Antiarrythmics Lecture Review

This set of flashcards covers key concepts related to antiarrhythmic medications, including classifications, mechanisms, dosing, indications, contraindications, side effects, and drug interactions. The information compiled from lecture notes facilitates effective review for exam preparation.

What is the mechanism of action of Class IA antiarrhythmic drugs?

Na⁺ channel blocker; slows Phase 0 depolarization in ventricular muscle fibers.

What is the mechanism of action of Class IB antiarrhythmic drugs?

Na⁺ channel blocker; shortens Phase 3 repolarization in ventricular muscle fibers.

What is the mechanism of action of Class IC antiarrhythmic drugs?

Na⁺ channel blocker; markedly slows Phase 0 depolarization in ventricular muscle fibers.

What is the mechanism of action of Class II antiarrhythmic drugs?

β‑Adrenoreceptor blocker; inhibits Phase 4 depolarization in SA and AV nodes.

What is the mechanism of action of Class III antiarrhythmic drugs?

K⁺ channel blocker; prolongs Phase 3 repolarization in ventricular muscle fibers.

What is the mechanism of action of Class IV antiarrhythmic drugs?

Ca²⁺ channel blocker; inhibits action potential in SA and AV nodes.

What do Class Ia sodium channel blockers do to QRS duration and QT interval?

Increase QRS duration and QT interval.

What is the electrophysiologic effect of Class Ia sodium channel blockers?

Significantly prolong the repolarization process; slows Phase 0 depolarization.

What do Class Ib sodium channel blockers do to the QT interval?

Decrease QT interval slightly.

What is the electrophysiologic effect of Class Ib sodium channel blockers?

Weakly blocks sodium channels and decreases action potential duration; promotes outflow of potassium; shortens Phase 3 repolarization.

What do Class Ic sodium channel blockers do to QRS duration and QT interval?

Increase QRS duration, prolong QT interval.

What is the electrophysiologic effect of Class Ic sodium channel blockers?

Block rapid sodium channels; inhibition of Phase 0 depolarization; stronger effect on ventricular arrhythmia.

What are the ADRs of Class I sodium channel blockers?

Ventricular arrhythmias; QT prolongation; acute heart failure; nausea/vomiting; dizziness, coordination, balance, speech issues; visual disturbances; rash, hives, itch; fatigue, sleepiness.

What are the mechanisms of action of Class Ia medications?

Block repolarizing potassium channels; prolong the refractory periods of fast-channel tissues; slow Phase 0 depolarization in cardiac myocytes.

What are the supraventricular tachyarrhythmia indications for Class Ia medications?

A-Fib and Flutter; atrial tachycardia.

What are the ventricular tachyarrhythmia indications for Class Ia medications?

Ventricular tachycardia; V-Fib.

What are the Class Ia medications?

Procainamide (Pronestyl); Disopyramide (Norpace); Quinidine.

What are the common side effects of Class Ia medications?

Ventricular arrhythmia; QT prolongation; acute heart failure; CNS and anticholinergic effects; hemolytic anemia.

What are the indications for Procainamide (Procan)?

Reserved for life-threatening atrial flutter/fibrillation & ventricular arrhythmias (IV & PO); ventricular and supraventricular arrhythmias.

What are the contraindications for Procainamide (Procan)?

Complete heart block; lupus erythematous; Torsades.

What major clinical trial warning is associated with Procainamide?

CAST Trial: ↑ mortality with Encainide/Flecainide in treatment of PVCs s/p MI.

What is the dose and maintenance dosing for Procainamide (Procan)?

Load: 14–17 mg/kg @ 25–50 mg/min; Maintenance: 1–4 mg/min or 2–6 grams/day.

What warnings are associated with Procainamide (Procan)?

↑ CHF; renal disease; myasthenia gravis (anti-cholinergic); sulfite allergy; QRS widening (>25%).

What should be done prior to administering Procainamide to reduce risk of V-tach?

Cardiovert OR digitalize (rate block) prior to Procainamide to reduce risk of V-tach.

What are the pregnancy and lactation considerations for Procainamide?

Pregnancy Cat C; avoid lactation.

What are the ADRs of Procainamide (Procan)?

