Baumgartner H, Khan S S, DeRobertis M, Czer L S, Maurer G
Division of Cardiology and Cardiovascular Surgery, Cedars-Sinai Medical Center, Los Angeles.
Circulation. 1992 Jun;85(6):2275-83. doi: 10.1161/01.cir.85.6.2275.
Although Doppler echocardiography has been shown to be accurate in assessing stenotic orifice areas in native valves, its accuracy in evaluating the prosthetic valve orifice area remains undetermined.
Doppler-estimated valve areas were studied for their agreement with catheter-derived Gorlin effective orifice areas and their flow dependence in five sizes (19/20-27 mm) of St. Jude, Medtronic-Hall, and Hancock aortic valves using a pulsatile flow model. Doppler areas were calculated three ways: using the standard continuity equation; using its simplified modification (peak flow/peak velocity); and using the Gorlin equation with Doppler pressure gradients. The results were compared with Gorlin effective orifice areas derived from direct flow and catheter pressure measurements. Excellent correlation between Gorlin effective orifice areas and the three Doppler approaches was found in all three valve types (r = 0.93-0.99, SEE = 0.07-0.11 cm2). In Medtronic-Hall and Hancock valves, there was only slight underestimation by Doppler (mean difference, 0.003-0.25 cm2). In St. Jude valves, however, all three Doppler methods significantly underestimated effective orifice areas derived from direct flow and pressure measurements (mean difference, 0.40-0.57 cm2) with differences as great as 1.6 cm2. In general, the modified continuity equation calculated the largest Doppler areas. When orifice areas were calculated from the valve geometry using the area determined from the inner valve diameter reduced by the projected area of the opened leaflets, Gorlin effective orifice areas were much closer to the geometric orifice areas than Doppler areas (mean difference, 0.40 +/- 0.31 versus 1.04 +/- 0.20 cm2). In St. Jude and Medtronic-Hall valves, areas calculated by either technique did not show a consistent or clinically significant flow dependence. In Hancock valves, however, areas calculated by both the continuity equation and the Gorlin equation decreased significantly (p less than 0.001) with low flow rates.
Doppler echocardiography using either the continuity equation or Gorlin formula allows in vitro calculation of Medtronic-Hall and Hancock effective valve orifice areas but underestimates valve areas in St. Jude valves. This phenomenon is due to localized high velocities in St. Jude valves, which do not reflect the mean velocity distribution across the orifice. Valve areas are flow independent in St. Jude and Medtronic-Hall prostheses but decrease significantly with low flow in Hancock valves, suggesting that bioprosthetic leaflets may not open fully at low flow rates.
尽管多普勒超声心动图已被证明在评估天然瓣膜狭窄口面积方面具有准确性，但其在评估人工瓣膜口面积方面的准确性仍未确定。
使用脉动流模型，研究了五种尺寸（19/20 - 27毫米）的圣犹大、美敦力 - 霍尔和汉考克主动脉瓣的多普勒估计瓣膜面积与导管衍生的戈林有效口面积的一致性及其流量依赖性。多普勒面积通过三种方式计算：使用标准连续性方程；使用其简化修正版（峰值流量/峰值速度）；以及使用带有多普勒压力梯度的戈林方程。将结果与通过直接流量和导管压力测量得出的戈林有效口面积进行比较。在所有三种瓣膜类型中，戈林有效口面积与三种多普勒方法之间均发现了极好的相关性（r = 0.93 - 0.99，标准误 = 0.07 - 0.11平方厘米）。在美敦力 - 霍尔和汉考克瓣膜中，多普勒测量仅有轻微低估（平均差异为0.003 - 0.25平方厘米）。然而，在圣犹大瓣膜中，所有三种多普勒方法均显著低估了通过直接流量和压力测量得出的有效口面积（平均差异为0.40 - 0.57平方厘米），差异高达1.6平方厘米。总体而言，修正后的连续性方程计算出的多普勒面积最大。当使用从内瓣膜直径确定的面积减去打开瓣叶的投影面积来根据瓣膜几何形状计算口面积时，戈林有效口面积比多普勒面积更接近几何口面积（平均差异为0.40 ± 0.31平方厘米对1.04 ± 0.20平方厘米）。在圣犹大和美敦力 - 霍尔瓣膜中，两种技术计算出的面积均未显示出一致的或临床上显著的流量依赖性。然而，在汉考克瓣膜中，通过连续性方程和戈林方程计算出的面积在低流量时均显著减小（p < 0.001）。
使用连续性方程或戈林公式的多普勒超声心动图可在体外计算美敦力 - 霍尔和汉考克瓣膜的有效口面积，但会低估圣犹大瓣膜的口面积。这种现象是由于圣犹大瓣膜中存在局部高速，这不能反映整个口的平均速度分布。圣犹大和美敦力 - 霍尔人工瓣膜的口面积与流量无关，但汉考克瓣膜在低流量时口面积显著减小，这表明生物瓣叶在低流量时可能无法完全打开。
