Mitral Valve Prolapse
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- Mitral valve prolapse (MVP) is a systolic billowing of one or both mitral leaflets into the left atrium (LA) during systole ± mitral regurgitation (MR).
- More specifically, MVP is a single or bileaflet prolapse of at least 2 mm superior displacement into the LA during systole on the parasternal long-axis annular plane of the valve on echocardiogram ± leaflet thickening.
- Classic: prolapse with >5 mm of leaflet thickening
- Nonclassic: prolapse with <5 mm of leaflet thickening
- Synonym(s): systolic click-murmur syndrome; billowing mitral cusp syndrome; myxomatous mitral valve; floppy valve syndrome; redundant cusp syndrome; Barlow syndrome
- Predominant age: MVP has been described in all age groups.
- Initial descriptions based on clinical examinations suggested a 2:1 female predominance. Using modern echocardiogram criteria, men and women are affected equally (1).
- The most serious consequences of hemodynamically significant MR occur in patients age >50 years (1).
MVP is the most common valvular abnormality, affecting 2–3% of the general population (1).
Etiology and Pathophysiology
- The pathology causing MVP is multifactorial and includes the following:
- Abnormal valve tissue
- Myxomatous degeneration: redundant layers of leaflet “hooding” the cords, chordal elongation, and annular dilatation
- Myxoid leaflets are more elastic and less stiff than normal valves.
- Chordal rupture is more common.
- Disparity in size between the mitral valve and the left ventricle (LV)
- Connective tissue disorders
- Abnormal valve tissue
- MVP is often associated with variable degrees of MR, which occurs in 9% of patients.
- The degree of MR depends on the degree of leaflet thickening and amount of flail or partially flail segments (2). When this occurs, 10-year mortality is 37% (2).
- Frequently, there is enlargement of the LA and LV.
- Mitral annulus is often dilated.
- Involvement of other valves may occur (tricuspid valve prolapse 40%, pulmonic prolapse and aortic prolapse 2–10%).
- Possible increased vagal tone
- Possible increased urine epinephrine and norepinephrine
- MVP patients often have orthostatic hypotension and tachycardia.
- Genetics causes proliferation of the spongiosa layer of the leaflets and fibrosis on the surface of them (1).
- Thinning and elongation of chordae tendineae
- The mitral valve differentiates during days 35 to 42 of fetal development, the same time as differentiation of the vertebrae and ribs.
- Familial MVP is inherited as an autosomal dominant trait but with variable expressivity and incomplete penetrance.
- Two genetic loci identified
- MMVP1 on chromosome 16p11.2–p12.1
- MMVP2 on chromosome 11p15.4
- MVP is a primary cardiovascular disorder.
- MVP is more likely to occur in patients with connective tissue disorders (see “Commonly Associated Conditions”).
- Physical characteristics associated with MVP
- Straight thoracic spine
- Pectus excavatum
- Asthenic body habitus
- Low body mass index (BMI)
- Scoliosis or kyphosis
- Hypermobility of the joints
- Arm span > height
- Narrow anteroposterior (AP) diameter of the chest
Commonly Associated Conditions
- Marfan syndrome (91% of Marfan syndrome patients have MVP, although large majority of MVP patients do not meet criteria for Marfan.)
- Ehlers-Danlos syndrome
- Hypertrophic cardiomyopathy
- Pseudoxanthoma elasticum
- Osteogenesis imperfecta
- von Willebrand disease
- Primary hypomastia
- Graves disease
- Rheumatic heart disease