The electrocardiogram (ECG or EKG) is an indispensable, non-invasive diagnostic tool that provides a graphical representation of the heart’s electrical activity. For healthcare professionals, including pharmacists, a fundamental understanding of ECG principles, lead placement, normal waveforms, and basic interpretation is crucial for assessing cardiac function, identifying arrhythmias, evaluating the effects of cardiovascular drugs, and contributing to overall patient management. This MCQ quiz is designed to test your foundational knowledge of electrocardiology, paving the way for more advanced ECG interpretation.
1. An electrocardiogram (ECG) is a recording of the:
- A. Mechanical contractile activity of the heart.
- B. Blood flow through the coronary arteries.
- C. Electrical activity generated by the heart during depolarization and repolarization.
- D. Heart sounds associated with valve closure.
Answer: C. Electrical activity generated by the heart during depolarization and repolarization.
2. The P wave on a normal ECG represents:
- A. Ventricular depolarization
- B. Ventricular repolarization
- C. Atrial depolarization
- D. Atrial repolarization
Answer: C. Atrial depolarization
3. The QRS complex on a normal ECG represents:
- A. Atrial depolarization
- B. Atrial repolarization
- C. Ventricular depolarization
- D. Ventricular repolarization
Answer: C. Ventricular depolarization
4. The T wave on a normal ECG represents:
- A. Atrial depolarization
- B. Ventricular depolarization
- C. Atrial repolarization
- D. Ventricular repolarization
Answer: D. Ventricular repolarization
5. The PR interval on a normal ECG measures the time from the:
- A. Beginning of ventricular depolarization to the end of ventricular repolarization.
- B. Beginning of atrial depolarization (P wave) to the beginning of ventricular depolarization (QRS complex).
- C. End of atrial depolarization to the beginning of ventricular depolarization.
- D. Duration of the QRS complex.
Answer: B. Beginning of atrial depolarization (P wave) to the beginning of ventricular depolarization (QRS complex).
6. Which part of the ECG represents the delay of the electrical impulse at the atrioventricular (AV) node?
- A. The P wave
- B. The PR segment (the latter part of the PR interval)
- C. The QRS complex
- D. The T wave
Answer: B. The PR segment (the latter part of the PR interval)
7. The standard limb leads (I, II, and III) are described as:
- A. Unipolar leads
- B. Precordial leads
- C. Bipolar leads
- D. Augmented leads
Answer: C. Bipolar leads
8. Lead II of the standard limb leads records the potential difference between which two limbs?
- A. Right arm and left arm
- B. Right arm and left leg
- C. Left arm and left leg
- D. Right leg and right arm
Answer: B. Right arm and left leg
9. The augmented limb leads (aVR, aVL, aVF) are:
- A. Bipolar leads measuring potential between two active electrodes.
- B. Unipolar leads measuring potential at one limb relative to a composite reference point.
- C. Chest leads.
- D. Esophageal leads.
Answer: B. Unipolar leads measuring potential at one limb relative to a composite reference point.
10. The precordial (chest) leads (V1-V6) primarily view the heart’s electrical activity in which plane?
- A. Frontal plane
- B. Sagittal plane
- C. Horizontal (transverse) plane
- D. Coronal plane
Answer: C. Horizontal (transverse) plane
11. On standard ECG paper, what does one small square (1 mm) typically represent in time if the paper speed is 25 mm/second?
- A. 0.02 seconds
- B. 0.04 seconds
- C. 0.10 seconds
- D. 0.20 seconds
Answer: B. 0.04 seconds
12. On standard ECG paper, what does one large square (5 mm) typically represent in time if the paper speed is 25 mm/second?
