Between patients with CHD and IPAH, we distinguished the most common correlations, as many as 15, such as age and 6MWT (negative); age and mPAP (negative); age and PASP (negative); 6MWT and RVSP (positive); 6MWT and PASP (positive); CD19+ and CD4+/CD8+ (positive); PVR and mPAP (positive); CD45+ and CD4+ (positive); CD4+ and CD4+/CD8+ (positive); CD45+ and CD8+ (positive); ASP and RVSP (positive); and CO and IL-2 concentration and NT-proBNP and IL-10 concentration, for both of which the correlations were positive in patients with CHD and negative in patients with IPAH. The gene discussed is CD4; the disease is idiopathic pulmonary arterial hypertension.