Electrocardiogram (ECG) MCQs With Answer

Mastering Electrocardiogram (ECG) MCQs With Answer is essential for B. Pharm students preparing for clinical pharmacy, pharmacology, and therapeutics assessments. This focused ECG MCQ collection covers ECG basics, cardiac electrophysiology, lead placement, waveform recognition (P, QRS, T), intervals, arrhythmias, ischemic changes, and drug-induced ECG effects. Questions emphasize interpretation, rhythm analysis, conduction blocks, electrolyte influences, and how medicines alter ECG patterns—critical for safe drug therapy and monitoring. Regular practice with these targeted ECG questions will strengthen diagnostic reasoning, improve medication safety, and boost exam readiness. Now let’s test your knowledge with 50 MCQs on this topic.

Q1. What is the normal duration of the PR interval on a standard ECG?

• 120–200 ms
• 80–120 ms
• 200–300 ms
• Less than 80 ms

Correct Answer: 120–200 ms

Q2. Which waveform represents ventricular depolarization?

• P wave
• QRS complex
• T wave
• U wave

Correct Answer: QRS complex

Q3. Which lead is most useful for detecting inferior wall myocardial infarction?

• V1–V2
• V3–V4
• II, III, aVF
• I and aVL

Correct Answer: II, III, aVF

Q4. Tall peaked T waves on ECG are classically associated with which electrolyte disturbance?

• Hypokalemia
• Hyperkalemia
• Hypercalcemia
• Hypomagnesemia

Correct Answer: Hyperkalemia

Q5. Prolongation of the QT interval increases risk of which arrhythmia?

• Atrial fibrillation
• Ventricular fibrillation
• Torsades de pointes
• Sinus bradycardia

Correct Answer: Torsades de pointes

Q6. Which antiarrhythmic class is most associated with QT prolongation?

• Class I (Na+ channel blockers)
• Class II (β-blockers)
• Class III (K+ channel blockers)
• Class IV (Ca2+ channel blockers)

Correct Answer: Class III (K+ channel blockers)

Q7. Which lead shows septal Q waves typically?

• V1 and V2
• V5 and V6
• V3 and V4
• II and III

Correct Answer: V1 and V2

Q8. A widened QRS complex (>120 ms) most commonly indicates which problem?

• Left atrial enlargement
• Ventricular conduction delay (bundle branch block)
• Early repolarization
• Sinus tachycardia

Correct Answer: Ventricular conduction delay (bundle branch block)

Q9. Which ECG change is typical in acute transmural myocardial infarction?

• ST-segment elevation in corresponding leads
• Global T-wave flattening
• Prominent U waves
• Shortened PR interval

Correct Answer: ST-segment elevation in corresponding leads

Q10. Which drug is associated with characteristic ‘scooped’ ST segment depression and flattened T waves?

• Digoxin
• Lidocaine
• Propranolol
• Amiodarone

Correct Answer: Digoxin

Q11. A saw-tooth pattern on ECG with regular atrial activity most likely indicates:

• Atrial fibrillation
• Atrial flutter
• Multifocal atrial tachycardia
• Ventricular tachycardia

Correct Answer: Atrial flutter

Q12. Which lead axis deviation is suggested by positive QRS in lead I and negative QRS in lead aVF?

• Normal axis
• Left axis deviation
• Right axis deviation
• Extreme axis deviation

Correct Answer: Left axis deviation

Q13. Which ECG finding suggests hypercalcemia?

• Prolonged QT interval
• Shortened QT interval
• Peaked T waves
• U waves

Correct Answer: Shortened QT interval

Q14. What is the primary pacemaker of the heart seen on ECG as the origin of P waves?

• Atrioventricular (AV) node
• Sinoatrial (SA) node
• Bundle of His
• Purkinje fibers

Correct Answer: Sinoatrial (SA) node

Q15. Which ECG sign is strongly suggestive of left ventricular hypertrophy (LVH)?

• Low voltage QRS in all leads
• Right axis deviation
• Large R wave in V5 or V6 with deep S in V1
• ST elevation in inferior leads

Correct Answer: Large R wave in V5 or V6 with deep S in V1

Q16. Which change is typically seen with digitalis toxicity?

• Short PR interval without other changes
• ST depression with ‘scooped’ appearance and increased PR interval
• Widespread ST elevation
• U waves and prolonged QTc

Correct Answer: ST depression with ‘scooped’ appearance and increased PR interval

Q17. Which condition causes prominent U waves on ECG?

