Mitral stenosis and mitral regurgitation

Overview

The mitral valve has two leaflets (anterior and posterior), attached by chordae tendineae to papillary muscles, and sits in a fibrous annulus. Disease of any part can make it narrow (stenosis) or leaky (regurgitation).

In Pakistan, rheumatic heart disease remains a major cause of both lesions, often in young women. Mitral stenosis can decompensate dramatically in pregnancy or with the onset of atrial fibrillation.

Mitral stenosis (MS)

Aetiology

• Rheumatic heart disease (by far the commonest), years after rheumatic fever. More common in women.
• Congenital mitral stenosis.
• Lutembacher syndrome: mitral stenosis plus an atrial septal defect.
• Mitral annular calcification in the elderly and in end-stage renal disease.
• Rare: carcinoid disease, SLE, rheumatoid arthritis.
• Left atrial myxoma can mimic MS.

Pathology: rheumatic inflammation causes fusion of the commissures, thickening and later calcification of cusps and shortened chordae; the valve takes a "fish-mouth" or domed shape.

Pathophysiology

• Normal valve area is 4–6 cm². Symptoms usually start below about 2 cm²; severe MS is below 1 cm².
• Blood flow from left atrium to left ventricle is obstructed, so left atrial pressure rises → left atrial enlargement → pulmonary venous congestion → pulmonary hypertension → right ventricular hypertrophy and failure → functional tricuspid regurgitation.
• Left ventricular function is usually normal.
• Anything that shortens diastole (tachycardia, AF, pregnancy, exercise, fever) raises left atrial pressure sharply and causes pulmonary oedema.

Clinical symptoms

• Exertional breathlessness, orthopnoea, PND; acute pulmonary oedema with AF or pregnancy.
• Haemoptysis: pink frothy sputum, bronchial vein rupture, or pulmonary infarction.
• Palpitations from AF.
• Systemic emboli (stroke is commonest) from left atrial thrombus.
• Fatigue, cough, recurrent chest infections; rusty sputum from haemosiderin-laden macrophages.
• Right heart failure: ankle swelling, ascites, liver congestion.
• Pressure from a huge left atrium: hoarseness (left recurrent laryngeal nerve, Ortner syndrome) and dysphagia.

Physical signs

Auscultatory diagnosis

• Loud S1: the mobile but narrowed valve shuts sharply. It becomes soft when the valve is calcified and rigid.
• Opening snap: high-pitched sound just after S2 as the stiff valve snaps open.
• Mid-diastolic murmur: low-pitched rumble, best heard with the bell at the apex, patient turned on the left side, in expiration, after exercise.
• Presystolic accentuation: late-diastolic increase from atrial contraction; disappears in AF.
• Graham Steell murmur: early diastolic murmur of pulmonary regurgitation from severe pulmonary hypertension.

Signs of severe MS:

• Short gap between S2 and the opening snap (high left atrial pressure opens the valve early).
• Long mid-diastolic murmur.
• Signs of pulmonary hypertension (loud P2, RV heave) and right heart failure.

ECG

• P mitrale: broad, bifid (notched) P wave in lead II; large negative terminal P component in V1 (left atrial enlargement), in sinus rhythm.
• Atrial fibrillation is common.
• Later: right axis deviation and right ventricular hypertrophy (tall R in V1).

Radiological findings (chest X-ray)

• Left atrial enlargement:
  • Straightening of the left heart border (prominent left atrial appendage).
  • Double shadow to the right of the heart.
  • Splayed carina (left main bronchus lifted).
  • Posterior bulge on lateral film; may indent a barium-filled oesophagus.
• Normal-sized left ventricle.
• Pulmonary venous congestion: upper lobe diversion, Kerley B lines, oedema.
• Enlarged pulmonary arteries (pulmonary hypertension).
• Calcified mitral valve on a lateral view; rarely, haemosiderosis nodules.

Echocardiography

• Thickened, restricted leaflets with commissural fusion; "hockey-stick" anterior leaflet; enlarged left atrium.
• Severity:

• Doppler estimates pulmonary artery pressure from the tricuspid jet.
• TOE detects left atrial (appendage) thrombus, essential before balloon valvotomy.
• The Wilkins score (mobility, thickening, calcification, subvalvular disease) predicts the success of balloon valvotomy.

