Reasons why huge saccular aneurysms do not rupture in patient with polycythemia: a case report

Abstract

Abstract Background Morphologically, the risk of aortic aneurysm rupture is mainly evaluated based on the diameter and type (e.g., fusiform or saccular). Recently, based on finite element analysis, a sac depth/neck width > 0.8 and aspect ratio (vertical diameter/horizontal diameter) < 1.0 indicate a high risk of rupture. However, some aneurysms do not rupture despite a high risk according to the morphology. Therefore, the influence of other risk factors of aortic aneurysm rupture should be considered. Case presentation: A saccular aortic aneurysm (84 mm) was incidentally detected during preoperative examination for chronic empyema in a 74-year-old male patient with a history of polycythemia. Aortic arch graft replacement using an open stent was performed. Conclusions Morphologically, this case was associated with a very high risk of rupture; nevertheless, it did not rupture. It has been reported that the wall stress based on finite element reflects the risk of rupture more accurately than the rupture risk based on the diameter of aneurysm. The neck of saccular aneurysm is the highest peak wall stress and is linked to the rupture point. Additionally, it has been reported that the disappearance of endothelial cells is associated with a high risk of rupture. Although a mural thrombus leads to vascular necrosis and aneurysm formation by blocking blood supply from vasa vasorum, in this case, a mural thrombus (likely formed due to polycythemia) covered the neck of aneurysm and embolized within saccular aneurysm preserving intima like coil embolization, and a decrease in peak wall stress could be attributed to reduction in the risk of rupture even for huge saccular aneurysms.