NATURE OF ‘UNIPOLAR’ EXTREMITY LEADS IN THE DOG. LEAD VR

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Abstract
The nature of the unipolar extremity leads VR, VL and VF in the dog was detd. by employing 5 techniques of investigation [long dash] impressed potentials, forced epicardial extrasystoles, surface application of KCL and/or cautery, ligation of coronary vessels, and heating and cooling the epicardium. In each of these leads, downward movement of the electrocardiographic beam occurred following depolarization of specific regions of the heart designated as the proximal zone of the lead, while upward movement of the beam occurred when depolarization occurred in specific regions of the heart designated as the distal zone. The position of the beam at any given moment in the ventricular complex is detd. by the algebraic summation of electrical effects caused by depolarization in the proximal and distal zones. It was therefore possible to chart in a rough way the spread of excitation and recovery by . analyzing the position of the beam at successive moments in each of the three leads. It was also possible to localize the site of origin of extrasystoles and of injury currents. The proximal and distal zones for each unipolar extremity lead were delimited and seemed to bear a definite spatial relationship to the position of the exploring electrode. The ''zonal interference'' theory of the genesis of the ventricular complex proposed by Nahum and Hoff received full confirmation in these expts.