Effects of acute changes in left ventricular size on surface potential in man

Effects of cardiac size on surface potential magnitude were investigated by induction of acute changes in ventricular dimensions by rapid atrial pacing in 17 cases with ischemic heart disease (IHD) and in 15 cases without IHD. Left ventricular end-diastolic dimensions (LVDd), estimated by echocardiography, decreased along with certain changes in surface potential magnitude during atrial pacing in each case. A positive correlation between LVDd and the amplitudes of RV5, RX, and the maximum spatial QRS magnitude was observed in most of the cases and might be explained by changes in distance between the heart and the chest electrode and/or the Brody effect. However, an inverse correlation was observed in 4 of 17 cases with IHD, and could not be explained by these factors. Other factors, such as changes in the ventricular activation sequence, should be considered as the mechanism.