Qualifying clinical encounters included all hospitalizations, emergency department visits including observation stays, and outpatient encounters with a diagnosis code for heart failure (HF). Episodes of worsening HF were defined as including ≥1 qualifying clinical encounter, ≥1 symptom, ≥2 objecting findings including ≥1 sign, and ≥1 change in HF-related therapy. In total, there were 1,223,616 unique clinical encounters with an associated diagnosis code for HF. After applying natural language processing-based algorithms, the proportion of clinical encounters meeting the diagnostic criteria for worsening HF ranged from a low of 4.7% for outpatient encounters to a high of 37.2% for hospitalizations (A). There has been a substantial increase in the annual incidence of episodes of worsening HF from 25 to 33 events per 100 person-years driven by emergency department visits and outpatient encounters (B).