EKG/ECG INTERPRETATION EXAM STUDY GUIDE
2026 | RHYTHMS & ABNORMALITIES PRACTICE
TEST | 200+ VERIFIED QUESTIONS & ANSWERS
WITH DETAILED RATIONALES | ARRHYTHMIAS,
HEART BLOCKS, ST CHANGES & CLINICAL
ANALYSIS
• This study guide contains 200 verified EKG/ECG questions with detailed EXPERT
RATIONALE to help you master rhythm interpretation, arrhythmias, heart blocks,
ST changes, and clinical analysis for exams and clinical practice.
• Work through each question independently before checking the highlighted
correct answer and EXPERT RATIONALE — this active recall method maximizes
retention and prepares you for real exam conditions.
EKG/ECG INTERPRETATION EXAM STUDY GUIDE 2026
QUESTION 1: What is the normal duration of the PR interval?
A. 0.06 – 0.10 seconds
B. 0.08 – 0.12 seconds
C. 0.12 – 0.20 seconds
D. 0.20 – 0.28 seconds
E. 0.28 – 0.36 seconds
CORRECT ANSWER: C. 0.12 – 0.20 seconds
EXPERT RATIONALE: The normal PR interval ranges from 0.12 to 0.20 seconds
(3–5 small squares on ECG paper). It represents the time taken for the electrical
impulse to travel from the SA node through the AV node and bundle of His to the
ventricles. A PR interval greater than 0.20 seconds indicates a first-degree heart
block.
,QUESTION 2: What is the normal duration of the QRS complex?
A. 0.04 – 0.06 seconds
B. 0.06 – 0.10 seconds
C. 0.10 – 0.12 seconds
D. 0.12 – 0.16 seconds
E. 0.16 – 0.20 seconds
CORRECT ANSWER: B. 0.06 – 0.10 seconds
EXPERT RATIONALE: The normal QRS complex duration is 0.06 to 0.10 seconds
(less than 3 small squares). It represents ventricular depolarization. A QRS wider
than 0.12 seconds suggests a bundle branch block, ventricular rhythm, or aberrant
conduction.
QUESTION 3: The SA node normally fires at what rate?
A. 20 – 40 beats per minute
B. 40 – 60 beats per minute
C. 60 – 100 beats per minute
D. 100 – 150 beats per minute
E. 150 – 200 beats per minute
CORRECT ANSWER: C. 60 – 100 beats per minute
EXPERT RATIONALE: The sinoatrial (SA) node is the primary pacemaker of the
heart and normally fires at 60–100 beats per minute. It is located in the right
atrium. Rates below 60 indicate sinus bradycardia and above 100 indicate sinus
tachycardia.
QUESTION 4: Which wave on the ECG represents ventricular depolarization?
A. P wave
,B. T wave
C. U wave
D. QRS complex
E. PR segment
CORRECT ANSWER: D. QRS complex
EXPERT RATIONALE: The QRS complex represents ventricular depolarization —
the electrical activation of the ventricles that triggers ventricular contraction. The P
wave represents atrial depolarization, the T wave represents ventricular
repolarization, and the U wave is associated with repolarization of the Purkinje
fibers.
QUESTION 5: What does the T wave represent on an ECG?
A. Atrial depolarization
B. Ventricular depolarization
C. Ventricular repolarization
D. Atrial repolarization
E. AV node conduction
CORRECT ANSWER: C. Ventricular repolarization
EXPERT RATIONALE: The T wave represents ventricular repolarization — the
recovery phase of the ventricles after contraction. Abnormalities of the T wave such
as inversion, peaking, or flattening can indicate ischemia, electrolyte imbalances, or
other cardiac pathologies.
QUESTION 6: At a standard ECG paper speed of 25 mm/second, one small
square represents:
A. 0.02 seconds
, B. 0.04 seconds
C. 0.06 seconds
D. 0.08 seconds
E. 0.10 seconds
CORRECT ANSWER: B. 0.04 seconds
EXPERT RATIONALE: At standard ECG paper speed of 25 mm/second, each
small square (1 mm) represents 0.04 seconds. Each large square (5 mm) represents
0.20 seconds. This is fundamental to measuring intervals and durations on the ECG.
QUESTION 7: How do you calculate heart rate using the 300 method on a
regular rhythm?
A. Count QRS complexes in 6 seconds and multiply by 10
B. Divide 1500 by the number of small squares between R-R intervals
C. Divide 300 by the number of large squares between R-R intervals
D. Multiply the PR interval by 100
E. Count P waves in 10 seconds and multiply by 6
CORRECT ANSWER: C. Divide 300 by the number of large squares between
R-R intervals
EXPERT RATIONALE: The 300 method is used for regular rhythms. Count the
number of large squares between two consecutive R waves and divide 300 by that
number. For example, if there are 4 large squares between R waves, the heart rate
is 300 ÷ 4 = 75 bpm.
QUESTION 8: What is the intrinsic firing rate of the AV node?
