Abstract Body (Do not enter title and authors here): Introduction: Turner syndrome (TS) is caused by the partial or complete absence of one sex chromosome and affects 1 in 2500 liveborn infants. Hypertension, bicuspid aortic valve (BAV), and thoracic aortic aneurysms (TAAs) are more prevalent in TS compared to the general population and predispose to aortic dissections, which may occur in young adults with TS. We hypothesize that adults with TS who have TAAs experience a high rate of adverse cardiovascular outcomes.

Methods: Adults with TS who had Healthy Heart Project (HHP) echocardiograms at national conferences between 2003 and 2023 were contacted for enrollment in descending order of the aortic size index (ASI, cm/m²), defined as the ratio of the maximum ascending aortic diameter to body surface area. After informed consent, clinical characteristics and outcomes (as numbers of participants or median and interquartile range) were abstracted from questionnaires and medical records.

Results: Sixty-four of 704 total HHP participants were contacted and 19 (with 10 of the 20 highest ASI values) were enrolled with complete data. The baseline ASI was 2.19 (0.48), compared to 1.51 (0.36) for all other HHP participants. The median age was 59 (13) years. The most prevalent characteristics were 45,X (10) or 45,X/46,XX (6) karyotypes; BAV (9), coarctation (4), or no congenital lesions (6); and hypertension (12). A mean of 10 serial aortic images were available for each participant over a follow up period of 14 (9.8) years. The median increase in aortic diameter was 0.09 (0.29) mm/yr at the sinuses of Valsalva and 0.26 (0.44) mm/yr at the ascending aorta. Seven participants underwent aortic operations due to enlarging TAAs when the median ascending diameter was 3.83 (0.67) cm (ASI 2.58 (0.11) cm/m²). In 3 cases, operations were urgent due to cardiovascular symptoms or rapid aortic dilation, but there were no acute aortic dissections. The median time between the index image and subsequent repair was 3.5 (7.0) years. Three HHP participants with the 8th, 15th, and 42nd largest ASI values died prior to follow up. One death was caused by complications after surgical aortic valve replacement at age 20.

Conclusions: In a cohort of adults with TS and TAAs, 40% (7/19) developed progressive aortic enlargement requiring aortic repairs and there were 3 deaths. These observations underscore the importance of lifelong surveillance and timely intervention to prevent deaths due to cardiovascular disease in TS.