Final answer:
Calcium channel blockers in Class IV antiarrhythmics prevent the influx of calcium ions through heart muscle channels, decreasing heart rate and the strength of heart contractions, and thus treating hypertension and arrhythmias. Potassium channel blockers, on the other hand, primarily affect the repolarization phase of the cardiac action potential.
Step-by-step explanation:
The mechanism of action of calcium channel blockers, specifically those classified as Class IV antiarrhythmics, involves the inhibition of the influx of calcium ions through the slow calcium channels in the heart muscle. This effect leads to a reduction in the strength of cardiac contractions (negative inotropic effect) and a prolongation of the cardiac action potential, which translates into a slowed heart rate (HR) and decreased likelihood of abnormal heart rhythms or cardiac dysrhythmia. Calcium channel blockers, such as amlodipine, verapamil, and diltiazem, work by binding to these channels, thus impeding the inward movement of calcium ions, which play a critical role in the electrical signaling and muscular contraction of the heart. By doing so, these drugs reduce myocardial oxygen demand and can treat conditions such as hypertension, angina pectoris, and certain types of arrhythmias. Meanwhile, potassium channel blockers like amiodarone and procainamide target the movement of potassium ions through voltage-gated K+ channels, primarily affecting the repolarization phase of the action potential, which can lead to prolonged repolarization and prevention of tachyarrhythmias.