Pulmonary Arterial Hypertension in Canada: Closing the Gaps

There is no single cause of pulmonary arterial hypertension. PAH can be:

• Idiopathic (no identifiable cause)
• Heritable, due to genetic variants such as BMPR2
• Drug or toxin induced, for example certain appetite suppressants
• Associated with other diseases, such as connective tissue diseases, congenital heart disease, portal hypertension, HIV infection or congenital heart defects (shunts).

In many patients, PAH is the result of several factors combined.

The World Health Organization (WHO) classifies pulmonary hypertension into five groups based on the underlying cause:

• Group 1: Pulmonary arterial hypertension (PAH)
• Group 2: Pulmonary hypertension due to left heart disease
• Group 3: Pulmonary hypertension due to lung diseases or low oxygen
• Group 4: Chronic thromboembolic pulmonary hypertension (CTEPH)
• Group 5: Pulmonary hypertension with unclear or multifactorial mechanisms

PAH corresponds specifically to WHO Group 1.

“Pulmonary hypertension” is a broad term that means high blood pressure in the blood vessels of the lungs from any cause.

“Pulmonary arterial hypertension” is a specific subtype (WHO Group 1) where the problem is mainly in the small pulmonary arteries themselves. All PAH is pulmonary hypertension, but not all pulmonary hypertension is PAH. Correctly identifying the group matters because the tests, treatments and prognosis can be very different.

Common symptoms of PAH include:

• Shortness of breath, especially with activity
• Fatigue and reduced exercise capacity
• Dizziness or fainting
• Chest discomfort or chest pain
• Palpitations
• Swelling of the legs, ankles or abdomen in more advanced stages

Symptoms often develop slowly and can be mistaken for asthma, deconditioning or anxiety, which contributes to delayed diagnosis.

Diagnosis usually requires:

• Medical history and physical examination
• Echocardiogram (heart ultrasound)
• Blood tests and lung function tests
• Imaging of the lungs (CT or ventilation perfusion scan)
• Right heart catheterization, which directly measures pressures in the pulmonary arteries and is the gold standard to confirm PAH and assess severity.

Because the workup is complex, people with suspected PAH are typically referred to specialized pulmonary hypertension centers.

Pulmonary arterial hypertension is generally a chronic, progressive disease. At present, PAH is considered not curable and usually cannot be fully reversed. However, modern treatments can improve symptoms, exercise capacity and survival, and in some patients disease progression can be slowed significantly or partially reversed on a functional level.

In rare situations where PAH is caused by another condition that can be treated effectively, marked improvement is possible, but this needs specialist care.

Life expectancy in pulmonary hypertension, and specifically PAH, has improved with modern therapies but still varies a lot from person to person.

Recent studies of PAH show:

• Median survival around 6 to 7 years after diagnosis in many cohorts
• Five year survival rates often in the range of 50 to more than 70 percent, depending on the cause, risk profile, response to treatment and access to specialized care.

These numbers are averages, not predictions for any individual. A pulmonary hypertension specialist can give more personalized information based on detailed risk assessment.

There is no single “best” treatment for pulmonary hypertension or PAH. The right approach depends on the type of pulmonary hypertension, its severity and the underlying cause. For PAH, guideline based therapy typically combines:

• Drugs that target the endothelin pathway (endothelin receptor antagonists)
• Drugs that target the nitric oxide pathway (PDE5 inhibitors or soluble guanylate cyclase stimulators)
• Drugs that target the prostacyclin pathway (prostacyclin analogues or receptor agonists)
• Supportive treatments such as diuretics, oxygen when indicated and supervised rehabilitation

Treatment decisions should always be made with a pulmonary hypertension specialist.

Pulmonary arterial hypertension is usually managed by:

• Pulmonologists or cardiologists with expertise in pulmonary hypertension
• Multidisciplinary teams in specialized pulmonary hypertension or pulmonary vascular disease centers

These teams coordinate diagnostic testing, advanced therapies and long term follow up.

Smoking is a well known risk factor for lung disease and cardiovascular disease. There is growing evidence that tobacco smoke exposure can contribute to pulmonary vascular damage and may increase the risk of pulmonary arterial hypertension in some people, in addition to clearly increasing the risk of pulmonary hypertension related to chronic lung disease.

Even if smoking is not the only cause, quitting smoking is strongly recommended for anyone with pulmonary hypertension or at risk of the condition.

End stage pulmonary hypertension refers to advanced disease where the right side of the heart is severely weakened and symptoms are present even at rest. People at this stage may have:

• Severe shortness of breath with minimal activity
• Marked swelling, abdominal fluid and low blood pressure
• Frequent hospitalizations for right heart failure

Management focuses on intensive medical therapy, evaluation for lung or heart lung transplantation when appropriate, and palliative and supportive care to relieve symptoms and maintain quality of life.