CCBMA Diagnostic Procedures and ECG

Question 1

In a standard 12-lead ECG, how many chest (precordial) leads are included?

Accepted Answer

6

Answer

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?

Accepted Answer

Atrial depolarization

Answer

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?

Accepted Answer

Placing electrodes over bony prominences

Answer

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?

Accepted Answer

Clipping excessive hair and cleaning with alcohol

Answer

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?

Accepted Answer

4th intercostal space, right sternal border

Answer

V1 is placed at the 4th intercostal space along the right sternal border.

CCBMA - California Certifying Board for Medical Assistants Practice Test