Pulmonary venous stenosis has been demon- strated before and after surgery, but it is not usually progressive over time and has not been associated with PAH. 3. Although risks of isolated cor triatriatum sinister surgery is low, it should be performed when there is evidence of a substantial gradient. In 1 series, the mean gradient at the time of surgical repair was at least 8 mm Hg.S4.2.1-3 It is conceivable that on occasion, clinical circumstances (ie, symp- toms, arrhythmia) would warrant intervention in patients with lower gradients. 4.2.2. Congenital Mitral Stenosis Recommendation for Congenital Mitral Stenosis Referenced studies that support the recommendation are summarized in Online Data Supplement 32. COR LOE Recommendation I B-NR Adults with congenital mitral stenosis or a parachute mitral valve should be evaluated for other left-sided obstructive Synopsis Congenital mitral valve disease may be anatomically complex and is often accompanied by other lesions. Indications for intervention in mitral stenosis are de- scribed in the 2014 VHD guidelineS4.2.2-3 and apply to those patients with congenital mitral stenosis. Balloon mitral valvuloplasty is rarely, if ever, indicated or effec- tive in congenital mitral stenosis. See Section 3.3 for recommendations on who should perform surgeries, cardiac catheterization, and other procedures in these patients; Section 3.4 for rec- ommendations on diagnostic evaluation; and Table 17 for routine testing and follow-up intervals. Recommendation-Specific Supportive Text 1. Parachute mitral valve is most commonly found in the presence of other congenital abnormali- ties such as the components of Shone complex. Recurrence and progression of the various asso- ciated lesions are expected, subsequent surger- ies are common, and mortality may be associated with other defects.S4.2.2-2 Therefore, these patients require follow-up at a center where such abnor- malities can be followed and future interventions considered. 