Spratt J A, Olsen C O, Tyson G S, Glower D D, Davis J W, Rankin J S
J Thorac Cardiovasc Surg. 1983 Oct;86(4):479-89.
It has been suggested that mitral valve replacement for mitral regurgitation can precipitate acute myocardial failure by increasing left ventricular afterload. However, most studies of this problem have involved anesthesia, acute surgical trauma, or ischemic cardioplegia, each of which can influence myocardial function. The pure hemodynamic consequences of mitral valve replacement were investigated by surgically instrumenting eight dogs with ultrasonic transducers to measure left ventricular diameter, electromagnetic flow probes to measure ascending aortic blood flow, and micromanometers to measure left ventricular and pleural pressures. At the time of implantation, an 8 mm stainless steel shunt was inserted through the left ventricular myocardium at the base of the anterior wall and sutured to the left atrial appendage, producing simulated mitral regurgitation of 20% to 40% of total ventricular output. Balloon occluders were placed around the left atrial shunt and both venae cavae. One to 7 days after implantation, each dog was studied in the conscious state, and data were recorded during acute occlusion of the shunt. After shunt occlusion, left ventricular mean ejection pressure increased significantly in all studies. Systolic wall tension also increased by an average of 8%, diameter shortening decreased by 21%, and forward cardiac output increased by 17%. Thus the higher afterload associated with elimination of mitral regurgitation produced an acute fall in stroke shortening and total left ventricular output. However, forward cardiac output increased in all studies, implying improved pump efficiency and overall cardiac performance. Thus the improvement in pump efficiency associated with restoration of mitral valve competence uniformly increases forward cardiac output despite an increased ventricular afterload and a decreased total stroke volume. Although there may be differences between this relatively acute model and chronic forms of mitral regurgitation encountered clinically, these data suggest that forward cardiac output should increase with correction of mitral regurgitation and that the associated augmentation in afterload is probably not a major factor causing low cardiac output after correction.
有人提出，二尖瓣反流的二尖瓣置换术可通过增加左心室后负荷而引发急性心肌衰竭。然而，关于这个问题的大多数研究都涉及麻醉、急性手术创伤或缺血性心脏停搏，其中每一项都可能影响心肌功能。通过手术给八只狗植入超声换能器以测量左心室直径、电磁血流探头以测量升主动脉血流量以及微测压计以测量左心室和胸膜压力，来研究二尖瓣置换术的单纯血流动力学后果。在植入时，将一根8毫米的不锈钢分流管穿过前壁底部的左心室心肌并缝合到左心耳，产生相当于心室总输出量20%至40%的模拟二尖瓣反流。在左心房分流管和两条腔静脉周围放置球囊封堵器。植入后1至7天，在清醒状态下对每只狗进行研究，并在急性封堵分流管期间记录数据。在所有研究中，分流管封堵后，左心室平均射血压力显著增加。收缩期壁张力平均也增加了8%，直径缩短减少了21%，前向心输出量增加了17%。因此，与消除二尖瓣反流相关的较高后负荷导致了每搏缩短和左心室总输出量的急性下降。然而，在所有研究中前向心输出量都增加了，这意味着泵效率和整体心脏功能得到改善。因此，尽管心室后负荷增加且总每搏量减少，但与二尖瓣功能恢复相关的泵效率提高一致地增加了前向心输出量。尽管这个相对急性的模型与临床上遇到的慢性二尖瓣反流形式可能存在差异，但这些数据表明，纠正二尖瓣反流后前向心输出量应该会增加，并且相关的后负荷增加可能不是纠正后导致心输出量降低的主要因素。