Blood dyscrasias; gastrointestinal issues; Torsades de pointes; worsening heart failure.

What chronic-use effect may occur with Procainamide (>6 weeks)?

ANA (Anti-Nuclear Antibody) – lupus-like syndrome (i.e. myalgias, arthralgias, arthritis, pulmonary or pericardial serositis).

How is Procainamide metabolized and eliminated?

Hepatic metabolism: N-acetyl procainamide (NAPA); renal excretion: PA & NAPA.

What therapeutic monitoring is required for Procainamide?

Narrow therapeutic index drug; monitor PA & NAPA serum concentrations.

What is the indication for Disopyramide (Norpace)?

Alternative Rx: life-threatening ventricular arrhythmias; negative inotrope/anticholinergic effect.

What are the contraindications for Disopyramide (Norpace)?

Cardiogenic shock; QT prolongation; 2nd or 3rd degree AV block; bradycardia leading to syncope without a pacemaker; avoid in pregnancy & lactation.

What CAST trial warning applies to Disopyramide?

Don’t use other anti-arrhythmics in combination; no use in CrCL < 40 mL/min.

What is the dose for Disopyramide (Norpace)?

400–800 mg daily divided Q6–Q12 hrs.

What are the ADRs of Disopyramide (Norpace)?

Worsening CHF; hypotension; wide QRS; prolonged QT; hypoglycemia; worsens myasthenia gravis; glaucoma; urinary retention; gastrointestinal issues; hepatic cholestasis; worsen underlying conduction abnormalities (e.g., sick sinus syndrome, Wolf-Parkinson-White syndrome, bundle branch block).

How is Disopyramide metabolized and cleared?

Hepatic metabolism via 3A4; renal clearance (50%) unchanged.

What are the DDIs for Disopyramide (Norpace)?

↓ K⁺ → ↓ antiarrhythmic effect; 3A4 drugs.

What is the classification of Quinidine?

Class 1a; anti-parasitic (Plasmodium vivax & Plasmodium malariae).

What are the indications for Quinidine?

Conversion & maintenance of A-Fib/Flutter; life-threatening ventricular arrhythmias.

What are the contraindications for Quinidine?

History of immune thrombocytopenia; myasthenia gravis (anti-cholinergic).

What warnings are associated with Quinidine?

CAST effect; pro-arrhythmia; sick sinus syndrome; bradycardia; pregnancy category C; avoid lactation.

What is the dose for Quinidine?

Variable 200–600 mg PO Q 8 hrs.

What are the ADRs of Quinidine?

Thrombocytopenia; diarrhea; fever; rash; cinchonism (D, V, tinnitus, deafness, vertigo, diplopia, blurred vision, photophobia, headache, confusion, delirium); autoimmune & inflammatory syndromes (rash, blood dyscrasias, myalgia, systemic lupus erythematosus-like, pneumonitis).

How is Quinidine metabolized?

Hepatic metabolism via 3A4; half-life of active metabolite (3HQ).

What are the DDIs for Quinidine?

Diltiazem ↑ Quin concs; diuretics & NaHCO₃⁻ ↓ renal clearance of Quin; 3A4 drugs alter Quin concs; grapefruit ↓ 3A4 Quin metabolism; NaCl ↑ Quin concs; Quin ↑ digoxin concs.

What therapeutic monitoring is required for Quinidine?

Narrow therapeutic index; monitor quinidine concentrations.

What are the pharmacologic effects of Class Ib medications?

Shorten the action potential duration; manifest when the cardiac cell is firing rapidly; ventricular arrhythmias.

What are the Class Ib medications?

Lidocaine (Xylocaine); Mexiletine (Mexitil).

What are the common side effects of Class Ib medications?

Seizures; confusion; drowsiness; blurred vision; pro-arrhythmia.

What is Lidocaine used for?

Local anesthetic & antiarrhythmic; IV bolus produces immediate effect with duration of 15–20 mins.

What are the indications for Lidocaine?

Drug of choice for ventricular arrhythmia – post CABG & post MI; decreases Phase 3 repolarization; decreases duration of action potential.

What are the contraindications for Lidocaine?

