Valvular Heart Disease
The four cardiac valves consist of either cusps or leaflets that close to prevent the blood from flowing backwards. When pressure behind the valve builds up, the valve opens, after blood has passed through, the pressure is reduced and the valve closes, actively or passively.
Rheumatic valve disease used to be the most prevalent etiology of valvular cardiac diseases worldwide. In developing countries, rheumatic heart disease remains the most common cause of valvular heart disease. Over the past 60 years, the etiology of most valvular heart disease in industrialized countries shifted towards degenerative etiologies, mainly because of a decrease in acute rheumatic fever. However cardiac valve diseases remain common in industrialized countries, mainly because the decrease in rheumatic valve disease is compensated by an increase in degenerative valve disease, with an important contributing fact being the aging population of industrialized countries. This shift in pathologic etiology accounts for differences in patient characteristics and distribution of type of valvular lesions. 
In the US population, the national prevalence of moderate and severe valve disease was estimated at 2,5%, determined by echocardiography. In another cohort, prevalence based on clinical signs and symptoms, confirmed by echocardiographic imaging, the estimated prevalence of at least moderate valvular diseas was estimated at 1,8%. This difference indicates the under diagnosing of valvular heart disease, and illustrates the fact that diagnosis on the basis of clinical information alone is not reliable. . Prevalence did not change according to gender, but increased substantially with advancing age, with 13,2 % after the age of 75 years, versus <2% prior to 65 years old. The predominance of degenerative etiologies accounts for the higher prevalence in the elderly. Moreover, the prevalence of degenerative valve disease is expected to rise with the aging population of Western countries.
Mitral regurgitation was found to be the most frequent valvular disease, with a prevalence of 1,7 %, followed by aortic regurgitation (0,5%), aortic stenosis (0,4%) and mitral stenosis (0,1%). Mean age of patients presenting to the hospital in the Euro heart survey was 65 years . In this survey, 63% of all cases of native valve disease were of degenerative etiology. Aortic stenosis was found to be the most frequent valvular disease of patients referred for treatment. In 22% of all patients etiology was rheumatic heart disease.
In developing countries, approximately 30 milion cases of rheumatic fever occur annually, in general before the age of 20. . Approximately 60% of patients will develop rheumatic heart disease, which becomes clinically evident 1 to 3 decades later . Rheumatic heart disease remains the most common cause of valvular heart disease in third world countries. In western countries, rheumatic heart disease is the second most common cause of valvular heart disease.