Functional MR is an important complication, which adversely affects the prognosis of patients with ischemic heart disease or global LV dysfunction. Two-dimensional Doppler echocardiography is a noninvasive and useful method for the diagnosis of functional MR. However, the pathophysiology of functional MR is not yet established, therefore, extensive investigations are necessary to understand its basic mechanism and establish effective and practical method for the prevention and treatment of functional MR.