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34 Cards in this Set
- Front
- Back
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What is an arrhythmia?
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An abnormality in rate, regularity, or site of origin of cardiac impulse, or a disruption in impulse conduction so that the normal sequence of atrial and ventricular activation is changed
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What are some possible causes of arrhythmias?
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• Imbalances of parasympathetic and sympathetic influences
• Changes in serum electrolyte conc. (esp. K+ and Ca2+) • Hypoxemia; ischemia and infarction of heart muscle • Acidosis; changes in CO2 conc. • Excessive stretch of cardiac tissue; mechanical trauma; myocardial diseases |
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What type of drugs are considered Class I antiarrhythmic drugs?
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* Local anesthetic agents; Membrane stabilizers
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What are "membrane stabilizers"
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They block fast Na+ channels which causes decrease upstroke of Phase 0 which causes decreased conduction velocity in normal or abnormal cardiac tissue
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What are Class I antiarrhythmic drugs used to treat?
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tachyarrhythmias
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What drugs are considered Class Ia antiarrhythmic drugs?
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* Quinidine
* Procainamide * Disopyramide |
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What is the mechanism of Class Ia antiarrhythmic drugs?
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* They depress conduction in normal/abnormal cardiac tissue
* Prolong repolarization |
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What drugs are considered Class Ib antiarrhythmic drugs?
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* Lidocaine
* Tocainide * Mexiletine * Phenytoin |
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What is the mechanism of Class Ib antiarrhythmic drugs?
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They accelerate repolarization and shorten AP duration, esp. in cells with longer AP (i.e. Purkinje fibers)
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What drugs are considered Class Ic antiarrhythmic drugs?
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* Encainide
* Flecainide |
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What is the mechanism of Class Ic antiarrhythmic drugs?
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They slow conduction; little effect on action potential duration
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What type of drugs are Class II antiarrhythmic drugs?
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Beta blockers
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What are Class II antiarrhythmic drugs used for?
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* Arrhythmias caused by increased sympathetic activity
* Used to treat supraventricular and ventricular tachyarrhythmias |
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What is the MOA for Class II antiarrhythmic drugs?
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* Cause decreased HR, decreased myocardial contractility and myocardial O2 consumption
* These lead to improvement in myocardial oxygenation which can affect cellular electrophysiology and reduce arrhythmia formation |
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What are some examples of Class II antiarrhythmic drugs?
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* Propranolol
* Oxyprenolol * Alprenolol |
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What type of drugs are Class III antiarrhythmic drugs?
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agents that prolong action potential duration
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What is the MOA of Class III antiarrhythmic drugs?
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* They cause prominent prolongation of action potential and extended refractory period
* This leads to increased fibrillation threshold; used to prevent sudden death due to ventricular tachyarrhythmias |
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What are some examples of Class III antiarrhythmic drugs?
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Amiodraone, Bretylium, Sotalol
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What type of drugs are Class IV antiarrhythmic drugs?
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calcium channel blockers
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What is the MOA of Class IV antiarrhythmic drugs?
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• Inhibit slow L-type Ca2+ channels, which are involved in depolarization of SA and AV junction
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What are Class IV antiarrhythmic drugs used for?
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• Used to slow AV conduction and control supraventricular arrhythmias involving AV renentry
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What lype of drug is Lidocaine?
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Class IB (local anesthetic agent)
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In regards to being a antiarrhythmic drug- what is MOA of Lidocaine?
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Shorten AP duration by accelerating repolarization, esp. in Purkinje fibers (may prolong effective refractory period of damaged myocardium)
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What type of arrhythmias is Lidocaine used for?
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Used in reverting ventricular dysrhythmias that form during anesthesia, surgery, ischemia, trauma
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What lype of drug is Sotalol?
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Class III (agent that prolongs AP duration)
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In regards to being a antiarrhythmic drug- what is MOA of Sotalol ?
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****Lengthens AP duration
• Blocks K+ channels which decreases the rate of repolarization, increased plateau phase * Increases ventricular fibrillation threshold |
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What type of drug is Amiodarone?
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Class III (agent that prolongs AP duration)
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In regards to being a antiarrhythmic drug- what is MOA of Amiodarone?
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* Lengthens AP duration, but doesn’t affect resting membrane potential
* Its metabolite (desethylamiodarone) blocks fast Na+ channels |
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What type of drug is Procainamide?
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Class IA (local anesthetic agent)
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In regards to being a antiarrhythmic drug- what is MOA of Procainamide?
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It depresses conduction in normal/abnormal cardiac tissue; prolongs repolarization, lengthens AP duration
* Block Na+ channels which leads to a slower rate of depolarization in Phase 0 |
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What type of drug is Diltiazem?
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Class IV agent (calcium channel blocker)
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In regards to being a antiarrhythmic drug- what is MOA of Diltiazem?
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****Blocks Ca2+ channel
• Lengthened duration of phase1 (depolarization) and phase 2 (plateau) of AP = neg. chronotrope • Less calcium enters cell to act in contractile mechanism = neg. inotropic effect |
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What type of drug is Quinidine?
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Class IA (local anesthetic agent)
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In regards to being a antiarrhythmic drug- what is MOA of Quinidine?
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Depresses conduction in normal and abnormal cardiac tissue; prolong repolarization
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