Severity of Rheumatic Mitral Stenosis: A Comparative Study of Mitral Leaflet Separation Index versus Mitral Valve Area.

Abstract

Introduction: Assessing the severity of mitral stenosis (MS) is crucial for predictive and therapeutic purposes. While methods like planimetry and pressure half-time (PHT) are considered the gold standard for measuring mitral valve area (MVA), they can be operator-dependent or influenced by hemodynamic factors. Our study evaluates the accuracy of mitral leaflet separation index (MLSI) as an alternative tool for assessing rheumatic MS severity, considering its independence from hemodynamic variations. The limitations of conventional methods are discussed to underscore the need for alternative approaches.

Methods: This retrospective study was conducted at a single-center adult echocardiography laboratory. We included 148 patients with rheumatic MS who underwent transthoracic echocardiography between January 2016 and December 2020. MLSI was compared to traditional methods for determining MVA by measuring the distance between the tips of mitral valve leaflets in two-dimensional echocardiographic views which was then averaged to obtain the MLS index.

Results: Of the 148 patients (mean age 51.4 years ± 14.2 years, 76.4% female), atrial fibrillation (AF) was present in 20.3%. Among these patients, 70 reported symptoms ranging from shortness of breath on exertion class II to III. There are moderate positive correlations between averaged MVA and MLSI by PLX (r = 0.640, p < 0.001) and MLSI by apical four-chamber (r = 0.608, p < 0.001). The mean MLSI was 10.2 ± 2.3 mm, with a range of 7.8-13.3 mm. Subgroup analyses revealed stronger correlations between MLSI and MVA in patients without AF or mitral regurgitation (MR). AUROC analysis identified an MLSI threshold of <0.81 cm for severe MS, yielding an AUC of 0.84. Reproducibility analysis demonstrated excellent agreement for MLSI (ICC = 0.92, 95% CI: 0.87-0.96). Subgroup analyses also showed that the correlation between MLSI and mean gradient was stronger in patients without MR (r = -0.58) compared to those with moderate-to-severe MR (r = -0.41). Subgroup analyses showed weaker correlations in patients with significant MR or AF.

Conclusion: Our findings suggest that MLSI correlates moderately positively with MVA measured by planimetry and PHT. Thus, MLSI can serve as an additional method for assessing the severity of rheumatic MS in adult patients. This index is useful in cases of discordance between MS severities estimated by existing methods, in the presence of AF, and alongside MR.