Oshinski J N, Parks W J, Markou C P, Bergman H L, Larson B E, Ku D N, Mukundan S, Pettigrew R I
Department of Radiology, Emory University School of Medicine, Atlanta, Georgia 30322, USA.
J Am Coll Cardiol. 1996 Dec;28(7):1818-26. doi: 10.1016/S0735-1097(96)00395-6.
This study evaluated whether magnetic resonance imaging (MRI) and magnetic resonance (MR) phase velocity mapping could provide accurate estimates of stenosis severity and pressure gradients in aortic coarctation.
Clinical management of aortic coarctation requires determination of lesion location and severity and quantification of the pressure gradient across the constricted area.
Using a series of anatomically accurate models of aortic coarctation, the laboratory portion of this study found that the loss coefficient (K), commonly taken to be 4.0 in the simplified Bernoulli equation delta P = KV2, was a function of stenosis severity. The values of the loss coefficient ranged from 2.8 for a 50% stenosis to 4.9 for a 90% stenosis. Magnetic resonance imaging and MR phase velocity mapping were then used to determine coarctation severity and pressure gradient in 32 patients.
Application of the new severity-dependent loss coefficients found that pressure gradients deviated from 1 to 17 mm Hg compared with calculations made with the commonly used value of 4.0. Comparison of MR estimates of pressure gradient with Doppler ultrasound estimates (in 22 of 32 patients) and with catheter pressure measurements (in 6 of 32 patients) supports the conclusion that the severity-based loss coefficient provides improved estimates of pressure gradients.
This study suggests that MRI could be used as a complete diagnostic tool for accurate evaluation of aortic coarctation, by determining stenosis location and severity and by accurately estimating pressure gradients.
本研究评估磁共振成像（MRI）和磁共振（MR）相速度映射是否能准确估计主动脉缩窄的狭窄严重程度和压力梯度。
主动脉缩窄的临床管理需要确定病变位置和严重程度，并量化狭窄区域两端的压力梯度。
利用一系列解剖结构精确的主动脉缩窄模型，本研究的实验室部分发现，简化伯努利方程ΔP = KV²中通常取为4.0的损失系数（K）是狭窄严重程度的函数。损失系数的值范围从50%狭窄时的2.8到90%狭窄时的4.9。然后使用磁共振成像和MR相速度映射来确定32例患者的缩窄严重程度和压力梯度。
应用新的与严重程度相关的损失系数发现，与使用常用值4.0进行的计算相比，压力梯度偏差为1至17 mmHg。将MR压力梯度估计值与多普勒超声估计值（32例患者中的22例）以及导管压力测量值（32例患者中的6例）进行比较，支持了基于严重程度的损失系数能更好地估计压力梯度这一结论。
本研究表明，MRI可通过确定狭窄位置和严重程度以及准确估计压力梯度，用作准确评估主动脉缩窄的完整诊断工具。
