,Question 1
Which component of an electrocardiogram (ECG) represents ventricular depolarization?
A. P wave B. QRS complex C. T wave D. U wave
Correct answer: B. QRS complex.
Rationale: The QRS complex represents electrical depolarization of the ventricles, which
precedes ventricular contraction. The P wave represents atrial depolarization, while the T wave
represents ventricular repolarization.
Question 2
Which ECG component represents atrial depolarization?
A. P wave B. QRS complex C. ST segment D. T wave
Correct answer: A. P wave.
Rationale: The P wave reflects the spread of electrical activation through the atria. Its shape,
presence, and relationship to the QRS complex help determine whether the rhythm originates
from the sinus node or another atrial or junctional source.
Question 3
What does the PR interval measure?
A. Ventricular repolarization time B. Time from the beginning of atrial depolarization to the
beginning of ventricular depolarization C. Duration of ventricular contraction D. Time between
two consecutive R waves
Correct answer: B.
Rationale: The PR interval extends from the beginning of the P wave to the beginning of the
QRS complex. It reflects conduction from the atria through the AV node and the His-Purkinje
system. A typical adult PR interval is 0.12–0.20 seconds.
Question 4
What is the usual duration of a normal adult QRS complex?
A. 0.01–0.02 seconds B. 0.06–0.10 seconds C. 0.20–0.30 seconds D. 0.40–0.50 seconds
Correct answer: B. 0.06–0.10 seconds.
,Rationale: A normal QRS complex is generally less than 0.12 seconds. A QRS duration of 0.12
seconds or greater is considered wide and may reflect bundle branch block, ventricular origin, or
abnormal intraventricular conduction.
Question 5
Which rhythm is characterized by a regular rate, normal sinus P waves, and a typical adult heart
rate of 60–100 beats per minute?
A. Atrial fibrillation B. Normal sinus rhythm C. Ventricular fibrillation D. Complete heart block
Correct answer: B. Normal sinus rhythm.
Rationale: Normal sinus rhythm originates in the sinus node. It typically has a rate of 60–100
beats per minute in adults, a P wave before each QRS, consistent PR intervals, and regular R–R
intervals.
Question 6
An adult patient has a heart rate of 48 beats per minute, with a P wave before each QRS and a
consistent PR interval. Which rhythm is most likely?
A. Sinus tachycardia B. Sinus bradycardia C. Atrial flutter D. Ventricular tachycardia
Correct answer: B. Sinus bradycardia.
Rationale: Sinus bradycardia is a sinus rhythm with a rate below 60 beats per minute in adults. It
may be normal during sleep or in trained athletes, but it can also occur with medications,
ischemia, or conduction-system disease. Clinical significance depends on symptoms and
hemodynamic status.
Question 7
An adult patient has a regular heart rate of 118 beats per minute. Normal sinus P waves precede
every QRS. Which rhythm is most likely?
A. Sinus tachycardia B. Ventricular fibrillation C. Complete heart block D. Asystole
Correct answer: A. Sinus tachycardia.
Rationale: Sinus tachycardia is a sinus rhythm with a rate above 100 beats per minute in adults.
Common causes include fever, pain, anxiety, dehydration, anemia, hypoxia, and physiological
stress. Treatment generally focuses on the underlying cause.
Question 8
, Which ECG finding is most characteristic of atrial fibrillation?
A. Regular P waves before every QRS B. Irregularly irregular ventricular rhythm with no
consistent discrete P waves C. A single premature QRS after every fourth beat D. A regular
rhythm with progressively lengthening PR intervals
Correct answer: B.
Rationale: Atrial fibrillation is characterized by disorganized atrial electrical activity and an
irregularly irregular ventricular response when AV conduction is present. It increases the risk of
thromboembolic stroke and may require rate or rhythm management and assessment for
anticoagulation.
Question 9
A patient has a regular narrow-complex tachycardia at approximately 180 beats per minute. P
waves are difficult to identify. Which rhythm is a common possibility?
A. Supraventricular tachycardia B. Sinus bradycardia C. Asystole D. First-degree AV block
Correct answer: A. Supraventricular tachycardia.
Rationale: Some forms of supraventricular tachycardia produce a rapid, regular, narrow-complex
rhythm with P waves hidden within or close to the QRS complexes. The differential diagnosis
includes atrial tachycardia and atrial flutter with fixed conduction. Clinical assessment and a 12-
lead ECG can help distinguish them.
Question 10
Which rhythm is most commonly associated with a sawtooth pattern of atrial activity?
A. Atrial flutter B. Ventricular fibrillation C. Sinus arrhythmia D. Junctional escape rhythm
Correct answer: A. Atrial flutter.
Rationale: Atrial flutter commonly produces organized flutter waves, especially visible in the
inferior ECG leads. The atrial rate is often approximately 250–350 beats per minute, while the
ventricular rate depends on AV conduction.
Question 11
What is a premature ventricular contraction (PVC)?
A. An early electrical impulse arising from the ventricles B. A normal P wave occurring late C.
A complete absence of electrical activity D. A delayed sinus impulse with a normal QRS
Which component of an electrocardiogram (ECG) represents ventricular depolarization?
