APEX EKG TEST EXAM – 250+ QUESTIONS WITH
CORRECT ANSWERS & RATIONALES
1. The EKG shows a regular rhythm with a rate of 180 bpm, no visible P waves, and
a very narrow QRS complex (<0.08 sec). This is most likely:
A) Ventricular Tachycardia
B) Atrial Fibrillation
C) Supraventricular Tachycardia (SVT)
D) Normal Sinus Rhythm
Correct Answer: C) Supraventricular Tachycardia (SVT)
Rationale: SVT originates above the ventricles, resulting in a very fast rate (>160 bpm)
with a narrow QRS complex. P waves are often hidden in the T waves of the preceding
beat .
2. A 71-year-old female patient with CHF exacerbation has a new murmur. During
which phase of the cardiac cycle would you anticipate auscultation of an S3 or S4
heart sound?
A) Systole
B) Diastole
C) Atrial contraction
D) Ventricular contraction
Correct Answer: B) Diastole
Rationale: S3 and S4 are diastolic sounds. A new murmur with CHF exacerbation suggests
valvular pathology .
,3. What is the normal QTc interval for adults?
A) Less than 0.36 seconds
B) Less than 0.44 seconds for males and 0.46 seconds for females
C) Less than 0.50 seconds
D) Greater than 0.50 seconds
Correct Answer: B) Less than 0.44 seconds for males and 0.46 seconds for females
Rationale: A prolonged QTc is defined as >0.44 seconds in males and >0.46 seconds in
females .
4. The U wave is thought to represent:
A) Purkinje fiber repolarization
B) Atrial kick
C) His bundle depolarization
D) Septal depolarization
Correct Answer: A) Purkinje fiber repolarization
Rationale: The U wave, when seen, reflects repolarization of the Purkinje fibers. Prominent
U waves may indicate hypokalemia or bradycardia .
5. Which lead is considered the "rhythm strip" lead in most monitors?
A) Lead I
B) Lead II
C) Lead III
D) aVF
Correct Answer: B) Lead II
Rationale: Lead II best visualizes P waves and is typically used for continuous monitoring .
,6. What is the intrinsic firing rate of the AV node?
A) 20-40 bpm
B) 40-60 bpm
C) 60-100 bpm
D) 100-120 bpm
Correct Answer: B) 40-60 bpm
Rationale: The AV node serves as the secondary pacemaker with an intrinsic firing rate of
40–60 bpm .
7. What is the intrinsic firing rate of the Purkinje fibers?
A) 20-40 bpm
B) 40-60 bpm
C) 60-100 bpm
D) 100-120 bpm
Correct Answer: A) 20-40 bpm
Rationale: The Purkinje fibers serve as the tertiary pacemaker with an intrinsic rate of 20–
40 bpm .
8. Which of the following ECG findings is characteristic of Wolff-Parkinson-White
(WPW) syndrome?
A) PR interval >0.20 seconds
B) Delta wave
C) U wave
D) Prolonged QT interval
Correct Answer: B) Delta wave
Rationale: WPW syndrome is characterized by a delta wave (slurred upstroke of the QRS)
and short PR interval (<0.12 sec) due to pre-excitation through an accessory pathway .
, 9. A normal P wave should measure:
A) >0.12 seconds in duration
B) <0.12 seconds in duration
C) Taller than the R wave in lead I
D) Absent throughout the tracing
Correct Answer: B) <0.12 seconds in duration
Rationale: A normal P wave should be <0.12 seconds (<3 small boxes) in duration. A wide
P wave may indicate left atrial enlargement .
10. The vertical axis (amplitude) calibration standard is:
A) 5 mm = 0.5 mV
B) 10 mm = 1 mV
C) 20 mm = 1 mV
D) 5 mm = 2 mV
Correct Answer: B) 10 mm = 1 mV
Rationale: The standard calibration is 10 mm = 1 mV to ensure uniformity across
tracings .
