Antiarrhythmics - Vaughan Williams Classification:
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Description

Antiarrhythmics - Vaughan Williams Classification:
CLASS 1 - Sodium Channel Blockers:
 • MOA: Block fast Na+ channels to reduce speed of ion conduction
 • ↓ slope of phase 0 to decrease rate and magnitude of depolarization
 • Divided into 3 categories based on Na+ channel blocking effects and AP duration:
    - CLASS 1A: Moderate Blockade, Intermediate Action, ↑ EFR & AP duration
    - CLASS 1B: Weak Blockade, Fast Action, ↓ EFR & AP duration
    - CLASS 1C: Strong Blockade, Slow Action,  ←→ EFR & AP duration
CLASS 2 - Beta Blockers:
 • MOA: Inhibit B.adrenergic activation (↓ cAMP and Ca++ current) causing ↓SA node and AV node activity (rate control)
 • ↓ slope of phase 4 to slow depolarization
 • ↑ PR interval to prolong AV node repolarization
CLASS 3 - Potassium Channel Blockers:
 • MOA: Block K+ channels (primarily) and block alpha & beta adrenergic receptors, and Ca & Na channels.
    - ↑ duration of phase 2 (↑ERP & ↑AP Duration)
    - ↑ QT interval (delays time repolarization)
CLASS 4 - Calcium Channel Blockers:
 • MOA: Block slow Ca++ channels to prevent Ca++ influx into cells (rate control).
    - ↓ slope of phase 0 and 4 to ↑ ERP (slow conduction velocity)
    - ↑ PR interval to prolong AV node repolarization
    - ↓ contraction force (negative inotropy)

ACCP Cardiology PRN @accpcardprn

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Contributed by

Dr. Gerald Diaz
@GeraldMD
Board Certified Internal Medicine Hospitalist, GrepMed Editor in Chief 🇵🇭 🇺🇸 - Sign up for an account to like, bookmark and upload images to contribute to our community platform. Follow us on IG:  https://www.instagram.com/grepmed/ | Twitter: https://twitter.com/grepmeded/
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