A. P wave B. QRS complex C. T wave D. U wave
Correct answer: B. QRS complex.
Rationale: The QRS complex represents electrical depolarization of the ventricles, which
precedes ventricular contraction. The P wave represents atrial depolarization, while the T wave
represents ventricular repolarization.
Question 2
Which ECG component represents atrial depolarization?
A. P wave B. QRS complex C. ST segment D. T wave
Correct answer: A. P wave.
Rationale: The P wave reflects the spread of electrical activation through the atria. Its shape,
presence, and relationship to the QRS complex help determine whether the rhythm originates
from the sinus node or another atrial or junctional source.
Question 3
What does the PR interval measure?
A. Ventricular repolarization time B. Time from the beginning of atrial depolarization to the
beginning of ventricular depolarization C. Duration of ventricular contraction D. Time between
two consecutive R waves
Correct answer: B.
Rationale: The PR interval extends from the beginning of the P wave to the beginning of the
QRS complex. It reflects conduction from the atria through the AV node and the His-Purkinje
system. A typical adult PR interval is 0.12–0.20 seconds.
Question 4
What is the usual duration of a normal adult QRS complex?
A. 0.01–0.02 seconds B. 0.06–0.10 seconds C. 0.20–0.30 seconds D. 0.40–0.50 seconds
Correct answer: B. 0.06–0.10 seconds.
,Rationale: A normal QRS complex is generally less than 0.12 seconds. A QRS duration of 0.12
seconds or greater is considered wide and may reflect bundle branch block, ventricular origin, or
abnormal intraventricular conduction.
Question 5
Which rhythm is characterized by a regular rate, normal sinus P waves, and a typical adult heart
rate of 60–100 beats per minute?
A. Atrial fibrillation B. Normal sinus rhythm C. Ventricular fibrillation D. Complete heart block
Correct answer: B. Normal sinus rhythm.
Rationale: Normal sinus rhythm originates in the sinus node. It typically has a rate of 60–100
beats per minute in adults, a P wave before each QRS, consistent PR intervals, and regular R–R
intervals.
Question 6
An adult patient has a heart rate of 48 beats per minute, with a P wave before each QRS and a
consistent PR interval. Which rhythm is most likely?
A. Sinus tachycardia B. Sinus bradycardia C. Atrial flutter D. Ventricular tachycardia
Correct answer: B. Sinus bradycardia.
Rationale: Sinus bradycardia is a sinus rhythm with a rate below 60 beats per minute in adults. It
may be normal during sleep or in trained athletes, but it can also occur with medications,
ischemia, or conduction-system disease. Clinical significance depends on symptoms and
hemodynamic status.
Question 7
An adult patient has a regular heart rate of 118 beats per minute. Normal sinus P waves precede
every QRS. Which rhythm is most likely?
A. Sinus tachycardia B. Ventricular fibrillation C. Complete heart block D. Asystole
Correct answer: A. Sinus tachycardia.
Rationale: Sinus tachycardia is a sinus rhythm with a rate above 100 beats per minute in adults.
Common causes include fever, pain, anxiety, dehydration, anemia, hypoxia, and physiological
stress. Treatment generally focuses on the underlying cause.
Question 8
, Which ECG finding is most characteristic of atrial fibrillation?
A. Regular P waves before every QRS B. Irregularly irregular ventricular rhythm with no
consistent discrete P waves C. A single premature QRS after every fourth beat D. A regular
rhythm with progressively lengthening PR intervals
Correct answer: B.
Rationale: Atrial fibrillation is characterized by disorganized atrial electrical activity and an
irregularly irregular ventricular response when AV conduction is present. It increases the risk of
thromboembolic stroke and may require rate or rhythm management and assessment for
anticoagulation.
Question 9
A patient has a regular narrow-complex tachycardia at approximately 180 beats per minute. P
waves are difficult to identify. Which rhythm is a common possibility?
A. Supraventricular tachycardia B. Sinus bradycardia C. Asystole D. First-degree AV block
Correct answer: A. Supraventricular tachycardia.
Rationale: Some forms of supraventricular tachycardia produce a rapid, regular, narrow-complex
rhythm with P waves hidden within or close to the QRS complexes. The differential diagnosis
includes atrial tachycardia and atrial flutter with fixed conduction. Clinical assessment and a 12-
lead ECG can help distinguish them.
Question 10
Which rhythm is most commonly associated with a sawtooth pattern of atrial activity?
A. Atrial flutter B. Ventricular fibrillation C. Sinus arrhythmia D. Junctional escape rhythm
Correct answer: A. Atrial flutter.
Rationale: Atrial flutter commonly produces organized flutter waves, especially visible in the
inferior ECG leads. The atrial rate is often approximately 250–350 beats per minute, while the
ventricular rate depends on AV conduction.
Question 11
What is a premature ventricular contraction (PVC)?
A. An early electrical impulse arising from the ventricles B. A normal P wave occurring late C.
A complete absence of electrical activity D. A delayed sinus impulse with a normal QRS
