Physiologic Studies in Mitral Valvular Disease

Physiologic findings obtained by cardiac catheterization on 29 patients with mitral valvular disease are discussed. Cardiac outputs, intracardiac pulmonary arterial and pulmonary pressures are determined during rest and exercise. It is shown that the resting cardiac output is reduced in all patients with mitral disease and that exercise results either in a fall or a small increase in the minute volume of circulation. The pulmonary artery and capillary pressures are elevated with rest and rise further with exercise. A clear differentiation by physiologic means between mitral stenosis and mitral insufficiency is difficult. However, in patients with mitral insufficiency the resting cardiac output is lower, the arterial venous oxygen difference is higher and exercise causes a greater fall in the cardiac output. A comparison is made between the physiologic manifestations of mitral disease and myocardial failure: the residual volume of blood of the right ventricle is usually increased in patients with mitral disease and failure and in myocardial failure alone. However, the right ventricular residual volume is normal in mitral disease without evidence of myocardial failure. The pulmonary vascular resistance in mitral disease is usually elevated. It is demonstrated that in a number of patients the pulmonary vascular resistance is not fixed since it decreases during exercise or following valvulotomy of the mitral valve.