The Epidemiology of Valvular Aortic Stenosis. Prevalence, incidence, mortality, risk factors and progression of aortic stenosis in a general population. The Tromsø Study.

Abstract

With datasets from 3 repeated echocardiographic examinations (1994, 2001 and 2008) of a random sample of initially 3,273 participants in the Tromsø Study, we were able to give descriptive and analytical epidemiologic data on degenerative aortic valve disease. Aortic valve stenosis (AS) was defined as a mean aortic valve gradient ≥15 mmHg. There were 164 subjects with AS. We found that prevalence consistently increased with age, average values being 0.2% in the 50-59 year cohort, 1.3% in the 60-69 year cohort, 3.9% in the 70-79 year cohort and 9.8% in the 80-89 year cohort. The incidence rate of AS was 4.9‰/year. The mean annual increase in mean transvalvular pressure gradient was 3.2 mmHg. The increase was lower in mild AS than in more severe disease, disclosing a non-linear development of the gradient, but with large individual variations. Mortality was not significantly increased in the asymptomatic AS-group (HR=1.28), nor in those who received aortic valve replacement (n=34, HR= 0.93), compared with the general population. 132 participants were diagnosed with incident AS. Cox proportional hazards regression disclosed age (HR 1.11, 95%CI 1.08 to 1.14), systolic blood pressure (HR 1.01, 95%CI 1.00 to 1.02), active smoking (HR 1.71, 95%CI 1.09 to 2.67), and waist circumference (HR 1.02, 95%CI 1.00 to 1.03) as independent predictors of incident AS. Analysis of risk factors for progression of AS disclosed a higher mean aortic gradient at first measurement (p=0.015), weight (p=0.015), a low Hgb (p=0.030) and HDL (p=0.032) as significant independent predictors. From this study AS appears to constitute a distinctive age related degenerative and inflammatory disease, which may be aggravated by smoking and a number of factors increasing the mechanical stress on the aortic valve. Two repeated echocardiographic examinations were performed on 1,884 participants in the last 7 year span (2001-2008). Those with a subclinical aortic valve gradient <15 mmHg were stratified into 3 groups: <5 mmHg, 5-9.9 mmHg and 10-14.9 mmHg. At baseline 73 participants had gradients from 10-14.9 mmHg, of whom 33.3 % developed AS during follow up. In contrast, AS developed in only 3.7 % of those with a baseline gradient of 5-9.9 mmHg and in 0.3% of those with a gradient < 5 mmHg. The results support a regular follow up of patients with a mean aortic valve gradient of 10 -15 mmHg.