The document classifies antiarrhythmic drugs into four categories based on their mechanism of action: Class I drugs block sodium channels, Class II drugs block beta receptors, Class III drugs block potassium channels, and Class IV drugs block calcium channels. It describes the conduction pathways in the heart from the sinoatrial node through the atrioventricular node and Purkinje fibers to the ventricles, noting the atrioventricular node has a slower conduction velocity than other tissues. The document also provides a table summarizing the classification of antiarrhythmic drugs and an illustration of ion movement across cell membranes.

1. Antiarrhythmic Drugs-Overview
Dr. Fahad Azam
Shifa College of Medicine

2. Classification of antiarrhythmic drugs
Classification of drugs Mechanism of action
IA Na+ channel blocker
Qunidine, Procainamide
IB Na+ channel blocker
Lidocaine, Mexiletine
IC Na+ channel blocker
Flecainide, Propafenone
II Beta receptor blocker
Propanalol, Metoprolol
III K+ channel blocker
Amiodarone, Sotalol,
IV Ca+ channel blocker
Verapamil, Diltiazem, Nifedipine

3. Conduction Pathways and Velocity of Conduction
• Conduction Pathway:
SA node  atrial muscle  AV node  Purkinjee fibers  Ven. Muscle
delay
• Velocity:
– Fast conducting fiber:
• Purkinjee cell, Ventricular muscle, Atrial muscle
– Slow conducting fiber:
• AV node, SA node

4. Classification Mechanism of action
of drugs
IA Na+ channel blocker
Qunidine,
Procainamide
IB Na+ channel blocker
Lidocaine, Mexiletine
IC Na+ channel blocker
Flecainide,
Propafenone
II Beta receptor
blocker
Propanalol,
Metoprolol
III K+ channel blocker
Amiodarone, Sotalol,
IV Ca+ channel blocker
Verapamil, Diltiazem,
Nifedipine

5. Intracellular Extracellular
Na Leak
Na Pump
K Pump
K Diffusion