[Electrical changes in experimental diastolic and mixed overloads of the right ventricle]

The paper describes the electrical changes in 115 mongrel dogs with exposed heart and open pericardium, during the gradual development of diastolic and combined (diastolic and systolic) overloading of the right ventricle. Ventricular overload was produced by means of a constant venous infusion of saline solution: up to 12 liters in 3 hours and half. In all cases, right intraventricular conduction disturbances, of either proximal or distal type, appeared. Right blocks were classified on the base of the topography of the ventricular activation delay. They were correlated with the hemodynamic adaptation. The results of this study allow us to formulate the following main points: 1) Disturbances of the right intraventricular conduction during experimental diastolic and combined overloading of the ipsilateral ventricle, seem to be due to a distention of the ventricular specialized fibers; 2) proximal right blocks are related to a global dilatation of the ventricular chamber, secondary either to a quick overloading or to a decrease in the myocardial capacity for adaptation; 3) distal right blocks are caused more frequently by a distention of the anterolateral portions of the free right ventricular wall, where the right middle subdivision is located.