ANALYSIS OF RISK-FACTORS FOR EXCESS MORTALITY AFTER AORTIC-VALVE REPLACEMENT

Objectives. This study sought to identify risk factors for both late o bserved and late ''excess'' mortality after aortic valve replacement a nd to examine the causes of late mortality. Background. Because operat ive mortality after aortic valve replacement is very low, the timing o f surgical intervention should focus on maximizing long-term survival. However, to judge the effect of valve replacement on long-term surviv al in an elderly population, it is important to separate mortality res ulting from extraneous causes (Background mortality) from disease rela ted mortality (excess mortality). Background mortality can be estimate d by calculating expected mortality on the basis of age and gender. Me thods. From 1966 to 1986, 643 patients (mean age 59.6 gears, 138 [21%] greater than or equal to 70 years old) underwent aortic valve replace ment, 129 of whom also underwent coronary bypass grafting; 594 patient s survived greater than or equal to 30 days after the procedure. The o verall operative mortality rate for isolated aortic valve replacement decreased over time from 25.5% (1966 to 1972) to 2.6% (1980 to 1986). Cumulative total follow-up after discharge was 3,603 patient-years. Mu ltivariate analysis was performed for both observed and excess mortali ty. Results. Risk factors for both observed and excess mortality were previous myocardial infarction, coronary artery disease, heart failure and atrial fibrillation. Although age greater than or equal to 70 yea rs was a risk factor for observed mortality (hazard rate ratio [HRR] 2 .4, 95% confidence interval [CI] 1.6 to 3.7), it was not a risk factor for excess mortality. In contrast, isolated aortic regurgitation was an important risk factor for excess mortality only (HRR 3.8, 95% CI 1. 3 to 11.2). Late mortality was valve related in 22% of patients, inclu ding sudden death in 7% and cerebral vascular accidents in 7%. Congest ive heart failure was an important cause of death (21%) irrespective o f the time elapsed since aortic valve replacement, In patients with ao rtic regurgitation, congestive heart failure was the main cause of dea th (38%); in patients with aortic regurgitation and preoperative heart failure or severe left ventricular dysfunction, heart failure was the cause of death in 44% and 63%, respectively. Conclusions. Analysis of excess mortality revealed that older age in itself is not a risk fact or for late mortality after aortic valve replacement. Aortic regurgita tion carries a high risk, probably associated with left ventricular dy sfunction at the time of operation. Earlier operation may be warranted in such patients.