Inflammatory and immune variables as predictors of survival in dogs with myxomatous mitral valve disease

We aimed to investigate the association between selected inflammatory and immune variables and survival of dogs with myxomatous mitral valve disease (MMVD). We evaluated data of 62 client-owned dogs with MMVD, grouped into preclinical, stable congestive heart failure (CHF) and unstable CHF. Univariate Cox proportional hazards regression analysis was used to quantify the association of white blood cell count, concentrations and percentages of T lymphocytes and their subtypes (T helper lymphocytes, cytotoxic T lymphocytes, double positive T lymphocytes, double negative T lymphocytes) and B lymphocytes with survival. P values < 0.1 in individual groups and P values < 0.05 in the group of all patients were considered significant. Spearman correlation coefficients between significant covariates were calculated to assess the relationships among variables and with survival.

In the preclinical group, percentage of double positive T lymphocytes was negatively associated with survival (hazard ratio (HR) = 2.328; P = 0.051). In the unstable CHF, T lymphocyte (HR = 1.613; P = 0.085), cytotoxic T lymphocyte (HR = 1.562; P = 0.048), double positive (HR = 1.751; P = 0.042), and double negative T lymphocyte (HR = 1.613; P = 0.096) concentrations were negatively associated with survival, as well as cytotoxic T lymphocyte (HR = 1.502; P = 0.007) concentration in the group of all patients. The percentage of T helper lymphocytes was positively associated with survival in the unstable CHF (HR = 0.604; P = 0.053) and in the group of all patients (HR = 0.733; P = 0.044).

The concentration of cytotoxic T lymphocytes positively correlated with left atrial to aortic ratio (LA/Ao) (rho = 0.259, P = 0.037), and peak velocity of early diastolic mitral flow (rho = 0.259, P = 0.039), whereas the percentage of T helper lymphocytes negatively correlated with left atrial to aortic ratio (LA/Ao) (rho = -0.212, P = 0.090) and early to late mitral flow ratio (rho = -0.232, P = 0.072).

Cytotoxic T lymphocytes, T helper lymphocytes, double positive and double negative T lymphocytes as well as biomarkers cardiac troponin I, N-terminal pro-B-type natriuretic peptide, C-reactive protein are implicated in the progression of MMVD.