Although ABT occurs in a substantial minority (30%‐40%) of people and dogs receiving ACE‐inhibitors, predicting which patients are or will be affected is elusive.18, 21 Aldosterone breakthrough occurring with short‐term ACE‐inhibitor monotherapy in this study was independent of angiotensin II, and the ACE gene polymorphism appeared to negatively influence aldosterone concentrations in this group of dogs with preclinical mitral valve disease. Here, ACE is linked to mitral valve disorder.