Mitral Valve Disease — Symptoms, Causes & Treatment | MyMedicPlus

The mitral valve — named for its resemblance to a bishop's mitre — is a bicuspid (two-leaflet) valve separating the left atrium from the left ventricle, allowing blood to flow forward from the atria to the ventricle during diastole and preventing regurgitation (backward flow) during systolic ventricular contraction. It is a complex apparatus comprising two leaflets (anterior and posterior), an annulus, chordae tendineae (tendinous cords connecting leaflet edges to papillary muscles), and two papillary muscles (anterolateral and posteromedial). Mitral valve disease encompasses two principal haemodynamic disorders: mitral regurgitation (MR — incompetence or leakage of the valve causing backward blood flow into the left atrium during systole) and mitral stenosis (MS — narrowing of the valve orifice reducing forward blood flow from the left atrium to the left ventricle during diastole). MR is the most common form of valvular heart disease in high-income countries — affecting approximately 2% of the general population — with the mitral valve prolapse (MVP) syndrome accounting for the majority of cases. Rheumatic heart disease remains the dominant cause of MS and MR globally — the sequela of rheumatic fever (following group A streptococcal pharyngitis in childhood), predominantly affecting low- and middle-income countries. Together, rheumatic heart disease affects 40 million people worldwide and causes 300,000 deaths annually. The natural history of mitral valve disease is of progressive haemodynamic deterioration leading to atrial fibrillation, pulmonary hypertension, and heart failure — with decisive intervention at the right time substantially improving prognosis.

Mitral regurgitation (MR) is classified as primary (organic — intrinsic leaflet or chordal pathology) or secondary (functional — structurally normal valve distorted by left ventricular (LV) dilatation and remodelling). Primary MR causes: mitral valve prolapse (MVP — the most common cause in high-income countries, present in 2-3% of the general population — posterior leaflet billowing above the mitral annular plane due to myxomatous degeneration of the leaflet tissue and chordae; associated with connective tissue disorders including Marfan syndrome, Ehlers-Danlos syndrome); rheumatic heart disease (scarring of leaflets and subvalvular apparatus from recurrent rheumatic fever — causes leaflet retraction, fusion, and regurgitation or combined MR and MS); infective endocarditis (destruction of leaflet tissue, chordal rupture, or vegetation formation on the valve causing acute severe MR — a surgical emergency); chordal rupture (spontaneous rupture of chordae tendineae causing acute MR — often from degeneration in elderly males); mitral annular calcification (MAC — degenerative calcification of the annulus in elderly patients, particularly those with hypertension, diabetes, and CKD — rigid calcified annulus impairs leaflet coaptation); and congenital mitral valve abnormalities (cleft anterior leaflet, accessory commissure). Secondary (functional) MR: LV dilatation from dilated cardiomyopathy or post-MI LV remodelling displaces the papillary muscles laterally, tethering the leaflets and preventing coaptation despite structurally normal leaflets. Mitral stenosis (MS) causes: rheumatic heart disease (the vast majority of MS globally — 95% of clinically significant MS; leaflet thickening, commissural fusion, and subvalvular fibrosis progressively narrowing the mitral orifice from the normal 4-6cm² to severe below 1.5cm²); congenital MS (parachute mitral valve, cor triatriatum); mitral annular calcification; mucopolysaccharidoses; and carcinoid syndrome (right-sided usually).

Mitral regurgitation: the natural history of chronic MR has a prolonged compensated phase during which the left atrium dilates to accommodate the regurgitant volume at low pressure, and the left ventricle enlarges (eccentric hypertrophy) to maintain forward cardiac output — this phase may last years to decades with the patient asymptomatic despite severe MR. Symptoms emerge with LV dysfunction or atrial fibrillation: exertional dyspnoea (initially on moderate exertion, progressing to rest dyspnoea and orthopnoea — from raised left atrial and pulmonary venous pressure); palpitations (from AF, which develops in 30-40% of severe MR, precipitating haemodynamic deterioration); reduced exercise tolerance; and fatigue. Auscultation: a holosystolic (pansystolic) blowing murmur at the left cardiac apex (heard with the stethoscope diaphragm, typically grade 3-6/6), radiating to the left axilla — classic for MR; the murmur of MVP is characterised by a midsystolic click followed by a late systolic murmur. Acute severe MR (chordal rupture, endocarditis, papillary muscle rupture from MI): sudden-onset acute pulmonary oedema and haemodynamic collapse — a cardiac surgical emergency. Mitral stenosis: obstruction to LV filling causes a pressure gradient across the mitral valve; symptoms develop when the mitral valve area reduces below 2cm² (moderate MS): dyspnoea (from elevated left atrial pressure, pulmonary congestion — worsened by exercise, tachycardia, and pregnancy as faster heart rates reduce diastolic filling time and increase the transmitral gradient); orthopnoea and paroxysmal nocturnal dyspnoea; haemoptysis (from pulmonary vein hypertension); atrial fibrillation (from chronic left atrial pressure elevation and enlargement — present in 30-50% of symptomatic MS — precipitating acute pulmonary oedema and thromboembolic risk); systemic thromboembolism (stroke, peripheral arterial embolism from LA thrombus in AF); and Malar flush (bilateral, reddish-purple discolouration of the cheeks from low cardiac output and peripheral vasoconstriction). Auscultation: a low-pitched diastolic rumble at the apex (best heard in the left lateral decubitus position with the bell of the stethoscope); loud first heart sound (S1); an opening snap (high-pitched early diastolic sound — shorter A2-OS interval reflects more severe stenosis); and signs of pulmonary hypertension (loud P2, right ventricular heave, tricuspid regurgitation murmur).

