Generating real-world evidence (RWE) of patients with heart failure requires clinical data elements not commonly found in administrative databases. This presentation compares and contrasts the view of patients with heart failure from the perspective of the PINNACLE® Registry, a large cardiovascular disease registry developed by the American College of Cardiology, with those identified in the Practice Fusion ambulatory electronic health record (EHR) database. Both data sources represent large collections of real-world data (RWD) across the United States, but from different perspectives; where PINNACLE primarily represents cardiologists and related specialists, Practice Fusion contains primary care physicians and specialists in ambulatory, community-based healthcare practices. Differences between these types of data sources have deep implications for identifying key patient populations within RWD sources in terms of both understanding heart failure management, as well as potential recruitment for observational research or clinical trials.