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CHAPTER SUMMARY AND CENTRAL ILLUSTRATION
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Chapter Summary
This chapter discusses the etiology, pathogenesis, clinical presentation, diagnostic modalities, and therapeutic options of mitral stenosis (MS). Rheumatic MS remains prevalent in developing countries whereas prevalence of degenerative MS has increased in developed countries. The hemodynamic hallmark of MS is a persistent diastolic gradient between the left atrium and left ventricle. Exertional dyspnea develops after a long asymptomatic latent period. The course is subsequently complicated by heart failure, atrial fibrillation, thromboembolism, and hemoptysis. Echocardiography is the mainstay of diagnosis, although cardiac catheterization may be needed to establish the severity in doubtful cases. While medical therapy can relieve the symptoms of MS, relief of the mechanical obstruction is needed to correct the underlying hemodynamic abnormality. This is achieved by balloon mitral valvotomy or mitral valve replacement in those with favorable or unfavorable anatomy, respectively. In patients with degenerative MS, newer therapies in the form of percutaneous transcatheter mitral replacement are being evaluated. A concerted global effort to control rheumatic heart disease is needed to reduce the prevalence of rheumatic MS.
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ETIOLOGY AND EPIDEMIOLOGY
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Worldwide, the majority of cases of mitral stenosis (MS) are caused by rheumatic heart disease (RHD) (Fig. 32–1).1,2 In developed nations, rheumatic fever has become quite rare and so too has MS (0.02% in Sweden).3 Possible reasons include antibiotic use, improved socioeconomic conditions as well as mutation of the group “A” streptococcus (GAS) to a less rheumatogenic agent. On the other hand, degenerative MS (due to mitral annular calcification) is increasing in developed nations (12.5% in the Euro Heart Survey).2,4
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RHD remains prevalent in developing countries Using echocardiographic screening, the prevalence of RHD ranged from 20 to 30 per 1000 school children.5,6 There are an estimated 39 million cases of RHD worldwide,7 mostly in low- and middle-income countries. Approximately half of the patients with RHD have MS (either isolated or combined with other valve pathologies)8,9 but only 60% of these patients report a past history of rheumatic fever (RF).10–12
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Rheumatic MS is a progressive disease with an initial stable course in the early years followed by an accelerated deterioration. The time interval between RF and the clinical appearance of MS varies considerably. In developed countries, the disease has a slow progression with a latency period of 20 to 40 years before symptoms appear.10–13 Thus, presentation in the West is in the fifth to sixth decades of life.14 In developing ...