Relias Dysrhythmia Basic A Assessment 2026 Updated Questions and
Answers | Complete Cardiac Rhythm Interpretation Study Guide with
Verified Solutions, Detailed Rationales, ECG Fundamentals, Heart
Conduction System, Sinus Rhythms, Atrial Dysrhythmias, Ventricular
Dysrhythmias, AV Blocks, Rhythm Recognition, Cardiac Monitoring,
Patient Assessment and Relias Competency Exam Preparation
Question 1: How many seconds does one small box on standard ECG graph paper
represent? A. 0.10 seconds B. 0.20 seconds C. 0.04 seconds D. 0.02 seconds
CORRECT ANSWER: C. 0.04 seconds Rationale: Standard ECG paper runs at 25
mm/sec; therefore, one small box (1 mm) represents 0.04 seconds.
Question 2: How many seconds does one large box on standard ECG graph paper
represent? A. 0.04 seconds B. 0.10 seconds C. 0.20 seconds D. 1.00 seconds
CORRECT ANSWER: C. 0.20 seconds Rationale: A large box consists of five small
boxes. Multiplying 5 by 0.04 seconds equals 0.20 seconds.
Question 3: What is the standard calibration for the vertical axis of an ECG? A. 1 mV
= 5 mm B. 1 mV = 10 mm C. 1 mV = 15 mm D. 1 mV = 20 mm CORRECT ANSWER: B. 1
mV = 10 mm Rationale: The standard calibration marks the vertical axis so that 1
millivolt equals 10 small boxes (10 mm) in amplitude.
Question 4: What is the normal duration of the PR interval? A. 0.04 to 0.10 seconds
B. 0.12 to 0.20 seconds C. 0.20 to 0.24 seconds D. 0.06 to 0.10 seconds CORRECT
ANSWER: B. 0.12 to 0.20 seconds Rationale: The PR interval represents the time from
the onset of atrial depolarization to the onset of ventricular depolarization and normally
measures 0.12 to 0.20 seconds.
Question 5: What is the normal duration of the QRS complex? A. 0.04 to 0.10
seconds B. 0.12 to 0.20 seconds C. 0.20 to 0.24 seconds D. Less than 0.04 seconds
CORRECT ANSWER: A. 0.04 to 0.10 seconds Rationale: The QRS complex represents
ventricular depolarization. Normal conduction through the bundle branches results in a
narrow complex of 0.04 to 0.10 seconds.
Question 6: What cardiac event does the P wave represent? A. Atrial depolarization
B. Atrial repolarization C. Ventricular depolarization D. Ventricular repolarization
CORRECT ANSWER: A. Atrial depolarization Rationale: The electrical impulse
originating from the sinoatrial node causes atrial depolarization, represented by the P
wave.
Question 7: What cardiac event does the T wave represent? A. Atrial depolarization
B. Atrial repolarization C. Ventricular depolarization D. Ventricular repolarization
CORRECT ANSWER: D. Ventricular repolarization Rationale: The T wave reflects the
recovery phase (repolarization) of the ventricles.
Question 8: Why is atrial repolarization usually not seen on a standard ECG? A. It
occurs during the PR interval. B. It is buried in the QRS complex. C. It is too weak to be
detected. D. It occurs after the T wave. CORRECT ANSWER: B. It is buried in the QRS
,complex. Rationale: Atrial repolarization happens simultaneously with ventricular
depolarization and is obscured by the much larger electrical signal of the QRS complex.
Question 9: What is the primary pacemaker of the healthy heart? A. Atrioventricular
node B. Bundle of His C. Purkinje fibers D. Sinoatrial node CORRECT ANSWER: D.
Sinoatrial node Rationale: The SA node has the fastest intrinsic rate (60-100 bpm) and
serves as the primary pacemaker of the heart.
Question 10: What is the intrinsic rate of the atrioventricular (AV) node? A. 60 to 100
bpm B. 40 to 60 bpm C. 20 to 40 bpm D. 10 to 20 bpm CORRECT ANSWER: B. 40 to 60
bpm Rationale: If the SA node fails, the AV node acts as a secondary pacemaker with
an intrinsic rate of 40 to 60 bpm.
Question 11: What is the intrinsic rate of the ventricular pacemaker cells (Purkinje
fibers)? A. 60 to 100 bpm B. 40 to 60 bpm C. 20 to 40 bpm D. 10 to 20 bpm CORRECT
ANSWER: C. 20 to 40 bpm Rationale: Ventricular pacemaker cells have the slowest
intrinsic rate, firing at 20 to 40 bpm if higher pacemakers fail.
Question 12: In Normal Sinus Rhythm, what is the typical heart rate? A. 40 to 60 bpm
B. 60 to 100 bpm C. 100 to 150 bpm D. Less than 40 bpm CORRECT ANSWER: B. 60 to
100 bpm Rationale: Normal sinus rhythm is defined by a regular rhythm originating in
the SA node with a rate between 60 and 100 beats per minute.
