Term
| What are the classes of Antiarrhythmic Drugs? |
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Definition
Class Ia, Ib, Ic
Class II
Class III
Class IV |
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Term
| What is the general mechanism of Class Ia antiarrhythmics? |
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Definition
Na+ Channel Blockade
Moderately blocks phase 0 upstroke rate
Prolongs repolarization
Ex. Qunidine, Procainamide and Disopyramide |
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Term
| What is the general mechanism of action of Class Ib antiarrhytmic drugs? |
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Definition
Mild block of Na+ channel
Mild decrease in phase 0 upstroke rate
Shorten repolarization
Ex. Lidocain, Tocainide, Mexiletine and Phenytoin |
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Term
| What is the general mechanism of action of Class Ic antiarrhythmic drugs? |
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Definition
Marked Na+ Channel Blockade
Marked decrease in phase 0 upstroke rate
-no change in repolarization
Ex. Flecainide, Propafenone |
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Term
| What is the general mechanism of action of Class II antiarrhytmic drugs? |
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Definition
Class II are the Beta-Blocking agents.
Propanolol, Esmolol, Metaprolol and many more.
*all end in "ol"* |
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Term
| What is the general mechanism of action of Class III antiarrhytmic drugs? |
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Definition
Class III antiarrythmics are K+ channel blocking agents.
Marked prolongation of repolarization.
Ex. Amiodarone, Bretylium, Sotolol |
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Term
| What is the general mechanism of action of Class IV antiarrhytmic drugs? |
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Definition
Class IV antiarrhythmic drugs are Ca2+ channel blocking agents.
Ex. Verapamil and Dilitazem |
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Term
| What are the main cardiac effects of Class IA antiarrythmic drugs? |
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Definition
1. Prolong QRS wave (decrease slope of phase 0)
2. Prolong ventricular repolarization (inc. Phad 1-3 of RP)
3. Prolong QT interval
4. decrease automaticity of slow and fast fibers
5. initial anticholinergic effects at SA/AV nodes |
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Term
| What are the main toxicities of Class IA antiarrythmic drugs? |
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Definition
1. Widening of QRS may lead to ventricular tachycardia
2. Torsades de Points
-proarrhythmia
-caused by drugs that prolong QT
-can lead to tachychardia and syncope (fainting) |
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Term
| What are the main clinical indicatoins for use of Class IA antiarrythmic drugs? |
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Definition
1. SVT - Supra-ventricular tachychardia arrhythmias
ex.) atrial flutter or fibrillation |
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Term
| What is the drug of choice for the Class IA antiarrythmic drugs? |
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Definition
| Qunidine, Procainamide and Disopyramide |
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Term
| What are the main cardiac effects of Class IB antiarrythmic drugs? |
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Definition
1. Shortens QT interval
-slight decrease in slope of phase 0
2. Decreases ventricular automaticity
-especially in ischemic cardiocytes |
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Term
| What are the toxicities of Class IB antiarrythmic drugs? |
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Definition
1. Dose related CNS effects
-dizziness, tremor, psychosis, convulsions
-CNS depression can have anesthetic action (pain suppression) |
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Term
| What are the clinical indications for Class IB antiarrythmic drugs? |
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Definition
1. Ventricular arrhthmias only
-especially post MI to reduce ventricular fibrillation |
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Term
| What are the drugs of choice for Class IB antiarrhythmic drugs? |
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Definition
1. Lidocaine
-extensive 1st pass metabolism
-cannot be giving PO
-hepatic metabolism converts to active metabolites
-IV loading and maintenance dose follows 2 compartment model
2. Lidocaine analogs
-Mexiletine and Tocainide
3.Phenytoin
-used in digitalis-induced arrhythmias |
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Term
| What are the main cardiac effects of Class IC antiarrythmic drugs? |
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Definition
Widening of QRS and PR interval
-minimal effect on QT interval |
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Term
| What are the toxicities of Class IC antiarrythmic drugs? |
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Definition
1. Aggrevation of AV block
-can lead to ventricular tachycardia
