Bech-Hanssen O, Caidahl K, Wallentin I, Ask P, Wranne B
Department of Clinical Physiology, Sahlgrenska University Hospital, Linköping University Hospital, Göteborg, Sweden.
J Thorac Cardiovasc Surg. 2001 Aug;122(2):287-95. doi: 10.1067/mtc.2001.115161.
We sought to evaluate the Doppler assessment of effective orifice area in aortic prosthetic valves. The effective orifice area is a less flow-dependent parameter than Doppler gradients that is used to assess prosthetic valve function. However, in vivo reference values show a pronounced spread of effective orifice area and smaller orifices than expected compared with the geometric area.
Using Doppler echocardiography, we studied patients who received a bileaflet St Jude Medical valve (n = 75; St Jude Medical, Inc, St Paul, Minn) or a tilting disc Omnicarbon valve (n = 46; MedicalCV, Incorporated, Inver Grove Heights, Minn). The prosthetic valves were also investigated in vitro in a steady-flow model with Doppler and catheter measurements in the different orifices. The effective orifice area was calculated according to the continuity equation.
In vivo, there was a wide distribution with the coefficient of variation (SD/mean x 100%) for different valve sizes ranging from 21% to 39% in the St Jude Medical valve and from 25% to 33% in the Omnicarbon valve. The differences between geometric orifice area and effective orifice area in vitro were 1.26 +/- 0.41 cm(2) for St Jude Medical and 1.17 +/- 0.38 cm(2) for Omnicarbon valves. The overall effective orifice areas and peak catheter gradients were similar: 1.35 +/- 0.37 cm(2) and 25.9 +/- 16.1 mm Hg for St Jude Medical and 1.46 +/- 0.49 cm(2) and 24.6 +/- 17.7 mm Hg for Omnicarbon. However, in St Jude Medical valves, more pressure was recovered downstream, 11.6 +/- 6.3 mm Hg versus 3.4 +/- 1.6 mm Hg in Omnicarbon valves (P =.0001).
In the patients, we found a pronounced spread of effective orifice areas, which can be explained by measurement errors or true biologic variations. The in vitro effective orifice area was small compared with the geometric orifice area, and we suspect that nonuniformity in the spatial velocity profile causes underestimation. The St Jude Medical and Omnicarbon valves showed similar peak catheter gradients and effective orifice areas in vitro, but more pressure was recovered in the St Jude Medical valve. The effective orifice area can therefore be misleading in the assessment of prosthetic valve performance when bileaflet and tilting disc valves are compared.
我们试图评估多普勒超声心动图对人工主动脉瓣膜有效瓣口面积的评估。有效瓣口面积是一个比多普勒压力阶差更不依赖流量的参数，用于评估人工瓣膜功能。然而，体内参考值显示有效瓣口面积分布范围很广，且与几何面积相比，瓣口面积小于预期。
我们使用多普勒超声心动图研究了接受双叶圣犹达医疗瓣膜（n = 75；圣犹达医疗公司，明尼苏达州圣保罗）或倾斜碟片全碳瓣膜（n = 46；MedicalCV公司，明尼苏达州因弗格罗夫海茨）的患者。还在体外稳态血流模型中对人工瓣膜进行了研究，在不同瓣口处进行了多普勒和导管测量。根据连续性方程计算有效瓣口面积。
在体内，不同瓣膜尺寸的变异系数（标准差/平均值×100%）分布范围较广，圣犹达医疗瓣膜为21%至39%，全碳瓣膜为25%至33%。体外几何瓣口面积与有效瓣口面积的差异，圣犹达医疗瓣膜为1.26±0.41 cm²，全碳瓣膜为1.17±0.38 cm²。总体有效瓣口面积和导管峰值压力阶差相似：圣犹达医疗瓣膜为1.35±0.37 cm²和25.9±16.1 mmHg，全碳瓣膜为1.46±0.49 cm²和24.6±17.7 mmHg。然而在圣犹达医疗瓣膜中，下游压力恢复更多，为11.6±6.3 mmHg，而全碳瓣膜为3.4±1.6 mmHg（P = 0.0001）。
在患者中，我们发现有效瓣口面积分布范围很广，这可能是由测量误差或真正的生物学变异所致。体外有效瓣口面积比几何瓣口面积小，我们怀疑空间速度分布不均匀导致了低估。圣犹达医疗瓣膜和全碳瓣膜在体外显示出相似的导管峰值压力阶差和有效瓣口面积，但圣犹达医疗瓣膜压力恢复更多。因此，在比较双叶瓣膜和倾斜碟片瓣膜时，有效瓣口面积在评估人工瓣膜性能时可能会产生误导。
