Page 739 - Cardiac Nursing

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C HAPTER 2 9 / Acquired Valvular Heart Disease 715
fully monitored, however, and referred for mitral valve repair or
replacement before significant left ventricular dysfunction or pul- MITRAL VALVE PROLAPSE
monary hypertension occurs.
Cause
Surgical Management Mitral valve prolapse (MVP) refers to a variable clinical syndrome
Two surgical approaches are used to treat mitral regurgitation. Mi- that is the result of a variety of pathologic mechanisms of one or
10
tral valve repair uses reconstructive techniques as well as a rigid more portions of the mitral valve leaflets and apparatus. During
prosthetic ring to repair the mitral valve apparatus, thus sparing ventricular systole, one or both of the mitralleaflets prolapse above
the valve and avoiding the consequences of valve replacement. Mi- the plane of the mitral valve annulus. MVP syndrome may also be
tral valve replacement involves implantation of a prosthetic valve, known as Barlow syndrome, myxomatous valve syndrome, or click-
either mechanical or bioprosthetic. The mitral valve apparatus is murmur syndrome. The most common cause of MVP is myxoma-
preserved whenever possible as it contributes to the preservation tous degeneration, but it is also causedby Marfan syndrome,
of left ventricular function (Fig. 29-6). In patients with chronic Ehlers–Danlos syndrome, rheumatic heart disease, and ischemic
mitral regurgitation, mitral replacement should occur before the papillary muscle dysfunction. MVP occurs twice as frequently in
patient has had irreversible left ventricular dysfunction. Mitral women as men but serious mitral regurgitation with MVP occurs
10
valve replacement or repair can preserve left ventricular function more frequently in men older than 50 years. MVP can be either
and ejection fraction. Patients with NYHA class II symptoms nonfamilial or familial, transmitted as an autosomal trait.
should be considered for surgery.
In most patients, mitral valve repair may be undertaken for pa- Pathology
tients with mitral insufficiency as an alternative to replacement. Sur-
gical techniques involve reconstructing the leaflets and annulus in Patients with MVP have redundant myxomatous tissue with ex-
such a way as to narrow the orifice. These procedures consist of di- cess deposits of proteoglycans in the middle or spongiosa layer of
rect suture of the valve cusps, repair of the elongated or ruptured the valve. Histologically, collagen fragmentation and disorganiza-
chordae tendineae (chordoplasty), or repair of the valve annulus (an- tion as well as elastic fiber are present. Acid mucopolysaccharide
nuloplasty). With an annuloplasty, the incompetent valve is remod- material accumulates in the valve leaflets. The mitral valve leaflets,
eled using a ring prosthesis that is attached to the leaflets and the an- annulus, and chordae tendineae may also demonstrate disrupted
nulus. Mitral valve repair has demonstrated excellent short-term and collagen structure and extensive myxomatous change. While myx-
long-term results with low perioperative mortality rate (not 2% in omatous changes occur most commonly in the mitral valve, they
most reported series). In patients with acute mitral regurgitation sec- can also occur in the other cardiac valves.
ondary to myocardial infarction, coronary angiography should be
performed to define coronary anatomy for concomitant coronary Pathophysiology
bypass surgery at the time of mitral valve repair or replacement.
Enlargement of the valve leaflets related to myxomatous degener-
ation causes systolic prolapse of one or both leaflets into the left
atrium. Patients with MVP may have mitral regurgitation ranging
in severity from none to severe. Persistent billowing of the valve
causes stress to the underlying chordae and papillary muscles. Pro-
gressive mitral valvular degeneration can result in increasingly se-
vere mitral regurgitation. If chordal rupture occurs, severe mitral
regurgitation develops.
Supraventricular tachycardias (i.e., premature atrial contrac-
tions and paroxysmal supraventricular tachycardias) and ventricu-
lar arrhythmias may occur in patients with MVP. Although some
patients with MVP have had sudden cardiac death, it is unclear
what role MVP has in the cause. Patients with MVP may also
have autonomic nervous system dysfunction; specifically, mid-
brain control of adrenergic and vagal responses may be abnormal.
Clinical Manifestations
Most patients with MVP are asymptomatic. Patients may have
sharp, localized chest pain that is usually brief in duration. Pa-
tients may have equivocal symptoms of anxiety, fatigue, palpita-
tions, chest pain, and orthostatic hypotension. The chest pain that
occurs with MVP is often atypical and may be related to abnor-
mal tension on papillary muscles. 10 As mitral regurgitation pro-
■ Figure 29-6 Valve replacement with chordal preservation. (From gresses, patients may note increasing dyspnea, fatigue, decreased
Chitwood, W. R. [1998]. Mitral valve repair: Ischemic. In L. R. exercise tolerance, orthopnea, and paroxysmal nocturnal dyspnea.
Kaiser, I. L. Kron, & T. L. Spray [Eds.], Mastery of cardiothoracic sur- Ruptured chordae with leaflet flail and acute mitral regurgitation
gery [p. 321]. Philadelphia: Lippincott-Raven.) result in symptoms of severe left ventricular failure.