Baylor Scott & White EKG Competency Exam – Baylor
Scott & White Health | 2026 Comprehensive Questions
and Verified Answers .
DOMAIN 1: EKG BASICS & CARDIAC ANATOMY/PHYSIOLOGY (Questions 1-10)
Q1. Which structure serves as the primary pacemaker of the heart, initiating electrical
impulses at a normal rate of 60-100 beats per minute?
A. The atrioventricular (AV) node
B. The sinoatrial (SA) node [CORRECT]
C. The bundle of His
D. The Purkinje fibers
Correct Answer: B
Rationale: The SA node is located in the posterior wall of the right atrium near the superior
vena cava and is the heart's natural pacemaker. The AV node acts as a secondary pacemaker
(40-60 bpm), while the bundle of His and Purkinje fibers serve as tertiary pacemakers (20-40
bpm).
Q2. A 67-year-old patient asks why the EKG shows a "P wave" before each heartbeat. The
nurse explains that the P wave represents:
A. Ventricular depolarization initiated by the bundle branches
B. Atrial depolarization initiated by the SA node [CORRECT]
C. Atrial repolarization hidden within the QRS complex
D. Ventricular repolarization following contraction
Correct Answer: B
Rationale: The P wave represents atrial depolarization initiated by the sinoatrial node. Atrial
repolarization is usually not visible on a standard EKG because it occurs during ventricular
depolarization (QRS complex) and is obscured by the larger electrical forces of the ventricles.
Q3. The PR interval on a 12-lead EKG is measured from the beginning of the P wave to the
beginning of the QRS complex. Which cardiac electrical event does this interval represent?
A. The time for ventricular depolarization only
,B. The time from SA node firing to ventricular depolarization [CORRECT]
C. The duration of ventricular systole
D. The recovery period of the atria
Correct Answer: B
Rationale: The PR interval represents the total time from the beginning of atrial
depolarization (P wave) through conduction across the atria, AV node, bundle of His, and
bundle branches until the onset of ventricular depolarization (QRS complex). Normal PR
interval is 0.12-0.20 seconds (3-5 small boxes).
Q4. On standard EKG paper, each small box (1 mm) represents:
A. 0.04 seconds in time and 0.5 mV in amplitude
B. 0.04 seconds in time and 0.1 mV in amplitude [CORRECT]
C. 0.20 seconds in time and 0.1 mV in amplitude
D. 0.20 seconds in time and 0.5 mV in amplitude
Correct Answer: B
Rationale: Standard EKG paper speed is 25 mm/second, making each small 1 mm box equal to
0.04 seconds. The vertical calibration is 10 mm/mV, making each small box equal to 0.1 mV (1
mm). Large boxes (5 mm) equal 0.20 seconds and 0.5 mV.
Q5. A nurse is measuring the QRS complex on a rhythm strip. The QRS duration is 3 small
boxes wide. What is the duration in seconds, and is this considered normal?
A. 0.12 seconds; normal QRS duration [CORRECT]
B. 0.20 seconds; normal QRS duration
C. 0.12 seconds; prolonged QRS duration indicating bundle branch block
D. 0.20 seconds; prolonged QRS duration requiring immediate intervention
Correct Answer: A
Rationale: At standard paper speed (25 mm/sec), 3 small boxes × 0.04 seconds = 0.12 seconds.
Normal QRS duration is <0.12 seconds (under 3 small boxes). A QRS of exactly 0.12 seconds is
at the upper limit of normal; >0.12 seconds indicates delayed ventricular conduction such as
bundle branch block or ventricular rhythm.
,Q6. Which phase of the cardiac action potential corresponds to the T wave seen on the
surface EKG?
A. Phase 0 - rapid sodium influx and depolarization
B. Phase 1 - early rapid repolarization
C. Phase 2 - plateau phase with calcium influx
D. Phase 3 - rapid potassium efflux and ventricular repolarization [CORRECT]
Correct Answer: D
Rationale: The T wave represents ventricular repolarization (Phase 3 of the action potential),
characterized by potassium efflux from the myocardial cells. Phase 0 corresponds to the QRS
complex (depolarization), while Phase 2 (plateau) corresponds to the ST segment.
Q7. A nursing student asks about the significance of the U wave sometimes seen following the
T wave. The educator correctly explains that:
A. U waves always indicate acute myocardial infarction
B. U waves are prominent hypokalemia and may represent repolarization of the Purkinje
fibers or papillary muscles [CORRECT]
C. U waves are normal variants with no clinical significance
D. U waves indicate impending ventricular fibrillation
Correct Answer: B
Rationale: Prominent U waves are classically associated with hypokalemia, though they may
also be seen in bradycardia, hypercalcemia, or certain medications. While sometimes present
as a normal variant, prominent U waves should prompt electrolyte evaluation, particularly
potassium levels.
