Degenerative Mitral Stenosis-Diagnostic Challenges and Future Directions

Determining the severity of stenosis in degenerative mitral stenosis (DMS) is fraught with challenges. Neither a high trans-mitral gradient nor a small valve area calculation is sufficiently diagnostic for DMS due to variable left atrial and left ventricular compliance in the setting of diastolic dysfunction, and the variable flow seen in patients with chronic kidney disease (i.e., high flow state) and elderly women (low flow state). Three-dimensional measurement of mitral valve area may be underestimated due to shadowing from basal calcium, and mitral valve annulus (MVA) by continuity equation (CEQ) or dimensionless mitral valve index can be erroneous in the presence of significant regurgitation of left-sided valves. The proposed dimensionless mitral stenosis index (DMSI) can be an easy echocardiographic tool to use in daily practice but needs further validation and is limited in the setting of significant regurgitation of left sided valves. Mean trans-mitral gradients $>$ 8 mmHg and pulmonary artery pressure $>$ 50 mmHg are independent predictors of mortality in those with MVA $<$ 1.5 ${\mathrm{cm}}^2$ derived by CEQ. In patients who have symptoms that are out of proportion to the degree of stenosis reported, exercise stress testing may help determine the physiologic effects of the stenotic valve. A combination of MVA by CEQ or DMSI and mean transmitral gradient at a given left ventricle stroke volume (flow) should be evaluated in larger studies.