RELIAS Dysrhythmia Exam Prep | Practice Questions with Verified
Answers and Detailed Rationales | Cardiac Rhythm Interpretation,
ECG Waveform Analysis, Arrhythmia Identification, Heart Block
Recognition, Telemetry Monitoring, Cardiac Emergency Response
and Clinical Cardiology Basics
Question 1: Which ECG component represents ventricular depolarization?
A. P wave
B. QRS complex
C. T wave
D. U wave
CORRECT ANSWER: B. QRS complex
RATIONALE : The QRS complex on an electrocardiogram represents the electrical
depolarization of the ventricles, which triggers ventricular contraction. The P wave
represents atrial depolarization, the T wave represents ventricular repolarization, and
the U wave, when present, may represent repolarization of the Purkinje fibers or
papillary muscles.
Question 2: A regular rhythm with a rate of 48 beats per minute, normal P waves
preceding each QRS complex, and a PR interval of 0.16 seconds is best identified
as:
A. Sinus bradycardia
B. Junctional rhythm
C. First-degree heart block
D. Sinus arrhythmia
CORRECT ANSWER: A. Sinus bradycardia
RATIONALE : Sinus bradycardia is characterized by a regular rhythm originating from the
SA node with a rate less than 60 beats per minute, normal P waves preceding each QRS
complex, and a normal PR interval (0.12-0.20 seconds). The described rhythm meets all
these criteria. Junctional rhythm typically has absent or inverted P waves, first-degree
heart block has a prolonged PR interval >0.20 seconds, and sinus arrhythmia has an
irregular rhythm that varies with respiration.
Question 3: What is the normal duration of the PR interval on a standard ECG?
A. 0.04-0.08 seconds
B. 0.12-0.20 seconds
C. 0.20-0.36 seconds
D. 0.36-0.44 seconds
CORRECT ANSWER: B. 0.12-0.20 seconds
RATIONALE : The PR interval, measured from the beginning of the P wave to the
beginning of the QRS complex, normally ranges from 0.12 to 0.20 seconds (3-5 small
,boxes on standard ECG paper). This interval represents the time required for the
electrical impulse to travel from the SA node through the atria, AV node, and bundle of
His to the Purkinje fibers.
Question 4: Which dysrhythmia is characterized by an irregularly irregular rhythm
with no discernible P waves?
A. Atrial flutter
B. Sinus arrhythmia
C. Atrial fibrillation
D. Multifocal atrial tachycardia
CORRECT ANSWER: C. Atrial fibrillation
RATIONALE : Atrial fibrillation is characterized by chaotic, disorganized atrial electrical
activity resulting in an irregularly irregular ventricular response and absence of distinct
P waves on the ECG. Instead, fibrillatory waves or a wavy baseline may be seen. Atrial
flutter shows sawtooth flutter waves, sinus arrhythmia has normal P waves with
respiratory variation, and multifocal atrial tachycardia has at least three different P wave
morphologies.
Question 5: A patient presents with a heart rate of 180 beats per minute, narrow
QRS complexes, and no visible P waves. This rhythm is most consistent with:
A. Ventricular tachycardia
B. Sinus tachycardia
C. Atrial fibrillation with rapid ventricular response
D. Paroxysmal supraventricular tachycardia
CORRECT ANSWER: D. Paroxysmal supraventricular tachycardia
RATIONALE : Paroxysmal supraventricular tachycardia (PSVT) typically presents with a
regular, narrow-complex tachycardia at rates of 150-250 bpm, often with buried or
absent P waves due to the rapid rate. Ventricular tachycardia has wide QRS complexes,
sinus tachycardia has visible P waves preceding each QRS, and atrial fibrillation has an
irregularly irregular rhythm.
Question 6: Which finding is diagnostic of first-degree atrioventricular block?
A. Dropped QRS complexes after P waves
B. Progressive prolongation of the PR interval until a QRS is dropped
C. PR interval consistently greater than 0.20 seconds
D. Complete dissociation between P waves and QRS complexes
CORRECT ANSWER: C. PR interval consistently greater than 0.20 seconds
RATIONALE : First-degree AV block is defined by a prolonged PR interval exceeding 0.20
seconds with every P wave conducted to the ventricles. Dropped QRS complexes
indicate second-degree block, progressive PR prolongation describes Mobitz Type I
(Wenckebach), and complete AV dissociation characterizes third-degree heart block.