Q8. Which structure provides the ONLY normal electrical connection between the atria and
ventricles?
A. The interatrial septum
B. The interventricular septum
C. The atrioventricular (AV) node and bundle of His [CORRECT]
D. The coronary sinus
Correct Answer: C
, Rationale: The AV node and bundle of His form the only normal electrical pathway between
the atria and ventricles. This arrangement allows the atria to contract and complete
ventricular filling before ventricular contraction occurs. Accessory pathways (as in WPW)
bypass this normal connection.
Q9. Calculate the heart rate using the large box method for a rhythm strip showing an R-R
interval of 4 large boxes.
A. 100 beats per minute
B. 85 beats per minute
C. 75 beats per minute [CORRECT]
D. 60 beats per minute
Correct Answer: C
Rationale: The large box method uses the formula: 300 ÷ number of large boxes between R
waves. 300 ÷ 4 = 75 beats per minute. This method is accurate for regular rhythms. Each large
box represents 0.20 seconds (5 small boxes × 0.04 seconds).
Q10. The corrected QT interval (QTc) is calculated to account for heart rate variations. Which
formula is most commonly used for this correction in clinical practice?
A. QTc = QT ÷ √RR (Bazett's formula) [CORRECT]
B. QTc = QT × heart rate
C. QTc = QT + (0.154 × [1 - RR])
D. QTc = QT ÷ heart rate
Correct Answer: A
Rationale: Bazett's formula (QTc = QT / √RR) is the most widely used method for heart rate
correction of the QT interval. Normal QTc is generally <0.44 seconds in men and <0.46 seconds
in women. Fridericia's formula (QTc = QT / ∛RR) is sometimes used as an alternative.
DOMAIN 2: LEAD PLACEMENT & ARTIFACT RECOGNITION (Questions 11-18)
Q11. A nurse is placing the precordial leads (V1-V6) on a 58-year-old male patient. Where
should V1 be positioned?
A. Fourth intercostal space, left sternal border
B. Fourth intercostal space, right sternal border [CORRECT]
Scott & White Health | 2026 Comprehensive Questions
and Verified Answers .
DOMAIN 1: EKG BASICS & CARDIAC ANATOMY/PHYSIOLOGY (Questions 1-10)
Q1. Which structure serves as the primary pacemaker of the heart, initiating electrical
impulses at a normal rate of 60-100 beats per minute?
A. The atrioventricular (AV) node
B. The sinoatrial (SA) node [CORRECT]
C. The bundle of His
D. The Purkinje fibers
Correct Answer: B
Rationale: The SA node is located in the posterior wall of the right atrium near the superior
vena cava and is the heart's natural pacemaker. The AV node acts as a secondary pacemaker
(40-60 bpm), while the bundle of His and Purkinje fibers serve as tertiary pacemakers (20-40
bpm).
Q2. A 67-year-old patient asks why the EKG shows a "P wave" before each heartbeat. The
nurse explains that the P wave represents:
A. Ventricular depolarization initiated by the bundle branches
B. Atrial depolarization initiated by the SA node [CORRECT]
C. Atrial repolarization hidden within the QRS complex
D. Ventricular repolarization following contraction
Correct Answer: B
Rationale: The P wave represents atrial depolarization initiated by the sinoatrial node. Atrial
repolarization is usually not visible on a standard EKG because it occurs during ventricular
depolarization (QRS complex) and is obscured by the larger electrical forces of the ventricles.
Q3. The PR interval on a 12-lead EKG is measured from the beginning of the P wave to the
beginning of the QRS complex. Which cardiac electrical event does this interval represent?
A. The time for ventricular depolarization only
,B. The time from SA node firing to ventricular depolarization [CORRECT]
C. The duration of ventricular systole
D. The recovery period of the atria
Correct Answer: B
Rationale: The PR interval represents the total time from the beginning of atrial
depolarization (P wave) through conduction across the atria, AV node, bundle of His, and
bundle branches until the onset of ventricular depolarization (QRS complex). Normal PR
interval is 0.12-0.20 seconds (3-5 small boxes).