Stokes-Adams syndrome; Wolf-Parkinson-White syndrome; severe SA, AV or intraventricular block.

What are the pregnancy and lactation considerations for Lidocaine?

Pregnancy category B; lactation unknown.

What is the dose for Lidocaine?

50–100 mg given as a 25–50 mg/min continuous infusion; maximum rate: 200–300 mg per hour.

What are the ADRs of Lidocaine?

CNS toxicity at high concentrations (drowsiness, slurred speech, confusion, convulsions, vomiting, tremors); cardiovascular issues (hypotension, bradycardia, cardiac arrest).

How is Lidocaine metabolized and eliminated?

Hepatic metabolism: 90%; 10% excreted unchanged.

What are the DDIs for Lidocaine?

↑ risk of arrhythmia/heart block with beta-blockers & digitalis.

What is Mexiletine and how is it used?

Similar to lidocaine; local anesthetic; anti-arrhythmic; oral dosage form.

What is the indication for Mexiletine?

Chronic treatment of ventricular arrhythmias associated with previous MI; may use in combination with amiodarone.

What are the contraindications for Mexiletine?

CAST effect; pro-arrhythmia; sick sinus syndrome; bradycardia; pregnancy category C; avoid lactation.

What is the dose for Mexiletine?

200–300 mg PO Q 8 hrs; maximum 1200 mg/day.

What are the ADRs of Mexiletine?

Gastrointestinal issues (vomiting and dyspepsia); CNS effects (lightheadedness, dizziness, tremor, ataxia, seizures); worsening of underlying conduction abnormalities; ventricular arrhythmias; acute liver injury; worsen CHF.

What are the DDIs for Mexiletine?

Drugs metabolized via CYP2D6 & CYP1A2 may alter mexiletine concentrations.

What are the indications for Class Ic medications?

A-Fib and Flutter; V-Fib and V-Tach; premature beats (A or V).

When should Class Ic medications be avoided?

Structural heart disease; left ventricular hypertrophy; heart failure; atherosclerotic heart disease.

What are the Class Ic medications?

Encainide (Enkaid) – off-market due to pro-arrhythmic effects; Flecainide (Tambacor); Propafenone (Rhythmol).

What are the side effects of Class Ic medications?

Increased risk of pro-arrhythmia; QT prolongation; acute heart failure; tremor; visual disturbances.

What class is Flecainide (Tambacor) and what is its mechanism?

Class 1c; local anesthetic; suppresses Phase 0 – slows conduction; blocks potassium channels.

What are the indications for Flecainide?

A-Fib/A-Flutter cardioversion (if absence of structural heart disease and no CHF); maintenance of sinus rhythm A-Fib/Flutter; refractory life-threatening ventricular arrhythmias.

What are the contraindications for Flecainide?

CAST effects; cardiogenic shock; sick sinus syndrome; 2nd or 3rd degree AV block; bradycardia leading to syncope without a pacemaker; pregnancy category C; lactation: penetrates breast milk.

What is the major warning for Flecainide?

Worsening CHF (negative inotropic effect).

What is the dose for Flecainide?

50–100 mg PO Q 12 hrs.

What are the ADRs of Flecainide?

Pro-arrhythmia; worsen existing heart failure; CNS effects; visual impairment; gastrointestinal issues.

How is Flecainide metabolized and eliminated?

Hepatic metabolism: CYP 450 2D6; half-life = 12–27 hrs; 20–50% excreted unchanged renal.

What are the DDIs for Flecainide?

CYP 2D6 drugs (quinidine) alter metabolism.

What class is Propafenone (Rhythmol) and what is its mechanism?

Class 1C; suppresses Phase 0 – slows conduction; does NOT block K⁺ channels.

What are the indications for Propafenone?

Maintenance of A-Fib/A-Flutter; not for rate control.

What are the contraindications for Propafenone?

CHF; cardiogenic shock; Brugada syndrome; bradycardia; SA, AV or intraventricular block; CAST effects; severe COPD or asthma; electrolyte disorder.

What warnings are associated with Propafenone?

Worsened arrhythmia; QT interval prolongation; worsened CHF; myasthenia gravis; caution in impaired hepatic & renal function; unmasks Brugada syndrome.

