Mitral valve prolapse
Mitral valve prolapse (MVP) is defined as an abnormal displacement of the mitral valve leaflets into the left atrium during ventricular systole. The condition was first described by John Brereton Barlow in 1966 and was subsequently termed mitral valve prolapse by John Michael Criley. It is also known as click murmur syndrome, myxomatous mitral valve syndrome, billowing mitral cusps syndrome, floppy mitral valve syndrome, Barlow's Syndrome. Prolapse occurs when the mitral valve leaflets are displaced more than 2 mm above the mitral annulus high points. The condition can be further divided into classic and nonclassic subtypes based on the thickness of the mitral valve leaflets: up to 5 mm is considered nonclassic, while anything beyond 5 mm is considered classic MVP (Figure 1).
The incidence of MVP in the general population has historically ranged from 5% to 15%, but data from the community-based Framingham study, employing rigid diagnostic criteria, suggest a much lower rate of around 2–3%. MVP is more frequent in young women than in men. It commonly occurs with heritable connective tissue disorders, including Marfan syndrome, Ehlers-Danlos syndrome, osteogenesis imperfecta, and pseudoxanthoma elasticum. In fact, 90% of patients with Marfan syndrome have MVP due to the increased redundancy of the mitral leaflets and apparatus that occur as a result of myxomatous degeneration. Thoracic skeletal abnormalities such as straight thoracic spine and pectus excavatum are commonly associated with MVP. Primary MVP can be familial or nonfamilial. Familial MVP is transmitted as an autosomal trait, and several chromosomal loci have been identified.
Myxomatous proliferation is the most common pathologic basis for MVP, and it can lead to myxomatous degeneration of the loose spongiosa and fragmentation of the collagen fibrils. Patients with classic mitral valve prolapse have excess connective tissue that thickens the spongiosa and separates collagen bundles in the fibrosa. This is due to an excess of dermatan sulfate, a glycosaminoglycan. This weakens the leaflets and adjacent tissue, resulting in increased leaflet area and elongation of the chordae tendineae. Elongation of the chordae tendineae may also cause rupture. Disruption of the endothelium may predispose patients to infectious endocarditis and thromboembolic complications. However, MVP can be also characterized by a mild buckling of an otherwise anatomically normal valve.
Mitral valve prolapse is often diagnosed from the physical examination, when the classic auscultatory finding of a mid-to-late systolic click and/or murmur is appreciated. Alternatively, it may be incidentally diagnosed during routine echocardiography or discovered when complications of MVP manifest. Echocardiography is the most useful method of diagnosing a prolapsed mitral valve. Two- and three-dimensional echocardiography are particularly valuable as they allow visualization of the mitral leaflets relative to the mitral annulus. Leaflet thickness and their displacement relative to the annulus can be measured. The billowing valve with prolapse is generally associated with excess tissue, chordal elongation, and free-edge prolapse, which is initially late systolic and later with further chordal elongation may become holosystolic. MVP can also be consequent to a flail mitral valve, which is often associated with chordae rupture, although some patients may have extreme chordal elongation without rupture (Figure 2). MVP is the most common cause of isolated mitral regurgitation. In Carpentier's functional classification of mitral valve disease - used to describe the mechanism of valvular dysfunction - MPV belongs to the II type (excess leaflet motion) (Figure 3).
Signs and symptoms
The classic auscultatory finding is a mid-to-late systolic click, which is present due to the leaflets prolapsing into the left atrium resulting in tensing of the mitral valve apparatus. It may or may not be followed by a high-pitched, mid-to-late systolic murmur at the cardiac apex. The midsystolic click can vary in intensity and timing, primarily depending on left ventricular volume. Dynamic auscultation is often useful for establishing the diagnosis of MVP syndrome. Changes in LV end-diastolic volume result in changes in the timing of the midsystolic click(s) and murmur. When end-diastolic volume is decreased (such as with standing), MVP occurs earlier in systole and the click-murmur complex occurs shortly after the first heart sound. In contrast, any maneuver that augments the volume of blood in the ventricle reduces myocardial contractility or increases LV afterload (i.e. during squatting) lengthens the time from onset of systole to occurrence of MVP and the click-murmur complex moves toward the second heart sound.
Most patients are asymptomatic. Symptomatic patients with MVP may show symptoms related to autonomic dysfunction, such as easy fatigability, dizziness, palpitations, atypical chest pain. Occasionally, supraventricular arrhythmias observed in MVP are associated with increased parasympathetic tone. Later, as the disease progresses, symptoms of congestive heart failure may appear.
Common general physical features associated with MVP include asthenic body habitus, straight-back syndrome, pectus excavatum, hypermobility of the joints and Marfan syndrome features.
The M-mode echocardiogram visualizes the classic appearance of mitral prolapse as a posterior bowing of the posterior leaflet or both mitral leaflets in systole. The bowing can be present either throughout the entire systole or confined to the late systole, and occurs simultaneously with the systolic click.
