Relias Dysrhythmia Basic Test
Questions And Correct Answers
(Verified Answers) Plus Rationales
2026 Q&A | Instant Download Pdf
1. Which cardiac structure normally serves as the primary pacemaker
of the heart?
A. Atrioventricular node
B. Bundle of His
C. Sinoatrial node
D. Purkinje fibers
Answer: C. Sinoatrial node
Rationale: The sinoatrial (SA) node normally initiates the electrical
impulse that controls the heart's rhythm. It is located in the right
atrium and normally produces a resting rhythm of approximately 60–
100 beats/minute.
2. Which ECG component represents atrial depolarization?
A. P wave
B. QRS complex
C. T wave
D. ST segment
Answer: A. P wave
Rationale: The P wave represents electrical depolarization of the atria.
A normal sinus rhythm generally has one P wave before every QRS
complex, with consistent morphology.
, 3. Which portion of the ECG represents ventricular depolarization?
A. P wave
B. QRS complex
C. T wave
D. U wave
Answer: B. QRS complex
Rationale: The QRS complex represents ventricular depolarization.
Because atrial repolarization occurs at approximately the same time, it
is usually hidden within the QRS complex.
4. What does the T wave normally represent?
A. Atrial depolarization
B. Ventricular depolarization
C. AV nodal conduction
D. Ventricular repolarization
Answer: D. Ventricular repolarization
Rationale: The T wave represents ventricular repolarization, or the
electrical recovery of the ventricles after depolarization. Changes in T-
wave morphology can occur with ischemia, electrolyte disturbances,
and other conditions.
5. Which finding is most characteristic of normal sinus rhythm?
A. Irregular rhythm with no identifiable P waves
B. Wide QRS complexes occurring regularly
C. A P wave preceding each QRS complex with a regular rhythm
D. More QRS complexes than P waves
Answer: C. A P wave preceding each QRS complex with a regular
rhythm
,Rationale: Normal sinus rhythm originates in the SA node and
generally has a regular rhythm, a consistent P-wave morphology, a P
wave before every QRS complex, and a ventricular rate of
approximately 60–100 beats/minute.
6. A patient's heart rate is 48 beats/minute, and the rhythm is regular.
P waves precede every QRS complex, and the PR interval is
consistent. Which rhythm is most likely?
A. Sinus bradycardia
B. Sinus tachycardia
C. Atrial fibrillation
D. Ventricular fibrillation
Answer: A. Sinus bradycardia
Rationale: Sinus bradycardia originates from the SA node but has a
rate below 60 beats/minute in adults. The presence of normal P waves
before each QRS and a regular rhythm supports a sinus origin.
7. A patient has a regular rhythm at 118 beats/minute. Each QRS
complex is preceded by a normal-appearing P wave. Which rhythm
is most likely?
A. Atrial fibrillation
B. Sinus tachycardia
C. Ventricular tachycardia
D. Junctional rhythm
Answer: B. Sinus tachycardia
Rationale: Sinus tachycardia is a sinus rhythm with a rate greater than
100 beats/minute in adults. P waves should maintain a consistent
relationship with the QRS complexes.
8. Which rhythm is classically described as “irregularly irregular”?
, A. Sinus arrhythmia
B. Atrial flutter
C. Junctional rhythm
D. Atrial fibrillation
Answer: D. Atrial fibrillation
Rationale: Atrial fibrillation is characterized by chaotic atrial electrical
activity, absence of consistent organized P waves, and an irregularly
irregular ventricular rhythm. The ventricular response may be rapid,
controlled, or slow.
9. Which ECG finding is most characteristic of atrial fibrillation?
A. No distinct P waves and an irregularly irregular ventricular
rhythm
B. Regular P waves followed by narrow QRS complexes
C. Sawtooth flutter waves with a regular ventricular rate
D. Wide QRS complexes occurring at a very rapid rate
Answer: A. No distinct P waves and an irregularly irregular
ventricular rhythm
Rationale: Atrial fibrillation produces disorganized atrial activity, so
distinct P waves are generally absent. The AV node conducts impulses
unpredictably, producing an irregularly irregular ventricular response.
10. Which ECG appearance is commonly associated with atrial
flutter?
