Chap 25 Antidysrhythmic Drugs Flashcards
Antidysrhythmics
Dysrhythmia*
Any deviation* from the normal* rhythm* of the heart*
Arrhythmia*
“No rhythm”* which implies asystole
Terms dysrhythmia* and arrhythmia are used interchangeably with
the term arrhythmia being most commonly used.
Antidysrhythmics
Used* for the treatment* and prevention of disturbances in cardiac rhythm
Action Potential
Four* phases
Phase 0:* upstroke
Resting cardiac cell membrane suddenly becomes highly permeable to sodium ions; movement through sodium channels
Depolarization*
Phase 1*
Begins a rapid process of repolarization* that continues through Phases 2 and 3 to Phase 4, which is the RMP
Common Dysrhythmias
Supraventricular* dysrhythmias
Originate above the ventricles in SA or AV node or atrial myocardium
Ventricular dysrhythmias
Originate below the AV node in the His-Purkinje system or ventricular myocardium
Ectopic foci
Outside the conduction system
Conduction blocks
Dysrhythmias that involve the disruption of impulse conduction between the atria and ventricles
Atrial fibrillation
AV nodal reentrant tachycardia (AVNRT)
Paroxysmal supraventricular tachycardia (PSVT)
Varying degrees of AV block
Premature ventricular contractions (PVC)
Ventricular fibrillation
Ventricular tachycardia
Antiarrhythmic Drug Classes
IA: Police Department Questions
Procainamide Diospyramide Quinidine
IB: Liquored Man
Lidocaine Mexiletine
IC: For Peeing
Flecainide Propafenone
II: (Not included in Mnemonic (2=BB)
Beta Blockers
III: After Drinking Scotch In Dark
Amiodarone Dronedarone Sotalol Ibutilide Dofetilide
IV: Dirty Vehicle
Diltiazem Verpamil
Antiarrhythmic Drug Mechanism of Action and Indications
Class I*
Membrane-stabilizing drugs
Fast sodium channel blockers
Divided into Ia, Ib, and Ic drugs, according to
Vaughan Williams Classification:
Class Ia: procainamide, quinidine, and disopyramide
Block sodium (fast) channels
Delay repolarization
Increase APD
Used for atrial fibrillation, premature atrial contractions, premature ventricular contractions, ventricular tachycardia, Wolff-Parkinson- White syndrome
Procainamide (Pronestyl)
Class Ia*
Uses: atrial and ventricular tachydysrhythmias
Significant adverse effects: include ventricular dysrhythmias, blood disorders, systemic lupus erythematosus (SLE)–like syndrome, nausea, vomiting, diarrhea, fever, leukopenia, maculopapular rash, flushing, and torsades de pointes resulting from prolongation of the QT interval
Contraindications: known hypersensitivity, heart block*, and SLE
Quinidine (Quinidex)
Class Ia*
Both direct action on the electrical activity of the heart and indirect (anticholinergic) effect
Significant adverse effects: cardiac asystole and ventricular ectopic beats
Others: cinchonism (tinnitus, loss of hearing, blurring vision, GI upset)
Black box warning: can cause torsades de pointes
Antiarrhythmic Drug Mechanism of Action and Indications Class IB
Vaughan Williams Classification:
Class Ib: phenytoin, lidocaine*
Block sodium channels
Accelerate repolarization
Increase or decrease APD
Lidocaine is used for ventricular dysrhythmias only.
Phenytoin is used for atrial and ventricular tachydysrhythmias caused by digitalis toxicity or long QT syndrome.
Lidocaine (Xylocaine)
Class Ib
Action: raises the ventricular fibrillation threshold
Significant adverse effects: twitching, convulsions, confusion, respiratory depression or arrest, hypotension, bradycardia, and dysrhythmias
Contraindications: hypersensitive, severe SA or atrioventricular (AV) intraventricular block, or Stokes-Adams or Wolff-Parkinson- White syndrome
Antiarrhythmic Drug Mechanism of Action and Indications Class IC
Vaughan Williams Classification:
Class Ic: flecainide, propafenone*
Block sodium channels (more pronounced effect)
Little effect on APD or repolarization
Used for severe ventricular dysrhythmias
May be used in atrial fibrillation or flutter, Wolff-Parkinson-White syndrome, supraventricular tachycardia dysrhythmias
Antiarrhythmic Drug Mechanism of Action and Indications Class II
Vaughan Williams Classification:
Class II: beta blockers
Reduce or block sympathetic nervous system stimulation, thus reducing transmission of impulses in the heart’s conduction system
Depress Phase 4 depolarization
General myocardial depressants for both supraventricular and ventricular dysrhythmias
Also used as antianginal and antihypertensive drugs
Antiarrhythmic Drug Mechanism of Action and Indications Class III
Vaughan Williams Classification:
Class III: amiodarone, dronedarone, dofetilide, sotalol, ibutilide
Increase APD
Prolong repolarization in Phase 3
Used for dysrhythmias that are difficult to treat
Life-threatening ventricular tachycardia or fibrillation, atrial fibrillation or flutter that is resistant to other drugs
Ibutilide (Corvert)
Class III*
Indicated for atrial dysrhythmias
Dosed based on body weight
Can cause ventricular dysrhythmias
Antiarrhythmic Drug Mechanism of Action and Indications Class IV
Vaughan Williams Classification:
Class IV:*
Calcium channel blockers
Inhibit slow-channel (calcium-dependent) pathways
Depress Phase 4 depolarization
Reduce AV node conduction
Used for paroxysmal supraventricular tachycardia (PSVT); rate control for atrial fibrillation and flutter
Diltiazem (Cardizem, Others)
Class IV*
Temporary control of a rapid ventricular response in patients with atrial fibrillation or flutter and PSVT
Contraindications: hypersensitivity, acute myocardial infarction, pulmonary congestion, Wolff-Parkinson-White syndrome, severe hypotension, cardiogenic shock, sick sinus syndrome, or second- or third-degree AV block
