Funding Acknowledgements Type of funding sources: None. Background ARNI has been shown to be superior to enalapril in long term reducing the mortality and hospitalization of heart failure (HF). However short-term effect on diastolic function remain unclear. We sought to evaluate 6 months" effects of ARNI on left ventricular (LV) diastolic parameters determined by speckle tracking and tissue Doppler imaging. Objectives This study aims to evaluate the torsional dynamics and 2D speckle tracking in heart failure with reduced ejection fraction on patients taking angiotensin receptor neprilysin inhibitors (ARNI) and non. Methods This study was carried out in Menoufia university hospitals included 60 patients of HFrEF during the period from august 2019 to January 2020. (50%) of patients was treated with traditional treatment of heart failure and the remaining was treated with ARNI. Data were collected including history and clinical examination. ECG and speckle tracking and tissue Doppler imaging was done to evaluate the diastolic function. Results Our results showed no significant difference between the two groups at baseline. There was significant improvement of the LV diastolic function. Untwist time and untwist onset showed the highly significant parameters of improvement. Conclusion This study concluded that ARNI showed short term improvement of diastolic function of the left ventricle that can be detected by STE. Comparison between the studied groups re Echocardiographic diastolic parameters after 6 months ARNI Traditional P-value (Sig.) Count 30 30 Diastolic dysfunction grade Grade 1 9 (30%) 1 (3.3%) 0.008 (S) Grade 2 18 (60%) 22 (73.4%) Grade 3 3 (10%) 7 (23.3%) Other doppler diastolic parameters E/A 0.93 ± 0.30 1.16 ± 0.26 0.002 (S) E/e" 9.1 ± 1.9 10.8 ± 1.6 <0.001 (HS) TR velocity (m/s) 2.6 ± 0.3 2.8 ± 0.3 0.003 (S) Speckle diastolic parameters Untwist rate (°/s) -65.4 ± 5.2 -60.4 ± 4.5 <0.001 (HS) Untwist onset (ms) 96.8 ± 16.2 106.1 ± 15.7 0.028 (S) Shows comparison between ARNI vs Traditionally treated patients and how the parameters of conventional and STE was improved in favor of diastolic parameters. Abstract Figure. Baseline vs 6 months inbetween studied g