Endovascular management of thoracic aortic aneurysms. Preoperative imaging and device sizing

Three-dimensional reconstruction of computed tomography scans is invaluable in permitting accurate measurements of thoracic aorta aneurysms. Length measurements are optimized; however, lumen diameters are best measured directly from transverse slices.

A typical sizing diagram for sizing of the descending thoracic aorta. A minimum of 6 diameters are used to characterize the proximal and distal landing zones. For the Gore Tag device, these are lumen-to-lumen measurements, not adventitial-to-adventitial measurements. Consequently appropriate sizing requires a contrast-enhanced computed tomography scan, angiogram, or intravascular ultrasound. A, Proximal implantation site; B, 1 cm from proximal implantation site; C, 2 cm from proximal implantation site; D, aneurysm; E, 2 cm from distal implantation site; F, 1 cm from proximal implantation site; G, distal implantation site; H, right common iliac artery; I, left common iliac artery; J, right external iliac/femoral; K, left external iliac/femoral; L, proximal neck, distance from aneurysm to left subclavian or carotid arteries; M, aneurysm length; N, distal neck, distance from aneurysm to celiac axis; O, total treatment length; P, proximal angle; Q, distal angle.

Sizing chart for the W. L. Gore Thoracic Aneurysm Graft (TAG).

A, Measure the length of the aneurysm using angiography with marker catheter present. B, Measure the maximum lumen-to-lumen diameter using computed tomography.

Diameter measured in angled necks as shown by aortogram and computed tomography (CT) scan: measure the smaller width of the ellipse.

Compensating for tortuosity at landing zones: Use more than 2 cm of neck if available and appropriate. More than 2 cm of neck is recommended when a severe angle exists (<60° angle).