Abstract 15629: Adequate Mitral Leaflet Compensation Prevents Development of Ischemic Mitral Regurgitation
Background: Although inferior myocardial infarctions (IMI) are commonly associated with development of ischemic mitral regurgitation (IMR), it is unclear why some patients develop IMR despite similar size and location of MI. We hypothesized that the development of IMR in MI of similar size and location relates to differences in compensatory leaflet adaptation to post MI remodeling.
Methods: Eleven sheep underwent ligation of circumflex branches to create similar IMI. Two months after MI, MR [vena contracta (VC)], end-diastolic (EDV), end-systolic volumes (ESV) were measured by 2D echo. Mitral leaflet adaptation was measured as the ratio of total leaflet area (at end-diastole) to closure leaflet area (at mid-systole) (LeafA/ClosA) and ratio of total leaflet to annular area (LeafA/AnnA). These measures reflect the extent of leaflet remodeling needed to maintain mitral valve (MV) closure in setting of distortion of MV-LV spatial relationship from post MI remodeling. Lower ratios are consistent with inadequate leaflet adaptation to maintain MV closure whereas higher ratios reflect more adequate leaflet adaptation.
Results: At baseline, there were no differences in EDV or ESV or MR. No-MR sheep had larger ratios compared to +MR (LeafA/ClosA: 1.29±0.07 vs. 1.2±0.04; p<0.05), suggesting greater leaflet area availability for MV closure in the No-MR group. Two months post MI, 7 sheep developed moderate MR (+MR) with VC of 4.8±0.7mm and 4 sheep had mild or less MR (No-MR) with VC of 1.2±0.5 mm, P<0.001, relative to +MR. Both +MR and No- MR groups had similar increases in LV volumes (No-MR vs. + MR; EDV, 46%± 25 vs. 50%± 38; ESV, 76%± 25 vs.77%± 47; P=ns). LeafA/ClosA and LeafA/AnnA decreased significantly in +MR but did not change in the No-MR sheep (figure).
Conclusion: The development of IMR following infarction is associated with decreased mitral leaflet area available for closure at baseline as well as inadequate mitral leaflet adaptation to post MI remodeling.
- © 2011 by American Heart Association, Inc.