Some patients have symptoms from rheumatic MS even with a mitral valve area >1.5 cm2 and a resting mean transmitral gradient <10 mmHg. This may be related to the variability and reliability of measuring a mitral valve area by either planim- etering a short-axis image of the mitral valve or using a diastolic half-time for indirect calculation of the mitral valve area. There are also patients who have a relatively low gradient at rest who generate a much higher gradient with exercise, with symptoms developing from the higher LA pressure. Thus, in these patients in whom there is a discrepancy between the clinical symptoms and the resting hemodynamics, exercise testing with measurement of the mean transmitral gradient or the direct pulmonary artery wedge, or both, is Patients who increase their gradients to >15 mmHg with exercise have been shown to improve symptomatically after PMBC.16 6. Both anatomic valve morphology and the pres- ence of commissural calcification predict suc- cessful PMBC. However, in all such series, this predictive ability is not absolute, with 42% of patients with an anatomic valve Wilkins morphol- ogy score >822,23,31,32 having an optimal outcome (25% increase in mitral valve area to >1.5 cm2 ) and 38% of patients with commissural calcium having event-free survival at 1.8 years.18,19,22,23 Accordingly, severely symptomatic patients who are poor surgi- cal candidates may benefit from PMBC even with suboptimal valve anatomy.17 Patients who refuse surgery may also be offered PMBC after discussion about the potential complications associated with this procedure when it is performed in patients with suboptimal valve anatomy. 6.3. 