1
EKG Test Preparation Rhythm Interpretation
Practice Questions and Study Guide Actual
Exam 2026/2027 Complete Exam-Style Questions
with Detailed Rationales | 100% Verified | Pass
Guaranteed – A+ Graded
Part I: EKG Fundamentals, Waveforms & Lead
Placement (Questions 1-15)
Q1: The electrical impulse that initiates each heartbeat
normally originates from which cardiac structure?
A. AV node
B. Bundle of His
C. SA node (sinoatrial node) [CORRECT]
D. Purkinje fibers
Correct Answer: C
Rationale: The SA node, located in the upper right atrium
near the opening of the superior vena cava, is the heart's
natural pacemaker and normally fires at 60-100 beats per
minute. It generates the electrical impulse that spreads
through the atria, causing them to depolarize and contract
before the impulse travels to the AV node.
,2
Q2: On a standard EKG tracing recorded at 25
mm/second, what does one small square (1 mm) on the
horizontal axis represent?
A. 0.04 seconds
B. 0.10 seconds
C. 0.20 seconds
D. 0.40 seconds [CORRECT]
Correct Answer: A
Rationale: At the standard paper speed of 25 mm/sec,
each small 1mm square represents 0.04 seconds (40
milliseconds), and each large square (5mm, made up of 5
small squares) represents 0.20 seconds. This is
foundational knowledge for measuring all EKG intervals
accurately.
Q3: [CLINICAL SCENARIO] You are reviewing an
EKG strip and measure the PR interval at 0.22 seconds
(5.5 small squares). The QRS complex measures 0.08
seconds, and the QT interval appears appropriately
,3
corrected for the rate. How would you document this
finding?
A. Normal EKG with all intervals within limits
B. Prolonged PR interval consistent with first-degree AV
block [CORRECT]
C. Widened QRS indicating bundle branch block
D. Shortened PR interval suggesting pre-excitation
syndrome
Correct Answer: B
Rationale: The normal PR interval range is 0.12–0.20
seconds (3–5 small squares) in adults. A PR interval of
0.22 seconds exceeds the upper limit of normal, meeting
the diagnostic criteria for first-degree AV block, even
though every P wave is still conducted to the ventricles.
Q4: Which EKG lead placement is CORRECT for lead
V4?
A. Fifth intercostal space at the midclavicular line
[CORRECT]
, 4
B. Fourth intercostal space at the midaxillary line
C. Fifth intercostal space at the anterior axillary line
D. Fourth intercostal space at the left sternal border
Correct Answer: A
Rationale: V4 is placed in the fifth intercostal space at the
midclavicular line. To remember precordial lead
positions: V1 and V2 are at the 4th ICS (right and left
sternal borders respectively), V4 is at the 5th ICS
midclavicular line, V3 goes midway between V2 and V4,
V5 is at the 5th ICS anterior axillary line, and V6 is at the
5th ICS midaxillary line.
Q5: The P wave on an EKG represents what electrical
event in the heart?
A. Ventricular depolarization
B. Atrial depolarization [CORRECT]
C. Ventricular repolarization
D. Atrial repolarization
EKG Test Preparation Rhythm Interpretation
Practice Questions and Study Guide Actual
Exam 2026/2027 Complete Exam-Style Questions
with Detailed Rationales | 100% Verified | Pass
Guaranteed – A+ Graded
Part I: EKG Fundamentals, Waveforms & Lead
Placement (Questions 1-15)
Q1: The electrical impulse that initiates each heartbeat
normally originates from which cardiac structure?
A. AV node
B. Bundle of His
C. SA node (sinoatrial node) [CORRECT]
D. Purkinje fibers
Correct Answer: C
Rationale: The SA node, located in the upper right atrium
near the opening of the superior vena cava, is the heart's
natural pacemaker and normally fires at 60-100 beats per
minute. It generates the electrical impulse that spreads
through the atria, causing them to depolarize and contract
before the impulse travels to the AV node.
,2
Q2: On a standard EKG tracing recorded at 25
mm/second, what does one small square (1 mm) on the
horizontal axis represent?
A. 0.04 seconds
B. 0.10 seconds
C. 0.20 seconds
D. 0.40 seconds [CORRECT]
Correct Answer: A
Rationale: At the standard paper speed of 25 mm/sec,
each small 1mm square represents 0.04 seconds (40
milliseconds), and each large square (5mm, made up of 5
small squares) represents 0.20 seconds. This is
foundational knowledge for measuring all EKG intervals
accurately.
Q3: [CLINICAL SCENARIO] You are reviewing an
EKG strip and measure the PR interval at 0.22 seconds
(5.5 small squares). The QRS complex measures 0.08
seconds, and the QT interval appears appropriately
,3
corrected for the rate. How would you document this
finding?
A. Normal EKG with all intervals within limits
B. Prolonged PR interval consistent with first-degree AV
block [CORRECT]
C. Widened QRS indicating bundle branch block
D. Shortened PR interval suggesting pre-excitation
syndrome
Correct Answer: B
Rationale: The normal PR interval range is 0.12–0.20
seconds (3–5 small squares) in adults. A PR interval of
0.22 seconds exceeds the upper limit of normal, meeting
the diagnostic criteria for first-degree AV block, even
though every P wave is still conducted to the ventricles.
Q4: Which EKG lead placement is CORRECT for lead
V4?
A. Fifth intercostal space at the midclavicular line
[CORRECT]
, 4
B. Fourth intercostal space at the midaxillary line
C. Fifth intercostal space at the anterior axillary line
D. Fourth intercostal space at the left sternal border
Correct Answer: A
Rationale: V4 is placed in the fifth intercostal space at the
midclavicular line. To remember precordial lead
positions: V1 and V2 are at the 4th ICS (right and left
sternal borders respectively), V4 is at the 5th ICS
midclavicular line, V3 goes midway between V2 and V4,
V5 is at the 5th ICS anterior axillary line, and V6 is at the
5th ICS midaxillary line.
Q5: The P wave on an EKG represents what electrical
event in the heart?
A. Ventricular depolarization
B. Atrial depolarization [CORRECT]
C. Ventricular repolarization
D. Atrial repolarization
