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Original Articles

Reduced Systolic Torsion in Chronic "Pure" Mitral Regurgitation

Daniel B. Ennis, PhD; Tom C. Nguyen, MD; Akinobu Itoh, MD; Wolfgang Bothe, MD; David H. Liang, MD; Neil B. Ingels, PhD and D. Craig Miller, MD

From the Department of Cardiothoracic Surgery (D.B.E., T.C.N., A.I., W.B., N.B.I., D.C.M.) and the Division of Cardiovascular Medicine (D.H.L.), Stanford University, Stanford, Calif; and the Research Institute (N.B.I.), Palo Alto Medical Foundation, Palo Alto, Calif.

Correspondence to Daniel B. Ennis, Department of Cardiothoracic Surgery, Stanford University School of Medicine, 300 Pasteur Drive, Falk CVRB CV-015, Stanford, CA 94305-5488. E-mail daniel.ennis{at}gmail.com

Received April 16, 2008; accepted January 8, 2009.

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/m², P<0.01), indicating LV remodeling. Global LV systolic torsion decreased in HOLE from WK-01 to WK-12 (4.1±2.8° versus 1.7±1.7°, P<0.01), but did not change in CNTL (5.5±1.8° versus 4.2±2.7°, 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.

Key Words: mechanics • mitral valve • myocardium • ventricles • torsion

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CLINICAL PERSPECTIVE

Related Article

Reduced Systolic Torsion in Chronic "Pure" Mitral Regurgitation

Daniel B. Ennis, Tom C. Nguyen, Akinobu Itoh, Wolfgang Bothe, David H. Liang, Neil B. Ingels, and D. Craig Miller
Circ Cardiovasc Imaging 2009 2: 85-92. [Abstract] [Full Text] [PDF]