Afterload mismatch in aortic and XXXX : implications for surgical therapy.

@entity1 @entity296 @entity339 @entity64 @entity67 @entity1184 @entity472 @entity337 @entity299 @entity340 @entity1002
In the management of @entity1 with @entity340 , an understanding of the effects of altered loading conditions on the left ventricle is important in reaching a proper decision concerning the timing of corrective operation. In acquired @entity340 , @entity1184 generally maintains left ventricular chamber size and ejection fraction within normal limits, but in late stage disease function can deteriorate as preload reserve is lost and @entity472 progresses. In this setting, even when the ejection fraction is markedly reduced (less than 25%), it can improve to normal after aortic valve replacement, suggesting that afterload mismatch rather than irreversibly depressed myocardial contractility was responsible for @entity1002 . Therefore, @entity1 with severe @entity472 and symptoms should not be denied operation because of @entity299 . In chronic severe aortic and @entity339 , operation is generally recommended when symptoms are present, but whether to recommend operation to prevent irreversible @entity296 in @entity1 with few or no symptoms has remained controversial. In @entity337 , left ventricular function generally improves postoperatively, even if it is moderately impaired preoperatively, indicating correction of afterload mismatch. Most such @entity1 can be carefully followed by echocardiography. However, in some @entity1 , severe left @entity67 fails to improve postoperatively. Therefore, when echocardiographic studies in the @entity1 with severe @entity337 show an ejection fraction of less than 40% (fractional shortening less than 25%) plus enlarging left ventricular end-diastolic diameter (approaching 38 mm/m2 body surface area) and end-systolic diameter (approaching 50 mm or 26 mm/m2), confirmation of these findings by cardiac catheterization and consideration of operation are advisable even in @entity1 with minimal symptoms. In chronic @entity339 , maintenance of a normal ejection fraction can mask depressed myocardial contractility. Pre- and postoperative studies in such @entity1 have shown a poor clinical result after mitral valve replacement, associated with a sharp decrease in the ejection fraction after operation. This response appears to reflect unmasking of decreased myocardial contractility by mitral valve replacement, with ejection of the total @entity64 volume into the high impedance of the aorta (afterload mismatch produced by operation).(ABSTRACT TRUNCATED AT 400 WORDS)
