Terasawa Y, Tanaka M, Konno K, Niita K, Kashiwagi M
Jpn Heart J. 1977 Sep;18(5):652-63. doi: 10.1536/ihj.18.652.
In order to examine the production mechanism of the midsystolic click in cases of a midsystolic click and a late systolic murmur, the relationship between the click and the motion of the mitral apparatus was studied by means of ultrasono-cardiotomography and the simultaneous recording of phonocardiograms and ultrasono-cardiograms (UCGs). It was found that the systolic click occurred in exact coincidence with the time at which the hump of the echo of the unusual early systolic anterior motion (early SAM) took its backmost position. This coincidence was found when the click was shifted either by postural changes or inhalation of amyl nitrite. The present ultrasono-cardiotomographic study demonstrated that the echo source of the early SAM could be attributed to the protrusion into the left ventricular outflow tract of the slackened elongated chordae tendineae in systole. The anterior leaflet moved suddenly to the position of maximal prolapse when the slackened chordae tendineae were stretched taut in midsystole. In other words, the midsystolic click occurred when the anterior leaflet prolapsed and the tension exerted on the chordae tendineae was at its maximum.
为了研究收缩中期喀喇音及收缩晚期杂音病例中收缩中期喀喇音的产生机制，通过超声心动断层摄影术以及心音图和超声心动图（UCG）的同步记录，研究了喀喇音与二尖瓣装置运动之间的关系。研究发现，收缩期喀喇音与异常的收缩期早期前向运动（早期SAM）回声驼峰到达其最后位置的时间完全一致。当喀喇音因体位改变或吸入亚硝酸异戊酯而发生移位时，也发现了这种一致性。目前的超声心动断层摄影研究表明，早期SAM的回声源可归因于收缩期松弛延长的腱索突入左心室流出道。当中期收缩期松弛的腱索被拉紧时，前叶突然移动到最大脱垂位置。换句话说，收缩中期喀喇音发生在前叶脱垂且腱索上的张力达到最大值时。
