Pulmonary hypertension (PH) is a condition marked by high blood pressure in the arteries of the lungs. Among its different forms, pulmonary arterial hypertension (PAH) and chronic thromboembolic pulmonary hypertension (CTEPH) are two serious and distinct subtypes. Though they may seem similar, their causes, diagnosis, and treatments differ significantly. Understanding these differences is crucial for accurate diagnosis and effective management.
What Is Pulmonary Arterial Hypertension (PAH)?
PAH is a type of pulmonary hypertension characterized by narrowing of the small arteries in the lungs. This causes increased resistance to blood flow and elevated pressure in the pulmonary arteries. Over time, the right side of the heart works harder, leading to right heart strain and eventually heart failure.
Causes of PAH
PAH can occur without a known cause (idiopathic), or be linked to other conditions. Common causes include:
- Connective tissue diseases (like scleroderma or lupus)
- HIV infection
- Liver disease (portal hypertension)
- Congenital heart disease
- Use of certain drugs or toxins (e.g., appetite suppressants)
Symptoms of PAH
Symptoms are often non-specific and may include:
- Shortness of breath during activity
- Fatigue
- Chest pain
- Fainting spells (syncope)
- Swelling in ankles or legs
What Is Chronic Thromboembolic Pulmonary Hypertension (CTEPH)?
CTEPH is a form of pulmonary hypertension caused by old, organized blood clots in the pulmonary arteries. These clots block blood flow and increase pressure in the lung circulation. Unlike PAH, CTEPH is potentially curable through surgery in eligible patients.
Causes of CTEPH
CTEPH develops as a long-term complication of pulmonary embolism (PE), a condition where a blood clot travels to the lungs. In most people, clots dissolve after treatment. But in some, parts of the clot remain and form scar tissue that narrows or blocks pulmonary arteries.
Risk factors for CTEPH include:
- History of multiple pulmonary emboli
- Abnormal clotting disorders
- Spleen removal (splenectomy)
- Infected shunts or catheters
Symptoms of CTEPH
Like PAH, CTEPH may show signs such as:
- Shortness of breath
- Exercise intolerance
- Fatigue
- Chest discomfort
- Swelling in legs
However, CTEPH symptoms usually appear after a prior pulmonary embolism.
Diagnostic Differences Between PAH and CTEPH
Accurate diagnosis is essential because treatment differs. The evaluation includes:
Right Heart Catheterization
This test measures pulmonary artery pressure directly and is used to confirm both PAH and CTEPH.
Ventilation/Perfusion (V/Q) Scan
This nuclear scan is key in identifying CTEPH. It shows areas of the lungs that are ventilated but not perfused due to blockages. It is more sensitive than CT for CTEPH.
CT Pulmonary Angiography and Pulmonary Angiogram
These imaging tests can reveal organized clots or scarring in the pulmonary arteries, helping to diagnose CTEPH. They are less helpful in PAH.
Other Tests
- Blood tests to screen for autoimmune disease
- ECG and echocardiogram to evaluate heart function
- 6-minute walk test to assess exercise capacity
Treatment Approaches
Treatment of PAH
PAH requires lifelong medical therapy. Options include:
- Endothelin receptor antagonists: Reduce blood vessel constriction (e.g., bosentan, ambrisentan)
- Phosphodiesterase-5 inhibitors: Improve nitric oxide effect (e.g., sildenafil, tadalafil)
- Prostacyclin analogs: Relax blood vessels and improve flow (e.g., epoprostenol, treprostinil)
- Guanylate cyclase stimulators: Enhance vasodilation (e.g., riociguat)
- Supportive care: Oxygen, diuretics, anticoagulants, supervised exercise
Treatment of CTEPH
Unlike PAH, CTEPH may be curable in many patients.
Pulmonary thromboendarterectomy (PTE): A surgery to remove clots from pulmonary arteries. It is the gold standard treatment and may offer complete recovery.
Balloon pulmonary angioplasty (BPA): A catheter-based procedure used in inoperable cases to open blocked arteries.
Riociguat: The only approved drug for inoperable or residual CTEPH.
Anticoagulation: Lifelong blood thinners are essential to prevent new clots.
Prognosis and Life Expectancy
Prognosis in PAH
PAH is a progressive disease. With modern therapies, 5-year survival rates have improved to over 65–75%, especially with early diagnosis and aggressive treatment. Without treatment, life expectancy is much shorter, often 2–3 years after diagnosis.
Prognosis in CTEPH
CTEPH patients who undergo successful surgery can be cured. Survival rates post-surgery are excellent, with many patients living normal or near-normal lives. For inoperable cases, prognosis depends on how well medical therapy or BPA works. Survival rates are better compared to untreated PAH, especially when diagnosed early.
Key Differences Between PAH and CTEPH
| Feature | PAH | CTEPH |
|---|---|---|
| Cause | Unknown or linked to systemic diseases | Chronic blood clots in pulmonary arteries |
| Curability | No cure, managed with medications | Often curable with surgery |
| Main Diagnostic Tool | Right heart catheterization | V/Q scan and pulmonary angiogram |
| Medical Treatment | PAH-targeted drugs | Riociguat, anticoagulants, BPA if needed |
| Surgical Treatment | Not applicable | Pulmonary thromboendarterectomy (PTE) |
Conclusion
PAH and CTEPH are both serious forms of pulmonary hypertension. While their symptoms may appear similar, the underlying causes, treatments, and outcomes are very different. PAH arises from narrowing of lung arteries due to various causes and requires long-term medication. CTEPH stems from unresolved blood clots and may be cured with surgery.
Accurate and early diagnosis is essential. Right heart catheterization, imaging, and history of prior clots help distinguish between the two. Treatment should be based on a comprehensive evaluation by a pulmonary hypertension specialist. Understanding these differences improves outcomes and offers hope to many patients facing these conditions.
Related topics: