Figure 4.

Multivariable-adjusted association of end of surgery (A) urine isofurans and (B) urine F₃-isoprostanes with postoperative atrial fibrillation (PoAF), evaluated by restricted cubic splines and logistic regression. Biomarkers underwent log-transformation before analyses as they were right-skewed, and analyses adjusted for age (years), sex (male/female), country (US, Italy, Argentina), body mass index (kg/m²), prevalent hypertension (yes/no), prevalent diabetes (yes/no), prevalent coronary heart disease (yes/no), prevalent chronic renal failure (yes/no), prevalent heart failure (yes/no), smoking (never or former/current), dyslipidemia (yes/no), statin medication use (yes/no), ejection fraction (%), and logistic Euroscore (continuous). The solid red line and shaded areas represent the OR and 95% CIs, respectively, in comparison to the reference level representing the median value of the lowest quartile (12.5th percentile). Dotted vertical lines correspond to the 10th, 25th, 50th, 75th, and 90th percentiles of the log biomarker concentrations. Both biomarkers associated linearly overall with PoAF (P=0.02 for each) but showed little evidence of nonlinearity (P≥0.26 for each).