Potassium channel blockers, such as amiodarone and procainamide, affect the repolarization phase of the action potential by inhibiting the movement of K+ ions through voltage-gated channels in cardiac cells.
Step-by-step explanation:
Potassium channel blockers, such as amiodarone and procainamide, affect the repolarization phase of the action potential. These drugs inhibit the movement of K+ through voltage-gated K+ channels in the cardiac cells. By blocking potassium channels, these medications prolong the action potential duration, which can help regulate abnormal electrical activity in the heart.