Anti-arrhythmic

Anti-arrhythmic Drugs

Anti-arrhythmic drugs are a class of pharmaceuticals used to treat and prevent cardiac arrhythmias, which are irregular heartbeats that can lead to serious complications such as stroke or heart failure. These drugs work by modifying the electrical impulses in the heart, thereby restoring normal rhythm and improving cardiac function.

Classification

Anti-arrhythmic drugs are classified into four main classes based on the Vaughan Williams classification system:

Class I

Class I anti-arrhythmics are sodium channel blockers. They are further subdivided into three categories:

• Class IA - These drugs, such as quinidine, procainamide, and disopyramide, slow conduction and prolong repolarization.
• Class IB - Drugs like lidocaine and mexiletine shorten repolarization and are used primarily for ventricular arrhythmias.
• Class IC - These include flecainide and propafenone, which markedly slow conduction with little effect on repolarization.

Class II

Class II anti-arrhythmics are beta blockers, such as propranolol, metoprolol, and atenolol. They work by blocking the effects of adrenaline on the heart, reducing heart rate and contractility.

Class III

Class III drugs are potassium channel blockers, which prolong repolarization. Examples include amiodarone, sotalol, and dofetilide. These are used for both atrial and ventricular arrhythmias.

Class IV

Class IV anti-arrhythmics are calcium channel blockers, such as verapamil and diltiazem. They are effective in treating supraventricular arrhythmias by slowing conduction through the atrioventricular node.

Mechanism of Action

Anti-arrhythmic drugs work by altering the cardiac action potential, which is the electrical signal that triggers heart muscle contraction. Each class of drugs affects different ion channels or receptors in the heart, leading to changes in the duration and conduction of electrical impulses.

Indications

These drugs are indicated for various types of arrhythmias, including:

• Atrial fibrillation
• Atrial flutter
• Ventricular tachycardia
• Ventricular fibrillation
• Supraventricular tachycardia

Side Effects

Anti-arrhythmic drugs can have significant side effects, including:

• Proarrhythmia (induction of new arrhythmias)
• Hypotension
• Bradycardia
• Torsades de Pointes (a specific type of ventricular tachycardia)
• Pulmonary toxicity (especially with amiodarone)

Also see

• Cardiac electrophysiology
• Electrocardiogram
• Heart block
• Pacemaker

Cardiovascular disease A-Z

Most common cardiac diseases

• Cardiac arrhythmia‎
• Cardiogenetic disorders‎
• Cardiomegaly‎
• Cardiomyopathy‎
• Cardiopulmonary resuscitation‎
• Chronic rheumatic heart diseases‎
• Congenital heart defects‎
• Heart neoplasia‎
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• Pericardial disorders
• Syndromes affecting the heart‎
• Valvular heart disease‎

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A

• Accelerated idioventricular rhythm
• Acute decompensated heart failure
• Arteriosclerotic heart disease
• Athletic heart syndrome
• Atrial flutter
• Atrioventricular fistula
• Cardiovascular disease in Australia
• Autoimmune heart disease

B

• Brown atrophy of the heart

C

• Ebb Cade
• Cardiac allograft vasculopathy
• Cardiac amyloidosis
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• Cardiogenic shock
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D

• Duke Treadmill Score
• Duroziez's disease

E

• Eisenmenger's syndrome
• Embryocardia
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• Eosinophilic myocarditis

H

• Heart attack
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• Heart to Heart (1949 film)
• High-output heart failure
• Hyperdynamic precordium

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I

• Idiopathic giant-cell myocarditis
• Interventricular dyssynchrony
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• Isolated atrial amyloidosis

K

• Keshan disease

L

• Loeffler endocarditis

M

• Mydicar
• Myocardial bridge
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N

• Nonbacterial thrombotic endocarditis

O

• OLR1
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P

• Papillary fibroelastoma
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• Pulmonary vein stenosis

R

• Right axis deviation
• Roemheld syndrome

S

• Saturated fat and cardiovascular disease
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T

• Traumatic cardiac arrest

V

• Ventricular aneurysm
• Vibroacoustic disease
• Viral cardiomyopathy

W

• Waon therapy