Potassium channel blockers (such as amiodarone and procainamide) are used to treat abnormal electrical activity of the heart. These drugs impede movement of K through voltage fated K channels. Which part of the action potential would you expect these drugs to most directly affect

repolarization  

Explanation:

Potassium channel blockers are drugs that interfere with the flow of potassium ions (K+) through potassium channels in cell membranes, thereby prolonging the duration of the action potential (repolarization phase). For example, amiodarone is a class III antiarrhythmic agent whose target is HERG human cardiac K+ channel. This drug (amiodarone) acts by prolonging the repolarization phase of the cardiac action potential.