Relias Dysrhythmia Basic A
– 2025/2026 – complete
Practice Test with Verified
Answers
SECTION 1: ECG FOUNDATIONS & MEASUREMENTS
Question 1
The electrical impulse normally originates from which structure of the heart?
A) AV node
B) Bundle of His
C) SA node
D) Purkinje fibers
Answer: C) SA node
Rationale: The sinoatrial (SA) node, located in the upper wall of the right atrium, is the
heart's natural pacemaker. It normally discharges at 60-100 beats per minute, has the
highest degree of automaticity, and overrides other potential pacemakers. The AV node
,delays impulses (intrinsic rate 40-60 bpm), and Purkinje fibers are the terminal
conduction pathway (intrinsic rate 20-40 bpm).
Question 2
What is the normal intrinsic firing rate of the SA node in a resting adult?
A) 20-40 beats per minute
B) 40-60 beats per minute
C) 60-100 beats per minute
D) 100-150 beats per minute
Answer: C) 60-100 beats per minute
Rationale: The SA node is the primary pacemaker with an intrinsic firing rate of 60-100
bpm. The AV junction has a backup rate of 40-60 bpm, and the Purkinje fibers have an
intrinsic rate of 20-40 bpm. Understanding these rates helps identify escape rhythms
when the primary pacemaker fails.
Question 3
Which component of the ECG represents ventricular depolarization?
A) P wave
B) PR interval
C) QRS complex
D) T wave
Answer: C) QRS complex
Rationale: The QRS complex represents the electrical impulse traveling through the
ventricles, causing them to contract. The P wave represents atrial depolarization, the PR
interval represents the time from the start of atrial depolarization to the start of
ventricular depolarization, and the T wave represents ventricular repolarization.
, Question 4
What is the standard ECG paper speed?
A) 15 mm/second
B) 25 mm/second
C) 50 mm/second
D) 100 mm/second
Answer: B) 25 mm/second
Rationale: The standard recording speed for an ECG is 25 mm per second. At this
speed, each small box (1 mm) represents 0.04 seconds, and each large box (5 mm)
represents 0.20 seconds.
Question 5
On standard ECG paper, 1 small box (1 mm) represents how many seconds?
A) 0.04 seconds
B) 0.10 seconds
C) 0.20 seconds
D) 0.50 seconds
Answer: A) 0.04 seconds
Rationale: At standard speed (25 mm/sec), each small box = 0.04 sec (40 ms). Each
large box (5 small boxes) = 0.20 seconds. This measurement is fundamental for
calculating heart rate and intervals.
Question 6
A normal PR interval should measure:
– 2025/2026 – complete
Practice Test with Verified
Answers
SECTION 1: ECG FOUNDATIONS & MEASUREMENTS
Question 1
The electrical impulse normally originates from which structure of the heart?
A) AV node
B) Bundle of His
C) SA node
D) Purkinje fibers
Answer: C) SA node
Rationale: The sinoatrial (SA) node, located in the upper wall of the right atrium, is the
heart's natural pacemaker. It normally discharges at 60-100 beats per minute, has the
highest degree of automaticity, and overrides other potential pacemakers. The AV node
,delays impulses (intrinsic rate 40-60 bpm), and Purkinje fibers are the terminal
conduction pathway (intrinsic rate 20-40 bpm).
Question 2
What is the normal intrinsic firing rate of the SA node in a resting adult?
A) 20-40 beats per minute
B) 40-60 beats per minute
C) 60-100 beats per minute
D) 100-150 beats per minute
Answer: C) 60-100 beats per minute
Rationale: The SA node is the primary pacemaker with an intrinsic firing rate of 60-100
bpm. The AV junction has a backup rate of 40-60 bpm, and the Purkinje fibers have an
intrinsic rate of 20-40 bpm. Understanding these rates helps identify escape rhythms
when the primary pacemaker fails.
Question 3
Which component of the ECG represents ventricular depolarization?
A) P wave
B) PR interval
C) QRS complex
D) T wave
Answer: C) QRS complex
Rationale: The QRS complex represents the electrical impulse traveling through the
ventricles, causing them to contract. The P wave represents atrial depolarization, the PR
interval represents the time from the start of atrial depolarization to the start of
ventricular depolarization, and the T wave represents ventricular repolarization.
, Question 4
What is the standard ECG paper speed?
A) 15 mm/second
B) 25 mm/second
C) 50 mm/second
D) 100 mm/second
Answer: B) 25 mm/second
Rationale: The standard recording speed for an ECG is 25 mm per second. At this
speed, each small box (1 mm) represents 0.04 seconds, and each large box (5 mm)
represents 0.20 seconds.
Question 5
On standard ECG paper, 1 small box (1 mm) represents how many seconds?
A) 0.04 seconds
B) 0.10 seconds
C) 0.20 seconds
D) 0.50 seconds
Answer: A) 0.04 seconds
Rationale: At standard speed (25 mm/sec), each small box = 0.04 sec (40 ms). Each
large box (5 small boxes) = 0.20 seconds. This measurement is fundamental for
calculating heart rate and intervals.
Question 6
A normal PR interval should measure:
