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To cure regurgitation brought on by myocardial infarction, more than 40,000 patients domestically have Mitral Valve (MV) repair surgery each year (MI). Although it is thought that ongoing MV tissue remodelling after repair has a significant role in regurgitation recurrence, it is yet unclear how the post MI condition affects MV remodelling. Our inability to forecast the remodelling of the MV both post MI and post surgery to aid surgical planning is a result of this lack of understanding. The present work was conducted to noninvasively measure the effects of MI on MV remodelling in terms of leaflet shape and deformation as a crucial first step. Real time three dimensional echocardiographic images were taken before the MI as well as at 0,4, and 8 weeks after the MI in eight adult dorset sheep. The leaflet surface at systole was scanned in both open and closed states, and the associated scans were extracted using a previously tested image based morphing workflow. We discovered that MI caused long lasting changes in leaflet dimensions in the diastolic configuration. These modifications grew over the course of four weeks before stabilising. When compared to the current time point, MI significantly changed the MV's systolic shape, and the range of stretch that the MV leaflet experienced at peak systole was significantly decreased. Interestingly, the systolic strains remained fairly comparable throughout the post MI period when we referenced the leaflet strains to the pre MI configuration. Overall, we saw that the MV leaflet shape underwent permanent changes as a result of post MI ventricular remodeling.
This mostly had an impact on the MV's diastolic configuration, which had an impact on the leaflet's range of stretch when compared to the existing diastolic configuration. These results are in line with our earlier research, which showed that post MI leaflet deformations were more likely to be plastic (i.e., irreversible), and that this increase was entirely explained by changes in collagen fiber structure. The condition of the MV leaflet can also reveal the progression and degree of MV adaptation after MI, as we have shown through noninvasive methods, and is therefore highly relevant to the creation of new and existing patient specific minimally invasive surgical repair techniques.
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