Objectives: To determine the effect of sildenafil for dogs with Eisenmeger's syndrome and secondary erythrocytosis.
Methods: This is a prospective, single arm, open-label study. Five clinical dogs with Eisenmeger's syndrome and secondary erythrocytosis were included. New York Heart Association functional class, packed cell volume, pulmonary artery acceleration time to ejection time ratio and serum erythropoietin concentration were evaluated before and after sildenafil therapy (0·5 mg/kg, twice a day).
Results: New York Heart Association functional class was significantly improved after one (median 2; range 1 to 2, P=0·031) and three months (median 2; range 1 to 2, P=0·031) of sildenafil therapy, compared with the baseline (median 3, range 2 to 3). Packed cell volume was significantly decreased after three months (median 59%; range 56 to 63, P=0·031) of therapy, compared with the baseline (median 71%; range 58 to 74). Acceleration time to ejection time ratio had increased and serum erythropoietin concentration had decreased particularly after 1 month of therapy, but there was no statistical significance.
Clinical Significance: Sildenafil improved the clinical signs and secondary erythrocytosis in dogs with Eisenmeger's syndrome. Sildenafil therapy could be a useful treatment for dogs with Eisenmeger's syndrome.