American Red Cross ACLS ECG and
Rhythm Recognition Examination
Questions And Correct Answers
(Verified Answers) Plus Rationales
2026 Q&A | Instant Download Pdf
1. A monitor displays a regular rhythm at 80 beats/min. Each QRS
complex is narrow and is preceded by a consistent upright P wave
with a constant PR interval. Which rhythm is most likely present?
A. Atrial fibrillation
B. Ventricular tachycardia
C. Normal sinus rhythm
D. Complete heart block
Answer: C. Normal sinus rhythm
Rationale: Normal sinus rhythm is characterized by a regular atrial
and ventricular rhythm, a rate generally between 60 and 100
beats/min, an identifiable P wave before every QRS complex, a
consistent PR interval, and narrow QRS complexes.
2. Which ECG finding is most characteristic of atrial fibrillation?
A. Regular rhythm with sawtooth flutter waves
B. Irregularly irregular rhythm with no consistent P waves
C. Wide QRS complexes occurring at exactly 150 beats/min
D. P waves occurring independently of QRS complexes
Answer: B. Irregularly irregular rhythm with no consistent P waves
,Rationale: Atrial fibrillation produces chaotic atrial electrical activity.
The ventricular response is typically irregularly irregular, and discrete,
consistent P waves are absent.
3. A patient has a regular narrow-complex tachycardia at 180
beats/min. P waves are difficult to identify. Which rhythm should
be considered?
A. Supraventricular tachycardia
B. Sinus bradycardia
C. Ventricular fibrillation
D. Complete heart block
Answer: A. Supraventricular tachycardia
Rationale: SVT commonly presents as a rapid, regular narrow-
complex rhythm, often around 150 to 250 beats/min. P waves may be
hidden within the QRS complexes or T waves.
4. Which feature distinguishes ventricular tachycardia from most
supraventricular tachycardias?
A. Presence of a P wave before every QRS
B. Rate below 100 beats/min
C. Irregularly irregular rhythm
D. Wide QRS complexes during the tachycardia
Answer: D. Wide QRS complexes during the tachycardia
Rationale: Ventricular tachycardia usually produces QRS complexes
lasting at least 0.12 second. A wide-complex tachycardia should be
treated as ventricular tachycardia when the diagnosis is uncertain,
particularly in an unstable patient.
5. Which rhythm is defined by chaotic electrical activity with no
organized ventricular depolarization?
,A. Atrial flutter
B. Ventricular fibrillation
C. Sinus rhythm
D. First-degree AV block
Answer: B. Ventricular fibrillation
Rationale: Ventricular fibrillation consists of disorganized ventricular
electrical activity without effective ventricular contraction. It is a
cardiac arrest rhythm requiring immediate recognition and
appropriate resuscitation.
6. A patient’s ECG shows a regular rhythm at 48 beats/min with a
normal P wave before every QRS and a constant PR interval. What
is the rhythm?
A. Junctional tachycardia
B. Atrial fibrillation
C. Sinus bradycardia
D. Ventricular fibrillation
Answer: C. Sinus bradycardia
Rationale: Sinus bradycardia retains the normal sinus pattern but has
a rate below 60 beats/min in adults. Clinical significance depends on
the patient’s symptoms and overall condition.
7. Which ECG characteristic is associated with atrial flutter?
A. Repeated atrial activity producing a sawtooth pattern
B. Completely absent electrical activity
C. Wide, irregular ventricular complexes without atrial activity
D. Progressive PR prolongation followed by dropped QRS complexes
Answer: A. Repeated atrial activity producing a sawtooth pattern
, Rationale: Atrial flutter is associated with rapid, organized atrial
activity, commonly producing characteristic flutter waves. AV
conduction may occur in ratios such as 2:1, 3:1, or 4:1.
8. What does the PR interval primarily represent?
A. Ventricular repolarization
B. Ventricular depolarization
C. Atrial repolarization
D. Conduction from the atria through the AV node and toward the
ventricles
Answer: D. Conduction from the atria through the AV node and
toward the ventricles
Rationale: The PR interval reflects the time from the beginning of
atrial depolarization to the beginning of ventricular depolarization. It
includes conduction through the AV node and His-Purkinje system.
9. A patient has a PR interval of 0.24 second on repeated ECG
complexes, with every P wave followed by a QRS complex. Which
conduction abnormality is present?
A. Second-degree AV block type II
B. First-degree AV block
C. Third-degree AV block
D. Ventricular fibrillation
Answer: B. First-degree AV block
Rationale: First-degree AV block is characterized by a PR interval
longer than 0.20 second with every atrial impulse still conducted to the
ventricles.
10. Which finding is typical of second-degree AV block Mobitz
I?
