Ultrasono-cardiotomography showed the midsystolic click occurs when the anterior mitral leaflet prolapses and tension on the slackened, elongated chordae tendineae is at its maximum.
Case Report (n=1)
No
What is the mechanism of production of the midsystolic click in patients with a prolapsed mitral valve?
The midsystolic click in mitral valve prolapse is caused by the sudden tensing of slackened, elongated chordae tendineae as the anterior leaflet reaches its maximal prolapse.
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.
Terasawa et al. (Sat,) conducted a case report in Prolapsed mitral valve (n=1). Ultrasono-cardiotomography and simultaneous phonocardiography was evaluated on Timing and mechanism of the midsystolic click. Ultrasono-cardiotomography showed the midsystolic click occurs when the anterior mitral leaflet prolapses and tension on the slackened, elongated chordae tendineae is at its maximum.