Cosset Benoit, Boussel Loic, Davila Serrano Eduardo, Millon Antoine, Douek Philippe, Farhat Fadi, Sigovan Monica
University Lyon 1, INSA Lyon, UCBL 1, CNRS, Inserm, CREATIS UMR 5220, Lyon, France.
Department of Cardio-Vascular Surgery, Hospices Civils de Lyon, Lyon, France.
Front Cardiovasc Med. 2022 May 25;9:873144. doi: 10.3389/fcvm.2022.873144. eCollection 2022.
The standard treatment for complicated Stanford type B aortic dissection (TBAD) is thoracic endovascular aortic repair (TEVAR). Functional parameters, specifically blood flow, are not measured in the clinical assessment of TEVAR, yet they are of outmost importance in patient outcome. Consequently, we investigated the impact of TEVAR on the flows in the aorta and its branches in TBAD using 4D Phase-Contrast Magnetic Resonance Imaging (4D Flow MRI).
Seven patients with TBAD scheduled for TEVAR underwent pre and post-operative 4D Flow MRI. An experienced reader assessed the presence of helical flow in the false lumen (FL) using streamlines and measured net flow at specific locations. In addition, forward and reverse flows, stasis, helicity, and absolute helicity were computed automatically along the aorta centerline. Average values were then computed in the segmented vessels. Impact of TEVAR on these parameters was assessed with a Wilcoxon signed rank test. Impact of the metallic stent on the velocity quantification was assessed using intra-class correlation coefficient (ICC) between velocities measured intra-stent and in adjacent stent-free regions.
FL helical flow was observed proximally in 6 cases and distally in 2 cases pre-operatively. Helical flow disappeared post-TEVAR proximally, but developed distally for 2 patients. Intra-stent measures were similar to stent-free with a median difference of 0.1 L/min and an ICC equal to 0.967 ( < 0.01). Forward flow increased from 59.9 to 81.6% in the TL and significantly decreased in the FL from 15.9 to 3.3%. Similarly, reverse flow increased in the TL from 4.36 to 10.8% and decreased in the FL from 10.3 to 4.6%. No significant changes were observed in net flow for aortic branches ( > 0.05). A significant increase in FL stasis was observed ( = 0.04).
TEVAR significantly increased forward flow in the TL and significantly decreased both forward and reverse flows in the FL. Interestingly, reverse flow in the TL increased post-TEVAR, which could be due to increased rigidity of the wall, due to the metallic stent. User independent helicity quantification enabled detection of elevated helicity at the level of secondary entry tears which had been missed by streamline visualization.
复杂型B型主动脉夹层（TBAD）的标准治疗方法是胸主动脉腔内修复术（TEVAR）。在TEVAR的临床评估中未测量功能参数，特别是血流，但它们对患者预后至关重要。因此，我们使用四维相位对比磁共振成像（4D Flow MRI）研究了TEVAR对TBAD患者主动脉及其分支血流的影响。
7例计划接受TEVAR治疗的TBAD患者在术前和术后接受了4D Flow MRI检查。一位经验丰富的阅片者使用流线评估假腔（FL）中螺旋血流的存在，并在特定位置测量净血流。此外，沿着主动脉中心线自动计算正向和反向血流、血流停滞、螺旋度和绝对螺旋度。然后在分割的血管中计算平均值。使用Wilcoxon符号秩检验评估TEVAR对这些参数的影响。使用支架内和相邻无支架区域测量的速度之间的组内相关系数（ICC）评估金属支架对速度量化的影响。
术前在6例患者的近端和2例患者的远端观察到FL螺旋血流。TEVAR术后近端螺旋血流消失，但2例患者的远端出现螺旋血流。支架内测量值与无支架测量值相似，中位数差异为0.1 L/min，ICC等于0.967（<0.01）。真腔（TL）中的正向血流从59.9%增加到81.6%，假腔中的正向血流从15.9%显著降低到3.3%。同样，TL中的反向血流从4.36%增加到10.8%，FL中的反向血流从10.3%降低到4.6%。主动脉分支的净血流未观察到显著变化（>0.05）。观察到FL血流停滞显著增加（=0.04）。
TEVAR显著增加了TL中的正向血流，并显著降低了FL中的正向和反向血流。有趣的是，TEVAR术后TL中的反向血流增加，这可能是由于金属支架导致管壁刚度增加所致。用户独立的螺旋度量化能够检测到二级入口撕裂水平处升高的螺旋度，而流线可视化则未发现。