Question 13: Which characteristic is required to identify a rhythm as originating
from the SA node? A. Inverted P waves in lead II B. Absent P waves C. Upright P waves
in lead II D. Wide QRS complexes CORRECT ANSWER: C. Upright P waves in lead II
Rationale: The SA node is located in the high right atrium; the electrical vector moves
toward lead II, producing upright P waves.
Question 14: What defines Sinus Bradycardia? A. Rate below 60 bpm, normal P
waves B. Rate above 100 bpm, normal P waves C. Irregular rhythm with variable P waves
D. Absent P waves with wide QRS CORRECT ANSWER: A. Rate below 60 bpm, normal
P waves Rationale: Sinus bradycardia is a normal sinus rhythm with a rate slower than
60 beats per minute.
Question 15: Which of the following is a common, benign cause of sinus
bradycardia? A. Hypovolemia B. High athletic conditioning C. Sympathetic stimulation
D. Hyperthyroidism CORRECT ANSWER: B. High athletic conditioning Rationale:
Well-conditioned athletes often have resting sinus bradycardia due to high vagal tone.
Question 16: What defines Sinus Tachycardia? A. Rate below 60 bpm B. Rate between
60 and 100 bpm C. Rate greater than 100 bpm D. Irregular rate greater than 100 bpm
CORRECT ANSWER: C. Rate greater than 100 bpm Rationale: Sinus tachycardia is a
normal sinus rhythm with a rate exceeding 100 beats per minute.
Question 17: Which physiological state commonly causes sinus tachycardia? A.
Sleep B. Hypothermia C. Exercise D. Beta-blocker administration CORRECT ANSWER:
, C. Exercise Rationale: Exercise increases sympathetic nervous system activity, leading
to an increased heart rate (sinus tachycardia).
Question 18: What is the defining characteristic of Sinus Arrhythmia? A. Rate varies
with the respiratory cycle B. P waves change morphology C. PR interval prolongs with
each beat D. QRS complexes are wide and bizarre CORRECT ANSWER: A. Rate varies
with the respiratory cycle Rationale: Sinus arrhythmia is a normal variant where the
heart rate increases during inspiration and decreases during expiration.
Question 19: What distinguishes a Sinus Pause from Sinus Arrest? A. Pause is
shorter than one P-P interval; arrest is longer B. Pause has wide QRS; arrest has narrow
QRS C. Pause lacks P waves; arrest has inverted P waves D. There is no difference; they
are synonymous CORRECT ANSWER: A. Pause is shorter than one P-P interval;
arrest is longer Rationale: A sinus pause is a temporary failure of the SA node lasting
less than one exact P-P interval, whereas sinus arrest is a complete failure lasting
longer.
Question 20: What is a Premature Atrial Complex (PAC)? A. An early beat originating
in the ventricles B. An early beat originating in the atria outside the SA node C. A delayed
beat originating in the AV node D. A missed beat due to SA node failure CORRECT
ANSWER: B. An early beat originating in the atria outside the SA node Rationale:
PACs are early ectopic beats originating from an irritable focus in the atria other than
the SA node.
Question 21: How does the P wave of a PAC typically appear compared to a normal
sinus P wave? A. It is always inverted B. It is hidden in the T wave C. It may have a
different morphology or be hidden D. It is always wider and taller CORRECT ANSWER:
C. It may have a different morphology or be hidden Rationale: Because the PAC
originates outside the SA node, the depolarization vector differs, altering the P wave
shape or causing it to merge with the preceding T wave.
Question 22: What is the QRS duration of a typical PAC? A. Greater than 0.12
seconds B. Less than 0.12 seconds C. Variable depending on the heart rate D. Exactly
0.20 seconds CORRECT ANSWER: B. Less than 0.12 seconds Rationale: PACs
conduct down the normal AV and ventricular pathways, resulting in a narrow QRS
complex (< 0.12 seconds).
Question 23: What is Atrial Flutter? A. A chaotic, irregular atrial rhythm B. A rapid,
regular atrial rhythm with a "sawtooth" pattern C. A slow junctional escape rhythm D. A
ventricular rhythm with no atrial activity CORRECT ANSWER: B. A rapid, regular atrial
rhythm with a "sawtooth" pattern Rationale: Atrial flutter is caused by a reentry circuit
in the atria, producing rapid "F" waves that look like sawteeth.
Question 24: What is the typical atrial rate in Atrial Flutter? A. 100 to 150 bpm B. 250
to 350 bpm C. 350 to 600 bpm D. Less than 60 bpm CORRECT ANSWER: B. 250 to 350
bpm Rationale: The atrial rate in typical atrial flutter ranges from 250 to 350 beats per
minute.
