What is Pulmonary Idiopathic Hypertension?
Pulmonary hypertension, or PH, is a condition where the pressure in the lung’s arteries is above 20 mmHg, which doctors measure using a specific type of heart test. A more specific form of this condition is pulmonary artery hypertension, or PAH, which includes patients whose blood pressure just before it reaches the lung’s small vessels is high. Also, the resistance in their lungs to blood flow is above a certain level.
PAH can be broken into three types: idiopathic (appears randomly with no known cause), heritable (passed down through families) and related to risk factors or other health conditions. This discussion will focus on idiopathic pulmonary artery hypertension (IPAH), a random occurrence without family history or specific risks for PAH.
What Causes Pulmonary Idiopathic Hypertension?
High resistance in lung blood vessels is caused by an increase in cells lining these vessels and their surrounding muscles. This leads to the thickening of the walls of small lung arteries. In addition, these lining cells can’t make enough nitric oxide and prostacyclin, which are necessary for smooth functioning.
Patients suffering from inherited and non-specific forms of high blood pressure in the lungs can be identified by a specific genetic mutation. In the non-specific forms, there is a genetic inclination to develop lung hypertension. Either way, both these forms share overlapping genetic changes. Some cases of non-specific pulmonary hypertension have been connected with genetic mutations such as BMPR2, SMAD 1 and 9, KCNK3, and CAV1. While there indeed are genetic elements involved in the development of such cases, environmental factors also play a part.
For example, a study of 340 patients with non-specific high blood pressure in the lungs showed that these patients were over 10 times more likely to have previously used stimulants like amphetamine, methamphetamine, or cocaine in comparison to patients with lung hypertension due to identifiable risk factors.
More research is required to fully understand these findings.
Risk Factors and Frequency for Pulmonary Idiopathic Hypertension
Based on a study of 2039 patients in the US with pulmonary artery hypertension, the average age at diagnosis was about 52, with approximately three times as many females as males affected. Out of these patients, almost half were classified as having Idiopathic Pulmonary Artery Hypertension (IPAH). Typically, IPAH impacts around 1 in every 1 million people and is usually seen in young, healthy women. If IPAH is not treated, the average survival time tends to be around 2.8 years.
- The average age for those with pulmonary artery hypertension is approximately 52 years old.
- The condition affects females more than males, with approximately 4 females for every male diagnosed.
- Almost half of the patients in this study had Idiopathic Pulmonary Artery Hypertension (IPAH).
- IPAH usually affects 1 in a million individuals, often young, healthy women.
- If untreated, IPAH has an average survival time of around 2.8 years.
Signs and Symptoms of Pulmonary Idiopathic Hypertension
Pulmonary hypertension is a medical condition that often presents with a variety of symptoms. Initial signs may be hard to recognize, which is likely why the diagnosis can be delayed, often taking up to two years on average for most patients.
Patients can experience the following symptoms:
- Difficulty breathing
- Fatigue
- Chest pain
- Near fainting or fainting
- Swelling in the lower extremities
During a physical examination, doctors may notice certain signs that might suggest a patient has pulmonary hypertension. It’s important to note, however, that not all patients will have every symptom. Signs may include:
- An exaggerated second heart sound that can be heard using a stethoscope (93% of patients)
- A heart murmur indicative of improper function of the tricuspid valve (the valve between the right atrium and right ventricle of the heart) (40% of patients)
- A heart murmur indicative of improper function of the pulmonic valve (the valve that controls blood flow from the heart to the lungs) (13% of patients)
- Swelling in the hands and feet (32% of patients)
Testing for Pulmonary Idiopathic Hypertension
To diagnose idiopathic pulmonary artery hypertension, which is an unexplained increase in the pressure of the lung’s arteries, all other reasons for high lung artery pressures need to be ruled out. In general, a medical professional will start with the least invasive tests before moving on to a right heart catheterization. This procedure confirms the diagnosis of pulmonary artery hypertension. Blood tests will likely focus on eliminating other potential diseases that can lead to pulmonary hypertension, like certain autoimmune diseases, HIV, liver disease, and certain types of infections.
