Q&A | Cardiac Rhythm
1. A patient's cardiac monitor reveals a regular rhythm with a rate of 48
beats per minute. There is a P wave before each QRS complex, and the PR
interval measures 0.16 seconds. What is the correct interpretation?
A) Normal sinus rhythm
B) Sinus bradycardia
C) Sinus arrhythmia
D) First-degree AV block
Correct Answer: Sinus bradycardia
Rationale: Sinus bradycardia is defined by a regular sinus rhythm with a rate
below 60 beats per minute. The presence of a normal P wave and a normal
PR interval confirms a sinus origin. Normal sinus rhythm would have a rate
between 60-100 bpm, while sinus arrhythmia would have an irregular
rhythm.
2. An ECG tracing demonstrates an irregular rhythm with a rate of 78 beats
per minute. Upright P waves are present, but the R-R intervals vary with the
patient's respiration. What is this rhythm?
A) Sinus arrhythmia
B) Atrial fibrillation
C) Wandering atrial pacemaker
D) Sinus bradycardia
Correct Answer: Sinus arrhythmia
Rationale: Sinus arrhythmia is characterized by a sinus rhythm with a
variable rate, causing irregular R-R intervals that often vary with respiration.
,The P waves are consistent and upright, distinguishing it from atrial
fibrillation (which lacks P waves) and wandering atrial pacemaker (which has
changing P wave morphology).
3. An ECG strip shows a regular rhythm with a heart rate of 115 beats per
minute. There are upright P waves before each QRS complex, and the PR and
QRS intervals are within normal limits. What is the rhythm?
A) Normal sinus rhythm
B) Sinus tachycardia
C) Supraventricular tachycardia
D) Atrial flutter
Correct Answer: Sinus tachycardia
Rationale: Sinus tachycardia is a sinus rhythm with a rate exceeding 100
beats per minute. The presence of normal P waves and normal intervals
confirms the sinus origin. Normal sinus rhythm is 60-100 bpm, while
supraventricular tachycardia typically lacks visible P waves.
4. A patient's ECG reveals a regular rhythm with a rate of 52 beats per
minute. There are no visible P waves, but the QRS complexes are narrow
(0.08 seconds). What is the rhythm?
A) Sinus bradycardia
B) Junctional rhythm
C) Idioventricular rhythm
D) First-degree AV block
Correct Answer: Junctional rhythm
,Rationale: A junctional rhythm originates from the AV junction and typically
has a rate of 40-60 beats per minute. P waves are absent or inverted and
may appear before, during, or after the QRS complex. Idioventricular rhythm
would have wide QRS complexes, and sinus bradycardia would have visible P
waves.
5. An ECG tracing shows a regular rhythm with a heart rate of 180 beats per
minute and a QRS duration of 0.08 seconds. P waves are not visible. What is
the rhythm?
A) Sinus tachycardia
B) Supraventricular tachycardia
C) Atrial fibrillation
D) Ventricular tachycardia
Correct Answer: Supraventricular tachycardia
Rationale: Supraventricular tachycardia is a regular, narrow-complex
tachycardia originating above the ventricles, with a rate typically between
150-350 bpm. P waves are often hidden in the QRS or T waves. Ventricular
tachycardia would have wide QRS complexes.
6. An ECG shows a regular rhythm with a heart rate of 72 beats per minute.
Instead of distinct P waves, there are saw-tooth flutter waves present at a
rate of approximately 300 beats per minute. What is the rhythm?
A) Atrial fibrillation
B) Atrial flutter
C) Supraventricular tachycardia
D) Wandering atrial pacemaker
Correct Answer: Atrial flutter
, Rationale: Atrial flutter is typically a regular rhythm characterized by a saw-
tooth pattern of flutter waves, usually at a rate of 250-350 bpm. The
ventricular rate is a fraction of the atrial rate. Atrial fibrillation lacks
organized flutter waves and has an irregularly irregular rhythm.
7. A patient's monitor displays an irregularly irregular rhythm with a
ventricular rate of 140 beats per minute. No P waves are discernible, and the
baseline is chaotic. What is the rhythm?
A) Atrial flutter
B) Atrial fibrillation with rapid ventricular response
C) Multifocal atrial tachycardia
D) Sinus tachycardia
Correct Answer: Atrial fibrillation with rapid ventricular response
Rationale: Atrial fibrillation with rapid ventricular response is characterized
by an irregularly irregular rhythm, absent P waves, and a ventricular rate
>100 bpm. Atrial flutter typically has a regular rhythm with flutter waves,
and multifocal atrial tachycardia would have multiple P wave morphologies.
8. An ECG tracing reveals a regular rhythm with a heart rate of 45 beats per
minute. There are no visible P waves, but the QRS complexes are wide
(>0.12 seconds). What is the rhythm?
A) Junctional rhythm
B) Idioventricular rhythm
C) Ventricular tachycardia
D) Complete heart block
Correct Answer: Idioventricular rhythm