Secondary pulmonary hypertension (PH) is high blood pressure in the arteries of the lungs that occurs as a result of an underlying medical condition. Unlike primary (or idiopathic) pulmonary hypertension, which has no identifiable cause, secondary PH is a complication of another disease.
Causes:
Secondary PH develops due to various underlying conditions that affect the pulmonary arteries or the left side of the heart. These conditions can be broadly categorized as:
- Left heart disease: Conditions such as mitral valve disease, aortic valve disease, heart failure with preserved ejection fraction (HFpEF), and heart failure with reduced ejection fraction (HFrEF) can increase pressure in the left atrium, which then backs up into the pulmonary circulation.
- Lung diseases: Chronic lung conditions that cause low oxygen levels (hypoxia) or damage the lung tissue can lead to pulmonary vasoconstriction (narrowing of the blood vessels) and increased pulmonary artery pressure. Examples include:
- Chronic obstructive pulmonary disease (COPD)
- Interstitial lung diseases (e.g., pulmonary fibrosis)
- Sleep-disordered breathing (e.g., obstructive sleep apnea)
- Chronic blood clots in the lungs: Pulmonary embolism, especially when recurrent or unresolved, can lead to chronic thromboembolic pulmonary hypertension (CTEPH).
- Connective tissue diseases: Autoimmune diseases like scleroderma, lupus, and rheumatoid arthritis can affect the blood vessels in the lungs.
- Other conditions:
- Sickle cell anemia
- Liver disease (cirrhosis)
- HIV infection
- Congenital heart defects
Symptoms:
The symptoms of secondary PH are often similar to those of primary PH, but they may be overshadowed or attributed to the underlying condition. Symptoms may include:
- Shortness of breath (dyspnea), initially during exertion and later at rest
- Fatigue
- Chest pain
- Dizziness or lightheadedness
- Swelling in the ankles, legs, or abdomen (edema)
- Rapid heartbeat (tachycardia)
- Cough
- Bluish discoloration of the lips or skin (cyanosis)
Diagnosis:
Diagnosing secondary PH involves identifying both the pulmonary hypertension and the underlying cause. Diagnostic procedures include:
- Medical history and physical examination: To assess symptoms, risk factors, and potential underlying conditions.
- Echocardiogram: An ultrasound of the heart to estimate pulmonary artery pressure and assess heart function.
- Pulmonary function tests (PFTs): To evaluate lung function and identify underlying lung diseases.
- Chest X-ray: To visualize the lungs and heart.
- CT scan: To provide detailed images of the lungs and pulmonary arteries, which is particularly important in diagnosing CTEPH.
- Right heart catheterization: The gold standard for diagnosing PH. It directly measures the pressures in the heart and pulmonary arteries and assesses how well the heart is pumping.
- Blood tests: To check for underlying conditions (e.g., connective tissue diseases, liver disease, HIV) and assess overall health.
- Ventilation-perfusion (V/Q) scan: To evaluate blood flow and airflow in the lungs, primarily used to diagnose CTEPH.
Treatment:
The primary goal of treatment for secondary PH is to manage the underlying condition and alleviate the symptoms of pulmonary hypertension. Treatment strategies may include:
- Treating the underlying condition: Addressing the root cause is crucial. For example:
- Medications or surgery for left heart disease
- Oxygen therapy, bronchodilators, or pulmonary rehabilitation for lung diseases
- Anticoagulation and pulmonary thromboendarterectomy (PTE) surgery for CTEPH
- Immunosuppressive therapy for connective tissue diseases
- Pulmonary hypertension-specific medications: These medications can help to dilate the pulmonary arteries, reduce pulmonary artery pressure, and improve symptoms:
- Phosphodiesterase-5 (PDE-5) inhibitors (e.g., sildenafil, tadalafil)
- Endothelin receptor antagonists (ERAs) (e.g., bosentan, ambrisentan)
- Prostanoids (e.g., epoprostenol, treprostinil)
- Soluble guanylate cyclase (sGC) stimulators (e.g., riociguat)
- Oxygen therapy: To maintain adequate oxygen levels, especially in patients with PH secondary to lung disease.
- Diuretics: To reduce fluid buildup and swelling.
- Lung transplantation: May be an option in severe cases that do not respond to other treatments.
The management of secondary PH often requires a multidisciplinary approach involving cardiologists, pulmonologists, and other specialists, depending on the underlying condition.