An electrocardiogram (ECG), lung X-ray, and pulmonary function tests can be helpful in diagnosing pulmonary hypertension. However, none of these tests are specific or sensitive enough to be used for routine screening. On an ECG, there may be signs of change in the direction of the heart’s electrical waves and increased size of the right side of the heart. X-ray findings may show thinner luung markings and enlargement of the lung arteries. Patients with idiopathic pulmonary arterial hypertension may have slightly lower lung volume and forced breath volume. The ability to transfer oxygen in the lungs is also significantly reduced in patients with this condition. It’s important to measure oxygen levels during sleep and exercise, as even slight drops in oxygen can cause further constriction of the lung arteries and increase pressure.
A Doppler echo test is the initial test to consider for patients suspected of having high lung artery pressure. This test uses sound waves to estimate the speed and direction of blood flow in the vessels. However, it’s only around 50% accurate in estimating the pressure in the lung artery. This is due to changes in blood volume, the position of the Doppler probe, and variable estimates of peak blood speed. Estimating pressure with Doppler echocardiography should be part of a comprehensive Doppler examination of the heart as some patients may show signs of increased pressure, such as right heart enlargement or dysfunction, even with underestimated pressure measurements.
To definitely diagnose pulmonary artery hypertension, a right heart catheterization is needed. This procedure provides a full assessment of the blood flow in the heart, including measurements of lung artery pressure, the pressure in the lungs’ small blood vessels, and the resistance to blood flow in these vessels. A procedure on the left side of the heart is often performed at the same time because high pressures in this area can lead to an alternative cause of high lung artery pressures.
The fifth worldwide meeting on pulmonary arterial hypertension defines pulmonary hypertension as a mean lung artery pressure greater than 20 mmHg at rest. Pulmonary artery hypertension is defined as a mean lung artery pressure greater than 20 mmHg at rest, a pressure in the small lung blood vessels less than 15 mmHg, and a measurement of the resistance to blood flow in these vessels greater than 3 Woods units.
Treatment Options for Pulmonary Idiopathic Hypertension
Before starting treatment for Idiopathic Pulmonary Arterial Hypertension (IPAH), doctors need to conduct a test (vasoreactivity testing) to see if certain medications (Calcium Channel Blockers or CCBs) will work. This test is done during a special procedure called a right heart catheterization, where a vasodilator (a drug that widens blood vessels) is given to the patient. The test is considered successful if the patient’s blood pressure in the lung arteries drops and the amount of blood the heart pumps either stays the same or increases, without a drop in the overall body’s blood pressure. If the test is positive, medications like dihydropyridine, nifedipine, or diltiazem could be beneficial for the patient.
For patients in the second category of the World Health Organization (WHO) classifications (WHO Class II), doctors recommend using drugs such as ambrisentan or bosentan, which block a certain substance in the body (endothelin) that can constrict blood vessels. Also, they recommend drugs like sildenafil, which helps relax the blood vessels.
For patients labeled as WHO class III, in addition to the drugs mentioned above, IV (directly into a vein) epoprostenol or inhaled iloprost (both help widen the blood vessels in the lungs) can be used. If the response to these isn’t sufficient, an alternate drug like treprostinil could be given subcutaneously (under the skin). Additionally, if a patient doesn’t tolerate sildenafil, tadalafil may be an option.
For patients in the most severe category (WHO Class IV), direct IV infusion of epoprostenol is the primary treatment. If this doesn’t bring about a good enough response, the doctors might consider a combination therapy of various drugs including others that help widen the blood vessels, block the constricting substance, and help relax the blood vessels. In advanced or rapidly worsening cases, doctors might consider heart and lung surgical therapies. Other treatments, used according to each individual’s conditions, may include oxygen therapy and water pills to manage the body’s fluid balance.
What else can Pulmonary Idiopathic Hypertension be?
To identify if someone has idiopathic pulmonary hypertension, which basically means high blood pressure that affects the lungs with no obvious cause, doctors will want to rule out other conditions that could be causing high pressure in the pulmonary arteries. These may include:
- Heart diseases that are present from birth or develop later
- Veno-occlusive disease, which is a rare condition that blocks the small veins in your lungs
- Any other diseases that affect the lungs
- Chronic hypoventilation, which can be caused by sleep apnea—this is when you stop breathing momentarily while you sleep
- Living at high altitudes for a long period of time
- Liver disease
- Taking certain medications that suppress appetite, or other types of drugs
- Fibrosing mediastinitis, a condition where scars form in the area of your chest that separates your lungs.
