Mitral valve prolapse (MVP) is a relatively common heart valve abnormality caused by prolapse of one or both of the mitral leaflets into the left atrium. MVP is defined on echocardiography as single or bileaflet prolapse of at least 2 mm, with or without leaflet thickening.¹ In the 1980s, various nonspecific symptoms were attributed to MVP, such as atypical chest pain, exertional dyspnoea, palpitations, syncope and anxiety. These were sometimes termed "mitral valve prolapse syndrome". However, data from the Framingham study and others do not support a link between these symptoms and MVP.¹

Epidemiology

The prevalence of mitral valve prolapse (MVP) is estimated as 2-3% of the population, with an equal sex ratio.¹

Aetiology and associated conditions¹

The cause is often multifactorial.

• A common occurence is leaflet thickening and redundancy, known as myxomatous degeneration - not related to hypothyroidism but involving the accumulation of proteoglycans on histology. The underlying mechanism is not known.
• Mitral valve prolapse (MVP) may also occur with histologically normal valves. Contributing/associated factors may be:
  • A disproportionately small left ventricular (LV) cavity.
  • Unrepaired secundum atrial defects.
  • Certain recognised syndromes:
    • Marfan's syndrome; recent research suggests 28% prevalence (lower than previously thought).²
    • Ehlers-Danlos syndrome (6% prevalence).
    • Osteogenesis imperfecta.
    • Pseudoxanthoma elasticum.
    • Adult polycystic kidney disease.
• Genetic factors - there is probably a familial, autosomal dominant condition with variable penetrance and variable clinical presentation. There may be other genetic forms.^3,4

Presentation¹

• Mitral valve prolapse (MVP) is generally asymptomatic, unless there are complications such as significant mitral regurgitation. It usually presents as an incidental finding on clinical examination or echocardiogram.
• A careful physical examination is said to be highly sensitive for echocardiographic MVP, although it is not specific (see 'Differential diagnosis', below). MVP may also be found on echocardiography when auscultation is normal. Classical auscultation findings are:
  • A dynamic mid-to-late systolic click, often followed by a late systolic mitral regurgitant murmur.
  • The murmur is dynamic in that it moves within systole as the loading conditions change.
  • There is an earlier click with reduction of end-diastolic volume, e.g. on standing or a Valsalva manoeuvre.
  • The click will be later in systole when the left ventricular (LV) afterload or end-diastolic volume is increased, e.g. by squatting or hand-grips.
• Symptoms of autonomic dysfunction may occur with genetically inherited MVP, e.g. anxiety, panic attacks, palpitations, syncope or presyncope, neuropsychiatric symptoms⁵
• Look for associated conditions, e.g. Marfan's syndrome.

Differential diagnosis¹

A click heard during auscultation may also be due to:

• Redundant leaflets or chordae, without echocardiographic prolapse.
• Bicuspid aortic stenosis.
• Atrial myxoma.
• Pericarditis.

Other causes of mitral regurgitation.

Investigation¹

• Patients with signs of mitral valve prolapse (MVP) should have 2D echocardiography. This shows the prolapse and distinguishes it from other causes of systolic clicks.
• As mentioned above, strict criteria for echocardiographic diagnosis are important to avoid over-diagnosis.
• Transthoracic echocardiography can confirm MVP, but can miss prolapse of the lateral scallop of the valve; transoesophageal echocardiography may be more sensitive.
• ECG and CXR are usually normal unless there has been progression to significant mitral regurgitation. The ECG may show nonspecific ST-segment and T-wave abnormalities.⁵
• If there is doubt about exercise tolerance, an exercise test may be useful.

Management¹

Patients with mitral valve prolapse (MVP) can be classified as at high or low risk of developing severe mitral regurgitation.

Low risk

• Those with no symptoms, only mild regurgitation and stable examination findings, do not need treatment. These patients can be followed up conservatively.
• Symptoms of autonomic dysfunction can be treated with a trial of betablockers and abstinence from caffeine, alcohol and cigarettes.⁵

High risk

Factors which increase the risk of severe mitral regurgitation developing are:

• Age over 50, hypertension or obesity.
• Moderate-severe mitral regurgitation.
• Mitral regurgitation during exercise but not at rest.
• Echocardiographic findings of mitral leaflet thickness >5 mm, posterior leaflet prolapse or increased left ventricular (LV) dimensions.
• Atrial fibrillation.
• Reduced LV systolic function.
• Left atrial enlargement.

Patients at high risk need follow-up to monitor for progressive mitral regurgitation. If this occurs, the surgical repair or replacement of the valve may be needed, and the optimal timing of surgery must be considered.

Prophylaxis

• Anti-thrombotic treatment is not recommended for MVP alone.⁶
• Endocarditis prophylaxis:
  • Patients with MVP are at increased risk of endocarditis if they have:
    • A systolic click and murmur on examination.
    • Myxomatous degeneration and mitral regurgitation on echocardiography.
    • 'High-risk' features (above), such as LV dilatation, left atrial enlargement, leaflet thickening, redundant chordae, or other high-risk features, as above.
  • NICE guidelines state that:⁷
    • Routine antibiotic prophylaxis is not required for most procedures.
    • However, antibiotic cover for infective endocarditis should be given to patients who are receiving antibiotics for a gastrointestinal or genitourinary procedure to an infected site.
    • Patients at risk of endocarditis should be aware of relevant symptoms.

