Pulmonary arterial hypertension (PH) is an increase in the pressure within the arteries that supply the lungs. PH can be secondary to a variety of causes, including severe acquired left sided heart disease, certain congenital heart diseases, heartworm disease, pulmonary thromboembolism (blood clot) or any type of primary lung disease. Some of these causes are reversible, but others are not. Mild pulmonary hypertension does not cause any clinical signs. If pulmonary hypertension is severe, it can lead to symptoms, such as respiratory difficulty, syncope (fainting), exercise intolerance, and cyanosis (blue discoloration of gums/tongue).

Non-invasive diagnosis of pulmonary hypertension is possible by performing an echocardiogram (ultrasound of the heart). Additional tests can be performed to help identify the primary cause of the pulmonary hypertension, but in some cases a cause cannot be identified. If an underlying disease process is identified and treatable (pneumonia, for example), it may be possible to improve or even resolve the PH with appropriate therapy. If a primary cause cannot be identified or treated, or if the patient has significant clinical signs associated with pulmonary hypertension, specific therapy directed at the PH can be extremely beneficial. In some patients, oxygen supplementation is very important during the first few days of treatment to help the patient breathe more comfortably.

Specific medications, such as Sildenafil (Viagra) can be given to help dilate the pulmonary vessels without causing low blood pressure. Severe pulmonary hypertension can carry a poor prognosis, but treatment with Sildenafil (Viagra) and some other similar medications have led to significant improvements or resolution of clinical signs in many patients.