Postoperative atrial fibrillation after elective thoracic surgery: incidence, timing, and associations with respiratory, inflammatory, and cardiac stress markers

Background Postoperative atrial fibrillation (POAF) is a clinically relevant rhythm disturbance after thoracic surgery and may reflect the combined effects of surgical trauma, impaired pulmonary physiology, inflammation, and cardiopulmonary stress. This study aimed to evaluate the incidence and timing of POAF after elective thoracic surgery and to identify clinical, respiratory, intraoperative, inflammatory, and cardiac stress markers associated with its development. Methods This prospective observational cohort study included 172 adult patients undergoing elective thoracotomy or video-assisted thoracoscopic surgery between June 2022 and June 2023. Patients with a history of atrial fibrillation, newly diagnosed preoperative atrial fibrillation, emergency surgery, intraoperative cardiac arrest, or insufficient postoperative rhythm monitoring were excluded. Rhythm status was assessed during the first five postoperative days using daily 12-lead electrocardiography and additional rhythm confirmation when clinically indicated. Patients were categorized as having no arrhythmia, POAF, or other postoperative rhythm disturbances. Clinical characteristics, surgical and intraoperative variables, respiratory function, arterial blood gas parameters, and perioperative inflammatory and cardiac stress biomarkers were analyzed. Results Postoperative rhythm disturbances occurred in 32 patients (18.6%), and new-onset POAF developed in 18 patients (10.5%). Most POAF episodes occurred early, with 16 of 18 cases (88.9%) developing within the first 72 postoperative hours, and the highest number of cases occurring between 48 and 72 h. Open thoracotomy and pneumonectomy were more frequent among patients with POAF. Patients who developed POAF had greater cumulative smoking exposure, more frequent erythrocyte transfusion and norepinephrine use, lower preoperative FEV₁, lower preoperative oxygenation, lower post-extubation SaO₂, and higher end-of-operation and postoperative 24-hour lactate levels. Postoperative 24-hour NLR, CRP, and NT-proBNP levels were also higher in patients with POAF, whereas troponin T and magnesium levels did not differ significantly among rhythm groups. Exploratory POAF-focused analyses showed similar patterns, but these findings should be interpreted cautiously because of the limited number of POAF events. Conclusions POAF occurred in 10.5% of patients after elective thoracic surgery, with most episodes developing within the first 72 postoperative hours. The findings suggest that POAF after thoracic surgery represents a complex perioperative phenotype associated with reduced pulmonary reserve, impaired oxygenation, greater surgical stress, hemodynamic instability, systemic inflammation, and myocardial wall stress. Easily obtainable markers such as NLR, CRP, lactate, and NT-proBNP, when interpreted together with clinical and respiratory variables, may help characterize patients who warrant closer early postoperative rhythm surveillance.