BASIC ARRHYTHMIA SENTARA TEST COMPLETE
STUDY GUIDE 2026 - 300 Practice Questions with
Correct Answers & Detailed Rationales | GRADED A+ |
2026/2027 Update | 100% Verified Solutions
Section 1: Sinus Rhythms (Questions 1–35)
1. A patient's ECG shows a regular rhythm at a rate of 72 bpm.
There are upright, uniform P waves preceding each QRS complex.
The PR interval is 0.16 seconds and the QRS duration is 0.08
seconds. What is the correct interpretation?
A. Normal sinus rhythm
B. Sinus bradycardia
C. Sinus tachycardia
D. Sinus arrhythmia
Answer: A
Rationale: Normal sinus rhythm is characterized by a regular rhythm with a rate of 60–
100 bpm, upright, uniform P waves before each QRS, a PR interval of 0.12–0.20 seconds,
and a QRS duration of <0.12 seconds. All criteria are met in this scenario. Sinus
bradycardia would have a rate <60 bpm, sinus tachycardia would have a rate >100 bpm,
and sinus arrhythmia would show irregularity related to the respiratory cycle .
2. An ECG strip shows a regular rhythm at 48 bpm with upright,
uniform P waves before each QRS. The PR interval is 0.18 seconds
and the QRS duration is 0.08 seconds. What is the rhythm?
,A. Normal sinus rhythm
B. Sinus bradycardia
C. Sinus tachycardia
D. Sinus arrhythmia
Answer: B
Rationale: Sinus bradycardia is identified by a regular sinus rhythm with a rate below 60
bpm. The presence of upright, uniform P waves before each QRS confirms the impulse
originated in the SA node. The patient is asymptomatic. Normal sinus rhythm requires a
rate of 60–100 bpm. Sinus arrhythmia would show irregularity, and sinus tachycardia
would have a rate >100 bpm .
3. A patient presents with a heart rate of 145 bpm, regular
rhythm, and upright P waves preceding each QRS complex. The
PR interval is 0.14 seconds. What is the rhythm?
A. Sinus tachycardia
B. Supraventricular tachycardia
C. Atrial flutter
D. Ventricular tachycardia
Answer: A
Rationale: Sinus tachycardia is identified by a regular rhythm, normal P-wave
morphology, and rates typically between 100–150 bpm. Upright, uniform P waves
preceding each QRS confirm sinus origin. While supraventricular tachycardia can also
present with tachycardia, the presence of distinct upright P waves makes sinus
tachycardia the correct interpretation. Atrial flutter would show saw-tooth flutter waves,
and ventricular tachycardia would show wide QRS complexes .
4. An ECG strip shows an irregularly irregular rhythm with a rate
of 78 bpm. The rhythm varies with the respiratory cycle, and all P
waves are upright and uniform. What is the most likely rhythm?
A. Atrial fibrillation
B. Sinus arrhythmia
,C. Sinus bradycardia
D. Wandering atrial pacemaker
Answer: B
Rationale: Sinus arrhythmia is characterized by an irregularly irregular rhythm where the
heart rate varies with the respiratory cycle (increases with inspiration, decreases with
expiration). All P waves originate from the sinus node and are upright and uniform.
Atrial fibrillation shows no P waves and a grossly irregular rhythm. Wandering atrial
pacemaker would show varying P-wave morphology .
5. The normal PR interval should measure between:
A. 0.04–0.08 seconds
B. 0.08–0.12 seconds
C. 0.12–0.20 seconds
D. 0.20–0.30 seconds
Answer: C
Rationale: The PR interval represents conduction from the atria through the AV node
and His-Purkinje system before ventricular depolarization. The normal PR interval is
0.12–0.20 seconds (3–5 small boxes). A prolonged PR interval suggests first-degree AV
block. A shortened PR interval may indicate pre-excitation (WPW syndrome) or
junctional rhythm .
6. What is the normal duration of the QRS complex?
A. <0.06 seconds
B. <0.12 seconds
C. 0.12–0.20 seconds
D. 0.20–0.40 seconds
Answer: B
Rationale: The QRS complex represents ventricular depolarization. The normal QRS
duration is <0.12 seconds (less than 3 small boxes). A QRS duration >0.12 seconds
indicates a bundle branch block or ventricular origin of the rhythm .
, 7. Which of the following is NOT a criterion for normal sinus
rhythm?
A. Rate between 60–100 bpm
B. PR interval 0.12–0.20 seconds
C. P waves upright in lead II
D. QRS duration >0.12 seconds
Answer: D
Rationale: Normal sinus rhythm requires a rate of 60–100 bpm, a PR interval of 0.12–
0.20 seconds, upright P waves in lead II, and a QRS duration of <0.12 seconds. A QRS
duration >0.12 seconds is not a criterion for normal sinus rhythm and indicates a
conduction abnormality .
8. A patient on a cardiac monitor shows a regular rhythm at 75
bpm with upright P waves. Suddenly, a pause occurs on the
monitor with no P wave or QRS complex for 2 seconds. After the
pause, the rhythm resumes at 75 bpm. This is most consistent
with:
A. Second-degree AV block type II
B. Sinus arrest
C. Sinus block
D. Premature atrial contraction
Answer: B
Rationale: Sinus arrest is characterized by a sudden pause in the sinus rhythm with no P
wave, QRS, or T wave. The pause length is not a multiple of the baseline R-R interval.
The underlying rhythm resumes after the pause. Sinus block would show a pause that is
a multiple of the baseline R-R interval. Premature atrial contractions are early beats, not
pauses .