A. Completely absent atrial activity
B. Sawtooth-shaped flutter waves
C. Wide chaotic ventricular complexes
D. One isolated premature ventricular complex
Answer: B. Sawtooth-shaped flutter waves
Questions And Correct Answers
(Verified Answers) Plus Rationales
2026 Q&A | Instant Download Pdf
1. Which cardiac structure normally serves as the primary pacemaker
of the heart?
A. Atrioventricular node
B. Bundle of His
C. Sinoatrial node
D. Purkinje fibers
Answer: C. Sinoatrial node
Rationale: The sinoatrial (SA) node normally initiates the electrical
impulse that controls the heart's rhythm. It is located in the right
atrium and normally produces a resting rhythm of approximately 60–
100 beats/minute.
2. Which ECG component represents atrial depolarization?
A. P wave
B. QRS complex
C. T wave
D. ST segment
Answer: A. P wave
Rationale: The P wave represents electrical depolarization of the atria.
A normal sinus rhythm generally has one P wave before every QRS
complex, with consistent morphology.
, 3. Which portion of the ECG represents ventricular depolarization?
A. P wave
B. QRS complex
C. T wave
D. U wave
Answer: B. QRS complex
Rationale: The QRS complex represents ventricular depolarization.
Because atrial repolarization occurs at approximately the same time, it
is usually hidden within the QRS complex.
4. What does the T wave normally represent?
A. Atrial depolarization
B. Ventricular depolarization
C. AV nodal conduction
D. Ventricular repolarization
Answer: D. Ventricular repolarization
Rationale: The T wave represents ventricular repolarization, or the
electrical recovery of the ventricles after depolarization. Changes in T-
wave morphology can occur with ischemia, electrolyte disturbances,
and other conditions.
5. Which finding is most characteristic of normal sinus rhythm?
A. Irregular rhythm with no identifiable P waves
B. Wide QRS complexes occurring regularly
C. A P wave preceding each QRS complex with a regular rhythm
D. More QRS complexes than P waves
Answer: C. A P wave preceding each QRS complex with a regular
rhythm
,Rationale: Normal sinus rhythm originates in the SA node and
generally has a regular rhythm, a consistent P-wave morphology, a P
wave before every QRS complex, and a ventricular rate of
approximately 60–100 beats/minute.
6. A patient's heart rate is 48 beats/minute, and the rhythm is regular.
P waves precede every QRS complex, and the PR interval is
consistent. Which rhythm is most likely?
A. Sinus bradycardia
B. Sinus tachycardia
C. Atrial fibrillation
D. Ventricular fibrillation
Answer: A. Sinus bradycardia
Rationale: Sinus bradycardia originates from the SA node but has a
rate below 60 beats/minute in adults. The presence of normal P waves
before each QRS and a regular rhythm supports a sinus origin.
7. A patient has a regular rhythm at 118 beats/minute. Each QRS
complex is preceded by a normal-appearing P wave. Which rhythm
is most likely?
A. Atrial fibrillation
B. Sinus tachycardia
C. Ventricular tachycardia
D. Junctional rhythm
Answer: B. Sinus tachycardia
Rationale: Sinus tachycardia is a sinus rhythm with a rate greater than
100 beats/minute in adults. P waves should maintain a consistent
relationship with the QRS complexes.
8. Which rhythm is classically described as “irregularly irregular”?
, A. Sinus arrhythmia
B. Atrial flutter
C. Junctional rhythm
D. Atrial fibrillation
Answer: D. Atrial fibrillation
Rationale: Atrial fibrillation is characterized by chaotic atrial electrical
activity, absence of consistent organized P waves, and an irregularly
irregular ventricular rhythm. The ventricular response may be rapid,
controlled, or slow.
9. Which ECG finding is most characteristic of atrial fibrillation?
A. No distinct P waves and an irregularly irregular ventricular
rhythm
B. Regular P waves followed by narrow QRS complexes
C. Sawtooth flutter waves with a regular ventricular rate
D. Wide QRS complexes occurring at a very rapid rate
Answer: A. No distinct P waves and an irregularly irregular
ventricular rhythm
Rationale: Atrial fibrillation produces disorganized atrial activity, so
distinct P waves are generally absent. The AV node conducts impulses
unpredictably, producing an irregularly irregular ventricular response.
10. Which ECG appearance is commonly associated with atrial
flutter?
A. Completely absent atrial activity
B. Sawtooth-shaped flutter waves
C. Wide chaotic ventricular complexes
D. One isolated premature ventricular complex
Answer: B. Sawtooth-shaped flutter waves
