Pulmonary hypertension (PH) is defined as a higher pressure than normal in the vessels leading to and traveling through the lungs. In normal circulation, oxygen-depleted blood, returning from body, enters the right side of the heart. From there it is pumped to the lungs through the pulmonary artery to be re-oxygenated. The oxygenated blood then passes back into the left side of the heart to be distributed again to the body. When pulmonary hypertension develops, the right ventricle (lower chamber of the heart) enlarges and works harder to pump blood to the lungs. The pressure increase in the pulmonary vessels can vary and the extent of heart changes and symptoms will depend on the severity of PH. With chronic PH, the right side of the heart can fail (right heart failure) resulting in lethargy, inappetence, and ascites (fluid accumulation in the abdomen). In addition, severe right heart enlargement can impede normal filling of the left heart. Subsequently, the amount of blood pumped to the body is reduced causing muscle weakness, exercise intolerance, and syncope (collapse).

There are various classifications of pulmonary hypertension and the most simplified is to define PH as either primary or secondary. Primary PH is rarely diagnosed in dogs and the majority of cases of PH are secondary to another disease process. Left sided heart diseases (valve disease or dilated cardiomyopathy) and pulmonary (lung) diseases are the most common causes of PH and account for up to 60-80% of cases in dogs. Other causes include heartworm disease, thromboembolic disease (blood clots), congenital heart defects, and high altitudes.

Work-up is largely aimed at determining the underlying cause and includes (but is not limited to) blood work, urinalysis, heartworm test, chest x-rays, and an echocardiogram. The echocardiogram is the least invasive test available to diagnose PH, determine the severity (mild, moderate or severe) and monitor for progression. If the underlying cause can be identified, every attempt will be made to treat it. However, many of the diseases that cause PH cannot be cured. Therefore, additional therapy is directed at lowering the blood pressure in the lungs.

The overall goal of therapy is to improve the length and quality of life with medications. Dog with mild PH are often asymptomatic and may not require medications. Severe PH, however, often results in clinical signs and shortens a dog’s life span. Multiple drugs can be used depending on your pet’s needs and most of the drugs will need to be continued throughout his/her life. Routine reevaluation of your pet is needed in order to provide optimal care.