The Heart Valve Society

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Quantifying Infarction-induced Changes in Mitral Valve Geometry and Deformation Using 3D Echocardiography
Bruno V. Rego1, Amir H. Khalighi1, Robert C. Gorman2, Joseph H. Gorman, III2, Michael S. Sacks1.
1University of Texas at Austin, Austin, TX, USA, 2University of Pennsylvania, Philadelphia, PA, USA.

OBJECTIVE: Each year, more than 40,000 people in the United States undergo mitral valve (MV) repair surgery to treat mitral regurgitation caused by myocardial infarction (MI). Unfortunately, long-term efficacy of repair procedures remains a challenge, with 30% of patients experiencing recurrence of regurgitation. Although continual strain-driven remodeling of the MV is believed to be a major cause of repair failure, the effects of MI and repair surgery on MV deformation patterns are not well understood. The goal of the present study was thus to quantify the effects of MI on MV geometry and strains, to facilitate functional assessment and surgical planning.
METHODS: Five ovine MVs were imaged pre-MI and 8 weeks after posterobasal MI using real-time three-dimensional echocardiography (rt-3DE). The acquired images were segmented to extract open-state and closed-state MV geometries (Fig. 1a). A previously validated image-based morphing pipeline was used to register corresponding open- and closed-state scans and infer local directional strains across the leaflet surface at systole. MI-induced changes in geometry and strain patterns were then examined on a subject-specific basis.
RESULTS: Analysis of rt-3DE images showed that the MV annulus is substantially dilated and flattened post-MI, consistent with previous findings. Moreover, both leaflets were severely tethered post-MI, causing them to no longer exhibit tenting in closure. These MI-induced effects propagated throughout both leaflets to yield substantial changes in strain patterns, including increases in circumferential and radial stretches (Fig. 1b).
CONCLUSIONS: These findings indicate that MI significantly exacerbates the strains experienced by the MV in systole. While current surgical repair approaches primarily seek to restore the immediate function of the MV, our results suggest that repair strategies to relieve leaflet strains would curb adverse leaflet remodeling and thus improve long-term outcomes. Ongoing work aims to apply this method to human data for patient-specific repair simulation and optimization.


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