This study was designed to investigate predictors of atrial fibrillation (AF) in patients with heart failure with preserved ejection fraction (HFpEF), with a particular focus on the potential relationship between venous congestion and intracranial pressure dynamics. Among HFpEF patients, those with AF exhibited significantly higher right atrial pressure (RAP), larger right atrial area, higher CHA₂DS₂-VA scores, and increased optic nerve sheath diameter (ONSD), a noninvasive surrogate marker of intracranial pressure. In multivariable logistic regression analysis, increased ONSD, elevated RAP, larger right atrial area, and higher CHA₂DS₂-VA score remained independently associated with AF, suggesting that both systemic venous congestion and intracranial pressure-related mechanisms may contribute to AF susceptibility in this population. These findings support the hypothesis of a cardio-cerebral interaction in HFpEF, in which elevated right-sided filling pressures may impair cerebrospinal fluid drainage, increase intracranial pressure, and potentially promote AF through autonomic and hemodynamic pathways.