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Anti arrhythmics !!!

Anti arrhythmics !!!. Automaticity enhanced automaticity abnormal automaticity Triggered activity Early afterdepolarisation (EAD) Delayed afterdepolarisation (DAD) Re-entry. Arrhythmogenic mechanisms. Classification of the Anti- arrhythmics.

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Anti arrhythmics !!!

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  1. Anti arrhythmics!!!

  2. Automaticity • enhanced automaticity • abnormal automaticity • Triggered activity • Early afterdepolarisation (EAD) • Delayed afterdepolarisation (DAD) • Re-entry Arrhythmogenic mechanisms

  3. Classification of the Anti-arrhythmics Vaughan Williams EM. "Classification of antiarrhythmic drugs." 1970

  4. Delay depolarisation – fast Na+ channels 1 2 0 0 3 Transmembrane Potential mV -90 4 Quinidine - Class Ia

  5. 1 2 0 0 3 Transmembrane Potential mV -90 4 Blocks Na+ channels in actively depolarising cells/depolarised areas. Action potential is shortened. Lidocaine (Lignocaine) – Class Ib

  6. No change in action potential duration 1 2 0 0 3 Transmembrane Potential mV -90 4 Flecainide - Class Ic

  7. K+ channel blockers: Amiodarone, dronedarone Delay repolarisation – K+ channels 1 2 0 0 3 Transmembrane Potential mV -90 4 Amiodarone - Class III

  8. Ca2+ channels blockers: Verapamil, diltiazem Reduce amplitude and shorten Phase 2 – L-type Ca2+ channels 1 2 0 0 3 Transmembrane Potential mV -90 4 Verapamil - Class IV Reduce intracellular Ca2+ and thus negatively inotropic on myocytes

  9. Verapamil Effect on SA Node

  10. Summary

  11. Ivabradine • Selective If blocker – “funny channel” • Acts only on the SA node • Slows Na+ entry • Slower pacemaker potential Na+ K+ If Channel blockers Ivabradine

  12. Usually digoxin • Inhibits the Na+/K+ ATPase pump • Increased intracellular Na+ • Ca2+ exchanged for Na+ passively • Via Ca2+/Na+ exchangers that rely on Na+ concentration gradient • Thus cytoplasmic Ca2+ increased as less extruded • (Increases vagal drive – the heart slows down) K+ [Na+] low Cardiac Glycoside: Increased force of contraction and blocks AV node ATP→ADP [Na+] high Na+ Ca2+ Na+ Inhibited by concentration gradient Na+ increases as pump blocked

  13. Speeds up the heart rate • Acetylcholine receptors in the SA and AV nodes • Blocks the effects of acetylcholine (parasympathetic blockade) → blocks the “handbrake” so heart beats faster • Used for emergency treatment of bradycardia (slow heart rate) • Because of other Ach receptors in the body • S/E: dry mouth, urinary retention, dilated pupils Atropine

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