Aims The aim of the present study was to identify risk markers for the development of valvular aortic stenosis (AS). Lipoprotein(a) (Lp(a)) and Chlamydia pneumoniae IgG antibody titres in plasma and in circulating immune complexes as well as leptin and tissue plasminogen activator (t-PA) in plasma were studied.

Methods and Results One hundred and one patients (41 women and 60 men, mean age 71±8 years) with significant AS and 101 age- and sex-matched controls were included in this study. All patients underwent aortic valve replacement at the University Hospital in Umeå, Sweden. The controls had no symptoms of cardiovascular disease and they were examined echocardiographically. An Lp(a) level ≥480 mg.l⁻¹, a C. pneumoniae-specific IgG titre ≥1/128, a high leptin level and a high t-PA mass concentration in plasma were identified as risk markers for AS. A strong synergism between Lp(a) and C. pneumoniae IgG antibodies in circulating immune complexes was found.

Conclusion Our data indicate that a chronic C. pneumoniae infection and a high plasma Lp(a) level might influence and aggravate aortic heart valve sclerosis via the formation of circulating immune complexes. The present study also strongly suggests an association between high plasma leptin, t-PA mass concentration and AS.