**Question:** Most cardiostable among the following is

A. Amiodarone
B. Metoprolol
C. Sotalol
D. Diltiazem

**Core Concept:** Cardiostability is a term used to describe the ability of a drug to prevent or treat arrhythmias without causing bradycardia or worsening heart failure.

**Why the Correct Answer is Right:**

Amiodarone is a highly effective antiarrhythmic drug with a broad spectrum of activity against various arrhythmias, including supraventricular and ventricular tachyarrhythmias. It is a class III antiarrhythmic agent (lengthens the action potential) and is also a class Ic agent (blocks sodium channels and causes afterdepolarizations). Amiodarone has a relatively low risk of causing bradycardia and heart failure compared to other antiarrhythmic drugs.

**Why Each Wrong Option is Incorrect:**

B. Metoprolol (beta-blocker) is a cardioselective agent, meaning it preferentially blocks beta-1 receptors. While it can be useful in some cases (e.g., angina, hypertension), its antiarrhythmic properties are relatively weak compared to amiodarone.

C. Sotalol (beta-blocker) is also a beta-blocker, but like metoprolol, its antiarrhythmic properties are not as potent as amiodarone. Sotalol has class III properties (lengthens action potential), but its beta-blocking properties overshadow its antiarrhythmic effects.

D. Diltiazem (calcium channel blocker) is primarily used for its antihypertensive and antianginal properties. Its antiarrhythmic properties are relatively weak, making it less cardiostable compared to amiodarone.

**Clinical Pearl:** Amiodarone is a versatile antiarrhythmic drug with potent antiarrhythmic properties, low risk of bradycardia, and heart failure. It is a valuable tool in managing complex arrhythmias and is often used as a first-line choice for drug-resistant atrial fibrillation or ventricular tachycardia.

**Correct Answer:** Amiodarone (Class IC)