<qa>  What is the most common cause of adult valvular heart disease?Aortic stenosis remains the most common cause of adult valvular heart disease, the prevalence increasing with age. Average survival of patients treated conservatively has historically been reported as 25 years from the onset of symptoms. More recent studies have confirmed the dismal prognosis of severe aortic stenosis. Advanced age, reduced left-ventricular ejection fraction, congestive heart fail-ure and renal insufficiency appear to be independent predictors of reduced survival. Asymptomatic patients with very severe aortic stenosis also share a poor prognosis with a high event rate and a risk of rapid functional deterioration. Early surgery offers a therapeutic option to improve clinical outcomes via decreasing cardiac mortality and improving symptoms. 