FORM OF QRS EXTRASYSTOLIC COMPLEXES DEPENDING ON THE LOCALIZATION OF ZONES OF ELECTRIC STIMULATION OF THE HEART VENTRICLES IN DOGS
The forms of extrasystolic QRS complexes from limb leads in anesthetized dogs (n = 10) were studied. The trachea was intubated and artificial ventilation was made. The chest was opened and into the myocardium of the ventricles parallel to their base were introduced multiple needle electrodes consisting of platinized macroelectrodes. Extrasystoles were reproduced by electrical stimulation of the subendocardial, intramural and subepicardial zones of the myocardium of the free walls of the ventricles. It is established that the limb leads allow clearly differentiating according to the QRS form of left ventricular and right ventricular extrasystoles. In dogs, as in humans, with left ventricular extrasystoles, the form of the QRS complex had morphology, characteristic of the right bundle-branch block, in the right ventricle – of the left bundle-branch block. The electrical axis of the heart as in right ventricular and left ventricular extrasystoles is shifted to the left in comparison with the norm. The tendency of an increase in the duration of extrasystolic complexes formed as a result of stimulation of the epicardium is compared with subendocardial and intramural stimulation. The morphology of the extrasystolic complexes in the limb leads does not allow to identify the localization of ectopic foci located at different depths of the free walls of the ventricles of the heart. Electrocardiograms in limb leads are of little informative value for determining the localization of ectopic foci in the ventricular myocardium.