Vectorcardiography

Vectorcardiography (VCG) is a method of recording the magnitude and direction of the electrical forces that are generated by the heart by means of a continuous series of vectors that form curving lines around a central point.

Vectorcardiography was developed by E. Frank in the mid 1950s. Since the human body is a three-dimensional structure, the basic idea is to construct three orthogonal leads containing all the electric information. The three leads are represented by right-left axis (X), head-to-feet axis (Y) and front-back (anteroposterior) axis (Z).

To calculate Frank's leads X, Y and Z using the standard leads system, the following expressions are used:

X = -(-0.172 V1 - 0.074 V2 + 0.122 V3 + 0.231 V4 + 0.239 V5 + 0.194 V6 + 0.156 DI - 0.010 DII) (1)

Y = (0.057 V1 - 0.019 V2 - 0.106 V3 - 0.022 V4 + 0.041 V5 + 0.048 V6 - 0.227 DI + 0.887 DII) (2)

Z = -(-0.229 V1 - 0.310 V2 - 0.246 V3 - 0.063 V4 + 0.055 V5 + 0.108 V6 + 0.022 DI + 0.102 DII) (3)

There are different criteria how at to evaluate a vectorcardiogram created by various researchers. Grygoriy Risman presents these different methods, which were developed over half a century and offers an advanced approach called spatial vectorcardiometry (SVCM). The original Russian thesis is filed in the Odessa Medical Academy. Recently, Bipolar Precordial Leads exploring the right to left axis combined with averaged unipolar precordial leads allowed to produce sectorial VCG loops in the horizontal plane.