- Dyspnea or orthopnea.
- Characteristic apical systolic murmur.
- Color-flow Doppler echocardiographic evidence of systolic
regurgitation into the left atrium.
The mitral apparatus consists of the left ventricular walls that support the papillary muscles, the chordae tendineae, mitral leaflets,
annulus, and adjacent left atrial walls. Because defects in any
of these components can lead to systolic regurgitation, the list
of diseases that can cause mitral regurgitation includes many types
of heart disease. Anything that causes left ventricular dilatation
may disrupt the alignment of the papillary muscles, impairing their
function and dilating the annulus, resulting in mitral regurgitation.
Myocardial infarction involving the papillary muscles or the left
ventricular walls that support them can impair the function of the
mitral apparatus. Mitral chordae can rupture, especially in patients
with hypertension or mitral valve prolapse. The most common diseases affecting
the mitral leaflets are rheumatic heart disease and the myxomatous changes
of mitral valve prolapse. In addition, infectious endocarditis can
destroy the mitral leaflets, and mitral annular calcification can
impair the normal systolic contraction of the annulus, leading to mitral
regurgitation. Finally, left atrial dilatation from any cause can
disrupt annular function and cause mitral regurgitation. Some patients
have combinations of these defects, making mitral regurgitation
both more likely and more severe.
For clinical purposes, mitral regurgitation can be divided into two broad categories: organic and functional. The former refers
to diseases that involve the valve leaflets and their immediate
supporting apparatus, ie, chordae and annulus. The latter refers
to diseases that affect the left ventricle and atrium, leaving the
valve apparatus intact (Table 10–1).
Most clinical studies involve patients with organic mitral regurgitation,
so, unless otherwise specified, the following discussion focuses
on organic mitral regurgitation.
Table 10–1. Etiologic Classification of Mitral Regurgitation. |Favorite Table|Download (.pdf)
Table 10–1. Etiologic Classification of Mitral Regurgitation.
|Organic Mitral Regurgitation|
Myxomatous changes (mitral valve prolapse)
Rheumatic heart disease
Spontaneous chordal rupture
Collagen vascular disease
Trauma: penetrating and nonpenetrating
|Functional Mitral Regurgitation|
Among the many causes of chronic organic mitral regurgitation, mitral valve prolapse is a unique entity in many ways. An increase
in the middle connective tissue layer of the mitral valve causes
an increase in leaflet size and elongated chordae. The resultant
systolic prolapse of the valve into the left atrium may or may not
be accompanied by regurgitation. In some patients, regurgitation depends
on left ventricular volume. Large volumes tend to reduce prolapse and
hence regurgitation; small volumes have the opposite effect.
Consequently, the presence or absence of regurgitation and its severity and timing in systole (the ventricle becomes progressively
smaller during systole) are determined by a complex interplay of
left ventricular volume, pressure, and contractile state. Patients
with mitral valve prolapse are also unique because the condition
can be hereditary connective tissue disease (eg, Marfan syndrome) ...