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24 Cards in this Set
- Front
- Back
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Name the Class IA antiarrhythmics
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Disopyramid
Quinidine Procainamide |
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Name the Class IB antiarrhythmics
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Lidocaine
Tocainide Mexiletine Phenytoin |
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Name the Class IC antiarrhythmics
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Flecainide
Propafenone |
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In general, how does a Class I antiarrhythmic change a myocyte's depolarization?
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Blocks Na+ channels. This results in a decreased Phase 0 slope and increased threshold for firing.
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How does the myocyte's depolarization change with Class IA antiarrhythmics?
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Decreases phase 0 slope (some)
Prolonged action potential (block K+ channels too!) Long effective refractory period and QT interval |
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How does the myocyte's depolarization change with Class IB antiarrhythmics?
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Decreases phase 0 slope (a little)
Shortened action potential |
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How does the myocyte's depolarization change with Class IC antiarrhythmics?
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Decreases phase 0 slope (a lot)
No change in action potential |
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What are Class IA antiarrhythmics used for?
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Effective in atria and ventricles
Reentrant and ectopic SVT V-tach |
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What are Class IB antiarrhythmics used for?
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Best post-MI!
Preferentially affect ischemic or depolarized Purkinje or ventricular tissue Useful for acute ventricular arrhythmias (especially post-MI) and in digitalis-induced arrhythmias. |
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What are Class IC antiarrhythmics used for?
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Worst post-MI!
Can only be used in patients without structural abnormalities Last resort in refractory tachyarrhythmias |
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How do Class II antiarrhythmics have their effects?
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Work best on AV node and on cells with automaticity
Suppress abnormal pacemakers by decreasing the slope of phase 4 Slowed conduction through the AV node can cause an increased PR interval |
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Name the Class III antiarrhythmics?
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K - (potassium)
I - Ibutilide S - Sotalol B - Bretylium A - Amiodarone D - Dofetilide |
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What is the mechanism of Class III antiarrhythmic's action?
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Block the K+ channels, delaying repolarization.
Increases action potential duration, effective refractory period, and QT interval |
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Amiodarone is a class III antiarrhythmic. How does it work?
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Blocks K+ channels... AND...
alters the lipid membrane, leading to class I, II, III, and IV effects. |
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What must be done when a patient is started on Amiodarone?
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Check PFTs, LFTs, and TFTs regularly
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What are the side effects of Amiodarone?
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Pulmonary fibrosis
Hepatotoxicity Hypo/hyperthyroidism Corneal and skin deposits Photodermatitis Cardiovascular effects (bradycardia, CHF, heart block) |
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Name the Class IV antiarrhythmics
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Verapamil
Diltiazem (non-dihydropyridines) |
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What cells do Class IV antiarrhythmics work on?
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AV node and cells with automaticity
Most selective for rapidly depolarizing myocytes in the nodes/atria |
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How is a myocyte affected by a Class IV antiarrhythmic?
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Decreased conductance velocity
Increased PR interval Increased effective refractory period |
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What are Class IV antiarrhythmics used for?
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Prevention of nodal arrhythmias
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How does adenosine work?
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Opens K+ channels, which hyperpolarizes the cell and inhibits Ca2+ influx at the SA and AV nodes.
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What is adenosine used for?
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Termination of supraventricular tachycardia
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What drug are the effects of adenosine blocked by?
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Theophylline (asthma drug)
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When is Mg2+ used with arrhythmias?
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Effective against torsades and digoxin toxicity
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