Kim W Y, Bisgaard T, Nielsen S L, Poulsen J K, Pedersen E M, Hasenkam J M, Yoganathan A P
Department of Thoracic and Cardiovascular Surgery, Skejby Sygehus, Aarhus University Hospital, Denmark.
J Am Coll Cardiol. 1994 Aug;24(2):532-45. doi: 10.1016/0735-1097(94)90314-x.
This study investigated the velocity distribution across the natural mitral valve.
Information about the blood velocity distribution across the mitral valve is of interest in basic fluid dynamic studies of the natural mitral valve and is needed for precise cardiac output estimates by Doppler echocardiography.
The velocity distribution across the mitral valve was measured by epicardial Doppler echocardiography in ten 90-kg anesthetized pigs. By rotating the ultrasound transducer in 30 degrees intervals from the apical position, we constructed two-dimensional velocity profiles across the left ventricular inflow tract from diameters from each rotation arranged around a reference point. The time-averaged mitral velocity profile was calculated to estimate the error in cardiac output calculations that may occur with pulsed Doppler ultrasound when a single sample volume is used to record the mean velocity across the mitral orifice.
The time-averaged diastolic cross-sectional mitral velocity profiles at the level of the mitral annulus and leaflet tips were variably skewed because of the development of a large anterior vortex in the left ventricle during the deceleration of early diastolic inflow and atrial systole. The ratio of the time-velocity integral of the center sample volume to the spatially averaged time-velocity integral was 1.13 +/- 0.15 (mean +/- SD) (range 0.80 to 1.32). Using regression analysis, we found a correlation between the degree of nonuniformity of the cross-sectional velocity distribution and the peak velocity of the anterior vortex (r = 0.65, p < 0.01).
The assumption of a flat mean velocity profile across the mitral valve can introduce errors of +13 +/- 15% (mean +/- SD) in cardiac output measured with pulsed Doppler ultrasound when one is interrogating a single center sample volume.
本研究调查了天然二尖瓣上的速度分布情况。
二尖瓣上血流速度分布的信息在天然二尖瓣的基础流体动力学研究中具有重要意义，并且是通过多普勒超声心动图精确估算心输出量所必需的。
通过心外膜多普勒超声心动图测量了10头体重90千克的麻醉猪二尖瓣上的速度分布。从心尖位置开始，以30度间隔旋转超声换能器，我们根据围绕参考点排列的每次旋转的直径构建了左心室流入道的二维速度剖面。计算时间平均二尖瓣速度剖面，以估计当使用单个样本容积记录二尖瓣口平均速度时，脉冲多普勒超声在心输出量计算中可能出现的误差。
由于舒张早期流入和心房收缩减速期间左心室内出现大的前向涡流，二尖瓣环和瓣叶尖端水平的时间平均舒张期二尖瓣横截面速度剖面呈不同程度的倾斜。中心样本容积的时间速度积分与空间平均时间速度积分之比为1.13±0.15（平均值±标准差）（范围0.80至1.32）。通过回归分析，我们发现横截面速度分布的不均匀程度与前向涡流的峰值速度之间存在相关性（r = 0.65，p < 0.01）。
当使用脉冲多普勒超声询问单个中心样本容积时，假设二尖瓣上平均速度剖面呈平坦分布会在心输出量测量中引入+13±15%（平均值±标准差）的误差。
