Effects of subendocardial injury on the electrocardiogram of intact dogs

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Abstract
In intact anes-thetized dogs, localized, reversible, and easily reproducible injuries were produced at the apical subendocardium of both ventricles by using the endomyocardial bioptome of Konno and Sakakibara, inserted through the cervical vessels. These resulted in S-T elevation in the lead from the bioptome (endocardial lead) and S-T depression in the unipolar precordial lead with the electrode fluoroscopically placed opposite the tip of the bioptome, and usually in lead a VF. In one experiment S-T elevation was found in the precordial lead; in this case autopsy showed that the tip contacted the posterior wall. These findings point to the participation of the subendocardium in the genesis of the electrocardiogram and are in accord with the dipole concept of the electrocardiogram but contrary to the zonal interference theory. Several reasons are discussed why subendocardial injuries could produce a smaller S-T displacement in surface leads than comparable subepicardial injuries.