Ischemic mitral regurgitation (MR) affects 1.2 to 2.1 million patients in the United States, with more than 400,000 patients having moderate-to-severe MR. [1
] Chronic ischemic MR of 2+ severity discovered at cardiac catheterization for symptomatic coronary artery disease has a 1-year mortality of approximately 17% [2
] and the one-year mortality for 3+ and 4+ ischemic MR is approximately 40%. [2
Ischemic MR is usually managed with mitral annuloplastyalone. [3
] However, the need for surgical therapy and the type of surgical therapy remains unclear. For instance, the type of annuloplasty(flexible vs. rigid, complete vs. incomplete) is controversial [3
] and the role of surgical remodeling with devices including the Acorn CorCap [5
] and Coapsys [6
] is unclear.
Finite element (FE) modeling of the heart and heart valves is becoming more and more common. For instance, there have been numerous FE modeling studies of the aortic valve, either as a bioprosthesis or as native tissue. In contrast, the mitral valve is structurally more complex and includes the contracting left ventricular (LV) wall as a structural element. As a consequence, most FE models of the mitral valve assume that the papillary muscles are fixed in space. Examples include the work of Kunzelman et al [7
], who generated the first FE model of an isolated mitral valve. Finite element models of the isolated mitral valve have now been used to determine the effect of artificial chordae on valve deformation [9
], the effects of leaflet and annular curvature on leaflet stress [10
], and the effects of innovative annuloplasty ring shape. [11
] More recently, modeling of the mitral leaflets has become more realistic [13
] and fluid structure interaction (FSI) has been added. [14
On the other hand, FE models of the LV that incorporate myocardial contractility have been described and used to determine the effect of myocardial infarction on structure and function. [15
] Additionally, the efficacy of various surgical procedures has been simulated with the FE method. [18
] Most recently, a method for determining myocardial material properties non-invasively was developed using FE modeling and optimization [20
]. To date, however, FE models of the LV have not included the mitral valve.
In the current study, we expand our previous FE models of the LV [20
] to incorporate the leaflets and chordae of the mitral valve. The model is based on MRI data from a sheep that has developed moderate ischemic MR after postero-basal myocardial infarction. [21
] We demonstrate the utility and power of the method by using the FE model to test the hypothesis that a reduction in infarct stiffness will increase dyskenesis of the posterior LV wall, increase the displacement of the posterior papillary muscle and thereby increase ischemic mitral regurgitation.