Mitral Valve Prolapse

Introduction
Background

Mitral valve prolapse (MVP) is the most common valvular abnormality, affecting approximately 2-6% of the population in the United States. MVP usually results in a benign course. However, it occasionally leads to serious complications, including clinically significant mitral regurgitation, infective endocarditis, sudden cardiac death, and cerebrovascular ischemic events. MVP is also the most common cause of isolated mitral regurgitation in the United States, and it is the most common reason for mitral valve surgery.
Pathophysiology

Most patients with MVP are asymptomatic, and their natural history is benign. However, when large, floppy valves or ruptured chordae tendinea result in severe mitral regurgitation, mitral valve surgery or repair may be necessary. 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. Disruption of the endothelium may predispose patients to infectious endocarditis and thromboembolic complications. However, the vast majority of patients with MVP have only a minor derangement of the mitral valve structure that is usually clinically insignificant.

Frequency
United States


MVP is thought to be inherited with increased expression of the gene in female individuals (2:1). The most common form of inheritance is autosomal dominant, but X-linked inheritance has been described.

MVP 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.

In the 1970s and 1980s, MVP was overdiagnosed because of the absence of rigorous echocardiographic criteria, with a reported prevalence of 5-15%. Subsequently, Levine et al reported that the 2-dimensional echocardiographic characterizations of prolapse, especially on the parasternal long-axis view, are most specific for the diagnosis of MVP.1 Use of these criteria prevent overdiagnosis.

Data from the community-based Framingham study demonstrated that MVP syndrome occurred in only 2.4% of the population.

Mortality/Morbidity

Most patients with MVP are asymptomatic and have a benign prognosis, with survival rates similar to those of the general population. Nonetheless, high-risk patients (ie, those with moderate-to-severe mitral regurgitation) have increased cardiac morbidity and mortality rates, especially if reduced left ventricular systolic function is present.

See Complications.
Sex

MVP occurs more frequently in young women than in men. The most serious consequences of hemodynamically significant mitral regurgitation occur in men older than 50 years.
Age

MVP has been observed in all ages.
Clinical
History

Mitral valve prolapse (MVP) 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.

Most patients are asymptomatic. Symptomatic patients with MVP are separated into 3 categories: (1) those with symptoms related to autonomic dysfunction; (2) those with symptoms related to the progression of mitral regurgitation; and (3) those with symptoms that occur as a result of an associated complication (ie, stroke, endocarditis, or arrhythmia).
Symptoms related to autonomic dysfunction are usually associated with genetically inherited MVP and include the following:
Anxiety
Panic attacks
Arrhythmias
Exercise intolerance
Palpitations
Atypical chest pain
Fatigue
Orthostasis
Syncope or presyncope
Neuropsychiatric symptoms
Symptoms related to progression of mitral regurgitation include the following:
Fatigue
Dyspnea
Exercise intolerance
Orthopnea
Paroxysmal nocturnal dyspnea (PND)
Progressive signs of congestive heart failure (CHF)
ECG usually is normal, but can show nonspecific ST-segment and T wave abnormalities especially in leads II, III, aVF.
MVP is also commonly seen in patients with inheritable connective tissue disorders.

Physical

Clinical characteristics are typically benign in young women, whereas men older than 50 years tend to have serious consequence of mitral regurgitation.

Common general physical features associated with MVP include the following:
Asthenic body habitus
Low body weight or body mass index (BMI)
Straight-back syndrome
Scoliosis or kyphosis
Pectus excavatum
Hypermobility of the joints
Arm span greater than height (which may be indicative of Marfan syndrome)
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.
End-diastolic volume can be reduced by performing a Valsalva maneuver or by having the patient stand. These maneuvers result in an early click, which is close to the first heart sound, and a prolonged murmur. In the supine position, especially with the legs raised for increased venous return, left ventricular diastolic volume is increased, resulting in a click later in systole and a shortened murmur.
Patients with MVP most frequently have symptoms of autonomic dysfunction, including easy fatigability, dizziness, and atypical chest pain. This pain is perhaps related to papillary muscle strain (ie, excessive pulling on the left ventricular wall with prolapsed leaflets in the left atrium).
Causes

MVP usually occurs as an isolated entity. As previously mentioned, it also commonly occurs with heritable disorders of connective tissue. MVP has also been described in association with a secundum atrial septal defect.

http://emedicine.medscape.com/article/155494-overview