Key result
Chronic pure mitral regurgitation in sheep significantly reduced global left ventricular systolic torsion at 12 weeks compared to controls (1.7 vs 4.2 degrees, P<0.05).
Why the study?
Does chronic 'pure' mitral regurgitation alone reduce global LV torsion in a sheep model?
Does chronic 'pure' mitral regurgitation alone reduce global LV torsion in a sheep model?
Chronic 'pure' mitral regurgitation alone causes a significant reduction in global LV systolic torsion and increases LV mass index, indicating it is a major driver of torsional deterioration.
Isolates MR as a driver of reduced LV torsion in sheep; leaves open translation to human disease.
BACKGROUND: Global left ventricular (LV) torsion declines with chronic ischemic mitral regurgitation (MR), which may accelerate the LV remodeling spiral toward global cardiomyopathy; however, it has not been definitively established whether this torsional decline is attributable to the infarct, the MR, or their combined effect. We tested the hypothesis that chronic "pure" MR alone reduces global LV torsion. METHODS AND RESULTS: Chronic "pure" MR was created in 13 sheep by surgically punching a 3.5- to 4.8-mm hole (HOLE) in the mitral valve posterior leaflet. Nine control (CNTL) sheep were operated on concurrently. At 1 (WK-01) and 12 weeks (WK-12) postoperatively, the 4D motion of implanted radiopaque markers was used to calculate global LV torsion. MR-grade in HOLE was greater than CNTL at WK-01 and WK-12 (2.5+/-1.1 versus 0.6+/-0.5, P<0.001 at WK-12). HOLE LV mass index was larger at WK-12 compared with CNTL (195+/-14 versus 170+/-17 g/m(2), P<0.01), indicating LV remodeling. Global LV systolic torsion decreased in HOLE from WK-01 to WK-12 (4.1+/-2.8 degrees versus 1.7+/-1.7 degrees , P<0.01), but did not change in CNTL (5.5+/-1.8 degrees versus 4.2+/-2.7 degrees , P=NS). Global LV torsion was lower in HOLE relative to CNTL at WK-12 (P<0.05) but not at WK-01 (P=NS). CONCLUSIONS: Twelve weeks of chronic "pure" MR resulting in mild global LV remodeling is associated with significantly increased LV mass index and reduced global LV systolic torsion, but no other significant changes in hemodynamics. MR alone is a major component of torsional deterioration in "pure" MR and may be an important factor in chronic ischemic mitral regurgitation.
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Ennis et al. (2009) studied Chronic pure mitral regurgitation (n=22). Surgically created chronic pure mitral regurgitation vs. Concurrent control operation was evaluated on Global LV systolic torsion at 12 weeks (p=<0.05). Chronic pure mitral regurgitation in sheep significantly reduced global left ventricular systolic torsion at 12 weeks compared to controls (1.7 vs 4.2 degrees, P<0.05).
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