Low-Gradient Severe Mitral Stenosis: Hemodynamic Profiles, Clinical Characteristics, and Outcomes

Background-Optimal management of patients with severe mitral stenosis (MS) and low transmitral gradient is incompletely understood. Methods and Results-We examined 101 consecutive patients with severe rheumatic MS (mitral valve area <= 1.5 cm(2)) who underwent balloon valvuloplasty. Low gradient was defined as mean transmitral gradient <10 mm Hg and low flow as stroke volume index <= 35 mL/m(2) by echocardiography. Symptoms and mortality data were collected. Systolic, diastolic, and arterial function were characterized by measuring left ventricular (LV) end-systolic elastance, LV stiffness constant (beta), diastolic capacitance (predicted LV end-diastolic volume at a common LV filling pressure of 30 mm Hg), and effective arterial elastance. Low gradient (<10 mm Hg) was present in 55 patients, including low flow/low gradient in 11 and normal flow/low gradient in 44 patients, and high gradient was present in 46 patients. Participants with low-flow/low-gradient (LG) MS were older with higher rates of atrial fibrillation (64%) and subvalvular thickening, higher afterload, and decreased LV compliance with lower ejection fraction (57 +/- 10% versus 65 +/- 4% versus 63 +/- 6%, P=0.002) but similar end-systolic elastance compared with patients with normal-flow/LG and high-gradient MS. The normal-flow/LG group had larger mitral valve area and lower left atrial pressure by catheterization, as well as favorable long-term outcomes compared with the low-flow/LG and high-gradient MS group. A total of 40% of patients with LG MS had no symptomatic benefit from valvuloplasty compared with 18% of patients with high-gradient MS (P=0.02). Conclusions-Presence of low gradient in patients with severe MS was associated with lesser symptomatic benefit from valvuloplasty. In the subset with low stroke volume index, this may be related to independent ventricular-vascular uncoupling, decreased LV compliance, and high prevalence of atrial fibrillation in addition to intrinsic MS.