THE EFFECT OF THE HEART'S POSITION ON THE ELECTROCARDIOGRAPHIC APPEARANCE OF VENTRICULAR EXTRASYSTOLES 1

Abstract

Studies were made in anesthetized dogs of the effect of changing the heart''s position on the electrocardiogram of extrasystoles induced from fixed points. The electrical axis of the various extrasystoles did not move the same amount nor always in the same direction when the heart was shifted. Many times the direction of the major initial deflection of the extrasystoles was reversed in one or more leads. The results are attributed to the unequal movements of the so-called 3-dimensional vectors of the various extrasystoles when the heart was shifted. The reversal in direction of the QRS group of ventricular extrasystoles shows (a) that the configuration and position of the heart cannot be ignored in analyzing the site of ventricular extrasystoles and bundle-branch block in man, and (b) that the direction of the QRS group of extrasystoles induced in the 2 patients reported may not be applied to the non-diseased human heart without consideration of all factors. On the basis of these results it would be unjustified to attempt to localize the site of ventricular extrasystoles or of bundle-branch block from the direction of the major initial complex in the electrocardiograms.