ACE2 and heart failure: Serum ACE2 activity strongly correlated with the clinical condition of patients with severe heart failure (HF - CRT before: NYHAII: 32.3±3.1 UF/mL, NYHAIII: 45.2±2.9 UF/mL, NYHAIV: 64.2±6.2 UF/mL, Figure 2B).