• Hyperkalemia
• Hypokalemia
• Hypercalcemia
• Hypocalcemia

Correct Answer: Hypokalemia

Q18. Which lead(s) form the augmented limb leads?

• V1–V6
• I, II, III
• aVR, aVL, aVF
• V4–V6 only

Correct Answer: aVR, aVL, aVF

Q19. In complete heart block (third-degree AV block), the ECG shows:

• Prolonged PR interval with every P followed by QRS
• No relationship between P waves and QRS complexes (AV dissociation)
• Short PR interval and delta waves
• Saw-tooth atrial activity

Correct Answer: No relationship between P waves and QRS complexes (AV dissociation)

Q20. Which antiarrhythmic is most likely to cause torsades de pointes?

• Metoprolol
• Amiodarone (short term less likely)
• Sotalol
• Verapamil

Correct Answer: Sotalol

Q21. Which lead placement is incorrect for a standard 12-lead ECG?

• V1 at 4th intercostal space right sternal border
• V2 at 4th intercostal space left sternal border
• V4 at 5th intercostal space mid-clavicular line
• V6 at 5th intercostal space mid-sternal line

Correct Answer: V6 at 5th intercostal space mid-sternal line

Q22. What does a pathologic Q wave usually indicate?

• Recent pulmonary embolism
• Prior transmural myocardial infarction
• Normal variant in young adults
• Pericarditis

Correct Answer: Prior transmural myocardial infarction

Q23. Early repolarization pattern is most commonly seen in which group?

• Older patients with coronary disease
• Young healthy adults, especially athletes
• Patients with hyperkalemia
• Patients on digoxin therapy

Correct Answer: Young healthy adults, especially athletes

Q24. Which ECG finding is typical of pericarditis?

• Localized ST elevation with reciprocal changes
• Diffuse ST elevation and PR segment depression
• Deep Q waves in anterior leads
• Peaked T waves in all leads

Correct Answer: Diffuse ST elevation and PR segment depression

Q25. Which of the following drugs can prolong the QT interval?

• Macrolide antibiotics (e.g., erythromycin)
• Metformin
• Acetaminophen
• Heparin

Correct Answer: Macrolide antibiotics (e.g., erythromycin)

Q26. Which rhythm is characterized by irregularly irregular R-R intervals and absent distinct P waves?

• Atrial flutter
• Atrial fibrillation
• Multifocal atrial tachycardia
• Sinus arrhythmia

Correct Answer: Atrial fibrillation

Q27. What does a left bundle branch block (LBBB) typically show in leads V5–V6?

• Q waves in V5–V6
• Broad, notched R waves in V5–V6
• Small R waves and deep S waves
• Peaked T waves only

Correct Answer: Broad, notched R waves in V5–V6

Q28. In ECG, QTc is corrected QT for heart rate. Which formula is commonly used for QT correction?

• Fick equation
• Henderson-Hasselbalch
• Bazett’s formula
• Fick-Bazett combined formula

Correct Answer: Bazett’s formula

Q29. Which ECG change suggests acute posterior myocardial infarction?

• ST elevation in V1–V3
• Tall R waves and ST depression in V1–V3
• Deep Q waves in II, III
• Diffuse PR depression

Correct Answer: Tall R waves and ST depression in V1–V3

Q30. Which electrolyte abnormality is commonly associated with prolonged PR interval and peaked T waves?

• Hyperkalemia
• Hypokalemia
• Hypernatremia
• Hypocalcemia

Correct Answer: Hyperkalemia

Q31. Which drug class can cause bradycardia and PR prolongation on ECG?

• Beta-blockers
• Loop diuretics
• Thiazide diuretics
• ACE inhibitors

Correct Answer: Beta-blockers

Q32. Which of the following features differentiates supraventricular tachycardia (SVT) from ventricular tachycardia?

• Wide QRS complex always indicates SVT
• Presence of concordance across precordial leads always indicates SVT
• Narrow QRS with rapid rate often suggests SVT
• Absence of P waves always indicates SVT

Correct Answer: Narrow QRS with rapid rate often suggests SVT

Q33. Which ECG finding suggests right ventricular hypertrophy (RVH)?

• Tall R waves in V1 and right axis deviation
• Deep S waves in V1 and left axis deviation
• Low voltage QRS in limb leads
• Diffuse ST elevation

Correct Answer: Tall R waves in V1 and right axis deviation

Q34. Which condition is associated with Osborne (J) waves on the ECG?

• Hyperthyroidism
• Hypothermia
• Hyperkalemia
• Pericarditis

Correct Answer: Hypothermia

Q35. Which ECG change is commonly seen with acute pulmonary embolism?

