DAO and congestive heart failure: Based on this background, this study aims to further clarify the relationships between certain tag-single nucleotide polymorphisms (SNPs) or previously reported positive SNPs of HRH2, HRH3, DAO, and HNMT genes and CHF risk using case-control method among Chinese Han population hoping to provide novel genetic risk markers for personalized prevention and treatment of CHF, which would eventually inform our understanding of the disease.