CCBMA Diagnostic Procedures and ECG 1 — Questions and Answers
Question 1: In a standard 12-lead ECG, how many chest (precordial) leads are included?
- 4
- 6 (Correct answer)
- 8
- 12
Correct answer: 6
A 12-lead ECG includes 6 chest leads (V1–V6) and 6 limb leads (I, II, III, aVR, aVL, aVF).
Question 2: What does the P wave on an ECG represent?
- Ventricular depolarization
- Atrial depolarization (Correct answer)
- Ventricular repolarization
- AV node conduction delay
Correct answer: Atrial depolarization
The P wave represents atrial depolarization, which triggers the contraction of the atria.
Question 3: Which ECG lead placement error is most likely to produce artifact?
- Placing electrodes over bony prominences (Correct answer)
- Cleaning skin with alcohol before electrode placement
- Instructing the patient to lie still
- Using fresh electrodes
Correct answer: Placing electrodes over bony prominences
Placing electrodes over bony prominences creates poor contact and increased artifact due to reduced conductivity.
Question 4: Which preparation step is most important before placing ECG electrodes?
- Applying lotion to the skin
- Clipping excessive hair and cleaning with alcohol (Correct answer)
- Asking the patient to exercise briefly
- Placing electrodes over clothing
Correct answer: Clipping excessive hair and cleaning with alcohol
Cleaning the skin with alcohol and clipping hair removes oils and reduces impedance for better signal quality.
Question 5: Where is the V1 electrode placed in a standard 12-lead ECG?
- 5th intercostal space, midclavicular line
- 4th intercostal space, right sternal border (Correct answer)
- 4th intercostal space, left sternal border
- 5th intercostal space, anterior axillary line
Correct answer: 4th intercostal space, right sternal border
V1 is placed at the 4th intercostal space along the right sternal border.
Question 6: A somatic tremor artifact on an ECG is most likely caused by:
- Electrical interference from equipment
- Patient muscle movement or shivering (Correct answer)
- Incorrect lead placement
- Worn or dried electrode gel
Correct answer: Patient muscle movement or shivering
Somatic tremor artifact results from voluntary or involuntary patient muscle movement and appears as irregular baseline wander.
CCBMA Diagnostic Procedures and ECG 1
In a standard 12-lead ECG, how many chest (precordial) leads are included?