Objects: We aimed to clarify the differences in the significance of the ratio of diastolic elastance (Ed) to arterial elastance (Ea), [Ed/Ea=(E/e’)/(0.9×systolic blood pressure)], an afterload-integrated diastolic index that reflects left atrial pressure overload, on prognosis between patients with heart failure with preserved ejection fraction (HFpEF) with and without atrial fibrillation (AF). Methods: We studied 552 HFpEF patients hospitalized for acute decompensated heart failure (sinus rhythm/AF:352/200). Blood testing and transthoracic echocardiography were performed before discharge. Primary endpoint was all-cause mortality after discharge. Results: During a median follow-up of 508 days, 88 patients (sinus rhythm/AF: 54/34) had all-cause mortality. In the subgroup with sinus rhythm, but not AF, Ed/Ea was significantly higher in patients with than without all-cause mortality. In a multivariate Cox hazard analysis, Ed/Ea was significantly associated with all-cause mortality independent of N-terminal pro-brain natriuretic peptide level in patients with sinus rhythm, but not with AF. Conclusions: Ed/Ea provided lesser important information for predicting all-cause mortality in HFpEF patients with AF than with sinus rhythm. The prognostic risk factors may differ between elderly HFpEF patients with and without AF.