Final answer:
Potassium channel blockers like amiodarone and procainamide delay the repolarization phase of the cardiac action potential, thereby prolonging it and preventing arrhythmias.
Step-by-step explanation:
Potassium channel blockers, such as amiodarone and procainamide, obstruct the flow of potassium ions through voltage-gated K+ channels during the repolarization phase of the cardiac action potential. This prolongs the duration of the action potential and the refractory period. As a result, the heart’s electrical excitability is reduced, which can prevent abnormal rapid heart rhythms, or arrhythmias.
Specifically, these drugs affect the phase of repolarization after the peak of the action potential, where K+ channels typically open to allow K+ ions to exit the cell, thereby restoring the cell to its resting potential. By inhibiting these channels, repolarization is delayed, leading to a longer action potential duration.