2. increased mortality in CAST with encainide, flecainide |
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Term
| What are the clinical indications of Class IC antiarrythmic drugs? |
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Definition
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Term
| What are the drugs of choice for the Class IC antiarrythmic drugs? |
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Definition
| Flecainide, Propafenone, Moricizine |
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Term
| What are the toxicities of Class IC antiarrythmic drugs? |
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Definition
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Term
| What are the main cardiac effects of Class II antiarrythmic drugs? |
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Definition
Beta-Blocking Agents
1. Effects Pacemaker cells: SA, AV and purkinje fibers
2. Decrease HR, slowed AV conduction, increased PR interval, decreased automaticity (especially related to SNS)
3. Decreases cardia work and oxygen consumption
4. Post MI reduction of reinfarction and sudden death |
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Term
| What are the clinical indications for Class II antiarrythmic drugs? |
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Definition
1. Supraventricular arrhythmias
-some ventricular arrhythmias |
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Term
| What are the drugs of choice and selectivity of Class II antiarrhythmic drugs? |
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Definition
1. Propranolol - non-selective blocking
2. Acebutolol - Beta 1
3. Esmolol - Beta 1
4. Metoprolol - Beta 1 |
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Term
What do Beta receptors do?
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Definition
| Beta blockers target the beta receptor. Beta receptors are found on cells of the heart muscles, smooth muscles, airways, arteries, kidneys, and other tissues that are part of the sympathetic nervous system and lead to stress responses, especially when they are stimulated by epinephrine(adrenaline). Beta blockers interfere with the binding to the receptor of epinephrine and other stress hormones, and weaken the effects of stress hormones |
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Term
| What are the 3 beta receptors and their actions? |
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Definition
| β1-adrenergic receptors are located mainly in the heart and in the kidneys.[7] β2-adrenergic receptorsare located mainly in the lungs, gastrointestinal tract, liver, uterus, vascular smooth muscle, and skeletal muscle.[7] β3-adrenergic receptors are located in fat cells |
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Term
| What are the cardiac effects of Class III antiarrhythmic drugs? |
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Definition
K+ Channel Blockers = Class III
1. Increase effective refractive period
- decreases re-entry arrhythmias
-Prolong RP (phase 1-3) and AP duration, w/o significant Na+ channel blockade
2 Amiodarone specific
- decreased conduction velocity = decrease re-entry
-decreased rate of firing (Phase 4 slope)
-causes decreased automaticity |
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Term
| What are the clinical indications for Class III antiarrhythmic drugs? |
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Definition
Atrial, nodal and ventricular arrhythmias
very broad use |
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Term
| What are the toxicities of Class III antiarrhythmic drugs? |
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Definition
1. microdeposits in cornea skin and other tissues
2. pulmonary toxicity - fibrosiss
3. peripheral neuroapthy and myopathy
4. abnormal liver function
5. thyroid dysfunction
6. photosensativity - blue-gray skin discoloration in sun exposed areas |
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Term
| What are the drugs of choice for Class III antiarrhythmic drugs? |
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Definition
| Bretylium, Sotalol, Amiodarone, Ibutilide, Dofetilide |
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Term
| What are the cardiac effects of Class IV antiarrhythmic drugs? |
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Definition
1. decreased conduction velocity of AV node
2. increased refractory period of AV node
Both lead to decreased re-entry |
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Term
| What are the drugs of choice for Class IV antiarrhythmic drugs? |
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Definition
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Term
| What are the toxicities of Class IV antiarrhythmic drugs? |
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Definition
GI - constipation with verapamil
Hypotension
decreased HR
AV block
potential for CHF |
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Term
| What are the clinical indications for Class IV antiarrhythmic drug use? |
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Definition
suppresses ventricular rate in atrial flutter and fibrillation
compare to digitlis and beta-blockers |
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