7th March 2024

Mitral Valve

Mitral Stenosis

The aetiology of mitral stenosis (MS) is mostly rheumatic or degenerative. 

Rheumatic fever is the most common cause of mitral stenosis worldwide. Its prevalence has greatly decreased in industrialised countries, but it remains a significant healthcare problem in developing countries and affects young patients. 

Rarer causes of mitral stenosis include congenital deformity of the valve, carcinoid syndrome, use of ergot and/or serotonergic drugs such as fenfluramine, SLE, mitral annular calcification due to ageing, and amyloidosis. 

Clinical manifestations

MS usually manifests with dyspnoea or orthopnoea. Patients can have a malar flush, distended neck veins and a low volume pulse which is irregular due to atrial fibrillation. 

It is characterised by a mid-late diastolic rumbling murmur heard best in expiration with presystolic accentuation because at the end of diastole the atria contract, squirting the last of the blood into the ventricle. A loud S1 with an opening snap (due to thickened valve leaflets and high LA pressures) and a loud P2 may be heard. 

In severe MS, the murmur lasts longer and the opening snap comes closer to S2. A severely calcified valve will result in no opening snap.

Diagnosis

The ECG may show atrial fibrillation and chest x-ray may show a double right heart border indicating an enlarged left atrium, prominent pulmonary artery and Kerley B lines. 

Echocardiography is the preferred method for diagnosis, assessment of severity, and haemodynamic consequences of mitral stenosis. A TOE should be performed to exclude LA thrombus before percutaneous mitral commissurotomy or after an embolic episode, or when TTE is suboptimal. 

Stress testing is indicated in patients with no symptoms or symptoms equivocal or discordant with the severity of mitral stenosis. Exercise echocardiography is also used. 

Management

Diuretics, beta-blockers, digoxin, non-dihydropyridine calcium channel blockers and ivabradine can improve symptoms. 

Anticoagulation with vitamin K antagonist (warfarin) with a target INR between 2 and 3 is indicated in patients with AF. Patients with moderate-to-severe mitral stenosis and AF should be kept on warfarin and not receive NOACs. 

Definitive therapy requires a mechanical solution by percutaneous balloon commissurotomy, surgical mitral valve repair, or valve replacement. Definitive therapy should be offered to patients with severe symptomatic disease who are unlikely to benefit from medical therapy alone, and may be considered in some patients with severe asymptomatic disease. 

A systematic review found a lack of evidence concerning the effectiveness of the various treatments for valvular heart disease in pregnancy. Diuretics are given to control mild symptoms. If symptoms worsen and heart failure threatens the life of the mother and/or foetus, balloon valvotomy can be performed safely.

The contraindications for percutaneous mitral balloon valvotomy are as follows:

• Moderate to severe MR.
• Heavily calcified mitral valve.
• LA thrombus.
• Concomitant coronary artery disease or other valve disease requiring surgery.

Mitral Regurgitation

Mitral regurgitation (MR) may present with dyspnoea, usually on exertion, palpitations, and/or decreased exercise tolerance. It typically presents as a holosystolic blowing murmur at the apex, radiating to the axilla. 

A transthoracic echocardiogram is the diagnostic test of choice in identifying the presence, severity, and mechanism of MR. Colour Doppler flow and continuous-wave Doppler studies can assess the severity of regurgitation, left ventricular dimensions, size and function of the right ventricle, and pulmonary artery systolic pressure. 

Surgical treatment is the best available treatment option, although percutaneous approaches have gained significant potential. Asymptomatic chronic MR with LVEF, more than 60% are treated with ACEi and beta blockers. All patients with MR may be offered antibiotic prophylaxis prior to dental and/or urological procedures, depending on their risk profiles. The most common complications of MR include AF, pulmonary hypertension, LV dysfunction, CCF and prosthesis stenosis.

References

• Mitral Stenosis BMJ Best Practice. [Online] https://bestpractice.bmj.com/topics/en-gb/323
• Mitral Regurgitation BMJ Best Practice. [Online] https://bestpractice.bmj.com/topics/en-gb/322
• Alec Vahanian et al. ESC/EACTS Scientific Document Group, 2021 Guidelines for the management of valvular heart disease: Developed by the Task Force for the management of valvular heart disease of the European Society of Cardiology (ESC). European Heart Journal, Volume 43, Issue 7, 14 February 2022. https://doi.org/10.1093/eurheartj/ehab395