Answers | Complete Cardiac Rhythm Interpretation Study Guide with
Verified Solutions, Detailed Rationales, ECG Fundamentals, Heart
Conduction System, Sinus Rhythms, Atrial Dysrhythmias, Ventricular
Dysrhythmias, AV Blocks, Rhythm Recognition, Cardiac Monitoring,
Patient Assessment and Relias Competency Exam Preparation
Question 1: How many seconds does one small box on standard ECG graph paper
represent? A. 0.10 seconds B. 0.20 seconds C. 0.04 seconds D. 0.02 seconds
CORRECT ANSWER: C. 0.04 seconds Rationale: Standard ECG paper runs at 25
mm/sec; therefore, one small box (1 mm) represents 0.04 seconds.
Question 2: How many seconds does one large box on standard ECG graph paper
represent? A. 0.04 seconds B. 0.10 seconds C. 0.20 seconds D. 1.00 seconds
CORRECT ANSWER: C. 0.20 seconds Rationale: A large box consists of five small
boxes. Multiplying 5 by 0.04 seconds equals 0.20 seconds.
Question 3: What is the standard calibration for the vertical axis of an ECG? A. 1 mV
= 5 mm B. 1 mV = 10 mm C. 1 mV = 15 mm D. 1 mV = 20 mm CORRECT ANSWER: B. 1
mV = 10 mm Rationale: The standard calibration marks the vertical axis so that 1
millivolt equals 10 small boxes (10 mm) in amplitude.
Question 4: What is the normal duration of the PR interval? A. 0.04 to 0.10 seconds
B. 0.12 to 0.20 seconds C. 0.20 to 0.24 seconds D. 0.06 to 0.10 seconds CORRECT
ANSWER: B. 0.12 to 0.20 seconds Rationale: The PR interval represents the time from
the onset of atrial depolarization to the onset of ventricular depolarization and normally
measures 0.12 to 0.20 seconds.
Question 5: What is the normal duration of the QRS complex? A. 0.04 to 0.10
seconds B. 0.12 to 0.20 seconds C. 0.20 to 0.24 seconds D. Less than 0.04 seconds
CORRECT ANSWER: A. 0.04 to 0.10 seconds Rationale: The QRS complex represents
ventricular depolarization. Normal conduction through the bundle branches results in a
narrow complex of 0.04 to 0.10 seconds.
Question 6: What cardiac event does the P wave represent? A. Atrial depolarization
B. Atrial repolarization C. Ventricular depolarization D. Ventricular repolarization
CORRECT ANSWER: A. Atrial depolarization Rationale: The electrical impulse
originating from the sinoatrial node causes atrial depolarization, represented by the P
wave.
Question 7: What cardiac event does the T wave represent? A. Atrial depolarization
B. Atrial repolarization C. Ventricular depolarization D. Ventricular repolarization
CORRECT ANSWER: D. Ventricular repolarization Rationale: The T wave reflects the
recovery phase (repolarization) of the ventricles.
Question 8: Why is atrial repolarization usually not seen on a standard ECG? A. It
occurs during the PR interval. B. It is buried in the QRS complex. C. It is too weak to be
detected. D. It occurs after the T wave. CORRECT ANSWER: B. It is buried in the QRS
,complex. Rationale: Atrial repolarization happens simultaneously with ventricular
depolarization and is obscured by the much larger electrical signal of the QRS complex.
Question 9: What is the primary pacemaker of the healthy heart? A. Atrioventricular
node B. Bundle of His C. Purkinje fibers D. Sinoatrial node CORRECT ANSWER: D.
Sinoatrial node Rationale: The SA node has the fastest intrinsic rate (60-100 bpm) and
serves as the primary pacemaker of the heart.
Question 10: What is the intrinsic rate of the atrioventricular (AV) node? A. 60 to 100
bpm B. 40 to 60 bpm C. 20 to 40 bpm D. 10 to 20 bpm CORRECT ANSWER: B. 40 to 60
bpm Rationale: If the SA node fails, the AV node acts as a secondary pacemaker with
an intrinsic rate of 40 to 60 bpm.
Question 11: What is the intrinsic rate of the ventricular pacemaker cells (Purkinje
fibers)? A. 60 to 100 bpm B. 40 to 60 bpm C. 20 to 40 bpm D. 10 to 20 bpm CORRECT
ANSWER: C. 20 to 40 bpm Rationale: Ventricular pacemaker cells have the slowest
intrinsic rate, firing at 20 to 40 bpm if higher pacemakers fail.
Question 12: In Normal Sinus Rhythm, what is the typical heart rate? A. 40 to 60 bpm
B. 60 to 100 bpm C. 100 to 150 bpm D. Less than 40 bpm CORRECT ANSWER: B. 60 to
100 bpm Rationale: Normal sinus rhythm is defined by a regular rhythm originating in
the SA node with a rate between 60 and 100 beats per minute.
