Published Online
on January 22, 2009

A more recent version of this article appeared on March 1, 2009

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Original Article

Reduced systolic torsion in chronic "pure" mitral regurgitation

Daniel B. Ennis^1,3; Tom C. Nguyen¹; Akinobu Itoh¹; Wolfgang Bothe¹; David H. Liang¹; Neil B. Ingels² and D. Craig Miller¹

¹ Stanford University, Stanford, California;
² Stanford University, Stanford & Palo Alto Medical Foundation, Palo Alto, California

³ E-mail: daniel.ennis{at}ucla.edu

Background—Global left ventricular (LV) torsion declines with chronic ischemic mitral regurgitation (CIMR), which may accelerate the LV remodeling spiral toward global cardiomyopathy; however, it has not been definitively established whether this torsional decline is due 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 thirteen sheep by surgically punching a 3.5-4.8mm hole (HOLE) in the mitral valve posterior leaflet. Nine control (CNTL) sheep were operated upon concurrently. At one (WK-01) and twelve weeks (WK-12) postoperatively, the 4-D 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 vs. 0.6±0.5, P<0.001 at WK-12). HOLE LV mass index (LVMI) was larger at WK-12 compared to CNTL (195±14 vs. 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° vs. 1.7°±1.7°, P<0.01), but did not change in CNTL (5.5°±1.8° vs. 4.2°±2.7°, P=N.S.). Global LV torsion was lower in HOLE relative to CNTL at WK-12 (P<0.05), but not at WK-01 (P=N.S.).

Conclusions—Twelve weeks of chronic "pure" MR resulting in mild global LV remodeling is associated with significantly increased LVMI 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 CIMR.

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

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]