Intravascular Ultrasound (IVUS) in Complex Aortic Endovascular Interventions

Thoracic Aortic Aneurysm

Intravascular ultrasound, bridging stentgraft, BEVAR, EVAR, IVUS

The study aims to investigate the applicability of intravascular ultrasound (IVUS) in the endovascular therapy of juxta-, supra- and thoracoabdominal aortic aneurysms. The focus of the study is on the intraoperative and postoperative evaluation of the geometric data of bridging stentgrafts in terms of patency, occurrence of stenosis and/or kinking.

Intravascular ultrasound (IVUS) is an already validated diagnostic method increasingly use in endovascular interventions. In contrast to conventional digital subtraction angiography (DSA), the IVUS provides in vivo real-time vessel images. Furthermore, its accuracy has been examined in histological studies, which could report of a good correlation regarding the vessel diameters (Jin ZG et al. Int J Cardiovasc Imaging. 2017 Feb; 33 (2): 153-160.). Stenosis and/or kinkings of stents or stentgrafts as well as their fully expansion and morphology can be assessed with the use of IVUS. The IVUS has already been used successfully in the context of endovascular treatment of infrarenal aortic aneurysms (Endovascular Aortic Repair or EVAR). Here, the IVUS has proven to be a valuable diagnostic instrument to examine the anatomy of the inserted stent grafts intraoperatively and to detect any abnormalities. In addition, the use of IVUS led to a significant reduction in the use of iodine-containing contrast media and radiation exposure as part of these complex endovascular interventions (Pecoraro F et al. Ann Vasc Surg. 2019 Apr; 56: 209-215.). In the endovascular therapy of thoracoabdominal as well as suprarenal and juxtarenal aortic aneurysms, stent grafts with recesses (windows - Fenestrated EVAR or FEVAR) or side arms (branches - Branched EVAR or BEVAR) for the renovisceral vessels (truncus coeliacus, superior mesenteric artery and renal arteries) are implanted. In exceptional cases, the renovisceral vessels are supplied with stent grafts that are implanted in parallel to the aortic stent grafts (Chimney-Technique). These branches or windows are then connected to the corresponding target vessels via a bridging stent graft. The patency and anatomy of the bridging stent grafts are usually checked intraoperatively by angiography. The dynamics of the contrast agent flow and the X-ray images of the framework of the stent graft help in assessing their patency as well as the absence of structural problems. The Computed Tomographic Angiography (CTA) is considered the gold standard as diagnostic method to assess the patency and anatomy of the stentgrafts postoperatively. This diagnostic method bares with it the exposure to relevant radiation dose as well as to contrast media. However, CTA scans do not provide in vivo real-time vessel images. Furthermore, in case of pathological findings a new intervention may be necessary. The IVUS technique overcomes these issues due to its low invasiveness and its possible use during the index procedure. This can lead to the immediate identification of eventual structural problems of the bridging stent grafts which can jeopardize their patency and to correct them already during the index procedure. The use of the IVUS during FEVAR, BEVAR and CHEVAR has already been implemented in our clinical routine. At our knowledge, a prospective collection of anatomical-geometric data by IVUS in complex endovascular treatments of complex aortic aneurysm has not been yet reported. The aim of the current study is the retrospective evaluation of the anatomical-geometric data already collected by IVUS as well as the prospective collection of new data regarding the patency and anatomy of bridging stent grafts.

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