Excerpt from Mitral Valve Prolapse

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Background

Mitral valve prolapse (MVP) can occur in a multitude of disorders and, in most instances, it reflects a normal variant rather than a single disease process.

Despite years of research, the symptomatology and significance of MVP remain controversial. It was termed the disease of the decade in the 1980s, but now some consider it an interesting finding of dubious importance. Initial studies that reported associated symptoms of MVP as chest pain, dyspnea, anxiety, and panic, were probably flawed by recruitment bias. Recent studies imply that the incidence of MVP previously was overestimated by inaccurate echocardiographic diagnostic criteria and that associated symptoms, other than palpitations, are uncommon.

Despite this, patients with MVP are at risk for endocarditis, stroke, mitral regurgitation (MR), mitral valve replacement (MVR) surgery, and sudden death.

Pathophysiology

A myxomatous degeneration from collagen dissolution leads to excess mucopolysaccharides in the middle spongiosa layer of the mitral valve leaflets, resulting in stretching of the leaflets and the chordae tendineae.

MVP occurs when the left ventricular (LV) size is small in comparison to an enlarged mitral annulus, leaflets, or chordae tendineae, and it can be induced in healthy women with typical body habitus following dehydration that is reversed with rehydration. MVP resolves during pregnancy and following weight gain in anorexic patients.

Recent studies have shown that abnormalities of elastic fibers found in floppy mitral valves are related to genetic variants in fibrillin, one of the components of the microfibrils, as well as elastin and collagen I and II.

A constellation of abnormalities (eg, increased sensitivity to adrenergic stimuli, increased catecholamines, abnormal beta-receptors, increased atrial natriuretic factor, renin-aldosterone dysregulation, decreased intravascular volume, magnesium deficiency) has been thought to lead to chest pain, dyspnea, fatigue, dizziness, near-syncope symptoms, and anxiety in a subset of patients with MVP.

Cardiac manifestations include supraventricular arrhythmias, palpitations, mitral regurgitation, bacterial endocarditis, and sudden death. Chest pain may not be more common in patients with MVP than in the general population, and it may be attributed to myofascial syndromes, hyperventilation, coronary spasm, esophageal dysmotility, or gastroesophageal reflux.

MVP can result in cerebrovascular ischemia, which may be related to abnormal platelet activity or protein C or S deficiencies.

Frequency

United States

MVP can be identified by echocardiography in 3-4% of the general population, and it is identified in 7% of autopsies.

International

The worldwide incidence of MVP is similar to that in the United States.

Mortality/Morbidity

• In general, MVP is a benign disorder, but it may account for the majority of isolated cases of mitral regurgitation (MR), 90% of cases of ruptured chordae tendineae, 40% of strokes in young patients, and 10-15% of cases of endocarditis.
• Those with structural abnormalities (ie, thickened, deformed, or redundant mitral valve leaflets) are more likely to suffer complications (eg, progressive MR, endocarditis, sudden death).
• Cases of MVP with a murmur and not just an isolated click have a general mortality rate that is increased by 15-20%.

Race

Prevalence is similar among different ethnic groups.

Sex

• The female-to-male ratio is approximately 3:1.
• Men older than 45 years have twice the risk of MR and endocarditis.

Age

Age of onset is 10-16 years.

• MVP is uncommon before the adolescent growth spurt occurs. It usually is detected in young adulthood.
• Although MVP is considered congenital, echocardiographic findings typically are absent in newborns.

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