Pediatric Mitral Valve Prolapse

Updated: Mar 21, 2017
  • Author: Poothirikovil Venugopalan, MBBS, MD, FRCPCH; Chief Editor: Syamasundar Rao Patnana, MD  more...
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Overview

Background

Mitral valve prolapse (MVP), the most common anomaly of the mitral valve apparatus, occurs when one or both mitral valve leaflets excessively billows into the left atrium toward the end of systole. Mitral regurgitation (MR) develops in some patients with mitral valve prolapse, particularly those with more significant prolapse, when the valve edges fail to coapt. An extreme form of prolapse could include chordal rupture, in which the prolapsed mitral valve is flail. Mitral valves excised from patients with severe MR secondary to mitral valve prolapse have large leaflets and various histologic alterations.

Besides the symptoms attributable to the MR, various neuroendocrine and autonomic disturbances occur in some patients with mitral valve prolapse. In these patients, prolapse may be an epiphenomenon of the underlying autonomic or neurohumoral illness. The term mitral valve prolapse syndrome is often used to refer to the collection of these manifestations. However, in a significant proportion of patients, the mitral valve prolapse is trivial, and no such associated manifestations are present. In these patients, mitral valve prolapse constitutes an essentially benign condition.

Mitral valve prolapse syndrome was recognized as early as 1916, when Sir James MacKenzie described the soldier's heart in spare, thin young men with great vasomotor instability, easy fatigability, breathlessness, and pain over the region of the heart. Kerley first described the syndrome in 1920, and Lincoln described the syndrome in 1928. In 1963, Barlow and colleagues made the first clinical diagnosis of the syndrome as it is known today. The advent of echocardiography led to further advances and formed the basis of current knowledge.

Idiopathic mitral valve prolapse may be congenital in some patients, but recognition may be delayed until adolescence or adulthood. Associated complicating issues include cardiac arrhythmia, heart failure secondary to severe MR (rare), and, occasionally, thromboembolic events. Familial cases are known and occur in an autosomal dominant pattern with variable penetrance and expression (familial mitral valve prolapse).

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Pathophysiology

Mitral valve prolapse (MVP) is a heterogeneous disorder and may originate from various underlying causes affecting one or more portions of the mitral valve leaflets, chordae tendineae, papillary muscle, and/or valve annulus. The syndrome may occur in isolation or in association with generalized connective tissue abnormalities, such as Marfan syndrome [1] and Ehlers-Danlos syndrome, in which specific enzymatic defects are found. Mitral valve prolapse may occur in the context of inflammatory disease such as rheumatic fever or endocarditis. [2]

Isolated mitral valve prolapse can be sporadic or familial, demonstrating autosomal dominant and X-linked inheritance. Three different loci on chromosomes 16, 11, and 13 are linked to mitral valve prolapse, but no specific gene has been described. Another locus on chromosome X has also been found to cosegregate with a rare form of mitral valve prolapse called X-linked myxomatous valvular dystrophy. [3]

Isolated mitral valve prolapse has been independently associated with low body mass index; however, the reason for this association remains unexplained. [4]

Mitral valve prolapse may be secondary to rupture or dysfunction of the papillary muscles following myocardial infarction or ischemia, rupture of chordae tendineae due to infective endocarditis, or abnormal left ventricular wall motion in the setting of myocardial ischemia and/or primary myocardial disease. In these patients, the posterior leaflet in the floppy valve tends to have a significantly longer basal free-edge length and more frequent chordal rupture compared with patients with postinflammatory disease.

A connective tissue abnormality, possibly related to collagen metabolism, may underlie the idiopathic disorder. Abnormalities of collagen and elastic fibers have been documented in floppy mitral valves (FMV). Urokinase-plasminogen activator (PLAU), which is suggested in the pathogenesis of elastin and collagen degradation in arterial aneurysm, has also been implicated in mitral valve prolapse (PLAU T4065C TC genotype). TGFBR2 mutations have also been recognized among patients with mitral valve prolapse and Marfanlike phenotype. [5] A Marfanlike phenotype A locus for autosomal dominant mitral valve prolapse has also been described on chromosome 11p15.4.

Investigators have also suggested that floppy mitral valve/mitral valve prolapse (FMV/MVP) syndrome may not be attributable alone to the severity of the mitral regurgitation (MR) and that hypersensitivity to adrenergic stimulation related to β1-adrenergic receptor polymorphism may play a partial role in symptoms, particularly in women with FMV/MVP. [6]

Electron microscopy of the affected valve leaflets shows a haphazard arrangement, disruption, and fragmentation of collagen fibrils. Myxomatous proliferation of the mitral valve, in which the middle spongiosa layer is predominantly involved, leads to the presence of unusually large amounts of myxomatous material and acid mucopolysaccharide. Degeneration of collagen within the central core of the chordae tendineae may lead to chordal rupture. Mitral valve prolapse can also follow rheumatic fever and myocardial infarction, in which case the prolapse is secondary to inflammatory or ischemic chordal rupture, respectively.

