In humans, iron deficiency represents a relevant occurrence in heart failure (HF), with or without anaemia, and is associated with the worst outcome. Moreover, chronic kidney disease (CKD) is a well-known comorbidity of HF and is strongly associated with the risk of developing anaemia. The most common cause of HF in dogs is myxomatous mitral valve disease (MMVD). To the best of our knowledge, no studies have examined the iron status in dogs with HF, with and without CKD. The aim of this retrospective study was to evaluate the iron status in dogs affected by MMVD and how strong is the relation with HF.

The retrospective study included 54 dogs with complete case records, echocardiography and laboratory analyses. Iron status was evaluated by measuring serum iron concentration (SIC), un- saturated iron binding capacity (UIBC), total iron binding capacity (TIBC), and percentage of saturation (%SAT).

The prevalence of dogs showing low serum iron concentration (SIC) was 18% in the whole population, 33% in symptomatic patients, 100% in dogs with acute decompensated HF. No signif- icant differences in SIC, UIBC, TIBC and %SAT median values were found among dogs classi- fied in different ACVIM (American College of Veterinary Internal Medicine) classes, between symptomatic and non-symptomatic patients, and among IRIS (International Renal Interest Soci- ety) classes. Azotemic and non-azotemic patients presented a significant difference in SIC mean values (p=0.02). Generalised linear model (GLM) revealed that dogs with low SIC were at high- er risk of being included in a higher ACVIM class (OR=6.383, p-value=0.014).

Log-rank analysis showed shorter survival in dogs with low SIC (p=0.020), multivariate Cox analysis revealed that only HF symptoms can affect survival.

Myxomatous mitral valve disease (MMVD) is a cardiac condition commonly found in older dogs. The disease process can lead to heart failure (HF). In HF, an increase of reactive oxygen species (ROS) and abnormal mitochondrial activity, as well as apoptosis, have been reported. Humanin (HN) is a polypeptide that has a cardioprotective effect against apoptosis and oxidative stress. The purposes of this study were (1) to investigate the potential role of plasma HN as a cardiac biomarker to predict disease progression of MMVD, and (2) to compare plasma HN concentrations with plasma NT-pro BNP concentrations. Thirty-one dogs were included in the study. The dogs were separated into four groups: Group 1 was healthy dogs (n = 8), Group 2 was MMVD class B (n = 8), Group 3 was MMVD class C (n = 8), and Group 4 was MMVD class D (n = 7). All dogs were given a physical examination, thoracic radiography, echocardiography, and samples of their blood were collected for hematology and blood chemistry analysis. Levels of plasma HN and plasma NT-proBNP were also investigated. The results showed that plasma HN levels were lower in the dogs with MMVD and that lower plasma HN levels were associated with greater severity of MMVD-induced HF. It was possible to observe changes in plasma HN levels at a less severe disease stage than plasma NT-proBNP in dogs with MMVD. These findings sug- gest that a decreased plasma HN level can be used as a biomarker to identify dogs with MMVD -induced HF.