Internal Diseases and Therapy · MU Sofia

13. Diseases of the mitral valve: mitral stenosis

Covers mitral stenosis: how rheumatic and degenerative narrowing of the valve obstructs left ventricular filling, and how this drives atrial fibrillation, pulmonary hypertension and right heart failure. It then sets out the severity grading table, the classic auscultation findings, the ECG and echocardiographic features, a differential-diagnosis table, and medical, balloon and surgical treatment with intervention criteria.

Inside: 10 sections · 2 labelled pictures · 2 tables · 14 flashcards · 14 min

Topic 13 of 139 in the MU Sofia syllabus for Internal Diseases and Therapy (Medicine, Years 4 and 5). The free AceMed note covers it in 10 sections, about 1,995 words (14 min of reading), with 14 flashcards.

In this note

  1. Definition
  2. Etiology
  3. Pathophysiology and haemodynamics
  4. Classification
  5. Clinical features
  6. Diagnosis
  7. Differential diagnosis
  8. Treatment
  9. Complications
  10. Prognosis

Definition

Mitral stenosis (MS) is a narrowing of the mitral valve orifice that obstructs the flow of blood from the left atrium (LA) into the left ventricle (LV): an obstruction to LV filling in diastole.

  • The mitral valve has an anterior and a posterior leaflet, attached by chordae tendineae to two papillary muscles (anterolateral and posteromedial); together with the annulus they form the mitral apparatus.
  • The normal mitral valve area (MVA) is 4–6 cm². A mild reduction (down to about 2 cm²) causes little or no gradient at rest; the obstruction becomes clinically significant at ≤ 1.5 cm² (see Classification), not at 2 cm².

Etiology

  • Rheumatic heart disease is by far the most common cause worldwide. Only about half of the patients remember an episode of acute rheumatic fever; about two thirds are women. Symptoms appear after a latent period of 10–20 years or more: in the 4th–5th decade in Europe, but in teenagers and young adults where rheumatic fever is endemic (Africa, South Asia).
  • Degenerative (calcific) MS: heavy mitral annular calcification spreading into the base of the leaflets in elderly patients, often with hypertension, chronic kidney disease (dialysis), diabetes or aortic stenosis. It is increasing in Europe. There is no commissural fusion.
  • Rare causes: congenital MS (parachute mitral valve; with an atrial septal defect = Lutembacher syndrome), systemic lupus erythematosus, rheumatoid arthritis, drugs (ergot derivatives, cabergoline, pergolide, fenfluramine, benfluorex), mediastinal radiotherapy, carcinoid disease, mucopolysaccharidoses, Fabry disease.
  • Functional obstruction of LA outflow without a stenotic valve: left atrial myxoma, large vegetation, ball thrombus, cor triatriatum, stenosis of a prosthetic mitral valve.

Pathology of rheumatic MS

  • Repeated inflammation and healing → fusion of the commissures (the key lesion), thickened and later calcified leaflets, and fused, shortened chordae.
  • The result is a funnel-shaped valve with a narrow, slit-like "fish-mouth" (buttonhole) orifice. The mitral valve is affected in almost all patients with rheumatic heart disease, often together with mitral regurgitation and aortic valve disease.

Rheumatic mitral stenosis seen from the opened left atrium: thickened leaflets fused at the commissures leave only a narrow "fish-mouth" slit.

Image: “Mitral stenosis, gross pathology 20G0015 lores” by unknown author, Public domain, via Wikimedia Commons.

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