PATHOPHYSIOLOGY AND NATURAL-HISTORY OF ACQUIRED VALVE DISEASE

The pathophysiology and natural history of valvular disease are important considerations in planning patient management. The decline in the incidence of rheumatic fever has been accompanied by a parallel decline in the number of cases of mitral stenosis. In general, correction of mitral stenosis can await the onset of symptoms. Patients with concomitant moderately severe aortic regurgitation should have surgical correction of the mitral stenosis together with aortic valve replacement, because of the high mortality associated with this combined valvular disorder after mitral surgery alone. One reason for this high mortality is the reduced ability of the left ventricle to handle a volume load after correction of mitral stenosis. Although surgical correction of mitral regurgitation should be considered when there is a decrease in left ventricular ejection fraction or an increase in end-systolic volume, recent evidence suggests that pulmonary hypertension and right ventricular dysfunction are also predictive of a poor prognosis. Currently, aortic valve replacement in aortic stenosis is recommended when patients become symptomatic, but new data suggest that severe aortic stenosis (valve area index < 0.5 cm2/m2) may be an indication even in the absence of symptoms. A large experience with patients with chronic aortic regurgitation suggests that valve replacement should be considered when end-systolic left ventricular dimension is 50 mm or greater by M-mode echocardiography or if ejection fraction falls on serial measurements, even if symptoms are absent. These new insights will help clinicians with the difficult task of selecting appropriate treatment for patients with mitral and aortic valve disease.