Study of the Sudden Heart Failure Participant Population in the US

Inclusion Criteria: * Age 18 years or older on the index date * At least 6 months of activity in the database * An inpatient visit with at least one of the following ICD-9 or ICD-10 diagnosis codes (ICD-9 diagnosis codes: 428.xx, 785.51 or ICD-10 diagnosis codes: I50.xx, R57.0) in the primary or secondary position OR mention of "heart failure" on the admission record Exclusion Criteria: * An average LVEF ≥ 40 during the hospitalization * Any code for myocardial infarction (ICD-9 diagnosis code: 410.xx, ICD-10 diagnosis code: I21.xx) or related terms such as "myocardial infarction", "mi", "infarct" or "heart attack" occurring during the index hospitalization Other protocol defined inclusion/exclusion criteria could apply