RED BLOOD CELL DISTRIBUTION WIDTH IN DOGS WITH PRE-CAPILLARY AND POST-CAPILLARY PULMONARY HYPERTENSION

Red blood cell distribution width (RDW) is a component of the CBC and is a quantitative measurement of anisocytosis. In humans, increased RDW has been recently associated with different cardiovascular and cardiopulmonary disorders, including pulmonary hypertension (PH). The aim of the present study was to evaluate RDW values in dogs with pre-capillary PH (Pre-PH) and post-capillary PH (Post-PH). Dogs were prospectively enrolled and were submitted to physical examination, CBC and serum biochemical profile, and cardiovascular examination including ECG, thoracic radiography and complete echocardiographic and echo-Doppler examination. Based on results of these exams, dogs were divided in healthy dogs (control, n = 31 dogs), dogs with chronic degenerative valvular disease without PH (CDVD-noPH, n = 35 dogs), dogs with CDVD with PH (Post-PH, n = 29 dogs) and dogs with pre-PH (n = 15 dogs). The diagnosis of PH was based on the presence of a tricuspid regurgitation jet maximal velocity ≥ 2.8 m/s in absence of increased right ventricular outflow tract obstruction. Selected echocardiographic, CBC and serum biochemical parameters were compared among groups using ANOVA and Kruskal-Wallis tests for normally and non-normally distributed variables, respectively. The Pearson’s correlation test was used to analyze the correlation between RDW and selected echocardiographic, CBC and serum biochemical parameters. The minimum level of significance was chosen for P < 0.05. Lsmean  SE RDW in dogs with Pre-PH (16.6%  0.3%) was significantly higher compared to that of healthy dogs (12.9%  0.2%, P < 0.001) and that of dogs with CDVD-noPH (13.5%  0.2%, P < 0.05). The median serum urea concentrations of dogs with Pre-PH, Post-PH and CDVD-noPH were significantly higher than that of control dogs (P < 0.001, P = 0.001, and P < 0.001, respectively). In dogs with Pre-PH, the RDW had a significant, positive correlation with serum urea (correlation coefficient, 0.790) and creatinine concentration (correlation coefficient, 0.763), and a significant, negative correlation with the left ventricular diameter at diastole:aorta ratio (correlation coefficient, -0.609). In dogs with Post-PH, the RDW values had a significant, positive correlation with WBC (correlation coefficient, 0.497), right ventricular diameter at diastole (correlation coefficient, 0.504), and the left atrium:aorta ratio (correlation coefficient, 0.384). Results suggest that the RDW can play a role in dogs with Pre-PH but not in dogs with Post-PH. Thromboembolic and/or inflammatory mechanisms involved in the pathophysiology of pre-PH and deterioration of renal function may be responsible of the observed results.