VECTORCARDIOGRAPH

Typical Number in Hospital: 1

Cost Bands: 5

References: 9

Electrical signals from the heart are normally presented as a graph of voltage against time. The voltages developed along the various axes of the heart are recorded using a set of lead configurations which are selected in turn. However, more information can be derived from a vectorcardiogram (VCG) which can deliver a three-dimensional picture of the orientation and magnitude of the cardiac electrical vector throughout the cardiac cycle. In practice a two-dimensional image is displayed for each of the orthogonal planes.

A system of electrode positions has been developed to collect the X,Y and Z components of the ECG and any two of these can be fed through amplifiers to the X and Y deflection plates of a cathode ray tube. The ECG cycle is therefore presented as a loop on the screen representing the path of the electrical vector. The three possible planes of the vectorcardiogram may be shown in sequence and be photographed or collected in a computer memory for slow rate output to an X-Y recorder. Normal and abnormal patterns of the VCG loop are well documented.