ANTIARRHYTHMIC THERAPY
AUTOMATICITY
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All cardiac cells have the potential to be
a pacemaker - if it is not the S-A node initiating an impulse = arrhythmia
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Latent pacemakers fire slower then the S-A
node
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Causes of ectopic foci: ischemia, acidosis, suppressant drugs
REFRACTORINESS
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Responsiveness of a cardiac membrane during recovery of previous
activity
MECHANISM OF ACTION OF
ANTIARRHYTHMICS
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DECREASE AUTOMATICITY
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INCREASE THE REFRACTORY PERIOD
QUINIDINE
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DIFFERENT SALTS
• SULFATE
IS 83% QUINIDINE
• GLUCONATE
IS 62% QUINIDINE
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PHARMACOLOGY
• DECREASE
AUTOMATICITY
• INCREASE
REFRACTORY PERIOD
• Intravenous:
dilate vessel (hypotension)
• Increase
conduction thru A-V node
ADVERSE REACTIONS
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ARRHYTHMOGENIC
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TOXICITY: Cinchonism
• Tinnitus
• Headache
• Nausea/vomiting
• vertigo
QUINIDINE USAGE
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ATRIAL TACHYCARDIA
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ATRIAL FIBRILLATION
• Use digoxin as adjunct
therapy
PROCAINAMIDE
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PHARMACOLOGY
• Decreases automaticity
• Increases refractory
period
• Slows A-V conduction
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ADVERSE REACTIONS
• Lupus-like Syndrome
• Dose Related, Reversible
• Arrhythmogenic
PROCAINAMIDE USE
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Atrial Tachycardia
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Atrial Fibrillation
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Ventricular Arrhythmia - intravenous use when lidocaine fails or
is contraindicated
DISOPYRAMIDE
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PHARMACOLOGY
• Decrease Automaticity
• Increase Refractory
Period
• No Effect on A-V
conduction
• Strong anticholinergic
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CONTRAINDICATION
• Congestive Heart
Failure
DISOPYRAMIDE USE
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Atrial Tachycardia
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Atrial Fibrillation
LIDOCAINE
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PHARMACOLOGY
• Local anesthetics
• Antiarrhythmic
(intravenous use only)
• High therapeutic index
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ADVERSE EFFECTS
• CNS Toxicity: tinnitus, respiratory depression, seizure
LIDOCAINE
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Antiarrhythmic Dosing
• Loading Dose
• Intravenous infusion
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USE
• Ventricular
Arrhythmias
• Digoxin toxicity
arrhythmias
CLASS 1B AND 1C
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Mexelitine, Tocainide, Flecainide
• Oral agents for
ventricular arrhythmias
• pharmacology similar
to lidocaine
PROPRANOLOL
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BETA BLOCKER
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INTRAVENOUS USE AS AN ANTIARRYTHMIC
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USE
• atrial tachycardia
• ventricular
tachycardia
BRETYLIUM
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ANTIADRENERGIC
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INTRAVENOUS USE ONLY
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USE
• Ventricular arrhythmia
unresponsive to lidocaine and procainamide
AMIODARONE
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45 DAY HALF LIFE
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USE - VENTRICULAR ARRHYTHMIAS
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IV FORM TO TREAT VENTRICULAR ARRHYTHMIAS
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ADVERSE REACTIONS
• cataract
• pulmonary fibrosis
• hypothyroid
VERAPAMIL
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CALCIUM CHANNEL BLOCKER
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INTRAVENOUS PUSH FOR ANTIARRHYTHMIC PROPERTIES
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SECOND DOSE CAN BE REPEATED IN 5 MINUTES
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90% EFFECTIVE
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USE - atrial tachycardia
ATROPINE
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ANTICHOLINERGIC
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INTRAVENOUS PUSH FOR ANTIARRHYTHMIC USE
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USE - sinus bradycardia