COR LOE Recommendations In patients with signs or symptoms of rheumatic MS, TTE is indicated to establish the diagnosis, quantify hemodynamic severity, assess concomitant valvular lesions, and demonstrate valve morphology (to determine suitability for mitral commissurotomy).1 3 In patients considered for percutaneous mitral balloon commissurotomy (PMBC), TEE should be performed to assess the presence or absence of LA thrombus and to evaluate the severity of MR.4 6 Synopsis For patients with rheumatic MS, TTE is the initial di- agnostic test to determine the severity of the stenosis Table 16. Stages of MS Stage Definition Valve Anatomy Valve Hemodynamics Hemodynamic Consequences Symptoms A At risk of MS Mild valve doming during diastole Normal transmitral flow velocity None None B Progressive MS Rheumatic valve changes with commissural fusion and diastolic doming of the mitral valve leaflets Planimetered mitral valve area Increased transmitral flow velocities Mitral valve area >1.5 cm2 Diastolic pressure half-time Mild to moderate LA enlargement Normal pulmonary pressure at rest None C Asymptomatic severe MS Rheumatic valve changes with commissural fusion and diastolic doming of the mitral valve leaflets Planimetered mitral valve area Mitral valve area 1.5 cm2 Diastolic pressure half-time Severe LA enlargement Elevated PASP >50 mm Hg None D Symptomatic severe MS Rheumatic valve changes with commissural fusion and diastolic doming of the mitral valve leaflets Planimetered mitral valve area Mitral valve area 1.5 cm2 Diastolic pressure half-time Severe LA enlargement Elevated PASP >50 mm Hg Decreased exercise tolerance Exertional dyspnea The transmitral mean pressure gradient should be obtained to further determine the hemodynamic effect of the MS and is usually >5 mm Hg to 10 mm Hg in severe MS; however, because of the variability of the mean pressure gradient with heart rate and forward flow, it has not been included in the criteria for severity. 