Experimental Production of an Extracardiac Shunt Around the Mitral Valve

IN CERTAIN cases of heart disease of rheumatic origin there is stenosis of the mitral valve which is accompanied with only mild involvement of the myocardium. In such instances the disturbed circulatory physiology is traceable almost wholly to obstruction at the valve. Circulatory embarrassments are principally of two kinds. First, there is insufficient filling of the left ventricle during diastole, resulting in a failure of the heart to supply adequate amounts of blood to the periphery, particularly under conditions of increased exercise which raise the demands for an augmented flow to the locomotor system. Second, the damming up of blood behind the stenotic valve causes engorgement of the pulmonary bed which can lead to pulmonary edema, respiratory distress, hemoptysis, limitation of physical activity and even fatality. Such pulmonary congestion is particularly aggravated during periods of exercise when the right ventricle increases its output but the flow of blood is impeded