<qa>  What is the most common valvular disease in the western world?Aortic valve stenosis AVS is the most common valvular disease in the western world. The prevalence increases with age where degenerative changes of the aortic valve with thickening, accumulation of calcium and progressive dysfunction of the valve usually becomes apparent in patients older than 60 years. Although the development of AVS generally is believed to be a degenerative process more recent studies have demonstrated AVS is caused by a complex process of increased cellularity, lipid accumulation, extracellular matrix deposition, and with disease progression calcification of lesions. Although mild and moderate AVS generally is well tolerated severe AVS is associated with considerable morbidity and mortality, and valve replacement is generally required. 