Electrocardiographic features in experimental subendocardial infarctions in canine hearts.

Chemical necrosis was produced with the infiltration of 96 degrees alcohol on the middle anterosuperior segment 5 (nomenclature of the International Society for Computerized Electrocardiology) of the free left ventricular (LV) wall in 45 dogs and on the apical segment 10 and middle posterolateral segment 11 in 30 others. In five animals from each group, a 10 bipolar arrow assembly was used to obtain Purkinje fiber potentials and to determine the degree to which QS complexes are recorded from the inner portions of the free LV wall. When transmural necrosis was present, QS complexes were generally obtained in both the epicardial 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 corresponding leads. Left peripheral blocks obscured the manifestation of myocardial necrosis.