,Question 7: In Mobitz Type I (Wenckebach) second-degree heart block, what
pattern is observed?
A. Constant PR interval with intermittent non-conducted P waves
B. Progressive lengthening of the PR interval until a QRS complex is dropped
C. Random non-conducted P waves without PR interval changes
D. Fixed 2:1 or 3:1 conduction ratio
CORRECT ANSWER: B. Progressive lengthening of the PR interval until a QRS
complex is dropped
RATIONALE : Mobitz Type I (Wenckebach) second-degree AV block is characterized by
progressive prolongation of the PR interval with each successive beat until a P wave
fails to conduct and a QRS complex is dropped, after which the cycle repeats. Constant
PR intervals with dropped beats indicate Mobitz Type II, and fixed conduction ratios may
occur in either type but are not diagnostic alone.
Question 8: Which dysrhythmia requires immediate defibrillation?
A. Asystole
B. Pulseless electrical activity
C. Ventricular fibrillation
D. Sinus bradycardia with hypotension
CORRECT ANSWER: C. Ventricular fibrillation
RATIONALE : Ventricular fibrillation is a shockable rhythm requiring immediate
defibrillation as part of advanced cardiac life support. Asystole and pulseless electrical
activity are non-shockable rhythms treated with CPR and epinephrine. Sinus
bradycardia with hypotension may require atropine or pacing but not defibrillation.
Question 9: What is the hallmark ECG finding in atrial flutter?
A. Irregularly irregular rhythm with fibrillatory waves
B. Sawtooth-shaped flutter waves, typically at 250-350 bpm
C. Wide QRS complexes with AV dissociation
D. Prolonged QT interval with torsades de pointes
CORRECT ANSWER: B. Sawtooth-shaped flutter waves, typically at 250-350 bpm
RATIONALE : Atrial flutter is characterized by regular, sawtooth-shaped flutter waves (F
waves) at an atrial rate of 250-350 bpm, most prominent in leads II, III, aVF, and V1. The
ventricular response depends on the AV conduction ratio (e.g., 2:1, 3:1). Irregularly
irregular rhythm describes atrial fibrillation, wide QRS with AV dissociation indicates
ventricular tachycardia, and prolonged QT with polymorphic VT describes torsades de
pointes.
Question 10: A patient has a rhythm with a rate of 30 bpm, regular P waves at 70
bpm, and no relationship between P waves and QRS complexes. This is:
, A. Sinus bradycardia
B. Second-degree AV block Type II
C. Third-degree (complete) heart block
D. Junctional escape rhythm
CORRECT ANSWER: C. Third-degree (complete) heart block
RATIONALE : Third-degree (complete) heart block is characterized by complete AV
dissociation, where atrial and ventricular activities are independent. P waves occur at a
regular atrial rate, QRS complexes occur at a slower regular ventricular escape rate, and
there is no consistent PR interval relationship. Sinus bradycardia has conducted P
waves, Mobitz Type II has intermittent non-conducted P waves with constant PR
intervals when conducted, and junctional escape rhythm may have retrograde P waves
or no P waves.
Question 11: Which medication is first-line for stable narrow-complex
supraventricular tachycardia?
A. Amiodarone
B. Adenosine
C. Lidocaine
D. Epinephrine
CORRECT ANSWER: B. Adenosine
RATIONALE : Adenosine is the first-line medication for stable narrow-complex
supraventricular tachycardia because it transiently blocks AV nodal conduction, often
terminating reentrant SVT involving the AV node. Amiodarone is used for wider-complex
or unstable tachycardias, lidocaine is primarily for ventricular arrhythmias, and
epinephrine is used in cardiac arrest algorithms.
Question 12: What is the primary nursing intervention for a patient with
symptomatic sinus bradycardia?
A. Administer adenosine immediately
B. Prepare for synchronized cardioversion
C. Assess for underlying causes and prepare for atropine
D. Initiate defibrillation
CORRECT ANSWER: C. Assess for underlying causes and prepare for atropine
RATIONALE : For symptomatic sinus bradycardia, the nurse should first assess for
reversible causes (hypoxia, medications, ischemia) and prepare to administer atropine
per protocol if the patient is unstable. Adenosine is contraindicated in bradycardia,
cardioversion is for unstable tachyarrhythmias, and defibrillation is for VF/pulseless VT.
Question 13: Which ECG finding is most characteristic of premature ventricular
contractions (PVCs)?
