HomeHealth articlespulmonary embolismWhat Are the Latest Diagnostic Tests for Pulmonary Embolism?

Understanding Pulmonary Embolism and Its Various Diagnostics

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New possibilities for diagnosing pulmonary embolism have emerged due to recent technical developments in CT scans, MRIs, etc. Continue reading to learn more.

Written by

Dr. Asna Fatma

Medically reviewed by

Dr. Varun Chaudhry

Published At May 26, 2023
Reviewed AtDecember 4, 2023

What Is Pulmonary Embolism?

First, it is important to learn what pulmonary embolism is to understand it. When an embolus (a particle that causes blockages) is lodged inside a blood vessel, it results in an embolism. This blockage-causing material can be a foreign body, a blood clot (thrombus), air bubbles, other gases, fat particles, amniotic fluid particles, etc. The blood flow in the affected blood vessel may become partially or completely blocked due to an embolism. When a blood clot or embolus is present in the lung’s arteries, it is known as a pulmonary embolism. The blood clot typically originates in a deep vein in the legs, and from there, it moves to the lung. The clot seldom develops in a vein in other areas of the body. Pulmonary embolism poses a life-threatening risk because one or more blood clots can cause blockage in the lungs.

What Causes Pulmonary Embolism?

When a piece of substance, most frequently a blood clot, lodges in a pulmonary artery and blocks blood flow, it causes a pulmonary embolism. Often this pulmonary embolism can occur due to multiple blood clots present in the blood vessels of the lungs. In addition, materials other than blood clots can sometimes obstruct blood vessels. Examples include:

  • Fat globules emerge from the fractured long bones.

  • Tumor parts.

  • Air bubbles.

  • Amniotic fluid fragments.

Anyone can get blood clots that can cause pulmonary embolisms; some factors can increase the chances of developing pulmonary embolism. These risk factors are as follows:

  • Family or personal history of blood clots and clotting disorders.

  • Certain medical conditions like heart diseases, certain types of cancers, clotting disorders, COVID-19 infection, etc.

  • Individuals who have been bedridden for a very long time.

  • Smoking.

  • Obesity.

  • Excessive alcohol consumption.

  • Estrogen replacement therapy or regular intake of birth control pills.

  • Pregnancy.

What Are the Symptoms of Pulmonary Embolism?

Depending on how much of the lung is affected, the magnitude of the blood clots, and whether the patient has underlying lung or heart problems, the symptoms of pulmonary embolism can vary greatly. The common sign and symptoms of pulmonary embolism are as follows:

  • Shortness of breath or dyspnea. The patient may experience difficulty breathing even while at rest.

  • Chest pain that may feel like a heart attack. When the patient takes a deep breath, the pain frequently gets severe.

  • Frequent fainting.

  • Cough.

  • The cough may contain blood or a streak of blood in the mucus.

  • Irregular heartbeats.

  • Feeling dizzy.

  • Excessive perspiration (sweating).

  • Fever or pyrexia.

  • Pain in the legs.

  • Swelling in the legs.

  • Bluish discoloration of the skin or cyanosis.

How Long Can Someone Have Pulmonary Embolism Without Knowing?

About 50 percent of people with pulmonary embolism do not have symptoms, so it may take months to diagnose the condition. Therefore, a person can have a pulmonary embolism for months and not know about it.

What Are the Latest Diagnostic Strategies for Pulmonary Embolism?

The diagnosis of pulmonary embolism continues to be a significant clinical issue. According to statistics, one to two cases of clinically suspected pulmonary embolism occurs annually per 1000 individuals. However, major advancements in these diagnostic tests have occurred in recent years, suggesting novel diagnostic approaches for pulmonary embolism and opening up new possibilities for diagnosis.

