Klues H G, Roberts W C, Maron B J
Pathology Branch, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, Md. 20892.
Circulation. 1991 Sep;84(3):1188-97. doi: 10.1161/01.cir.84.3.1188.
Obstruction to left ventricular outflow in hypertrophic cardiomyopathy (HCM) is usually due to systolic anterior motion of the mitral valve. Occurrence of structural mitral valve abnormalities in HCM and their significance in producing outflow obstruction (even in the absence of typical systolic anterior motion) has not been fully appreciated.
Analysis of 78 mitral valves excised from patients with obstructive HCM showed that 10 (13%) had anomalous insertion of one or both left ventricular papillary muscles directly into the anterior mitral leaflet. This malformation was identified by echocardiography, which demonstrated direct continuity between the hypertrophied papillary muscle and mitral leaflet, resulting in a long rigid area of midcavity narrowing that appeared to be solely or largely responsible for outflow obstruction. Basal subaortic pressure gradients were large (70-150 mm Hg). Mitral valve replacement reduced the outflow gradient substantially to 0-15 mm Hg in four patients with postoperative cardiac catheterization. However, two other patients who underwent septal myotomy/myectomy had persistent symptoms and incomplete relief of obstruction (gradients 60 and 70 mm Hg) because of continued midcavity apposition of papillary muscle and ventricular septum.
Anomalous papillary muscle insertion into anterior mitral leaflet represents a mechanism of obstruction to left ventricular outflow in patients with HCM and differs considerably from typical dynamic obstruction caused by mitral valve systolic anterior motion that occurs in many other patients with HCM. Recognition of this malformation emphasizes the diverse morphological expression of HCM and also has important clinical implications for patients requiring operation because the gradient is likely to persist even after adequate myotomy/myectomy; consequently, mitral valve replacement would appear to be the operation of choice in most such patients.
肥厚型心肌病（HCM）中左心室流出道梗阻通常是由于二尖瓣收缩期前向运动所致。HCM中二尖瓣结构异常的发生情况及其在导致流出道梗阻（即使在无典型收缩期前向运动时）中的意义尚未得到充分认识。
对78例梗阻性HCM患者切除的二尖瓣进行分析显示，10例（13%）存在一根或两根左心室乳头肌直接异常插入二尖瓣前叶的情况。这种畸形通过超声心动图得以识别，其显示肥厚的乳头肌与二尖瓣叶之间存在直接连续性，导致中腔狭窄形成一个长而僵硬的区域，似乎单独或主要导致流出道梗阻。主动脉瓣下基底部压力阶差较大（70 - 150 mmHg）。二尖瓣置换术使4例术后行心导管检查的患者流出道阶差大幅降至0 - 15 mmHg。然而，另外2例接受室间隔肌切开/切除术的患者仍有持续症状且梗阻缓解不完全（阶差分别为60和70 mmHg），原因是乳头肌与室间隔持续在中腔贴合。
乳头肌异常插入二尖瓣前叶是HCM患者左心室流出道梗阻的一种机制，与许多其他HCM患者中由二尖瓣收缩期前向运动引起的典型动态梗阻有很大不同。认识到这种畸形强调了HCM形态学表现的多样性，对需要手术的患者也具有重要临床意义，因为即使进行了充分的肌切开/切除术后阶差仍可能持续存在；因此，二尖瓣置换术似乎是大多数此类患者的首选手术方式。
