Abstract Body (Do not enter title and authors here): Background
There is limited data on how growth unfolds during surveillance of ascending aortic (AsAo) dilation. Most prior research has treated AsAo growth as a linear process, calculating the rate of diameter change between the index and most recent imaging studies to minimize the impact of substantial measurement variability. However, this approach can miss episodic (“staccato”) periods of disease progression—phenomena previously described in abdominal aortic aneurysms—that may affect risk prediction and intervention timing.

Research question
Does growth of the AsAo occur in an episodic or continuous fashion, and what patient characteristics are associated with each growth pattern?

Methods
We performed a single-center, retrospective study of 1,238 patients with ≥4 chest CT/MR angiograms including double-oblique, clinically reported mid-AsAo diameters. Baseline imaging and clinical data came from the first available scan. Given variability in clinical diameter measurements, growth considered present if a ≥2.0 mm increase occurred over a >6-month interval. In a subgroup, we compared diameter growth against Vascular Deformation Mapping (VDM) – a validated, high-precision (<1 mm error) 3D growth mapping technique. Growth was considered present by VDM at a growth rate (GR) of ≥0.3 mm/year. Clinical factors were analyzed using univariate and multivariable logistic regression.

Results
Among 1,238 patients (6,907 scans; 8,541 person-years), mean age was 60 ± 13 years; 69% were male; 88% had hypertension; and 3.4% had Marfan syndrome. Episodic growth occurred in ≥1 interval in 51% of patients (Figure 1). Clinical diameters and VDM showed only “fair” agreement in growth assessments (κ = 0.26; 76% agreement); a >10% false positive and 67% false negative rate for clinical diameter measurements. Patients with episodic growth were younger (56.8 ± 13 vs. 62.5 ± 12, p < 0.001) and had smaller baseline aortas (Z-score 1.45 ± 2 vs. 1.96 ± 2, p < 0.001), both remaining significant after adjustment for potential confounders.

Conclusion
Approximately half of patients with AsAo dilation exhibit evidence of discontinuous growth during surveillance, suggesting alternating periods of biological equilibrium and disequilibrium in the aortic wall. While the mechanisms underlying these episodes and their associated risks require further investigation, younger age at diagnosis and smaller baseline sizes raise the possibility that unrecognized genetic abnormalities may contribute.