What is the dose for Propafenone?

225 mg PO Q 12 hrs to MAX of 425 mg PO Q 12 hrs.

What are the ADRs of Propafenone?

Gastrointestinal issues; CNS effects; bronchospasm; blood dyscrasias; anxiety; constipation; fatigue.

What are the DDIs for Propafenone?

CYP 2D6 & 3A4 & 1A2 inhibitors ↑ propafenone concentrations; propafenone ↑ digoxin & warfarin levels; Orlistat ↓ propafenone concentrations.

What are the pharmacologic effects of Class II beta-blockers?

↓ Phase 4 depolarization; ↓ heart rate, contractility, AV conduction and automaticity of SA/AV nodes; provides rate control for tachycardia caused by increased sympathetic activity; decreased heart rate and cardiac output; decreased systolic and diastolic blood pressure.

What are the indications for Class II beta-blockers?

Rate control A-Fib and Flutter; life-threatening arrhythmias post-MI & hypertension; CHF.

What are the Class II beta-blocker medications?

Atenolol (Tenormin); Metoprolol (Lopressor); Propranolol (Inderal); Esmolol (Breviblock).

What benefit does propranolol provide post-MI?

↓ risk of sudden arrhythmic death after MI; ↓ mortality rate in first year after MI.

What are the ADRs of Class II beta-blockers?

Hypotension; worsening heart failure; bronchospasm; bradycardia; fatigue; dizziness; peripheral vascular insufficiency.

What is Esmolol (Brevibloc) used for?

Short term Rx for perioperative tachycardia & hypertension; rate control of supraventricular tachycardia & sinus tachycardia.

What are the contraindications for Esmolol (Brevibloc)?

Cardiogenic shock; sick sinus syndrome; 2nd or 3rd degree AV block; bradycardia leading to syncope without a pacemaker; use with calcium channel blockers; pregnancy: risk of fetal hypoxia; lactation: unknown.

What warnings are associated with Esmolol (Brevibloc)?

Asthma; diabetes; pheochromocytoma (unopposed alpha agonism); rebound myocardial infarction with abrupt discontinuation.

What is the dose for Esmolol (Brevibloc)?

500 mcg/kg IV load over 60 seconds; then 50–300 mcg/kg/min (depends on indication).

What are the ADRs of Esmolol (Brevibloc)?

Hypotension; diaphoresis; bradycardia; dizziness.

How is Esmolol metabolized?

Hepatic metabolism; half-life = 9 minutes.

What are the DDIs for Esmolol (Brevibloc)?

Digoxin ↓ heart rate; anti-cholinesterases ↑ neuromuscular blockade; avoid vasoconstrictors & positive inotropes.

What are the pharmacologic effects of Class III potassium channel blockers?

Block outward potassium during repolarization; prolong ventricular action potential duration and refractory period; slow Phase 3 repolarization; decrease the frequency of pro-arrhythmias; all Class III drugs have the potential to induce arrhythmias.

What are the Class III medications?

Amiodarone (Cordarone); Dronedarone (Multaq); Sotalol (Betapace); Dofetilide (Tikosyn); Ibutilide (Corvert).

What are the common side effects of Class III medications?

QT prolongation; bradycardia; Torsade de pointes.

What is Amiodarone (Cordarone) and what are its key properties?

Potent antiarrhythmic & vasodilator; Class III; effects K⁺ channels, also Class I, II & IV effects; beta- & alpha-adrenergic receptor blocker; prolongs action potential; iodine in molecule.

What are the indications for Amiodarone?

Recurrent V-Fib; recurrent hemodynamically unstable V-Tach; mainstay Rx for rhythm management of A-Fib/Flutter.

What are the contraindications for Amiodarone?

Cardiogenic shock; sick sinus syndrome; 2nd or 3rd degree AV block; bradycardia leading to syncope without a pacemaker; avoid in pregnancy & lactation.

What are the ADRs of Amiodarone?

Pulmonary (eosinophilic/fibrosis); hepatic & cardiac (pro-arrhythmia) toxicity; congestive heart failure; thyroid (hypo- & hyper-); hepatitis.