Differences in Characteristics, Left Atrial Reverse Remodeling, and Functional Outcomes after Mitral Valve Replacement in Patients with Low-Gradient Very Severe Mitral Stenosis

Abstract

Background: The discrepancy between planimetered mitral valve area (MVA) and mean diastolic pressure gradient (MDPG) has not been studied extensively in patients with mitral stenosis. The purpose of the present study was to investigate differences in characteristics and outcomes after mitral valve replacement (MVR) between low- and high-MDPG groups in patients with very severe mitral stenosis (VSMS). The hypothesis was that the low-MDPG group would have different characteristics and would be associated with poor clinical outcomes after MVR.

Methods: In total, 140 patients who underwent isolated MVR because of pure VSMS (planimetered MVA ≤ 1.0 cm(2)) were retrospectively reviewed, and follow-up echocardiography was performed for ≥12 months after MVR. Patients were divided into two groups according to preoperative MDPG (low gradient [LG], <10 mm Hg; high gradient [HG], ≥10 mm Hg). Strain and strain rate analysis was performed using speckle-tracking echocardiography of the left ventricle before MVR in a subgroup of 56 patients.

Results: There were 82 patients (59%) in the LG group and 58 patients (41%) in the HG group. The LG group was older and demonstrated a higher prevalence of female gender, diabetes mellitus, and atrial fibrillation (P < .05 for all). When comparing the LG and HG groups, the left atrial volume index was larger (105.1 ± 51.9 vs 87.8 ± 42.9 mL/m(2), P < .001), and strain rate during isovolumic relaxation of the left ventricle was lower (0.17 ± 0.08 vs 0.29 ± 0.09 sec(-1), P < .001) in the LG group. After MVR, the percentage left atrial volume index reduction after MVR was significantly smaller in the LG group (-29.9 ± 15.1% vs -43.5 ± 16.4%, P < .001). Persistent symptoms after MVR were more common in the LG group compared with the HG group (P = .004), even though preoperative functional class was similar between the groups.

Conclusions: Compared with those with HG VSMS, patients with LG VSMS were older, more often female, and more frequently had diabetes mellitus and atrial fibrillation. They also had greater impairment of isovolumic relaxation, less favorable left atrial reverse remodeling, and a greater risk for persistent symptoms after MVR. These data might suggest other concurrent mechanisms for left atrial enlargement and symptom development in LG VSMS, such as atrial fibrillation and diastolic dysfunction, as well as valvular stenosis.

Keywords: Left atrium; Mitral stenosis; Mitral valve replacement.