ELECTROCARDIOGRAPHIC FEATURES IN EXPERIMENTAL SUBENDOCARDIAL INFARCTIONS IN CANINE HEARTS

Chemical necrosis was produced with the infiltration of 96-degrees alc ohol on the middle anterosuperior segment 5 (nomenclature of the Inter national Society for Computerized Electrocardiology) of the free left ventricular (LV) wall in 45 dogs and on the apical segment 10 and midd le posterolateral segment 11 in 30 others. In five animals from each g roup, a 10 bipolar arrow assembly was used to obtain Purkinje fiber po tentials and to determine the degree to which QS complexes are recorde d from the inner portions of the free LV wall. When transmural necrosi s was present, QS complexes were generally obtained in both the epicar dial and thoracic leads. Subendocardial necrosis was manifested by qrS complexes on the epicardium, as well as in the peripheral leads. When the posterolateral middle third of the LV wall was damaged, Rs or qRs complexes were recorded in leads II, III, and aVF, and an increase in the voltage of the R wave in leads V1 and V2 was observed. intramural myocardial necrosis diminished the voltage of the R wave in the corre sponding leads. Left peripheral blocks obscured the manifestation of m yocardial necrosis.