Introduction

An ECG (electrocardiogram) is a test that records the electrical activity of your heart, including the rate and rhythm. It is used to diagnose cardiac conditions, monitor heart function.

ECG is a graphic record of the electrical impulse that generated by depolarization and repolarization of myocardium.

Lead Placement

A 12-lead ECG provides multiple electrical views of the heart along a vertical and horizontal.

• Bipolar Limb leads (I, II, III)

• Unipolar augmented leads (aVR,aVL,aVF)

• Chest leads (V1-V6)

Normal Sinus Rhythm

Electrical activity of the cardiac cycle is characterized by five primary wave deflections, designated by letters P,Q,R,S,T.

ECG Components

• P Wave: Atrial depolarization

• QRS Complex: Ventricular depolarization(80-100ms)

• T Wave: Ventricular repolarization(160ms)

• PR Interval: Atrioventricular delay(120-200ms)

• QT Interval: Ventricular repolarization (420ms)

Einthoven's Triangle

Einthoven's Triangle is a concept in electrocardiography (ECG) used to represent the spatial relationship of the three standard limb electrodes (Lead I, Lead II, and Lead III) and their electrical activity in the heart.

How it Works:

Einthoven's Triangle is essentially a geometrical triangle formed by placing three electrodes on the body: one on the right arm, one on the left arm, and one on the left leg. These electrodes are used to measure the electrical activity of the heart and form the basis for the standard 12-lead ECG.

The three points of the triangle represent the following:

• Right Arm (RA): This is the reference electrode.

• Left Arm (LA): This electrode is used for Lead I and contributes to Leads II and III.

• Left Leg (LL): This electrode is used for Lead II and Lead III, and it helps determine the direction of the heart's electrical activity along the vertical axis.

Electrical Representation:

The three leads, Lead I, Lead II, and Lead III, correspond to the following vectors:

1. Lead I measures the potential difference between the right and left arms (RA - LA).

2. Lead II measures the potential difference between the right arm and the left leg (RA - LL).

3. Lead III measures the potential difference between the left arm and the left leg (LA - LL).

Purpose:

Einthoven's Triangle helps visualize the direction of electrical impulses as they travel through the heart. The heart's electrical activity can be traced along the axes of the triangle, and it provides information about the heart's rhythm, structure, and function.

Key Points:

• The triangle is an equilateral triangle, meaning the three leads are spaced equally around the heart's electrical axis.

• Einthoven's Law states that the sum of the potentials of Lead I, Lead II, and Lead III is always zero.

This law helps ensure the consistency of the electrical measurements.