The New York Heart Association (NYHA) Functional Classification was first published in 1928 by the New York Heart Association and has been revised multiple times (1964, 1973, 1994). It is the oldest and most universally used system for quantifying functional limitation due to heart failure, providing a simple 4-class ordinal scale based on physical activity and symptom burden. Despite being entirely subjective and having poor inter-rater reliability (kappa ~0.56), NYHA class has been the primary functional endpoint or stratification variable in virtually every major heart failure clinical trial for nearly a century, including RALES (spironolactone), COPERNICUS (carvedilol), PARADIGM-HF (sacubitril-valsartan), and EMPEROR-Reduced (empagliflozin).