Mitral Valve Prolapse

Mitral Valve Prolapse
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Mitral Valve Prolapse
Mitral valve prolapse (MVP) syndrome has been given many names, including the systolic click
murmur syndrome, Barlow syndrome, billowing mitral cusp syndrome, myxomatous mitral valve, floppy
valve syndrome, and redundant cusp syndrome. It is a common but variable clinical syndrome that results
from a diverse pathologenic mechanisms of one or more portions of the mitral apparatus, the valve leaflets,
chordea tendineae, papillary muscle, and valve annulus. MVP usually associated with myxomatous
degeneration, affects up to 2 to 3% of adults in industrialized countries, with a 2:1 female predominance.
Myxomatous degeneration of the mitral valve is the most common cause of mitral regurgitation in the
United States.
Etiology
Most frequently non-classic mitral valve prolapse occurs as a primary condition unassociated with other
diseases. Patients present with a mid-systolic click or clicks, mild billowing of non-thickened mitral valve
leaflets), the mitral valve leaflet coaptation point on the ventricle side of the mitral annulus and no or
minimal mitral regurgitation.
However, classic mitral valve prolapse has been reported to be associated with many conditions. It is
characterized by increased redundancy or thickening (myxomatous changes) of varying portions of the
mitral valve leaflets. There is surface fibrosis of the mitral valve leaflets, mitral annular dilatation, chordal
redundancy and lengthening and fibrin deposits. MVP occurs quite commonly inheritable disorders of
connective tissue that increase the size of the mitral leaflets and apparatus, including the Marfan
syndrome, Ehlers-Danlos syndrome, osteogenesis imperfects, Ebstein's anomaly of the tricuspid valve,
atrial septa defect of the ostium secundum variety, and the Holt-Oram syndrome. Classic mitral valve
prolapse may be familial, non-familial. There appears to be a high incidence of MVP in patients with
asthenic habitus and a variety of congenital thoracic deformities, including a straight back, a pectus
excavatum and a shallow chest.
Secondary mitral valve prolapse can appear in coronary artery disease due to a relative displacement of the
ischemic papillary muscle.
Functional mitral valve prolapse results from a disproportion of the mitral valve leaflets and chordae in
relation to the internal left ventricular dimension. A reduction or alteration in left ventricular cavity size or
shape may cause normal mitral valve leaflets to move past the mitral valve annulus during ventricular
systole.
Pathology
The myxomatous appearance of the leaflets in MVP is due to a loss or dissolution of the normal dense
collagen fibers (fibrosa), with replacement and invasion of a less sturdy type of connective tissue
(spongiosa). The leaflets, chordae tendineae, and annulus all may be affected by myxomatous
proliferation. The leaflets are thickened and redundant, and the chordae tendineae become elongated.
Both mitral leaflets can be affected in MVP, but the posterior leaflet is more commonly involved.
Myxomatous proliferation, although most commonly affecting the mitral valve, is not limited to this valve but
has been described in the tricuspid, aortic, and pulmonic valves, particularly in patients with Marfan
syndrome, and may lead to regurgitation of these valves.
Prolapse represents abnormal superior systolic displacement of the mitral valve leaflets; one or both of the
leaflets extend beyond the normal systolic coaptation point (as seen in the below animation), allowing MR
to occur. During systole, individual scallops or an entire leaflet may billow excessively into the left atrium
(LA). For severe MR to be present, both leaflets must be affected or one leaflet may be flail, such as in the
case of a ruptured chordae tendinea. The stress on the ballooning leaflets during ejection may result in
additional stretching of the valve tissue and chordae. Thus, prolapse may beget greater prolapse.
