Basic Arrhythmia Interpretation Exam | ECG Rhythm
Practice Questions, Answers & Detailed Explanations
2026/2027
Question 1
What is the primary electrocardiographic characteristic used to define a
Normal Sinus Rhythm (NSR)?
A. Regular rate of 60 to 100 bpm with upright P waves preceding every
narrow QRS complex and consistent PR intervals
B. Irregular rate exceeding 100 bpm with absent P waves and wide QRS
complexes
C. Slow rate below 60 bpm with prolonged PR intervals exceeding 0.30
seconds
D. Sawtooth baseline flutter waves with variable ventricular responses
Correct Answer: A. Regular rate of 60 to 100 bpm with upright P waves
preceding every narrow QRS complex and consistent PR intervals
Detailed Rationale: NSR originates normally in the sinoatrial (SA) node,
displaying uniform upright P waves in leads II, III, and aVF, normal
conduction intervals, and a regular rhythm between 60 and 100 bpm.
Question 2
How is Sinus Bradycardia differentiated from a normal sinus rhythm on
a rhythm strip?
,A. The rate is slower than 60 beats per minute, while all other sinus
characteristics remain normal.
B. The QRS complexes are wide and bizarre, exceeding 0.12 seconds.
C. P waves are completely absent from the baseline.
D. The R-R intervals are irregularly irregular.
Correct Answer: A. The rate is slower than 60 beats per minute, while
all other sinus characteristics remain normal.
Detailed Rationale: Sinus bradycardia shares identical morphology to
normal sinus rhythm (upright P waves, constant PR intervals, narrow
QRS) except that the ventricular rate drops below 60 beats per minute.
Question 3
What defines Sinus Tachycardia when interpreting an ECG tracing?
A. A regular sinus rhythm with an accelerated heart rate between 100
and 150 beats per minute
B. A chaotic rhythm exceeding 200 beats per minute with no visible P
waves
C. A slow rhythm with dropped beats and prolonged PR intervals
D. An irregular rhythm featuring sawtooth waves
Correct Answer: A. A regular sinus rhythm with an accelerated heart
rate between 100 and 150 beats per minute
Detailed Rationale: Sinus tachycardia is an elevation of heart rate
driven by the SA node responding to physiological stressors,
maintaining normal P-wave morphology and a rate typically between
100 and 150 bpm.
,Question 4
What is the normal standard duration for the PR interval on ECG paper?
A. 0.12 to 0.20 seconds (3 to 5 small boxes)
B. 0.04 to 0.10 seconds (1 to 2 small boxes)
C. 0.20 to 0.40 seconds (5 to 10 small boxes)
D. 0.50 to 0.60 seconds
Correct Answer: A. 0.12 to 0.20 seconds (3 to 5 small boxes)
Detailed Rationale: The PR interval measures electrical transit time
from atrial depolarization through the AV node. Normal duration spans
3 to 5 small horizontal grid squares.
Question 5
What is the normal acceptable duration range for a narrow QRS
complex representing ventricular depolarization?
A. Less than 0.12 seconds (up to 3 small boxes)
B. Exactly 0.20 seconds
C. 0.30 to 0.45 seconds
D. Greater than 0.15 seconds
Correct Answer: A. Less than 0.12 seconds (up to 3 small boxes)
Detailed Rationale: Rapid ventricular activation via the normal His-
Purkinje conduction network produces a narrow QRS complex lasting
less than 0.12 seconds (3 small boxes).
Question 6
, Which key features characterize Atrial Fibrillation (AFib) during rhythm
interpretation?
A. An irregularly irregular ventricular rhythm with absent discrete P
waves and undulating fibrillatory baseline waves
B. A regular rhythm with sawtooth flutter waves at 300 bpm
C. Fixed PR intervals exceeding 0.28 seconds
D. Wide bizarre QRS complexes occurring at 40 bpm
Correct Answer: A. An irregularly irregular ventricular rhythm with
absent discrete P waves and undulating fibrillatory baseline waves
Detailed Rationale: AFib is caused by chaotic micro-reentrant electrical
impulses in the atria, resulting in an erratic, unpredictable ventricular
response (irregularly irregular) and a wavy baseline without true P
waves.
Question 7
What distinct ECG pattern identifies Atrial Flutter?
A. Regular sawtooth or picket-fence flutter waves (F waves) with a
consistent or variable ventricular response
B. Completely flat baseline with zero electrical activity
C. Inverted P waves appearing after wide QRS complexes
D. Randomly changing P wave shapes at 110 bpm
Correct Answer: A. Regular sawtooth or picket-fence flutter waves (F
waves) with a consistent or variable ventricular response
Practice Questions, Answers & Detailed Explanations
2026/2027
Question 1
What is the primary electrocardiographic characteristic used to define a
Normal Sinus Rhythm (NSR)?