• New right bundle branch block and S1Q3T3 pattern
• Diffuse ST elevation
• Peaked T waves in lateral leads
• Pathologic Q waves in inferior leads

Correct Answer: New right bundle branch block and S1Q3T3 pattern

Q36. In which situation would you expect a shortened PR interval with a delta wave?

• Wolff-Parkinson-White (WPW) syndrome
• AV nodal reentrant tachycardia
• Complete heart block
• Pericarditis

Correct Answer: Wolff-Parkinson-White (WPW) syndrome

Q37. What does low voltage QRS complexes in all leads suggest?

• Pleural effusion or pericardial effusion
• Left ventricular hypertrophy
• Acute anterior MI
• Hyperkalemia

Correct Answer: Pleural effusion or pericardial effusion

Q38. Which ECG finding indicates atrial enlargement?

• Broad, notched P waves in lead II suggest left atrial enlargement
• Peaked T waves indicate left atrial enlargement
• Short PR interval indicates right atrial enlargement
• High-voltage QRS indicates atrial enlargement

Correct Answer: Broad, notched P waves in lead II suggest left atrial enlargement

Q39. Which class of drugs can cause PR prolongation by slowing AV nodal conduction?

• Class IA antiarrhythmics
• Calcium channel blockers (non-dihydropyridine)
• Loop diuretics
• Statins

Correct Answer: Calcium channel blockers (non-dihydropyridine)

Q40. Which ECG parameter is used to estimate ventricular rate in atrial fibrillation on a regular 6-second strip?

• Number of P waves ×10
• Number of QRS complexes ×10
• PR interval ×6
• QT interval ×5

Correct Answer: Number of QRS complexes ×10

Q41. Brugada syndrome is identified by which ECG pattern?

• Diffuse ST depression in all leads
• ST elevation in V1–V3 with coved-type morphology
• Low voltage QRS and electrical alternans
• Peaked T waves and short QT interval

Correct Answer: ST elevation in V1–V3 with coved-type morphology

Q42. Which of the following best describes electrical alternans?

• Beat-to-beat variation in QRS amplitude, often due to large pericardial effusion
• Alternating PR intervals with constant QRS
• Fixed ST elevation in anterior leads
• Alternating axis deviation on serial ECGs

Correct Answer: Beat-to-beat variation in QRS amplitude, often due to large pericardial effusion

Q43. A patient on class IA antiarrhythmic shows widened QRS and prolonged QT. Which drug belongs to class IA?

• Amiodarone
• Procainamide
• Propranolol
• Flecainide

Correct Answer: Procainamide

Q44. Which of the following indicates ischemia rather than infarction on ECG?

• Pathologic Q waves
• ST-segment elevation with reciprocal changes
• ST-segment depression and/or T-wave inversion
• Persistent QRS widening

Correct Answer: ST-segment depression and/or T-wave inversion

Q45. Which lead is most directly over the right ventricle?

• V1
• V3
• V5
• V6

Correct Answer: V1

Q46. Which statement about paced rhythms on ECG is true?

• Ventricular pacing produces a narrow QRS complex
• Atrial pacing produces absent P waves
• Ventricular pacing typically produces a wide QRS with a pacing spike before the QRS
• Pacemaker spikes are only seen on invasive monitoring

Correct Answer: Ventricular pacing typically produces a wide QRS with a pacing spike before the QRS

Q47. In which lead would ST elevation reflect lateral wall myocardial infarction?

• V1–V2
• II, III
• V5–V6 and I, aVL
• V3R–V4R

Correct Answer: V5–V6 and I, aVL

Q48. Which pharmacologic agent is useful acutely for terminating reentrant supraventricular tachycardia by transient AV nodal block?

• Adenosine
• Atropine
• Isoproterenol
• Amiodarone

Correct Answer: Adenosine

Q49. What ECG change is associated with severe hypokalemia?

• Peaked T waves and shortened QT
• Prominent U waves, ST depression, and flattened T waves
• Widened QRS and peaked T waves
• Shortened PR interval and delta waves

Correct Answer: Prominent U waves, ST depression, and flattened T waves

Q50. Which concept is important when interpreting an ECG in a B. Pharm clinical setting?

• ECG interpretation is irrelevant to drug safety
• Recognizing drug-induced ECG changes and electrolyte causes is essential for medication management
• Only cardiologists need to know ECG basics
• ECG changes never influence dosing decisions

Correct Answer: Recognizing drug-induced ECG changes and electrolyte causes is essential for medication management

G S Sachin

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