Abstract 4140345: 3D Statistical Shape Analysis Predicts Type A Aortic Dissection Better Than Aortic Diameters

Introduction/Background: The vast majority of type A aortic dissection (TAAD) patients do not meet diameter thresholds for ascending aortic repair before their dissection. Increased ascending aortic length has been suggested to improve risk predictions, but this metric simplifies the aortic shape to a single dimension and doesn’t capture 3D features like tortuosity/torsion. Research Questions/Hypothesis: Are there distinct shape features of the ascending aorta that differentiate patients with TAAD better than aortic diameter? Methods/Approach: We retrospectively identified patients with good quality, pre-dissection CT imaging of the chest at our center prior to surgical repair of acute TAAD, excluding those with pre-existing dissection or prior aortic intervention. This pre-TAAD group was compared to a reference cohort of ‘normal’ patients (no aortic disease), patients with borderline ascending aortic dilation (35-44 mm) and ascending aneurysm (≥45 mm; aTAA). A shape score, based on statical shape modeling (SSM) and cosine similarity was computed (tubular ascending and arch) to quantify the similarity between an individual aortic shape compared to the mean ‘normal’ shape (defined as -1) and mean pre-TAAD shape (defined as +1). Results/Data (descriptive and inferential statistics): We identified 30 spontaneous TAAD patients with CTs at a median of 1.5 (IQR: 0.7-3.8) years pre-dissection. We compared against pre-existing cohorts with normal aortas (n=165), borderline dilation (n=119) and aTAA aneurysm (n=42). Age, sex and hypertension did not significantly differ between TAAD and aTAA groups. Max diameter (47.7 ± 2.0 vs. 40.6 ± 6.0 mm, p<0.01), centerline length (130 ± 11.5 vs. 120 ± 16.7 mm, p<0.01) and tortuosity (1.33 ± 0.08 vs. 1.27 ± 0.07, p<0.01) were higher in aTAA versus TAAD. Median SSM scores were higher in the (TAAD group 1.25, IQR: 0.76-1.46) compared to the aTAA group (-1.25, IQR: -1.60, -0.95; p<0.01) and the borderline dilation group (-1.03, IQR: -1.25, -0.84; p<0.01), Figure 1 . SSM scores for normal, borderline dilated and aTAA did not significantly differ. Conclusion: A novel SSM-based scoring method of assessing ascending aorta and arch geometry reveals clear shape differences among patients prior to TAAD.