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Vc premature ventricular contraction 1 pvchr increased

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Unformatted text preview: erone directly induces myopathy – Aldosterone blocks reuptake epi/norepi so induces symp. arrhy. Phosphodiesterase Inhibitors (amrinone & milrinone) – Positive inotropic, dilates veins (less return) – Dilates arteries (decreases afterload) – Not supported by follow-up studies – Too many cautions but try short term Antiarrhythmics (or Antiarrhythmics Antidysrhythmic drugs) • Arrhythmia - any disorder of rate or conduction of electrical impulses – P.V.C. - premature ventricular contraction • 1 PVC/Hr increased mortality risk • 10/Hr see 20% mortality the first year • Highly lethal arrhythmias have – 80% mortality in the first year if not treated – 50% mortality with treatment • Meds are dangerous with multiple side effects • Implantable defibrillators an option Quinidine Quinidine Prototype antiarrhythmic drug – Originally for malaria – Used less frequently than digitalis for arrhythmias Mechanisms of Action An Overview • Chiefly a cardiac depressant – Explains therapeutic effects • Also anticholinergic – Explains negative effects Mechanism of Action Mechanism • Cardiac depressant – Decreased excitability, conduction velocity, and contractility – More effective on His & Purkinje than SA node. – Prolongs effective refractory period • Anticholinergic (atropine-like) action - AV node – Prevents cardiac slowing with muscarinic drugs – May be hazard when used to treat flutter or fibrillation • Atrial flutter may be transmitted to ventricles – Solution: Often used after digitalis because digitalis does inhibit conduction through A-V node. Therapeutic Uses Therapeutic • Atrial fibrillation - converts to normal sinus rhythm – hospital setting – electrical conversion more commonly used than drug – sometimes used to prevent reoccurrence of fibrillation • Atrial flutter - used if digitalis fails to work • Ventricular tachycardia – Common complication of myocardial infarction – Electroshock – implantable defibrillators – Lidocaine used in hospital if episodes repeatedly occur • Premature systoles (P.V.C.) – Usually only treat if think will lead to more serious arrhythmias (tachycardia, flutter, fibrillation) Side or Toxic Effects Side Antiarrhythmics • Cinchonism (quinidine from cinchona bark) – Relate to Malaria treatment – Aspirin • Mild to Moderate Symptoms – – – – GI -nausea ,vomiting, diarrhea, abdominal pain Ears -ringing , decreased hearing Eyes -blurr...
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