Cancer as a Hidden Catalyst: Rethinking Postoperative Atrial Fibrillation After Cardiac Surgery

Postoperative atrial fibrillation (POAF) is the most frequent post-cardiac surgical arrhythmia and is associated with haemodynamic instability, longer hospital stays, higher healthcare utilisation, stroke and adverse long-term outcomes. Conventional models of POAF focus on advancing age, pre-existing atrial substrate, increasing operative complexity, inflammatory responses related to cardiopulmonary bypass, disturbances in autonomic balance, and acute metabolic insults during the perioperative period. Although these explanations are important, they may be incomplete. Malignancy and the cancer-associated systemic environment involve biological processes potentially relevant to postoperative atrial vulnerability, such as chronic inflammation, oxidative stress, impaired vascular function, hypercoagulability, altered immune response, frailty, and treatment-related myocardial, pericardial, or conduction-system injury. This review assesses whether malignancy should be regarded as an underrecognised modifier of susceptibility rather than as a coincidental comorbidity. Most available data are extrapolated from cardio-oncology and thoracic oncology studies or general studies related to atrial fibrillation (AF) rather than studies focused on cardiac surgery. While malignancy cannot be dismissed as irrelevant to the generation of POAF, it also does not permit causal inference. Future studies should move beyond binary cancer status and incorporate cancer activity, treatment exposures, biomarker profiles, and atrial substrate measures to determine whether malignancy improves perioperative POAF risk stratification.