Stein P D, Sabbah H N, Magilligan D J, Lakier J B
Am J Cardiol. 1982 Jun;49(8):1874-82. doi: 10.1016/0002-9149(82)90205-3.
The cause of a musical (cooing) murmur produced by a degenerated bioprosthetic valve in the mitral position was investigated. Spectral analysis of the murmur recorded at the chest wall at the site of the maximum palpable impulse showed virtually all sound in a narrow frequency band around the dominant frequency of 158 hertz. The same valve, surgically removed and mounted in the mitral position in a pulse duplicating system, produced an audible musical murmur detected by a phonocatheter in the atrial chamber. Nearly all of the sound-pressure occurred in a narrow band of frequency around 145 hertz. High speed motion pictures (500 frames/s) showed systolic flutter of a flail leaflet. The frequency of this leaflet flutter was 142 hertz. Hot film anemometry showed minimal turbulence, all located near the margin of the regurgitant leaflet. The intensity of the murmur was unrelated to the intensity of turbulence. A second degenerated bioprosthetic valve that produced in vivo a typical blowing holosystolic mitral regurgitant murmur produced in vitro a murmur with a broad range of frequencies (20 to 500 hertz). With this valve, the intensity of the murmur was related to the intensity of the turbulence. Motion pictures showed no leaflet flutter. Flutter of an insufficient valve leaflet causing uniform and periodic high frequency fluctuating pressures therefore appeared to be the cause of the musical quality of the systolic murmur in a degenerated bioprosthetic valve.
对二尖瓣位生物瓣退变产生的乐音（咕咕样）杂音的病因进行了研究。在胸壁可触及最强搏动处记录的杂音频谱分析显示，几乎所有声音都集中在主频158赫兹附近的一个窄频带内。同一瓣膜经手术切除后安装在脉搏复制系统的二尖瓣位，心房内的导管可检测到可闻及的乐音性杂音。几乎所有声压都出现在145赫兹附近的一个窄频带内。高速电影（500帧/秒）显示连枷瓣叶的收缩期扑动。该瓣叶扑动频率为142赫兹。热膜风速测量显示湍流极小，均位于反流瓣叶边缘附近。杂音强度与湍流强度无关。第二个退变生物瓣在体内产生典型的全收缩期吹风样二尖瓣反流杂音，在体外产生频率范围较宽（20至500赫兹）的杂音。对于这个瓣膜，杂音强度与湍流强度有关。电影显示无瓣叶扑动。因此，功能不全的瓣叶扑动导致均匀且周期性的高频波动压力，似乎是退变生物瓣收缩期杂音具有乐音性质的原因。
