ECG Multiple Choice Questions on Waves Intervals and Interpretation
ECG or Electrocardiograph is a test that is used to assess the Muscular and Electrical functionalities of the Heart. It is a painless test that can be conducted in a few minutes and results can also be read instantly. An Electrocardiograph is basically a graph of voltage plotted against the time of electrical activity of the heart.
The electrical activity of the heart - The Electrical System is the power source that makes the working of the heart possible in a Nutshell. The electrical impulses trigger the heartbeat that travels down a pathway through the heart. These pathways are conduction pathways and they are responsible for causing ventricles of the heart to contract and pump out blood. The human heart has a natural pacemaker that produces these electrical impulses all by itself. These electrical impulses generate an electrical current that spreads over our body. An electrocardiogram measures these currents in the form of wave graphs on paper.
The electrodes of the electrocardiogram are placed on the skin to note the normal working conditions of the heart. These electrodes detect the electrical impulses occurring during each heartbeat. The impulses are picked up from the changes in an electrical path on the skin. These changes arise from the heart muscles and the electrophysiologic patterns of depolarizing.
Let’s have a look at some solved Multiple-choice questions on ECG
MCQs on Electrocardiography or ECG
1. Who developed an Electrocardiogram?
Wilhelm His
Steward
Hubert Mann
Willem Einthoven
Answer: (d)
2. In the case of a normal Heartbeat, Depolarization stimulus arises in which of the following?
Epicardium
Sinoatrial Node (SA node)
Atrioventricular Node (AV node)
His bundle
Answer: (b)
3. What does the P wave represent?
Depolarization of the atria
Depolarization of the ventricles
Represents the repolarization of the ventricles
Depolarization of the atria and ventricles
Answer: (a)
4. Which of these cannot be detected by an Electrocardiogram?
The rate and rhythm of Heartbeats
The size and position of the Heart chambers
The function of implanted Pacemakers
Presence of asymptomatic blockages in the atria of the Heart
Answer: (d)
5. Which of the following indicates Ventricular Muscle Depolarization?
P wave
QRS complex
T wave
PR interval
Answer: (b)
6. What does the T wave represent in an ECG?
Atrial diastole
Atrial systole
Ventricular diastole
Joint diastole
Answer: (c)
7. What does the Depolarization of Ventricles initiate?
Atrial diastole
Atrial systole
Ventricular systole
Joint diastole
Answer: (c)
8. Counting the number of QRS complexes, which of the following can be interpreted?
Rate of heartbeat
Rate of breathing
Cardiac output
Stroke volume
Answer: (a)
9. What do Depolarization and Repolarization initiate in different chambers of the Heart?
Contraction and relaxation
Relaxation and contraction
Thickening and thinning
Contraction and thickening
Answer: (a)
10. Which of the following waves of ECG represent Repolarization?
P wave
QRS complex
RS wave
T wave
Answer: (d)
11. In a single circulation the Heart Pumps?
Oxygenated blood
Deoxygenated blood
Mixed blood
Only blood nutrients
Answer: (b)
12. The Depolarization Stimulus for the normal Heartbeat originates in the
Epicardium
His-bundle areas
Atrioventricular (AV) nodal
Sinoatrial (SA) node
Answer: (d)
13. A shortened PR interval, slurring (called a delta wave) of the initial QRS deflection, and prolonged QRS duration are characteristics of
Wolff-Parkinson-White (WPW) syndrome
B. Atrial tachycardia
C. Left bundle branch block
D. Myocardial ischemia
Answer: (a)
14. The classic ECG changes in Myocardial Infarction (MI. are
T-wave inversion
ST-segment elevation
Development of an abnormal Q wave
All of the above
Answer: (d)
15. ECG depicts the Depolarisation and Repolarisation processes during the Cardiac Cycle. In the ECG of a normal healthy individual one of the following waves is not represented, which one is that?
