ECG Cardiac Pharmacology 2 — Questions and Answers
Question 1: Which antiarrhythmic drug class works by blocking sodium channels and slowing phase 0 depolarization?
- Class I (Correct answer)
- Class II
- Class III
- Class IV
Correct answer: Class I
Class I antiarrhythmics block sodium channels, reducing the rate of rise of phase 0 of the cardiac action potential.
Question 2: A patient receives IV adenosine for SVT. Which ECG change would you expect immediately after administration?
- Transient AV block (Correct answer)
- Prolonged QT interval
- ST elevation
- Wide QRS complex
Correct answer: Transient AV block
Adenosine causes transient AV block by hyperpolarizing AV nodal cells, which terminates reentrant SVT.
Question 3: Digoxin toxicity on an ECG most commonly presents as which rhythm?
- PVCs with bigeminy (Correct answer)
- Atrial flutter
- Right bundle branch block
- Sinus tachycardia
Correct answer: PVCs with bigeminy
Digoxin toxicity classically causes increased automaticity and AV block, manifesting as PVCs and bigeminy on the ECG.
Question 4: Which drug used to treat atrial fibrillation primarily works by blocking IKr potassium channels to prolong the action potential?
- Dofetilide (Correct answer)
- Metoprolol
- Flecainide
- Verapamil
Correct answer: Dofetilide
Dofetilide is a pure Class III agent that selectively blocks IKr potassium channels, prolonging repolarization and the QT interval.
Question 5: A patient on amiodarone should be monitored for which ECG manifestation as a sign of toxicity?
- Markedly prolonged QT interval (Correct answer)
- Shortened PR interval
- Left axis deviation
- Delta waves
Correct answer: Markedly prolonged QT interval
Amiodarone prolongs the QT interval as a pharmacologic effect, and excessive prolongation increases the risk of torsades de pointes.
Question 6: Which calcium channel blocker is preferred for rate control in atrial fibrillation because it primarily acts on the AV node?
- Diltiazem (Correct answer)
- Amlodipine
- Nifedipine
- Nicardipine
Correct answer: Diltiazem
Diltiazem is a non-dihydropyridine calcium channel blocker that preferentially slows AV nodal conduction, making it effective for rate control.
Question 7: Lidocaine is classified as which Vaughan Williams antiarrhythmic class?
- Class IB (Correct answer)
- Class IA
- Class IC
- Class II
Correct answer: Class IB
Lidocaine is a Class IB sodium channel blocker that preferentially binds inactivated channels and shortens the action potential duration.
ECG Cardiac Pharmacology 2
Which antiarrhythmic drug class works by blocking sodium channels and slowing phase 0 depolarization?