Einthoven triangle

The Einthoven triangle is an example of a recorded voltage u (the electrocardiogram signal) modeled as the dot product of the lead vector of a bipolar PU electrode pair and the bound heart dipole vector m (see Section 10.1). 

Figure 10.3 Myocard of left (thick) and right (thin) ventricles, the Einthoven triangle in the frontal plane. QRS heart vector m, normal angle values are between —30° and +90°.

Figure 10.6 Locus of the heart vector m given each 10 ms in the QRS diastole. Derived from the Einthoven triangle (Figure 10.5). The graph is in the frontal plane and the x-axis has the direction of the lead vector H (a = 0).

The Einthoven triangle gained more and more acceptance, but was also heavily criticized. 

Lack of three-dimensional (3D) data The Einthoven triangle is flat as if all electrical activities in the heart occur in a thin vertical sheet. An additional back electrode would, for instance, represent a first primitive approach to a lead perpendicular to the classical Einthoven triangle. 

Einthoven s electrode placement has been adopted and standardized into the ECG Lead system known as the Einthoven triangle and is shown in Fig. 17.38. Electric potential differences are measured between the three limb electrodes along the line between the electrode placements, and their potentials are called lead I, n, and III such that... 

Einthoven (1913) proposed an equilateral triangle model with the center in the heart center. Figure 10.5. Each side of the triangle corresponded to each of the three bipolar leads I, II, and III. He proposed the heart modeled as a bound dipole vector (he did not use that expression), and that a lead voltage was the projection of the heart vector on a corresponding triangle side (actually a dot product). He proposed that his model could... 

Figure 10.5 Einthoven s triangle. The triangle is in the frontal plane of the patient, m is the heart vector bound to the center of the heart u is the instantaneous scalar voltage measured in a respective lead a is the instantaneous angle of the electric axis of the heart.

A Dutch physician named Willem Einifaoven in 1902 pnqx>sed a measurement convention where the ECG electrodes were placed on the limbs. At this position, the monitored electric activity waveshape is more reproducible from one individual to the next because they are in a relative far field to the heart where electric gradients are lower. Einthoven used electrodes placed on the right and left aims and left leg and made the assumption that the heart was at the electric center of a triangle defined by the electrodes. 

The axes of the three bipolar limb leads (I, II, and III) form a shape known as Einthoven s triangle. Because the electrodes for these leads are about equidistant from the heart, the triangle is equilateral. 

The three limb leads I, II and III combine to form the bipolar leads. By bipolar we mean that the lead has both a positive and negative pole. Willem Einthoven established this standardised lead system, which was named after him, called Einthoven s Triangle (Fig. 2.4). Different electrode positions were also tested but produced little or no measurable results in comparison. 

---