Depolarization of atria
Repolarization of atria
Depolarization of ventricles
Repolarization of ventricles
Answer: (b)
16. Which of the following correctly explains a phase/ event in cardiac cycle in a standard Electrocardiogram?
QRS complex indicates atrial contraction.
QRS complex indicates ventricular contraction.
Time between S and T represents atrial systole.
P-wave indicates beginning of ventricular contraction.
Answer: (b)
17. In a normal individual, the heart rate can be determined by the ___________ in an ECG
Interval between two QRS complexes
Number of P waves
Interval between the P and T waves
Number of T waves
Answer: (a)
18. This is the classic ECG change in MI (Myocardial Infarction.
ST-segment elevation
T-wave inversion
Development of an abnormal Q wave
All of these
Answer: (d)
19. In which of these conditions can widen QRS and Tall-tented T waves be observed
Hyponatremia
Hyperkalemia
Hyperglycemia
Hyperphosphatemia
Answer: (b)
20. A particular ECG change observed in Hypokalemia is
ST-segment elevation
U wave, which is a position deflection after the T wave
Tall peaked T waves
Widening of the QRS complex and increased amplitude
Answer: (b)
21. ECG identified by the PR interval tends to become longer with every succeeding ECG complex until there is a P wave not followed by a QRS is observed in
Third-Degree Atrioventricular Block
Second-Degree Atrioventricular Block, Type II
Second-Degree Atrioventricular Block, Type I
First-Degree Atrioventricular Block, Type II
Answer: (c)
22. The waves which represent the excitation of the atria are,
P-wave
QRS complex
T-wave
ST-segment
Answer: (a)
23. The depolarization of the ventricles is represented in,
P-wave
T-wave
QRS complex
PQ interval
Answer: (c)
24. The heartbeat of a person can be determined by which of the following waves?
P-wave
QRS complex
ST-segment
PQ interval
Answer: (b)
25. The enlargement of auricles is represented by,
Enlargement of P-wave
Enlargement of QR segment
Depression of ST segment
Elevation of ST segment
Answer: (a)
26. Depression of the ST segment depicts, which of the following?
Ischemia
Hypokalemia
Myocardial infarction
Acute heart attack
Answer: (a)
27. The longest refractory period is found in which of the following muscles?
Skeletal muscles
Smooth muscles
Cardiac muscles
Facial muscles
Answer: (c)
28. The full form of ECG is
Electricity cardiac group
Electrocardio group
Electrocardium granules
Electrocardiogram
Answer: (d)
29. AV block refers to
Impulse not reaching SA node
Impulse not reaching the AV node
Impulse not reaching Purkinje fibers
Impulse not generating in the heart
Answer: (b)
30. The major symptom of heart failure is
Lung congestion
Vomiting
Yellowing of eyes
Pain in the chest
Answer: (a)
31. The full form of CAD is
Coronary artery disease
Carotid artery disorder
Carotid artery disease
Coronary angina disorder
Answer: (a)
32. Immediately after the QRS wave, which of the phases of the cardiac cycle follows?
Isovolumic relaxation
Ventricular ejection
Atrial systole
Isovolumic contraction
Answer: (d)
33. The positive electrode when recording lead aVL on an EKG is
left arm
left leg
right leg
left arm + left leg
Answer: (a)
34. From an ECG of a horse, which of the following cannot be determined?
Heart rhythm
Heart rate
Ventricular enlargement presence
The duration of the P-R interval
Answer: (c)
35. Leads V3 and V4 represent which of the following views of the heart?
Septal
Inferior
Anterior
Lateral
Answer: (c)
36. A normal PR interval duration ranges between
0.04 - 0.12 seconds (small squares of 1-3)
0.12 - 0.2 seconds (small squares of 3-5)
0.04 - 0.08 seconds (small squares of 1-2)
0.08 - 0.12 seconds (small squares of 2-3)
Answer: (b)