9. How do you calculate the length of a pause during sinus arrest?
A. Count the R waves in the pause and multiply by 0.02 seconds
B. Count the number of large boxes between the R waves that come right before and
STUDY GUIDE 2026 - 300 Practice Questions with
Correct Answers & Detailed Rationales | GRADED A+ |
2026/2027 Update | 100% Verified Solutions
Section 1: Sinus Rhythms (Questions 1–35)
1. A patient's ECG shows a regular rhythm at a rate of 72 bpm.
There are upright, uniform P waves preceding each QRS complex.
The PR interval is 0.16 seconds and the QRS duration is 0.08
seconds. What is the correct interpretation?
A. Normal sinus rhythm
B. Sinus bradycardia
C. Sinus tachycardia
D. Sinus arrhythmia
Answer: A
Rationale: Normal sinus rhythm is characterized by a regular rhythm with a rate of 60–
100 bpm, upright, uniform P waves before each QRS, a PR interval of 0.12–0.20 seconds,
and a QRS duration of <0.12 seconds. All criteria are met in this scenario. Sinus
bradycardia would have a rate <60 bpm, sinus tachycardia would have a rate >100 bpm,
and sinus arrhythmia would show irregularity related to the respiratory cycle .
2. An ECG strip shows a regular rhythm at 48 bpm with upright,
uniform P waves before each QRS. The PR interval is 0.18 seconds
and the QRS duration is 0.08 seconds. What is the rhythm?
,A. Normal sinus rhythm
B. Sinus bradycardia
C. Sinus tachycardia
D. Sinus arrhythmia
Answer: B
Rationale: Sinus bradycardia is identified by a regular sinus rhythm with a rate below 60
bpm. The presence of upright, uniform P waves before each QRS confirms the impulse
originated in the SA node. The patient is asymptomatic. Normal sinus rhythm requires a
rate of 60–100 bpm. Sinus arrhythmia would show irregularity, and sinus tachycardia
would have a rate >100 bpm .
3. A patient presents with a heart rate of 145 bpm, regular
rhythm, and upright P waves preceding each QRS complex. The
PR interval is 0.14 seconds. What is the rhythm?
A. Sinus tachycardia
B. Supraventricular tachycardia
C. Atrial flutter
D. Ventricular tachycardia
Answer: A
Rationale: Sinus tachycardia is identified by a regular rhythm, normal P-wave
morphology, and rates typically between 100–150 bpm. Upright, uniform P waves
preceding each QRS confirm sinus origin. While supraventricular tachycardia can also
present with tachycardia, the presence of distinct upright P waves makes sinus
tachycardia the correct interpretation. Atrial flutter would show saw-tooth flutter waves,
and ventricular tachycardia would show wide QRS complexes .
4. An ECG strip shows an irregularly irregular rhythm with a rate
of 78 bpm. The rhythm varies with the respiratory cycle, and all P
waves are upright and uniform. What is the most likely rhythm?
A. Atrial fibrillation
B. Sinus arrhythmia
,C. Sinus bradycardia
D. Wandering atrial pacemaker
Answer: B
Rationale: Sinus arrhythmia is characterized by an irregularly irregular rhythm where the
heart rate varies with the respiratory cycle (increases with inspiration, decreases with
expiration). All P waves originate from the sinus node and are upright and uniform.
Atrial fibrillation shows no P waves and a grossly irregular rhythm. Wandering atrial
pacemaker would show varying P-wave morphology .
5. The normal PR interval should measure between:
A. 0.04–0.08 seconds
B. 0.08–0.12 seconds
C. 0.12–0.20 seconds
D. 0.20–0.30 seconds
Answer: C
Rationale: The PR interval represents conduction from the atria through the AV node
and His-Purkinje system before ventricular depolarization. The normal PR interval is
0.12–0.20 seconds (3–5 small boxes). A prolonged PR interval suggests first-degree AV
block. A shortened PR interval may indicate pre-excitation (WPW syndrome) or
junctional rhythm .
6. What is the normal duration of the QRS complex?
A. <0.06 seconds
B. <0.12 seconds
C. 0.12–0.20 seconds
D. 0.20–0.40 seconds
Answer: B
Rationale: The QRS complex represents ventricular depolarization. The normal QRS
duration is <0.12 seconds (less than 3 small boxes). A QRS duration >0.12 seconds
indicates a bundle branch block or ventricular origin of the rhythm .
, 7. Which of the following is NOT a criterion for normal sinus
rhythm?
A. Rate between 60–100 bpm
B. PR interval 0.12–0.20 seconds
C. P waves upright in lead II
D. QRS duration >0.12 seconds
Answer: D
Rationale: Normal sinus rhythm requires a rate of 60–100 bpm, a PR interval of 0.12–
0.20 seconds, upright P waves in lead II, and a QRS duration of <0.12 seconds. A QRS
duration >0.12 seconds is not a criterion for normal sinus rhythm and indicates a
conduction abnormality .
8. A patient on a cardiac monitor shows a regular rhythm at 75
bpm with upright P waves. Suddenly, a pause occurs on the
monitor with no P wave or QRS complex for 2 seconds. After the
pause, the rhythm resumes at 75 bpm. This is most consistent
with:
A. Second-degree AV block type II
B. Sinus arrest
C. Sinus block
D. Premature atrial contraction
Answer: B
Rationale: Sinus arrest is characterized by a sudden pause in the sinus rhythm with no P
wave, QRS, or T wave. The pause length is not a multiple of the baseline R-R interval.
The underlying rhythm resumes after the pause. Sinus block would show a pause that is
a multiple of the baseline R-R interval. Premature atrial contractions are early beats, not
pauses .
9. How do you calculate the length of a pause during sinus arrest?
A. Count the R waves in the pause and multiply by 0.02 seconds
B. Count the number of large boxes between the R waves that come right before and
