Anatomy of Mitral Valve Complex as Revealed by Non-Invasive Imaging: Pathological, Surgical and Interventional Implications

Abstract

Knowledge of mitral valve (MV) anatomy has been accrued from anatomic specimens derived by cadavers, or from direct inspection during open heart surgery. However, today two-dimensional and three-dimensional transthoracic (2D/3D TTE) and transesophageal echocardiography (2D/3D TEE), computed tomography (CT) and cardiac magnetic resonance (CMR) provide images of the beating heart of unprecedented quality in both two and three-dimensional format. Indeed, over the last few years these non-invasive imaging techniques have been used for describing dynamic cardiac anatomy. Differently from the "dead" anatomy of anatomic specimens and the "static" anatomy observed during surgery, they have the unique ability of showing "dynamic" images from beating hearts. The "dynamic" anatomy gives us a better awareness, as any single anatomic arrangement corresponds perfectly to a specific function. Understanding normal anatomical aspects of MV apparatus is of a paramount importance for a correct interpretation of the wide spectrum of patho-morphological MV diseases. This review illustrates the anatomy of MV as revealed by non-invasive imaging describing physiological, pathological, surgical and interventional implications related to specific anatomical features of the MV complex.

Keywords: cardiac magnetic resonance; computed tomography; mitral valve anatomy; multimodality imaging; two-dimensional and three-dimensional transthoracic and transesophageal echocardiography.

Figure 1

Cardiac magnetic resonance (CMR) still frame image in cross-section long-axis view in (A) diastole and (B) systole showing the mitral valve apparatus formed by leaflets, annulus, chordae tendinea and papillary muscles. They move in a perfect spatial and temporal coordination to obtain an effective competence and an unrestricted inflow. The “dynamic” anatomy provided by non-invasive imaging techniques gives us the awareness as the structural arrangement of any single component serves to a specific function.

Figure 2

(A) 3D transesophageal echocardiography (TEE) still frame image of mitral valve forms an overhead perspective with a specific rendering algorithm that permits a movable source of light. With a source of light behind the valve, the two components of mitral annulus are well visible (the curved dotted line marks the posterior segment). (B) 2D TEE cross-section long-axis view showing the four components of posterior segment of annulus. The adipose tissue (AT) has a different texture compared with surrounding tissues. (C) CMR cross-section long-axis view. (D) Magnified image of the structures inside the red square in C showing the four components of posterior segment. The AT can be distinguished because the signal is much stronger (white in color) than that of surrounding structures. (E) Computed tomography (CT) cross-section long-axis view. (F) Magnified image of the structures inside the red square in E showing the four components of the posterior segment. As AT is more hypodense to x-ray, it appears as an area that is darker than the surrounding structures. AO = aorta; LV = left ventricle; LA = left atrium.

Figure 3

Three-dimensional TEE image of the mitral valve (MV) from an overhead perspective in (A) diastole and (B) systole. The sphincteric action of the annulus is marked with a red (diastolic) and white (systolic) circumference.

Figure 4

Two-dimensional (A) and three-dimensional (B) TEE cross-section long-axis view showing the hinge line of anterior mitral leaflet (AML), the hinge line of the aorta (AO) and in between the mitral aortic curtain. (C,D) 3D TEE from a ventricular perspective in systole (C) and in diastole (D), showing the mitral–aortic curtain in “en face” view.

Figure 5

(A) 3D TEE with a new volume rendering algorithm from an overhead view, showing the two commissure (arrows) and the P1, P2, P3 scallops of the posterior leaflet. A1, A2, A3 are the corresponding segments of anterior leaflet. (B) CMR cross-section short-axis at the level of mitral leaflets showing the commissures (asterisks) and the scallops. (C) 2D TEE and (D) 3D TEE cross-section long-axis views showing the rough and clear zones.

Figure 6

Three-dimensional TEE, the mitral valve four-basic view. (A) Surgical view. (B) View from left ventricle. (C) Angled lateral-to-medial view. (D) Angled medial-to-lateral view. AML = anterior mitral leaflet; PML = posterior mitral leaflet; MC = medial commissure (asterisk); LC = lateral commissure (asterisk).

Figure 7

(A) 2D TTE and (C) CT cross section in long-axis view. (B,D) Magnified images of the structures inside the red rectangle of panel A and C, respectively, showing the strut and marginal chordae (see text).

Figure 8

(A,B) 2D TTE and (C,D) CMR cross-sections in diastole (A,C) and in systole (B,D) showing the longitudinal contraction of papillary muscle (PM) preventing leaflet eversion during the systole (see text).

Figure 9

(A–D) CT representative images showing as the base of PMs do not attach to the compact myocardium but rather to a network of trabeculations.

Figure 10

(A,C) CMR images in long-axis view in diastole (A) and in systole (C). (B,D) Magnified images of the structures in the red squares in panel A and C, respectively. The insertion of posterior leaflets on the atrial myocardium (arrow) is well visible either in diastole (panel B) or in systole (panel C). The asterisks in both B and D panel mark the curtain-like fibrous tissue. (E) Long-axis view late gadolinium enhancement (LGE) showing the fibrosis on the tip of papillary muscle (PM) and at the base of LV (arrows). (F) Short-axis view LGE showing the fibrosis on the tip of PM.

Figure 11

Three-dimensional TEE surgical view of mitral valve showing the anatomical relationships of mitral valve with the circumflex coronary artery (CX), the coronary sinus (CS) and the atrio-ventricular node (AVN). AML = anterior mitral leaflet, P1–P2–P3 = scallops of posterior mitral leaflet, LCS = left coronary sinus, RCS = right coronary sinus, NCS = non-coronary sinus, MB = marginal branch of CX.