Final answer:
Amiodarone affects the repolarization phase of the cardiac action potential by impeding the movement of K+ through voltage-gated K+ channels, slowing the return to the resting membrane potential.
Step-by-step explanation:
Potassium channel blockers such as amiodarone and procainamide are medications frequently used to manage cardiac dysrhythmias, which is an abnormal electrical activity in the heart. These drugs function by impeding the movement of K+ ions through voltage-gated K+ channels. This action could be expected to affect the repolarization phase of the action potential. More specifically, amiodarone would delay the repolarization phase, as this phase of the action potential depends on the efflux of K+ ions out of the cardiac muscle cells, which is necessary for the return of the membrane potential to its resting state after depolarization.