Abstract
The author reported previously the electrocardiographic and vectorcardiographic classification of clinical isolated complete RBBB. Under-standing of patterns of ventricular excitation in clinical RBBB has been progressed by studies on experimental RBBB. The present paper concerns the electrocardiographic and vectorcardiographic findings when incisions of. the main stem and subdivisions of the right bundle branch Were produced in canine hearts. ECGS and VCGs, obtained, in a dog with spontaneous complete RBBB and in five dogs with surgically produced complete RBBB, were studied Materials and Methods. All experiments were performed on 20 mongrel adult dogs weighing 5.3 to 19.3 kilograms. Each dog was anesthetized with intravenous pentobarbital sodium (Initially 20 to 25 mg. per kilogram). A control 12-lead ECG and Frank VCG were obtained. Under artificial positive-pressure respiration, the heart was exposed through a right or left thoracotomy and supported in approximately normal position by a sling made from the pericardium. When appropriate, right bundle branch block was produced blindly with a Lucae's myringotomy knife introduced into the right ventricular cavity through the anterior free wall of the ventricle. ECGs and VCGs were recorded after closing the chest on each occasion. The ECGS Were obtained with the use of the Fukuda Electro Co. Model RS-100DH2 at a paper speed of 25mm/sec. The thoracic lead position employed in this study are those of Lannek. CV5RL is located on the fifth right intercostal space at the sternal border, corresponding roughly to lead V1 in man. VCGs in the frontal (F), left sagittal (LS) and horizontal (H) planes were recorded in the supine position. The fifth intercostal space was used for placement of the chest electrodes. The VCGs were obtained with the use of the Fukuda Electro Co. Model VA-1A.
