Patient Selection for Surgery vs. Surveillance in Moderately Dilated Ascending Aorta: Insights from Titan:SvS, an International Prospective Trial.

Background: Guidelines for treating ascending thoracic aortic aneurysms (ATAA) are largely based on single-center studies. To understand factors influencing patient selection for surgery versus surveillance, patient and aneurysm characteristics were compared for subjects in the randomized and registry arms of a large prospective, multi-center, multi-national trial.

Methods: TITAN: SvS (Treatment in Thoracic Aortic aNeurysm: Surgery versus Surveillance) is the largest prospective multi-center study of patients with ATAA between 5.0-5.4 cm, randomizing patients 1:1 to initial surgery versus surveillance. Non-randomized patients are enrolled into a Registry where results of operative or surveillance strategy can be followed prospectively. Between 2018 and 2023, 615 patients were enrolled at 22 sites in USA and Canada. Demographic and aneurysm characteristics were compared between randomized and registry arms.

Results: Compared to randomized and operative registry groups, patients in the surveillance registry were older with more co-morbidities. No significant differences were observed in maximal ascending aortic diameter [(5.1 (5.0, 5.2) vs 5.1 (4.9, 5.2) cm, p=0.2] or other aneurysm characteristics. Despite similar numbers of enrolling centers in the USA (n=11) and Canada (n=12), Canadian patients were more likely to be randomized (58% vs. 7%, p<0.01), and less likely to be enrolled in the operative (9% vs. 42%, p <0.01) or surveillance registry (34% vs. 51%).

Conclusions: Enrollment data TITAN:SvS suggests that patient and geographic characteristics, rather than aortic size, influence decision-making regarding the initial treatment strategy for ATAAs. These findings highlight the need for caution when generalizing outcomes from operative registries, as sicker patients may be excluded.