Abstract Body (Do not enter title and authors here): Background: Most connective tissue disorders (CTD) that cause aortic dilation (AoD) are hereditary. Children suspected of CTD may be referred to a pediatric cardiology or genetics clinic (PC) where the focus of care is on the child. While recommendations for screening of adult family members may be made, it is not typically performed on-site leading to potential gaps in care. We sought to evaluate the impact of a family-focused cardiovascular genetics (CVG) clinic on outcomes and to compare the impact of such a clinic to PC in preventing premature adverse aortic events (AE) in patients and family members.

Methods: A retrospective records review of all pediatric (age < 21 years) encounters for CTD performed during the current era of genetic testing was conducted. Patients were included if AoD was identified. Location of initial clinic visit (PC vs. CVG) was noted. Children referred for a family history of known AoD were excluded. Recommendation for-, completion of- & results of- family screening were noted. Preventable adverse events, defined as AoD-related death/dissection in an undiagnosed proband or family member occurring after initial clinic encounter were recorded. Screening practices & outcomes were compared between clinic types.

Results: Of 154 children who met inclusion criteria with a mean age of 11.1 (+/- 9.3) years, initial evaluation was performed in PC in 94 (61%) & CVG in 60 (39%) patients. Screening was recommended in 37 (39%) vs. 60 (100%) families seen in PC vs. CVG clinic (p<0.00001) and was completed in 23/37 (70%) referred by PC (average of 2.1 (+/- 1.2) family members screened), vs 53/60 (88%) in CVG (average of 3.8 (+/- 5.9) family members screened) (p=.002). Of the 47 screened in PC, 30 (64%) were found to have AoD or the same pathogenic mutation as the proband, compared to 99 (43%) of 230 family members in CVG clinic. Preventable AE occurred in 4 (4%) probands and 30 (31%) families seen in PC compared to 0 probands and 6 (10%) families in CVG (p=.38 for probands, p=.002 for families). Of the 154 families, pathogenic variants in FBN1 [77], TGFBR1 [5], TGFBR2 [9], Col3A1 [4], SMAD3 [6], and other genes [25] were identified as the source of AoD. Gene negative hereditary thoracic aortic aneurysm disease was suspected in 22 (14.3%).

Conclusion: When a child is diagnosed with a hereditary aortopathy, whole family screening is essential to preventing AE. Clinics offering family-based care facilitate timely diagnosis in other family members.