- A. 0.04 seconds
- B. 0.10 seconds
- C. 0.20 seconds
- D. 1.00 second
Answer: C. 0.20 seconds
13. The standard calibration for an ECG is typically 1 mV of electrical activity producing a deflection of:
- A. 1 mm (1 small square)
- B. 5 mm (1 large square)
- C. 10 mm (2 large squares)
- D. 20 mm (4 large squares)
Answer: C. 10 mm (2 large squares)
14. Which leads are typically used to assess the inferior wall of the left ventricle?
- A. Leads I and aVL
- B. Leads V1 and V2
- C. Leads II, III, and aVF
- D. Leads V5 and V6
Answer: C. Leads II, III, and aVF
15. Leads V1 and V2 are best positioned to view the electrical activity of the:
- A. Lateral wall of the left ventricle
- B. Inferior wall of the left ventricle
- C. Septum and right ventricle
- D. Posterior wall of the left ventricle
Answer: C. Septum and right ventricle
16. The normal duration of the PR interval in an adult is typically:
- A. Less than 0.10 seconds
- B. 0.12 to 0.20 seconds (3 to 5 small squares)
- C. 0.20 to 0.28 seconds
- D. Greater than 0.30 seconds
Answer: B. 0.12 to 0.20 seconds (3 to 5 small squares)
17. The normal duration of the QRS complex in an adult is typically:
- A. 0.12 to 0.20 seconds
- B. Greater than 0.20 seconds
- C. Less than 0.12 seconds (often 0.06 to 0.10 seconds)
- D. 0.02 to 0.04 seconds
Answer: C. Less than 0.12 seconds (often 0.06 to 0.10 seconds)
18. The ST segment on an ECG normally should be:
- A. Elevated by at least 2 mm
- B. Depressed by at least 2 mm
- C. Isoelectric (at the same level as the baseline TP segment or PR segment)
- D. Inverted in all leads
Answer: C. Isoelectric (at the same level as the baseline TP segment or PR segment)
19. The QT interval represents the total duration of:
- A. Atrial depolarization only
- B. Ventricular depolarization and repolarization
- C. AV nodal delay
- D. The cardiac cycle
Answer: B. Ventricular depolarization and repolarization
20. Because the QT interval varies with heart rate, it is often corrected (QTc). Which formula is commonly used for this correction?
- A. Einthoven’s formula
- B. Bazett’s formula (QTc = QT / √RR)
- C. Nernst equation
- D. Frank-Starling law
Answer: B. Bazett’s formula (QTc = QT / √RR)
21. A prolonged QTc interval is a risk factor for which potentially life-threatening arrhythmia?
- A. Atrial fibrillation
- B. Sinus bradycardia
- C. Torsades de Pointes (a type of polymorphic ventricular tachycardia)
- D. First-degree AV block
Answer: C. Torsades de Pointes (a type of polymorphic ventricular tachycardia)
22. To calculate the heart rate from an ECG with a regular rhythm, one common method is to divide 300 by the number of:
- A. Small squares between two consecutive R waves.
- B. Large squares between two consecutive R waves.
- C. QRS complexes in a 6-second strip.
- D. P waves in a 10-second strip.
Answer: B. Large squares between two consecutive R waves. (Or 1500 divided by the number of small squares).
23. If the rhythm is irregular, the heart rate can be estimated by counting the number of QRS complexes in a __________ strip and multiplying by __________.
- A. 3-second; 20
- B. 6-second; 10
- C. 10-second; 10
- D. 1-minute; 1
Answer: B. 6-second; 10 (A 6-second strip is 30 large squares).
24. Einthoven’s Law states that:
- A. Lead I + Lead II = Lead III
- B. Lead I + Lead III = Lead II
- C. Lead II + Lead III = Lead I
- D. aVR + aVL + aVF = 0
Answer: B. Lead I + Lead III = Lead II
25. The atrial repolarization wave (Ta wave) is usually:
- A. A prominent upright wave after the T wave.
- B. A large negative wave before the P wave.
- C. Not visible or obscured by the QRS complex on a standard ECG.
- D. Identical in morphology to the P wave.
Answer: C. Not visible or obscured by the QRS complex on a standard ECG.
26. The J point on an ECG is the:
- A. Beginning of the P wave.
- B. Peak of the R wave.
- C. Junction between the end of the QRS complex and the beginning of the ST segment.
- D. End of the T wave.
