Santema BT, et al. - In this retrospective analysis of the BIOlogy Study to TAilored Treatment in Chronic Heart Failure (BIOSTAT-CHF), an observational cohort, researchers compared biomarker profiles of patients with heart failure (HF) with reduced vs preserved ejection fraction (HFrEF vs HFpEF) in order to gain insights into underlying pathophysiological mechanisms of atrial fibrillation (AF) in these different HF phenotypes. They detected a homogeneously elevated cardiovascular risk marker profile in relation to the presence of AF in patients with HFrEF, vs patients with HFpEF who had a more scattered risk marker profile in relation to the presence of AF. Based on these findings, the underlying pathophysiological mechanisms of AF in these HF phenotypes were suggested to be different.