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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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Presentation Transcript
arrhythmogenic mechanisms

Automaticity

    • enhanced automaticity
    • abnormal automaticity
  • Triggered activity
    • Early afterdepolarisation (EAD)
    • Delayed afterdepolarisation (DAD)
  • Re-entry
Arrhythmogenic mechanisms
classification of the anti arrhythmics
Classification of the Anti-arrhythmics

Vaughan Williams EM. "Classification of antiarrhythmic drugs." 1970

lidocaine lignocaine class ib

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
amiodarone class iii

K+ channel blockers: Amiodarone, dronedarone

Delay repolarisation – K+ channels

1

2

0

0

3

Transmembrane Potential mV

-90

4

Amiodarone - Class III
verapamil class iv

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

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

Na+

K+

If Channel blockers

Ivabradine

cardiac glycoside increased force of contraction and blocks av node
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

atropine
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