The imaging assessment and specific endograft design for the endovascular repair of ascending aortic dissection

Abstract

Background: Endovascular option has been proposed for a very limited and selected number of Stanford type A aortic dissection (TAAD) patients. We have performed a computed tomography (CT)-based TAAD study to explore appropriate endograft configurations for the ascending aortic pathology.

Methods: TAAD patients treated with optimal CT scans were retrospectively reviewed, and their entry tears (ETs) were identified using three-dimensional and multiplanar reconstructions in an EndoSize workstation. After generating a centerline of flow, measurements, including numerous morphologic characteristics of anatomy, were evaluated and a selected subset of patients were determined to be suitable for endovascular treatments. Proximal diameter and distal diameter of endograft were selected based on diameters measured at the ET level and at the innominate artery (IA) level, with 10% oversizing with respect to the true lumen, but not exceeding the original aortic diameter. The length of the endograft was determined by the distance from the sinotubular junction to IA.

Results: This study covered 126 TAAD patients with primary ET in ascending aorta, among which, according to the assumed criteria, 48 (38.1%) patients were deemed to be suitable for endovascular treatment. The diameters of ascending aorta from the sinotubular junction to the IA level presented a downward trend, and the proximal diameters differed significantly from distal diameters of the endograft for TAAD (39.9 versus 36.2 mm, P<0.01), implying that the conical endograft might be compatible with the ascending pathology. In the ascending aorta, lengths of the endograft should be 50, 60, 70, 80, and 90 mm in five (10.4%), 22 (45.9%), 13 (27.1%), six (12.5%), and two (4.2%) patients, respectively.

Conclusion: In this selected number of Chinese patients, the suitability of endovascular repair has been demonstrated based on the CT imaging. Shorter, larger, and bare spring-free conical endografts were preferred in the ascending aortic pathology.

Keywords: design; endograft; endovascular; type A dissection.

Figure 1

The origin of the axis indicates defined location of intimal tear. Note: The presence of a region of intimal disruption can be viewed in three planes (axial, coronal, and sagittal planes) in the same place.

Figure 2

Various locations of the ETs. Notes: (A) ET was close to STJ and did not offer a suitable proximal landing zone for the endograft. (B) ET located in the middle of the ascending aorta was an ideal case for endovascular treatment. (C) ET was located close to LCC, which led to the absence of suitable distal landing zone, a branched endograft or hybrid, or chimney procedure is necessary to maintain perfusion to the branch vessels. Abbreviations: ET, entry tear; LCC, left common carotid artery; STJ, sinotubular junction.

Figure 3

Aortic measurements. Notes: (A) A successful generation of a CLF and the distance from STJ to IA was 81 mm. (B) A plane perpendicular to the CLF where the circle locates in (A) at the ET level. If the cross-sectional shape of the true lumen at ET level was elliptical or even crescentic rather than circular, mathematical modeling was done, (maximum + minimum diameter)/2, to obtain correct diameter. Abbreviations: CLF, centerline of flow; ET, entry tear; FL, false lumen; IA, innominate artery; STJ, sinotubular junction; TL, true lumen.

Figure 4

A scatter plot showing the locations of the ET. Notes: The distance of ET is represented in millimeters relative to the STJ (x axis) and IA (y axis). The dashed lines at 20 mm distal to STJ and proximal to IA represent the minimum distances required for proximal and distal landing zone based on our selection criterion, so the upper right quadrant represents the potential candidacy for endovascular treatment. Patients in the lower right and upper left quadrants have unfavorable anatomy due to insufficient distal and proximal landing zones. Abbreviations: ET, entry tear; IA, innominate artery; STJ, sinotubular junction.

Figure 5

A trend graph showing the true lumen diameter versus the location of the ascending aorta. Notes: The ascending aorta is divided into tenths from STJ to IA (x axis), and y axis represents the true lumen diameters (mm) at each level. A downward trend of the diameters is observed, which indicates that conical endografts might have advantages in the ascending aortic pathology. Abbreviations: IA, innominate artery; STJ, sinotubular junction.