APEX EKG TEST EXAM – QUESTIONS WITH CORRECT
ANSWERS & RATIONALES | Master ECG Interpretation for
Nursing & Cardiology Certification
Accelerate your cardiac rhythm recognition and pass your
certification with this definitive APEX EKG test preparation guide
packed with real questions, answers, and detailed rationales. This
comprehensive resource covers EKG grid calculations, interval
measurements, advanced cardiac electrophysiology, and complex
arrhythmia interpretation (including heart blocks, AFib, and
telemetry monitoring). It is an essential study tool for nursing
students and telemetry professionals looking to secure a top
grade and clinical confidence
SECTION 1: EKG BASICS & WAVEFORM INTERPRETATION
(Questions 1-50)
QUESTION 1
Each small box on standard EKG paper represents how much time?
A) 0.04 seconds
B) 0.2 seconds
C) 0.4 seconds
D) 1 second
Answer: A) 0.04 seconds
,Rationale: On standard EKG paper running at 25 mm/s, each 1 mm small square equals
0.04 seconds (40 milliseconds). Five small boxes make one large box (0.2 seconds). This is a
fundamental measurement for all EKG interval calculations .
QUESTION 2
What is the standard calibration on EKG paper for amplitude?
A) 5 mm = 0.5 mV
B) 10 mm = 1 mV
C) 20 mm = 1 mV
D) 5 mm = 2 mV
Answer: B) 10 mm = 1 mV
Rationale: The standard calibration is 10 mm = 1 mV to ensure uniformity across
tracings. This allows for consistent measurement of waveform amplitudes and accurate
interpretation of EKG findings .
QUESTION 3
A normal P wave should measure how long in duration?
A) >0.12 seconds
B) <0.12 seconds
C) 0.12-0.20 seconds
D) <0.04 seconds
Answer: B) <0.12 seconds
Rationale: A normal P wave should be <0.12 seconds (<3 small boxes) in duration. A
wide P wave (>0.12 seconds) may indicate left atrial enlargement. P wave amplitude
should be <2.5 mm in the limb leads .
,QUESTION 4
A normal PR interval should measure between:
A) 0.04 and 0.12 seconds
B) 0.12 and 0.20 seconds
C) 0.20 and 0.40 seconds
D) >0.40 seconds
Answer: B) 0.12 and 0.20 seconds
Rationale: The PR interval represents the time from atrial depolarization to the onset of
ventricular depolarization. It corresponds to the delay at the AV node, which allows time
for ventricular filling. The normal range is 0.12-0.20 seconds (3-5 small boxes) .
QUESTION 5
A normal QRS complex duration should be:
A) Less than 0.06 seconds
B) 0.06 to 0.10 seconds
C) 0.12 to 0.20 seconds
D) Greater than 0.20 seconds
Answer: B) 0.06 to 0.10 seconds
Rationale: A normal QRS complex is less than 0.12 seconds (3 small boxes), usually
measuring between 0.06 and 0.10 seconds. This represents normal ventricular
depolarization through the His-Purkinje system. A QRS >0.12 seconds indicates a bundle
branch block or ventricular origin .
QUESTION 6
A normal QT interval should measure between:
A) 0.20 and 0.30 seconds
B) 0.36 and 0.46 seconds
C) 0.46 and 0.56 seconds
D) Greater than 0.56 seconds
, Answer: B) 0.36 and 0.46 seconds
Rationale: The normal QT interval (from start of QRS to end of T wave) measures 0.36-
0.46 seconds. A prolonged QT interval (>0.45 seconds) increases the risk of Torsades de
Pointes, a life-threatening ventricular arrhythmia. Rate correction (QTc) should be used for
accurate assessment .
QUESTION 7
What ion channels primarily generate the upstroke of the QRS complex?
A) Calcium
B) Potassium
C) Sodium
D) Chloride
Answer: C) Sodium
Rationale: Sodium ion channels generate the rapid depolarization (upstroke) of the QRS
complex. Fast sodium channels cause phase 0 in ventricular and Purkinje cells. This rapid
inward sodium current is responsible for the sharp deflection seen in the QRS .
QUESTION 8
What does the T wave represent?
A) Atrial depolarization
B) Ventricular depolarization
C) Ventricular repolarization
D) Atrial repolarization
Answer: C) Ventricular repolarization
Rationale: The T wave reflects ventricular repolarization. It is typically upright, smooth,
and rounded in the limb leads when the rhythm originates from the sinoatrial node.
Changes in T wave morphology can indicate ischemia, electrolyte disturbances, or drug
effects .
