Dynamic Morphology of the Aorta. Pre- and postoperative imaging

Abstract

With endovascular treatment of the aorta a folded covered stentgraft is introduced in the aorta via the femoral arteries. Adequate pre-operative planning is necessary to allow for proper stentgraft sizing. Stentgrafts should be adequately oversized to ensure good apposition to the aortic wall and provide sufficient fixation. An adequate proximal seal and fixation prevents complications such as endoleakage and stentgraft migration. Stentgrafts are most commonly sized on static computed tomographic (CT) images. However, as a result of cardiac contraction and aortic compliance the aorta exhibits pulsatile shape changes throughout the cardiac cycle. With the high speed acquisition of the current CT scanners, the sealing and fixation zones of the aorta are scanned within a fraction of the cardiac cycle. Images might be obtained in systole, diastole or anywhere in between. With ECG-synchronized imaging we visualized the aortic shape changes in the thoracic and abdominal aorta. We used ECG-synchronized CT and Magnetic Resonance Imaging scan protocols, which, respectively, resulted in 8 and 16 images throughout the cardiac cycle. Subsequent image post-processing techniques allowed for quantification of the aortic distention and the asymmetry therein. In some patients with aortic aneurysms, diameter changes were over 10% at relevant endograft sealing zones. In these patients endograft oversizing of 10% might not be sufficient. Aortic distention at the endograft sealing zones might be a predictor for proximal neck problems and compromised endograft durability. After endografting of the thoracic aorta the pulsatile aortic distention was preserved and this may have serious consequences for endograft durability. We observed an asymmetric distention of the aorta. Endograft design should be able to adapt to and withstand this continuous and pulsatile asymmetric distention. The aorta of young healthy volunteers also exhibited an asymmetric pulsatile distention, with pronounced radius changes ranging from 14% to 41%. In general, the orientation of distention was anterior-posterior. There might be a relation between the direction of distention and development and localization of vascular pathology. A valuable non-invasive tool for future research into aortic distention, development and localization of vascular pathology is provided. In addition, we validated the concept of a new and fast method to measure post-operative aortic aneurysm volume on CTA data. Using this method we showed that volumetry is more sensitive for detecting aneurysm sac growth or shrinkage than diameter alone. Volume measurements should have a place in the follow-up after endovascular aneurysm repair.