**Core Concept:** Dofetilide is a class III antiarrhythmic drug, which is used for the treatment of patients with atrial fibrillation, atrial flutter, and heart failure. Class III antiarrhythmic drugs work by prolonging the action potential duration in cardiac cells, thereby stabilizing the heart rate and reducing the risk of ventricular arrhythmias.

**Why the Correct Answer is Right:** Dofetilide belongs to the class of drugs known as selective potassium channel blockers. It inhibits the rapid delayed rectifier potassium current (IKr) in the heart, which prolongs the action potential duration in the atrial and ventricular myocytes. This leads to a decrease in the automaticity, excitability, and conduction velocity of the heart, ultimately stabilizing the heart rate and reducing the risk of ventricular arrhythmias.

**Why Each Wrong Option is Incorrect:**

A. **Option A**: This option is incorrect because Dofetilide is a selective potassium channel blocker, not a calcium channel blocker. Calcium channel blockers, such as verapamil and diltiazem, are used for different cardiovascular conditions, like hypertension and angina pectoris.

B. **Option B**: This option is incorrect because Dofetilide is a selective potassium channel blocker, not a beta-blocker. Beta-blockers, such as propranolol, are used for different cardiovascular conditions, like hypertension, angina pectoris, and heart failure.

C. **Option C**: This option is incorrect because Dofetilide is a selective potassium channel blocker, not a calcium antagonist. Calcium antagonists, such as nifedipine, are used for different cardiovascular conditions, like hypertension and angina pectoris.

D. **Option D**: This option is incorrect because Dofetilide is a selective potassium channel blocker, not a calcium antagonist. Calcium antagonists, such as verapamil and diltiazem, are used for different cardiovascular conditions, like hypertension and angina pectoris.

**Clinical Pearl / High-Yield Fact:** Antiarrhythmic drugs like Dofetilide are used in the management of atrial fibrillation and atrial flutter, as well as in the treatment of heart failure. They help stabilize the heart rate and reduce the risk of ventricular arrhythmias.