Pulmonary hypertension (PH) refers to high blood pressure in the blood vessels that travel between the heart and lungs. Pulmonary venous hypertension (PVH) and pulmonary arterial hypertension (PAH) are two distinct subsets of PH with different causes and treatments.
The World Health Organization (WHO) Classification of Pulmonary Hypertension recognizes five distinct groups of PH: PAH represents WHO group 1, and PVH makes up WHO group 2. Although PAH is designated as group 1, it is a rare disorder, with 500 to 1,000 new cases diagnosed each year. Conversely, WHO group 2 is the most commonly diagnosed classification of PH. Across subsets, PH has a higher prevalence in women than in men.
PVH (sometimes called postcapillary PH) is caused by diseases of the left side of the heart, such as left-sided heart failure or valve dysfunction. Alternately, PAH (sometimes called primary pulmonary hypertension or precapillary PH) is associated with right-sided heart diseases and has several origins.
Both PVH and PAH are characterized by increased blood pressure in the lungs. The differences in these conditions lie in what causes this increase in pressure.
PVH is caused by left heart disease — often left ventricular failure. Left ventricular failure occurs when there is a weakening or stiffening of the left side of the heart. The left side of the heart pumps oxygen-rich blood into the body’s circulatory system. When the left side of the heart is weak, the left ventricle has difficulty pumping, leading to reduced output. Likewise, when the left side of the heart is stiff, it can’t expand to allow enough blood to enter. In either case, this can cause blood to back up into the lung’s blood vessels, which increases blood pressure.
Valvular disease is another type of left-sided heart disease. Valves are small pieces of tissue in the heart that ensure that blood flows in the proper direction (from right to left). When the heart’s valves become narrow or leaky, blood can start flowing in the wrong direction, causing a backup of pressure in the lung’s blood vessels. An example of this is mitral valve disease, a condition where the valve between the upper left and lower left chambers of the heart (the left atrium and left ventricle, respectively) does not close properly.
On the other hand, PAH is caused by changes in the blood vessels connecting the right side of the heart to the lungs. The right side of the heart takes oxygen-low blood from the body and circulates it toward the lungs to pick up more oxygen. The changes in PAH include blood vessel narrowing, a process called vascular remodeling. This narrowing obstructs or reduces blood flow. In response to the decreased blood flow, the right side of the heart pumps harder, causing the muscle to thicken and enlarge (hypertrophy). Although hypertrophy may be helpful at first, it eventually impairs the heart’s ability to pump properly.
As mentioned above, PVH is a type of pulmonary hypertension that arises due to problems with the left side of the heart. PVH can be caused by problems with the left-sided heart’s muscles or valves. Regardless of the type of left-sided heart disease causing PVH, it is generally considered a singular condition.
Conversely, there are several types of PAH. In some cases, there is no identifiable cause. PAH can also be affected by other illnesses or by environmental or genetic factors.
Idiopathic PAH is high blood pressure in the arteries of the lungs without a clear cause.
Many chronic health conditions are associated with PAH. They include connective tissue diseases such as scleroderma, as well as congenital heart diseases. In addition, PAH can develop in people with HIV. Blood cancers like myeloproliferative disorders are known to cause PAH. Lupus, an inflammatory disorder, is also associated with PAH.
A person may develop PAH as the result of environmental triggers. This includes the use of drugs, particularly certain appetite-suppressant medications or amphetamines. PAH may also occur due to toxin exposure.
About 15 percent to 20 percent of people with PAH have heritable PAH, where an abnormal form of a gene that causes PAH is passed down between generations. Most commonly, heritable PAH is caused by mutations in the BMPR2 gene.
Other genes with a link to PAH have also been discovered. However, these are largely associated with spontaneous mutations (mutations that are not inherited from a relative) or are found in people who do not have a family history of PAH.
The symptoms of PVH and PAH are similar to those found in other types of PH but vary in presentation between people. Some people may not experience symptoms of PAH or PVH until their condition is advanced. The way a person with PVH or PAH experiences symptoms depends on co-occurring medical conditions, sex, age, and other factors.