To establish the diagnosis two-dimensional transthoracic echocardiography (TTE) must show that one or both mitral leaflets billow by at least 2 mm into the left atrium during systole (Figure 4, videos 1 and 2). Thickening of the involved leaflet to greater than 5 mm supports the diagnosis and identifies the classical type of MVP. This finding is also helpful in identifying patients at significant risk for developing severe MR or infective endocarditis. Leaflet redundancy is often associated with an enlarged mitral annulus and elongated chordae tendineae. Left ventricular function should be carefully assessed: chronic overload of mitral regurgitation results in progressive increase in left ventricular dimensions, particularly in diastole. End-systolic diameter tends to fall due to the large stroke volume, thus making conventional measurements of left ventricular systolic function from fractional shortening or ejection fraction misleading. There may be left atrial dilatation, depending on the presence and severity of mitral regurgitation (MR). Pulmonary hypertension may occur, with associated RV dysfunction. In some patients, after an initially prolonged asymptomatic interval, the entire process may enter an accelerated phase as a result of left atrial and ventricular dysfunction and atrial fibrillation. In some instances, spontaneous rupture of MV chordae will occur. Involvement of other valves may be present. Tricuspid valve prolapse may occur in 40% of patients with MVP. Pulmonic and aortic valve prolapses occur in 2% to 10% of patients with MVP.
|Video 1||Video 2|
Mitral valve prolapse and resulting regurgitation can be of variable degrees, ranging from mild to severe (video 3). Determination of the severity of mitral regurgitation should follow the same criteria applied to mitral regurgitation due to other causes, including the vena contracta and PISA method (see Mitral Regurgitation). It must be emphasized that the PISA method is based on the assumption of hemispheric symmetry of the velocity distribution proximal to the regurgitant lesion, which may not hold for very eccentric jets, as it may happen in MVP. Colour flow mapping and continuos wave doppler shows predominantly late systolic mitral regurgitation.
Transesoephageal echocardiographic (TOE) images may also help in delineating clearer images and accurate assessment of the exact prolapsing portion of the leaflet. Detailed assessment of the valve structure and function is crucial particularly when considering valve repair. Although 2-dimensional (2D) TTE and TEE echocardiography provide precise information regarding MV anatomy, three-dimensional (3D) TTE and 3D TOE could increase the understanding of more complex abnormalities of MV apparatus and individual scallop identification, and has been applied to the evaluation of surgical MV prolapse (video 4). From the parasternal view (including real-time standard images and zoom images), leaflet and chordae morphology is easily detected, while apical full-volume analysis allowed the generation of a larger single pyramid of data and a complete visualization of all segments of the valve in the so-called atrial “surgical view”. However, the best 3D echo method to quantitate MR severity is still not defined.
|Video 3||Video 4|
The natural history of asymptomatic MVP is heterogeneous and can vary from benign and normal life expectancy to adverse with significant morbidity or mortality, including clinically significant mitral regurgitation, infective endocarditis, sudden cardiac death, and cerebrovascular ischaemic events. The major predictors of mortality are moderate to severe MR and an ejection fraction less than 50%. Echocardiographic evidence of thickened MV leaflets (5 mm or greater) is also a predictor of complications related to MVP.
Management of severe MR due to MVP is almost always by surgical leaflet repair with or without ring insertion, particularly in patients with posterior leaflet prolapse. Results of anterior leaflet repair is now very satisfactory in well-selected cases. In patients with chronic atrial fibrillation and severely dysmorphic mitral leaflets, valve replacement may be a better option.
Prevention of infective endocarditis
Individuals with MVP are at higher risk of infective endocarditis. This risk is approximately three- to eightfold the risk of infective endocarditis in the general population. Previous American Heart Association Guidelines on Prevention of Infective Endocarditis recommended prescribing antibiotics to patients with MVP associated to valvular regurgitation and/or thickened leaflets before invasive procedures, including dental procedures. In 2007, indications have been revised, concluding that "prophylaxis for dental procedures should be recommended only for patients with underlying cardiac conditions associated with the highest risk of adverse outcome from infective endocarditis". Therefore, antibiotic prophylaxis is no longer indicated for patients with MVP.
- Barlow JB, Bosman CK. Aneurysmal protrusion of the posterior leaflet of the mitral valve. An auscultatory-electrocardiographic syndrome. Am Heart J. 1966 Feb;71(2):166-78.
- Criley JM, Lewis KB, Humphries JO, Ross RS. Prolapse of the mitral valve: clinical and cine-angiocardiographic findings. Br Heart J. 1966 Jul;28(4):488-96.
- Freed LA, Levy D, Levine RA, Larson MG, Evans JC, Fuller DL, Lehman B, Benjamin EJ. Prevalence and clinical outcome of mitral-valve prolapse. N Engl J Med. 1999 Jul 1;341(1):1-7.
- Hayek E, Gring CN, Griffin BP. Mitral valve prolapse. Lancet. 2005 Feb 5-11;365(9458):507-18.
- Olsen EG, Al-Rufaie HK. The floppy mitral valve. Study on pathogenesis. Br Heart J 1980; 44: 674–83.
