Although open repair is traditionally pursued for proximal aorta pathology, endovascular stent grafting is possible in certain cases of type A dissection and proximal thoracic aortic aneurysm. A 2011 study demonstrated a 98% technical success rate for TEVAR in the treatment of 45 patients with type A dissection in which the entry tear was at least 2.5 cm from the coronary ostia [52]. Notably, transposition of the supra-aortic vessels was necessary in nearly half of the patients in this study to ensure an adequate landing zone. Other authors recommend a minimum distance of 1 cm from the intimal tear entry site to the sinotubular junction and brachiocephalic trunk [11]. CTA is essential in planning for these cases to avert compromise of coronary and brachiocephalic circulation as well as aortic valve dysfunction. An essential aspect of pre-TEVAR planning is evaluation of the iliofemoral vasculature. Thoracic aorta endografts tend to be larger than their abdominal counterparts, requiring insertion sheaths with outer diameters up to 27 French. For this reason, a minimum vessel diameter of at least 8 to 9 mm is preferred [25,26]. Additionally, increased vessel depth, degree of femoral artery calcification, and iliofemoral tortuosity have been shown to be negative predictors of percutaneous TEVAR success [24]. All of these variables are readily evaluable with CTA and, in conjunction with sound clinical judgment, can be used to avoid the dreaded complication of iliac disruption necessitating open surgical repair. In cases of unfavorable anatomy, surgical or endovascular conduits have been shown to reliably facilitate endovascular repair [53]. The radiation dose associated with properly performed CT examinations in the evaluation of thoracic aortic disease is not of significant concern [54].
Thoracic Aortic Aneurysm or Dissection Treatment Planning and Follow Up. Although open repair is traditionally pursued for proximal aorta pathology, endovascular stent grafting is possible in certain cases of type A dissection and proximal thoracic aortic aneurysm. A 2011 study demonstrated a 98% technical success rate for TEVAR in the treatment of 45 patients with type A dissection in which the entry tear was at least 2.5 cm from the coronary ostia [52]. Notably, transposition of the supra-aortic vessels was necessary in nearly half of the patients in this study to ensure an adequate landing zone. Other authors recommend a minimum distance of 1 cm from the intimal tear entry site to the sinotubular junction and brachiocephalic trunk [11]. CTA is essential in planning for these cases to avert compromise of coronary and brachiocephalic circulation as well as aortic valve dysfunction. An essential aspect of pre-TEVAR planning is evaluation of the iliofemoral vasculature. Thoracic aorta endografts tend to be larger than their abdominal counterparts, requiring insertion sheaths with outer diameters up to 27 French. For this reason, a minimum vessel diameter of at least 8 to 9 mm is preferred [25,26]. Additionally, increased vessel depth, degree of femoral artery calcification, and iliofemoral tortuosity have been shown to be negative predictors of percutaneous TEVAR success [24]. All of these variables are readily evaluable with CTA and, in conjunction with sound clinical judgment, can be used to avoid the dreaded complication of iliac disruption necessitating open surgical repair. In cases of unfavorable anatomy, surgical or endovascular conduits have been shown to reliably facilitate endovascular repair [53]. The radiation dose associated with properly performed CT examinations in the evaluation of thoracic aortic disease is not of significant concern [54].