Arrhythmias: classification and antiarrhythmic therapy MCQs With Answer

Introduction: Arrhythmias: classification and antiarrhythmic therapy MCQs With Answer is a concise, exam-focused resource tailored for M.Pharm students studying Pharmacotherapeutics I (MPP 102T). This set of MCQs covers electrophysiological foundations, the Vaughan-Williams classification and newer classification concepts, mechanisms of action of major antiarrhythmic drugs, clinical indications, adverse effects, pharmacokinetics, and therapeutic monitoring. Questions emphasize mechanistic understanding, drug selection for specific arrhythmias, interactions and safety concerns (e.g., QT prolongation, proarrhythmia), and practical considerations in acute and chronic management. Use these items to deepen conceptual knowledge, prepare for assessments, and reinforce rational therapeutic choices in arrhythmia management.

Q1. Which of the following best describes the primary electrophysiological mechanism targeted by Class IA antiarrhythmic drugs?

• Predominant blockade of fast sodium channels with strong use-dependent block and no effect on repolarization
• Intermediate blockade of fast sodium channels plus moderate potassium channel blockade leading to prolonged action potential duration
• Selective blockade of L-type calcium channels reducing AV nodal conduction
• Beta-adrenergic receptor antagonism decreasing sympathetic tone

Correct Answer: Intermediate blockade of fast sodium channels plus moderate potassium channel blockade leading to prolonged action potential duration

Q2. Which drug is most appropriate for acute termination of paroxysmal supraventricular tachycardia (AV nodal reentrant tachycardia) in an otherwise stable adult?

• Oral amiodarone
• Intravenous adenosine
• Oral flecainide
• Intravenous sotalol

Correct Answer: Intravenous adenosine

Q3. Which antiarrhythmic class is characterized primarily by potassium channel blockade that prolongs repolarization and increases action potential duration?

• Class I
• Class II
• Class III
• Class IV

Correct Answer: Class III

Q4. Regarding amiodarone, which statement about its pharmacology and safety profile is most accurate?

• It has a short half-life and minimal tissue accumulation, making it ideal for short courses only
• It is purely a Class III agent without any effect on sodium, calcium channels or adrenergic receptors
• It is highly lipophilic with a very long half-life and multi-channel effects but requires monitoring for thyroid, pulmonary and hepatic toxicity
• It commonly causes torsades de pointes due to marked QT prolongation in most patients

Correct Answer: It is highly lipophilic with a very long half-life and multi-channel effects but requires monitoring for thyroid, pulmonary and hepatic toxicity

Q5. Which of the following best describes “use‑dependent” block seen with some sodium channel blockers?

• Block is stronger at lower heart rates and weaker at high frequencies
• Block increases with repetitive depolarizations and higher heart rates
• Block occurs only in resting (diastolic) membrane potentials
• Block depends only on drug concentration, independent of channel state

Correct Answer: Block increases with repetitive depolarizations and higher heart rates

Q6. Which antiarrhythmic is contraindicated in patients with structural heart disease due to increased risk of mortality and proarrhythmia?

• Flecainide
• Amiodarone
• Sotalol
• Verapamil

Correct Answer: Flecainide

Q7. Which agent is a Class IB antiarrhythmic commonly used for ventricular arrhythmias, especially in the setting of acute myocardial ischemia?

• Lidocaine
• Procainamide
• Disopyramide
• Quinidine

Correct Answer: Lidocaine

Q8. Which of the following drugs is a pure IKr (rapid delayed rectifier potassium current) blocker used for maintenance of sinus rhythm in atrial fibrillation and requires hospitalization for initiation because of QT monitoring?

• Dofetilide
• Amiodarone
• Propafenone
• Sotalol

Correct Answer: Dofetilide

Q9. Which antiarrhythmic drug acts predominantly by blocking L-type calcium channels and is particularly effective in controlling ventricular rate in atrial flutter or fibrillation by slowing AV nodal conduction?

• Verapamil
• Amiodarone
• Mexiletine
• Propranolol

Correct Answer: Verapamil

Q10. Which statement about sotalol’s pharmacology is correct?

