Progressive aortic enlargement in medically managed acute type B aortic dissections with visceral aortic involvement.

Objective: Aortic remodeling of the thoracic aorta has been studied in patients treated with medical or endovascular therapy for the treatment of acute aortic dissections; however, particular attention has not yet focused on identifying specific growth patterns and rates across all aortic zones. Additionally, previous studies have not delineated between dissections with and without visceral aortic involvement, and we hypothesize that these two cohorts may exhibit distinct differences. The aim of this study is to investigate aortic behavior over time in medically managed acute Society for Vascular Surgery/Society of Thoracic Surgeons (SVS/STS) type B dissections with visceral aortic involvement and identify potential associations of subsequent aortic behavior with clinical outcomes.

Methods: A single-center retrospective review was performed of all patients between 2010 and 2020 with acute SVS/STS type B aortic dissections with visceral aortic involvement that were not surgically managed. Short-axis centerline measurements of the true/false lumen and total aortic diameter (TAD) were taken at standardized locations relative to aortic anatomy within each aortic zone, including nondissected zones. Measurements were taken at the time of diagnosis and at six subsequent yearly intervals. Diameter changes over time were evaluated using repeated measures mixed models linear growth analysis. Aortic enlargement was classified by growth in TAD ≥5 mm in either the thoracic (thoracic segment enlargement [TSE], zone 0-4) or visceral segments (visceral segment enlargement [VSE], zone 5-9).

Results: A total of 78 patients were identified with a median length of follow-up of 3.3 years (interquartile range [IQR], 1.3-6.6 years). Follow-up past 5 years was seen in 31% of the cohort. For the entire cohort, mean thoracic growth in TAD was 2.0 ± 2.0 mm/year, and visceral growth in TAD was 2.5 ± 2.4 mm/year. TSE was observed in 65% of patients, with a median time until onset of 0.8 years (IQR, 0.4-2.3 years). VSE was observed in 57% of the cohort, with a median time until onset of 1.6 years (IQR, 0.9-3.3 years). Repeat measures mixed models linear growth analysis identified significant predictable linear growth in all aortic zones except for the nondissected zones 0-2. Odds for TSE are significantly increased in patients with known genetically triggered aortic conditions (odds ratio [OR], 2; 95% confidence interval [CI], 1.8-4.5; P = .044) and in cases where the dissection entry tear was in either zone 1 or 2 (OR, 4.8; 95% CI, 1.2-8.4; P = .044). In adjusted regression analysis, odds for intervention in the thoracic aorta were significantly increased in patients with rapid TSE in zone 3 (OR, 3.6; 95% CI, 1.1-8.4; P = .045). Similarly, odds for intervention targeting the visceral aortic segment were significantly increased in patients with zone 9 VSE (OR, 9.3; 95% CI, 1.1-13.3; P = .014). Odds for 5-year all-cause mortality were significantly increased in cases with large thoracic aneurysms (OR, 6.1; 95% CI, 1.1-14.9; P = .042).

Conclusions: Aortic enlargement was present in the majority of patients with medically managed acute SVS/STS Type B aortic dissections with visceral aortic involvement, with analysis demonstrating predictable linear growth in all dissected zones. Patients with aortic enlargement demonstrated higher gross changes in diameter in addition to higher yearly rates of change compared with all comers. Odds for enlargement were impacted by both patient demographic and anatomic dissection characteristics. Growth in zone 3 and zone 9 significantly increased odds for aortic intervention. Odds for 5-year mortality were significantly increased in the presence of large thoracic aneurysms. Results highlight risk of progressive degeneration beyond acute phase in SVS/STS Type B aortic dissections with visceral aortic involvement, with life-long surveillance remaining crucial in management of dissections.