This single-center prospective case-control study, conducted from December 1, 2015 to January 1, 2017 in Tehran Heart Center, evaluated gene expression of IL-17, relative count of (CD4+IL17+) Th17 cells and CD4+ helper T-cells in peripheral blood mononuclear cells of 42 patients with CHF and 42 matched controls. Here, IL17A is linked to congestive heart failure.