Pulmonary Hypertension

The signs of pulmonary hypertension can mimic those of many respiratory and cardiac diseases, which is part of why a specialist evaluation is so important. Common signs include:

• Persistent cough — may be mistaken for a respiratory infection
• Labored or rapid breathing (dyspnea/tachypnea), especially after minimal activity
• Exercise intolerance — tiring quickly or refusing to exercise
• Fainting or sudden collapse (syncope) triggered by exertion or excitement, caused by a sudden drop in cardiac output
• Blue- or gray-tinged gums (cyanosis) — indicating that blood is not being adequately oxygenated
• Abdominal distension from right-sided heart failure and fluid accumulation
• General weakness and lethargy

Some pets with mild PH have no obvious symptoms, and the condition is discovered incidentally during a cardiac ultrasound performed for a murmur or another concern. Any unexplained breathing difficulty or fainting episode should be evaluated promptly.

PH is classified by its underlying cause, and identifying that cause is essential to choosing the right treatment:

• Left-sided heart disease — the most common cause in dogs; conditions like mitral valve disease or dilated cardiomyopathy raise pressures that back up through the pulmonary circulation
• Chronic respiratory or airway disease — bronchitis, tracheal collapse, and pulmonary fibrosis (particularly in West Highland White Terriers) increase resistance in the lung vessels over time
• Heartworm disease — adult worms living in the pulmonary arteries cause direct obstruction and inflammation; even treated heartworm can leave lasting vascular damage
• Pulmonary thromboembolism (PTE) — blood clots lodging in the lung arteries, often secondary to conditions such as protein-losing nephropathy, hyperadrenocorticism (Cushing's disease), immune-mediated hemolytic anemia, or cancer
• Congenital cardiac shunts — abnormal connections between heart chambers or great vessels that expose the pulmonary circulation to abnormally high pressure or blood flow from birth
• Idiopathic PH — in a minority of cases no underlying cause is identified; more common in small-breed dogs

Small and toy breeds appear to be overrepresented, likely because of their predisposition to both mitral valve disease and chronic airway disease.

Because so many conditions can lead to PH, the diagnostic process has two parallel goals: confirm elevated pulmonary pressures and identify the underlying cause.

• Echocardiogram (cardiac ultrasound) — the cornerstone of PH diagnosis; Dr. D'Urso uses Doppler measurements of tricuspid regurgitation (a small backflow jet through the tricuspid valve, present in most dogs with PH) to estimate pulmonary artery pressure. The echo also assesses right-heart enlargement and rules out or identifies left-sided disease or congenital defects.
• Chest radiographs (X-rays) — evaluate lung patterns for chronic airway disease, pulmonary fibrosis, or fluid; assess heart size and the size of the main pulmonary artery
• Heartworm antigen test — performed in any patient with unexplained respiratory signs or suspected PH, especially in dogs with outdoor exposure
• Blood panel and urinalysis — screen for protein-losing nephropathy, Cushing's disease, and other systemic diseases associated with thromboembolism
• Electrocardiogram (ECG) — identifies right-sided enlargement patterns and concurrent arrhythmias
• Pulse oximetry and arterial blood gas — quantify the degree of oxygen impairment when needed

Treatment has two simultaneous priorities: reduce pulmonary artery pressure to protect the right heart, and treat the underlying cause aggressively.

• Sildenafil (Viagra) — the most widely used pulmonary vasodilator (blood-vessel relaxer) in veterinary medicine; works by selectively dilating the pulmonary arteries, lowering resistance, and reducing the workload on the right ventricle. It does not cure PH but can significantly improve quality of life and exercise tolerance.
• Treating the underlying disease — managing left-sided heart failure with diuretics and pimobendan, treating heartworm disease per established protocols, or addressing chronic airway disease with bronchodilators and anti-inflammatory medications
• Tadalafil — a longer-acting alternative to sildenafil used in some patients
• Oxygen supplementation — beneficial during acute decompensation to relieve breathing difficulty
• Anti-clotting therapy — used when PTE is confirmed or strongly suspected as the contributing cause

Prognosis varies widely depending on the underlying cause and the severity of right-heart changes at diagnosis. Dogs with PH secondary to well-controlled left-sided heart disease often respond better than those with primary lung disease or idiopathic PH. Regular monitoring with repeat echocardiograms helps guide dosage adjustments and catch progression early.

Any dog or cat with a persistent unexplained cough, breathing difficulty, or a fainting episode deserves a thorough cardiac evaluation — especially if chest X-rays or routine bloodwork have not provided a clear answer. Pulmonary hypertension is frequently underdiagnosed because its signs overlap with so many other conditions, and a Doppler echocardiogram is the only reliable way to confirm elevated pulmonary pressures without invasive testing. If your pet has known heart disease or chronic airway disease and is developing new symptoms, PH may be a developing complication that warrants re-evaluation. Dr. D'Urso performs echocardiograms and pulmonary pressure estimates on-site, allowing our team to adjust the diagnosis and treatment plan in one visit rather than coordinating across multiple facilities. Book an appointment to have your pet evaluated.