The Influence of Arterial Pressure on Mitral Incompetence in Man *

Abstract

A double dye dilution method was used to measure mitral regurgitant flow. Serial measurements were made of forward and regurgitant flow and left atrial and ventricular pressures during changes in arterial pressure induced by vasopressor and depressor drugs. Patients could be separated according to the changes found in the calculated area of the mitral regurgitant orifice. In some this remained constant, the regurgitant flow changing in proportion with the ventriculo-atrial pressure gradient; these patients often had coincident mitral stenosis, and at subsequent surgery the valve orifice was fixed by fibrosis or calcification. In others the regurgitant orifice varied considerably, disproportionate changes in regurgitant flow accompanying changes in arterial pressure; when this occurred, changes in myocardial contractility also influenced the regurgitant orifice; in these patients mitral stenosis was absent, and annular dilatation was invariably found at subsequent surgery, with or without disease of the valve leaflets. From these results, differences in the natural history of patients with mitral incompetence can be predicted. The information gained is also potentially useful in the differential diagnosis of different types of mitral incompetence.