Heart Failure: An Updated Review of Classification, Etiology, and Pathophysiology

Heart failure (HF) is a heterogeneous clinical syndrome that remains a leading cause of morbidity, mortality, and health care utilization worldwide. Contemporary efforts to standardize HF terminology have culminated in updated consensus definitions that integrate clinical symptoms and signs with objective corroboration by natriuretic peptide elevation and/or evidence of cardiogenic congestion from imaging, diagnostic modalities, or hemodynamic assessment. In parallel, modern classification frameworks emphasize complementary domains that capture disease trajectory and phenotype, including stage of disease (risk through advanced HF), functional limitation, and left ventricular ejection fraction–based categories. This review summarizes the evolution and current state of HF definitions and classification systems and highlights their implications for clinical care, research design, and trial generalizability. We then synthesize the major etiologic pathways leading to HF, spanning ischemic heart disease, hypertensive and valvular remodeling, genetic and nonischemic cardiomyopathies, inflammatory and infectious causes, toxic/metabolic/endocrine injury, infiltrative and storage disorders, and peripartum cardiomyopathy. Finally, we outline shared pathophysiologic mechanisms that link diverse causes to a common final phenotype, including maladaptive ventricular remodeling, neurohormonal and autonomic activation, inflammation and endothelial dysfunction, microvascular and mitochondrial derangements, cardiorenal and cardiohepatic interactions, and systemic consequences such as skeletal muscle dysfunction and frailty. By integrating definition, classification, etiology, and pathophysiology, this review provides a pragmatic framework to improve diagnostic precision, refine phenotyping, and support mechanism-based prevention and therapy across the HF spectrum.