Answer: C. Junction between the end of the R_S wave and the beginning of the ST segment. (More accurately, end of QRS, beginning of ST).
27. Which lead is placed at the 4th intercostal space, right sternal border?
- A. V1
- B. V2
- C. V3
- D. V4
Answer: A. V1
28. Which lead is placed at the 5th intercostal space, midclavicular line?
- A. V2
- B. V3
- C. V4
- D. V5
Answer: C. V4
29. Depolarization moving towards a positive electrode on an ECG will produce a(n):
- A. Negative deflection
- B. Positive deflection
- C. Isoelectric line
- D. Biphasic deflection
Answer: B. Positive deflection
30. Repolarization moving away from a positive electrode on an ECG will typically produce a(n):
- A. Negative deflection
- B. Positive deflection
- C. Isoelectric line
- D. No deflection
Answer: B. Positive deflection (Ventricular repolarization normally proceeds from epicardium to endocardium, opposite to depolarization, but because it’s a wave of negative charges moving away OR positive charges moving towards the effective negative end of the dipole, it results in an upright T wave in leads with upright QRS). More simply, T wave is usually concordant with QRS.
31. The electrical axis of the heart refers to the:
- A. Physical orientation of the heart in the chest.
- B. Predominant direction of ventricular depolarization in the frontal plane.
- C. Speed of conduction through the AV node.
- D. Strength of atrial contraction.
Answer: B. Predominant direction of ventricular depolarization in the frontal plane.
32. A normal QRS axis in an adult is typically between:
- A. 0° and +180°
- B. -30° and +90° (or +105° by some definitions)
- C. +90° and +180° (Right Axis Deviation)
- D. -30° and -90° (Left Axis Deviation)
Answer: B. -30° and +90° (or +105° by some definitions)
33. Which of the following can cause artifact on an ECG tracing?
- A. Patient movement or muscle tremor
- B. Correct lead placement
- C. Normal sinus rhythm
- D. A properly calibrated ECG machine
Answer: A. Patient movement or muscle tremor
34. The U wave, when present on an ECG, is a small deflection that typically follows the:
- A. P wave
- B. QRS complex
- C. T wave
- D. It precedes the P wave
Answer: C. T wave
35. The main function of the AV node in cardiac conduction is to:
- A. Initiate the heartbeat.
- B. Rapidly conduct the impulse from the atria to the ventricles.
- C. Delay the electrical impulse from the atria before it passes to the ventricles, allowing time for atrial contraction to complete.
- D. Repolarize the ventricles.
Answer: C. Delay the electrical impulse from the atria before it passes to the ventricles, allowing time for atrial contraction to complete.
36. The His-Purkinje system is responsible for:
- A. Slowing conduction to the ventricles.
- B. Rapidly and synchronously depolarizing the ventricular myocardium.
- C. Initiating atrial depolarization.
- D. Repolarizing the atria.
Answer: B. Rapidly and synchronously depolarizing the ventricular myocardium.
37. What does a Q wave on an ECG represent if it is the first negative deflection of the QRS complex?
- A. Atrial repolarization
- B. Initial phase of ventricular depolarization, often septal depolarization (small Qs in some leads are normal)
- C. Ventricular repolarization
- D. AV nodal delay
Answer: B. Initial phase of ventricular depolarization, often septal depolarization (small Qs in some leads are normal)
38. Pathological Q waves (deep and wide) on an ECG can indicate:
- A. Acute ischemia
- B. Previous myocardial infarction (necrosis)
- C. Ventricular hypertrophy
- D. Pericarditis
Answer: B. Previous myocardial infarction (necrosis)
39. In a normal ECG, the R wave progression in the precordial leads means that the R wave amplitude should:
- A. Gradually decrease from V1 to V6.
- B. Gradually increase from V1 to V4/V5, then may decrease in V6.
- C. Remain constant across all precordial leads.
- D. Be absent in V1-V3.
Answer: B. Gradually increase from V1 to V4/V5, then may decrease in V6.
