Mitral valve resistance as a hemodynamic indicator in mitral stenosis.

Variability of the valve area calculated by the Gorlin formula has been noted in bioprosthetic and aortic valves, but few data are available for native stenotic mitral valves. Valve resistance has been proposed as an alternative hemodynamic indicator; however, its value in mitral stenosis has not been assessed. Thirty-four patients had simultaneous recordings of left atrial and ventricular pressures, 26 after percutaneous balloon mitral dilatation (PBMD). Patients with shunt or mitral regurgitation were excluded. Mitral valve resistance correlated exponentially with Gorlin mitral area (y = 133*[area]-1.5; p less than 0.0001). Both Gorlin mitral area and mitral resistance improved after PBMD (0.89 +/- 0.07 cm2 to 2.22 +/- 0.15 cm2; p less than 0.001; and 166 +/- 20 to 40 +/- 8 dynes.s.cm-5; p less than 0.001). Gorlin area and mitral resistance correlated with New York Heart Association functional class. After infusion of isoproterenol in 17 patients, there was an increase in Gorlin area (baseline 1.77 +/- 0.22 cm2, change 0.23 +/- 0.10; p less than 0.03), whereas mitral resistance did not change (baseline 96 +/- 16 dynes.s.cm-5, change 2 +/- 5; p = not significant). Mitral resistance is valuable in the assessment of mitral stenosis. It varies less than Gorlin mitral area under changing hemodynamic conditions.