An experimental study of the electrocardiographic effects of localized myocardial lesions

Abstract Localized lesions were produced in twentythree dogs by the injection of 40 per cent formalin into the myocardium through the intact chest wall. Simultaneous electrocardiographic leads from an orthogonal lead system designed for this animal were recorded before and after production of the lesions. The hearts were sectioned at 3 mm. intervals to demonstrate location of the lesions. The effects of localized tissue loss in each of these areas were qualitatively predicted on the basis of the ventricular excitation sequence in the dog. These predicted effects were compared with the actual effects of the lesions. Twenty lesions resulted in QRS alterations similar to those predicted on the basis of tissue loss. These included some lesions restricted to the subendocardial half of the myocardium, and some of these were manifest by abnormal Q waves in the electrocardiogram. Alterations of the QRS complex which followed those attributed to tissue loss occurred with eleven lesions and were considered to be probable results of conduction disorders. There was a definite correlation of conduction disorders and involvement of the interventricular septum by the lesions.