ECG ECG Pharmacology and Cardiac Medications 1 — Questions and Answers
Question 1: Which ECG change is most commonly associated with digoxin toxicity?
- Prolonged PR interval and ST scooping (Correct answer)
- Short QT interval and tall T waves
- Wide QRS with right bundle branch block pattern
- Peaked P waves and shortened PR interval
Correct answer: Prolonged PR interval and ST scooping
Digoxin toxicity characteristically causes a prolonged PR interval and a 'scooped' or sagging ST segment depression.
Question 2: A patient taking amiodarone is most likely to show which ECG finding?
- Shortened QT interval
- Prolonged QT interval (Correct answer)
- Delta waves
- Shortened PR interval
Correct answer: Prolonged QT interval
Amiodarone prolongs ventricular repolarization, resulting in a prolonged QT interval on the ECG.
Question 3: Which class of antiarrhythmic drugs primarily works by blocking sodium channels and may widen the QRS complex?
- Class II
- Class III
- Class I (Correct answer)
- Class IV
Correct answer: Class I
Class I antiarrhythmics (e.g., lidocaine, flecainide) block sodium channels, slowing depolarization and widening the QRS complex.
Question 4: A patient receiving IV adenosine for SVT would most likely show which transient ECG finding immediately after the dose?
- Ventricular tachycardia
- Complete heart block or brief asystole (Correct answer)
- Atrial fibrillation
- Prolonged QT interval
Correct answer: Complete heart block or brief asystole
Adenosine transiently blocks AV node conduction, often producing a brief period of complete heart block or asystole before normal rhythm resumes.
Question 5: Hyperkalemia caused by potassium-sparing diuretics (e.g., spironolactone) would first appear on the ECG as:
- Flat T waves
- Peaked, narrow T waves (Correct answer)
- Prolonged QT interval
- Short PR interval
Correct answer: Peaked, narrow T waves
The earliest ECG manifestation of hyperkalemia is tall, peaked (tented) T waves due to altered ventricular repolarization.
Question 6: Which beta-blocker effect on the ECG helps an ECG technician recognize its therapeutic use?
- Shortened PR interval and faster heart rate
- Prolonged PR interval and slower heart rate (Correct answer)
- Widened QRS and peaked T waves
- Delta waves on multiple leads
Correct answer: Prolonged PR interval and slower heart rate
Beta-blockers slow AV node conduction, producing a prolonged PR interval, and reduce heart rate by decreasing SA node automaticity.
Question 7: A patient on a calcium channel blocker (e.g., verapamil) is expected to show which ECG change?
- Shortened PR interval
- Widened QRS complex
- Prolonged PR interval (Correct answer)
- Elevated ST segments
Correct answer: Prolonged PR interval
Calcium channel blockers slow conduction through the AV node, prolonging the PR interval on the ECG.
ECG ECG Pharmacology and Cardiac Medications 1
Which ECG change is most commonly associated with digoxin toxicity?