What is Idiopathic Pulmonary Artery Hypertension?
Pulmonary hypertension, also known as idiopathic pulmonary artery hypertension (IPAH), is a disease that gradually worsens and affects the small blood vessels in the lungs. We’re not sure what the exact risk factors for IPAH are at this point. The pressure in the lung arteries is consistently over 25 mmHg when resting and over 30 mmHg when exercising. IPAH is rare but deadly, with a high death rate. If it’s not treated, the pressure can build up and lead to heart failure and death.
The World Health Organization (WHO) classifies primary pulmonary hypertension as part of group 1 in their classification system aimed at determining the cause or mechanism of pulmonary hypertension:
1. Group 1: Pulmonary arterial hypertension (PAH), also known as primary pulmonary hypertension, can occur on its own or can be due to birth defects in the heart, liver disease, persistent high blood pressure in a newborn, conditions that affect the body’s connective tissues, or HIV infection.
2. Group 2: Pulmonary hypertension that happens because of heart disease (pulmonary venous hypertension)
3. Group 3: Pulmonary hypertension linked with low oxygen levels in the blood
4. Group 4: Pulmonary hypertension caused by long-term blood clot disease, blockages of lung blood vessels, or both
5. Group 5: Other causes
What Causes Idiopathic Pulmonary Artery Hypertension?
The exact cause of idiopathic pulmonary hypertension, a type of high blood pressure that affects the lungs, is not clear. However, it is known that some instances of this disease are inherited in families due to a defect in a particular gene. This gene defect makes the blood vessels in the lungs more likely to tighten or constrict, leading to the condition.
But it’s not only about genetics. Environment also has a role to play. Things like sudden low levels of oxygen can cause the arteries throughout the rest of the body to expand or dilate, while making the arteries in the lungs constrict. This emphasizes the fact that both gene and environmental factors are involved in this lung disease.
Risk Factors and Frequency for Idiopathic Pulmonary Artery Hypertension
IPAH, also known as Idiopathic Pulmonary Arterial Hypertension, is a rare condition that only affects a small number of people globally, including approximately four million people in the United States. Unfortunately, it’s responsible for nearly 140 deaths in the United States each year. IPAH is more frequently found in women and is typically diagnosed during their forties.
- IPAH is a rare disease, affecting 4 to 6 out of every one million people worldwide, and four million in the United States.
- Approximately 140 people die from IPAH in the United States each year.
- The disease is more commonly observed in women.
- Most cases are diagnosed during the patient’s fourth decade of life (their 40s).
Signs and Symptoms of Idiopathic Pulmonary Artery Hypertension
Exertional dyspnea, or shortness of breath during exertion, is often the first symptom of the disease. Because these symptoms are quite common to many conditions, it often leads to delayed diagnosis. As the condition progresses, additional symptoms such as fatigue, near fainting, actual fainting, heart palpitations, chest pain or angina due to the right side of the heart not getting enough oxygen, and swelling in the legs and ankles might appear. Severe symptoms typically indicate a failing right heart.
Physical examination can reveal signs that show an increase in pressure in the pulmonary blood vessels. These signs include distention of the jugular veins in the neck, increased second heart sound due to the pulmonary component of the sound, a possible fourth heart sound on the right side, and a heart murmur caused by imperfect function of the tricuspid valve.
- Exertional dyspnea (Shortness of breath during exertion)
- Fatigue
- Near fainting
- Fainting
- Heart palpitations
- Chest pain or angina (Due to the right side of the heart not getting enough oxygen)
- Swelling in the legs and ankles
- Jugular veins distention
- Increased second heart sound
- Right-sided fourth heart sound
- Tricuspid regurgitation murmur.
Testing for Idiopathic Pulmonary Artery Hypertension
Doctors may think that a patient has primary pulmonary hypertension (PAH), but it’s hard to diagnose just using medical history and physical exams alone. This is due to its common symptoms and how similar it is to many heart and lung diseases. So, other possible causes of pulmonary hypertension need to be ruled out.
A chest X-ray may show enlarged central pulmonary arteries, a thickened right ventricle of the heart, and clear lungs. An electrocardiogram (ECG) might display an enlargement of the right ventricle and right atrium, a rightward shift of the heart’s electrical axis, and a larger than normal P wave – a sign of right atrial enlargement.
An echocardiogram is the most sensitive tool to measure the size of the right ventricle and assess its pressure-volume overload. It also gives an estimate of pressure in the pulmonary artery. This test might show enlargement of the right atrium and ventricle, and regurgitation of the tricuspid heart valve.
Analysis of arterial blood may show a larger than normal difference in oxygen concentration between arterial and alveolar blood and low arterial oxygen concentration. Lung function tests may reveal impaired gas exchange in the lungs. Perfusion lung scans can help rule out blockage in the lung arteries caused by blood clots. Liver function tests, autoimmune tests, and HIV tests can be used to rule out other possible causes in high-risk patients.
