DEFINITION/DIAGNOSIS
A valvular cardiomyopathy occurs when a valvular abnormality is present and myocardial systolic function is depressed out of proportion to the increase in wall stress. This most commonly occurs with left-sided regurgitant lesions (mitral regurgitation and aortic regurgitation), less commonly occurs with aortic stenosis, and never occurs as a consequence of pure mitral stenosis.
DISTINCT PATHOPYSIOLOGY
The classic explanation for the typical phenotypes observed in valvular cardiomyopathies relates to exposure to different types of wall stress.”‘ Within this construct, the pattern of eccentric hypertrophy derives from increased diastolic wall stress.Thus long-standing mitral regurgitation most commonly results in compensated eccentric hypertrophy that can progress to a dilated failing phenotype. Aortic regurgitation is a particularly poorly tolerated hemodynamic insult because wall stress is increased in both systole and diastole, and when decompensation occurs, ventricular volume will be increased with or without increased wall thickness. Aortic stenosis classically results in compensated concentric hypertrophy, but when decompensation occurs, a variety of phenotypes can be observed that are similar to hypertensive cardiomyopathies. A disturbing and fairly commonly observed phenomenon is the development of a dilated cardiomyopathy after surgical correction of mitral and sometimes aortic valve disease in subjects who preoperatively had only mild LV dysfunction. These cases are likely due to the superimposition of myocardial damage resulting from open heart surgery and/or underlying dysfunction that was likely greater than appreciated preoperatively.
PROGNOSIS
The prognosis is variable and depends on the number of associated conditions, the nature and extent of the valvular abnormality, and most important, the severity of the cardiomyopathy at the time of surgical correction (see below). In general, severely depressed myocardial function will not improve much with surgical repair of aortic regurgitation or mitral regurgitation, but the prognosis is likely to be improved because of elimination of some of the hemodynamic insult. Replacement of the mitral valve should not be attempted in the majority of subjects with severe mitral regurgitation and LV ejection fractions less than 25 percent because of prohibitively high operative/perioperative mortality rates. On the other hand, there is no impairment of LV systolic function severe enough to preclude valve replacement of severe aortic stenosis, since function invariably will improve on relief of the hemodynamic insult, and the prognosis is relatively good.
