A Standard Carbon Dioxide Flushing Protocol to Reduce Air Embolization During Thoracic Endovascular Aortic Repair

FlushTEVAR is a non-profit, interventional, randomized, controlled, single-blind, national multicenter study promoted by the University of Bologna and coordinated by the Vascular Surgery Unit of IRCCS Azienda Ospedaliero-Universitaria di Bologna, Policlinico di Sant'Orsola, under the direction of Prof. Mauro Gargiulo, who also serves as Principal Investigator. The study aims to develop and evaluate a pre-implant thoracic endograft flushing technique using carbon dioxide (CO₂) to reduce periprocedural embolic events and cerebral infarctions in patients undergoing Thoracic Endovascular Aortic Repair (TEVAR). TEVAR is currently the treatment of choice for acute aortic syndromes and aneurysms involving the descending thoracic aorta. Despite its widespread use, TEVAR remains associated with significant neurological complications, with an incidence ranging from 3% to 8% in standard procedures and reaching up to 16% in more complex endovascular interventions. Cerebral embolization caused by solid and gaseous particles is considered the main cause of perioperative stroke and silent brain infarction (SBI), the latter being defined as ischemic brain injury detected by neuroradiological imaging in the absence of immediate clinical symptoms. During TEVAR, approximately 90% of microembolic signals detected in the middle cerebral artery are caused by gaseous emboli, with the highest number occurring during endograft deployment. This phenomenon is associated with the manufacturing and sterilization processes of endografts, during which gas microparticles become trapped between the endograft and its delivery system and are subsequently released into the bloodstream when the device is deployed at the intended aortic site. The primary objective of the study is to assess the difference in the incidence of major neurological events, including stroke and transient ischemic attack (TIA), as well as silent brain infarctions, between patients whose endografts undergo a standardized pre-implant flushing protocol with CO₂ followed by conventional saline flushing, and patients receiving standard saline flushing alone. Major neurological events will be assessed clinically, while silent brain infarctions will be evaluated using study-specific diffusion-weighted magnetic resonance imaging (DW-MRI) of the brain performed within 72 hours after the procedure. A total of 90 patients will be enrolled across four participating centers and randomized in a 1:1 ratio after providing informed consent. Forty-five patients will be allocated to the experimental arm and treated with CO₂ flushing before the standard saline flushing procedure during TEVAR, while forty-five patients will be allocated to the control arm and will receive standard saline flushing only. Eligible patients must be at least 18 years of age and present with type B acute aortic syndrome in the acute, subacute, or chronic phase, or thoracic and thoracoabdominal aneurysms with Crawford extent I, II, III, or IV. Written informed consent is required for participation. Patients will be excluded if the procedure is performed using CO₂ angiography, if endografts without a sheath are used, if emergency endovascular treatment is required, if they have experienced a stroke or TIA within the previous six months, if the proximal sealing zone is 0 or 1, if any contraindication to DW-MRI is present, or in cases of pregnancy or breastfeeding. At study completion, the two treatment groups will be compared on the basis of diffusion-weighted brain MRI findings. The primary endpoint is the number of silent brain infarctions and the determination of whether a statistically significant difference exists between the CO₂ flushing group and the saline flushing group. The safety of the procedure will be evaluated through both technical and clinical success. The planned study duration is three years, and postoperative rates of SBI and TIA/stroke will be compared between groups using Fisher's and Pearson's chi-square tests.