Dimensionless Index of the Mitral Valve for Evaluation of Degenerative Mitral Stenosis

Abstract

Purpose: Degenerative mitral stenosis (DMS) is an increasingly recognized cause of mitral stenosis. The goal of this study was to compare echocardiographic differences between DMS and rheumatic mitral stenosis (RMS), identify echocardiographic variables reflective of DMS severity, and propose a dimensionless mitral stenosis index (DMSI) for assessment of DMS severity. Methods: This is a single-center, retrospective cohort study. We included patients with at least mild MS and a mean transmitral pressure gradient (TMPG) [?] 4 mmHg. Mitral valve area by the continuity equation (MVACEQ) was used as an independent reference. The DMSI was calculated as follows: DMSI = VTILVOT / VTIMV. All-cause mortality data were collected retrospectively. Results: A total of 64 patients with DMS and 24 patients with RMS were identified. MVACEQ was larger in patients with DMS (1.43 ? 0.4 cm2) than RMS (0.9 ? 0.3 cm2) by~0.5 cm2 (p = <0.001) and mean TMPG was lower in the DMS group (6.0? 2 vs. 7.9?3 mmHg, p=0.003). A DMSI of ? 0.50 and [?] 0.351 were associated with MVACEQ [?] 1.5 and MVACEQ [?] 1.0 cm2 (p<0.001), respectively. With the progression of DMS from severe to very severe, there was a significant drop in DMSI. There was a non-significant trend towards worse survival in patients with MVACEQ [?] 1.0 cm2 and DMSI [?] 0.35, suggesting severe stenosis severity. Conclusion: Our results show that TMPG correlates poorly with MVA in patients with DMS. Proposed DMSI may serve as a simple echocardiographic indicator of hemodynamically significant DMS.

Degenerative Mitral Stenosis—Diagnostic Challenges and Future Directions

“…A nonsignificant trend toward increased risk mortality was observed with MVACEQ ≤1.0 cm 2 and DMSI ≤0.35 with 50% mortality in the DMS cohort at 1 year (Fig. 1B) [25]. However, this tool cannot be used in patients with significant left sided regurgitation as VTI across aortic or mitral valve would be higher and this may over or overestimate stenosis severity.…”

“…Such validation studies are lacking for DMS patients. There is a poor correlation seen between mean gradients and MVA using the continuity equation in DMS [25]. This lack of correlation can be attributed to different issues with trans-mitral flow, increased heart date (i.e., shortened diastole), and decreased left atrial and LV compliance in patients with diastolic dysfunction [17].…”

“…To overcome these issues, a dimensionless mitral stenosis index (DMSI) = (LVOT-VTI/MV-VTI) has been proposed (Fig. 1A, [25]). A DMSI of 0.35 to 0.50 is consistent with severe DMS (MVA ≤1.5 cm 2 ), and a DMSI <0.35 suggests very severe calcific MS (MVA ≤1.0 cm 2 ).…”

My Approach to the Echocardiographic Assessment of Mitral Annular Calcification: Challenges and Particularities

“…On the other hand, Doppler estimation using pressure halftime may overestimate the valve area (underestimating stenosis severity) due to decreased LV compliance and increased LV diastolic pressure, which are common in older patients. 9,16,19 Planimetry by two-and three-dimensional echocardiography may be inaccurate due to acoustic shadow formation. 9 The dimensionless index of the mitral valve can be useful for grading stenosis.…”

“…Values lower than 0.35 are correlated with very severe stenosis (mitral valve area < 1 cm²), while those 0.35-0.50 suggest severe stenosis (<1.5 cm²) (Figure 4). 9,19 The mitral transvalvular gradient should also be cautiously interpreted. In rheumatic mitral stenosis, the relationship between the mean gradient (MG) and the mitral valve area (MVA) is predictable, i.e., when the MG is > 10 mmHg, the MVA is < 1.0 cm².…”