A (Epicardial pacing). Anterior surface of the torso tank, seen from the inside. The "epicardial envelope" (H) shows a negative minimum (- sign) facing the epicardial pacing site, on the postero-inferior surface of the left ventricle, and two positive potential maxima (marked with a + sign). Two selected groups of current lines are shown. The lines start from the two maxima, follow curved pathways in the torso volume and reach the minimum, which overlies the epicardial pacing site. The rectangular frame shows the orientation and position of a plane passing through the three extrema (see text). Most of the selected currents flow near that plane.
B (Endocardial pacing): Anterior torso surface, seen from the inside. Compared to A, the image has been rotated by approximately 40Á from left to right around the vertical axis of the torso, to better visualize the current lines. Here too, the epicardial envelope H shows two potential maxima (+ signs) and a minimum (- sign). The location of the maxima is different from A, because here they are approximately aligned with the direction of the endocardial fibers. The location of the minimum, however, is the same as in A and overlies the site of insertion of the pacing needle. Here again, the rectangular frame shows the orientation and position of a plane passing through the three potential extrema.
From: Taccardi, B., Punske, B.B., MacLeod, R.S., and Ni Q., Extracardiac effects of myocardial electrical anisotropy, Journal of Biomedizinishe Technik, Vol. 46(2):216-218,2001.
Data rendered by BioPSE.