Electrocardiogram (ECG) and its interpretation is a core clinical skill for B. Pharm students, linking pharmacology, cardiology and patient safety. This concise guide emphasizes ECG basics—P wave, PR interval, QRS complex, ST segment, T wave—and common disorders such as arrhythmias, ischemia, conduction blocks and electrolyte or drug-induced changes (e.g., digoxin, antiarrhythmics, QT prolongation). You will learn lead placement, axis interpretation, rate calculation and recognition of life-threatening patterns like ventricular tachycardia, atrial fibrillation and torsades. Understanding ECG helps pharmacists assess drug effects, counsel clinicians and anticipate adverse cardiac events. Now let’s test your knowledge with 30 MCQs on this topic.
Q1. What does the P wave on a standard ECG most directly represent?
- Atrial depolarization
- Atrial repolarization
- Ventricular depolarization
- AV nodal delay
Correct Answer: Atrial depolarization
Q2. Which interval represents conduction time from atrial onset to ventricular onset?
- QRS duration
- QT interval
- PR interval
- ST segment
Correct Answer: PR interval
Q3. Normal QRS duration in adults is closest to which value?
- Less than 120 ms
- 120–200 ms
- 200–300 ms
- Less than 60 ms
Correct Answer: Less than 120 ms
Q4. ST-segment elevation in contiguous leads most often indicates which condition?
- Pericarditis
- Acute myocardial infarction (transmural)
- Hyperkalemia
- Left bundle branch block
Correct Answer: Acute myocardial infarction (transmural)
Q5. Which ECG change is most characteristic of hyperkalemia?
- Flattened T waves
- Peaked T waves and widened QRS
- Prolonged PR with U waves
- Delta waves with short PR
Correct Answer: Peaked T waves and widened QRS
Q6. A sawtooth pattern in inferior leads usually indicates which rhythm?
- Atrial fibrillation
- Atrial flutter
- Ventricular tachycardia
- Sinus tachycardia
Correct Answer: Atrial flutter
Q7. Which drug class is most associated with QT prolongation and risk of torsades de pointes?
- Beta blockers
- Class III antiarrhythmics and some macrolide antibiotics
- ACE inhibitors
- Thiazide diuretics only
Correct Answer: Class III antiarrhythmics and some macrolide antibiotics
Q8. What does a delta wave on the ECG signify?
- Ventricular hypertrophy
- Accessory pathway pre-excitation (WPW syndrome)
- Complete heart block
- Acute ischemia
Correct Answer: Accessory pathway pre-excitation (WPW syndrome)
Q9. First-degree AV block is defined by a PR interval of:
- Less than 120 ms
- 120–160 ms
- Greater than 200 ms
- Greater than 300 ms
Correct Answer: Greater than 200 ms
Q10. Which finding suggests left ventricular hypertrophy on a 12-lead ECG (Sokolow-Lyon criteria)?
- S wave in V1 + R wave in V5 or V6 ≥ 35 mm
- QRS duration > 120 ms
- ST elevation in V2–V4
- Low voltage in all limb leads
Correct Answer: S wave in V1 + R wave in V5 or V6 ≥ 35 mm
Q11. Which electrolyte disturbance commonly produces prominent U waves?
- Hyperkalemia
- Hypokalemia
- Hypercalcemia
- Hyponatremia
Correct Answer: Hypokalemia
Q12. A regularly irregular rhythm with grouped beating and progressive PR prolongation suggests:
- Second-degree Mobitz I (Wenckebach) block
- Second-degree Mobitz II block
- Complete heart block
- Atrial fibrillation
Correct Answer: Second-degree Mobitz I (Wenckebach) block
Q13. Which lead is best for detecting inferior wall myocardial infarction?
- V1–V3
- Leads II, III and aVF
- Leads I and aVL
- V5 and V6
Correct Answer: Leads II, III and aVF
Q14. In atrial fibrillation, what feature is absent on the ECG?
- Irregularly irregular R-R intervals
- Distinct P waves
- Variable ventricular rate
- Fibrillatory baseline waves
Correct Answer: Distinct P waves
Q15. A widened QRS (>120 ms) with right precordial ST-T changes and an rSR’ in V1 suggests:
- Left bundle branch block
- Right bundle branch block
- Hyperkalemia
- Anterior STEMI
Correct Answer: Right bundle branch block
Q16. Which calculation estimates heart rate on an ECG when rhythm is regular using large boxes?
- 1500 / number of small boxes between R waves
- 300 / number of large boxes between R waves
- 60 / PR interval
- Number of QRS complexes × 10
Correct Answer: 300 / number of large boxes between R waves
Q17. Electrical alternans (beat-to-beat variation in QRS amplitude) often suggests which clinical condition?
