This registry aims to provide insights on the pathogenic mechanisms that expose subjects with CILCA arch to the increased risk of postoperative complications. So, the CILCA arch registry will capture clinical data and medical images of subjects with CILCA arch treated by surgical or endovascular (TEVAR) means.

Study Design: International Multicenter and Observational registry

Estimated Enrolment: 500 patients, with competitive enrolment.

Clinical Follow up: Postoperatively at 30 days, at 12 months, and yearly after.

The so-called "bovine" aortic arch (BAA) is characterized by the presence of a common origin of the innominate and left carotid artery, or, less frequently, by the origin of the left carotid directly from the innominate artery (i.e. type 2 BAA). In the present protocol, for brevity and according to the STROBE guidelines the investigators employed the acronym CILCA (common origin of the innominate and left carotid artery) arch, previously employed in publications of our group.

The CILCA is the second more common arch configuration, and its prevalence in the general population is 13.6%, with relevant differences among ethnic groups. However, the real prevalence of the CILCA is likely underestimated, because its presence is largely unreported due to the presumed clinical irrelevance of this anatomical variant. In fact, the peculiar anatomical features associated with the CILCA mandate specific management strategies and preoperative planning in both surgical and endovascular procedures involving the aortic arch, including type A aortic dissection repair and carotid stenting.

There is increasing evidence in the literature that the CILCA represents a potential determinant of the onset of thoracic aortic disease. Notably, it is associated with a 1.4-fold increased risk of developing aortic aneurysms or dissections, and this entails a relevant prevalence of this anatomical variant among patients requiring thoracic endovascular aortic repair (TEVAR). In fact, the CILCA presents a consistent and peculiar anatomical pattern compared with standard arch configuration, which provides relevant information for TEVAR planning, and may have prognostic implications.

This registry aims to provide insights on the pathogenic mechanisms that expose subjects with CILCA arch to the increased risk of postoperative complications. So, the CILCA arch registry will capture clinical data and medical images of subjects with CILCA arch treated by surgical or endovascular (TEVAR) means.

Technical and specific aims:

• Development of automatic segmentation of medical images for the assessment of geometric features by machine learning
• Assessment of a simplified method for the calculation of the "displacement forces" in proximal landing zones for TEVAR

Primary Endpoint: Identification of peculiar anatomical characteristics in patients with CILCA arch, before\after treatment of aortic pathologies (including both TEVAR and Open Repair).

Secondary Endpoint: Identification of anatomical risk factors for the postoperative clinical outcomes.

REGISTRY DESIGN International Multicenter and Observational clinical registry. Enrollment will include 500 patients with CILCA arch, treated with TEVAR or open repair. All patients will be followed up for 5 years, and their' clinical pathway and treatment strategy will be at discretion of the operator following current guidelines for thoracic aortic disease.

FOLLOW-UP PERIOD Postoperatively, patients will be followed-up for 5 years. This includes every medical check-up performed according to clinical practice (including telephone contacts) to obtain information regarding medical history, cardiovascular drugs use, hospitalizations, and adverse events, at 30 days, at 12 months, and yearly after. Repeated imaging (i.e. CT scan or magnetic resonance imaging) will be obtained according to current guidelines, or medical need.

STATISTICAL ANALYSIS All patients who are successfully registered will be included in the analysis. Being this an observational registry aiming to investigate the postoperative outcomes of patients with CILCA, the investigators proceeded without a formal power analysis. The number of patients scheduled to be enrolled (i.e. 500) was deemed adequate to provide robust evidence for future statistical analyses.

The study will be performed according to "good clinical practice ". The collection of personal, procedural and clinical data of patients must take place into the electronic CRF. Only the investigators and the personnel registered on the "Site Personnel Signature Log" will be granted access to the eCRF.

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Inclusion Criteria:

• Age ≥ 18 years old
• CILCA arch treated for an aortic disease (i.e. aortic dissection, aneurysm)

Exclusion Criteria:

• Contraindications to computed tomography (e.g. hypersensitivity to contrast media, renal failure);
• Suspected or manifested pregnancy

Subject with a CILCA and a thoracic cardiovascular disease requiring treatment. Both open cardiovascular repair and endovascular treatment (TEVAR) will be included.