Experimental complete right heart bypass. Proposal of a new model and acute hemodynamic assessment with vasoactive drugs in dogs.

A new model of complete right heart bypass was devised in dogs. All systemic venous blood was directly led to the bilateral pulmonary arteries by end-to-side superior vena cava-right pulmonary anastomosis, diverting the inferior vena caval blood to the superior vena cava with a graft, ligating the inferior vena cava at its end and the pulmonary artery at its trunk, and shunting the coronary venous return from the right-ventricle to the left atrium. Nine consecutive dogs tolerated the procedures, and acute hemodynamic characteristics and responses to vasoactive drugs were observed for 5 hours throughout the following full studies. Cardiac output ranged from 66 to 102 ml/min/kg at a central venous pressure of 15 to 26 mm Hg. Norepinephrine, isoproterenol, and phentolamine were administered with the central venous pressure maintained constant at 18 mm Hg. Isoproterenol and phentolamine increased cardiac output while reducing pulmonary and/or systemic vascular resistance, with a possible concomitant inotropic effect in the former. Norepinephrine was detrimental, causing an increase in both pulmonary and systemic vascular resistance.