Warming up the frozen elephant trunk for aortic arch pathology.

Background: The frozen elephant trunk (FET) technique is a well-established procedure for chronic and acute aortic arch (AA) pathologies. Over time, practice has shifted from deep to moderate hypothermic circulatory arrest (HCA), especially for elective cases. This strategy might, however, impact neurological and renal outcomes. The aim of this single-center study is to assess the safety of very mild HCA (MiHCA) in patients who underwent FET with a core temperature ≥30 ℃. Methods: Data on all consecutive patients who electively or urgently underwent FET requiring HCA at Cardiac Surgery Unit of the University of Pisa were collected. In all cases, antegrade selective cerebral perfusion was performed, and hypothermia was maintained only during circulatory arrest (CA). We assessed postoperative acute kidney injury (AKI), neurological events, and bleeding as primary endpoints. Multivariable analysis was performed to evaluate the predictors of the three outcomes. Results: We included 92 patients, 86% of which presented with an acute aortic syndrome. Of this cohort, 17% had neurological deficits at baseline and 9% were intubated at arrival; the German Registry of Acute Aortic Dissection Type A (GERAADA) score was 24%±14%. The mean bladder temperature was 30±1.6 ℃, and the mean cardiopulmonary bypass (CPB) and CA times were 219±78 and 15 (I-III quartile, 13-19) min, respectively. Median cerebral perfusion time was 59 (I-III quartile, 31-113) min, bilateral antegrade cerebral perfusion (ACP) was performed in 96% of cases, and unilateral in 4%. Packing for bleeding was necessary in 4% of cases, and 21% of patients required surgical revision for bleeding within the first 24 hours from surgery. We had one (1%) fatal, eight (9%) disabling, and five (5%) non-disabling strokes, while 6% of patients developed renal impairment requiring temporary venovenous hemofiltration. Thirty-day mortality was 14%. Bladder temperature was not associated with outcomes, while retrograde perfusion and GERAADA score were predictors of neurological events. GERAADA score also tended to predict postoperative bleeding, while the involvement of the descending aorta tended to predict renal impairment. Conclusions: CA with core temperatures above 30 ℃, paired with selective bilateral cerebral perfusion, resulted in the best outcomes in patients undergoing FET in case of acute aortic syndromes.