Echocardiographic characteristics of dogs with pulmonary hypertension secondary to respiratory diseases

BACKGROUND: Pulmonary hypertension (PH) secondary to respiratory disease is caused by pulmonary vascular remodeling and hypoxia. Severe PH can induce various clinical signs, including syncope and right‐sided heart failure. HYPOTHESIS/OBJECTIVES: To investigate the echocardiographic characteristics in dogs with PH secondary to respiratory diseases. ANIMALS: Thirty‐one dogs with respiratory diseases with or without PH and 15 healthy dogs. METHODS: Prospective cross‐sectional study. Dogs were classified according to respiratory disease (obstructive airway/lung disease [OALD] or restrictive lung disease [RLD]) and PH‐relevant signs. The association between echocardiographic variables and PH (classified by respiratory disease and PH‐relevant signs) was investigated. RESULTS: Twenty‐one dogs were diagnosed with PH; of these, 11 showed PH‐related signs (OALD, n = 2; RLD, n = 9), 14 had right ventricular hypertrophy, and 19 had pulmonary arterial enlargement. Right ventricular dysfunction and dilatation were observed only in dogs with PH‐related signs (n = 10). Left and right ventricular stroke volumes were significantly lower in dogs with PH (median [interquartile range]: 17.2 [12.4‐20.8] and 16.8 [15.3‐29.5] mL/m(2), respectively). Dogs with RLD had higher echocardiography‐estimated pulmonary vascular resistance than those with OALD (median [interquartile range]: 3.1 [1.9‐3.3] and 1.6 [1.3‐2.2], respectively). CONCLUSIONS AND CLINICAL IMPORTANCE: Pulmonary arterial enlargement was the most common echocardiographic finding in dogs with PH secondary to respiratory diseases. Right ventricular dysfunction, dilatation, and decreased left and right ventricular stroke volume were significantly associated with the PH‐related signs, indicating that comprehensive echocardiography is recommended in dogs with respiratory disease. Restricted lung disease might induce more severe PH than OALD.