Methods Study population: Between August 2010 and July 2012, this study will enroll 100 severe MR patients who will receive cardiac catheterization for pre-operation evaluation. Exclusion criteria are the following: 1) presence of mitral stenosis, 2) more than mild severity of aortic valvular problem, 3) any abnormality of atrial septum (e.g., atrial septal defect or aneurysm), and 4) rhythm other than sinus rhythm. MR are categorized by mapping jet expansion in the LA in 4- and 2-chamber views at end systole from three separate cardiac cycles. MR is considered severe when regurgitant jet area occupies more than 40% of the LA area. The grade of MR is increased by one degree (moderate to severe) in cases of eccentric MR jet based on evidence of reduced color-flow jet areas due to loss of momentum in jets adjacent to chamber walls. Significant coronary lesion is defined as diameter stenosis > 70% in at least one major coronary artery. The control group consisted of 50 other comorbid disease-, age- and gender-matched patients with negative results of coronary angiography, despite positive result of screen test for coronary artery disease (treadmill, Thallium scan, stress echocardiography, or 64-slides CT angiography), and they are selected after confirming no evidence of valvular heart disease by echocardiography. All patients and controls will give written informed consent to participate in the study, and the study is approved by the institutional review board.