This document contains clinical expert consensus recommendations to guide the approach to patients with mitral regurgitation (MR); and emphasizes clinical and echocardiographic assessment, establishment of etiology and mechanism, consideration of associated hemodynamic consequences, recognition of indications for surgical evaluation, appreciation of the graded complexity of mitral valve repair as a function of pathoanatomy, and understanding of the currently limited role for transcatheter mitral valve edge-to-edge repair in the United States. Recommendations are based on the 2014 American Heart Association (AHA)/American College of Cardiology (ACC) Guideline for the Management of Patients With Valvular Heart Disease and its 2017 focused update. Key points:

1. Key steps in the management of patients with MR include identification of MR, definition of the etiology of MR (including whether MR is primary or secondary) and the Carpentier classification of leaflet motion, assessment of MR severity, treatment decisions that begin with the Heart Valve Team, and follow-up with clinical cardiology and the primary care provider.
2. Evaluation of the patient with MR begins with a directed history and physical examination. The clinician should recognize that symptoms may be subtle, owing to insidious progression and self-limitation of physical activity. Exercise testing can be useful for assessment of functional status and elicitation of symptoms; and exercise echocardiography may reveal elevated pulmonary artery pressures, worsening of MR, or blunted left ventricular (LV) or right ventricular contractile reserve.
3. The mechanism and etiology of MR should be determined, usually with transthoracic echocardiography (TTE), or, if image quality is poor, with transesophageal echocardiography (TEE). In addition to assessment of the mitral apparatus, careful measurement of left atrial (LA) volume and LV diameter and volume should be performed.
4. Primary MR (due to abnormalities of the mitral leaflets or subvalvular apparatus) should be distinguished from secondary MR (due to LA or LV geometric changes with a functionally normal mitral valve). In addition to LV dilation or regional or global abnormalities of LV systolic function, secondary MR also can be caused by pure LA and mitral annular dilation (termed atrial functional MR).
5. After characterization of leaflet morphology, leaflet motion should be described using Carpentier’s classification system: type I (normal leaflet motion); type II (excessive leaflet motion); and type III (restricted leaflet motion), subcategorized as type IIIA (restricted during both systole and diastole) and type IIIB (restricted only during systole).
6. The assessment of MR severity should begin with color-flow Doppler assessment, but also should include quantitative parameters including effective regurgitant orifice area, regurgitant volume, and regurgitant fraction. A comprehensive approach is recommended, in which multiple parameters are evaluated and integrated to form a final determination of MR severity. Additional testing including TEE and cardiac magnetic resonance imaging should be used when the assessment of MR on TTE is not definitive.
7. Decisions regarding the optimal treatment of chronic MR are based on multiple variables, including MR type, MR severity, hemodynamic consequences, disease stage, patient comorbidities, and the experience of the Heart Valve Team and its members.
8. The principal intervention for primary MR is surgery; transcatheter mitral valve repair using an edge-to-edge clip plays a very limited role. In contrast, surgical treatment for secondary MR should be considered only after appropriate medical and device therapies have been instituted. Whenever feasible, mitral valve repair is strongly preferred over mitral valve replacement for primary MR.
9. Common techniques for mitral valve repair include (for primary MR) non-resection techniques using artificial chords or ipsilateral chordal transfer, triangular resection with annuloplasty ring, and sliding leaflet valvuloplasty with annuloplasty ring; and (for secondary MR) restrictive remodeling with a rigid annuloplasty ring, and chordal-sparing mitral valve replacement.
10. Surgeon experience has been recognized as a primary determinant of successful repair. For asymptomatic (stage C1) patients, patients with complex mitral pathoanatomy, and patients who desire a minimally invasive or robotic approach to mitral valve repair, consideration should be given to referral to an experienced mitral surgeon at a comprehensive valve center.
11. Long-term follow-up of patients after surgical or transcatheter mitral intervention is essential for the assessment of durability, functional outcomes, and survival.

Keywords: Cardiac Surgical Procedures, Catheters, Consensus, Diagnostic Imaging, Diastole, Dilatation, Echocardiography, Echocardiography, Transesophageal, Exercise Test, Guideline, Heart Valve Diseases, Heart Valve Prosthesis, Hemodynamics, Mitral Valve, Mitral Valve Insufficiency, Magnetic Resonance Imaging, Patient Care Team, Primary Health Care, Systole

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