APEX EKG Exam Prep | 2026/2027 | ECG Rhythm Interpretation
APEX EKG EXAM PREP
2026/2027 | ECG Rhythm Interpretation | 41 Questions with Correct Answers
Graded A+ | 100% Verified | Evidence-Based Rationales
Instructions
This examination consists of 41 multiple-choice questions covering foundational ECG interpretation competencies
across nine domains: ECG paper and measurement fundamentals, normal sinus rhythm and sinus dysrhythmias, atrial
dysrhythmias, junctional dysrhythmias, ventricular dysrhythmias, heart blocks (AV conduction disturbances),
pacemaker rhythms, artifact recognition, and clinical correlation with nursing actions. Correct answers are displayed in
bold cyan with evidence-based rationales aligned to AHA ACLS and AACN standards.
Select the single best answer for each question. Each question is worth one point. A score of 80% (33/41) or higher
indicates competency in ECG rhythm interpretation.
Section I: ECG Paper and Measurement Fundamentals
1. On standard ECG paper, what is the time represented by one small box?
A. 0.02 seconds
B. 0.04 seconds
C. 0.10 seconds
D. 0.20 seconds
Rationale: One small box on standard ECG paper equals 0.04 seconds (1 mm). One large box (5 small boxes)
equals 0.20 seconds. This is foundational for all ECG interval measurements including PR, QRS, and QT
intervals.
2. A nurse counts 8 R-R intervals in 6 seconds on an ECG rhythm strip. What is the approximate heart rate?
A. 48 bpm
B. 60 bpm
C. 80 bpm
D. 96 bpm
Rationale: The 6-second method multiplies the number of R-R intervals in 6 seconds by 10: 8 × 10 = 80 bpm.
This is the most practical bedside method for irregular rhythms and is recommended by AACN for rapid rate
estimation.
3. Using the 1500 method, if the R-R interval measures 20 small boxes, what is the heart rate?
A. 60 bpm
B. 75 bpm
C. 85 bpm
D. 100 bpm
Rationale: The 1500 method divides 1500 by the number of small boxes between R waves: 1500 ÷ 20 = 75 bpm.
This method is most accurate for regular rhythms but becomes unreliable with irregular rhythms.
4. What does one large box on standard ECG paper represent in both time and voltage?
1
, APEX EKG Exam Prep | 2026/2027 | ECG Rhythm Interpretation
A. 0.04 sec, 0.1 mV
B. 0.20 sec, 0.5 mV
C. 0.20 sec, 0.1 mV
D. 0.10 sec, 1.0 mV
Rationale: One large box (5 × 5 small boxes) represents 0.20 seconds horizontally and 0.5 mV vertically on
standard ECG paper at 25 mm/s speed and 10 mm/mV gain. These standards are set by AHA for consistent
interpretation.
5. The triplicate method for heart rate calculation involves counting the number of large boxes between two
consecutive R waves and dividing into:
A. 150
B. 300
C. 1500
D. 60
Rationale: The triplicate method divides 300 by the number of large boxes between R waves. For example, if 4
large boxes separate R waves: 300 ÷ 4 = 75 bpm. This is the fastest bedside estimation for regular rhythms.
Section II: Normal Sinus Rhythm and Sinus Dysrhythmias
6. Which of the following criteria defines Normal Sinus Rhythm (NSR)?
A. Rate 50–90 bpm, regular, P before each QRS, PR 0.12–0.20 sec
B. Rate 60–100 bpm, regular, upright P before each QRS, PR 0.12–0.20 sec, QRS < 0.12 sec
C. Rate 60–100 bpm, irregular, P before each QRS, PR 0.16–0.24 sec
D. Rate 70–120 bpm, regular, no visible P waves, narrow QRS
Rationale: NSR requires all five criteria: rate 60–100 bpm, regular rhythm, upright P wave preceding each QRS
in lead II, PR interval 0.12–0.20 seconds, and QRS duration < 0.12 seconds. Absence of any criterion indicates a
dysrhythmia.
7. A patient's rhythm strip shows a rate of 48 bpm with a regular rhythm, upright P wave before each QRS, and
PR interval of 0.16 sec. This rhythm is identified as:
A. Normal Sinus Rhythm
B. Sinus Bradycardia
C. First-Degree AV Block
D. Sinus Arrhythmia
Rationale: Sinus Bradycardia is characterized by all criteria of NSR except the rate, which is less than 60 bpm
(here 48 bpm). The impulse still originates from the SA node, as evidenced by the upright P wave before each
QRS. It is common in athletes and during sleep.
