A LEAD SYSTEM RECORDING TOTAL OUTWARD CARDIAC DIPOLE STRENGTH

Abstract

The McFee-Johnston lead field concept is an important advance toward electrocardiographic leads giving uniform and calculable dipole representation throughout the heart but the X and Z leads suggested by Johnston''s group do not take full advantage of the concept. The equipotential fields of these leads are non-uniform in horizontal plane models, while in the frontal and sagittal planes, field uniformity does not extend to the torso surface. The fields also suffer from distortion by the Brody slope effect, as a result of "wrapping" multiple electrodes. A new lead system, also based on the McFee-Johnston concept, is proposed. It includes a platform-mounted multiple electrode, which automatically corrects for the slope effect. In 2-D field plots the X and Z fields are uniform in 3 planes, the leads being thus insensitive to dipole location and distribution, regardless of torso shape and heart size. Since the fields are uniform and calculable, not only in the heart but throughout the torso to the torso surface, a calculable quantitative relationship exists between cardiac and surface forces. A method of determining the heart''s total outward directed dipole moment is therefore described. A closed irregular dipole surface (Green surface) at the boundary of the high conductivity area formed by intracardiac blood, is suggested as an alternative to the widely used but inaccurate single equivalent cardiac dipole. The limitations of 2-D models, especially in the frontal and sagittal planes, are stressed. The 6 electrodes of the 3 proposed leads consist of a total of 72 balsa-lithium units. As no paste is required, the 3 leads take no longer to record, than 3 standard leads using paste.