Benefits of Long-Term Combination Therapy with Sildenafil Citrate and Beraprost Sodium in a Dog with Pulmonary Hypertension

A 12-year-old, spayed female Pekingese dog was presented with frequent syncope and exercise intolerance.Thoracic auscultation revealed a grade 4 heart murmur bilaterally and respiratory sinus arrhythmia.Electrocardiography indicated right axis deviation, suggesting right ventricular hypertrophy.Thoracic radiographs showed normal vertebral heart score of 9, vertebral left atrial size of 2.1, and intercostal space of 3.2, with an increased contact area between the sternum and right heart.Echocardiography revealed moderate tricuspid regurgitation and severe pulmonary hypertension (velocity 4.48 m/s; pressure gradient 80.4 mmHg).Based on diagnostic findings, congenital shunts, left-sided heart disease, tracheobronchial disease, pulmonary embolism, and heartworm disease were excluded, leading to a diagnosis of right-sided heart failure secondary to brachycephalic obstructive airway syndrome, with the characteristic narrow nostrils observed in the pekingese breed.The initial treatment with sildenafil citrate, along with pimobendan, enalapril maleate, and furosemide for right-sided heart failure, failed to improve syncope or pulmonary hypertension after three months.Beraprost sodium, a prostacyclin analog, was added, resulting in significant improvement in syncope despite unchanged echocardiographic findings (velocity 4.42 m/s; pressure gradient 78.2 mmHg).Clinical improvements persisted for 12 months with a regimen of sildenafil citrate (3 mg/kg PO bid) and beraprost sodium (20 g/kg PO bid).