IBHRE Pharmacology and Drug Therapy 1 — Questions and Answers
Question 1: Which class of antiarrhythmic drug works by blocking fast sodium channels?
- Class I (Correct answer)
- Class II
- Class III
- Class IV
Correct answer: Class I
Class I antiarrhythmic drugs block fast sodium channels, slowing phase 0 depolarization and conduction velocity.
Question 2: Amiodarone is primarily classified under which Vaughan Williams class?
- Class I
- Class II
- Class III (Correct answer)
- Class IV
Correct answer: Class III
Amiodarone is primarily a Class III antiarrhythmic that blocks potassium channels to prolong the action potential and refractory period.
Question 3: Which antiarrhythmic drug is contraindicated in structural heart disease due to increased mortality demonstrated in the CAST trial?
- Metoprolol
- Flecainide (Correct answer)
- Amiodarone
- Sotalol
Correct answer: Flecainide
Flecainide (Class IC) is contraindicated in structural heart disease because the CAST trial showed it significantly increased mortality in post-MI patients.
Question 4: What is the primary mechanism by which adenosine terminates paroxysmal SVT?
- Blocks L-type calcium channels
- Activates A1 receptors causing transient AV block (Correct answer)
- Blocks IKr potassium channels
- Activates beta-adrenergic receptors
Correct answer: Activates A1 receptors causing transient AV block
Adenosine activates A1 receptors on AV nodal cells, increasing potassium conductance and causing transient AV block that interrupts reentrant SVT.
Question 5: Ibutilide is primarily indicated for acute pharmacological conversion of which arrhythmia?
- Ventricular tachycardia
- Atrial flutter and atrial fibrillation (Correct answer)
- AVNRT
- Sinus tachycardia
Correct answer: Atrial flutter and atrial fibrillation
Ibutilide is an IV Class III agent specifically approved for rapid pharmacological cardioversion of atrial flutter and atrial fibrillation.
Question 6: Which beta-blocker has an ultra-short half-life of approximately 9 minutes, making it ideal for acute rate control?
- Metoprolol
- Esmolol (Correct answer)
- Atenolol
- Carvedilol
Correct answer: Esmolol
Esmolol has an ultra-short half-life of approximately 9 minutes due to rapid hydrolysis by red blood cell esterases.
IBHRE Pharmacology and Drug Therapy 1
Which class of antiarrhythmic drug works by blocking fast sodium channels?