What is Secondary Pulmonary Hypertension?
The heart moves blood from its right side to its left side through what is known as the pulmonary circulation. This process often works under low pressure, typically between 10 to 18 mm Hg, and can handle a large amount of blood flow during physical activities. The pressure in this system is controlled by factors like the pressure in the pulmonary arteries, pressure in the left atrium of the heart, and the heart’s overall output.
When the resistance in this system increases, leading to abnormally high pressures in the pulmonary artery, it can result in a condition called pulmonary hypertension. This means that the pressure in the pulmonary arteries remains consistently over 25 mm Hg at rest, and over 30 mm Hg during exercise.
Pulmonary hypertension, or PH, can be of two types: idiopathic (primary) when the cause is unknown, or secondary when it occurs due to other diseases or known risk factors. The most common triggers for secondary PH are underlying heart and lung diseases.
What Causes Secondary Pulmonary Hypertension?
The World Health Organization (WHO) breaks down the cause of high blood pressure in the lungs, also known as Pulmonary Arterial Hypertension (PAH), into different groups according to what is driving the high pressure:
* Group 1: This group involves high lung pressure that arises on its own or from other conditions such as heart defects from birth, liver high blood pressure, high blood pressure in newborn lungs, certain autoimmune diseases, HIV infection, or due to drugs and toxins.
* Group 2: This group comprises high lung pressure resulting from issues with the left side of the heart, such as heart valve disease or restrictive heart muscle diseases. The most common reason for this is due to a stiff or narrow heart valve and problems with the heart not relaxing properly to allow blood to flow in.
* Group 3: This group includes high lung pressure associated with severe lung diseases and low oxygen levels in your blood. It includes conditions such as chronic obstructive pulmonary disease (COPD), diseases that affect the structure of the lung, sleep breathing disorders, and conditions that cause low oxygen in the blood.
* Group 4: This group involves high lung pressure due to blood clots that have been there for a long time, blocking blood flow in your lungs.
The WHO also notes a ‘catch-all’ group 5: This is a mixed group of conditions that lead to high lung pressure:
* Metabolic disorders like glycogen storage disease, thyroid disease, and Gaucher disease.
* Systemic diseases like sarcoidosis, inflammation of blood vessels, and a genetic disorder called neurofibromatosis type 1.
* Blood diseases like disorders that cause an abnormal increase in blood cells.
Other things that can result in Group 5 high lung pressure include end-stage kidney disease requiring dialysis, physical external blockages of the lung vessels, or cases where parts of a tumor have traveled to the lungs.
Risk Factors and Frequency for Secondary Pulmonary Hypertension
Idiopathic pulmonary arterial hypertension (IPAH) is a form of PH that is more common in women. How often this disease happens in other groups is similar to how often it happens in the diseases that cause them.
- The occurrence of group 3 pulmonary hypertension (PH) is often seen in older people.
- The rate at which it happens in patients with COPD (chronic obstructive pulmonary disease) can vary because of certain genetic differences.
- For example, COPD patients with a certain type of genetic difference called the LL serotonin transporter gene polymorphism experience more severe lung pressure compared to those with the LS or SS variants.
Signs and Symptoms of Secondary Pulmonary Hypertension
Group 2 Pulmonary Hypertension (PH) is a condition that primarily causes symptoms like shortness of breath during physical activity, tiredness, and fatigue due to the heart’s struggle to maintain its output, especially during exercise. As this condition worsens, shortness of breath can also happen at rest. Other side effects that a patient with Group 2 PH might experience are difficulty breathing while lying flat (orthopnea), sudden nighttime shortness of breath (paroxysmal nocturnal dyspnea), a dry cough, coughing up blood (hemoptysis), and a hoarse voice. As the disease progresses, chest pain during exertion, fainting, and swelling in the limbs can also occur due to the right side of the heart becoming larger (right ventricular hypertrophy) and potentially leading to heart failure.
The severity of this disease is measured by the New York Heart Association (NYHA) Functional Classification.
When a physical examination is conducted, there are certain signs that might indicate the presence of Group 2 PH. These include a loud second heart sound linked to the pulmonary component (this is usually the first physical sign of the condition), a murmur due to blood flowing in the wrong direction in the tricuspid valve (tricuspid regurgitation murmur), visible swelling of the neck veins (jugular venous distention), an enlarged liver (hepatomegaly), and water retention in the lower legs (edema).
Testing for Secondary Pulmonary Hypertension
If you’re experiencing symptoms that might suggest pulmonary hypertension, your doctor will likely investigate further to rule out other potential causes, as these symptoms are common to many conditions. A test where you walk for six minutes can help assess your overall health.
If pulmonary hypertension seems likely, an echocardiogram (a type of ultrasound) can be used to estimate the pressure within your pulmonary artery and evaluate the function of your heart’s right side. However, some further tests would need to be done to make sure the symptoms aren’t due to other heart or lung diseases. These tests could include an EKG (electrocardiogram), a PFT (pulmonary function test), an arterial blood gas test, a chest x-ray, and a high-resolution CT scan.
A few characteristic signs that might be seen in these various tests include enlargement of the right side of the heart and deviations in the heart’s electrical patterns. In some cases, you might also see signals of left heart disease like fluid accumulation in the lungs.