Transthoracic echocardiography (TTE) with Doppler is the primary diagnostic and monitoring investigation for all valvular heart disease. For MR: TTE assesses mechanism and aetiology (leaflet prolapse, flail segment, restricted leaflets), severity of regurgitation (vena contracta width, effective regurgitant orifice area — EROA above 0.4cm² indicates severe MR in primary MR; above 0.2cm² in secondary MR), left atrial and left ventricular dimensions, and LV systolic function (LVEF and left ventricular end-systolic diameter — LVESD above 40mm or LVEF below 60% in primary MR indicates LV decompensation and is a surgical trigger). For MS: TTE quantifies mitral valve area (MVA — below 1.5cm² severe; 1.5-2.0cm² moderate) using planimetry and pressure half-time; measures the mean mitral transmitral gradient (above 10mmHg severe at rest); assesses valve morphology for suitability for commissurotomy (Wilkins score — calcification, mobility, thickening, subvalvular disease — score above 8/16 predicts poor commissurotomy result); and estimates pulmonary artery pressure. Transoesophageal echocardiography (TOE): superior image quality for assessing valve mechanism (chordal rupture, vegetations), mitral valve anatomy for repair planning, and excludes left atrial appendage (LAA) thrombus before commissurotomy or cardioversion in AF. Cardiac catheterisation: invasive haemodynamic assessment when echocardiography is inconclusive — measures transmitral gradient, pulmonary capillary wedge pressure, and cardiac output (Gorlin formula for MVA). Cardiac MRI: accurate quantification of regurgitant fraction when echocardiographic assessment is discordant or inadequate. ECG: may show AF, left atrial enlargement (P mitrale — bifid P wave in lead II), or right ventricular hypertrophy in advanced disease. Chest X-ray: cardiomegaly, left atrial enlargement (double density shadow), pulmonary venous congestion, Kerley B lines.

Medical management: for MR, vasodilators (ACE inhibitors, ARBs) reduce afterload and may decrease regurgitant fraction in symptomatic patients or those unsuitable for surgery; diuretics for symptomatic pulmonary congestion; rate control (beta-blockers, digoxin) and anticoagulation (warfarin — INR 2.5-3.5) for AF. For MS, diuretics reduce pulmonary congestion; beta-blockers or non-dihydropyridine calcium channel blockers (diltiazem, verapamil) slow heart rate and improve diastolic filling time, particularly during exercise and AF; anticoagulation with warfarin for all MS patients with AF (high thromboembolic risk — direct oral anticoagulants, DOACs, are not validated for rheumatic AF, only warfarin). Percutaneous mitral balloon commissurotomy (PMBC — Inoue technique): the preferred intervention for moderate-severe symptomatic rheumatic MS with a favourable valve morphology (Wilkins score below 8, no or mild MR, no LAA thrombus); a balloon catheter is advanced transseptally across the mitral valve and inflated to crack open the fused commissures — immediate haemodynamic improvement, MVA doubles; PMBC achieves 10-year event-free survival of 50-60% before requiring repeat intervention or surgery. Surgical intervention for MR: ACC/AHA guidelines recommend surgery for: (1) symptomatic severe primary MR with LVEF above 30%; (2) asymptomatic severe primary MR with LV decompensation (LVEF 30-60% or LVESD above 40mm); or (3) asymptomatic severe MR with new-onset AF or pulmonary artery systolic pressure above 50mmHg. Mitral valve repair (preferred over replacement when technically feasible) — resects the prolapsing segment, implants an annuloplasty ring, and repairs chordae; associated with lower operative mortality, preserved LV function, avoidance of anticoagulation, and superior long-term durability. Mitral valve replacement (MVR) — mechanical (requires lifelong anticoagulation with warfarin) or bioprosthetic (no anticoagulation required beyond 3 months but limited durability of 10-15 years; preferred for elderly, those with anticoagulation contraindications, and women wishing to avoid warfarin in pregnancy). Secondary MR: medical optimisation of HF (ACE inhibitors, beta-blockers, cardiac resynchronisation therapy — CRT when QRS above 150ms in LBBB); MitraClip (percutaneous edge-to-edge mitral valve repair — COAPT trial) for severe secondary MR in symptomatic HFrEF patients despite optimal medical therapy (reduces MR, heart failure hospitalisations by 47%, and mortality by 38% at 2 years). Mitral valve surgery for severe symptomatic MS with unfavourable anatomy unsuitable for PMBC: open surgical commissurotomy or MVR.

