Valve replacement for aortic stenosis: the curative potential of early operation.
Concentric hypertrophy of the left ventricular wall is the primary consequence of acquired aortic stenosis (AS). Reduced left ventricular (systolic) function usually returns to normal after aortic valve replacement (AVR) in AS. Afterload mismatch prior to AVR, and not reduced contractility, is thought to be the explanation. Together with "the prosthetic valve disease" the afterload mismatch theory is used conceptually to postpone AVR until severe symptoms prevail. However, latent or manifest myocardial ischaemia/hypoxia is a central abnormality in concentric hypertrophy, also in the absence of coronary artery disease (CAD); impaired left ventricular diastolic function due to both reduced (active) relaxation and passive qualities of hypertrophied muscle is the primary cause of congestive failure symptoms. Reduced systolic function (ejection fraction) develops in succession, and dilation of the ventricle is an end-stage phenomenon. With the present timing of operative intervention significant late excess mortality from congestive heart failure is the rule after AVR in AS. Early functional improvement is probably related to reduced myocardial oxygen demand associated with afterload reduction caused by AVR, irrespective of irreversible myocardial disease. Employing a 22-year surgical series, multivariate predictive models were made for the following effect measures of AVR: early mortality, long term survival, prosthesis related complications, sudden heart related events, recurrence of congestive heart failure, heart pathology at autopsy, and left ventricular systolic and diastolic function 12 years after AVR. A prognostic index was calculated for each patient from variables related to pre-AVR degree of heart disease. A low prognostic index corresponding to operative intervention early in the course of AS predicted an operative mortality approaching zero, a normal sex and age specific long term survival, a normal rate of the quantitatively most important prosthesis related complications, a normal rate of heart related events, complete symptom freedom early after the operation without late return of congestive heart failure, and normal left ventricular function late after the operation. Complete regression of left ventricular hypertrophy was a dominant underlying mechanism. Imparied diastolic function of the left ventricle at late reinvestigation, being related to significant residual hypertrophy, was the sole predictor of fatal congestive heart failure irrespective of (a usually normal) ejection fraction. A policy of consistent coronary artery bypass grafting concomitant with AVR in case of CAD reduced early mortality rate in such patients, including the elderly, to the (low) level of those without CAD. A normal survival can, however, not be anticipated in AS patients with concomitant CAD.(ABSTRACT TRUNCATED AT 400 WORDS)
Lund
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Department of Cardiac Surgery, Harefield Hospital, Middlesex, England.
D000293:Adolescent; D000328:Adult; D001021:Aortic Valve / Q000601:surgery; D001024:Aortic Valve Stenosis / Q000401:mortality / Q000601:surgery*; D005260:Female; D006350:Heart Valve Prosthesis / Q000401:mortality; D006801:Humans; D008297:Male; D008722:Methods; D008875:Middle Aged; D011183:Postoperative Complications; D011379:Prognosis; D012189:Retrospective Studies