Surgery

Symptoms of heart failure, severity of mitral regurgitation, presence or absence of atrial fibrillation, LV systolic function, LV end-diastolic and end-systolic volumes, and pulmonary artery pressure (at rest and with exercise) all influence the decision to recommend mitral valve surgery.⁸ Valve surgery is indicated for patients with:

• Symptomatic severe mitral regurgitation.
• Patients who are asymptomatic but have LV enlargement (end-systolic diameter >45 mm) or reduced systolic function (ejection fraction <60%).
• Severe mitral regurgitation with atrial fibrillation or pulmonary hypertension (AHA/ACC Class IIa recommendation for valve surgery).

Surgical options are:

• Management of mitral valve prolapse may include valve surgery, particularly in those patients who develop a flail mitral leaflet due to rupture or marked elongation of chordae tendineae.⁸
• Mitral valve repair, usually by leaflet resection, possibly with placement of an annuloplasty ring. Mitral valve repair for mitral valve prolapse is associated with excellent long-term survival and remains superior to mitral valve replacement beyond 10 years and up to 20 years after surgery.⁸
• NICE currently recommends that the evidence for the safety and efficacy of percutaneous mitral valve leaflet repair for mitral regurgitation is currently inadequate.⁹
• A technique using polytetrafluoroethylene neochordae has been used as an alternative to mitral valve surgery.¹⁰

The management of asymptomatic patients with severe mitral regurgitation but preserved LV function is controversial. However, there is a trend towards earlier surgical valve repair for patients with severe mitral regurgitation. This is because:

• There is a high success rate and durability of surgical repair.
• Some research shows improved clinical outcomes with early intervention.
• Occult LV dysfunction can precede symptoms.
• Those with severe mitral regurgitation and a flail valve leaflet may benefit from early surgical repair.

Complications and prognosis¹

Anterior leaflet mitral valve repair is associated with a higher risk for reoperation than posterior leaflet repair.The overall prognosis is excellent for most patients with mitral valve prolapse (MVP), with an expected lifespan similar to the general population. A minority of patients may develop complications such as:

• Progression to severe mitral regurgitation, which may may require surgery.
• There is a small increased risk of sudden cardiac death:
  • The absolute risk is very low but, in patients with myxomatous MVP, it is twice that of the general population.
  • If there is severe mitral regurgitation with a flail leaflet, this carries a higher risk (up to 2% per year).
• There is a small increased risk of infective endocarditis:
  • Without mitral regurgitation, the incidence of infective endocarditis is similar to that of the general population.
  • In patients with MVP and a systolic murmur, the risk increases to about 0.05% per year.
• There is also possibly an increased risk of stroke but this has not been proven.

Screening

It is suggested that first degree relatives of those with mitral valve prolapse (MVP) should have echocardiography to screen for the condition.¹¹

Document references

1. Hayek E, Gring CN, Griffin BP; Mitral valve prolapse. Lancet. 2005 Feb 5-11;365(9458):507-18. [abstract]
2. Taub CC, Stoler JM, Perez-Sanz T, et al; Mitral Valve Prolapse in Marfan Syndrome: An Old Topic Revisited. Echocardiography. 2008 Nov 24. [abstract]
3. Familial Mitral Valve Prolapse (FMVP), Online Mendelian Inheritance in Man (OMIM)
4. Myxomatous Mitral Valve Prolapse 2; MMVP2, Online Mendelian Inheritance in Man (OMIM)
5. Thakkar BV et al; Mitral Valve Prolapse, Medscape, Jul 2008
6. Salem DN, O'Gara PT, Madias C, et al; Valvular and structural heart disease: American College of Chest Physicians Evidence-Based Clinical Practice Guidelines (8th Edition). Chest. 2008 Jun;133(6 Suppl):593S-629S. [abstract]
7. Antimicrobial prophylaxis against infective endocarditis, NICE Clinical Guideline (March 2008)
8. American College of Cardiology/American Heart Association, Guidelines for the Management of Patients with Valvular Heart Disease (2006)
9. Percutaneous mitral valve leaflet repair for mitral regurgitation, NICE Interventional Procedure Guideline (August 2009)
10. Falk V, Seeburger J, Czesla M, et al; How does the use of polytetrafluoroethylene neochordae for posterior mitral valve prolapse (loop technique) compare with leaflet resection? A prospective randomized trial. J Thorac Cardiovasc Surg. 2008 Nov;136(5):1205; discussion 1205-6. Epub 2008 Sep 14. [abstract]
11. Cheitlin MD, Armstrong WF, Aurigemma GP, et al; ACC/AHA/ASE 2003 guideline update for the clinical application of echocardiography: summary article: a report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines (ACC/AHA/ASE Committee to Update the 1997 Guidelines for the Clinical Application of Echocardiography). Circulation. 2003 Sep 2;108(9):1146-62.