Objective: To examine whether there is an association between prehospital transfer distance and surgical mortality in emergency thoracic aortic surgery. Methods: A retrospective cohort study using a national clinical database in Japan was conducted. Patients who underwent emergency thoracic aortic surgery from January 1, 2014, to December 31, 2016, were included. Patients with type B dissection were excluded. A multilevel logistic regression analysis was performed to examine the association between prehospital transfer distance and surgical mortality. In addition, an instrumental variable analysis was performed to address unmeasured confounding. Results: A total of 12,004 patients underwent emergency thoracic aortic surgeries at 495 hospitals. Surgical mortality was 13.8%. The risk-adjusted mortality odds ratio for standardized distance (mean 12.8 km, standard deviation 15.2 km) was 0.94 (95% confidence interval, 0.87-1.01; P = .09). Instrumental variable analysis did not reveal a significant association between transfer distance and surgical mortality as well. Conclusions: No significant association was found between surgical mortality and prehospital transfer distance in emergency thoracic aortic surgery cases. Suspected cases of acute thoracic aortic syndrome may be transferred safely to distant high-volume hospitals.
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