How- ever, mean pressure gradient is highly dependent on transvalvular flow rate, the diastolic filling period, and heart rate. Mitral pressure half-time also has limitations, and is dependent upon LV and LA compliance as well as stenosis severity. Other approaches to calculation of the mitral valve area, such as the continuity equation or Gorlin formula, may be used if discrepancies exist. These pertain primarily to patients with rheumatic MS. 6.2. Rheumatic MS 6.2.1. Diagnosis and Follow-Up of Rheumatic MS 6.2.1.1. Diagnostic Testing: Initial Diagnosis Recommendations for Diagnostic Testing: Initial Diagnosis of Rheumatic MS Referenced studies that support the recommendations are summarized in Online Data Supplement 19. 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. 