So, to make sure they are diagnosing idiopathic pulmonary hypertension correctly, doctors will check for these conditions as part of the process.
What to expect with Pulmonary Idiopathic Hypertension
The REVEAL Registry PAH Risk Score Calculator is a helpful tool for doctors in predicting the survival rates of patients with pulmonary artery hypertension within the next year.
Several factors can decrease survival rates, according to this tool. These factors include:
- Men older than 60 years
- Having pulmonary artery hypertension related to portal hypertension (high blood pressure in the portal vein) or connective tissue disorder
- Family history of pulmonary artery hypertension
- Advanced stages of kidney insufficiency (WHO Class III or IV)
- Resting systolic blood pressure lower than 110 mmHg
- Heart rate higher than 92 beats per minute
- Walking less than 165 meters in a six-minute walk test
- A brain natriuretic peptide level greater than 180 pg/ml (a sign of heart failure)
- Pulmonary vascular resistance greater than 32 Woods units (a measurement of blood flow resistance in the lungs)
- Presence of fluid in the pericardial sac around the heart on an echocardiogram
- Different measures of heart and lung function (TAPSE less than 1.5 cm, or DLCO less than 32%).
Possible Complications When Diagnosed with Pulmonary Idiopathic Hypertension
Pulmonary artery hypertension, also known as pulmonary hypertension, can lead to a range of complications. One such complication is related to the blood vessels. For instance, the pulmonary artery, which carries blood from the heart to the lungs, can become enlarged due to the increased volume and stress on the walls of the vessels. This enlargement could potentially press on and obstruct the main artery that supplies blood to the left side of the heart.
A rare but serious complication that can result from pulmonary hypertension is the tearing or dissection of the pulmonary artery, which is often found during post-mortem examinations. It’s important to note that although this is unusual, it’s linked to heart defects present at birth and to a type of pulmonary hypertension that doesn’t have an obvious cause.
Long-term pulmonary artery hypertension can also lead to an increase in the resistance in these blood vessels which, in consequence, puts more stress on the right side of the heart. This causes the right part of the heart to thicken and eventually expand to cope with the increased blood load. If these adaptations fail, it could result in backflow of blood through the tricuspid valve (tricuspid regurgitation), accumulation of fluid around the heart (pericardial effusion), and potentially liver damage (cardiac cirrhosis).
Complications from procedures related to managing pulmonary artery hypertension also exist. For example, people being treated with a certain type of drug called prostacyclin analogs could develop infections at the site where a central line, a type of catheter, is inserted. This is because the line can become a breeding ground for infection over time, given the chronic nature of the disease.
Recovery from Pulmonary Idiopathic Hypertension
People with lung (pulmonary) hypertension are invariably at a higher risk when it comes to surgeries. The risk level depends on how severe their condition is, along with other associated health problems, and varies from person to person. Particular risks during and after surgery include instability in blood flow (hemodynamic instability) and failure of the right side of the heart. The latter happens when there is increased resistance in the lung blood vessels, which lowers the heart’s output.
To prevent this right-side heart failure, it is essential to keep the resistance in the lung blood vessels as low as possible during and after surgery. Till now, there is no standard treatment for right-side heart failure caused by increased lung blood vessel resistance. The use of drugs to increase blood pressure (pressor support) has limitations, as it can also increase resistance in the lung blood vessels.
However, a combination of inhaled iloprost or intravenous milrinone with oral sildenafil may help reduce lung blood vessel resistance without affecting the overall blood pressure. Another possible strategy is using low-dose vasopressin. This can help increase resistance in the overall blood vessels (systemic vascular resistance) and decrease resistance in lung blood vessels by promoting the release of a gas called nitric oxide from the lung vessel lining cells (endothelium).
Preventing Pulmonary Idiopathic Hypertension
People who have idiopathic pulmonary hypertension, a kind of high blood pressure that affects the lungs, need various types of support. This includes help preventing infections, which can be achieved through regular vaccinations appropriate for their age. They may also benefit from supervised medical care or rehabilitative exercises, as well as emotional and social support.
Additionally, if the patient is a woman who might have children, she must receive advice on birth control methods. This is because becoming pregnant could worsen her health condition.