Answers and Detailed Rationales | Cardiac Rhythm Interpretation,
ECG Waveform Analysis, Arrhythmia Identification, Heart Block
Recognition, Telemetry Monitoring, Cardiac Emergency Response
and Clinical Cardiology Basics
Question 1: Which ECG component represents ventricular depolarization?
A. P wave
B. QRS complex
C. T wave
D. U wave
CORRECT ANSWER: B. QRS complex
RATIONALE : The QRS complex on an electrocardiogram represents the electrical
depolarization of the ventricles, which triggers ventricular contraction. The P wave
represents atrial depolarization, the T wave represents ventricular repolarization, and
the U wave, when present, may represent repolarization of the Purkinje fibers or
papillary muscles.
Question 2: A regular rhythm with a rate of 48 beats per minute, normal P waves
preceding each QRS complex, and a PR interval of 0.16 seconds is best identified
as:
A. Sinus bradycardia
B. Junctional rhythm
C. First-degree heart block
D. Sinus arrhythmia
CORRECT ANSWER: A. Sinus bradycardia
RATIONALE : Sinus bradycardia is characterized by a regular rhythm originating from the
SA node with a rate less than 60 beats per minute, normal P waves preceding each QRS
complex, and a normal PR interval (0.12-0.20 seconds). The described rhythm meets all
these criteria. Junctional rhythm typically has absent or inverted P waves, first-degree
heart block has a prolonged PR interval >0.20 seconds, and sinus arrhythmia has an
irregular rhythm that varies with respiration.
Question 3: What is the normal duration of the PR interval on a standard ECG?
A. 0.04-0.08 seconds
B. 0.12-0.20 seconds
C. 0.20-0.36 seconds
D. 0.36-0.44 seconds
CORRECT ANSWER: B. 0.12-0.20 seconds
RATIONALE : The PR interval, measured from the beginning of the P wave to the
beginning of the QRS complex, normally ranges from 0.12 to 0.20 seconds (3-5 small
,boxes on standard ECG paper). This interval represents the time required for the
electrical impulse to travel from the SA node through the atria, AV node, and bundle of
His to the Purkinje fibers.
Question 4: Which dysrhythmia is characterized by an irregularly irregular rhythm
with no discernible P waves?
A. Atrial flutter
B. Sinus arrhythmia
C. Atrial fibrillation
D. Multifocal atrial tachycardia
CORRECT ANSWER: C. Atrial fibrillation
RATIONALE : Atrial fibrillation is characterized by chaotic, disorganized atrial electrical
activity resulting in an irregularly irregular ventricular response and absence of distinct
P waves on the ECG. Instead, fibrillatory waves or a wavy baseline may be seen. Atrial
flutter shows sawtooth flutter waves, sinus arrhythmia has normal P waves with
respiratory variation, and multifocal atrial tachycardia has at least three different P wave
morphologies.
Question 5: A patient presents with a heart rate of 180 beats per minute, narrow
QRS complexes, and no visible P waves. This rhythm is most consistent with:
A. Ventricular tachycardia
B. Sinus tachycardia
C. Atrial fibrillation with rapid ventricular response
D. Paroxysmal supraventricular tachycardia
CORRECT ANSWER: D. Paroxysmal supraventricular tachycardia
RATIONALE : Paroxysmal supraventricular tachycardia (PSVT) typically presents with a
regular, narrow-complex tachycardia at rates of 150-250 bpm, often with buried or
absent P waves due to the rapid rate. Ventricular tachycardia has wide QRS complexes,
sinus tachycardia has visible P waves preceding each QRS, and atrial fibrillation has an
irregularly irregular rhythm.
Question 6: Which finding is diagnostic of first-degree atrioventricular block?
A. Dropped QRS complexes after P waves
B. Progressive prolongation of the PR interval until a QRS is dropped
C. PR interval consistently greater than 0.20 seconds
D. Complete dissociation between P waves and QRS complexes
CORRECT ANSWER: C. PR interval consistently greater than 0.20 seconds
RATIONALE : First-degree AV block is defined by a prolonged PR interval exceeding 0.20
seconds with every P wave conducted to the ventricles. Dropped QRS complexes
indicate second-degree block, progressive PR prolongation describes Mobitz Type I
(Wenckebach), and complete AV dissociation characterizes third-degree heart block.
