Antiarrhythmic Agents

Question 1

Antiarrhythmic Classifications

Answer 1

• Class 1: Na+ Channel Blockers
• Class 2: Beta Blockers
• Class 3: K+ Channel Blockers
• Class 4: Ca++ Channel Blockers
• Other: adenosine, digitalis, atropine, magnesium

Question 2

AA MOA Options

Answer 2

• Slow conduction velocity of AP: increase refractoriness or create two-way block
• Change slope of Phase 4: decrease (B-blockers) or increase automaticity (atropine, EPI)
• Change threshold potential or maximum diastolic potential (decrease/increase automaticity)

Question 3

Classes 1 + Effects

Answer 3

• Class 1: decrease slop of phase 0 depolarization
• Class 1A: Increase ERP/AP duration, increase QT/QRS/PR
• Class 1B: Decrease ERP/AP duratio, no ECG change
• Classe 1C: Normal ERP/AP duration, increase PR/QRS
• Slow depolarization: 1c > 1b > 1a
• Monitor QT interval in these patients to prevent Torsades

Question 4

Class 2 + Effects

Answer 4

• Class 2: Decrease slope of phase 4 depolarization, prolong repolarization of AV node
• AV nodal blockade
• Decreases HR and increases PR (monitor to prevent AV block)

Question 5

Class 3 + Effects

Answer 5

• Class 3: Prolonged repolarization, increase ERP/AP duration
• Slow repolarization
• Increases QT interval

Question 6

Class 4 + Effects

Answer 6

• Class 4: slow rise of action potential, prolonged repolarization of AV node, increase PR interval and ERP
• AV nodal blockade
• Decreases HR and increases PR (monitor to prevent AV block)

Question 7

Treating Torsades

Answer 7

• Severe/symptomatic: electrocardioversion (defib, cardioversion)
• Mg+: suppresses EAD, helps terminate arrhythmia, decreases Ca++ and lowers EAD amplitudes
• Correct electrolyte imbalance if presented, remove offending agent if present
• Isoproterenol: accelerates AV conduction and decreases QT interval by increasing HR and reducing temporal dispersion of repolarization

Question 8

CV Drugs Causing Torsades

Answer 8

• Quinidine
• Procainamide
• Disopyramide
• Dofetilide
• Ibutilide
• Sotalol
• Flecainide
• Propafenone

Question 9

Non-CV Drugs Causing Torsades

Answer 9

• Erythromycin
• Clarithromycin
• Cholorquine
• Pentamidine
• Amantidine
• Trimethoprim-sulfamethoxazole
• Haloperidol
• Fluroquinolones

Question 10

Amiodarone

Answer 10

• Atrial arrhythmias or AV block: 100-200 mg/day (may or may not use loading dose)
• V-arrhythmias: 400 mg/day (often use loading dose)
• Excretion: half life increases with chronic use of medication, Css takes MONTHS to achieve
• Does adjustments aren’t necessary in renal or hepatic disease
• Inhibits most drug metabolizing enzymes