11. Which ion channels primarily generate the upstroke of the QRS complex?
A) Calcium
B) Potassium
C) Sodium
D) Chloride
Correct Answer: C) Sodium
CORRECT ANSWERS & RATIONALES
1. The EKG shows a regular rhythm with a rate of 180 bpm, no visible P waves, and
a very narrow QRS complex (<0.08 sec). This is most likely:
A) Ventricular Tachycardia
B) Atrial Fibrillation
C) Supraventricular Tachycardia (SVT)
D) Normal Sinus Rhythm
Correct Answer: C) Supraventricular Tachycardia (SVT)
Rationale: SVT originates above the ventricles, resulting in a very fast rate (>160 bpm)
with a narrow QRS complex. P waves are often hidden in the T waves of the preceding
beat .
2. A 71-year-old female patient with CHF exacerbation has a new murmur. During
which phase of the cardiac cycle would you anticipate auscultation of an S3 or S4
heart sound?
A) Systole
B) Diastole
C) Atrial contraction
D) Ventricular contraction
Correct Answer: B) Diastole
Rationale: S3 and S4 are diastolic sounds. A new murmur with CHF exacerbation suggests
valvular pathology .
,3. What is the normal QTc interval for adults?
A) Less than 0.36 seconds
B) Less than 0.44 seconds for males and 0.46 seconds for females
C) Less than 0.50 seconds
D) Greater than 0.50 seconds
Correct Answer: B) Less than 0.44 seconds for males and 0.46 seconds for females
Rationale: A prolonged QTc is defined as >0.44 seconds in males and >0.46 seconds in
females .
4. The U wave is thought to represent:
A) Purkinje fiber repolarization
B) Atrial kick
C) His bundle depolarization
D) Septal depolarization
Correct Answer: A) Purkinje fiber repolarization
Rationale: The U wave, when seen, reflects repolarization of the Purkinje fibers. Prominent
U waves may indicate hypokalemia or bradycardia .
5. Which lead is considered the "rhythm strip" lead in most monitors?
A) Lead I
B) Lead II
C) Lead III
D) aVF
Correct Answer: B) Lead II
Rationale: Lead II best visualizes P waves and is typically used for continuous monitoring .
,6. What is the intrinsic firing rate of the AV node?
A) 20-40 bpm
B) 40-60 bpm
C) 60-100 bpm
D) 100-120 bpm
Correct Answer: B) 40-60 bpm
Rationale: The AV node serves as the secondary pacemaker with an intrinsic firing rate of
40–60 bpm .
7. What is the intrinsic firing rate of the Purkinje fibers?
A) 20-40 bpm
B) 40-60 bpm
C) 60-100 bpm
D) 100-120 bpm
Correct Answer: A) 20-40 bpm
Rationale: The Purkinje fibers serve as the tertiary pacemaker with an intrinsic rate of 20–
40 bpm .
8. Which of the following ECG findings is characteristic of Wolff-Parkinson-White
(WPW) syndrome?
A) PR interval >0.20 seconds
B) Delta wave
C) U wave
D) Prolonged QT interval
Correct Answer: B) Delta wave
Rationale: WPW syndrome is characterized by a delta wave (slurred upstroke of the QRS)
and short PR interval (<0.12 sec) due to pre-excitation through an accessory pathway .
, 9. A normal P wave should measure:
A) >0.12 seconds in duration
B) <0.12 seconds in duration
C) Taller than the R wave in lead I
D) Absent throughout the tracing
Correct Answer: B) <0.12 seconds in duration
Rationale: A normal P wave should be <0.12 seconds (<3 small boxes) in duration. A wide
P wave may indicate left atrial enlargement .
10. The vertical axis (amplitude) calibration standard is:
A) 5 mm = 0.5 mV
B) 10 mm = 1 mV
C) 20 mm = 1 mV
D) 5 mm = 2 mV
Correct Answer: B) 10 mm = 1 mV
Rationale: The standard calibration is 10 mm = 1 mV to ensure uniformity across
tracings .
11. Which ion channels primarily generate the upstroke of the QRS complex?
A) Calcium
B) Potassium
C) Sodium
D) Chloride
Correct Answer: C) Sodium
