Experimental Observations on the Atypical Q-R-S Waves of the Electrocardiogram of the Dog

In the last few years considerable interest has been shown in the atypical Q-R-S waves of the electrocardiogram. These abnormal electrocardiograms have usually been seen in patients who gave clinical evidence of a failing myocardium. Many have died from cardiac failure within a few months following the time these abnormal electrocardiograms were discovered. In those cases that came to necropsy there has usually been found an extensive fibrosis of the heart which often involved the endocardial and subendocardial layers. Until recently it was generally believed that these atypical Q-R-S waves were due to a lesion of one or the other of the main branches of the auriculoventricular bundle. This conception was based primarily on the experimental work of Eppinger and Rothberger.1They produced experimental lesions of the right and left branch of the auriculoventricular bundle. Those hearts with a lesion of the right branch gave an electrocardiogram in which the