Inclusion Criteria:  Sacubitril/valsartan incident cohort Included patients  Prescribed sacubitril/valsartan within the identification period (01-July-2015 to 31-Mar-2019), that had non-missing gender and year of birth data. With at least one ICD-9-CM or ICD-10-CM code for diagnosis of HF within one-year prior to date of first prescription of sacubitril/valsartan (index date), and are treated as part of the integrated delivery network. With first month active 365 days prior to index and last date active was greater than or equal to (≥) index, and the month of provider source data was greater than the final date of patient follow-up. That were ≥18 years old at index date. With a valid LVEF value ≤40%, prior to index (index date included).  Angiotensin-converting enzyme inhibitors (ACEi) and Angiotensin II receptor antagonist (ARB) incident cohort  Included patient:  Prescribed ACEi or ARBs within the identification period (01-Jul-2015 to 31-Mar-2019), that had non-missing gender and year of birth data. With at least one ICD-9-CM or ICD-10-CM code for diagnosis of HF within one-year prior to date of first prescription of ACEi or ARB (index date), and were treated as part of the integrated delivery network. With first month active 365 days prior to index and last date active was ≥ index, and the month of provider source data is greater than the final date of patient follow-up. That were ≥ 18 years old at index date. With a valid LVEF value ≤ 40%, prior to index (index date included).  Exclusion Criteria:  Sacubitril/valsartan incident cohort  Excluded patients for the primary objective and secondary objective 2 to 6:  Patients who were prescribed sacubitril/valsartan within one-year prior to index date. Patients who were prescribed ACEi or ARBs, within one-year prior to index date (index date included).  Exclude patients for secondary objective 1:  Patients who were prescribed sacubitril/valsartan prior to index date. Patients who were prescribed ACEi or ARBs prior to index date (index date included).  Angiotensin-converting enzyme inhibitors (ACEi) and Angiotensin II receptor antagonist (ARB) incident cohort  Exclude patients for the primary objective and secondary objective 2 to 6:  Patients who were prescribed ACEi or ARBs within one-year prior to index date. Patients who were prescribed sacubitril/valsartan within one-year prior to index date (index date included). Which had a valid sacubitril/valsartan prescription that enables inclusion in the sacubitril/valsartan cohort. Exclude patients for secondary objective 1: Patients who were prescribed ACEi or ARBs prior to index date. Patients who were prescribed sacubitril/valsartan prior to index date (index date included). Which had a valid sacubitril/valsartan prescription that enables inclusion in the sacubitril/valsartan cohort