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Pharmacology I

Pharmacology I. Drugs Used to Treat Arrhythmias. Arrhythmias Needing Treatment:. Atrial Fibrillation/Flutter (AF) Supraventricular Tachycardia (SVT) Ventricular Tachycardia (VT). Drug Classifications: Ia. Used For: Used to treat SVT, AF, VT

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Pharmacology I

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  1. Pharmacology I Drugs Used to Treat Arrhythmias

  2. Arrhythmias Needing Treatment: • Atrial Fibrillation/Flutter (AF) • Supraventricular Tachycardia (SVT) • Ventricular Tachycardia (VT)

  3. Drug Classifications: Ia • Used For: Used to treat SVT, AF, VT • Mechanism: Blocks Na+ Channels (slows action potential) • ECG Effects: QRS and Q-T interval • Examples: Quinidine (Quinora), Procainamide (Pronestyl), Disopyramide (Norpace)

  4. Other Effects: Class Ia • Slight increase in resting HR • Causes peripheral vasodilation • Which decreases TPR • Which decreases BP • Supresses PVC’s • Quinidine Toxicity: • Prolonged Q-T: Causes polymorphic VT –”Torsades de Pointe” • Syncope

  5. Exercise Capacity: Class Ia Drugs (ACSM Manual) • No Change in Exercise Tolerance • Exercise ECG: • Prolonged Q-T intervals • “False Positive” ST changes • Exercise HR/BP unaffected

  6. Drug Classification: Ib • Used For: VT • Mechanism: Blocks Na+ channels • ECG Effects: Decreased Q-T Interval • Examples: Lidocaine (Xylocaine), Tocainide (Tonocard), Phenytoin (Dilantin)

  7. Other Effects: Class Ib • Increases Preload • Decreases Contractility (Reduces Ejection Fraction) • Lidocaine Toxicity: May reduce CO and BP excessively • Nevertheless: Well tolerated by CHF patients • NO Significant Exercise Effects

  8. Drug Classification: II • Used For: SVT and AF • Mechanism: Blocks Beta receptors for SNS and Adrenal stimulation • ECG Effects: Prolong P-R interval and reduce HR • Examples - Beta Adrenergic Blockers: Inderal, Lopressor, Corzide

  9. Other Effects: ß-Blockers • Reduce risk of prolonged Q-T intervals • Reduces all types of tachycardias • Adverse Effects: • May disrupt glucose control and Hypoglycemic symptoms in Diabetics • May exacerbate Cardiac failure in CHF • Sudden Withdrawal is DANGEROUS

  10. Exercise Effects: II • Very Common Cardiac Drugs • Exercise Tolerance: • Improved in patients with angina • Decreased in non-anginal patients • Exercise ECG: HR and ischemic changes • Hemodynamics: HR and BP at rest and Exercise

  11. Drug Classification: III • Used For: SVT, VT and AF • Mechanisms: Na+/K+ channel blocker and many others • ECG Effect: Prolong Q-T • Examples: NAPA, Amiodarone

  12. Other Effects: III • Slows HR • Decreases TPR (BP too) • Increases Coronary Artery blood flow • Slightly reduces contractility • ADVERSE: symptomatic sinus brady, AV blocks, sinus arrest

  13. Exercise Effects: III • Exercise Tolerance: No change • Exercise ECG: Decreased HR • Hemodynamics: Decreased HR

  14. And Finally: Class IV

  15. Drug Classification: IV • Used For: SVT and AF • Mechanisms: Ca++ Channel Blockers • ECG Effects: Decrease HR and Increase PR- Interval • Examples: Verapamil (Calan), Diltiazem (Cardizem)

  16. Other Effects: Class IV • Used more for other cardiac effects – especially hypertension and ischemia • Uncontrolled AF: Reduces Ventricular rate in AF (>100) • Adverse Effects: Hypotension, bradycardia and rarely, ventricular asystole

  17. Exercise Effects: IV • Exercise Tolerance: Improved in patients with angina • Exercise ECG: Reduced HR and ischemic ST changes • Hemodynamics: Reduced blood pressure

  18. What About Digitalis?

  19. Cardiac Glycosides: Nightshade plant… • Used For: SVT and AF • Mechanisms: Inhibits Na+/K+-ATPase activity (maintains resting potential…) • ECG Effects: QRS and Q-T • Examples: Lanoxin

  20. Other Effects: Digitalis • Most commonly used to treat CHF • Great Risk of Toxicity: Serum levels monitored closely • Tachyarrhythmias • Anorexia • “Halo Vision” when looking at lights

  21. Exercise And Digitalis: • Exercise Tolerance: Improved in patients with CHF or AF • ECG Effects: “Scooping” ST segment • Hemodynamics: Some decrease in patients with AF /CHF

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