Degenerative mitral regurgitation

Abstract

Degenerative mitral regurgitation is a major threat to public health and affects at least 24 million people worldwide, with an estimated 0.88 million disability-adjusted life years and 34,000 deaths in 2019. Improving access to diagnostic testing and to timely curative therapies such as surgical mitral valve repair will improve the outcomes of many individuals. Imaging such as echocardiography and cardiac magnetic resonance allow accurate diagnosis and have provided new insights for a better definition of the most appropriate timing for intervention. Advances in surgical techniques allow minimally invasive treatment with durable results that last for ≥20 years. Transcatheter therapies can provide good results in select patients who are considered high risk for surgery and have a suitable anatomy; the durability of such repairs is up to 5 years. Translational science has provided new knowledge on the pathophysiology of degenerative mitral regurgitation and may pave the road to the development of medical therapies that could be used to halt the progression of the disease.

Fig. 1 |. Types of degenerative mitral regurgitation.

a, 3D transoesophageal echocardiography image shows mitral valve prolapse of the central segment of the posterior mitral leaflet (asterisk) owing to chorda rupture (flail; arrow). b, More advanced form of degenerative mitral regurgitation, in which the prolapse of the posterior mitral leaflet (asterisk) is wider and has two chorda ruptured (arrows). c, The most advanced form of degenerative mitral regurgitation is characterized by redundant, excessive tissue and prolapse of both the anterior mitral leaflet (AML) and the posterior mitral leaflet (PML). Ao, aortic valve.

Fig. 2 |. Structural changes in degenerative mitral regurgitation.

a, The anatomy of the mitral valve apparatus and the histological structure of the mitral valve leaflet. b, In degenerative mitral valve disease, the prolapsing scallop of the posterior mitral leaflet shows significant growth of the spongiosa layer. In addition, dilatation of the left atrium and ventricle, fibrosis of the papillary muscles and ruptured chordae can occur.

Fig. 3 |. Morphological features of the normal mitral valve and degenerative mitral valve disease.

Normal (panels a–c) and degenerative (panels d–i) mitral valves stained for elastin (panels a,d and g; stained with Weigert’s resorcin fuchsin), collagen (panels b,e and h; stained with Masson’s trichrome) and glycosaminoglycans (GAGs; panels c,f and I; stained with Alcian blue). Degenerative mitral valves show an abnormal organization of the extracellular matrix with disrupted elastin, diminished and loose collagen in the fibrosa layer and expansion of the spongiosa layer. In addition, superimposed tissue (SIT) is detected at the atrial and ventricular sides of the original leaflet, contributing to increased thickness of the leaflet. Scale bar, 500 mm. Reprinted from ref. , CC BY 4.0.

Fig. 4 |. Mitral annulus abnormalities in degenerative mitral regurgitation.

a,b, Cardiac CT images show mitral valve prolapse of the central and medial scallop of the posterior mitral leaflet (black arrows and asterisks). The posterior mitral annulus shows prominent calcification (panel a, white arrow) underneath the prolapsing posterior mitral leaflet. The white dashed line shows the plane of the image in panel b. c, Severe degenerative mitral regurgitation and mitral annulus disjunction (white double arrowhead) shown as the separation of the mitral annulus and the posterior mitral leaflet at end-systole. Ao, aortic valve; LA, left atrium; LV, left ventricle; MV, mitral valve.

Fig. 5 |. Management of patients with severe chronic primary mitral regurgitation.

AF, atrial fibrillation; HF, heart failure; LA, left atrium/left atrial; LVEF, left ventricular ejection fraction; LVESD, left ventricular end-systolic diameter; SPAP, systolic pulmonary arterial pressure; TEER, transcatheter edge-to-edge repair. ^aLA dilatation: volume index ≥60 ml/m² or diameter ≥55 mm at sinus rhythm. ^bExtended heart failure treatment includes the following: cardiac resynchronization therapy; ventricular assist devices; and heart transplantation. Reprinted with permission from ref. , OUP.

Fig. 6 |. Transcatheter mitral valve repair techniques for primary mitral regurgitation.

Treatment of a posterior mitral valve prolapse (panel a, arrow) treated with a transcatheter edge-to-edge device (panels a–c). The device is orientated perpendicular to the line of coaptation and at the level where the flail is located (panel b). The blue and red dotted lines represent the bicommissural and the left ventricular outflow tract views, respectively, shown in panel c. After the device is closed, there is no mitral regurgitation. Treatment of a posterior mitral valve prolapse of the central scallop (panel d, arrow) with transapical neochords (panels d–g). The 3D reconstruction (panel e) shows the width of the prolapsing central scallop of the posterior mitral leaflet (arrow). Guidance of the procedure with 3D reconstruction and the biplane views (panel f) shows the device with the jaws that will catch the prolapsing segment where the neochords will be inserted (arrows). After repair (panel g), no mitral regurgitation is present. Ao, aortic valve.