ECG Interpretation and Dysrhythmia
Analysis Practice Exam questions and
correct answers– Updated 2026 (Graded A+)
instant download pdf
Subject: Cardiac Electrophysiology and ECG Interpretation
Subtopic: Cardiac Electrophysiology
Question 1: A patient develops progressive slowing of conduction through the atrioventricular
node due to increased vagal stimulation. Which ECG change would MOST likely occur first?
A) Widening of the QRS complex beyond 0.12 seconds
B) Progressive prolongation of the PR interval
C) Development of pathologic Q waves
D) Inversion of the T wave
Correct Answer: B - Progressive prolongation of the PR interval
Rationale: The AV node is particularly sensitive to vagal stimulation. Increased parasympathetic
tone slows AV nodal conduction, resulting in PR interval prolongation. QRS widening generally
reflects ventricular conduction abnormalities. Pathologic Q waves indicate myocardial necrosis,
while T-wave inversion commonly reflects repolarization abnormalities or ischemia.
Question 2: During depolarization, the primary movement responsible for the P wave is:
A) Ventricular repolarization
B) Atrial depolarization
C) AV nodal repolarization
D) Ventricular depolarization
Correct Answer: B - Atrial depolarization
Rationale: The P wave represents atrial depolarization as impulses spread from the sinoatrial
node through the atria. Ventricular depolarization produces the QRS complex, while ventricular
repolarization generates the T wave. AV nodal activity is generally not visible on the surface
ECG.
Question 3: A patient demonstrates a heart rate of 54 beats/minute with a regular rhythm, upright
P waves preceding every QRS complex, and a PR interval of 0.16 seconds. Which rhythm is
MOST likely present?
,A) Junctional rhythm
B) Sinus bradycardia
C) First-degree AV block
D) Idioventricular rhythm
Correct Answer: B - Sinus bradycardia
Rationale: Sinus bradycardia occurs when the sinus node generates impulses below 60
beats/minute while maintaining normal conduction. First-degree AV block requires a PR interval
exceeding 0.20 seconds. Junctional rhythms typically demonstrate absent or inverted P waves,
and idioventricular rhythms produce wide QRS complexes.
Question 4: Which electrolyte disturbance is MOST associated with peaked T waves and
increased risk of conduction disturbances?
A) Hypokalemia
B) Hyperkalemia
C) Hypocalcemia
D) Hyponatremia
Correct Answer: B - Hyperkalemia
Rationale: Hyperkalemia alters myocardial cell membrane excitability, producing tall peaked T
waves, widening QRS complexes, and eventually severe conduction abnormalities. Hypokalemia
typically produces flattened T waves and U waves. Calcium and sodium abnormalities produce
different ECG findings.
Question 5: A clinician measures a PR interval of 0.28 seconds in a patient whose QRS
complexes occur consistently after every P wave. Which conduction abnormality is present?
A) Second-degree AV block type I
B) First-degree AV block
C) Complete heart block
D) Mobitz type II block
Correct Answer: B - First-degree AV block
Rationale: First-degree AV block is characterized by a prolonged PR interval exceeding 0.20
seconds with consistent conduction of every atrial impulse. Mobitz I and II involve dropped
beats, while complete heart block demonstrates AV dissociation.
Subtopic: Normal Sinus Rhythm
Question 6: Which combination BEST defines normal sinus rhythm?
, A) Rate 40–60 bpm, absent P waves, narrow QRS
B) Rate 60–100 bpm, upright P waves, regular rhythm
C) Rate 100–150 bpm, wide QRS complexes
D) Irregular rhythm with variable PR intervals
Correct Answer: B - Rate 60–100 bpm, upright P waves, regular rhythm
Rationale: Normal sinus rhythm requires a rate between 60 and 100 bpm, consistent upright P
waves preceding each QRS, regular rhythm, and normal conduction intervals. The other options
describe bradyarrhythmias, tachyarrhythmias, or irregular rhythms.
Question 7: A telemetry strip demonstrates identical P waves before each QRS, constant PR
intervals, and a ventricular rate of 88 bpm. Which interpretation is MOST appropriate?
A) Atrial flutter
B) Normal sinus rhythm
C) Accelerated junctional rhythm
D) Multifocal atrial tachycardia
Correct Answer: B - Normal sinus rhythm
Rationale: The presence of uniform P waves, regular rhythm, and a rate within the normal range
strongly supports normal sinus rhythm. The other dysrhythmias demonstrate abnormal atrial
activity or altered pacemaker sites.
Question 8: The sinoatrial node normally functions as the dominant pacemaker because it:
A) Conducts impulses most slowly
B) Possesses the highest intrinsic firing rate
C) Produces the widest QRS complexes
D) Is located within the ventricles
Correct Answer: B - Possesses the highest intrinsic firing rate
Rationale: The SA node normally discharges at 60–100 bpm, exceeding the rates of subsidiary
pacemakers such as the AV junction or ventricles. This higher rate allows the SA node to
suppress lower pacemakers.
Question 9: Which ECG interval represents AV nodal conduction time?