ANSWERS & RATIONALES | Master ECG Interpretation for
Nursing & Cardiology Certification
Accelerate your cardiac rhythm recognition and pass your
certification with this definitive APEX EKG test preparation guide
packed with real questions, answers, and detailed rationales. This
comprehensive resource covers EKG grid calculations, interval
measurements, advanced cardiac electrophysiology, and complex
arrhythmia interpretation (including heart blocks, AFib, and
telemetry monitoring). It is an essential study tool for nursing
students and telemetry professionals looking to secure a top
grade and clinical confidence
SECTION 1: EKG BASICS & WAVEFORM INTERPRETATION
(Questions 1-50)
QUESTION 1
Each small box on standard EKG paper represents how much time?
A) 0.04 seconds
B) 0.2 seconds
C) 0.4 seconds
D) 1 second
Answer: A) 0.04 seconds
,Rationale: On standard EKG paper running at 25 mm/s, each 1 mm small square equals
0.04 seconds (40 milliseconds). Five small boxes make one large box (0.2 seconds). This is a
fundamental measurement for all EKG interval calculations .
QUESTION 2
What is the standard calibration on EKG paper for amplitude?
A) 5 mm = 0.5 mV
B) 10 mm = 1 mV
C) 20 mm = 1 mV
D) 5 mm = 2 mV
Answer: B) 10 mm = 1 mV
Rationale: The standard calibration is 10 mm = 1 mV to ensure uniformity across
tracings. This allows for consistent measurement of waveform amplitudes and accurate
interpretation of EKG findings .
QUESTION 3
A normal P wave should measure how long in duration?
A) >0.12 seconds
B) <0.12 seconds
C) 0.12-0.20 seconds
D) <0.04 seconds
Answer: B) <0.12 seconds
Rationale: A normal P wave should be <0.12 seconds (<3 small boxes) in duration. A
wide P wave (>0.12 seconds) may indicate left atrial enlargement. P wave amplitude
should be <2.5 mm in the limb leads .
,QUESTION 4
A normal PR interval should measure between:
A) 0.04 and 0.12 seconds
B) 0.12 and 0.20 seconds
C) 0.20 and 0.40 seconds
D) >0.40 seconds
Answer: B) 0.12 and 0.20 seconds
Rationale: The PR interval represents the time from atrial depolarization to the onset of
ventricular depolarization. It corresponds to the delay at the AV node, which allows time
for ventricular filling. The normal range is 0.12-0.20 seconds (3-5 small boxes) .
QUESTION 5
A normal QRS complex duration should be:
A) Less than 0.06 seconds
B) 0.06 to 0.10 seconds
C) 0.12 to 0.20 seconds
D) Greater than 0.20 seconds
Answer: B) 0.06 to 0.10 seconds
Rationale: A normal QRS complex is less than 0.12 seconds (3 small boxes), usually
measuring between 0.06 and 0.10 seconds. This represents normal ventricular
depolarization through the His-Purkinje system. A QRS >0.12 seconds indicates a bundle
branch block or ventricular origin .
QUESTION 6
A normal QT interval should measure between:
A) 0.20 and 0.30 seconds
B) 0.36 and 0.46 seconds
C) 0.46 and 0.56 seconds
D) Greater than 0.56 seconds
, Answer: B) 0.36 and 0.46 seconds
Rationale: The normal QT interval (from start of QRS to end of T wave) measures 0.36-
0.46 seconds. A prolonged QT interval (>0.45 seconds) increases the risk of Torsades de
Pointes, a life-threatening ventricular arrhythmia. Rate correction (QTc) should be used for
accurate assessment .
QUESTION 7
What ion channels primarily generate the upstroke of the QRS complex?
A) Calcium
B) Potassium
C) Sodium
D) Chloride
Answer: C) Sodium
Rationale: Sodium ion channels generate the rapid depolarization (upstroke) of the QRS
complex. Fast sodium channels cause phase 0 in ventricular and Purkinje cells. This rapid
inward sodium current is responsible for the sharp deflection seen in the QRS .
QUESTION 8
What does the T wave represent?
A) Atrial depolarization
B) Ventricular depolarization
C) Ventricular repolarization
D) Atrial repolarization
Answer: C) Ventricular repolarization
Rationale: The T wave reflects ventricular repolarization. It is typically upright, smooth,
and rounded in the limb leads when the rhythm originates from the sinoatrial node.
Changes in T wave morphology can indicate ischemia, electrolyte disturbances, or drug
effects .
