APEX EKG TEST EXAM – 350+ QUESTIONS
WITH CORRECT ANSWERS & RATIONALES
1. What does the Q wave represent on an ECG?
A) Depolarization of the AV node
B) The first negative deflection of the QRS complex
C) Ventricular repolarization
D) Atrial depolarization
Correct Answer: B) The first negative deflection of the QRS complex
Rationale: The Q wave is the initial negative deflection of the QRS complex
representing septal depolarization. It indicates the beginning of ventricular
depolarization .
2. Which interval reflects the time from the start of ventricular
depolarization to the end of ventricular repolarization?
A) PR interval
B) QT interval
C) ST segment
D) RR interval
Correct Answer: B) QT interval
Rationale: The QT interval represents the total time for ventricular
depolarization and repolarization. It extends from the beginning of the QRS
complex to the end of the T wave .
3. Which lead has a normally negative P wave and QRS complex?
,A) Lead I
B) Lead II
C) Lead aVR
D) Lead V5
Correct Answer: C) Lead aVR
Rationale: Lead aVR views the heart from the right shoulder and normally
shows negative deflections for the P wave and QRS complex because the
electrical activity moves away from this lead .
4. How is the R wave progression described from V1 to V6?
A) R waves decrease from V1 to V6
B) R waves increase from V1 to V5, then variable at V6
C) R waves are equal in all leads
D) R waves are absent in V1 to V3
Correct Answer: B) R waves increase from V1 to V5, then variable at V6
Rationale: R waves normally become taller from V1 to V5 as the electrical
signal moves toward the left ventricle, with the amplitude being variable at
V6 .
5. Which ion is responsible for phase 0 (rapid depolarization) in
ventricular myocytes?
A) Calcium
B) Sodium
C) Potassium
D) Chloride
,Correct Answer: B) Sodium
Rationale: Fast sodium channels mediate phase 0 in ventricular and Purkinje
cells. Calcium mediates phase 0 in the SA and AV nodes .
6. The absolute refractory period corresponds to which part of the
ECG?
A) P wave through beginning of QRS
B) QRS through peak of T wave
C) End of T wave to next P wave
D) PR interval
Correct Answer: B) QRS through peak of T wave
Rationale: The absolute refractory period extends from the beginning of the
QRS to the peak of the T wave. During this time, the cardiac cell cannot be
depolarized by any stimulus, preventing re-entrant arrhythmias .
7. Which statement about normal Q waves is correct?
A) Q waves should be >0.04 seconds wide
B) Q waves should not exceed 1/3 of the R wave amplitude
C) Q waves should be >1/3 of the R wave amplitude
D) Q waves should be >3 mm deep
Correct Answer: B) Q waves should not exceed 1/3 of the R wave
amplitude
Rationale: Normal Q waves are small (<0.04 seconds wide, <1/3 of the R
wave amplitude, and <3 mm deep). Pathologic Q waves indicate prior
myocardial infarction .
, 8. Which ECG feature is characteristic of hypokalemia?
A) Peaked T waves
B) Short QT interval
C) U waves
D) PR interval depression
Correct Answer: C) U waves
Rationale: Hypokalemia causes prominent U waves, T wave flattening, ST
depression, and prolonged QT intervals. Peaked T waves are seen in
hyperkalemia .
9. Which ECG feature is characteristic of hyperkalemia?
A) Prominent U waves
B) Narrow, peaked T waves
C) Prolonged QT interval
D) ST depression
Correct Answer: B) Narrow, peaked T waves
Rationale: Hyperkalemia causes tall, peaked (tented) T waves, PR
prolongation, and widening of the QRS complex. Prominent U waves are seen
in hypokalemia .
10. Which ECG change is associated with pericarditis?
A) Delta wave
B) Peaked T wave
WITH CORRECT ANSWERS & RATIONALES
1. What does the Q wave represent on an ECG?
A) Depolarization of the AV node
B) The first negative deflection of the QRS complex
C) Ventricular repolarization
D) Atrial depolarization
Correct Answer: B) The first negative deflection of the QRS complex
Rationale: The Q wave is the initial negative deflection of the QRS complex
representing septal depolarization. It indicates the beginning of ventricular
depolarization .
2. Which interval reflects the time from the start of ventricular
depolarization to the end of ventricular repolarization?
A) PR interval
B) QT interval
C) ST segment
D) RR interval
Correct Answer: B) QT interval
Rationale: The QT interval represents the total time for ventricular
depolarization and repolarization. It extends from the beginning of the QRS
complex to the end of the T wave .
3. Which lead has a normally negative P wave and QRS complex?
,A) Lead I
B) Lead II
C) Lead aVR
D) Lead V5
Correct Answer: C) Lead aVR
Rationale: Lead aVR views the heart from the right shoulder and normally
shows negative deflections for the P wave and QRS complex because the
electrical activity moves away from this lead .
4. How is the R wave progression described from V1 to V6?
A) R waves decrease from V1 to V6
B) R waves increase from V1 to V5, then variable at V6
C) R waves are equal in all leads
D) R waves are absent in V1 to V3
Correct Answer: B) R waves increase from V1 to V5, then variable at V6
Rationale: R waves normally become taller from V1 to V5 as the electrical
signal moves toward the left ventricle, with the amplitude being variable at
V6 .
5. Which ion is responsible for phase 0 (rapid depolarization) in
ventricular myocytes?
A) Calcium
B) Sodium
C) Potassium
D) Chloride
,Correct Answer: B) Sodium
Rationale: Fast sodium channels mediate phase 0 in ventricular and Purkinje
cells. Calcium mediates phase 0 in the SA and AV nodes .
6. The absolute refractory period corresponds to which part of the
ECG?
A) P wave through beginning of QRS
B) QRS through peak of T wave
C) End of T wave to next P wave
D) PR interval
Correct Answer: B) QRS through peak of T wave
Rationale: The absolute refractory period extends from the beginning of the
QRS to the peak of the T wave. During this time, the cardiac cell cannot be
depolarized by any stimulus, preventing re-entrant arrhythmias .
7. Which statement about normal Q waves is correct?
A) Q waves should be >0.04 seconds wide
B) Q waves should not exceed 1/3 of the R wave amplitude
C) Q waves should be >1/3 of the R wave amplitude
D) Q waves should be >3 mm deep
Correct Answer: B) Q waves should not exceed 1/3 of the R wave
amplitude
Rationale: Normal Q waves are small (<0.04 seconds wide, <1/3 of the R
wave amplitude, and <3 mm deep). Pathologic Q waves indicate prior
myocardial infarction .
, 8. Which ECG feature is characteristic of hypokalemia?
A) Peaked T waves
B) Short QT interval
C) U waves
D) PR interval depression
Correct Answer: C) U waves
Rationale: Hypokalemia causes prominent U waves, T wave flattening, ST
depression, and prolonged QT intervals. Peaked T waves are seen in
hyperkalemia .
9. Which ECG feature is characteristic of hyperkalemia?
A) Prominent U waves
B) Narrow, peaked T waves
C) Prolonged QT interval
D) ST depression
Correct Answer: B) Narrow, peaked T waves
Rationale: Hyperkalemia causes tall, peaked (tented) T waves, PR
prolongation, and widening of the QRS complex. Prominent U waves are seen
in hypokalemia .
10. Which ECG change is associated with pericarditis?
A) Delta wave
B) Peaked T wave
