BACKGROUND: Morphologically, the risk of aortic aneurysm rupture is mainly evaluated based on its type (e.g., fusiform or saccular) and diameter. Based on the finite element analysis, peak wall stress has been identified as a more sensitive and specific predictor of rupture in recent years. Moreover, in finite analysis, the neck of aneurysm is the highest peak wall stress and is associated with the rupture point.
METHODS: 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. In this case, a mural thrombus (likely formed due to polycythemia) covered the neck of aneurysm that is experiencing the highest peak wall stress and is associated with the rupture point. The mural thrombus decreased peak wall stress and could reduce the risk of rupture even for huge saccular aneurysms. Furthermore, the mural thrombus was fully occupied in aneurysms, such as during coil embolization. Thus, polycythemia could decrease the risk of rupture of huge saccular aneurysms.

BACKGROUND: Few previous hemodynamic studies demonstrated the detailed features of rupture point of intracranial aneurysms. The hemodynamic simulation for the case that ruptured during angiography was even rare. In the present study, we studied the hemodynamic characteristics of a posterior communicating artery segment aneurysm that ruptured during angiography and detailed the hemodynamic features at the rupture point.
METHODS: One 64-years-patient was 60-69 years old and suffered a subarachnoid hemorrhage within 24 h. Standard digital subtraction angiography and three-dimensional (3D) rotational angiography were performed and an 8 mm left posterior communicating artery segment aneurysm was found. The patient had a seizure immediately following 3D angiography for about 40 s and the immediate follow-up angiography showed contrast extravasation from the tip of identified aneurysms. The consequent vital sign of the patient became unstable. Urgent embolization under general anesthesia was planned, but the relatives refused interventional operation considering the high risk of procedure and poor condition of the patient. The computational fluid dynamic (CFD) method was used to evaluate the hemodynamic characteristics at rupture point, and the results showed that the rupture point was associated with markedly low wall shear stress and high oscillatory shear index without flow impingement.
CONCLUSIONS: We present a rare case of which the rupture site was identified during angiography. The hemodynamic simulations revealed that the rupture point was associated with markedly low WSS and high OSI without flow impingement. The result may be unique to this particular aneurysm; however, our findings provide insight into the hemodynamics of rupture point.