Added Value of Cardiovascular Magnetic Resonance in Primary Mitral Regurgitation

Resonance in Primary Mitral RegurgitationArticle, see p 1349 D egenerative (or primary) mitral regurgitation (MR) is the most prevalent valvular heart disease, with an estimated prevalence of 2% of the general population. 1 The most frequent form of degenerative MR is mitral valve prolapse caused by elongation or rupture of tendinous chords.Factors considered in the clinical decision making of patients with mitral valve prolapse include the impact of MR severity on symptoms, left ventricular (LV) dimensions and function, left atrial dilation, the presence of atrial fibrillation and pulmonary hypertension, and the possibility of performing a durable mitral valve repair. 2 Transthoracic echocardiography and transesophageal echocardiography remain the most common methods to evaluate the severity and mechanism of MR, LV dimensions and function, left atrial volume, and presence of pulmonary hypertension.Over the past 15 years, cardiovascular magnetic resonance (CMR) has gained acceptance for the assessment of patients with MR, providing information on MR severity and accurate measurements of LV or left atrial dimensions and function.However, echocardiography and CMR differ in the manner in which they quantify the severity of MR.Echocardiographic determinations of the severity of MR rely on color Doppler visualization of the regurgitant jet area, estimation of the regurgitant volume by subtracting the forward flow across the aortic valve from that occurring across the mitral valve, quantification of pulmonary vein flow profiles, or measurement of the mitral valve regurgitant orifice area, regurgitant volume, and regurgitant fraction with the proximal isovelocity surface area (PISA).3 The PISA method is based on identification of differences in regurgitant blood flow velocity that accelerates through the regurgitant orifice.However, the PISA method is less accurate in eccentric regurgitant jets and noncircular orifices or when the blood flow across the leaking valve is not holosystolic.In addition, the PISA method cannot be applied when multiple regurgitant jets are present.Miscalculation of the effective regurgitant orifice area of 10% to 25% by the PISA method has been reported among expert observers.4 Direct planimetry of the regurgitant orifice area with 3-dimensional echocardiographic techniques has improved the accuracy of quantifying the regurgitant volume and has shown better agreement with CMR.5,6 CMR techniques quantify the severity of MR through direct measurement of the mitral regurgitant volume and fraction using phase-contrast techniques.Mitral regurgitant volume and regurgitant fraction can be quantified with phase-contrast methods.The first method subtracts the aortic forward stroke volume from the LV stroke volume obtained by planimetry of LV short-axis cine images.It is important to note that this methodology is not applicable when aortic regurgitation coexists.The second method uses the phase-contrast method in isolation and directly measures the mitral regurgitant flow at the mitral valve.CMR flow measurements have