Introduction: Reports have suggested that high blood flow pulsatility in aneurysms may predict a higher risk of rupture, however, it is unclear whether similar flow dynamics also predict aneurysm growth. The objective of this study is to investigate differences in shape and blood flow characteristics between unruptured growing and stable aneurysms of comparable sizes.
Hypothesis: Growing and stable aneurysms of comparable sizes exhibit different flow characteristics across different aneurysm regions.
Method: We studied 4 growing aneurysms located at the posterior communicating artery (size ranged from 1.8mm to 11.4mm). Patient-specific aneurysm flow analysis and 3D aneurysm shape analysis were performed to investigate the flow changes during follow-up imaging. Specifically, we compared the shape parameters including aneurysm size, volume, and surface changes. We also compared the aneurysm flow properties including flow velocity, wall shear stress, pulsatility, and flow oscillatory characteristics. The growing aneurysms were analyzed against stable-matching aneurysms which were selected based on similar dome and neck size to find the predictive factors for aneurysm growth. These stable-matching aneurysms exhibiting no size changes for 2 years during follow-up were analyzed as a baseline.
Results: We found that blood flow pulsatility through the parent artery was similar across all growing and stable aneurysms, averaging 0.58±0.003. Regardless of aneurysm size, blood flow pulsatility through the aneurysm neck was at the level of 0.66 (0.66±0.06) for growing aneurysms. We also found a clear trend of that blood flow pulsatility increased from the neck to dome in growing aneurysms. Blood flow pulsatility, however, decreased from the aneurysm neck to dome in the stable aneurysms (P<0.05). The rate of increase of blood flow pulsatility through the dome also appears to have an exponential correspondence with the aneurysm volume increase, with a R^2 value of 0.94.
Conclusion: We found that increasing blood flow pulsatility from the aneurysm neck to dome may be indicative of aneurysm growth, which may be useful in identifying aneurysms that will potentially grow into high-risk aneurysms.