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Mitral Valve Prolapse
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Signs and Symptoms
A large majority of patients with MVP are asymptomatic. In may cases, otherwise asymptomatic patients
with MVP suffer from undue anxiety, perhaps precipitated by their having been informed of the presence of
heart disease. But there are individuals with MVP that may have a variety of symptoms, such as
palpitations, chest discomfort, dyspnea, fatigability, syncope, pre-syncope. Rare cases of sudden death
have been reported, possibly caused by malignant ventricular dysrhythmias. A mitral valve syndrome has
been described that includes the following symptoms: palpitations (Holter often with arrhythmias); atypical
chest pain, dyspnea, and fatigue (without evidence of impaired exercise tolerance); neuropsychiatric
complaints (panic attacks); and transient ischemic attacks and strokes. Individuals with MVP have been
shown to have a wide variety of supraventricular and ventricular tachyarrhythmias, as well as
bradyarrhythmias.
Physical Examination
In adults, MVP is one of the few cardiac conditions in which the outward appearance may suggest the
diagnosis. Individuals with familial variety of prolapse often are red haired and fair skinned. Many patients
are thin or asthenic with long extremities. Some degree of pectus excavatum and, less commonly pectus
carinatum is common. Scoliosis and loss of the normal dorsal thoracic kyphosis frequently is observed. A
narrow anterior posterior chest diameter (straight back) may be present, MVP has been associated with
very small breasts in women (hypomastia) in addition to the thoracoskeletal abnormalities.
Heart Sounds:
Systolic Clicks
The most important auscultatory finding in MVP is a systolic click at least 0.14 sec after S1. The mitral
valve begins to prolapse when the reduction of left ventricular volume during systole reaches a critical point
at which the valve leaflets no longer coapt; at that instant, the click occurs and the murmur commences.
The clicks coincide with prolapse of a leaflet or scallop, after LV systolic size has decreased considerably,
Thus, the click normally is found in mid to late systole and not during early systole. Any maneuver that
decreases left ventricular volume, such as a reduction of impedance to left ventricular outflow, a reduction
in venous return, or an augmentation of contractility, results in an earlier occurrence of prolapse during
systole. As a consequence, the click and onset of the murmur move closer to S1. When very early
prolapse occurs, the click can move into S1. and a separate sound may not be audible; S1 will appear to be
increased in intensity. Whenever one hears a loud "S1" in conjunction with a holosystolic murmur, it
should suggest the diagnosis of holosystolic mitral leaflet prolapse.
During the straining phase of the Valsalva maneuver, upon sudden standing, and early during the
inhalation of amyl nitrate, cardiac size decreases, and both the click and the onset of the murmur occur
earlier in systole (increase the duration). In contrast, a sudden change from the standing to the supine
position, leg-raising, squatting, maximal isometric exercise, and to a lesser extent, expiration will delay the
click (decrease the duration) and the onset of the murmur.
Systolic murmurs
Mitral valve prolapse click can be associated with or without a mid to late systolic, crescendo or
crescendo-decrescendo medium to high-pitched murmur due to mitral regurgitation.
Laboratory Examination
ECG is usually normal in asymptomatic patients with typical auscultatory and echocardiographic findings.
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Mitral Valve Prolapse
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A spectrum of arrhythmias, including atrial and ventricular premature contractions and supraventricular and
ventricular tachyarrhythmias as well as bradyarrhythmias due to sinus node dysfunction or varying degrees
of atrio ventricular block, have been observed. The reason is not clear.
Chest X-ray may be normal but may also show thoracic abnormalities (e.g., straight back, kyphosis,
scoliosis, pectus excavatum, pectus carinatum). Cardiomegaly due to left atrial enlargement and left
ventricular enlargement suggests significant mitral regurgitation.
Echocardiography is usually the procedure of choice in assisting in the diagnosis of mitral valve prolapse.
Below shows a parasternal long axis view. This view is considered the "gold standard" view in the
diagnosis of MVP. The anterior and posterior mitral valve leaflets are seeing coapting past the mital
annular line.
Cardiac Catheterization
Left ventricular angiography may demonstrate an abnormality of the mitral leaflets but cardiac
catheterization is not used in the diagnosis of mitral valve prolapse.
Treatment
There really is no treatment for mitral valve prolapse, but the patient should be followed if a patient has
significant mitral regurgitation associated. Mitral valve repair/replacement may be indicated for the
significant mitral regurgitation.
