Surface reflections of cardiac excitation and the assessment of infarct volume in dogs. A comparison of methods.

Ventricular depolarization was analyzed in intact dogs by simultaneously recording body surface potential maps, McFee axial vectorcardiograms, and a 5 X 4 lead precordial grid of QRS complexes. The purpose of this study was to compare the effectiveness of subtraction approaches, using the simultaneously acquired data. The totally closed chest approach avoided the problem of volume conductor alteration by thoracotomy. Infarct volume was calculated morphologically from measurements of serial ventricular sections. The maximal correlation with anatomic infarct size using the precordial QRS grid approach was 0.51, using cumulative difference data between 1 and 38 msec when the postinfarction grid was substracted from the preinfarction grid. A correlation coefficient of 0.80 was achieved using the numerically integrated data between 1 and 31 msec from the vectorcardiogram, and the body surface potential map achieved a correlation coefficient above 0.88 when the electrical difference of msec 16 was used. These data suggest that estimates of infarct size from selected surface reflections of the activation process are feasible if some sort of preinfarction control data are available. Caution must be exercised to avoid inclusion of electrical effects late in the activation process which contain contamination by highly variable alterations in the excitation sequence due to delayed conduction or alteration in conduction pathway in or near the infarct zone.