Comprehensive Guide to Pulmonary Embolism: Insights into Causes, Symptoms, Diagnosis, and Advanced Treatment Options

Pulmonary embolism is a health condition where the tiny arteries of the lungs are obstructed by an embolus. An embolus is a particle that has traveled through the bloodstream from one part of the body to another, causing arterial blockage. These particles could be blood clots, fat, air, or amniotic fluid. Venous blood clots are the most frequent cause of pulmonary embolism. Roughly 90% of all pulmonary emboli are caused by lower extremity deep venous thrombosis. Venous clots from here have the potential to break off and travel as an embolus to the lungs, causing pulmonary embolism.

Pulmonary Embolism

Pulmonary Embolism Credit: Mikael Häggström, M.D.

The cardiovascular system is made up of the heart, arteries, veins, venules, and capillaries. The heart pumps blood, and the vessels transport the blood to other parts of the body. Blood clotting happens as a normal physiological process to prevent bleeding. Under normal circumstances, the clots are broken down appropriately. Sometimes the body may not be able to break it down, leading to life-threatening situations.

Worldwide, pulmonary embolism is the third leading cause of cardiovascular disease, following coronary artery disease and stroke. It occurs more in adults and older people over 75 years old. The incidence of pulmonary embolism has been on a steady rise over the past 20 years.

Causes

Blood clots in the body occur due to the slow movement of blood in the veins. Conditions that can predispose an individual to this include clotting disorders, cancer, sedentary lifestyle, pregnancy, reduced mobility, advanced age, disorders of the bone marrow causing thickened blood, indwelling venous catheters, bone injury (especially to the leg, hip, or pelvis), infections, the period after a major surgery up until 3 months, sickle cell disease, obesity, nephrotic syndrome, use of hormones like estrogen and testosterone, smoking, stroke, and a previous history of blood clots.

People with reduced mobility, like post-surgery patients, travelers, or patients with illnesses that don’t allow ambulation, are more predisposed to pulmonary embolism. Some infections, like COVID-19, that cause a systemic response could also lead to pulmonary embolism.

Symptoms

The physical manifestations of the disease appear abruptly and depend on the person’s clinical state and the extent of the blockage. People with coronary artery disease or chronic obstructive pulmonary disease (COPD) may have it worse.

Symptoms include breathing difficulty, chest pain, fainting, mental deterioration, cough containing blood-stained sputum, and fever.

Pulmonary infarction is the death of lung tissue due to a lack of blood supply. An embolus could block arteries, leading to this. This could present as severe chest pain, coughing up blood, or a fever. Usually, the symptoms last a couple of days but become milder as time passes.

Breathing difficulty may be the only manifestation when a pulmonary infarction has not occurred. Scrambling for air, restlessness, and anxiety are common features. Chest pain may be accompanied by irregular heartbeats and palpitations, i.e., being able to feel your heartbeat.

Unconsciousness occurs in people with very large emboli. Meanwhile, the blood pressure could drop so low, leading to shock and possible death. Mental deterioration is the first symptom that occurs in the elderly due to reduced blood and oxygen supply to the brain.

Recurring emboli

People with recurring emboli usually have progressive lung disease over months or years, leading to damage to the lung tissue. Arterial pressure in the lungs persistently increases, leading to a condition called chronic thromboembolism pulmonary hypertension (CTEPH). In addition to other symptoms, this can manifest as leg swelling and body weakness.

Diagnosis

The diagnosis of pulmonary embolism begins with a thorough history-taking and examination, followed by laboratory investigations.

A diagnosis of a large pulmonary embolism could be made based on obvious symptoms and a history of certain risk factors. However, the symptoms of smaller emboli are milder and could be confused with either a heart attack or asthma. Thus, it is quite difficult to make a diagnosis of pulmonary embolism.

Laboratory tests that could give a clue include a chest X-ray, electrocardiogram (ECG), oxygen saturation test, D-Dimer test, CT angiography, ultrasonography of the legs, lung ventilation-perfusion scan, and echocardiography.

Sometimes a chest X-ray may show abnormal parts of the pulmonary vessels. The results don’t reveal the embolism in its entirety; therefore, they are not a reliable means of diagnosis. An ECG may show abnormalities in heart activity, which could be a pointer towards pulmonary embolism.

The oxygen saturation test is one way of knowing if the lungs are not taking in enough oxygen. A point-of-care device called a pulse oximeter could be used, or blood could be taken and sent to the lab for arterial blood gas analysis.

