What Is Pulmonary Vascular Disease?
Blood travels from the heart, to the lungs, and back to the heart. This process continually refills the blood with oxygen, and lets carbon dioxide be exhaled. Here's how the process works:
- Oxygen-poor blood returns from the body's tissues through the veins back to the right side of the heart.
- The right heart pumps oxygen-poor blood through the pulmonary arteries into the lungs. This blood becomes filled with oxygen.
- The oxygen-rich blood returns from the lungs back to the left side of the heart. The left heart pumps the oxygen-rich blood into the body through the aorta and many other arteries.
Any part of the heart-lung blood circuit can become damaged or blocked, leading to pulmonary vascular disease.
Causes of Pulmonary Vascular Disease
The causes of pulmonary vascular disease vary according to which of the lungs' blood vessels are affected. Pulmonary vascular disease is divided into several categories:
Pulmonary Arterial Hypertension: Increased blood pressure in the pulmonary arteries (carrying blood away from the heart to the lungs). Pulmonary arterial hypertension can be caused by lung disease, autoimmune disease, or heart failure. When there is no apparent cause, it's called idiopathic pulmonary arterial hypertension.
Pulmonary Venous Hypertension: Increased blood pressure in the pulmonary veins (carrying blood away from the lungs, to the heart). Pulmonary venous hypertension is most often caused by congestive heart failure. A damaged mitral valve in the heart (mitral stenosis or mitral regurgitation) may contribute to pulmonary venous hypertension.
Pulmonary Embolism: A blood clot breaks off from a deep vein (usually in the leg), travels into the right heart, and is pumped into the lungs. Rarely, the embolism can be a large bubble of air, or ball of fat, rather than a blood clot.
Chronic Thromboembolic Disease: In rare cases, a blood clot to the lungs (pulmonary embolism) is never reabsorbed by the body. Instead, a reaction occurs in which multiple small blood vessels in the lungs also develop blood clots. The process occurs slowly, and gradually affects a large part of the pulmonary arterial system.
Symptoms of Pulmonary Vascular Disease
The symptoms of pulmonary vascular disease vary according to several factors:
- The suddenness of the process affecting the pulmonary blood vessels
- Which pulmonary blood vessels are affected (where the pulmonary vascular disease is)
- How much of the pulmonary vascular system is affected
For example, a sudden, large pulmonary embolism blocking a large pulmonary artery can cause severe shortness of breath and chest pain. But a very small pulmonary embolism (blocking only a small blood vessel) may cause no noticeable symptoms.
Although symptoms of pulmonary vascular disease can vary widely, each of the causes of pulmonary vascular disease has a set of usual symptoms:
Pulmonary arterial hypertension: This most often causes slowly progressive shortness of breath. As the condition worsens, chest pain or fainting (syncope) with exertion can occur.
Pulmonary embolism: A blood clot to the lungs typically occurs suddenly. Shortness of breath, chest pain (often worse with deep breaths), and a rapid heart rate are common symptoms. Pulmonary embolism symptoms range from barely noticeable to severe, based on the size of the blood clot(s).
Pulmonary venous hypertension: This form of pulmonary vascular disease also causes shortness of breath, due to the congestive heart failure that's usually present. Shortness of breath may be worse while lying flat, when blood pressure is uncontrolled, or when extra fluid is present (edema).
Tests for Pulmonary Vascular Disease
Based on a person's symptoms, signs, and history, a doctor may begin to suspect the presence of pulmonary vascular disease. The diagnosis of pulmonary vascular disease is usually made using one or more of the following tests:
Computed tomography (CT scan): A CT scanner takes multiple X-rays, and a computer constructs detailed images of the lungs and chest. CT scanning can usually detect a pulmonary embolism in a pulmonary artery. CT scans can also uncover problems affecting the lungs themselves.
Ventilation/perfusion scan (V/Q scan): This nuclear medicine test takes images of how well the lungs fill with air. Those images are compared to pictures of how well blood flows through the pulmonary blood vessels. Unmatched areas may suggest a pulmonary embolism (blood clot) is present.
Echocardiography (echocardiogram): An ultrasound video of the beating heart. Congestive heart failure, heart valve disease, and other conditions contributing to pulmonary vascular disease can be discovered with echocardiogram.
Right heart catheterization: A pressure sensor is inserted through a needle into a vein in the neck or groin. A doctor advances the sensor through the veins, into the right heart, then into the pulmonary artery. Right heart catheterization is the best test to diagnose pulmonary arterial hypertension.
Chest X-ray film: A simple chest X-ray can't diagnose pulmonary vascular disease. However, it may identify contributing lung disease, or show enlarged pulmonary arteries that suggest pulmonary arterial hypertension.
Pulmonary angiography (angiogram): Contrast dye is injected into the blood, and X-ray images of the chest show detailed images of the pulmonary arterial system. Angiography is very good at diagnosing pulmonary embolism but is rarely performed anymore because CT scans are easier, less invasive, and have lower risk.
Treatments for Pulmonary Vascular Disease
There are many different treatments for pulmonary vascular disease. Pulmonary vascular disease is treated according to its cause.
Pulmonary embolism: Blood clots to the lungs are treated with blood thinners (anticoagulation). Treatments include the medicines are betrixaban (BEVYXXA), enoxaparin (Lovenox), heparin, and warfarin (Coumadin).
Chronic thromboembolic disease: Serious cases of thromboembolic disease may be treated with surgery to clear out the pulmonary arteries (thromboendarterectomy). Blood thinners are also used. Riociguat (Adempas) is a drug approved for use after surgery or in those who can't have surgery, to improve the ability to exercise.
Pulmonary arterial hypertension: Several medicines can lower blood pressure in the pulmonary arteries:
- ambrisentan (Letairis)
- bosentan (Tracleer)
- epoprostenol (Flolan)
- iloprost (Ventavis)
- macitentan (Opsumit)
- riociguat (Adempas)
- selexipag (Uptravi)
- sildenafil (Revatio)
- tadalafil (Adcirca)
- treprostenil (Orenitram, Remodulin, Tyvaso)
These drugs have been best shown to improve idiopathic pulmonary arterial hypertension.
Pulmonary venous hypertension: Because this form of pulmonary vascular disease is usually caused by congestive heart failure, these treatments for heart failure are usually appropriate:
- Diuretics, like furosemide (Lasix) and spironolactone (Aldactone)
- Angiotensin-converting enzyme (ACE) inhibitors, like lisinopril
- Beta-blockers, like carvedilol (Coreg) and metoprolol (Lopressor)
- Vasodilators that reduce blood pressure, like amlodipine (Norvasc), hydralazine (Apresoline) and isosorbide mononitrate (Imdur)
If pulmonary vascular disease is brought on by another condition, treating that condition might improve the pulmonary vascular disease:
- Autoimmune diseases (lupus, scleroderma, Sjogren's syndrome) are usually treated with drugs that suppress the immune system. Prednisone, azathioprine (Imuran), and cyclophosphamide (Cytoxan) are examples.
- In lung disease with low blood oxygen levels (chronic obstructive pulmonary disease, idiopathic pulmonary fibrosis, interstitial lung disease), providing inhaled oxygen can slow progression of pulmonary vascular disease. Two drugs, nintedanib (Ofev) and pirfenidone (Esbriet) are FDA-approved to treat idiopathic pulmonary fibrosis. They act on multiple pathways that may be involved in the scarring of lung tissue. Studies show both medications slow decline in patients when measured by breathing tests. Steroids to reduce inflammation and drugs to suppress the immune system may also be used.