Red blood cell abnormalities occur in dogs with congenital ventricular outflow tract obstruction.

Objective: To document RBC abnormalities in dogs with congenital ventricular outflow tract obstruction.

Animals: 62 dogs with pulmonic stenosis (PS) or aortic stenosis (AS) and 20 control dogs were recruited.

Procedures: The proportions of RBCs that were schistocytes, acanthocytes, and keratocytes were assessed. Complete blood cell counts were performed. Tested variables included hemoglobin concentration, hematocrit, and erythrocyte count.

Results: Median (interquartile range [IQR]) peak systolic Doppler-derived trans-stenotic pressure gradient (∆P) values were 161 mm Hg (108 to 215 mm Hg) and 134 mm Hg (125 to 165 mm Hg) for dogs with PS and AS, respectively. Hematologic abnormalities were detected in most dogs with AS or PS (54/62 [87%]) versus 8/20 [40%] in control dogs, with schistocytes found in 40 of 62 (65%; median, 0.1% RBCs; IQR, 0% to 0.3%), acanthocytes in 29 of 62 (47%; median, 0.3% RBCs; IQR, 0% to 0.9%), keratocytes in 39 of 62 (63%; median, 0% RBCs; IQR, 0% to 0.2%), and hemolytic anemia in 4 dogs with PS. No significant association was identified between these abnormalities and ∆P. However, 3 of 4 dogs with anemia had a ∆P > 200 mm Hg (range, 242 to 340 mm Hg). The dog with the highest ∆P value also had the most severe anemia and schistocytosis, and both resolved after balloon valvuloplasty.

Clinical Relevance: Poikilocytosis is common in dogs with congenital ventricular outflow tract obstruction, with anemia only observed in few dogs with high ∆P values.