Mitral regurgitation
Pathophysiology of mitral regurgitation
Incompetence of the mitral valve with regurgitation of blood from the left ventricle (LV) into the left atrium (LA) during systole is common (Figure 150-1). Although MR has a number of different causes, in most cases, MR occurs as a result of senescence of the mitral leaflets, and its prevalence increases with age. Degenerative MR is second only to calcific aortic stenosis as the most common valvular cardiac disorder in high-income countries. Mitral valve incompetence usually develops over many years, but incompetence of the valve can develop acutely for reasons other than degenerative disease (e.g., rupture of chordae tendineae from ischemic heart disease). Furthermore, acute MR can superimpose on chronic mitral insufficiency. Barlow disease of the mitral valve is another common condition resulting in MR, characterized by myxoid degeneration of the leaflets leading to thickened and redundant leaflets, mitral annular dilation, and chordal elongation.
Acute MR is usually quite symptomatic (Figure 150-2) and requires surgical intervention. However, the management of chronic regurgitation of the mitral valve is controversial; patients who are symptomatic or who have a decreased ejection fraction are at increased risk of developing complications and are usually considered candidates for surgery. Surgical repair or replacement of the valve not only relieves symptoms, but has increasingly been shown to improve long-term outcome, with reductions in morbidity and mortality rates. Patients who have MR and who have a decreased ejection fraction, an increased LV end-diastolic volume (LVEDV; i.e., dilated LV), chronic atrial fibrillation, or pulmonary hypertension have better long-term outcomes when the valve incompetence is surgically corrected earlier in the course of the disease. Increasing evidence indicates that life expectancy is improved in patients with MR who have surgery before the previously mentioned morbidities develop. Fortunately, the success of valve repair (compared with replacement) and the low morbidity and mortality rates associated with surgical intervention favor early elective surgery. In an effort to prevent progression to worsening disease and subsequent increase in morbidity and mortality rates, current efforts focus on identifying patients with asymptomatic mitral valve disease whose long-term outcome may be favorably impacted if their MR is corrected at an early stage.
