Biomarkers in lone atrial fibrillation - an additional 'fine tuning' of risk?

Lone atrial fibrillation (LAF) is generally regarded as a benign disorder that does not significantly increase the risk of thromboembolism and mortality. However, there is growing evidence that "lone" atrial fibrillation (AF) is a "heterogeneous" disorder with varying risk for thromboembolism based on the patient's underlying cardiovascular risk factors. Blood biomarkers, including markers of myocardial strain, inflammation, endothelial injury, platelet activation, and hypercoagulability, have potential to improve our risk stratification and management of LAF. Currently, there is a paucity of data on biomarkers in strictly defined LAF. The majority of studies that aimed to study lone atrial fibrillation excluded patients with structural heart disease, but did not exclude patients with co-existing cardiovascular risk factors such as hypertension or diabetes mellitus. Moreover, many of the studies did not exclude patients based on age, thereby increasing the likelihood of including patients with cardiovascular co-morbidities. There are currently a limited number of studies aimed to investigate the role of biomarkers in true LAF. The results are conflicting as to whether these biomarkers are associated with LAF or stroke risk. Future studies enrolling patients with true LAF using strict definition are needed. Herein, we review our current knowledge of biomarkers in association with atrial fibrillation and LAF and discuss their potential clinical utility.