  • Clinical Assessment: Although the symptoms and signs of pulmonary embolism are vague, a few "classic" clinical markers point to the disease. Shock or syncope are symptoms of a large pulmonary embolism-induced circulatory collapse. Acute right heart failure symptoms, such as severe dyspnea (difficulty breathing) and chest discomfort, may also be present. Acute dyspnea that is frequently accompanied by tachycardia (increased heart rate) may be caused by an embolism.

  • D-Dimer: A protein fragment known as D-dimer is created when a blood clot dissolves within the body. Even though this is not specific, the disintegration of thrombi (blood clots) may result in higher plasma d-dimer levels. Since neoplasm, sepsis, and other conditions can also result in fibrinolysis, the sensitivity of all d-dimer testing for pulmonary embolism is low. There are numerous ways to assess plasma d-dimer levels. These methods include latex agglutination test (simple and fast but not very sensitive method), enzyme-linked immunosorbent assay or ELISA, etc.

  • Ultrasonography: Pulmonary embolism and DVT, or deep vein thrombosis, are both manifestations of venous thromboembolism. Therefore, it makes sense to check for deep vein thrombosis when diagnosing pulmonary embolism because it has been proposed that pulmonary embolism may have deep vein origin. Treatment for both conditions is the same; hence the discovery of deep vein thrombosis in a patient suspected of having pulmonary embolism invalidates further testing for pulmonary embolism and allows for the initiation of anticoagulant therapy. To find deep vein thrombosis, lower limb venous compression ultrasonography is frequently employed. A high megahertz linear transducer is used to check the femoral and popliteal veins while the patient is supine. The diagnosis is mainly based on the incompressibility of a venous segment. Ultrasonography has a low diagnostic sensitivity for distal deep vein thrombosis. Therefore, these diagnostic strategies should be repeated over a period of seven to fourteen days.

  • Lung Scintigraphy: An initial traditional chest radiograph is typically followed by a (V′/Q′) lung scintigram. The scintigram is performed with the help of technetium-99m. Anterior, posterior, left, and right posterior oblique, left, and right lateral, and other projections are obtained using a low-energy, big field-of-view gamma camera. Typical manifestations of pulmonary embolism are segmental, pleural-based perfusion abnormalities.

  • Pulmonary Angiography: Pulmonary angiography is the gold standard for diagnosing pulmonary embolism. Despite its high degree of accuracy, this test is not frequently utilized. During this procedure, a catheter is used, the femoral vein is punctured, and the catheter is moved up via the heart into the pulmonary trunk. The presence of emboli is checked. There are no definitive contraindications for pulmonary angiography. However, there are some relative contraindications like congestive heart failure, pulmonary hypertension, etc.

  • Spiral Computed Tomography: The first person to claim that pulmonary embolism could be clearly seen on standard computed tomography was Sinner in the year 1978. The ability to see an intravascular clot on a CT scan is the trait that allows for the most accurate diagnosis of pulmonary embolism. To make a certain diagnosis, only one embolus needs to be clearly seen.

  • Magnetic Resonance Imaging (MRI): Due to the unique composition of lung tissue, conventional magnetic resonance imaging (MRI) techniques cannot discriminate between segmental and subsegmental pulmonary blood vessels. However, it is now possible to examine the pulmonary arteries due to new and better techniques. Pulmonary vasculature has been studied using a variety of magnetic resonance angiography (MRA) methods. Despite the positive findings of this technology, it is still frequently difficult to tell thrombi from blood because of poor contrast resolution and signal-to-noise ratios. The differentiation is made simpler by adding contrast material, boosting the sensitivity and specificity of magnetic resonance angiography for pulmonary embolism.

Conclusion:

Pulmonary embolism is characterized by blocked blood vessels of the lungs due to blood clots, air bubbles, fat emboli, etc. Pulmonary embolisms have been difficult to diagnose for several reasons, including; patients being asymptomatic, presenting symptoms similar to other diseases, etc. However, doctors can determine the probability of pulmonary embolism based on the patient's clinical presentation, electrocardiogram, chest radiograph, and laboratory results.

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Dr. Varun Chaudhry

Radiodiagnosis

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