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. 2009 Sep 15;120(11 Suppl):S99-103.
doi: 10.1161/CIRCULATIONAHA.109.844019.

Mitral leaflet adaptation to ventricular remodeling: prospective changes in a model of ischemic mitral regurgitation

Miguel Chaput  1 , Mark D Handschumacher, J Luis Guerrero, Godtfred Holmvang, Jacob P Dal-Bianco, Suzanne Sullivan, Gus J Vlahakes, Judy Hung, Robert A Levine; Leducq Foundation MITRAL Transatlantic Network
Affiliations

Mitral leaflet adaptation to ventricular remodeling: prospective changes in a model of ischemic mitral regurgitation

Miguel Chaput et al. Circulation. .

Abstract

Background: Ischemic mitral regurgitation is caused by systolic traction on the mitral leaflets related to ventricular distortion. Little is known about how chronic tethering affects leaflet area, in part because it cannot be measured repeatedly in situ. Recently, a new method for 3D echocardiographic measurement of mitral leaflet area was developed and validated in vivo against sheep valves, later excised. Clinical studies (n=80) showed that mitral leaflet area increased by >30% in patients with inferior myocardial infarction and dilated cardiomyopathy versus normal; greater adaptation independently predicted less mitral regurgitation. This study explored whether mitral valve area changes over time within the same heart with ischemic mitral regurgitation.

Methods and results: Twelve sheep were studied at baseline and 3 months after inferior myocardial infarction by 3D echocardiography; 6 were untreated and 6 were treated initially with an epicardial patch to limit left ventricular dilation and mitral regurgitation. Untreated sheep developed left ventricular dilation at 3 months, with global dysfunction (mean+/-SD ejection fraction, 24+/-10% versus 44+/-10% with patching, P=0.02) and moderate mitral regurgitation (vena contracta, 5.0+/-1.0 versus 0.8+/-1.0 mm, P<0.0002). In untreated sheep, total diastolic leaflet area increased from 13.1+/-1.3 to 18.1+/-2.5 cm(2) (P=0.0001). In patched sheep, leaflet area at 3 months was not significantly different from baseline sheep values (13.0+/-1.1 versus baseline, 12.1+/-1.8 cm(2), P=0.31).

Conclusions: Mitral valve area, independent of systolic stretch, increases over time as the left ventricular remodels after inferior myocardial infarction. This increase, however, fails to compensate adequately for tethering to prevent mitral regurgitation. Understanding the mechanism of valve adaptation can potentially suggest new biological and surgical therapeutic targets.

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Conflict of interest statement

The authors had full access to the data and take full responsibility for its integrity. All authors have read and agree to the manuscript as written. There are no conflicts of interest to declare.

Figures

Figure 1
Figure 1
Study design. IMI, inferior myocardial infarction.
Figure 2
Figure 2
Method of mitral leaflet area measurement (left) showing leaflet reconstruction in a normal beating sheep heart.
Figure 3
Figure 3
MR severity at baseline, immediately after IMI, and at 3 months follow-up (mean±SD). PJW, proximal jet width.
Figure 4
Figure 4
LV end-systolic volume and ejection fraction at 3 months follow-up (mean±SD). LVESV, left ventricular end systolic volume, EF, ejection fraction.
Figure 5
Figure 5
Total leaflet area, annular area and closure area at baseline and at 3 months follow-up (mean±SD).
See this image and copyright information in PMC

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