Electrocardiogram Tutorial – What is the Einthoven’s Triangle?

Since the start of the 20th century, the electrocardiogram (EKG) has been one of the most indispensable tools used by clinicians in diagnosing various heart conditions. We owe its existence to Dutch scientist Willem Einthoven who invented the first practical electrocardiograph in 1903 and introduced the use of leads. As a tribute, the electrodes of the three limb leads were named after him.

Based on these three limb leads’ positions relative to one another the Einthoven triangle is formed, which is basically an imaginary triangle surrounding the heart.  Following this EKG tutorial, it will be easier to understand that this triangle provides the reference area for mapping out the heart’s anatomy through specific locations of its electrical activity. Hence, one must also be familiar with the concept of the EKG, electrodes and the cardiac process of depolarization and repolarization. Below is an illustrated diagram of this triangle.

EKG Tutorial

In the past, Einthoven’s leads (leads I, II, and III) were the only leads used for obtaining an ECG tracing. These leads intersect at angles of 60 degrees (equal to the angles of an equilateral triangle: 180/3 = 60 degrees). It is easier to understand the concept of lead placement when the leads are drawn and represented as intersecting lines with a mutual center point. (Click the play button on the figure on top to view the animation). Shifting of the leads as seen in the animation is used for an easier understanding of the concept of lead placement and has no functional effect on the registration of electrical activity on the EKG tracing.

EKG Tracing

This EKG Tutorial provides you with a bird’s eye view of the Einthoven’s triangle, explaining why the electrodes are situated in specific areas of the body during the procedure. For more extensive EKG learning, please sign up for our online medical training at Medical-ELearning.com.