Common early symptoms of PAH and PVH may include:
Later symptoms of PVH and PAH may also include:
Although PVH and PAH have different underlying causes, they have similar symptoms. In some cases, PVH can be mistaken for PAH. The diagnosis process involves first determining whether a person has PH, then determining the specific type of PH by identifying its underlying cause. It’s important to be able to differentiate between PAH and PVH because the two conditions have different treatments.
When diagnosing PH and determining the origin, doctors will look for heart and lung abnormalities. They’ll check for changes in blood flow within the lung’s blood vessels. They will ask whether there is a family history of pulmonary hypertension or other pulmonary blood vessel disease. There are many tests that help with this process.
The initial test for PH is often an echocardiogram. This noninvasive diagnostic test uses ultrasound waves to image the heart while it beats to look for any physical abnormalities, like thickening of the ventricles. Advancements in echocardiographic technology allow doctors to image the heart two-dimensionally and even three-dimensionally to measure its size and functions in real-time.
Other common tests a doctor may perform include:
The only definitive test for PAH is an invasive procedure called a right heart catheterization (RHC) test — sometimes called a pulmonary artery catheterization test. RHC measures the blood pressure in the lungs (called mean pulmonary arterial pressure), as well as how much blood the heart is pumping. A medication for PH called nitric oxide is sometimes administered during RHC to see if it will relax the lung’s blood vessels.
To perform RHC, a cardiologist guides a catheter (a thin tube) through a hole in the skin (usually in the neck, arm, or groin) up to the heart and pulmonary arteries to measure the blood pressure. A person with PAH will have a mean pulmonary arterial pressure higher than 25 mm Hg while at rest.
Other measurements commonly taken during RHC include:
These measurements shed light on a person’s total cardiovascular health and can help rule out PVH.
A doctor may perform a few different tests to confirm whether a person with PH has PVH. In addition to RHC to aid in the diagnosis, ECG can be used to identify if a person has an enlarged left ventricle.
Another person’s pulmonary capillary wedge pressure (PCWP) also can confirm if they have PVH. Taking this measurement involves an invasive procedure, traditionally done using a balloon-tipped catheter that’s guided through branches of the pulmonary arteries. The balloon is inflated to obstruct blood flow to create pressure, which is then measured. People with PVH will have a PCWP greater than 15 mm Hg.
PVH can be diagnosed noninvasively using Doppler echocardiography to measure how much blood is being pumped and to observe the way blood flows through the heart. Abnormalities in blood flow on the left side of the heart may indicate left ventricle failure or mitral valve stenosis.
The treatment plan for PVH or PAH will vary depending on the underlying cause of the condition. Notably, targeted treatments are available for PAH but not PVH. It’s important to have an accurate diagnosis, as treatments for PAH can harm someone with PVH, and vice versa.
Treatments for PAH focus on decreasing blood pressure in the lungs by opening the pulmonary arteries. Medications are the first line of treatment for PAH. Common medications include phosphodiesterase inhibitors (such as Sildenafil), which act as vasodilators to open up blood vessels, and endothelin receptor antagonists, which prevent blood vessels from constricting. Vasoconstricting medications could have a negative impact on people with PAH.
Some people with PAH do not respond to medication or have a severe form of the condition called chronic thromboembolic pulmonary hypertension (CTEPH). In CTEPH, small blood clots increase the pressure inside the pulmonary artery. Treatment options for people with CTEPH and severe PAH include surgeries to remove blockages or to expand the arteries using balloon catheters. In severe cases, a lung transplant may be required.
Treatments for PVH are based on addressing the reason for left heart disease. Addressing fluid retention is an important part of the treatment plan for PVH, and this is often treated with diuretics.
Other medications that can control blood pressure and prevent the worsening of left-sided heart disease are angiotensin-converting enzyme inhibitors, angiotensin II receptor blockers, and beta-blockers. These can help lower blood pressure and reduce the work of the heart. Pulmonary vasodilator medications, which are often prescribed for PAH, are not generally recommended for PVH, and more research regarding these therapies is needed.
People with PVH caused by valve stenosis or narrowing may benefit most from surgery to repair the valve.
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