Pulmonary Hypertension in Cats

Signs of PHT include respiratory distress, coughing, and fluid buildup in the lungs or abdomen. Heart failure is closely associated with pulmonary hypertension as the function of the lungs and heart are closely related. PHT is a serious, life-threatening condition and veterinary help should be sought immediately if signs of PHT appear in your cat.

Pulmonary Hypertension (PHT) is the result of high pulmonary arterial (blood) pressure in the lungs. Cats do not appear to be prone to primary PHT that is due to congenital lung abnormalities, which occurs in other animals. When cats experience PHT it tends to be secondary to another condition that has affected lung functioning, usually by causing obstruction in the arteries or capillaries of the lungs. As capillaries are very narrow they are particularly prone to obstructions that result in oxygen not being properly taken up by the lungs. Common causes of obstruction that may result in PHT in cats are heartworms and blood clots.

Because blood pressure is not routinely monitored by veterinarians, PHT is not usually discovered until after symptoms occur. Because of the serious, life-threatening nature of pulmonary hypertension symptoms to be alert for are:

• Respiratory distress/breathing problems/labored breathing
• Coughing
• Respiratory crackles and wheezes
• Lethargy/reluctance to exercise/fatigue
• Loss of consciousness/fainting
• Abdominal distension
• Symptoms of other condition(s) that are causing PHT e.g. vomiting, fever
• Signs of parasitic infection
• Jugular distention
• Pale mucous membranes due to lack of oxygenation of tissues
• Heart murmur
• Symptoms of heart failure
• Diminished pulse
• Loss of appetite/weight loss
• Bleeding, including coughing blood, blood in urine, eye hemorrhage or nosebleed
• Seizures and neurological symptoms

In cats, PHT is usually secondary to another condition, it does not tend to be caused by genetic abnormalities of the lung. Conditions and causes of PHT include:

• Poisoning/exposure to toxic substances
• Adverse reaction to drugs or medication
• Viral infection
• Bacterial infection
• Chronic airway disease
• Hypoxia from high elevations
• Heart disease
• Upper airway obstruction
• Obstructive pulmonary disease (chronic pneumonia, infectious bronchitis)
• Pulmonary thromboembolism/blood clots/vascular blockage
• Parasitic infection - Heartworm
• Kidney disease

Obesity may be a contributing factor, making an overweight pet more susceptible to PHT.

Routine blood pressure screening is not usually part of regular veterinarian monitoring of your pet's health, therefore, hypertension is usually only discovered after symptoms have occurred. Because PHT in cats is secondary to other conditions, your cat may already be under veterinary care for the underlying condition when PHT symptoms appear. Your veterinarian will perform a complete physical examination including measuring your cat’s blood pressure and taking a medical history of your cat in order to determine possible underlying conditions for pulmonary hypertension symptoms in your cat if causation is not already known from previous diagnosis and treatment.

Urinalysis, blood chemistry and blood gas tests will be ordered to identify possible underlying conditions such as organ failure, bacterial or viral infection, or heartworm infection, and to measure oxygen and carbon dioxide in the blood to determine abnormalities in lung functioning. 

Pulmonary functioning tests may be used to check for obstructions and airway disease. If fluid has built up in the sac around the lungs or in the abdomen, a sample will be taken and analyzed. 

X-rays will reveal abnormalities in the lung or heart. Cardiac catheterization is a standard method of diagnosis for PHT, but more recently a doppler echocardiogram which will reveal blood clots, pressure in vessels, and heart abnormalities has become a more effective method of diagnosis.

Prognosis for PHT in cats is guarded and the outcome will be poor if an underlying condition cannot be identified and successfully treated.

Your veterinarian will treat the underlying condition causing the pulmonary hypertension. Examples of common treatment for secondary conditions are; surgery for removal of heartworms, antibiotic for infections, blood thinners for blood clots, and medications to counteract heart failure or chronic pulmonary disease.

Medications for lowering blood pressure and opening airways will be prescribed and supportive therapy involving oxygen therapy used if necessary. Hospitalization and cage rest during treatment is common.

Prognosis, recovery, and management of PHT depends on its cause. Along with appropriate management of the underlying condition, recovery from PHT will require pet owners to provide rest and a stress-free environment. A low-sodium diet to reduce blood pressure is recommended. If your pet is overweight a weight loss diet will lower their risk of relapsing.