Metabolic and neuroendocrine abnormalities also occur in mitral valve prolapse and may separately result in prolapse unrelated to a connective tissue disorder. Adolescents with anorexia nervosa form a distinct group, in whom mitral valve prolapse develops as a result of reduced left ventricular filling. [7] In such patients, increased norepinephrine and epinephrine may be found. Abnormalities in autonomic and neuroendocrine regulation have been demonstrated, including hyper-response to adrenergic stimulation, parasympathetic abnormalities (vagal withdrawal), altered baroreflex activity, renin-aldosterone regulation abnormalities, decreased intravascular volume, decreased left ventricular volume in upright posture, and atrial natriuretic factor secretion abnormalities.

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Etiology

Heritable disorders of connective tissue include the following:

Skeletal abnormalities include the following:

Other diseases include the following:

Several reports suggest magnesium deficiency underlies the disease in some patients.

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Epidemiology

United States data

Mitral valve prolapse (MVP) is the most prevalent cardiac valve disorder. Mitral valve prolapse is a common finding in otherwise healthy teenagers and young adults, particularly those patients who present with palpitations, chest pain, or dizziness. More than one third of cases in younger children are associated with other congenital heart defects. Reports vary, but 3-5% of pediatric patients likely have clinically significant mitral valve prolapse. However, a report from California places the prevalence at only 0.6%. [9]

International data

Prevalence rates are 1-2% in children and 5-15% in adolescents and young adults. In a series of 278 surgically removed mitral valves with pure regurgitation, mitral valve prolapse was present in 43%. [10]

Sex- and age-related demographics

Some studies show mitral valve prolapse is twice as frequent in females as in males.

Although findings are more frequent in older children and adults, the defect is believed to be present at birth.

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Prognosis

Mitral valve prolapse (MVP) is not progressive in childhood, and specific therapy is not indicated for the vast majority of patients.

Progression to significant mitral regurgitation (MR) or sudden death is rare.

Asymptomatic patients with isolated mitral systolic clicks need only counseling and reassurance.

Morbidity/mortality

When present, associated abnormalities dictate the risk. Presence of significant MR and prolonged QT interval on ECG may also influence outcome. QT prolongation is slightly more prevalent among patients with mitral valve prolapse and may be associated with repolarization abnormalities and arrhythmia vulnerability. When severe, MR can lead to heart failure.

As noted above, mortality is rare in children. Sudden death is also rare and occurs more often in young women with a history of recurrent syncope, sustained supraventricular tachycardia, or complex ventricular tachycardia. Family history of cardiac sudden death often is a risk-stratifying indicator.

Development of MR and the progression of mild or moderate MR to severe MR are important determinants to morbidity. One study showed that the prevalence of MR increased from 29% of patients to 43% of patients during 4.3 years of follow-up. [11]  Other possible complications include congestive cardiac failure, rupture of chordae tendineae, infective endocarditis (in 0.1-0.3 cases per 100 patient years), thromboembolic phenomena including cerebrovascular accidents, and sudden death. Cardiac arrhythmias such as ventricular tachycardia and ventricular fibrillation are more common in mitral valve prolapse.

Complications

Complications include the following:

  • MR: Progression or appearance of MR is one of the main complications. Over 4.3 years, approximately 14% of patients developed MR.
  • Congestive cardiac failure
  • Rupture of chordae tendineae
  • Infective endocarditis, in 0.1-0.3 cases per 100 patient years
  • Thromboembolic phenomena including cerebrovascular accidents and sudden death
  • Cardiac arrhythmia
  • Ventricular tachycardia and fibrillation
  • Syncope [12]
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Patient Education

Note the following:

  • Careful explanation of the clinical findings and the nature of mitral valve prolapse (MVP) help to reassure the anxious patient.
  • Normal activity can be allowed if mitral regurgitation (MR) is not severe
  • Antibiotic prophylaxis during surgery and dental procedures is only necessary if associated MR is present.
  • The vast majority of patients with mitral valve prolapse remain asymptomatic for their entire lives and require observation every few years for reassurance.
  • Patients with orthostatic syncope secondary to dehydration should take extra salt and water during and following sport activities and competition.
  • Pregnancy requires infective endocarditis prophylaxis during delivery. Other implications are based on the severity of MR.
  • For patient education resources, see the  Heart Health Center, as well as  Mitral Valve Prolapse.
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