Subvalvular apparatus and adverse outcome of balloon valvotomy in rheumatic mitral stenosis

Balloon mitral valvotomy (BMV) is a well-established therapeutic modality for rheumatic mitral stenosis (RMS). However, there are chances of procedural failure and the more ominous post-procedural severe mitral regurgitation. There are only a few prospective studies, which have evaluated the pathogenic mechanisms for these major complications of BMV, especially in relation to the subvalvular apparatus (SVA) pathology.

All symptomatic patients of RMS suitable for BMV by echocardiographic criteria in a span of 1 year were selected. In addition to the standard echocardiographic assessment of RMS (Wilkins score and score by Padial et al.), a separate grading and scoring system was assigned to evaluate the severity of the SVA pathology. The SVA score was 'I', when none of the two SVAs had severe disease, 'II' when one of the two SVAs has severe disease, and 'III' when both SVAs had severe disease. With these scoring systems, the outcomes of BMV (successful procedure, failure, and post-procedural mitral regurgitation) were analyzed. Emergency valve replacement was performed depending on clinical situation, and in cases of replacement, the pathology of the excised mitral valves were compared with echocardiographic findings.

Of the 356 BMVs performed in a year, 43 patients had adverse outcomes in the form of failed procedure (14 patients) and mitral regurgitation (29 patients). Forty-one among these had a SVA score of III. The sensitivity and specificity of the MR score was lesser than the SVA score (sensitivity 0.34 vs. 1.00, specificity 0.92 vs. 0.99, respectively). The mitral valvular morphology in 39 patients who underwent post-procedural valve replacements correlated well with echocardiography findings.

It is important to assess the degree of SVA pathology in the conventional echocardiographic assessment for RMS, as BMV would have adverse events when both SVAs were severely diseased.