CONDITION
Pulmonary Hypertension
Pulmonary hypertension describes persistently elevated blood pressure in the vessels that carry blood through the lungs. This increased pressure makes it harder for the right side of the heart to push blood forward, and over time the heart muscle may struggle to keep up with the extra work. Owners often arrive at this page because their dog or cat has been coughing, tiring more easily during walks or play, breathing faster than usual, or occasionally collapsing. In some cases, pulmonary hypertension is discovered during investigation of another condition affecting the heart or lungs. The signs can develop gradually and may be subtle at first. This page explores what pulmonary hypertension can look like in daily life, what may be happening in the heart and lung vessels, how the condition is identified through examination and imaging, and the range of approaches that exist to support affected animals.
Why this matters now
Pulmonary hypertension often develops in middle-aged to older dogs and cats, though younger animals can be affected when the condition arises secondary to congenital heart or lung abnormalities. Certain breeds, including Cavalier King Charles Spaniels and West Highland White Terriers, appear more frequently in referral populations, though this may reflect underlying conditions such as mitral valve disease or chronic lung inflammation rather than a direct genetic predisposition to pulmonary vascular changes. In cats, pulmonary hypertension is less commonly diagnosed but tends to surface in the context of advanced heart disease or chronic respiratory conditions.
The time course varies considerably between individuals and depends largely on the underlying cause and the degree of pressure elevation. Some animals develop symptoms gradually over months, with signs becoming more apparent as the right heart muscle thickens and begins to tire. Others may remain relatively stable for extended periods before a threshold is crossed and signs become more obvious. In a smaller number of cases, the condition can progress more quickly, particularly when pulmonary vessel changes are severe or when other heart or lung conditions accelerate the workload on the right heart.
Signals & patterns
Early signals
Reduced stamina during activity
An owner may notice that their dog no longer keeps pace on familiar walks or that their cat seems less interested in play sessions that previously engaged them. The change can be gradual and may initially be attributed to ageing or mood rather than a physical limitation.
Faster breathing at rest
The respiratory rate may creep upward even when the animal is settled and quiet, sometimes becoming apparent only when the owner counts breaths over a minute. This reflects the body's attempt to maintain oxygen delivery when circulation through the lungs is less efficient.
Occasional cough
A dry or soft cough may appear intermittently, often worse after excitement or exertion. In some cases this represents irritation or congestion in the airways; in others it may relate to pressure on airways from enlarged heart chambers or pulmonary vessels.
Subtle change in gum colour
The mucous membranes may appear slightly duller or take a fraction longer to return to pink after gentle pressure. These changes can be very difficult to detect without close familiarity with the individual animal's usual appearance.
Later signals
Abdominal distension
Fluid may begin to accumulate in the abdomen when the right heart struggles to move blood forward effectively, causing congestion in the veins returning from the body. The belly may appear rounder or feel tense, and the animal may seem less comfortable when lying down.
Episodes of weakness or collapse
Brief periods of unsteadiness, stumbling, or collapse can occur when the circulation fails to deliver enough oxygen to the brain during exertion or excitement. These episodes may last only seconds but can be alarming to witness.
Persistent rapid breathing
The respiratory rate remains elevated even during rest, and the animal may appear to be working harder to breathe, sometimes using abdominal muscles in a way that was not previously visible. This reflects ongoing difficulty maintaining adequate gas exchange and oxygen delivery.
Click to read about the biological mechanisms
How this is usually investigated
Investigation typically begins with a careful history of exercise tolerance, breathing patterns, and any episodes of weakness or collapse, followed by physical examination listening for heart murmurs, abnormal lung sounds, or fluid accumulation. When pulmonary hypertension is suspected, imaging and functional tests help to estimate the pressures in the lung vessels and assess how the right heart is coping. The process often unfolds in layers, with initial tests suggesting the possibility and more specialised studies refining the picture.
Physical examination
Echocardiography
Thoracic radiography
Blood tests
Advanced imaging and catheterisation
Options & trade-offs
Management typically involves a combination of approaches tailored to the underlying cause, the degree of pressure elevation, and the presence of right heart strain or other organ involvement. Some owners find that medication improves exercise tolerance and breathing comfort, while others balance treatment burden against modest or uncertain benefit. The course is often one of adjustment over time as the condition and the animal's tolerance of interventions become clearer.
Sildenafil
Sildenafil works by relaxing smooth muscle in the walls of pulmonary arteries, which can lower resistance and reduce the workload on the right heart. It is given orally, usually two or three times daily, and some animals show improved exercise capacity and reduced breathing effort within days to weeks. The medication does not reverse structural changes in the vessels but may slow progression when sustained pressure elevation is reduced.
Trade-offs: Response varies between individuals, and some animals show little clinical improvement despite treatment. Gastrointestinal upset or mild hypotension can occur, and the cost of ongoing medication may be a consideration for some owners. Monitoring typically involves repeat echocardiography to assess whether pressure estimates have fallen and whether the right heart is stabilising.
Diuretics
When fluid accumulation is present—either in the abdomen, chest cavity, or subcutaneous tissues—diuretics such as furosemide help to reduce the volume of circulating blood and ease the workload on the failing right heart. They are often used alongside vasodilators and can improve breathing comfort when pleural effusion is contributing to respiratory signs. Dosing is adjusted according to the degree of congestion and the animal's response.
