$$\text{Lead II} = \text{Lead I} + \text{Lead III}$$

Question 1

Which of the following best describes Einthoven's triangle as shown in the second image?

Accepted Answer

A geometric representation of the three bipolar limb leads (I, II, III) formed by electrodes placed on the right arm, left arm, and left leg.

Question 2

According to Einthoven’s law, which equation correctly relates the voltages of the three bipolar limb leads?

Accepted Answer

$$	ext{Lead II} = 	ext{Lead I} + 	ext{Lead III}$$

Question 3

In the first image, which lead configuration would most likely produce a negative QRS complex, and why?

Accepted Answer

aVR, because the electrical impulse travels away from the right arm electrode.

Question 4

What is the primary purpose of the limb leads (I, II, III) as depicted in the images?

Accepted Answer

To provide different frontal plane views of the heart's electrical activity.

Question 5

If the QRS complex in Lead I is positive, what does this indicate about the direction of the heart's electrical impulse?

Accepted Answer

The impulse is traveling toward the left arm electrode, which is the positive pole in Lead I.

Question 6

Which of the following statements about the augmented leads (aVR, aVL, aVF) is correct based on the first image?

Accepted Answer

They are unipolar leads that use a single positive electrode and a reference point created from the other electrodes.

Question 7

If the electrical impulse travels at a right angle to the positive electrode, what type of QRS complex is expected?

Accepted Answer

Isoelectric, with equal positive and negative deflections.

Question 8

Which electrode placement is used as a ground to minimize electric shock risk and stabilize EKG readings?

Accepted Answer

Right leg electrode

Question 9

Why is Lead II commonly used for rhythm monitoring in hospitals?

Accepted Answer

It provides clear views of both atrial (P wave) and ventricular (QRS complex) activity.

Question 10

Based on the images, which lead would most likely show the tallest QRS complex, and why?

Accepted Answer

Lead II, because the electrical axis of the heart most closely aligns with the direction of Lead II.

Question 11

If the left arm electrode is disconnected, which leads would be directly affected?

Accepted Answer

Leads I, II, III, aVL

Question 12

Which of the following is NOT a function of the bipolar limb leads as shown in the images?

Accepted Answer

Recording electrical activity from the chest wall

Question 13

What is the main difference between a lead and an electrode as illustrated in the images?

Accepted Answer

An electrode is a physical sensor placed on the body, while a lead is a specific view or recording created from those sensors.

Question 14

Which lead configuration in the first image would be most useful for detecting left ventricular hypertrophy?

Accepted Answer

Lead I and aVL, as they view the left side of the heart.

Question 15

If the QRS complex is isoelectric in Lead III, what does this suggest about the direction of the heart's electrical impulse?

Accepted Answer

The impulse is traveling perpendicular to Lead III.

Question 16

Which of the following best explains why the QRS complex in aVR is typically negative?

Accepted Answer

The heart's electrical impulse travels away from the right arm electrode, which is the positive pole in aVR.

Comprehensive Study Notes: Cardiac Anatomy, Physiology, and Electrocardiography (Chapters 1–6)

Study Guide - Practice Questions