Objectives: This study sought to identify risk factors for both late observed and late "excess" mortality after aortic valve replacement and to examine the causes of late mortality.
Background: Because operative mortality after aortic valve replacement is very low, the timing of surgical intervention should focus on maximizing long-term survival. However, to judge the effect of valve replacement on long-term survival in an elderly population, it is important to separate mortality resulting from extraneous causes (background mortality) from disease-related mortality (excess mortality). Background mortality can be estimated by calculating expected mortality on the basis of age and gender.
Methods: From 1966 to 1986, 643 patients (mean age 59.6 years, 138 [21%] > or = 70 years old) underwent aortic valve replacement, 129 of whom also underwent coronary bypass grafting; 594 patients survived > or = 30 days after the procedure. The overall 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. Multivariate analysis was performed for both observed and excess mortality.
Results: Risk factors for both observed and excess mortality were previous myocardial infarction, coronary artery disease, heart failure and atrial fibrillation. Although age > or = 70 years 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, including sudden death in 7% and cerebral vascular accidents in 7%. Congestive heart failure was an important cause of death (21%) irrespective of the time elapsed since aortic valve replacement. In patients with aortic regurgitation, congestive heart failure was the main cause of death (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 factor for late mortality after aortic valve replacement. Aortic regurgitation carries a high risk, probably associated with left ventricular dysfunction at the time of operation. Earlier operation may be warranted in such patients.