Objective To investigate the cause for stenosis of adult left ventricular outflow tract that is easy to miss diagnosis clinically and its sonographic representation. Methods We scanned the heart as conventional method with focus on observation of left ventricular outflow tract, ventricular wall thickness, change characteristics of motion curve of the mitral valve as well as change in dynamics of blood flow in the left ventricular outflow tract. Results Causes for stenosis were local thickening of the base of interventricular septum( 26 cases ), stenosis due to thickening of fibrous tendinous cords( 4 cases ), combined false tendon due to local thickening of base of ventricular septum( 2 cases ). Common manifestations were no significant thickening on left ventricular wall,stenosis of left ventricular outflow tract, high-speed blood flow information detected at the stenosis location of left ventricular outflow tract, all the motion curves of mitral valve showing obvious forward motion of systole for CD section( SAM phenomenon ),and combined aortic insufficiency( 19 cases ). Causes for missed diagnosis of stenosis were local thickening of the base of interventricular septum only displayed on a section instead of all sections, no significant thickening on the whole left ventricular wall,the combined backward flow of aortic valve masking the presence of narrow blood flow of the left ventricular outflow tract, stenosis caused by fibrous tendons easily confused with hypertrophic cardiomyopathy. Conclusions Only mutual complementation of 2D ultrasonic diagnosis, M mode ultrasonic diagnosis and doppler ultrasonic diagnosis and mutual-section careful observation can decrease the missed diagnosis rate of ultrasonic diagnosis.%目的 探讨临床易漏诊的成人左室流出道狭窄的原因及声像图表现.方法 按常规扫查心脏,重点观察左室流出道、室壁厚度、二尖瓣运动曲线变化特点及左室流出道内血流动力学改变.结果 (1)狭窄的原因:室间隔基底部局部增厚导致狭窄的有26例;由粗大纤维腱索导致狭窄的有4例;室间隔基底部局部增厚合并假腱索导致狭窄的有2例.(2)共同的表现:左室壁均无明显增厚;左室流出道变窄;左室流出道狭窄处均探及高速血流信息;二尖瓣运动曲线均见CD段收缩期明显前向运动(SAM现象);合并主动脉瓣关闭不全19例.(3)狭窄漏诊原因:室间隔基底部的局部增厚只在某一切面而非所有切面显示;左室壁均无明显增厚;合并存在的主动脉瓣反流掩盖了左室流出道狭窄血流存在;由纤维腱索导致的狭窄易与肥厚性心肌病相混淆.结论 二维、M型、多普勒超声检查三者有机结合,多切面仔细观察,能够大幅减少超声检查的漏诊率.
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