Pulmonary hypertension; demystifying the disorder

Pulmonary hypertension (PHT) can be difficult to diagnose, but is a relatively common disorder, in older, small breed dogs. It can be the result of many different disease processes and can be classified depending on the underlying aetiology. PHT can be the result of left-sided heart disease, such as acquired or congenital cardiac conditions; respiratory diseases like interstitial lung disease or chronic obstructive pulmonary disease; pulmonary thromboembolism; idiopathic lung conditions, or miscellaneous disease processes including those caused by Angiostrongylus vasorum and Dirofilaria immitis. Dogs are generally presented to the veterinary practitioner because of coughing or other respiratory signs. In its most severe form owners may observe their dog to be syncopal or cyanotic.

Diagnosis of PHT is reliant on imaging modalities, specifically Doppler echocardiography. Echocardiography is used to determine the severity of PHT and to look for associated cardiac pathology (cor pulmonale). Peak tricuspid and/ or pulmonic regurgitant velocities are measured to classify PHT in terms of severity. Thoracic imaging such as radiography or computed tomography should also be performed in dogs and cats where PHT has been identified to try and determine the underlying cause.

Treatment of PHT is aimed at alleviating the underlying cause, wherever possible. For animals with clinical signs, medical therapy to directly target PHT can be considered, such as with the phosphodiesterase-5 inhibitor, sildenafil. Other drugs, such as the endothelin antagonist bosentan, are also available but tend to be prohibitively expensive. Prognosis depends on the underlying cause and the severity of the pulmonary hypertension. This article reviews the evaluation, diagnostic process and treatment options available for dogs and cats with pulmonary hypertension