A. Regular rate of 60 to 100 bpm with upright P waves preceding every
narrow QRS complex and consistent PR intervals
B. Irregular rate exceeding 100 bpm with absent P waves and wide QRS
complexes
C. Slow rate below 60 bpm with prolonged PR intervals exceeding 0.30
seconds
D. Sawtooth baseline flutter waves with variable ventricular responses
Correct Answer: A. Regular rate of 60 to 100 bpm with upright P waves
preceding every narrow QRS complex and consistent PR intervals
Detailed Rationale: NSR originates normally in the sinoatrial (SA) node,
displaying uniform upright P waves in leads II, III, and aVF, normal
conduction intervals, and a regular rhythm between 60 and 100 bpm.
Question 2
How is Sinus Bradycardia differentiated from a normal sinus rhythm on
a rhythm strip?
,A. The rate is slower than 60 beats per minute, while all other sinus
characteristics remain normal.
B. The QRS complexes are wide and bizarre, exceeding 0.12 seconds.
C. P waves are completely absent from the baseline.
D. The R-R intervals are irregularly irregular.
Correct Answer: A. The rate is slower than 60 beats per minute, while
all other sinus characteristics remain normal.
Detailed Rationale: Sinus bradycardia shares identical morphology to
normal sinus rhythm (upright P waves, constant PR intervals, narrow
QRS) except that the ventricular rate drops below 60 beats per minute.
Question 3
What defines Sinus Tachycardia when interpreting an ECG tracing?
A. A regular sinus rhythm with an accelerated heart rate between 100
and 150 beats per minute
B. A chaotic rhythm exceeding 200 beats per minute with no visible P
waves
C. A slow rhythm with dropped beats and prolonged PR intervals
D. An irregular rhythm featuring sawtooth waves
Correct Answer: A. A regular sinus rhythm with an accelerated heart
rate between 100 and 150 beats per minute
Detailed Rationale: Sinus tachycardia is an elevation of heart rate
driven by the SA node responding to physiological stressors,
maintaining normal P-wave morphology and a rate typically between
100 and 150 bpm.
,Question 4
What is the normal standard duration for the PR interval on ECG paper?
A. 0.12 to 0.20 seconds (3 to 5 small boxes)
B. 0.04 to 0.10 seconds (1 to 2 small boxes)
C. 0.20 to 0.40 seconds (5 to 10 small boxes)
D. 0.50 to 0.60 seconds
Correct Answer: A. 0.12 to 0.20 seconds (3 to 5 small boxes)
Detailed Rationale: The PR interval measures electrical transit time
from atrial depolarization through the AV node. Normal duration spans
3 to 5 small horizontal grid squares.
Question 5
What is the normal acceptable duration range for a narrow QRS
complex representing ventricular depolarization?
A. Less than 0.12 seconds (up to 3 small boxes)
B. Exactly 0.20 seconds
C. 0.30 to 0.45 seconds
D. Greater than 0.15 seconds
Correct Answer: A. Less than 0.12 seconds (up to 3 small boxes)
Detailed Rationale: Rapid ventricular activation via the normal His-
Purkinje conduction network produces a narrow QRS complex lasting
less than 0.12 seconds (3 small boxes).
Question 6
, Which key features characterize Atrial Fibrillation (AFib) during rhythm
interpretation?
A. An irregularly irregular ventricular rhythm with absent discrete P
waves and undulating fibrillatory baseline waves
B. A regular rhythm with sawtooth flutter waves at 300 bpm
C. Fixed PR intervals exceeding 0.28 seconds
D. Wide bizarre QRS complexes occurring at 40 bpm
Correct Answer: A. An irregularly irregular ventricular rhythm with
absent discrete P waves and undulating fibrillatory baseline waves
Detailed Rationale: AFib is caused by chaotic micro-reentrant electrical
impulses in the atria, resulting in an erratic, unpredictable ventricular
response (irregularly irregular) and a wavy baseline without true P
waves.
Question 7
What distinct ECG pattern identifies Atrial Flutter?
A. Regular sawtooth or picket-fence flutter waves (F waves) with a
consistent or variable ventricular response
B. Completely flat baseline with zero electrical activity
C. Inverted P waves appearing after wide QRS complexes
D. Randomly changing P wave shapes at 110 bpm
Correct Answer: A. Regular sawtooth or picket-fence flutter waves (F
waves) with a consistent or variable ventricular response