37. If leads II, III, and aVF, note the ST-elevation, what would it suggest?
An inferior myocardial infarction
A posterior myocardial infarction
A septal myocardial infarction
An anterior myocardial infarction
Answer: (a)
38. Left axis deviation is caused due to
Defects of the conduction system
Atrial septal defects
Right ventricular hypertrophy
Left ventricular hypertrophy
Answer: (a)
39. QRS complex's normal duration is
0.04 seconds (1 small square)
0.08 seconds (2 small squares)
0.16 seconds (4 small squares)
0.12 seconds (3 small squares)
Answer: (d)
FAQs on MCQs on ECG with Detailed Answers and Explanations
1. What is ECG in biology?
An ECG (Electrocardiogram) is a graphical recording of the electrical activity of the heart over time. It is used to assess heart rhythm and detect cardiac abnormalities.
- It records electrical impulses generated during the cardiac cycle.
- It is obtained using electrodes placed on the skin.
- It helps diagnose arrhythmias, heart block, and myocardial infarction.
2. What are the different waves in an ECG?
The main waves in a normal ECG tracing are the P wave, QRS complex, and T wave. Each represents a specific electrical event in the heart.
- P wave: Atrial depolarization.
- QRS complex: Ventricular depolarization.
- T wave: Ventricular repolarization.
3. What does the P wave represent in an ECG?
The P wave represents the depolarization of the atria, which leads to atrial contraction. It is the first upward deflection seen in a normal ECG.
- It originates from the sinoatrial (SA) node.
- It indicates the spread of electrical impulse across both atria.
- Its absence or abnormal shape may suggest atrial disorders.
4. What is the QRS complex in an ECG?
The QRS complex represents ventricular depolarization, which triggers ventricular contraction. It is the most prominent part of the ECG tracing.
- It corresponds to the spread of impulse through the bundle of His and Purkinje fibers.
- Atrial repolarization occurs simultaneously but is hidden within it.
- A widened QRS complex may indicate conduction defects.
5. What does the T wave indicate in an ECG?
The T wave indicates ventricular repolarization, which is the recovery phase before the next heartbeat. It follows the QRS complex.
- It reflects relaxation of the ventricles.
- Abnormal T waves may indicate ischemia or electrolyte imbalance.
- It completes one electrical cycle of the ventricles.
6. What is the normal heart rate calculated from an ECG?
The normal heart rate calculated from an ECG is about 60–100 beats per minute in adults. It is determined by measuring the interval between successive R waves.
- Count the number of large squares between two R waves.
- Heart rate ≈ 300 divided by the number of large squares.
- Rates below 60 bpm indicate bradycardia; above 100 bpm indicate tachycardia.
7. What is the difference between depolarization and repolarization in ECG?
In an ECG, depolarization is the electrical activation of cardiac muscle, while repolarization is the return to the resting electrical state. Both are essential for a normal cardiac cycle.
- Depolarization: Causes muscle contraction (P wave and QRS complex).
- Repolarization: Leads to relaxation (T wave).
- They result from movement of ions like sodium and potassium across cardiac cell membranes.
8. What is the function of the SA node in ECG?
The sinoatrial (SA) node acts as the natural pacemaker of the heart and initiates the electrical impulse seen as the P wave in ECG. It controls the heart rate.
- Located in the right atrium.
- Generates rhythmic electrical impulses automatically.
- Sets the normal sinus rhythm of 60–100 beats per minute.
9. What is meant by a normal sinus rhythm in ECG?
A normal sinus rhythm is a regular heart rhythm that originates from the SA node and shows a normal pattern of P wave, QRS complex, and T wave. It indicates proper electrical conduction.
- Each P wave is followed by a QRS complex.
- Heart rate is between 60–100 bpm.
- Intervals and wave shapes are within normal limits.
10. Why is ECG important in diagnosing heart diseases?
An ECG is important because it helps detect abnormalities in heart rhythm, conduction, and muscle damage. It is a primary diagnostic tool in cardiology.
- Identifies arrhythmias and heart blocks.
- Detects myocardial infarction and ischemia.
- Monitors electrolyte imbalance and drug effects.
