Abstract Body (Do not enter title and authors here): Background: Ascending aortopathy (AA) is mostly asymptomatic and often incidentally diagnosed using cardiac imaging (either transthoracic echocardiography [TTE] or computed tomographic angiography [CTA]). However, to optimally time surgical replacement, precise aortic measurements are crucial.

Objective: We sought to evaluate the extent of reclassification of aortic size thresholds provided by using CTA vs. TTE in AA patients.

Methods: We included 7459 patients with an unrepaired AA (≥4 cm), who underwent TTE and subsequently underwent contrast-enhanced electrocardiographically gated CTA (within 1 year of each other) between 1/2010 and 12/2023 at our large tertiary referral center. Patients presenting with an acute aortic dissection/rupture as an initial presentation were excluded (n=1188). Aortic root (AR) and mid-ascending aortic (MAA) diameters were measured on TTE and CTA. In addition, on CTA, cross sectional area to height ratios (CSAH) were measured at the AR and MAA on CTA and a threshold of ≥10 cm2/m is considered abnormal.

Results: The baseline characteristics of the study population are shown in Figure 1. Figure 2 demonstrates the distribution of patients, separated on basis of 3 aortic diameter thresholds (<4.5 cm, 4.5-4.9 cm and ≥5 cm) at AR and MAA. Despite a significant correlation (r=0.80, p<0.001), TTE under-recognized an AR aneurysm (defined as ≥ 5 cm) in 646/1110 (58%) and over-estimated an aneurysm in 95/559 (17%) patients. Similarly, despite a significant correlation (r=0.79, p<0.001), TTE under-recognized an MAA aneurysm in 564/1518 (37%) and over-estimated an aneurysm in 379/1333 (28%) patients. CTA identified an additional 515 (32%) patients with an abnormal CSAH in the AR (of which 79 [15%] were women), despite the diameter in the non-aneurysmal range (<5 cm). Similarly, there were 949 (39%) patients with abnormal CSAH in the MAA (of which 383 [40%] were women), despite the diameter in the non-aneurysmal range.

Conclusions: In patients with suspected AA identified on TTE, CTA appropriately reclassifies a significant proportion of patients as having an aneurysm or not. Tomographic imaging should be considered in all patients with documented AA on TTE. Additionally, CTA identified a high proportion of patients with abnormal CSAH, despite the root or ascending aortic diameters not in the aneurysmal range. This might have implications in terms of timing of appropriate surgical referral for aortic replacement, especially in women.