Trade-offs: Diuretics do not address the elevated pulmonary pressure itself and can lead to dehydration, electrolyte imbalance, or worsening kidney function if dosing is too aggressive. Regular monitoring of renal parameters and body weight is often advised, and some animals require careful titration to balance symptom relief against side effects.
Management of underlying conditions
When pulmonary hypertension arises secondary to left-sided heart disease, chronic lung inflammation, heartworm infection, or thromboembolic disease, addressing the primary condition can reduce pulmonary vascular resistance. This may involve treating mitral valve disease, controlling airway inflammation with corticosteroids or bronchodilators, administering heartworm adulticide or preventive medication, or using anticoagulants when clotting is suspected. The impact on pulmonary pressure varies depending on how reversible the vessel changes are.
Trade-offs: Some underlying conditions are progressive or only partially treatable, and vessel remodelling may persist even when the inciting factor is controlled. Treatment of the primary disease can carry its own risks and costs, and the benefit to pulmonary pressure may not be immediate or complete.
Exercise and environmental modification
Adjusting the intensity and duration of physical activity can help to reduce demand on the heart and lungs, and many owners find that shorter, more frequent walks or play sessions suit their dog better than sustained exertion. Maintaining a calm environment and avoiding extremes of heat or cold may also ease breathing effort. Weight management is relevant in overweight animals, as excess body condition increases oxygen demand and cardiovascular strain.
Trade-offs: Activity modification does not change the underlying pathology but can improve quality of life and reduce the frequency of episodes of breathlessness or fatigue. Finding the right balance requires observation of the individual animal's tolerance, and some dogs or cats remain limited in their capacity despite careful pacing.
Oxygen supplementation
In animals with severe pulmonary hypertension and low blood oxygen levels, supplemental oxygen can be provided at home using concentrators or canisters, typically during episodes of increased respiratory distress. This approach may ease breathing effort and improve comfort in the short term, particularly when hypoxia is contributing to vasoconstriction in the lung vessels.
Trade-offs: Oxygen therapy requires equipment and can be logistically challenging for some households, and not all animals tolerate the mask or nasal cannulae comfortably. The benefit is usually temporary and does not alter the progression of the vascular disease, so it tends to be used as part of palliative care or during acute decompensation rather than as a long-term strategy.
Common misconceptions
"Pulmonary hypertension is the same as systemic high blood pressure."
Pulmonary hypertension refers specifically to elevated pressure in the vessels of the lungs, whereas systemic hypertension describes high pressure in the arteries supplying the rest of the body. The two conditions involve different parts of the circulation, have different causes, and are managed with different medications. An animal can have one without the other, though occasionally both are present.
"Once pulmonary hypertension is diagnosed, exercise must stop completely."
Most animals benefit from adjusted rather than eliminated activity, with the intensity and duration tailored to their individual tolerance. Gentle, regular movement can help maintain muscle condition and mental wellbeing, and many dogs continue to enjoy short walks or play sessions. The goal is to avoid overexertion that triggers breathlessness or collapse, not to confine the animal entirely.
"Coughing always means the condition is getting worse."
Coughing can have many causes in animals with pulmonary hypertension, including concurrent airway disease, compression of bronchi by enlarged heart chambers, or fluid accumulation in the lungs. A change in cough character or frequency may signal progression of heart failure, but it can also reflect a stable chronic bronchitis or a new respiratory infection. The pattern and associated signs help to distinguish between these possibilities.
Related conditions
Pleural Effusion
Pulmonary hypertension can contribute to pleural effusion when the increased pressure in the lung vessels and the strain on the right side of the heart lead to fluid leaking into the chest space. In some cases, pleural effusion may also be investigated as a possible cause of respiratory signs before pulmonary hypertension is identified.
Hypertrophic Cardiomyopathy in Cats
Hypertrophic cardiomyopathy in cats can lead to pulmonary hypertension when impaired filling of the heart causes pressure to build backwards into the vessels of the lungs. This connection means that cats with known heart muscle disease may be monitored for changes in breathing effort or exercise tolerance.
Dilated Cardiomyopathy in Dogs
Dilated cardiomyopathy in dogs can result in pulmonary hypertension when the weakened heart fails to move blood forward efficiently, causing pressure to rise in the pulmonary circulation. Dogs with this heart condition may show overlapping signs such as coughing, reduced stamina, and breathing changes.
Atrial Fibrillation
Atrial fibrillation can occur in dogs with pulmonary hypertension, particularly when the right side of the heart becomes enlarged and strained by the increased pressure in the lung vessels. The irregular rhythm may compound the circulatory challenges and influence how the condition is monitored over time.
Pericardial Effusion
Pericardial effusion can sometimes be considered during investigation of breathing difficulty and exercise intolerance, as it can produce overlapping signs with pulmonary hypertension. In some cases, fluid around the heart may also contribute to changes in circulation that affect pressure in the lung vessels.
Animals with pulmonary hypertension often have other conditions affecting the heart, lungs, or circulation, and exploring those pages may offer a fuller picture of how the various systems interact. The Metabolic Health pillar provides broader context on how oxygen delivery, energy balance, and organ function are maintained across the body. When pulmonary hypertension is suspected or confirmed, conversations with the veterinary team about monitoring frequency, signs to watch for at home, and the goals of treatment can help to shape a plan that fits the individual animal and household.
Last reviewed: 30 June 2026 · Dr Alastair Greenway MRCVS