Abstract WP78: Identifying Aneurysm Growth Based on Imaging: A Size Increase of 0.8-0.9 mm is the Optimal Threshold to Classify Growth

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Introduction: Documenting aneurysm growth is the key to monitoring the risk of aneurysm rupture. While aneurysm size changes can be found through imaging, the threshold which defines significant growth is important for clinical aneurysm management and consistency between studies. The purpose of this study is to investigate which threshold constitutes significant growth and best separates aneurysms into growth/no growth categories. Hypothesis: An optimal growth threshold that delineates aneurysm growth can be identified by a detailed study of longitudinal aneurysm data and risk factors. Method: A retrospective study was performed, examining 290 aneurysms longitudinally followed with CTA. Our study included 29 males and 177 females with a mean age of 61±13.22 years. We used the Chi-Square Test and Two-Way ANOVA to evaluate risk factors which included the initial aneurysm size, patient’s age and sex, multiplicity/number of aneurysms, lobulation, calcification, and aneurysm location. For each risk factor, growth thresholds ranging from 0.5-1.0 mm with a 0.1 mm interval were tested to classify aneurysm size change as “Growth” or “No Growth.” Independent T-Tests were also performed using these thresholds to compare the follow-up period between “Growth” and “No Growth” aneurysms. Results: The Chi-Square Test showed that the patient’s age and initial aneurysm size were statistically significant (p<0.05) for most growth thresholds. The Two-Way ANOVA revealed a significant interaction (p<0.05) between the patient’s age and initial aneurysm size. The Independent T-Tests showed a significantly longer (p<0.05) follow-up period for aneurysms with growth. Additionally, we ranked the growth thresholds for each test (based on which thresholds produced the lowest p-value) and summed up the ranks for each threshold. The thresholds of 0.8 mm and 0.9 mm produced the lowest p-values, making them the optimal thresholds. Conclusion: Patients under 50 years old and patients with aneurysms larger than 9.5 mm have an increased risk of aneurysm growth of 0.8 mm or more, and these aneurysms may need frequent follow-up and careful monitoring. Additionally, aneurysms that grow at least 0.8mm are growing significantly and may require intense clinical management.