Atrial fibrillation (AF): the most common complication of both MR and MS — develops in 30-50% of patients with significant disease; caused by chronic left atrial pressure elevation and progressive left atrial enlargement; precipitates haemodynamic deterioration in MS (loss of atrial filling and tachycardia markedly worsens the transmitral gradient) and MR (reduces LV filling time); carries high thromboembolic risk — stroke is the most feared complication of AF in MS (annual stroke risk 7-15% without anticoagulation in rheumatic AF with MS). Heart failure: untreated severe MR causes progressive LV eccentric dilatation and systolic dysfunction (LVEF decline, reduced forward cardiac output); once LVEF falls below 30-35%, prognosis with surgery worsens substantially — surgery should ideally be performed before LV decompensation. Pulmonary hypertension: chronic left atrial hypertension in both MR and MS causes reactive pulmonary vasoconstriction and eventually fixed pulmonary vascular remodelling, raising pulmonary artery systolic pressure (above 50-60mmHg indicates advanced disease); right ventricular failure develops from chronic pulmonary pressure overload, causing peripheral oedema, ascites, and low forward cardiac output. Infective endocarditis: all structural mitral valve disease (particularly MVP with MR) carries increased endocarditis risk — current guidelines recommend antibiotic prophylaxis only for highest-risk patients (prosthetic valves, prior endocarditis, congenital cyanotic heart disease) before dental procedures. Pregnancy: severe MS is the most dangerous valvular lesion in pregnancy — the physiological increase in heart rate and blood volume raises the transmitral gradient substantially, precipitating acute pulmonary oedema; pre-pregnancy PMBC for symptomatic MS is strongly recommended.

Primary prevention of rheumatic heart disease (still the dominant cause of MS and MR globally): prompt diagnosis and antibiotic treatment of group A streptococcal pharyngitis (10-day course of benzylpenicillin or amoxicillin) prevents the autoimmune rheumatic fever response that leads to valvular damage; secondary prophylaxis with monthly benzathine penicillin G (1.2 million units IM) for 10 years or until age 21 (whichever is longer) in patients who have had rheumatic fever prevents recurrent attacks and further valve damage — highly effective in preventing MS progression. All patients with confirmed mitral valve disease should be enrolled in a structured surveillance programme: echocardiographic monitoring frequency guided by disease severity — asymptomatic mild MR: TTE every 3-5 years; asymptomatic moderate MR: TTE every 1-2 years; asymptomatic severe MR: TTE every 6-12 months (more frequent if LVEF approaching the intervention threshold). Endocarditis prevention: antibiotic prophylaxis before dental procedures is recommended for highest-risk patients (those with prosthetic mitral valves, prior endocarditis, or complex congenital heart disease), not for MVP without MR under current guidelines; meticulous oral and dental hygiene reduces bacteraemia risk. Thromboembolism prevention: anticoagulation with warfarin (INR 2.5-3.5) for all patients with rheumatic MS and AF (DOAC data in rheumatic valvular AF are limited; warfarin remains standard); left atrial appendage occlusion (Watchman device) as an alternative to anticoagulation in those with AF and high bleeding risk. Exercise restriction in severe MS — exertion markedly increases heart rate and transmitral gradient, precipitating symptoms. All first-degree relatives of patients with Marfan syndrome or other hereditary connective tissue disorders should undergo screening echocardiography for MVP and aortic root dilatation.

Call emergency services (999/112) immediately for: sudden onset severe breathlessness, orthopnoea, and frothy pink sputum (acute pulmonary oedema from acute mitral regurgitation — chordal rupture, papillary muscle rupture post-MI, or endocarditis causing rapid haemodynamic collapse — requires emergency intensive care and likely urgent surgery); new-onset rapid palpitations with breathlessness in a patient with known mitral valve disease (new AF causing acute haemodynamic deterioration in MS — emergency rate control and anticoagulation required). See your cardiologist urgently for: increasing breathlessness or exercise limitation in a previously stable patient with mitral valve disease (symptom onset from MR or MS triggers urgent review — surgery timing may be indicated); a new or changing heart murmur detected on examination with fever (possible infective endocarditis — requires urgent echocardiography and blood cultures before starting antibiotics). See your GP for: symptoms of heart failure (ankle swelling, breathlessness on exertion, orthopnoea, reduced exercise tolerance) — a new murmur may be detected on examination indicating significant MR or MS; palpitations or irregular heartbeat (new AF in mitral valve disease requires immediate anticoagulation to reduce stroke risk). All patients diagnosed with MVP or rheumatic valve disease should be under annual cardiological review with surveillance echocardiography — the timing of intervention is critical to prevent irreversible LV damage in MR and thromboembolic events in MS.