Q4. On standard EKG paper, each small box (1 mm) represents:
A. 0.04 seconds in time and 0.5 mV in amplitude
B. 0.04 seconds in time and 0.1 mV in amplitude [CORRECT]
C. 0.20 seconds in time and 0.1 mV in amplitude
D. 0.20 seconds in time and 0.5 mV in amplitude
Correct Answer: B
Rationale: Standard EKG paper speed is 25 mm/second, making each small 1 mm box equal to
0.04 seconds. The vertical calibration is 10 mm/mV, making each small box equal to 0.1 mV (1
mm). Large boxes (5 mm) equal 0.20 seconds and 0.5 mV.
Q5. A nurse is measuring the QRS complex on a rhythm strip. The QRS duration is 3 small
boxes wide. What is the duration in seconds, and is this considered normal?
A. 0.12 seconds; normal QRS duration [CORRECT]
B. 0.20 seconds; normal QRS duration
C. 0.12 seconds; prolonged QRS duration indicating bundle branch block
D. 0.20 seconds; prolonged QRS duration requiring immediate intervention
Correct Answer: A
Rationale: At standard paper speed (25 mm/sec), 3 small boxes × 0.04 seconds = 0.12 seconds.
Normal QRS duration is <0.12 seconds (under 3 small boxes). A QRS of exactly 0.12 seconds is
at the upper limit of normal; >0.12 seconds indicates delayed ventricular conduction such as
bundle branch block or ventricular rhythm.
,Q6. Which phase of the cardiac action potential corresponds to the T wave seen on the
surface EKG?
A. Phase 0 - rapid sodium influx and depolarization
B. Phase 1 - early rapid repolarization
C. Phase 2 - plateau phase with calcium influx
D. Phase 3 - rapid potassium efflux and ventricular repolarization [CORRECT]
Correct Answer: D
Rationale: The T wave represents ventricular repolarization (Phase 3 of the action potential),
characterized by potassium efflux from the myocardial cells. Phase 0 corresponds to the QRS
complex (depolarization), while Phase 2 (plateau) corresponds to the ST segment.
Q7. A nursing student asks about the significance of the U wave sometimes seen following the
T wave. The educator correctly explains that:
A. U waves always indicate acute myocardial infarction
B. U waves are prominent hypokalemia and may represent repolarization of the Purkinje
fibers or papillary muscles [CORRECT]
C. U waves are normal variants with no clinical significance
D. U waves indicate impending ventricular fibrillation
Correct Answer: B
Rationale: Prominent U waves are classically associated with hypokalemia, though they may
also be seen in bradycardia, hypercalcemia, or certain medications. While sometimes present
as a normal variant, prominent U waves should prompt electrolyte evaluation, particularly
potassium levels.
Q8. Which structure provides the ONLY normal electrical connection between the atria and
ventricles?
A. The interatrial septum
B. The interventricular septum
C. The atrioventricular (AV) node and bundle of His [CORRECT]
D. The coronary sinus
Correct Answer: C
, Rationale: The AV node and bundle of His form the only normal electrical pathway between
the atria and ventricles. This arrangement allows the atria to contract and complete
ventricular filling before ventricular contraction occurs. Accessory pathways (as in WPW)
bypass this normal connection.
Q9. Calculate the heart rate using the large box method for a rhythm strip showing an R-R
interval of 4 large boxes.
A. 100 beats per minute
B. 85 beats per minute
C. 75 beats per minute [CORRECT]
D. 60 beats per minute
Correct Answer: C
Rationale: The large box method uses the formula: 300 ÷ number of large boxes between R
waves. 300 ÷ 4 = 75 beats per minute. This method is accurate for regular rhythms. Each large
box represents 0.20 seconds (5 small boxes × 0.04 seconds).
Q10. The corrected QT interval (QTc) is calculated to account for heart rate variations. Which
formula is most commonly used for this correction in clinical practice?
A. QTc = QT ÷ √RR (Bazett's formula) [CORRECT]
B. QTc = QT × heart rate
C. QTc = QT + (0.154 × [1 - RR])
D. QTc = QT ÷ heart rate
Correct Answer: A
Rationale: Bazett's formula (QTc = QT / √RR) is the most widely used method for heart rate
correction of the QT interval. Normal QTc is generally <0.44 seconds in men and <0.46 seconds
in women. Fridericia's formula (QTc = QT / ∛RR) is sometimes used as an alternative.
DOMAIN 2: LEAD PLACEMENT & ARTIFACT RECOGNITION (Questions 11-18)
Q11. A nurse is placing the precordial leads (V1-V6) on a 58-year-old male patient. Where
should V1 be positioned?
A. Fourth intercostal space, left sternal border
B. Fourth intercostal space, right sternal border [CORRECT]