,Question 7: In Mobitz Type I (Wenckebach) second-degree heart block, what
pattern is observed?
A. Constant PR interval with intermittent non-conducted P waves
B. Progressive lengthening of the PR interval until a QRS complex is dropped
C. Random non-conducted P waves without PR interval changes
D. Fixed 2:1 or 3:1 conduction ratio
CORRECT ANSWER: B. Progressive lengthening of the PR interval until a QRS
complex is dropped
RATIONALE : Mobitz Type I (Wenckebach) second-degree AV block is characterized by
progressive prolongation of the PR interval with each successive beat until a P wave
fails to conduct and a QRS complex is dropped, after which the cycle repeats. Constant
PR intervals with dropped beats indicate Mobitz Type II, and fixed conduction ratios may
occur in either type but are not diagnostic alone.
Question 8: Which dysrhythmia requires immediate defibrillation?
A. Asystole
B. Pulseless electrical activity
C. Ventricular fibrillation
D. Sinus bradycardia with hypotension
CORRECT ANSWER: C. Ventricular fibrillation
RATIONALE : Ventricular fibrillation is a shockable rhythm requiring immediate
defibrillation as part of advanced cardiac life support. Asystole and pulseless electrical
activity are non-shockable rhythms treated with CPR and epinephrine. Sinus
bradycardia with hypotension may require atropine or pacing but not defibrillation.
Question 9: What is the hallmark ECG finding in atrial flutter?
A. Irregularly irregular rhythm with fibrillatory waves
B. Sawtooth-shaped flutter waves, typically at 250-350 bpm
C. Wide QRS complexes with AV dissociation
D. Prolonged QT interval with torsades de pointes
CORRECT ANSWER: B. Sawtooth-shaped flutter waves, typically at 250-350 bpm
RATIONALE : Atrial flutter is characterized by regular, sawtooth-shaped flutter waves (F
waves) at an atrial rate of 250-350 bpm, most prominent in leads II, III, aVF, and V1. The
ventricular response depends on the AV conduction ratio (e.g., 2:1, 3:1). Irregularly
irregular rhythm describes atrial fibrillation, wide QRS with AV dissociation indicates
ventricular tachycardia, and prolonged QT with polymorphic VT describes torsades de
pointes.
Question 10: A patient has a rhythm with a rate of 30 bpm, regular P waves at 70
bpm, and no relationship between P waves and QRS complexes. This is:
, A. Sinus bradycardia
B. Second-degree AV block Type II
C. Third-degree (complete) heart block
D. Junctional escape rhythm
CORRECT ANSWER: C. Third-degree (complete) heart block
RATIONALE : Third-degree (complete) heart block is characterized by complete AV
dissociation, where atrial and ventricular activities are independent. P waves occur at a
regular atrial rate, QRS complexes occur at a slower regular ventricular escape rate, and
there is no consistent PR interval relationship. Sinus bradycardia has conducted P
waves, Mobitz Type II has intermittent non-conducted P waves with constant PR
intervals when conducted, and junctional escape rhythm may have retrograde P waves
or no P waves.
Question 11: Which medication is first-line for stable narrow-complex
supraventricular tachycardia?
A. Amiodarone
B. Adenosine
C. Lidocaine
D. Epinephrine
CORRECT ANSWER: B. Adenosine
RATIONALE : Adenosine is the first-line medication for stable narrow-complex
supraventricular tachycardia because it transiently blocks AV nodal conduction, often
terminating reentrant SVT involving the AV node. Amiodarone is used for wider-complex
or unstable tachycardias, lidocaine is primarily for ventricular arrhythmias, and
epinephrine is used in cardiac arrest algorithms.
Question 12: What is the primary nursing intervention for a patient with
symptomatic sinus bradycardia?
A. Administer adenosine immediately
B. Prepare for synchronized cardioversion
C. Assess for underlying causes and prepare for atropine
D. Initiate defibrillation
CORRECT ANSWER: C. Assess for underlying causes and prepare for atropine
RATIONALE : For symptomatic sinus bradycardia, the nurse should first assess for
reversible causes (hypoxia, medications, ischemia) and prepare to administer atropine
per protocol if the patient is unstable. Adenosine is contraindicated in bradycardia,
cardioversion is for unstable tachyarrhythmias, and defibrillation is for VF/pulseless VT.
Question 13: Which ECG finding is most characteristic of premature ventricular
contractions (PVCs)?