- Vahanian A, Alfieri O, Andreotti F, Antunes MJ, Barón-Esquivias G, Baumgartner H, Borger MA, Carrel TP, De Bonis M, Evangelista A, Falk V, Iung B, Lancellotti P, Pierard L, Price S, Schäfers HJ, Schuler G, Stepinska J, Swedberg K, Takkenberg J, Von Oppell UO, Windecker S, Zamorano JL, Zembala M; ESC Committee for Practice Guidelines (CPG), Bax JJ, Baumgartner H, Ceconi C, Dean V, Deaton C, Fagard R, Funck-Brentano C, Hasdai D, Hoes A, Kirchhof P, Knuuti J, Kolh P, McDonagh T, Moulin C, Popescu BA, Reiner Z, Sechtem U, Sirnes PA, Tendera M, Torbicki A, Vahanian A, Windecker S; Document Reviewers:, Popescu BA, Von Segesser L, Badano LP, Bunc M, Claeys MJ, Drinkovic N, Filippatos G, Habib G, Kappetein AP, Kassab R, Lip GY, Moat N, Nickenig G, Otto CM, Pepper J, Piazza N, Pieper PG, Rosenhek R, Shuka N, Schwammenthal E, Schwitter J, Mas PT, Trindade PT, Walther T. Guidelines on the management of valvular heart disease (version 2012): The Joint Task Force on the Management of Valvular Heart Disease of the European Society of Cardiology (ESC) and the European Association for Cardio-Thoracic Surgery (EACTS). Eur Heart J. 2012 Oct;33(19):2451-96.
- Bonow RO, Carabello BA, Chatterjee K, de Leon AC Jr, Faxon DP, Freed MD, Gaasch WH, Lytle BW, Nishimura RA, O'Gara PT, O'Rourke RA, Otto CM, Shah PM, Shanewise JS, Smith SC Jr, Jacobs AK, Adams CD, Anderson JL, Antman EM, Fuster V, Halperin JL, Hiratzka LF, Hunt SA, Lytle BW, Nishimura R, Page RL, Riegel B. ACC/AHA 2006 guidelines for the management of patients with valvular heart disease: a report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines (writing Committee to Revise the 1998 guidelines for the management of patients with valvular heart disease) developed in collaboration with the Society of Cardiovascular Anesthesiologists endorsed by the Society for Cardiovascular Angiography and Interventions and the Society of Thoracic Surgeons. J Am Coll Cardiol. 2006 Aug 1;48(3):e1-148. Erratum in: J Am Coll Cardiol. 2007 Mar 6;49(9):1014. PubMed PMID: 16875962.
- Lancellotti P, Moura L, Pierard LA, Agricola E, Popescu BA, Tribouilloy C, Hagendorff A, Monin JL, Badano L, Zamorano JL; European Association of Echocardiography. European Association of Echocardiography recommendations for the assessment of valvular regurgitation. Part 2: mitral and tricuspid regurgitation (native valve disease). Eur J Echocardiogr. 2010 May;11(4):307-32.
- Wilson W, Taubert KA, Gewitz M, Lockhart PB, Baddour LM, Levison M, Bolger A, Cabell CH, Takahashi M, Baltimore RS, Newburger JW, Strom BL, Tani LY, Gerber M, Bonow RO, Pallasch T, Shulman ST, Rowley AH, Burns JC, Ferrieri P, Gardner T, Goff D, Durack DT; American Heart Association Rheumatic Fever, Endocarditis, and Kawasaki Disease Committee; American Heart Association Council on Cardiovascular Disease in the Young; American Heart Association Council on Clinical Cardiology; American Heart Association Council on Cardiovascular Surgery and Anesthesia; Quality of Care and Outcomes Research Interdisciplinary Working Group. Prevention of infective endocarditis: guidelines from the American Heart Association: a guideline from the American Heart Association Rheumatic Fever, Endocarditis, and Kawasaki Disease Committee, Council on Cardiovascular Disease in the Young, and the Council on Clinical Cardiology, Council on Cardiovascular Surgery and Anesthesia, and the Quality of Care and Outcomes Research Interdisciplinary Working Group. Circulation. 2007 Oct 9;116(15):1736-54.
- Pepi M, Tamborini G, Maltagliati A, Galli CA, Sisillo E, Salvi L, Naliato M, Porqueddu M, Parolari A, Zanobini M, Alamanni F. Head-to-head comparison of two- and three-dimensional transthoracic and transesophageal echocardiography in the localization of mitral valve prolapse. J Am Coll Cardiol. 2006 Dec 19;48(12):2524-30.
- Feigenbaum H. Echocardiography, Sixth ed. Lea and Febiger, Malvern, PA. 2009.
- C. Otto. Textbook of Clinical Echocardiography, 4th Ed. Elsevier, 2009.
- Shah PM. Current concepts in mitral valve prolapse--diagnosis and management. J Cardiol. 2010 Sep;56(2):125-33.
- Mohty D, Orszulak TA, Schaff HV, Avierinos JF, Tajik JA, Enriquez-Sarano M. Very long-term survival and durability of mitral valve repair for mitral valve prolapse. Circulation 2001; 104: I1–I7.