Abstract TP363: Longitudinal Study of Hemodynamics and Growth in Matched ICA Aneurysms

Introduction: Larger intracranial aneurysms have a higher risk of rupture. Consistent with this, multiple studies have found that aneurysm growth during follow-up is a strong risk factor for rupture. In this study, we hypothesize that growing aneurysms may have different hemodynamic properties than their counterpart of stable aneurysms. To minimize errors in growth definition due to image resolution, we designed a study and performed a comprehensive review of over 20 years of single-image modality aneurysm data. We analyzed and investigated the hemodynamic differences between pairs of growing and stable aneurysms closely matched according to size and location. Methods: 257 3D CTA image studies were reviewed to study matched ICA aneurysms. Seventeen growing, saccular ICA aneurysms with imaging follow-up and without intervening treatment were identified from electronic medical records, and matching stable ICA aneurysms were found for each. Specifically, the initial diameter of aneurysm was matched within 10% and locations were matched in areas of ophthalmic arteries, the superior hypophyseal arteries, or the posterior communicating arteries. For each aneurysm, one initial and two follow-up 3D images were collected. The mean aneurysm follow-up duration was 4.10 ± 1.98 years. Blood flow within the ICA and aneurysm was modeled with a pulsatile computational fluid dynamics simulation using the 3D Navier-Stokes equations. Fisher’s exact test was used for categorical data, and the Wilcoxon signed-rank test was used to compare hemodynamics between matched samples. Results: Among aneurysm characteristics and patient history, the only significant factors distinguishing the growing and stable groups were bifurcation aneurysms (p = 0.04) and a history of smoking (p = 0.02). Paired difference testing indicated some hemodynamic differences between the two groups were consistent over follow-up. Specifically, flow pulsatility index (PI) varied in the aneurysm body (p = 0.009) and within the ICA immediately after the aneurysm (p = 0.008). Conclusion: Closely pairing growing and stable aneurysms eliminates confounding variables related to size and location. This study indicates that even under such conditions, hemodynamic differences exist. Local hemodynamics may play an important role in continued aneurysm growth.