**1. Introduction**

Rheumatic fever (RF) develops as the consequence of autoimmune reaction to group A betahemolytic streptococcal pharyngeal infection [1]. Cardiac involvement is the most important manifestation of RF and mainly presents an acute endocarditis and valvulitis. The following inflammatory and hemodynamic changes involving the cardiac valves insulted by the acute RF could result in long-standing rheumatic heart disease (RHD). The natural course of RHD depends on the severity of the initial attack and the frequency of recurrences. Unlike in developed countries, RHD is not infrequently seen in many areas of the world. Indeed, some countries have reported persistently high or even increasing incidence of RF and subsequent RHD during the recent decades [2]. All cardiac valves could be involved in patients with RHD.

© 2017 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

The mitral valve is almost always affected in clinically manifested patients, followed by the aortic and tricuspid valves. Mitral stenosis (MS) is the cardinal valvular lesion in RHD and is particularly amenable to transcatheter therapy when it is isolated or dominant and the anatomy is favorable. When left untreated, severe MS deteriorates the functional status of the patients and worsens their long-term outcomes [3]. Rarely, other etiologies might cause MS (i.e., connective tissue disorders, drugs, and congenital abnormalities). Today, degenerative calcified MS, failure of the bioprosthetic mitral valve, and overcorrection of mitral regurgitation (MR) are increasingly seen. Unlike rheumatic MS, these non-rheumatic mitral valve obstructions are not associated with commissural fusion and are not generally relieved by percutaneous balloon mitral valvuloplasty (BMV). When applied in correctly selected subjects and performed by experienced operators, a successful BMV procedure can improve symptoms and long-term survival of the patients and is, therefore, the method of choice in the treatment of patients with severe rheumatic MS [4, 5].