Flailed Mitral Valve
Flailed mitral valve can be defined as a ruptured chordea/papillary muscle that will result in the
abnormal coaptation of the mitral valve.
Etiology
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Mitral Valve Prolapse
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Chordal rupture may be caused by a mitral valve prolapse or severe mitral regurgitation, papillary muscle
dysfunction from a myocardial infarct or endocarditis. Acute mitral valve rupture or chordal rupture is
uncommon; it usually is found in association with other significant cardiac injury. In the setting of mitral
valve injury, rupture of the papillary muscle is the most likely, followed by rupture of the chordea tendineae
and avulsion of the valve itself. Papillary muscle rupture may be complete, involving the whole belly of the
muscle, or partial, involving one or more apical heads. Early recognition of acute MR, regardless of the
cause, is crucial to patient survival.
Signs, Symptoms and Treatment
There would be an acute sudden onset of congestive heart failure and acute pulmonary edema due to the
sudden increase in volume in the left atrium during systole. Flailing usually is acute and the left atrium
does not have time to take defense against the sudden onset of blood volume and rise in pressure. The
edges of the valve leaflet slips completely and points towards the left atria during systole. Most likely one or
two ruptured chordae - tertiary chordial rupture may not result in severe MR, but primary chordial may
result in acute severe MR.
Acute MR is poorly tolerated and frequently results in profound clinical deterioration. When acute, MR
results in abrupt or rapid-onset volume overload of the left heart. the pre-existing size and compliance of
the left atrium are paramount in determining the resultant signs and symptoms. A large volume of
regurgitation into a normal, noncompliant atrium results in high left atrial pressures. The left ventricle does
not tolerate an acute volume load when compensatory mechanisms of dilation and hypertrophy do not have
time to develop; left ventricular diastolic and left atrial pressures increase markedly. The clinical course of
such patients may rapidly decline and result in death.
Patients may experience rest dyspnea, orthopnea, paroxysmal nochturnal dyspnea, chest discomfort,
pulmonary edema, or shock and may need surgery immediately by insertion of a Carpentier or Duran ring,
placation or valve replacement.
Mitral Annular Calcification
Mitral annular calcification (MAC) is found in the valve rings or fibroskeleton of the heart. It is a
degenerative process occurring with aging and is found most often in individuals above the age of 40 years
and especially women. It is one of the most common cardiac abnormalities found at autopsy. When the
calcification is limited to the posterior-medial portion of the annulus at the base of the posterior leaflet there
are usually no complications. When the calcification is more extensive it may involve the valve leaflets and
cause limitation of motion leading to regurgitation, when it is severe it may be an important cause for MR
or, occasionally, and obstructive gradient during diastole.
Etiology
The development of degenerative calcification of the mitral annulus is accelerated by systemic
hypertension, aortic stenosis, patients with chronic renal failure with secondary hyperparathyroidism and
diabetes, as well as by an intrinsic defect in the fibrous skeleton of the heart, such as Marfan and Hurler
syndromes. In these two conditions, the mitral annulus is not only calcified but is also dilated, further
contributing to MR. The annulus may also become thick, ridged, and calcified secondary to rheumatic
involvement; when this process is severe, it is also can interfere with valve closure.
Pathophysiology
The normal annulus measures 10 cm in circumference, it is soft and flexible during systole contraction of
surrounding left ventricular muscle causes annulus to constrict. This constriction contributes to mitral
valve closure.
When annular calcification is present, it may immobilize the basal portion of the mitral leaflets, preventing
their normal excursion in diastole and coaptation in systole and aggravating the MR that results from loss of
the normal sphincteric action of the mitral valve.
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Mitral Valve Prolapse
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Signs and Symptoms
Frequently patients with MAC have arrhythmias (atrial fibrillation and atrial premature beats). Tricuspid
annular calcification is rare but is associated with ASD's, right ventricular hypertrophy and pulmonic
stenosis.
Patients with MAC are twice as likely to have thromboembolic events.
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