Mitral regurgitation (MR) is the most common valvular heart disorder. 1 About 9% of the general population aged more than 75 years in the United States have MR. As the incidence of MR increases with age, the number of patients with MR who require intervention and inpatient care will only increase in the coming decades. 2 MR is divided into two categories: primary organic MR, which occurs as a result of an intrinsically abnormal mitral valve, and secondary or functional MR, which develops secondary to left ventricular (LV) dysfunction or annular dilatation prohibiting normal valve closure. 3,4 Differentiating between these phenotypes of severe MR by imaging modalities is critical to allow accurate diagnosis as well as guidance in choosing timing and type of intervention. 5 Untreated severe MR is associated with poor outcomes due to the adverse consequences of long-standing volume overload on the left ventricle. It can cause LV volume overload, which may lead to progressive dilatation of the left ventricle and left atrium, heart failure, and pulmonary hypertension. 5,6 Echocardiography and CMR play a complementary role in the diagnosis and understanding the mechanism of MR. They also help define prognosis along with the optimal treatment strategies for MR. 7,8 Decisions regarding surgical interventions, being mitral valve repair or replacement, rely on symptomatology as well as the regurgitation severity, LV ejection fraction (LVEF), and LV end-systolic diameter (LVESD). 9,10 The role of imaging is hence as follows: to identify the etiology of the MR; to quantify the severity of the regurgitation; to assess the response of the left ventricle to the volume overload; and to determine the feasibility of durable repair. 4,5,7,8 Transthoracic echocardiography (TTE) remains the first-line modality per the American Society of Echocardiography(ASE)/American College of Cardiology (ACC)/American Heart Association(AHA) guidelines. The quantitative methods for assessment of MR severity via TTE involve the assessment of several independent data points as indicated in the ASE guidelines which includes flow convergence-based effective regurgitant orifice area (EROA) and regurgitant volume, pulse Doppler-based regurgitant volume, and the vena contracta. 4,11-14 Many assumptions underlie the assessment of MR by echocardiography, and hence, this assessment has limitations which arise from mitral regurgitation characteristics such as temporal change in orifice geometry, the possibility of multiple jets, the