A. 60 – 100 bpm
B. 100 – 150 bpm
2026 | RHYTHMS & ABNORMALITIES PRACTICE
TEST | 200+ VERIFIED QUESTIONS & ANSWERS
WITH DETAILED RATIONALES | ARRHYTHMIAS,
HEART BLOCKS, ST CHANGES & CLINICAL
ANALYSIS
• This study guide contains 200 verified EKG/ECG questions with detailed EXPERT
RATIONALE to help you master rhythm interpretation, arrhythmias, heart blocks,
ST changes, and clinical analysis for exams and clinical practice.
• Work through each question independently before checking the highlighted
correct answer and EXPERT RATIONALE — this active recall method maximizes
retention and prepares you for real exam conditions.
EKG/ECG INTERPRETATION EXAM STUDY GUIDE 2026
QUESTION 1: What is the normal duration of the PR interval?
A. 0.06 – 0.10 seconds
B. 0.08 – 0.12 seconds
C. 0.12 – 0.20 seconds
D. 0.20 – 0.28 seconds
E. 0.28 – 0.36 seconds
CORRECT ANSWER: C. 0.12 – 0.20 seconds
EXPERT RATIONALE: The normal PR interval ranges from 0.12 to 0.20 seconds
(3–5 small squares on ECG paper). It represents the time taken for the electrical
impulse to travel from the SA node through the AV node and bundle of His to the
ventricles. A PR interval greater than 0.20 seconds indicates a first-degree heart
block.
,QUESTION 2: What is the normal duration of the QRS complex?
A. 0.04 – 0.06 seconds
B. 0.06 – 0.10 seconds
C. 0.10 – 0.12 seconds
D. 0.12 – 0.16 seconds
E. 0.16 – 0.20 seconds
CORRECT ANSWER: B. 0.06 – 0.10 seconds
EXPERT RATIONALE: The normal QRS complex duration is 0.06 to 0.10 seconds
(less than 3 small squares). It represents ventricular depolarization. A QRS wider
than 0.12 seconds suggests a bundle branch block, ventricular rhythm, or aberrant
conduction.
QUESTION 3: The SA node normally fires at what rate?
A. 20 – 40 beats per minute
B. 40 – 60 beats per minute
C. 60 – 100 beats per minute
D. 100 – 150 beats per minute
E. 150 – 200 beats per minute
CORRECT ANSWER: C. 60 – 100 beats per minute
EXPERT RATIONALE: The sinoatrial (SA) node is the primary pacemaker of the
heart and normally fires at 60–100 beats per minute. It is located in the right
atrium. Rates below 60 indicate sinus bradycardia and above 100 indicate sinus
tachycardia.
QUESTION 4: Which wave on the ECG represents ventricular depolarization?
A. P wave
,B. T wave
C. U wave
D. QRS complex
E. PR segment
CORRECT ANSWER: D. QRS complex
EXPERT RATIONALE: The QRS complex represents ventricular depolarization —
the electrical activation of the ventricles that triggers ventricular contraction. The P
wave represents atrial depolarization, the T wave represents ventricular
repolarization, and the U wave is associated with repolarization of the Purkinje
fibers.
QUESTION 5: What does the T wave represent on an ECG?
A. Atrial depolarization
B. Ventricular depolarization
C. Ventricular repolarization
D. Atrial repolarization
E. AV node conduction
CORRECT ANSWER: C. Ventricular repolarization
EXPERT RATIONALE: The T wave represents ventricular repolarization — the
recovery phase of the ventricles after contraction. Abnormalities of the T wave such
as inversion, peaking, or flattening can indicate ischemia, electrolyte imbalances, or
other cardiac pathologies.
QUESTION 6: At a standard ECG paper speed of 25 mm/second, one small
square represents:
A. 0.02 seconds
, B. 0.04 seconds
C. 0.06 seconds
D. 0.08 seconds
E. 0.10 seconds
CORRECT ANSWER: B. 0.04 seconds
EXPERT RATIONALE: At standard ECG paper speed of 25 mm/second, each
small square (1 mm) represents 0.04 seconds. Each large square (5 mm) represents
0.20 seconds. This is fundamental to measuring intervals and durations on the ECG.
QUESTION 7: How do you calculate heart rate using the 300 method on a
regular rhythm?
A. Count QRS complexes in 6 seconds and multiply by 10
B. Divide 1500 by the number of small squares between R-R intervals
C. Divide 300 by the number of large squares between R-R intervals
D. Multiply the PR interval by 100
E. Count P waves in 10 seconds and multiply by 6
CORRECT ANSWER: C. Divide 300 by the number of large squares between
R-R intervals
EXPERT RATIONALE: The 300 method is used for regular rhythms. Count the
number of large squares between two consecutive R waves and divide 300 by that
number. For example, if there are 4 large squares between R waves, the heart rate
is 300 ÷ 4 = 75 bpm.
QUESTION 8: What is the intrinsic firing rate of the AV node?
A. 60 – 100 bpm
B. 100 – 150 bpm