A) QT interval
B) PR interval
C) ST segment
D) QRS duration
Correct Answer: B - PR interval
Analysis Practice Exam questions and
correct answers– Updated 2026 (Graded A+)
instant download pdf
Subject: Cardiac Electrophysiology and ECG Interpretation
Subtopic: Cardiac Electrophysiology
Question 1: A patient develops progressive slowing of conduction through the atrioventricular
node due to increased vagal stimulation. Which ECG change would MOST likely occur first?
A) Widening of the QRS complex beyond 0.12 seconds
B) Progressive prolongation of the PR interval
C) Development of pathologic Q waves
D) Inversion of the T wave
Correct Answer: B - Progressive prolongation of the PR interval
Rationale: The AV node is particularly sensitive to vagal stimulation. Increased parasympathetic
tone slows AV nodal conduction, resulting in PR interval prolongation. QRS widening generally
reflects ventricular conduction abnormalities. Pathologic Q waves indicate myocardial necrosis,
while T-wave inversion commonly reflects repolarization abnormalities or ischemia.
Question 2: During depolarization, the primary movement responsible for the P wave is:
A) Ventricular repolarization
B) Atrial depolarization
C) AV nodal repolarization
D) Ventricular depolarization
Correct Answer: B - Atrial depolarization
Rationale: The P wave represents atrial depolarization as impulses spread from the sinoatrial
node through the atria. Ventricular depolarization produces the QRS complex, while ventricular
repolarization generates the T wave. AV nodal activity is generally not visible on the surface
ECG.
Question 3: A patient demonstrates a heart rate of 54 beats/minute with a regular rhythm, upright
P waves preceding every QRS complex, and a PR interval of 0.16 seconds. Which rhythm is
MOST likely present?
,A) Junctional rhythm
B) Sinus bradycardia
C) First-degree AV block
D) Idioventricular rhythm
Correct Answer: B - Sinus bradycardia
Rationale: Sinus bradycardia occurs when the sinus node generates impulses below 60
beats/minute while maintaining normal conduction. First-degree AV block requires a PR interval
exceeding 0.20 seconds. Junctional rhythms typically demonstrate absent or inverted P waves,
and idioventricular rhythms produce wide QRS complexes.
Question 4: Which electrolyte disturbance is MOST associated with peaked T waves and
increased risk of conduction disturbances?
A) Hypokalemia
B) Hyperkalemia
C) Hypocalcemia
D) Hyponatremia
Correct Answer: B - Hyperkalemia
Rationale: Hyperkalemia alters myocardial cell membrane excitability, producing tall peaked T
waves, widening QRS complexes, and eventually severe conduction abnormalities. Hypokalemia
typically produces flattened T waves and U waves. Calcium and sodium abnormalities produce
different ECG findings.
Question 5: A clinician measures a PR interval of 0.28 seconds in a patient whose QRS
complexes occur consistently after every P wave. Which conduction abnormality is present?
A) Second-degree AV block type I
B) First-degree AV block
C) Complete heart block
D) Mobitz type II block
Correct Answer: B - First-degree AV block
Rationale: First-degree AV block is characterized by a prolonged PR interval exceeding 0.20
seconds with consistent conduction of every atrial impulse. Mobitz I and II involve dropped
beats, while complete heart block demonstrates AV dissociation.
Subtopic: Normal Sinus Rhythm
Question 6: Which combination BEST defines normal sinus rhythm?
, A) Rate 40–60 bpm, absent P waves, narrow QRS
B) Rate 60–100 bpm, upright P waves, regular rhythm
C) Rate 100–150 bpm, wide QRS complexes
D) Irregular rhythm with variable PR intervals
Correct Answer: B - Rate 60–100 bpm, upright P waves, regular rhythm
Rationale: Normal sinus rhythm requires a rate between 60 and 100 bpm, consistent upright P
waves preceding each QRS, regular rhythm, and normal conduction intervals. The other options
describe bradyarrhythmias, tachyarrhythmias, or irregular rhythms.
Question 7: A telemetry strip demonstrates identical P waves before each QRS, constant PR
intervals, and a ventricular rate of 88 bpm. Which interpretation is MOST appropriate?
A) Atrial flutter
B) Normal sinus rhythm
C) Accelerated junctional rhythm
D) Multifocal atrial tachycardia
Correct Answer: B - Normal sinus rhythm
Rationale: The presence of uniform P waves, regular rhythm, and a rate within the normal range
strongly supports normal sinus rhythm. The other dysrhythmias demonstrate abnormal atrial
activity or altered pacemaker sites.
Question 8: The sinoatrial node normally functions as the dominant pacemaker because it:
A) Conducts impulses most slowly
B) Possesses the highest intrinsic firing rate
C) Produces the widest QRS complexes
D) Is located within the ventricles
Correct Answer: B - Possesses the highest intrinsic firing rate
Rationale: The SA node normally discharges at 60–100 bpm, exceeding the rates of subsidiary
pacemakers such as the AV junction or ventricles. This higher rate allows the SA node to
suppress lower pacemakers.
Question 9: Which ECG interval represents AV nodal conduction time?
A) QT interval
B) PR interval
C) ST segment
D) QRS duration
Correct Answer: B - PR interval
