Multimodal image analysis and subvalvular dynamics in ischemic mitral regurgitation

Figures

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  Multimodal imaging showing mitral valve leaflet remodeling is heterogenous and allows for papillary muscle staging.

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  Figure 1. Overview of the study. Using magnetic resonance imaging and 3-dimensional echocardiography, we followed 6 ischemic mitral regurgitation (IMR) ovine models at baseline, 30 minutes post–myocardial infarction (MI), and 12 weeks post-MI to study the valvular and subvalvular apparatus of the mitral valve in IMR. This could allow for better preoperative planning and tailoring of adjunct surgical treatment.

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  Figure 2. Magnetic resonance imaging (MRI) image processing technique. Two-dimensional multislice images were reconstructed with volume segmentation and processing software. A, Reconstructed 3-dimensional (3D) model of baseline MRI. The anterolateral papillary muscle (ALPM) is marked with yellow, and the posteromedial papillary muscle (PMPM) is in light blue. B, Late gadolinium-enhanced MRI at 12 weeks after myocardial infarction (MI). Short-axis view. C and D, 3D reconstructed model at 12 weeks post-MI in the same animal as in A. The infarcted area (INF) is marked in brown. C, Atrial view. D, Posteromedial view.

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  Figure 3. Regional mitral valve (MV) leaflet adaptation. A, Regional anterior MV leaflet length at baseline (blue), 30 minutes post–myocardial infarction (MI) (red), and 12 weeks post-MI (green). The leaflet length is plotted as a function of intercommissural distance, expressed as a percentage of the distance traveled from the anterior commissure (AC). The positions of the AC and posterior commissure (PC) are 0% and 100%, respectively. B, Regional posterior valve leaflet length at baseline (blue), 30 minutes post-MI (red), and 12 weeks post-MI (green).

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  Figure 4. Coordinate system used to calculate position and dynamics of the papillary muscles. The mitral annular center (ANC) was set as the coordinate origin. We defined the positive X direction as the vector pointing toward the posterior horn of the mitral annulus. We defined the positive Y direction as the vector pointing toward the posterior commissure and the positive Z direction as the vector pointing toward the left atrial roof. PCM, Posterior commissure; AAOP, anterior aortic peak; MPA, midpoint of posterior annulus; AC, anterior commissure; LV, left ventricular.

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  Figure 5. Papillary muscle (PM) tracing technique. A, Resected heart after euthanization. The right ventricle and atria were removed, and the left ventricular septum was cut longitudinally from the aortic root toward the apex. The number of PM tips and anatomic characteristics were identified. B, Oblique view of 2-dimensional echocardiography (2DE) at baseline. PM tips were marked according to the anatomic characteristics obtained from the resected specimen. C, Short-axis view of 2-DE with the PMs marked. D and E, Traced annulus and leaflets along with marked PMs in right lateral oblique view (D) and front view from the left atrial side (E). ALPM, Anterolateral papillary muscle; PMPM, posteromedial papillary muscle.

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  Figure 6. A new papillary dynamics framework in ischemic mitral regurgitation (IMR) pathogenesis. At baseline, papillary muscle (PM) movement can be described as bilateral congruent movement with full range of motion and preserved PM to the annular center distance (PM-ANC). In the acute phase of IMR, the PPM motion is dampened with preserved PM-ANC and can thus be described as bilateral noncongruent movement. In chronic IMR, the PM movement is unilateral with minimal PPM movement (SUM1) or strictly no PPM movement (SUM2). SUM, Strict unilateral movement.

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  Figure 7. Temporal papillary muscle (PM) and annular dynamics throughout the cardiac cycle at serial time points. The top row compares mean annular and PM positions at end-diastole (blue) and at end-systole (red) in the atrial plane (left upper corner), Septolateral plane (right upper corner), intercomissural plane (left lower corner), and 3-dimensional view (right lower corner) at A, baseline; B, 30 minutes post–myocardial infarction (MI); and C, 12 weeks post-MI. The annuli are represented by circular shapes, and the PMs are represented by dots. The annular center was set as the origin. A, anterior annulus; L, left lateral annulus; P, posterior annulus; R, right lateral portion of the mitral annulus. The bottom row shows comparisons between mean annular and PM positions at baseline (base; blue), 30 minutes post-MI (red), and 12 weeks post-MI (green) at 3 different cardiac phases: D, end-diastole; E, mid-systole; F, end-systole. Table 8 shows the geometric papillary muscle position in Cartesian coordinates throughout cardiac cycle.