Portage Learning CHEM 210 Biochemistry Final – 150-Question Practice

Relias Dysrhythmia Basic A Exam
2026/2027 – 150-Question Practice Exam
(Relias Learning)

Section I: ECG Fundamentals and Waveforms (1–20)
1. Which of the following represents the time from the beginning of atrial depolarization to the
beginning of ventricular depolarization?
A. PR segment
B. PR interval
C. QT interval
D. ST segment

Correct Answer: B
Rationale: The PR interval measures from the start of the P wave to the start of the QRS
complex, representing atrial depolarization plus AV nodal delay.


2. Which segment represents the isoelectric period between the end of the QRS and the
beginning of the T wave?
A. PR segment
B. ST segment
C. TP segment
D. QT interval

Correct Answer: B
Rationale: The ST segment is the isoelectric period between ventricular depolarization and
repolarization.


3. What is the normal duration of the QT interval?
A. 0.12–0.20 seconds
B. 0.20–0.40 seconds
C. 0.36–0.44 seconds
D. 0.44–0.50 seconds

, Correct Answer: C
Rationale: Normal QT interval varies with heart rate but is generally 0.36–0.44 seconds.


4. Which lead is a bipolar limb lead?
A. V1
B. Lead I
C. aVR
D. V6

Correct Answer: B
Rationale: Leads I, II, and III are bipolar limb leads; aVR, aVL, and aVF are unipolar
augmented leads; V leads are precordial.


5. Which lead is an augmented unipolar limb lead?
A. Lead I
B. Lead II
C. aVF
D. V3

Correct Answer: C
Rationale: aVR, aVL, and aVF are augmented unipolar limb leads.


6. What does aVR represent?
A. Right arm
B. Left arm
C. Left leg
D. Right leg

Correct Answer: A
Rationale: aVR is the augmented vector right, primarily reflecting right arm potentials.


7. Which of the following is a precordial lead?
A. Lead I
B. aVL

,C. V4
D. aVF

Correct Answer: C
Rationale: V1–V6 are precordial (chest) leads.


8. Where is V1 placed?
A. Fourth intercostal space, right sternal border
B. Fourth intercostal space, left sternal border
C. Fifth intercostal space, left midclavicular line
D. Fifth intercostal space, left anterior axillary line

Correct Answer: A
Rationale: V1 is placed in the fourth intercostal space at the right sternal border.


9. Where is V6 placed?
A. Fourth intercostal space, right sternal border
B. Fourth intercostal space, left sternal border
C. Fifth intercostal space, left midaxillary line
D. Fifth intercostal space, left anterior axillary line

Correct Answer: C
Rationale: V6 is placed in the fifth intercostal space at the left midaxillary line.


10. What is the standard paper speed for ECG recording?
A. 10 mm/sec
B. 25 mm/sec
C. 50 mm/sec
D. 100 mm/sec

Correct Answer: B
Rationale: Standard ECG paper speed is 25 mm/sec.


11. What is the standard calibration for ECG?
A. 1 mV = 5 mm
B. 1 mV = 10 mm

, C. 1 mV = 15 mm
D. 1 mV = 20 mm

Correct Answer: B
Rationale: Standard calibration is 1 mV = 10 mm (two large boxes).


12. Which artifact is caused by patient movement?
A. Wandering baseline
B. Somatic tremor
C. 60-cycle interference
D. Interrupted baseline

Correct Answer: B
Rationale: Somatic tremor is caused by muscle movement and appears as jagged, irregular
baseline.


13. Which artifact is caused by electrical interference from nearby equipment?
A. Wandering baseline
B. Somatic tremor
C. 60-cycle interference
D. Interrupted baseline

Correct Answer: C
Rationale: 60-cycle interference appears as a thick, fuzzy baseline due to electrical noise.


14. Which artifact is caused by poor electrode contact?
A. Wandering baseline
B. Somatic tremor
C. 60-cycle interference
D. Interrupted baseline

Correct Answer: A
Rationale: Wandering baseline is often caused by poor electrode adhesion or patient
movement.


15. What is the refractory period?