Lactate in Heart Failure.

This narrative review explores the multifaceted role of lactate in heart failure (HF), focusing on its diagnostic and prognostic significance in both acute and chronic HF. Lactate functions not only as a marker of hypoperfusion and anaerobic metabolism but also as an active metabolic substrate. In acute HF, elevated lactate levels often signal circulatory insufficiency and predict adverse outcomes. In chronic HF, especially HFpEF, lactate dynamics during exercise reflect metabolic inefficiency and correlate with functional impairment. This review emphasizes the dual nature of lactate and discusses its potential utility in risk stratification and therapeutic guidance.