- Pulmonary embolism
- Pericardial effusion with cardiac tamponade
- Left ventricular hypertrophy
- Hypokalemia
Correct Answer: Pericardial effusion with cardiac tamponade
Q18. Which ECG change is classically associated with digitalis (digoxin) effect?
- ST segment scooping (downsloping) and shortened QT
- U waves and prolonged QT
- Delta waves and short PR
- Peaked T waves with wide QRS
Correct Answer: ST segment scooping (downsloping) and shortened QT
Q19. What does a prolonged QT interval predispose a patient to?
- Atrial flutter
- Torsades de pointes (polymorphic VT)
- Sinus bradycardia only
- Complete heart block
Correct Answer: Torsades de pointes (polymorphic VT)
Q20. Which lead shows the best view of the anterior wall of the left ventricle?
- V1–V4
- Leads II, III, aVF
- I and aVL
- V5–V6
Correct Answer: V1–V4
Q21. Which pattern indicates a left bundle branch block (LBBB)?
- QRS ≥120 ms with broad R waves in I, V5–V6 and absent Q in V5–V6
- rSR’ in V1 and wide S in V6
- Peaked T waves in all leads
- Short PR with delta wave
Correct Answer: QRS ≥120 ms with broad R waves in I, V5–V6 and absent Q in V5–V6
Q22. In Wolff-Parkinson-White (WPW) syndrome, which ECG feature is characteristic?
- Prolonged PR interval with deep Q waves
- Short PR interval and a delta wave
- Peaked P waves in inferior leads
- Diffuse ST elevation
Correct Answer: Short PR interval and a delta wave
Q23. Which condition commonly causes low voltage QRS complexes on ECG?
- Pericardial effusion or obesity
- Left ventricular hypertrophy
- Ventricular pre-excitation
- Right bundle branch block
Correct Answer: Pericardial effusion or obesity
Q24. Atrial rate around 250–350/min with a regular ventricular response and sawtooth waves indicates:
- Atrial fibrillation
- Atrial flutter with fixed block
- Multifocal atrial tachycardia
- Ventricular tachycardia
Correct Answer: Atrial flutter with fixed block
Q25. Which electrolyte abnormality is most likely when ECG shows flattened T waves and prominent U waves?
- Hyperkalemia
- Hypokalemia
- Hypercalcemia
- Hypermagnesemia
Correct Answer: Hypokalemia
Q26. What is the significance of a Q wave >40 ms or >25% of subsequent R wave in a lead?
- Normal variant
- Old transmural myocardial infarction (pathological Q wave)
- Acute pericarditis
- Hyperkalemia
Correct Answer: Old transmural myocardial infarction (pathological Q wave)
Q27. Which antiarrhythmic class primarily blocks sodium channels and widens QRS at higher doses?
- Class II (beta blockers)
- Class I (sodium channel blockers)
- Class III (potassium channel blockers)
- Class IV (calcium channel blockers)
Correct Answer: Class I (sodium channel blockers)
Q28. How is ventricular fibrillation recognized on ECG?
- Regular wide QRS complexes at ~150/min
- Chaotic irregular baseline with no identifiable QRS complexes
- Sawtooth atrial waves with regular ventricular response
- Prolonged PR interval with dropped beats
Correct Answer: Chaotic irregular baseline with no identifiable QRS complexes
Q29. Which ECG sign suggests right axis deviation?
- Positive QRS in lead I and negative in aVF
- Negative QRS in lead I and positive QRS in aVF
- Positive QRS in leads I and II
- Low voltage in limb leads
Correct Answer: Negative QRS in lead I and positive QRS in aVF
Q30. Which clinical intervention should a pharmacist be most concerned about when a drug prolongs the QT interval?
- Risk of torsades de pointes and review of interacting QT-prolonging medications
- Immediate discontinuation of all antihypertensives
- Routine administration of digoxin
- No concern unless QRS widens
Correct Answer: Risk of torsades de pointes and review of interacting QT-prolonging medications
I am a Registered Pharmacist under the Pharmacy Act, 1948, and the founder of PharmacyFreak.com. I hold a Bachelor of Pharmacy degree from Rungta College of Pharmaceutical Science and Research. With a strong academic foundation and practical knowledge, I am committed to providing accurate, easy-to-understand content to support pharmacy students and professionals. My aim is to make complex pharmaceutical concepts accessible and useful for real-world application.
Mail- Sachin@pharmacyfreak.com