No intervention is applied.

There would be echo records of subjectes of the study during follow-up. So for subjects with baseline none or mild valvular heart diseases, including mitral regurgitation, aortic regurgitation, and tricuspid regurgitation, there might be some with progression to moderate or severe valvular heart diseases, and some other without this progression. The primary outcome of the study would be the progression of valvular heart diseases from none or mild to moderateor severe, as assessed by echocardiography.