In this study, some proteins (hemopexin—HPX, tetranectin, apolipoprotein, adiponectin, inter-alpha-trypsin inhibitor heavy chain—ITIH, complement, angiotensinogen—ANG, and paraoxanase 1—PON-1) identified in serum of the dogs with CHF due to MMVD had already been identified in previous studies performed in dogs with MMVD [10,11,12,13] and idiopathic DCM [20,21]. Here, ANG is linked to familial dilated cardiomyopathy.