Bo Wen Li ¹ Juan Li ^1* Xin Meng ^1* Shu Yang ¹ Furong Tian ^1* Xiang Song ^2* Junjie Liu ^1*

• ¹ School of Clinical Medicine, North China University of Science and Technology, Tangshan, China
• ² School of Basic Medical Sciences, North China University of Science and Technology, Tangshan, Hebei Province, China

Objective: This research aims to investigate the association between the ratio of blood urea nitrogen to creatinine (BUN/Cr) and the rate of in-hospital mortality in patients with acute ischemic stroke (AIS) and atrial fibrillation (AF), who are also receiving care in intensive care unit (ICU).Methods: A retrospective study was conducted using the MIMIC-IV database. We collected data on BUN/Cr levels at admission for patients with AIS and concurrent AF. To assess the association between BUN/Cr and in-hospital mortality rate, statistical analysis was conducted employing multivariable logistic regression models and restricted cubic spline models. These models were utilized to investigate the potential relationship and provide insights into the impact of BUN/Cr on the likelihood of in-hospital mortality. Interaction and subgroup analyses were performed to evaluate the consistency of the correlation.Results: There were a total of 856 patients (age ≥18 years) with a median age of 78.0 years, of which 466 (54.4%) were female. Out of 856 patients, 182 (21.26%) died in the hospital. Upon controlling for confounding factors, the multivariable logistic regression analysis elucidated that patients falling within the third trisection (Q3 > 22.41 mg/dl) exhibited a noticeably increased susceptibility to inhospital mortality when contrasted with their counterparts positioned in the second trisection (Q2: 17.2-22.41 mg/dl) (OR=2.02, 95% CI: 1.26-3.26, p=0.004). A nonlinear J-shaped relationship was observed between BUN/Cr at ICU admission and in-hospital mortality rate (P=0.027), with a turning point at 19.63 mg/dl. In the threshold analysis, there was a 4% rise in in-hospital mortality for each 1 mg/dl increase in BUN/Cr (OR: 1.04,95% CI: 1.01-1.06, p = 0.012).In patients with AIS complicated by AF, BUN/Cr at admission shows a J-shaped correlation with in-hospital mortality rate. When BUN/Cr exceeds 19.63 mg/dl, the in-hospital mortality rate increases.