Dipla K, Mattiello J A, Jeevanandam V, Houser S R, Margulies K B
Department of Physiology, Temple University School of Medicine, Philadelphia, PA 19140, USA.
Circulation. 1998 Jun 16;97(23):2316-22. doi: 10.1161/01.cir.97.23.2316.
The failing myocardium is characterized by decreased force production, slowed relaxation, and depressed responses to beta-adrenergic stimulation. In some heart failure patients, heart function is so poor that a left ventricular assist device (LVAD) is inserted as a bridge to transplantation. In the present research, we investigated whether circulatory support with an LVAD influenced the functional properties of myocytes from the failing heart.
Myocytes were isolated from human explanted failing hearts (HF-myocytes) and failing hearts with antecedent LVAD support (HF-LVAD-myocytes). Studies of myocyte function indicated that the magnitude of contraction was greater (9.6+/-0.7% versus 6.9+/-0.5% shortening), the time to peak contraction was significantly abbreviated (0.37+/-0.01 versus 0.75+/-0.04 seconds), and the time to 50% relaxation was reduced (0.55+/-0.02 versus 1.45+/-0.11 seconds) in the HF-LVAD-myocytes compared with the HF-myocytes (P<0.05). The HF-LVAD-myocytes had larger contractions than the HF-myocytes at all frequencies of stimulation tested. The negative force-frequency relationship of the HF-myocytes was improved in HF-LVAD-myocytes but was not reversed. Responses to beta-adrenergic stimulation (by isoproterenol) were greater in HF-LVAD-myocytes versus HF-myocytes.
The results of the study strongly support the idea that circulatory support with an LVAD improves myocyte contractile properties and increases beta-adrenergic responsiveness.
衰竭心肌的特征是力量产生减少、舒张减慢以及对β-肾上腺素能刺激的反应减弱。在一些心力衰竭患者中，心脏功能极差，以至于需要植入左心室辅助装置（LVAD）作为移植的过渡手段。在本研究中，我们调查了LVAD循环支持是否会影响衰竭心脏的心肌细胞功能特性。
从人类离体衰竭心脏（HF-心肌细胞）和先前接受LVAD支持的衰竭心脏（HF-LVAD-心肌细胞）中分离出心肌细胞。心肌细胞功能研究表明，与HF-心肌细胞相比，HF-LVAD-心肌细胞的收缩幅度更大（缩短率为9.6±0.7%对6.9±0.5%），达到收缩峰值的时间显著缩短（0.37±0.01秒对0.75±0.04秒），50%舒张时间缩短（0.55±0.02秒对1.45±0.11秒）（P<0.05）。在所有测试的刺激频率下，HF-LVAD-心肌细胞的收缩都比HF-心肌细胞大。HF-心肌细胞的负性力-频率关系在HF-LVAD-心肌细胞中有所改善，但未逆转。HF-LVAD-心肌细胞对β-肾上腺素能刺激（通过异丙肾上腺素）的反应比HF-心肌细胞更大。
该研究结果有力地支持了以下观点，即LVAD循环支持可改善心肌细胞的收缩特性并增强β-肾上腺素能反应性。
