Geometric Distortions of the Mitral Valvular-Ventricular Complex in Chronic Ischemic Mitral Regurgitation

Abstract

Background— Better understanding of the precise 3-dimensional geometric changes of the mitral valvular-ventricular complex in chronic ischemic mitral regurgitation (CIMR) is needed in order to devise better surgical repair techniques. We hypothesized that changes after inferior myocardial infarction would be different in hearts that developed CIMR compared with those that did not. Methods and Results— Twenty-four sheep underwent coronary snare and marker placement (annulus, papillary muscles, and anterior and posterior leaflets). After 8 days, cinefluoroscopy provided 3-dimensional marker data, and snare occlusion of obtuse marginal branches created inferior myocardial infarction, including the posterior papillary muscle. After 7 weeks, the 16 surviving animals were studied again and grouped by mitral regurgitation grade (≥ 2+, n=10 versus ≤ 1+, n=6). End-systolic mitral annulus dimensions, components of papillary muscle and leaflet displacement, were calculated. After inferior myocardial infarction, total displacement of the posterior papillary muscle from the midseptal annulus (“saddle horn”) was greater in CIMR(+) animals: 6.5±3.2 versus 3.1±2.7 ( P =0.02), with the posterior papillary muscle moving more laterally (6.8±3.4 versus 2.5±3.5 mm, P =0.01). Increase in mitral annular septal-lateral diameter was greater in animals with CIMR (4.9±2.7 versus 2.3±2.0, P =0.02), and apical displacement of the posterior leaflet (PL) margin was also greater in the CIMR(+) group (1.7±1.0 versus 0.3±0.5, P =0.01). Conclusions— The CIMR(+) group had greater septal-lateral annular dilatation, lateral posterior papillary muscle displacement, and apical PL restriction, indicating that these associated geometric alterations may be important in the pathogenesis of CIMR. Treatment of CIMR should address both annular septal-lateral dilatation and lateral displacement of the posterior papillary muscle.

Asynchronous Movement of Mitral Annulus: An Additional Mechanism of Ischaemic Mitral Regurgitation

“…Previous studies suggested a number of mechanisms responsible for ischaemic MR, such as tethering of the leaflets by the displaced papillary muscles, 3 annular dilatation and other geometric changes, 5,20,21 global and local left ventricular remodeling and sphericization. 1,2 Clearly, isolated changes, such as isolated annular dilatation, are not able to cause important functional MR. 14 However acting in concert, geometric distortions of mitral valvular-ventricular complex lead to diminished leaflet coaptation and MR. 21 Surgery of functional MR aims mainly at reduction of mitral annular size.…”

“…1,2 Clearly, isolated changes, such as isolated annular dilatation, are not able to cause important functional MR. 14 However acting in concert, geometric distortions of mitral valvular-ventricular complex lead to diminished leaflet coaptation and MR. 21 Surgery of functional MR aims mainly at reduction of mitral annular size. 20 However MR may persist or recur in spite of ring implantation.…”

Percutaneous Mitral Valve Repair for Chronic Ischemic Mitral Regurgitation

“…[7][8][9][10][11][12][13] Despite this mechanistic complexity, annuloplasty alone produces satisfactory reduction of IMR in up to 80% of cases. 21 This suggests that development of less invasive and safer methods of mitral annuloplasty might afford an important clinical benefit for large numbers of patients with IMR.…”

“…[7][8][9][10][11][12][13] Using real-time 3D (RT3D) echocardiography, we demonstrated that medial MV tenting area (MVTa) is an important determinant of MR severity in IMR. 13 Clinical experience and experimental study, 14 however, have demonstrated that reducing the distance between the anterior and posterior annulus (A-P diameter) by surgical annuloplasty reduces or eliminates IMR.…”

Cardioband for the treatment of secondary mitral regurgitation: a viable percutaneous option?

“…As with surgical mitral restrictive annuloplasty, the Cardioband reduced the septolateral diameter of the mitral annulus (3.67±0.47 vs. 2.41±0.44 cm, P<0.001), but did not address the coexisting geometric subvalvular distortions. Persistent MR after MV repair is the result of continued left ventricular remodeling and dilatation, which perpetuates posterolateral and apical papillary muscle displacement, mitral leaflet tethering by the chordae tendinae, and incomplete systolic mitral valve closure (8,9). Data suggests that in the setting of left ventricular dilatation and secondary MR, a 1.5-fold increase in annular size may be tolerated prior to exacerbation of the MR regurgitant volume, reinforcing the importance of subvalvular dysfunction (10).…”