下壁和前壁心肌梗死致缺血性二尖瓣反流的不同机制

Different mechanisms of ischemic mitral regurgitation in patients with inferior and anterior myocardial infarction

目的比较前壁和下壁心肌梗死患者二尖瓣装置的结构特征,以探讨此两种情况下二尖瓣反流的不同机制。方法研究对象为连续收治的陈旧性下壁心肌梗死患者33例(下壁梗死组)、前壁心肌梗死61例(前壁梗死组)和超声心动图无异常的受试者22例(正常对照组)。在系统超声心动图检查的基础上,用二维和多普勒超声方法测量左心室容量、二尖瓣瓣环面积和二尖瓣反流分数。分别在心尖四腔和二腔心切面测量前外侧乳头肌和后内侧乳头肌至对侧二尖瓣环的牵引距离。结果下壁梗死组中12例(36%)患者有反流分数超过20%的二尖瓣反流,前壁梗死组为7例(11%);在并发二尖瓣反流的下壁梗死组中,后内侧乳头肌牵引距离显著长于前外侧乳头肌的牵引距离〔(42.6±4.9)mm vs.(36.1±1.7)mm,P<0.01〕;而在前壁梗死组中,两侧乳头肌牵引距离显著长于正常对照组〔(41.0±2.4)mm、(41.4±1.8)mm vs.(33.5±2.2)mm、(33.4±2.1)mm,P<0.01)〕,但两侧乳头肌间差异无显著性(P>0.05)。多元回归分析发现,后内侧乳头肌牵引距离和两乳头肌牵引距离之和分别是下壁心肌梗死和前壁心肌梗死并发二尖瓣反流的独立影响因素。结论下壁心肌梗死并发二尖瓣反流时,二尖瓣结构表现为以后内侧乳头肌为主的非对称性移位;前壁心肌梗死之缺血性二尖瓣反流则与二尖瓣结构中两乳头肌对称性移位有关。

Objective To discuss the different mechanisms of mitral regurgitation （MR） by comparison of the complex mitral geometry in patients with anterior myocardial infarction （MI） and patients with inferior MI. Methods 33 consecutive patients with prior inferior MI （ inferior MI group）, 61 consecutive patients with anterior MI （ anterior MI group） and 22 subjects with normal echocardiograms （control group） were enrolled in our research. Based on systemic echocardiography, left ventricular （LV） volume, mitral annular area and MR fraction were quantified by 2D and color Doppler flow imaging. PM tethering distances were determined by measurement of interpapillary distances to the mitral valve annulus in apical four - chamber and corss - sectional two - chamber views. Results Significant MR （ MR fraction 〉 20% ） was observed in 12 of the 33 with inferior MI and 7 of the 61 with anterior MI. In inferior MI patients complicated with MR, tethering distance was significantly longer in medial compared to lateral PM [ （42.6 ± 4.9） mm vs. （36.1 ±1.7 ） mm, P 〈 0.01 ） ] , demonstrating asymmetric medial PM displacement. Patients with MR due to anterior MI had comparable increases in both PM tethering distances [ （41.0 ±2.4） vs. （41.4 ±1.8 ） mm, P 〉 0.05 ], demonstrating symmetric bilateral PM displacement. Multiple regression analysis revealed that posteromedial papillary tethering distance and the sum of bilateral tethering distances were the independent influence factors contributing to inferior MI and anterior MI complicated with MR, respectively. Conclusion Patients with ischemic MR complicated with inferior MI have asymmetrically predominant medial PM displacement, while those with ischemic MR during anterior MI have symmetric bilateral PM displacements.