二尖瓣瓣下结构的心肌力学功能研究

Myocardial Mechanics of the Mitral Subvalvular Apparatus

以离体兔心灌注模型研究二尖瓣瓣环—乳头肌连续中断、腱索“牵拉”作用丧失后左室收缩及舒张特性的改变以及对左室过度充盈耐受性的影响。结果显示，连续中断后Ｅｍａｘ和ｄｐ／ｄｔｍａｘ减小，ＩＥＳＰＶＲ曲线压低，左室僵硬度常数（Ａｌｐｈａ）和等容舒张期时间常数（Ｔａｕ）以及－ｄｐ／ｄｔｍａｘ减小，ＰＰＶＲ曲线右移。遭受过度充盈后（ＥＤＰ１２ｋＰａ，６０ｓ），上述各项指标出现进一步的类似变化。结论：（１）二尖瓣及其瓣下结构具有不可忽视的心肌力学功能，即瓣膜—心室协同作用。（２）瓣环—乳头肌连续中断后，左室收缩性减退，压力负荷耐受性削弱；主动舒张功能减弱而被动扩张性增加，左室过度充盈耐受性较瓣下结构完整时明显减弱。因此，我们认为在二尖瓣替换术中保持瓣环—乳头肌的连续性，具有重要的心肌力学意义。

The changes of left ventricular systolic and diastolic characteristics as well as the tolerance of LV to over-filling were studied with an isolated perfused rabbit heart model. In this model,he papillary muscles were disconnected from the mitral anulus resulting in loss of the “tethering effect” of mitral tendineae. The experimentai data showed reduction of E max and dp/dt max, and sinking of IESPVR curve; reduction of the constant of the LV stiffness(Alpha), time constant of isovolumic relaxation (Tau) and -dp/dt max, rightward shift of PPVR curve. And all of them were further deteriorated after additional LV over-filling (EDP 12 kpa, 60 seconds). We concluded that 1.mitral valve and its subvalvular apparatus possess an important mechanical property or valve-ventricular interaction; 2. disconnection of the papillary muscles from mitral anulus will result in the decrease of LV contractility with poor tolerance to pressure load, the impairment of LV active relaxation and increase of LV distensibility. The later 2 factors make the tolerance of LV to over-filling very much limited. We considered that it is of great mechanical significance to keep the connection between mitral annulus and papillary muscles during mitral valve replacement.