Einthoven's triangle

Concept in electrocardiography

Einthoven's triangle is a theoretical construct used in electrocardiography (ECG) to represent the spatial orientation of the three standard limb leads (I, II, and III) used in recording the electrical activity of the heart. This concept is named after Willem Einthoven, a Dutch physiologist who was awarded the Nobel Prize in Physiology or Medicine in 1924 for his discovery of the mechanism of the electrocardiogram.

Description

Einthoven's triangle is an imaginary equilateral triangle that is formed by the two shoulders and the pubis, with the heart at the center. The vertices of the triangle correspond to the placement of the electrodes for the limb leads:

• Lead I is the voltage difference between the left arm (LA) and right arm (RA).
• Lead II is the voltage difference between the left leg (LL) and right arm (RA).
• Lead III is the voltage difference between the left leg (LL) and left arm (LA).

Diagram of limb leads in EKG

The triangle is used to understand the direction of the electrical activity of the heart as it is recorded by these leads. The leads are arranged in such a way that they form a coordinate system, allowing for the determination of the heart's electrical axis.

Function

Einthoven's triangle is fundamental in the interpretation of the ECG. By analyzing the electrical activity recorded by the three limb leads, clinicians can infer the direction and magnitude of the heart's electrical vector. This is crucial for diagnosing various cardiac conditions, such as arrhythmias, myocardial infarction, and conduction abnormalities.

The concept of Einthoven's triangle also facilitates the understanding of the Einthoven's law, which states that the sum of the voltages in leads I and III equals the voltage in lead II (I + III = II). This relationship is useful for verifying the accuracy of ECG recordings.

Clinical Application

In clinical practice, Einthoven's triangle helps in the placement of electrodes for a standard 12-lead ECG. Although modern ECGs use additional leads, the principles derived from Einthoven's triangle remain foundational. The triangle aids in the visualization of the heart's electrical activity in the frontal plane, providing insights into the heart's rhythm and conduction pathways.

Historical Context

Willem Einthoven developed the concept of the triangle in the early 20th century, revolutionizing the field of cardiology. His work laid the groundwork for modern electrocardiography, allowing for non-invasive monitoring of the heart's electrical activity. Einthoven's triangle remains a key teaching tool in medical education, illustrating the basic principles of ECG interpretation.

Related pages

• Electrocardiography
• Willem Einthoven
• Cardiac electrophysiology
• Heart conduction system