Association of Circulating Calcitonin With Risk and Onset of Postoperative Atrial Fibrillation After Cardiac Surgery

Background: Postoperative atrial fibrillation (POAF) affects up to 50% of cardiac surgery patients and is linked to higher morbidity, longer hospital stays and increased thromboembolic risk. Early identification of at-risk patients remains challenging. Calcitonin (CT), a hormone with anti-fibrotic effects, may serve as a novel biomarker. Methods: In 491 patients undergoing elective cardiac surgery, baseline serum CT was measured preoperatively using CT-specific enzyme-linked immunosorbent assay (ELISA). Patients with pre-existing AF were excluded. Associations between CT levels and POAF incidence and onset were evaluated using logistic regression, Cox proportional hazards models, and Kaplan-Meier analysis. Results: Among 248 patients with detectable CT levels, 88 patients developed POAF. Higher baseline CT was independently associated with lower risk of POAF (OR 0.68 per 5 pg/ml increase; 95% CI 0.51-0.89; P = 0.009) and delayed arrhythmia onset (adjusted HR 0.941; 95% CI 0.898-0.980, P = 0.0026) after adjusting for covariates. Kaplan-Meier analysis demonstrated a graded relationship between increasing CT levels and reduced cumulative incidence of POAF. In this cohort, baseline CT showed greater discriminative ability than CRP and BNP, although overall model performance remained moderate. Conclusion. Higher preoperative circulating CT levels are associated with reduced risk and delayed onset of POAF following cardiac surgery. These findings suggest that calcitonin may have the potential as a biomarker for perioperative risk stratification in POAF. Given the observational design and single-centre setting, further validation in independent cohorts and studies integrating mechanistic insights are warranted.