Rhythm Recognition Examination
Questions And Correct Answers
(Verified Answers) Plus Rationales
2026 Q&A | Instant Download Pdf
1. A monitor displays a regular rhythm at 80 beats/min. Each QRS
complex is narrow and is preceded by a consistent upright P wave
with a constant PR interval. Which rhythm is most likely present?
A. Atrial fibrillation
B. Ventricular tachycardia
C. Normal sinus rhythm
D. Complete heart block
Answer: C. Normal sinus rhythm
Rationale: Normal sinus rhythm is characterized by a regular atrial
and ventricular rhythm, a rate generally between 60 and 100
beats/min, an identifiable P wave before every QRS complex, a
consistent PR interval, and narrow QRS complexes.
2. Which ECG finding is most characteristic of atrial fibrillation?
A. Regular rhythm with sawtooth flutter waves
B. Irregularly irregular rhythm with no consistent P waves
C. Wide QRS complexes occurring at exactly 150 beats/min
D. P waves occurring independently of QRS complexes
Answer: B. Irregularly irregular rhythm with no consistent P waves
,Rationale: Atrial fibrillation produces chaotic atrial electrical activity.
The ventricular response is typically irregularly irregular, and discrete,
consistent P waves are absent.
3. A patient has a regular narrow-complex tachycardia at 180
beats/min. P waves are difficult to identify. Which rhythm should
be considered?
A. Supraventricular tachycardia
B. Sinus bradycardia
C. Ventricular fibrillation
D. Complete heart block
Answer: A. Supraventricular tachycardia
Rationale: SVT commonly presents as a rapid, regular narrow-
complex rhythm, often around 150 to 250 beats/min. P waves may be
hidden within the QRS complexes or T waves.
4. Which feature distinguishes ventricular tachycardia from most
supraventricular tachycardias?
A. Presence of a P wave before every QRS
B. Rate below 100 beats/min
C. Irregularly irregular rhythm
D. Wide QRS complexes during the tachycardia
Answer: D. Wide QRS complexes during the tachycardia
Rationale: Ventricular tachycardia usually produces QRS complexes
lasting at least 0.12 second. A wide-complex tachycardia should be
treated as ventricular tachycardia when the diagnosis is uncertain,
particularly in an unstable patient.
5. Which rhythm is defined by chaotic electrical activity with no
organized ventricular depolarization?
,A. Atrial flutter
B. Ventricular fibrillation
C. Sinus rhythm
D. First-degree AV block
Answer: B. Ventricular fibrillation
Rationale: Ventricular fibrillation consists of disorganized ventricular
electrical activity without effective ventricular contraction. It is a
cardiac arrest rhythm requiring immediate recognition and
appropriate resuscitation.
6. A patient’s ECG shows a regular rhythm at 48 beats/min with a
normal P wave before every QRS and a constant PR interval. What
is the rhythm?
A. Junctional tachycardia
B. Atrial fibrillation
C. Sinus bradycardia
D. Ventricular fibrillation
Answer: C. Sinus bradycardia
Rationale: Sinus bradycardia retains the normal sinus pattern but has
a rate below 60 beats/min in adults. Clinical significance depends on
the patient’s symptoms and overall condition.
7. Which ECG characteristic is associated with atrial flutter?
A. Repeated atrial activity producing a sawtooth pattern
B. Completely absent electrical activity
C. Wide, irregular ventricular complexes without atrial activity
D. Progressive PR prolongation followed by dropped QRS complexes
Answer: A. Repeated atrial activity producing a sawtooth pattern
, Rationale: Atrial flutter is associated with rapid, organized atrial
activity, commonly producing characteristic flutter waves. AV
conduction may occur in ratios such as 2:1, 3:1, or 4:1.
8. What does the PR interval primarily represent?
A. Ventricular repolarization
B. Ventricular depolarization
C. Atrial repolarization
D. Conduction from the atria through the AV node and toward the
ventricles
Answer: D. Conduction from the atria through the AV node and
toward the ventricles
Rationale: The PR interval reflects the time from the beginning of
atrial depolarization to the beginning of ventricular depolarization. It
includes conduction through the AV node and His-Purkinje system.
9. A patient has a PR interval of 0.24 second on repeated ECG
complexes, with every P wave followed by a QRS complex. Which
conduction abnormality is present?
A. Second-degree AV block type II
B. First-degree AV block
C. Third-degree AV block
D. Ventricular fibrillation
Answer: B. First-degree AV block
Rationale: First-degree AV block is characterized by a PR interval
longer than 0.20 second with every atrial impulse still conducted to the
ventricles.
10. Which finding is typical of second-degree AV block Mobitz
I?