40. The term “isoelectric line” on an ECG refers to the:
- A. Peak of the R wave
- B. Baseline of the ECG, representing no net electrical activity being detected
- C. Nadir of the S wave
- D. Duration of the QT interval
Answer: B. Baseline of the ECG, representing no net electrical activity being detected (typically the TP segment).
41. What is the primary purpose of applying conductive gel or pads when placing ECG electrodes on a patient’s skin?
- A. To cool the skin
- B. To reduce skin impedance and improve electrical signal conduction to the electrodes
- C. To prevent allergic reactions
- D. To make the electrodes stick better only
Answer: B. To reduce skin impedance and improve electrical signal conduction to the electrodes
42. The TP segment on an ECG (from the end of the T wave to the beginning of the next P wave) is important because it often represents the:
- A. Period of maximal myocardial ischemia.
- B. True electrical baseline (isoelectric line) of the ECG.
- C. Peak of ventricular contraction.
- D. Onset of atrial repolarization.
Answer: B. True electrical baseline (isoelectric line) of the ECG.
43. Which limb electrode serves as the ground (reference) electrode in a standard 12-lead ECG setup and is not directly involved in forming the limb or augmented leads?
- A. Left arm
- B. Right arm
- C. Left leg
- D. Right leg
Answer: D. Right leg
44. A “sinus rhythm” on an ECG implies that the:
- A. Heart rate is always between 60-100 bpm.
- B. QRS complexes are narrow.
- C. Electrical impulse originates in the SA node, and is characterized by upright P waves in lead II preceding every QRS.
- D. T waves are inverted.
Answer: C. Electrical impulse originates in the SA node, and is characterized by upright P waves in lead II preceding every QRS.
45. If the R-R interval on an ECG is consistently 4 large squares, what is the heart rate?
- A. 60 bpm
- B. 75 bpm
- C. 100 bpm
- D. 150 bpm
Answer: B. 75 bpm (300 / 4 = 75).
46. Which physiological event is NOT directly visible on a standard surface ECG?
- A. Atrial depolarization
- B. Ventricular depolarization
- C. Atrial repolarization (usually obscured by QRS)
- D. Ventricular repolarization
Answer: C. Atrial repolarization (usually obscured by QRS)
47. An abnormally short PR interval (<0.12 seconds) with a delta wave may suggest:
- A. First-degree AV block
- B. Ventricular pre-excitation (e.g., Wolff-Parkinson-White syndrome)
- C. Sinus bradycardia
- D. Bundle branch block
Answer: B. Ventricular pre-excitation (e.g., Wolff-Parkinson-White syndrome)
48. The main difference between the limb leads and precordial leads is that:
- A. Limb leads measure electrical activity in the horizontal plane, while precordial leads measure in the frontal plane.
- B. Limb leads measure electrical activity in the frontal plane, while precordial leads measure in the horizontal plane.
- C. Limb leads are unipolar, while precordial leads are bipolar.
- D. Precordial leads are only used for pediatric patients.
Answer: B. Limb leads measure electrical activity in the frontal plane, while precordial leads measure in the horizontal plane.
49. What does “calibration pulse” on an ECG signify?
- A. The patient’s heart rate
- B. A standard 1 mV signal used to check the ECG machine’s sensitivity (should produce a 10 mm deflection)
- C. The start of the ECG recording
- D. An electrical artifact
Answer: B. A standard 1 mV signal used to check the ECG machine’s sensitivity (should produce a 10 mm deflection)
50. Understanding the basics of electrocardiology is crucial for pharmacists primarily to:
- A. Perform cardiac catheterizations.
- B. Prescribe antiarrhythmic medications independently.
- C. Recognize normal ECG patterns, identify potential drug-induced ECG changes (e.g., QT prolongation, bradycardia), and contribute to the safe and effective use of cardiovascular medications.
- D. Interpret complex Holter monitor recordings without cardiologist input.
Answer: C. Recognize normal ECG patterns, identify potential drug-induced ECG changes (e.g., QT prolongation, bradycardia), and contribute to the safe and effective use of cardiovascular medications.