Background Diastolic function (DF) guidelines have been simplified but lack extensive outcome data. Using a rural university heart failure (HF) database, we assessed whether DF grading could predict HF, HF readmission, and all-cause mortality (ACM). Methods In this single-center retrospective study that included 613 patients in sinus rhythm hospitalized for HF (HF with preserved-254 patients, with mid-range-216 patients, and reduced ejection fraction-143 patients), we recorded demographics, Doppler-echo, Framingham HF score, laboratories, HF readmission, and ACM with follow-up to 2167 days. Results Diastolic dysfunction (Ddys) parameters (left atrial volume index [LAVI] > 34 ml/m(2), tricuspid regurgitation [TR] velocity > 2.8 m/sec, and E/e' > 14) had moderate sensitivity (46.2%-65.0%) for predicting HF among all phenotypes combined with DF grading having moderate predictability and additive to a clinical composite for HF prediction (AUC = .677, P < 0.0001; difference = .043, P < 0.001) for combined phenotypes. Ddys parameters and Ddys severity (2016 ASE criteria: grade II and III) were significantly associated with HF readmission for decompensated HF within 60-2167 days of follow-up (LAVI > 34 ml/m(2): HR 1.56 [1.26-2.19]; E/e' > 14: HR 1.44 [1.21-1.99]; TR > 2.8 m/sec: H1.43 [1.19-1.88]; LV Dys grade II: HR 2.12 [1.42-2.96]; LV Ddys grade III: HR 2.39 [1.57-4.82]). Conclusion The findings of this study highlight the clinical and prognostic relevance of determining the severity of LV Ddys in patients with HF with regard to HF verification and HF readmission.