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20 Cards in this Set
- Front
- Back
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What is the mechanism of Class I Anti Arrhythmics?
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Block the fast Na channel responsible for phase 0 depolarization.
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What is the mechanism of Class II Anti Arrhythmics?
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Beta adrenergic receptor blockers
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What is the mechanism of Class III Anti Arrhythmics?
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Prolongers of the Action Potential without effecting initial phase 0 depolarization (i.e. usually outward K blockers).
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What is the mechanism of Class IV Anti Arrhythmics?
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Block Slow L Type Calcium Channels
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Describe 2 mechanistic ways Antiarrhythmics treat increased automaticity.
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1. prolong phase 4 depolarization; 2. increase the refractory period
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Describe 2 mechanistic ways Antiarrhythmics treat reentrant pathways.
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1. increase tissue refractory period; 2. na channel blockade
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Describe Class IA's effect on Na channel. Usefulness?
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Increased threshold, moderate Na channel block. Has little effect on SA node so good for increased automaticity and prolongs refractory period so good for reentry circuits.
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What are Class IA's effect on EKG?
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Prolonged QRS and QT
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List 3 Class IA Drugs. For each list common side effects.
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Quinidine (oral only, anitcholinergic, hypotension);
Procainamide (can be IV, beware NAPA, SLE like); Disopyramide (oral,no dig/GI, > anticholinergic, > -inotropic effect) |
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Why is quinidine and digoxin a risky mix?
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Quinidine raises blood digoxin levels by decreasing body's clearance and volume of distribution of the later.
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Describe Class IB's effect on Na channel. Usefulness?
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Shortens the Action Potential duration and refractory period. This is effect is more pronounced leading to blockade in ischemic cells. Ventricular arrhytmias with little atrial effect.
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List 4 Class IB Drugs and their relavant side effects.
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Lidocaine (IV only, CNS);
Tocainide (oral, CNS/GI, agranulocytosis); Mexiletine (oral, CNS/GI); Diphenylhydantoin (antiseizure,IV/oral, CNS/GI) |
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Describe Class IC's effect on Na channel. What is the problem with this class?
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Most potent Na channel blocker. Can increase mortalitiy with underlying heart abnormalites!
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List 2 Class IC Drugs and their relevant side effects.
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Flecinide (oral, aggravation of CHF/V Arr);
Propafenoen (weak Beta adrenergic block) |
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Common EKG finding in Class II Drugs.
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prolonged PR interval due to prolonged AV nodal conduction.
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What are the clinical uses of Beta blocker (Class II) antiarrhytmics?
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Tachyarrhytmias (excess catecholamines); atrial flutter and fibrillation; supraventricular arrhytmias
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Amiodarone is a Class III Drug. What is the relevant action and side effects of this drug?
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Amiodarone (many effects, many adverse reactions, VD, -Inotrope, ~60 day elimination, pulmonary toxicity, thyroid dysf(x),GI)
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List 5 Class III Drugs.
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Amiodarone, Sotalol, Bretylium tosylate (IV), Ibutilide (IV, atrial flutter conversion), Dofetilide (oral, atrial flutter conversion)
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List 2 common Class IV Drugs.
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Verapamil, Diltiazem; CCBs so most potent in SA & AV nodes
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What is the most efective drug for the rapid termination of reentrant PSVT?
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Adenosine
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