CET Cardiac Pharmacology Effects on ECG 2 — Questions and Answers
Question 1: Amiodarone is known to prolong which ECG interval, increasing the risk of Torsades de Pointes?
- PR interval
- QRS duration
- QT interval (Correct answer)
- ST segment
Correct answer: QT interval
Amiodarone prolongs the QT interval by blocking potassium channels, which can precipitate Torsades de Pointes in susceptible patients.
Question 2: A patient receiving IV adenosine for SVT shows a brief pause on the ECG strip. What does this pause represent?
- Ventricular fibrillation
- Transient AV block (Correct answer)
- Bundle branch block
- Sinus bradycardia
Correct answer: Transient AV block
Adenosine transiently blocks AV conduction, producing a brief AV block that terminates re-entrant SVT and appears as a pause on the ECG.
Question 3: Which beta-blocker ECG effect helps differentiate it from calcium channel blocker toxicity on the ECG?
- Prolonged QT interval
- Widened QRS complex
- Bradycardia with narrow QRS vs. bradycardia with wide QRS (Correct answer)
- ST elevation in V1-V3
Correct answer: Bradycardia with narrow QRS vs. bradycardia with wide QRS
Beta-blocker toxicity typically causes bradycardia with a narrow QRS, while calcium channel blocker toxicity may cause bradycardia with a wide QRS and conduction abnormalities.
Question 4: Sotalol combines beta-blocking and Class III antiarrhythmic properties. Which ECG change is most expected?
- Shortened PR interval
- Widened QRS with LBBB pattern
- Prolonged QT interval (Correct answer)
- ST depression in inferior leads
Correct answer: Prolonged QT interval
Sotalol's Class III action blocks potassium channels, prolonging repolarization and the QT interval.
Question 5: A patient on procainamide develops a wide-complex tachycardia on ECG. What drug toxicity phenomenon is most likely?
- Proarrhythmia with widened QRS (Correct answer)
- Hyperkalemia-induced changes
- Acute MI pattern
- Wolff-Parkinson-White pre-excitation
Correct answer: Proarrhythmia with widened QRS
Procainamide toxicity causes QRS widening due to sodium channel blockade, which can lead to proarrhythmic ventricular tachycardia.
Question 6: Which ECG finding in a digitalis-toxic patient most urgently requires physician notification?
- Prolonged PR interval
- ST scooping in V5
- Bidirectional ventricular tachycardia (Correct answer)
- Shortened QT interval
Correct answer: Bidirectional ventricular tachycardia
Bidirectional ventricular tachycardia is a hallmark of severe digitalis toxicity and is a life-threatening emergency requiring immediate intervention.
Question 7: Flecainide, a Class IC drug, primarily affects the ECG by:
- Prolonging the QT interval only
- Shortening the PR interval
- Widening the QRS complex significantly (Correct answer)
- Causing peaked T waves
Correct answer: Widening the QRS complex significantly
Flecainide blocks fast sodium channels, markedly slowing intraventricular conduction and widening the QRS complex.
CET Cardiac Pharmacology Effects on ECG 2
Amiodarone is known to prolong which ECG interval, increasing the risk of Torsades de Pointes?