[mitral Stenosis].

8. What is the pathophysiology of mitral stenosis? Increased left atrial pressure is necessary to push blood through a stenotic mitral valve from the left atrium into the left ventricle. Increased left atrial pressure is transmitted retrograde into the pulmonary veins and pulmonary capillaries and ultimately into the pulmonary arteries. It gives the patient a sensation of dyspnea. A left atrial pressure of approximately 25 mm Hg increases pulmonary capillary pressure enough to produce pulmonary edema. Example: to maintain adequate left ventricular filling across a 1.5-cm valve, a pressure gradient of 20 mm Hg is required. With a normal left ventricular end-diastolic pressure of 5 mm Hg, a 20-mm Hg gradient produces a left atrial pressure of 25 mm Hg. Left atrial pressure rises even further as flow across the valve increases (increased CO). This high left atrial pressure backs up and floods the lungs (pulmonary edema).