8. Sinus Tachycardia is defined as a heart rate greater than:
A. 80 bpm originating from the SA node
B. 100 bpm originating from the SA node
C. 120 bpm with irregular R-R intervals
D. 150 bpm with wide QRS complexes
2
APEX EKG EXAM PREP
2026/2027 | ECG Rhythm Interpretation | 41 Questions with Correct Answers
Graded A+ | 100% Verified | Evidence-Based Rationales
Instructions
This examination consists of 41 multiple-choice questions covering foundational ECG interpretation competencies
across nine domains: ECG paper and measurement fundamentals, normal sinus rhythm and sinus dysrhythmias, atrial
dysrhythmias, junctional dysrhythmias, ventricular dysrhythmias, heart blocks (AV conduction disturbances),
pacemaker rhythms, artifact recognition, and clinical correlation with nursing actions. Correct answers are displayed in
bold cyan with evidence-based rationales aligned to AHA ACLS and AACN standards.
Select the single best answer for each question. Each question is worth one point. A score of 80% (33/41) or higher
indicates competency in ECG rhythm interpretation.
Section I: ECG Paper and Measurement Fundamentals
1. On standard ECG paper, what is the time represented by one small box?
A. 0.02 seconds
B. 0.04 seconds
C. 0.10 seconds
D. 0.20 seconds
Rationale: One small box on standard ECG paper equals 0.04 seconds (1 mm). One large box (5 small boxes)
equals 0.20 seconds. This is foundational for all ECG interval measurements including PR, QRS, and QT
intervals.
2. A nurse counts 8 R-R intervals in 6 seconds on an ECG rhythm strip. What is the approximate heart rate?
A. 48 bpm
B. 60 bpm
C. 80 bpm
D. 96 bpm
Rationale: The 6-second method multiplies the number of R-R intervals in 6 seconds by 10: 8 × 10 = 80 bpm.
This is the most practical bedside method for irregular rhythms and is recommended by AACN for rapid rate
estimation.
3. Using the 1500 method, if the R-R interval measures 20 small boxes, what is the heart rate?
A. 60 bpm
B. 75 bpm
C. 85 bpm
D. 100 bpm
Rationale: The 1500 method divides 1500 by the number of small boxes between R waves: 1500 ÷ 20 = 75 bpm.
This method is most accurate for regular rhythms but becomes unreliable with irregular rhythms.
4. What does one large box on standard ECG paper represent in both time and voltage?
1
, APEX EKG Exam Prep | 2026/2027 | ECG Rhythm Interpretation
A. 0.04 sec, 0.1 mV
B. 0.20 sec, 0.5 mV
C. 0.20 sec, 0.1 mV
D. 0.10 sec, 1.0 mV
Rationale: One large box (5 × 5 small boxes) represents 0.20 seconds horizontally and 0.5 mV vertically on
standard ECG paper at 25 mm/s speed and 10 mm/mV gain. These standards are set by AHA for consistent
interpretation.
5. The triplicate method for heart rate calculation involves counting the number of large boxes between two
consecutive R waves and dividing into:
A. 150
B. 300
C. 1500
D. 60
Rationale: The triplicate method divides 300 by the number of large boxes between R waves. For example, if 4
large boxes separate R waves: 300 ÷ 4 = 75 bpm. This is the fastest bedside estimation for regular rhythms.
Section II: Normal Sinus Rhythm and Sinus Dysrhythmias
6. Which of the following criteria defines Normal Sinus Rhythm (NSR)?
A. Rate 50–90 bpm, regular, P before each QRS, PR 0.12–0.20 sec
B. Rate 60–100 bpm, regular, upright P before each QRS, PR 0.12–0.20 sec, QRS < 0.12 sec
C. Rate 60–100 bpm, irregular, P before each QRS, PR 0.16–0.24 sec
D. Rate 70–120 bpm, regular, no visible P waves, narrow QRS
Rationale: NSR requires all five criteria: rate 60–100 bpm, regular rhythm, upright P wave preceding each QRS
in lead II, PR interval 0.12–0.20 seconds, and QRS duration < 0.12 seconds. Absence of any criterion indicates a
dysrhythmia.
7. A patient's rhythm strip shows a rate of 48 bpm with a regular rhythm, upright P wave before each QRS, and
PR interval of 0.16 sec. This rhythm is identified as:
A. Normal Sinus Rhythm
B. Sinus Bradycardia
C. First-Degree AV Block
D. Sinus Arrhythmia
Rationale: Sinus Bradycardia is characterized by all criteria of NSR except the rate, which is less than 60 bpm
(here 48 bpm). The impulse still originates from the SA node, as evidenced by the upright P wave before each
QRS. It is common in athletes and during sleep.
8. Sinus Tachycardia is defined as a heart rate greater than:
A. 80 bpm originating from the SA node
B. 100 bpm originating from the SA node
C. 120 bpm with irregular R-R intervals
D. 150 bpm with wide QRS complexes
2