Management and treatment

Medical:

• Diuretics for congestion.
• Rate control for AF or sinus tachycardia: beta-blockers (or rate-limiting calcium channel blockers, digoxin). Slowing the heart lengthens diastole and lowers left atrial pressure.
• Anticoagulation with warfarin in AF, previous embolism or left atrial thrombus. (DOACs are not recommended in moderate-to-severe rheumatic MS.)
• Secondary prophylaxis against rheumatic fever in young patients (see the rheumatic fever chapter).
• Pregnancy: breathlessness and tachycardia in a woman with MS is treated with a beta-blocker (e.g. metoprolol) and a diuretic if needed; balloon valvotomy can be performed in pregnancy if severe.

Intervention is offered to patients with severe MS and symptoms or pulmonary hypertension.

Complications of MS: AF, systemic embolism (stroke), pulmonary hypertension, right heart failure, pulmonary oedema, haemoptysis, infective endocarditis (less common than in MR), chest infections.

Mitral regurgitation (MR)

Aetiology

Acute severe MR: papillary muscle or chordal rupture (MI, endocarditis, trauma), leaflet perforation.

Pathophysiology

• In chronic MR, part of each stroke goes back into the left atrium. The left atrium dilates and absorbs the volume, so its pressure rises only slowly. The left ventricle enlarges to keep forward output up (volume overload). Symptoms may appear only after years.
• In acute MR, the normal-sized left atrium cannot stretch: left atrial pressure shoots up (large v wave), causing sudden pulmonary oedema and cardiogenic shock. The heart may be normal in size.

Symptoms

• Exertional breathlessness, orthopnoea, fatigue (low forward output), palpitations (AF).
• Late: right heart failure, cachexia.
• Endocarditis is more common and embolism less common than in MS.
• The onset of AF has a smaller effect on symptoms than in MS.

Physical signs

Auscultatory, ECG and radiological findings

• Auscultation: soft S1, apical pansystolic murmur to the axilla, S3. Severity is suggested by an S3, a displaced apex and signs of LV dysfunction.
• ECG: P mitrale (left atrial enlargement), LVH in about half, AF.
• Chest X-ray: left atrial and left ventricular enlargement (raised cardiothoracic ratio), pulmonary venous congestion; valve or annular calcification. In acute MR, pulmonary oedema with a normal-sized heart.
• Echo: dilated left atrium and ventricle, mechanism (prolapse, flail leaflet, ruptured chord or papillary muscle), severity by colour Doppler (vena contracta, regurgitant volume), LV size and EF. TOE helps plan repair.

Treatment

Medical:

• Mild to moderate MR: regular echo follow-up.
• Diuretics, ACE inhibitors (especially in functional MR with LV dysfunction), heart failure drugs.
• Rate control and anticoagulation for AF.
• Good dental hygiene; endocarditis prophylaxis is not routine.

Surgery (repair is preferred over replacement where possible):

• Symptomatic severe MR (with LVEF above 30%).
• Asymptomatic severe MR with LV dysfunction: LV end-systolic diameter above 45 mm and/or EF below 60%.
• Consider in asymptomatic severe MR with new AF or pulmonary hypertension.
• Acute severe MR (papillary muscle or chordal rupture, endocarditis): emergency surgery, with an intra-aortic balloon pump as a bridge.
• Percutaneous edge-to-edge repair (MitraClip) for selected patients who are too high-risk for surgery.

Mitral valve prolapse

• Floppy, myxomatous leaflets bulge into the left atrium in systole (Barlow syndrome).
• More common in young women; associated with Marfan and Ehlers–Danlos syndromes.
• Often harmless; may cause atypical chest pain, palpitations.
• Mid-systolic click with a late systolic murmur.
• Can progress to severe MR, chordal rupture or endocarditis.

Mitral stenosis and regurgitation compared

Quick revision

• MS: rheumatic; area <1 cm² severe; malar flush, AF, tapping apex, loud S1, OS, mid-diastolic rumble.
• Severity: S2–OS gap short, murmur long, pulmonary hypertension.
• ECG: P mitrale/AF, later RAD and RVH. X-ray: LA enlargement (straight border, double shadow, splayed carina).
• MS treatment: diuretic, beta-blocker, warfarin for AF; balloon valvotomy if pliable, no LA clot, ≤mild MR; replace if calcified, MR or persistent clot.
• MR: prolapse, ischaemia, rheumatic, endocarditis, dilated LV.
• MR signs: displaced forceful apex, soft S1, pansystolic murmur to axilla, S3.
• Acute MR = sudden pulmonary oedema (papillary muscle rupture); emergency surgery.
• Operate in severe MR with symptoms, or EF <60% or end-systolic diameter >45 mm.

Written by The House Job from standard references (Kumar and Clark's Clinical Medicine).

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