ECG Interpretation Certification Exam
Practice Questions And Correct Answers
(Verified Answers) Plus Rationales 2027
Q&A | Instant Download Pdf
1. Which ECG component represents atrial depolarization?
A. QRS complex
B. P wave
C. T wave
D. U wave
Rationale: The P wave represents the electrical depolarization of the atria,
normally beginning in the sinoatrial node and spreading through the atrial
myocardium.
2. What does the QRS complex primarily represent?
A. Atrial repolarization only
B. Ventricular repolarization
,C. Ventricular depolarization
D. AV nodal delay
Rationale: The QRS complex represents ventricular depolarization and
normally precedes ventricular mechanical contraction.
3. Which ECG component primarily represents ventricular
repolarization?
A. P wave
B. PR interval
C. QRS complex
D. T wave
Rationale: The T wave reflects ventricular repolarization after ventricular
depolarization has occurred.
4. What does the PR interval measure?
A. Ventricular depolarization to ventricular repolarization
B. The interval from the onset of atrial depolarization to the onset of
ventricular depolarization
C. Ventricular repolarization only
D. The duration of the QRS complex
,Rationale: The PR interval includes atrial conduction, AV nodal conduction,
and His-Purkinje conduction up to the beginning of ventricular
depolarization.
5. Which ECG feature is most characteristic of normal sinus rhythm?
A. Absent P waves and irregularly irregular R-R intervals
B. Wide QRS complexes with AV dissociation
C. Upright P waves in appropriate leads, consistent P-to-QRS relationships,
and a regular rhythm originating from the sinus node
D. Progressive PR prolongation followed by dropped QRS complexes
Rationale: Normal sinus rhythm originates from the sinus node and
produces organized atrial depolarization followed by consistent ventricular
activation.
6. Which lead is commonly used as a practical rhythm-monitoring lead
because it frequently provides clear visualization of P waves and QRS
complexes?
A. aVR exclusively
B. Lead II
C. V1 exclusively
D. aVL exclusively
, Rationale: Lead II often displays atrial activity clearly because the normal
atrial depolarization vector is generally directed toward the positive
electrode of lead II.
7. What is the normal electrical axis of ventricular depolarization in the
frontal plane approximately?
A. −90° to −180°
B. About −30° to +90°
C. +120° to +180° only
D. Exactly 0° in every healthy adult
Rationale: The commonly accepted normal QRS axis is approximately −30°
to +90°, although definitions can vary slightly by reference and clinical
context.
8. What does left axis deviation generally indicate on an ECG?
A. A QRS axis between +120° and +180°
B. A QRS axis more negative than approximately −30°
C. A normal sinus rhythm
D. Complete absence of ventricular depolarization
Rationale: Left axis deviation generally refers to a QRS axis below
approximately −30° in the frontal plane.
9. What does right axis deviation generally indicate?
Practice Questions And Correct Answers
(Verified Answers) Plus Rationales 2027
Q&A | Instant Download Pdf
1. Which ECG component represents atrial depolarization?
A. QRS complex
B. P wave
C. T wave
D. U wave
Rationale: The P wave represents the electrical depolarization of the atria,
normally beginning in the sinoatrial node and spreading through the atrial
myocardium.
2. What does the QRS complex primarily represent?
A. Atrial repolarization only
B. Ventricular repolarization
,C. Ventricular depolarization
D. AV nodal delay
Rationale: The QRS complex represents ventricular depolarization and
normally precedes ventricular mechanical contraction.
3. Which ECG component primarily represents ventricular
repolarization?
A. P wave
B. PR interval
C. QRS complex
D. T wave
Rationale: The T wave reflects ventricular repolarization after ventricular
depolarization has occurred.
4. What does the PR interval measure?
A. Ventricular depolarization to ventricular repolarization
B. The interval from the onset of atrial depolarization to the onset of
ventricular depolarization
C. Ventricular repolarization only
D. The duration of the QRS complex
,Rationale: The PR interval includes atrial conduction, AV nodal conduction,
and His-Purkinje conduction up to the beginning of ventricular
depolarization.
5. Which ECG feature is most characteristic of normal sinus rhythm?
A. Absent P waves and irregularly irregular R-R intervals
B. Wide QRS complexes with AV dissociation
C. Upright P waves in appropriate leads, consistent P-to-QRS relationships,
and a regular rhythm originating from the sinus node
D. Progressive PR prolongation followed by dropped QRS complexes
Rationale: Normal sinus rhythm originates from the sinus node and
produces organized atrial depolarization followed by consistent ventricular
activation.
6. Which lead is commonly used as a practical rhythm-monitoring lead
because it frequently provides clear visualization of P waves and QRS
complexes?
A. aVR exclusively
B. Lead II
C. V1 exclusively
D. aVL exclusively
, Rationale: Lead II often displays atrial activity clearly because the normal
atrial depolarization vector is generally directed toward the positive
electrode of lead II.
7. What is the normal electrical axis of ventricular depolarization in the
frontal plane approximately?
A. −90° to −180°
B. About −30° to +90°
C. +120° to +180° only
D. Exactly 0° in every healthy adult
Rationale: The commonly accepted normal QRS axis is approximately −30°
to +90°, although definitions can vary slightly by reference and clinical
context.
8. What does left axis deviation generally indicate on an ECG?
A. A QRS axis between +120° and +180°
B. A QRS axis more negative than approximately −30°
C. A normal sinus rhythm
D. Complete absence of ventricular depolarization
Rationale: Left axis deviation generally refers to a QRS axis below
approximately −30° in the frontal plane.
9. What does right axis deviation generally indicate?
