Key result
Acute ischemic MR in canines increases posterior papillary muscle tethering length by ~1.3 mm.
Live three-dimensional echocardiography demonstrates that mitral apparatus geometry changes, specifically posterior papillary muscle tethering, contribute significantly to acute ischemic mitral regurgitation.
Animal data implicate mitral apparatus geometry in acute IMR; leaves open translation to human disease or therapy.
Objective. Mitral apparatus geometry changes during ischemic mitral regurgitation (MR) play an important role in finding mechanisms for ischemic MR. Live three-dimensional echocardiography (L3DE) is a new technique providing cardiac full-volume image in a very short time. We applied this technique to evaluate mitral apparatus geometry changes during acute ischemic MRs.Methods. After baseline two-dimensional echocardiography (2DE) and L3DE image acquiring, the left circumflex (LCX) coronary artery distal to the first obtuse marginal artery origin was ligated in order to produce an acute ischemic MR in 10 canines. When significant ischemic MR occurred, 2DE and L3DE imagings were repeated. PM tethering distance and mitral annular geometric dilation were measured by L3DE.Results. Acute ischemic MR was successfully produced by LCX ligation in 8 canines. MR grade increased from 0.5±0.2 at baseline to 2.4±0.2 during ischemic MR in scale, P<0.05. Mitral annulus dilated asymmetrically; anterior mitral annular perimeter length increased 10.0±3.2%, and posterior mitral annular perimeter length increased 19.4%±5.1% at mid-systole. The mitral annular configuration also somewhat distorted. The posterior annulus near anterior lateral commissure and that near posterior medial commissure could not be shown at the same level if we adjusted the anterior annulus and two commissures at the same level. The posterior papillary muscle (PPM) tethering length increased 1.3 ±0.2mm (p<0.05). The multiple linear regression analysis results showed that increase of PPM tethering distance was the only independent factor determining proximal MR jet cross-section area (r2=0.77).Conclusions. Live three-dimensional echocardiography can show mitral annulus spatial configuration and can be used to address questions related to mitral apparatus. Mitral apparatus geometry changes are contributed to acute ischemic MR.
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Zhang et al. (2006) studied Acute ischemic mitral regurgitation (n=10). Left circumflex artery ligation vs. Baseline (pre-ligation) was evaluated on Posterior papillary muscle (PPM) tethering length (mm) (MD 1.3, p=<0.05). Acute ischemic mitral regurgitation induced by left circumflex artery ligation in canines significantly increased posterior papillary muscle tethering length by 1.3 mm compared to baseline.
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