AN ECHOCARDIOGRAPHIC STUDY OF THE FLUID-MECHANICS OF OBSTRUCTION IN HYPERTROPHIC CARDIOMYOPATHY
AN ECHOCARDIOGRAPHIC STUDY OF THE FLUID-MECHANICS OF OBSTRUCTION IN HYPERTROPHIC CARDIOMYOPATHY
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DOI：
10.1016/0735-1097(93)90196-8
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发表时间：
1993-09-01
影响因子：
24
通讯作者：
DWYER, EM
中科院分区：
文献类型：
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作者：
SHERRID, MV;CHU, CK;DWYER, EM
目标。本研究的目的是探讨肥厚型心肌病患者二尖瓣-间隔接触和梗阻的流体力学原因。二尖瓣间隔对置是肥厚型心肌病患者梗阻的原因。在有阻塞的情况下，特征的连续波多普勒道显示血流的加速增加。(描边向左凹。)方法。我们研究了24名连续的患者，他们的多普勒超声心动图压力梯度大于或等于36毫米汞。我们追查了两条线索。1)在梗阻发生前，系统测量收缩早期左心室彩色血流方向与突出的二尖瓣叶的夹角。2)在梗阻发作后，我们对患者的连续波多普勒波轨迹的凹形轮廓进行了定性的分析，并提出了梗阻时相的流体力学理论来解释这些特征轨迹。我们提出了一个数学模型来支持这一概念。我们测量了129个角度。在二尖瓣-间隔接触之前，凸出的二尖瓣叶在心尖长轴和心尖五腔切面上分别以平均40度和45度的角度投影。在二尖瓣-间隔接触处，阻塞叶在同一个不同的切面上相对于血流平均突出52度和58度。甚至在收缩早期，在瓣叶粘合时，23例患者中有11例与血流成15度角。二尖瓣-间隔对位后，穿过帽状开口的梗阻开始。在这一阶段，阻塞的小叶相对于流动平均以55度和63度的角度伸出。在22例患者中，连续波多普勒示左室流出道血流速度增加。就在二尖瓣-间隔接触之前，凸出的小叶相对于血流以高角度突出。在这些高角度下，流动阻力，即流动的推动力，是对突出的小叶的主要流体动力，似乎是阻塞的直接原因。流动方向与凸出的小叶之间的高度夹角排除了显著的文丘里效应。甚至在收缩早期，在叶粘合时，一半患者的血流阻力占主导地位，与血流成15度角。在阻塞被触发后，从我们的数据和模型中可以看出，小叶是由于通过开口的压力差而被压向隔膜的。多普勒血流加速度的增加可以用一个随时间变化的放大反馈回路来解释，在该回路中，小孔的压差升高会导致小孔和大的压差。
Objectives. The goal of this study was to investigate the hydrodynamic cause of mitral-septal contact and obstruction in patients with hypertrophic cardiomyopathy.Background. Mitral-septal apposition has been shown to be the cause of obstruction in patients with hypertrophic cardiomyopathy. With obstruction, characteristic continuous wave Doppler tracings show an increasing acceleration of flow. (Tracing is concave to the left.)Methods. We studied 24 consecutive patients who had a Doppler echocardiographic pressure gradient greater-than-or-equal-to 36 mm Hg. We pursued two lines of inquiry. 1) Before the onset of obstruction, we systematically measured the angle between the direction of left ventricular Doppler color flow and the protruding mitral leaflet in early systole. 2) After the onset of obstruction, we qualitatively analyzed the concave contour of the continuous wave Doppler tracings in our patients and developed a hydrodynamic theory of the obstruction phase to explain the characteristic tracings. We present a mathematic model to support this concept.Results. We measured 129 angles. Just before mitral-septal contact, the protruding mitral leaflet projects at a mean 40-degrees and 45-degrees relative to flow in the apical long-axis and apical five-chamber views, respectively. At mitral-septal contact, the obstructing leaflet projects at a mean 52-degrees and 58-degrees relative to flow in the same respective views. Even very early in systole, at leaflet coaptation, 11 of 23 patients had angles >15-degrees relative to flow. After mitral-septal apposition, obstruction across a cowl-shaped orifice begins. During this stage, the obstructing leaflet projects at a mean 55-degrees and 63-degrees relative to flow. In 22 patients, the continuous wave Doppler tracing of the left ventricular outflow jet showed an increasing acceleration of flow.Conclusions. Just before mitral-septal contact, the protruding leaflets project at high angles relative to flow. At these high angles, flow drag, the pushing force of flow, is the dominant hydrodynamic force on the protruding leaflet and appears to be the immediate cause of obstruction. The high angle between flow direction and the protruding leaflet precludes significant Venturi effects. Even earlier in systole, at leaflet coaptation, flow drag is dominant in half of the patients, with angles relative to flow >15-degrees. After obstruction is triggered, it appears from our data and model that the leaflet is forced against the septum by the pressure difference across the orifice. The increasing acceleration of Doppler flow is explained by a time-dependent amplifying feedback loop in which the rising pressure difference across the orifice leads to a smaller orifice and a higher pressure difference.