Acute Mitral Regurgitation in Man

Four patients are presented who developed acute mitral regurgitation 5 days, 2, 3, and 18 months, respectively, before cardiac catheterization. The hemodynamic findings in the three early cases resemble those found in the presence of a constricting pericardium: left and right ventricular, as well as left and right atrial pressures, equilibrated during diastole. As expected, giant left atrial v waves accompanied markedly elevated pulmonary arterial pressures and low cardiac indices. Biplane angiocardiography showed only slight left atrial and moderate left ventricular enlargement, but showed a large regurgitant fraction and dilated pulmonary veins. Orthopnea was transient or absent in two of the three early cases. The pericardium may play a role in the early phase of acute mitral regurgitation in mimicking signs of right heart failure and preventing pulmonary edema. Development of increased pulmonary venous capacitance may be another major early mechanism of compensation since the pericardium may be preventing left atrial enlargement. Later in the course, after 6 months, the pericardium does not appear to be a factor in the hemodynamics, as noted in our patient and in patients reported by others.