Baumgartner H, Schima H, Tulzer G, Kühn P
2nd Department of Internal Medicine/Cardiology, Krankenhaus der Barmherzigen Schwestern, Linz, Austria.
J Am Coll Cardiol. 1993 Mar 15;21(4):1018-25. doi: 10.1016/0735-1097(93)90362-5.
This study investigated the effect of stenosis geometry on the Doppler-catheter gradient relation.
Although gradient estimation by Doppler ultrasound has been shown to be accurate in various clinical and in vitro settings, there have also been reports of substantial discrepancies between Doppler and catheter gradients. These conflicting results may be due to differences in geometry and hemodynamic characteristics of flow obstructions.
Stenoses of various geometry were simultaneously studied with continuous wave Doppler and catheter technique in a well controlled pulsatile flow model.
Doppler and catheter gradients correlated very well regardless of stenosis geometry and site of distal catheter measurement (r = 0.98 to 0.99, SEE = 1.8 to 5.3 mm Hg). When the catheter was pulled back through the stenosis, the highest gradients were found in or close to the stenosis. When these catheter gradients were compared with Doppler gradients, the agreement between the two techniques was excellent regardless of stenosis geometry (slope 0.97; mean difference 0.6 +/- 2.0 mm Hg). However, when distal pressures were measured 10 cm downstream from the stenotic segment, the slope of the regression line, and therefore the agreement between Doppler and catheter gradients, differed for the different stenosis types (slopes from 0.98 to 1.69). In stenoses with abrupt narrowing and abrupt expansion, agreement was acceptable. Doppler gradients were only slightly greater than catheter gradients (mean difference 4.5 +/- 5.2 mm Hg). In stenoses with a gradually tapering inlet and outlet, the Doppler-catheter gradient relation was dependent on the outflow angle. Good agreement was found for an angle of 60 degrees (mean difference 0.6 +/- 1.8 mm Hg). In stenoses with a 40 degrees outflow angle, Doppler gradients exceeded the catheter gradients by 13% on average; for stenoses with a 20 degrees outflow angle, Doppler gradients exceeded catheter gradients by 46 +/- 11.4%, with differences as great as 65 mm Hg. These results were identical for stenoses gradually tapering outward to the distal tubing diameter and those with abrupt expansion after 2 cm of gradual expansion. The results were also not affected by changing the inflow angle from 20 degrees to 60 degrees. However, an abrupt narrowing instead of a tapering inlet significantly altered the Doppler-catheter gradient relation (p < 0.001); Doppler gradients exceeded the catheter gradients by 34 +/- 10% for this stenosis type.
Doppler gradients accurately reflect the highest gradients across flow obstructions that occur in the vena contracta. However, these gradients may be significantly greater than catheter gradients that are measured farther downstream, as is usually the case in clinical catheterization studies. These discrepancies are due to pressure recovery. The magnitude of pressure recovery is highly dependent on the stenosis geometry, which therefore significantly affects the Doppler-catheter gradient relation. It is the outflow geometry that predominantly influences this relation, but the shape of the inlet may affect the results as well. Although pressure recovery occurs even in stenoses with abrupt narrowing and abrupt expansion, the phenomenon is most likely to become clinically relevant in stenoses with a gradually tapering inlet and outlet with an outflow angle < or = 20 degrees.
本研究调查狭窄几何形状对多普勒导管压力阶差关系的影响。
尽管在各种临床和体外环境中，多普勒超声估计压力阶差已被证明是准确的，但也有报道称多普勒和导管压力阶差之间存在显著差异。这些相互矛盾的结果可能是由于血流梗阻的几何形状和血流动力学特征不同所致。
在一个控制良好的搏动血流模型中，采用连续波多普勒和导管技术同时研究了各种几何形状的狭窄。
无论狭窄的几何形状和导管远端测量部位如何，多普勒和导管压力阶差的相关性都非常好（r = 0.98至0.99，标准误 = 1.8至5.3 mmHg）。当导管通过狭窄部位回撤时，最高压力阶差出现在狭窄处或其附近。当将这些导管压力阶差与多普勒压力阶差进行比较时，无论狭窄的几何形状如何，两种技术之间的一致性都非常好（斜率0.97；平均差异0.6±2.0 mmHg）。然而，当在狭窄段下游10 cm处测量远端压力时，回归线的斜率以及多普勒和导管压力阶差之间的一致性在不同类型的狭窄中有所不同（斜率从0.98至1.69）。在狭窄处突然变窄和突然扩张的情况下，一致性是可以接受的。多普勒压力阶差仅略大于导管压力阶差（平均差异4.5±5.2 mmHg）。在入口和出口逐渐变细的狭窄中，多普勒 - 导管压力阶差关系取决于流出角度。在60度角时一致性良好（平均差异0.6±1.8 mmHg）。在流出角度为40度的狭窄中，多普勒压力阶差平均比导管压力阶差高13%；在流出角度为20度的狭窄中，多普勒压力阶差比导管压力阶差高46±11.4%，差异高达65 mmHg。对于逐渐向外变细至远端管径的狭窄以及在逐渐扩张2 cm后突然扩张的狭窄，这些结果是相同的。结果也不受流入角度从20度变为60度的影响。然而，突然变窄而不是逐渐变细的入口会显著改变多普勒 - 导管压力阶差关系（p < 0.001）；对于这种狭窄类型，多普勒压力阶差比导管压力阶差高34±10%。
多普勒压力阶差准确反映了在狭窄处出现的跨血流梗阻的最高压力阶差。然而，这些压力阶差可能比通常在临床导管检查研究中在更远端测量的导管压力阶差显著更大。这些差异是由于压力恢复。压力恢复的程度高度依赖于狭窄的几何形状，因此显著影响多普勒 - 导管压力阶差关系。主要影响这种关系的是流出几何形状，但入口的形状也可能影响结果。尽管即使在狭窄处突然变窄和突然扩张的情况下也会发生压力恢复，但这种现象在入口和出口逐渐变细且流出角度≤20度的狭窄中最有可能具有临床相关性。
