Updated project metadata. Single cell sequencing in peripheral blood mononuclear cells (PBMCs) revealed a novel human-specific long noncoding RNA called heart-failure associated transcript 4 (HEAT4). HEAT4 expression was assessed in several in vitro and ex vivo models of immune cell activation, as well as in the blood of patients with heart failure (HF), acute myocardial infarction (AMI) and cardiogenic shock (CS). The transcriptional regulation of HEAT4 was verified through cytokine treatment and single cell sequencing. Loss-of-function and gain-of-function studies and multiple RNA–protein interaction assays uncovered a mechanistic role of HEAT4 in the monocyte anti-inflammatory gene program. HEAT4 expression and function was characterized in a vascular injury model in NOD.CB-17-Prkdc scid/Rj mice.