A D-dimer test is used to analyze the blood level of a substance called D-dimer. If the level is elevated, there is a high chance that the person has pulmonary embolism, and vice versa. However, a high D-dimer level doesn’t always point towards pulmonary embolism. Additional investigation is needed to confirm the diagnosis because the D-dimer level can be elevated by other conditions, like infection or injury.

CT angiography of the pulmonary vessels is a fast imaging test done to detect and locate emboli. A contrast material is inserted into a vein, which makes its way to the pulmonary vessels, outlining the location and extent of the emboli. This test is often used to diagnose pulmonary embolism in most centers.

Ultrasonography of the legs is done to identify blood clots in the veins of the legs, which are typically the cause of pulmonary embolism. Even in the absence of venous clots, pulmonary embolism is still possible. Usually, when clots are discovered in the legs and are accompanied by mild breathing difficulty, treatment for pulmonary embolism is initiated immediately.

A pulmonary ventilation-perfusion scan measures the extent of breathing and the flow of blood in the vessels of the lungs. Abnormal results are a pointer towards pulmonary embolism.

Echocardiography is done to assess the state of the chambers of the heart. The result may show an enlarged heart, suggesting pulmonary embolism. This could be useful, especially for patients with recurrent emboli.

Also, blood tests could be done to assess the level of clotting factors. A deranged level is a pointer towards a clotting disorder and, subsequently, pulmonary embolism.

Treatment

Treatment of this condition involves treating the symptoms as well as the administration of anti-clotting medications and the surgical removal of clots.

Symptomatic treatment includes the administration of intranasal oxygen if oxygen saturation is low. Analgesics like nonsteroidal anti-inflammatory drugs (e.g., ibuprofen) could be given to aid in pain relief. If the patient is in circulatory shock, intravenous fluids like normal saline could be given. Assisted ventilation using machines may be needed if there is respiratory failure.

Anti-clotting medications like heparin, fondaparinux, warfarin, apixaban, and edoxaban prevent blood clots from forming in the vessels. The duration of administration of these drugs depends on whether the clot is caused by a reversible risk factor or a clotting disorder. A time frame of about 3 months is given for the former, and indefinite administration is instituted if it is a clotting disorder. Also, anti-clotting medications have been adapted as a measure to prevent the occurrence of pulmonary embolism in at-risk individuals.

Medications like alteplase that break down clots, also known as thrombolytics, can also be used. However, they are sparingly administered because they tend to cause heavy bleeding. An exception is during an emergency.

In life-threatening situations where recurrent emboli occur, surgery could be carried out to retrieve the emboli with the aid of a catheter. A filter could also be placed in the larger veins (e.g., inferior vena cava) to prevent the emboli from traveling to the heart.

Clinical trials

Recruitment is currently ongoing for a study called the Acute Pulmonary Extraction Trial. This involves the use of equipment called the AlphaVac multipurpose mechanical aspiration (MMA) F1885 system for the treatment of acute intermediate-risk pulmonary embolism. Enrollment began in 2022 and will end in 2024.

Clinical Opinion 

Having a life free of pulmonary embolism depends on how well the disease is prevented. Preventive measures include regular exercise and mobility, smoking cessation, plenty of fluid intake, avoidance of caffeine and alcohol, weight loss, the use of compression stockings, and the use of a vena cava filter (as earlier discussed, for people with recurrent emboli). A sedentary lifestyle is a major risk factor so make it a habit to frequently get away from your desk and take a walk.

Conclusion 

Pulmonary embolism is a frequent and possibly life-threatening cardiovascular condition that needs to be identified and treated right away. Treatment with drugs that improve blood flow and reduce clot formation has proven to be helpful.

References

Bull, T. M., & Hountras, P. (2023, October 13). Pulmonary Embolism (PE) MSD Manual, Consumer Version Retrieved November 13, 2023, from https://www.msdmanuals.com/home/lung-and-airway-disorders/pulmonary-embolism/pulmonary-embolism-pe

Clark, A. C., Xue, J., & Sharma, A. (2019, June 1). Pulmonary Embolism: Epidemiology, Patient Presentation, Diagnosis, and Treatment Journal of Radiology Nursing Retrieved November 13, 2023, from https://doi.org/10.1016/j.jradnu.2019.01.006

Professional, C. C. M. (n.d.). Pulmonary Embolism, Cleveland Clinic Retrieved November 13, 2023, from https://my.clevelandclinic.org/health/diseases/17400-pulmonary-embolism

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