Question 13: Which characteristic is required to identify a rhythm as originating
from the SA node? A. Inverted P waves in lead II B. Absent P waves C. Upright P waves
in lead II D. Wide QRS complexes CORRECT ANSWER: C. Upright P waves in lead II
Rationale: The SA node is located in the high right atrium; the electrical vector moves
toward lead II, producing upright P waves.
Question 14: What defines Sinus Bradycardia? A. Rate below 60 bpm, normal P
waves B. Rate above 100 bpm, normal P waves C. Irregular rhythm with variable P waves
D. Absent P waves with wide QRS CORRECT ANSWER: A. Rate below 60 bpm, normal
P waves Rationale: Sinus bradycardia is a normal sinus rhythm with a rate slower than
60 beats per minute.
Question 15: Which of the following is a common, benign cause of sinus
bradycardia? A. Hypovolemia B. High athletic conditioning C. Sympathetic stimulation
D. Hyperthyroidism CORRECT ANSWER: B. High athletic conditioning Rationale:
Well-conditioned athletes often have resting sinus bradycardia due to high vagal tone.
Question 16: What defines Sinus Tachycardia? A. Rate below 60 bpm B. Rate between
60 and 100 bpm C. Rate greater than 100 bpm D. Irregular rate greater than 100 bpm
CORRECT ANSWER: C. Rate greater than 100 bpm Rationale: Sinus tachycardia is a
normal sinus rhythm with a rate exceeding 100 beats per minute.
Question 17: Which physiological state commonly causes sinus tachycardia? A.
Sleep B. Hypothermia C. Exercise D. Beta-blocker administration CORRECT ANSWER:
, C. Exercise Rationale: Exercise increases sympathetic nervous system activity, leading
to an increased heart rate (sinus tachycardia).
Question 18: What is the defining characteristic of Sinus Arrhythmia? A. Rate varies
with the respiratory cycle B. P waves change morphology C. PR interval prolongs with
each beat D. QRS complexes are wide and bizarre CORRECT ANSWER: A. Rate varies
with the respiratory cycle Rationale: Sinus arrhythmia is a normal variant where the
heart rate increases during inspiration and decreases during expiration.
Question 19: What distinguishes a Sinus Pause from Sinus Arrest? A. Pause is
shorter than one P-P interval; arrest is longer B. Pause has wide QRS; arrest has narrow
QRS C. Pause lacks P waves; arrest has inverted P waves D. There is no difference; they
are synonymous CORRECT ANSWER: A. Pause is shorter than one P-P interval;
arrest is longer Rationale: A sinus pause is a temporary failure of the SA node lasting
less than one exact P-P interval, whereas sinus arrest is a complete failure lasting
longer.
Question 20: What is a Premature Atrial Complex (PAC)? A. An early beat originating
in the ventricles B. An early beat originating in the atria outside the SA node C. A delayed
beat originating in the AV node D. A missed beat due to SA node failure CORRECT
ANSWER: B. An early beat originating in the atria outside the SA node Rationale:
PACs are early ectopic beats originating from an irritable focus in the atria other than
the SA node.
Question 21: How does the P wave of a PAC typically appear compared to a normal
sinus P wave? A. It is always inverted B. It is hidden in the T wave C. It may have a
different morphology or be hidden D. It is always wider and taller CORRECT ANSWER:
C. It may have a different morphology or be hidden Rationale: Because the PAC
originates outside the SA node, the depolarization vector differs, altering the P wave
shape or causing it to merge with the preceding T wave.
Question 22: What is the QRS duration of a typical PAC? A. Greater than 0.12
seconds B. Less than 0.12 seconds C. Variable depending on the heart rate D. Exactly
0.20 seconds CORRECT ANSWER: B. Less than 0.12 seconds Rationale: PACs
conduct down the normal AV and ventricular pathways, resulting in a narrow QRS
complex (< 0.12 seconds).
Question 23: What is Atrial Flutter? A. A chaotic, irregular atrial rhythm B. A rapid,
regular atrial rhythm with a "sawtooth" pattern C. A slow junctional escape rhythm D. A
ventricular rhythm with no atrial activity CORRECT ANSWER: B. A rapid, regular atrial
rhythm with a "sawtooth" pattern Rationale: Atrial flutter is caused by a reentry circuit
in the atria, producing rapid "F" waves that look like sawteeth.
Question 24: What is the typical atrial rate in Atrial Flutter? A. 100 to 150 bpm B. 250
to 350 bpm C. 350 to 600 bpm D. Less than 60 bpm CORRECT ANSWER: B. 250 to 350
bpm Rationale: The atrial rate in typical atrial flutter ranges from 250 to 350 beats per
minute.