The gold standard test is a cardiac catheterization of the right heart because it measures accurate pressures. Patients with PAH have high mean pulmonary artery pressures, both at rest and during exercise, with normal pulmonary capillary wedge pressure. The presence of fluid in the sac surrounding the heart is a sign of poor prognosis.
Finally, people diagnosed with PAH through cardiac catheterization should go through vasoreactivity testing. These tests use short-acting drugs that widen the blood vessels in the lungs. If the average pressure in the pulmonary artery drops significantly without a decrease in the heart’s pumping efficiency, it means that the patient responds to these medications. This is crucial because those patients can be treated with calcium channel blockers and tend to have a better prognosis.
Treatment Options for Idiopathic Pulmonary Artery Hypertension
While there’s no definitive cure for idiopathic pulmonary arterial hypertension (IPAH), treatment is typically guided by the patient’s symptoms and overall health status. The goal of these therapies is to improve the patient’s quality of life by managing symptoms. Medications like calcium channel blockers and vasoactive substances are often considered for IPAH treatment. Some medications might need to be taken in high doses orally, like calcium channel blockers, diltiazem, nifedipine. Yet, these are typically only recommended for patients who have shown a positive response to vasoreactivity testing.
For patients classified as stage II under the New York Heart Association’s (NYHA) guidelines, treatment generally involves oral endothelin receptor antagonists like ambrisentan, bosentan, and macitentan. These medications have been noted to reduce disease-related complications and mortality in some cases. Another group of drugs known as phosphodiesterase type-5 inhibitors (like sildenafil and tadalafil) are also common; these help relax arterial smooth muscles and facilitate pulmonary artery dilation. Non-parenteral prostanoids may also be added to the treatment plan.
For those in stage III or IV, or if earlier therapies are ineffective, prostanoid agents such as epoprostenol, treprostinil, and iloprost might be considered. These can be administered in various ways – intravenously, subcutaneously, or inhaled. However, intravenous administration requires a semi-permanent central venous catheter. Although these treatments have shown improvement in mortality rates, limitations include a high cost and a short lifespan.
Soluble guanylate cyclase stimulators, a new class of drugs currently in clinical trials, may be beneficial in managing pulmonary artery hypertension due to their dual mode of action. Selexipag, another novel drug, acts as a selective IP prostacyclin receptor agonist.
So far, single-drug therapy might provide relief from symptoms but hasn’t been proven to improve prognosis or survival. Therefore, combination therapy is being considered more often, offering a multi-target approach to treating PAH. Using a mix of drugs seems to bring about a better outcome than increasing the dosage of a single drug.
Anticoagulation medication may improve survival rates according to some studies. Supplementary therapies such as diuretics, digoxin, and oxygen might be considered for symptoms management and heart failure progression.
Patients with idiopathic pulmonary hypertension are encouraged to seek care from specialized centers for advanced therapies. When medical therapy loses effectiveness, surgical options, such as atrial septostomy and lung or heart-lung transplantation, are considered.
What else can Idiopathic Pulmonary Artery Hypertension be?
The process of diagnosing the issue is quite complex, mainly because the symptoms don’t point to a specific condition. Here are several possible conditions that share similar symptoms:
- Chronic obstructive asthma
- Anemia
- Heart failure
- Chronic obstructive pulmonary disease (COPD), a type of lung disease
- Cor pulmonale, a condition that causes the right side of the heart to fail
- Dilated cardiomyopathy, a disease of the heart muscle
- Mitral stenosis, a heart valve disease
- Connective tissue diseases, disorders that affect your connective tissues
- Portal hypertension, high blood pressure in the liver
- Obstructive sleep apnea, a sleeping disorder where breathing repeatedly starts and stops
Because these conditions share similar symptoms, it’s essential for healthcare providers to run various tests to accurately identify the problem.
What to expect with Idiopathic Pulmonary Artery Hypertension
The outlook for a condition called idiopathic pulmonary hypertension is generally not good. On average, people who are not treated for this disease typically live for about 2 to 3 years after being diagnosed. One important factor that can predict how long a person with this disease might survive is something called the “NYHA functional class”. Those in class 4 of this scale, for instance, typically live for less than 6 months.
The most critical factor that can affect a person’s prognosis is the function of the right side of the heart, which is also typically the cause of death in advanced stages of this disease. Additionally, pregnant women with advanced idiopathic pulmonary hypertension face a higher risk of death.
Possible Complications When Diagnosed with Idiopathic Pulmonary Artery Hypertension
- Failure of the right side of the heart
- Fluid buildup in the lungs
- Shortness of breath even while resting
- Fluid buildup in the abdomen
- Potential death