• Sotalol is a selective beta-1 blocker without any potassium channel effects
• Sotalol combines nonselective beta-blockade with Class III potassium channel blocking activity and can prolong QT interval
• Sotalol is primarily a sodium channel blocker used for atrial fibrillation conversion
• Sotalol has no proarrhythmic potential and requires no ECG monitoring

Correct Answer: Sotalol combines nonselective beta-blockade with Class III potassium channel blocking activity and can prolong QT interval

Q11. Which antiarrhythmic is associated with a significant risk of pulmonary fibrosis and thyroid dysfunction due to high iodine content?

• Amiodarone
• Flecainide
• Digoxin
• Diltiazem

Correct Answer: Amiodarone

Q12. For rate control in chronic atrial fibrillation in a patient with heart failure with reduced ejection fraction (HFrEF), which drug class is preferred?

• Non-dihydropyridine calcium channel blockers (verapamil/diltiazem)
• Class IC antiarrhythmics
• Cardioselective beta-blockers
• Pure potassium channel blockers

Correct Answer: Cardioselective beta-blockers

Q13. Which mechanism explains digitalis (digoxin) usefulness in controlling ventricular rate in atrial fibrillation?

• Direct blockade of cardiac sodium channels increasing conduction velocity through AV node
• Increase in vagal parasympathetic tone leading to slowed AV nodal conduction
• Direct prolongation of atrial action potential via potassium channel blockade
• Beta-adrenergic stimulation enhancing AV node refractoriness

Correct Answer: Increase in vagal parasympathetic tone leading to slowed AV nodal conduction

Q14. Torsades de pointes is most commonly associated with which pharmacologic effect?

• Excessive shortening of QT interval
• Marked QT prolongation due to delayed ventricular repolarization (IKr block)
• Pure beta-adrenergic blockade
• Excessive sodium channel activation

Correct Answer: Marked QT prolongation due to delayed ventricular repolarization (IKr block)

Q15. Which antiarrhythmic is known for significant anticholinergic and negative inotropic effects and may exacerbate heart failure despite strong sodium-channel blockade?

• Disopyramide
• Amiodarone
• Mexiletine
• Propafenone

Correct Answer: Disopyramide

Q16. Which property differentiates Class IC agents (flecainide, propafenone) from Class I subclasses regarding their effect on action potential duration?

• Class IC agents markedly prolong action potential duration and refractory period
• Class IC agents have minimal effect on action potential duration but produce potent sodium channel blockade with marked slowing of conduction
• Class IC agents selectively block calcium channels and shorten action potential
• Class IC agents act primarily on potassium channels to shorten repolarization

Correct Answer: Class IC agents have minimal effect on action potential duration but produce potent sodium channel blockade with marked slowing of conduction

Q17. In perioperative management, which antiarrhythmic is commonly avoided because of risk of exacerbating bradyarrhythmias and conduction block when combined with beta-blockers?

• Ivabradine
• Verapamil
• Amiodarone
• Procainamide

Correct Answer: Verapamil

Q18. Which drug is indicated for conversion of recent-onset atrial fibrillation with a mechanism primarily inhibiting the funny current (If) in the sinoatrial node?

• Flecainide
• Ivabradine
• Ibutilide
• Adenosine

Correct Answer: Ibutilide

Q19. Which statement about adenosine is correct in the context of supraventricular tachycardia (SVT) management?

• Adenosine is a long-acting A1 receptor agonist used for chronic rate control
• Adenosine transiently blocks AV nodal conduction via activation of A1 receptors and is useful for diagnostic termination of AVNRT
• Adenosine is contraindicated in Wolf-Parkinson-White syndrome because it permanently alters accessory pathway conduction
• Adenosine primarily prolongs ventricular action potential by blocking potassium channels

Correct Answer: Adenosine transiently blocks AV nodal conduction via activation of A1 receptors and is useful for diagnostic termination of AVNRT

Q20. Which monitoring parameter is essential when initiating or increasing dose of a Class III antiarrhythmic that prolongs QT interval?

• Serum potassium and baseline and serial ECG for QT interval
• Only baseline liver function tests are required
• Pulmonary function tests are sufficient without ECG
• Serum digoxin level monitoring only

Correct Answer: Serum potassium and baseline and serial ECG for QT interval

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