Abstract 16982: Baseline Diameter Does Not Predict Growth Rate in Ascending Thoracic Aortic Aneurysm

Abstract

Introduction: Patients with ascending thoracic aortic aneurysm (aTAA) are recommended to undergo routine imaging surveillance. While maximal diameter is the primary metric of disease severity, recent AHA/ACC guidelines emphasize the importance of aortic growth in determining surgical candidacy and risk of complications. Increasing diameter is often assumed to confer higher aortic growth rate (GR) due to increased wall tension; however, this relationship is poorly studied. Goal: To investigate the relationship between aTAA diameter and GR using Vascular Deformation Mapping (VDM), a validated technique for 3D growth mapping with sub-millimeter accuracy. Methods: We identified 122 patients with ascending aortic dilation (≥4.0 cm) and serial gated CT angiograms (CTA) with an interval of ≥2 years. Ascending GR was defined as the 90th percentile of wall deformation (radial direction) by VDM, normalized by interval (mm/y). Maximal diameter measurements were taken from the baseline CTA report. Aortic height index (AHI, cm/m) and aortic cross-sectional area/height ratio (CSAH, cm^2/m) were calculated. Ascending aortic length (AL, mm) was measured from the annulus to the origin of the innominate artery. Results: 122 patients (60.7% male, mean age 62.8 ± 10.9 y, 0% connective tissue disease) showed a mean baseline diameter of 44.7 ± 3.7 mm and mean GR of 0.30 ± 0.44 mm/y. No correlation was noted between GR and baseline diameter (r= -0.02, p= 0.86), AHI (r= -0.06, p= 0.54), CSAH (r= -0.04, p= 0.70), or AL (r= 0.08, p= 0.41). Diameter was modestly correlated with GR (r = 0.65, CI 95%: 0.11-0.89, p = 0.02) among the small subgroup with diameter ≥50mm (n=12). GR was not significantly correlated to age (r= -0.13, p= 0.17) and did not differ by sex (p= 0.91) or hypertension (p= 0.51). No demographic or anatomic variables were predictive of GR on multivariable analysis. Conclusions: Maximal aortic diameter is not predictive of aortic GR, especially at sizes under surgical thresholds (<50 mm).