To check for a specific type of pulmonary hypertension called chronic thromboembolic pulmonary hypertension, a scan that looks at ventilation and blood flow in the lungs (V/Q scan) might be performed. If there are defects in blood flow, further tests such as a CT scan of the pulmonary arteries and an assessment of the right side of the heart might be performed to confirm the diagnosis.
The direct measurement of different heart and lung pressure parameters using a catheter (a small, flexible tube) introduced into the heart and the pulmonary artery can confirm if you have pulmonary hypertension. This invasive test can measure factors like average pulmonary artery pressure, which can help determine your prognosis. High values in both pulmonary artery pressure and the pressure in the lung’s small blood vessels (PCWP) tend to be seen in pulmonary hypertension caused by left heart disease.
Treatment Options for Secondary Pulmonary Hypertension
Before starting treatment, it’s important to understand how severe the condition is. This is done by looking at how well the patient can exercise and how much their heart and blood flow are affected.
The main aim for treating pulmonary hypertension is to address the root cause of the problem. After this first step of treatment, doctors re-evaluate how severe the condition is.
Patients with moderate to severe levels of pulmonary hypertension that doesn’t improve after initial treatment may need a more advanced approach. This focuses on treating pulmonary hypertension directly, instead of the underlying issue causing it. Most people with a specific type of pulmonary hypertension (Group 1 Pulmonary Arterial Hypertension) and some people with Group 3, 4, and 5 will need this advanced treatment. Group 2 patients usually don’t need this type of treatment.
Advanced treatment options include medications called prostacyclin agonists, endothelin receptor antagonists, NO-cGMP enhancers, and in rare cases, calcium channel blockers.
For those whose condition doesn’t improve with initial advanced therapy, doctors may try a combination or different treatment.
For Group 1 patients, primary treatments often don’t work and they usually require advanced therapy.
Group 2 patients are treated with medications or heart valve repair to help the left side of the heart work better. In cases where they have too much fluid in their body, diuretics might be used. Other important parts of their care include managing any other health issues they may have, like high blood pressure or diabetes, and making lifestyle changes.
For Group 3, additional oxygen may be given to increase blood oxygen levels, and efforts are made to treat the underlying cause of low oxygen.
In Group 4, the best way to lessen the strain on the blood vessels in the lungs caused by a chronic blood clot is to have a surgery called a pulmonary thromboendarterectomy. However, this surgery might not be as effective in patients with disease in the small vessels. There can also be side effects after the operation and there’s a chance of the disease coming back.
If surgery isn’t possible or doesn’t work, another option is to use a small balloon to widen the pulmonary artery. Blood thinners and medications that dilate blood vessels might also help. However, these treatments aren’t officially approved for this condition yet.
In the most severe cases, where other treatments have failed, a heart-lung transplant may be considered as a last resort.
What else can Secondary Pulmonary Hypertension be?
Diagnosing pulmonary hypertension can be quite challenging because its symptoms are often similar to other common heart and lung diseases. This overlap typically leads to delays in correct diagnosis. The medical process involves ruling out certain conditions, including:
- Anemia
- Chronic lung conditions like obstructive pulmonary disease (COPD) and pulmonary fibrosis
- Chronic asthma
- Sleep apnea
- Cor pulmonale (a condition that causes the right side of the heart to fail)
- Cardiomyopathy (weakened heart muscle)
- Heart failure
- Coronary artery disease
- Mitral stenosis (a heart valve disease)
- Connective tissue diseases
- Portal hypertension (high blood pressure in the liver)
- Liver disease
- Budd-Chiari syndrome (a rare liver disease)
- Pulmonary embolism (a blood clot in the lungs)
- Hypothyroidism (underactive thyroid)
Basically, the path to diagnosing pulmonary hypertension involves investigating these possibilities and systematically ruling them out.
What to expect with Secondary Pulmonary Hypertension
On average, individuals showing signs of right heart failure or severe pulmonary hypertension (pressure in the pulmonary artery above 55 mm Hg) have a life expectancy of around one year. However, those with a well-functioning right heart and a pulmonary artery pressure below 55 mm Hg, generally survive approximately 3 years.
Patients with untreated IPAH, a type of high blood pressure that affects the arteries in the lungs and the right side of the heart, typically have a median life span of 2 to 3 years.
Possible Complications When Diagnosed with Secondary Pulmonary Hypertension
People who have pulmonary hypertension may experience several complications. These can include:
- Cor pulmonale and right heart failure, which are heart conditions resulting from persistent high blood pressure in the arteries of the lungs
- Alveolar hemorrhage, or bleeding in the lungs
- Pericardial effusion and tamponade, which are complications involving fluid around the heart
- Pulmonary cavitation, which means cavities form within the lung tissue
Preventing Secondary Pulmonary Hypertension
It’s crucial for patients to understand and follow their treatment plans if they have secondary conditions that can cause pulmonary hypertension, a kind of high blood pressure that affects the lungs. Conditions like obstructive sleep apnea, chronic obstructive pulmonary disease, and blood clots in the lungs (venous thromboembolism) could potentially lead to pulmonary hypertension if not managed correctly.
For this reason, individuals diagnosed with any of these conditions should receive proper advice about the risks of not treating their condition effectively. One significant factor that needs reinforcement is the importance of quitting smoking. Especially for patients already diagnosed with pulmonary hypertension, stopping smoking can greatly aid in managing their condition.
