EKG Test Preparation | Rhythm Interpretation
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1. Which component of the cardiac conduction system normally
serves as the heart’s primary pacemaker?
A. Atrioventricular (AV) node
B. Bundle of His
C. Sinoatrial (SA) node
D. Purkinje fibers
Rationale: The SA node normally generates the fastest intrinsic
electrical impulses, typically 60–100 beats/minute, and initiates the
impulse that spreads through the atria before reaching the AV node.
2. On a standard EKG, what does the P wave represent?
A. Ventricular repolarization
B. Ventricular depolarization
,C. Atrial depolarization
D. AV nodal conduction
Rationale: The P wave represents electrical activation, or
depolarization, of the atria. A normal sinus rhythm generally has one P
wave preceding each QRS complex.
3. What does the QRS complex primarily represent?
A. Atrial repolarization
B. Ventricular depolarization
C. Ventricular repolarization
D. Atrial contraction
Rationale: The QRS complex represents ventricular depolarization. Atrial
repolarization occurs at approximately the same time and is usually
hidden within the QRS complex.
4. The T wave normally represents:
A. Atrial depolarization
B. AV nodal delay
C. Ventricular depolarization
D. Ventricular repolarization
Rationale: The T wave represents recovery, or repolarization, of the
ventricles after ventricular depolarization.
, 5. What is the normal PR interval on a standard EKG?
A. 0.04–0.08 seconds
B. 0.12–0.20 seconds
C. 0.22–0.30 seconds
D. 0.30–0.40 seconds
Rationale: A normal PR interval is 0.12–0.20 seconds. It reflects
conduction from the beginning of atrial depolarization through the AV
node and His-Purkinje system to the ventricles.
6. A QRS duration of 0.14 seconds is best described as:
A. Normal
B. Borderline sinus rhythm
C. Wide
D. Prolonged PR conduction
Rationale: A QRS duration greater than approximately 0.12 seconds is
considered wide. A wide QRS may occur with bundle branch block,
ventricular rhythms, or other forms of abnormal ventricular conduction.
7. At a standard EKG paper speed of 25 mm/second, one small box
represents:
A. 0.01 second
B. 0.04 second
, C. 0.10 second
D. 0.20 second
Rationale: At 25 mm/second, each 1-mm small box represents 0.04
second. Five small boxes make one large box, representing 0.20 second.
8. At standard EKG calibration, five small boxes horizontally
represent:
A. 0.04 second
B. 0.10 second
C. 0.20 second
D. 1.00 second
Rationale: Five small boxes equal one large box. Since each small box
represents 0.04 second, one large box represents 0.20 second.
9. Which heart rate is generally considered normal for an adult sinus
rhythm?
A. 20–40 beats/minute
B. 40–59 beats/minute
C. 60–100 beats/minute
D. 110–150 beats/minute
exam Questions and Correct Answers (Verified
Answers) Plus Rationale 2027 Q&A| Instant
Download Pdf
1. Which component of the cardiac conduction system normally
serves as the heart’s primary pacemaker?
A. Atrioventricular (AV) node
B. Bundle of His
C. Sinoatrial (SA) node
D. Purkinje fibers
Rationale: The SA node normally generates the fastest intrinsic
electrical impulses, typically 60–100 beats/minute, and initiates the
impulse that spreads through the atria before reaching the AV node.
2. On a standard EKG, what does the P wave represent?
A. Ventricular repolarization
B. Ventricular depolarization
,C. Atrial depolarization
D. AV nodal conduction
Rationale: The P wave represents electrical activation, or
depolarization, of the atria. A normal sinus rhythm generally has one P
wave preceding each QRS complex.
3. What does the QRS complex primarily represent?
A. Atrial repolarization
B. Ventricular depolarization
C. Ventricular repolarization
D. Atrial contraction
Rationale: The QRS complex represents ventricular depolarization. Atrial
repolarization occurs at approximately the same time and is usually
hidden within the QRS complex.
4. The T wave normally represents:
A. Atrial depolarization
B. AV nodal delay
C. Ventricular depolarization
D. Ventricular repolarization
Rationale: The T wave represents recovery, or repolarization, of the
ventricles after ventricular depolarization.
, 5. What is the normal PR interval on a standard EKG?
A. 0.04–0.08 seconds
B. 0.12–0.20 seconds
C. 0.22–0.30 seconds
D. 0.30–0.40 seconds
Rationale: A normal PR interval is 0.12–0.20 seconds. It reflects
conduction from the beginning of atrial depolarization through the AV
node and His-Purkinje system to the ventricles.
6. A QRS duration of 0.14 seconds is best described as:
A. Normal
B. Borderline sinus rhythm
C. Wide
D. Prolonged PR conduction
Rationale: A QRS duration greater than approximately 0.12 seconds is
considered wide. A wide QRS may occur with bundle branch block,
ventricular rhythms, or other forms of abnormal ventricular conduction.
7. At a standard EKG paper speed of 25 mm/second, one small box
represents:
A. 0.01 second
B. 0.04 second
, C. 0.10 second
D. 0.20 second
Rationale: At 25 mm/second, each 1-mm small box represents 0.04
second. Five small boxes make one large box, representing 0.20 second.
8. At standard EKG calibration, five small boxes horizontally
represent:
A. 0.04 second
B. 0.10 second
C. 0.20 second
D. 1.00 second
Rationale: Five small boxes equal one large box. Since each small box
represents 0.04 second, one large box represents 0.20 second.
9. Which heart rate is generally considered normal for an adult sinus
rhythm?
A. 20–40 beats/minute
B. 40–59 beats/minute
C. 60–100 beats/minute
D. 110–150 beats/minute
