FCN3 and heart failure: Instead, most of the studies on ficolin-3 have focused on diseases such as autoimmune system and inflammation.6-8 In this study, the role of ficolin-3 and C5b-9 in heart failure was studied to explore the relationship between ficolin-3 and C5b-9 and cardiac function in patients with heart failure, so as to provide new methods for the diagnosis and prognosis of heart failure, and to conceive new treatment ideas and schemes for delaying the progression of heart failure.