- 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.
| Save Table
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)
or acquired (inflammation of the valve). Some patients exhibit abnormalities
of connective tissue in other organs (eg, thoracic skeleton) and
have demonstrable abnormalities in the autonomic nervous system.
Thus, the clinical presentation of mitral valve prolapse varies
from one that is similar to other forms of mitral regurgitation
to a unique presentation that is dominated by extracardiac manifestations.
In chronic mitral regurgitation, the more common of the two general clinical presentations, the mitral regurgitation
progressively worsens as the underlying heart disease worsens. In
this situation, the heart has time to adapt to the mitral leak.
The increased pressure in the left atrium during systole causes
left atrial dilatation. If this is not adequate to decompress the
left atrial pressure, the pulmonary arterial tone increases to protect
the pulmonary capillaries from increased hydrostatic pressure, resulting in
pulmonary hypertension. Because the regurgitated blood returns to the left ventricle
in diastole, along with the normal atrial stroke volume, the volume
load on the left ventricle results in left ventricular dilatation and
Initially, the loading conditions in mitral regurgitation enhance left ventricular performance because preload is increased and afterload
is normal. Preload is increased by the augmentation of left ventricular
diastolic volume, which increases left ventricular systolic function via
the Frank-Starling mechanism. Afterload, or the left ventricular
wall tension after the aortic valve opens in systole, is not increased,
despite increased left ventricular volume, because much of the increased
volume is regurgitated into the left atrium in early systole before
the aortic valve opens and because the continued regurgitation during
systole reduces forward stroke volume and blood pressure. As the
severity of mitral regurgitation increases over time, the ability
of the dilated left ventricle to augment systolic function reaches
its limits, left ventricular systolic function falls, and heart
Acute mitral regurgitation presents differently because there is insufficient time for these compensatory mechanisms
to develop. Sudden rupture of the chordae tendineae, for example, may
result in severe acute mitral regurgitation, which markedly increases
left atrial pressure. Because the left atrium has no time to dilate,
the pulmonary capillary pressure rises markedly, and pulmonary edema
usually ensues. The left ventricle also does not dilate adequately to
handle the tremendous volume load, and forward failure occurs because
of an impaired left ventricular stroke volume. Acute mitral regurgitation
(caused by the abrupt failure of a component of the mitral apparatus)
can precipitate or aggravate symptoms in a patient with chronic
Nesta F et al. New locus for autosomal dominant
mitral valve prolapse on chromosome 13: clinical insights from genetic
studies. Circulation. 2005 Sep 27;112(13):2022–30.
Chronic Mitral Regurgitation
The medical history of patients with chronic mitral regurgitation may suggest its cause. Look for a possible history of acute rheumatic
fever, coronary artery disease, or a cardiomyopathy. The most common
symptom in patients with chronic mitral ...