What is Pulmonary Embolism?

Pulmonary embolism is a condition characterized by the mechanical obstruction of blood flow in the pulmonary artery due to an embolism (thrombus). This blockage is accompanied by a pronounced spasm in the branches of the pulmonary artery, leading to the development of an acute pulmonary heart, a reduction in cardiac output, bronchospasm, and decreased oxygenation of the blood.

Among all autopsies conducted annually in the United States, pulmonary embolism is detected in 4–15% of cases. Statistical data indicates that 3% of surgical procedures result in pulmonary embolism as a postoperative complication, with a fatal outcome in 5.5% of cases.

Patients diagnosed with pulmonary embolism require immediate hospitalization in the intensive care unit.

This condition is more commonly observed in individuals over the age of 40.

What Are the Main Causes of Pulmonary Embolism?

What leads to pulmonary embolism? In 90% of cases, the origin of the blood clots responsible for pulmonary embolism is located in the inferior vena cava system, specifically in the ileal-femoral segment, pelvic veins, prostate veins, and deep veins of the legs.

Risk Factors Include:

• Malignant neoplasms (commonly lung, stomach, and pancreatic cancer)
• Cardiovascular diseases (myocardial infarction, atrial fibrillation, mitral valve disease, myocarditis, infective endocarditis)
• Heart failure
• Stroke
• Sepsis
• Inflammatory bowel disease
• Erythremia
• Nephrotic syndrome
• Obesity
• Physical inactivity
• Estrogen therapy
• Primary hypercoagulation syndrome
• Antiphospholipid syndrome
• Deficiency of protein C and S
• Antithrombin III deficiency
• Pregnancy and the postpartum period
• Dysfibrinogenemia
• Epilepsy
• Traumatic injuries
• Postoperative period

Pathophysiology

Depending on the localization of the obstruction, pulmonary embolism is classified into the following types:

• Embolism of small branches of the pulmonary artery
• Blockage of the pulmonary artery’s lobar or segmental branches due to embolism
• Massive embolism, where the clot is located in the main trunk of the pulmonary artery or one of its major branches

Based on the proportion of blood vessels excluded from circulation, pulmonary embolism is categorized into four forms:

1. Fatal – When more than 75% of the pulmonary arterial blood flow is blocked, leading to rapid death.
2. Massive – When over 50% of the vessels are affected, causing tachycardia, hypotension, loss of consciousness, acute right ventricular failure, pulmonary hypertension, and cardiogenic shock.
3. Submaximal – Involving 30–50% of the pulmonary arteries, leading to moderate shortness of breath and mild signs of acute right ventricular failure, though blood pressure remains stable.
4. Small – When less than 25% of blood flow is obstructed, resulting in mild dyspnea without signs of right ventricular failure.

Acute massive pulmonary embolism can be fatal in an instant.

Clinical Forms

Pulmonary embolism can present in different clinical forms:

• Fulminant (Acute) Form – Occurs when both main branches or the trunk of the pulmonary artery are completely blocked. The patient suddenly experiences rapidly progressing acute respiratory failure, a sharp drop in blood pressure, and ventricular fibrillation, leading to death within minutes.
• Acute Form – Arises when the main branches, along with some segmental and lobar branches, are occluded. The onset is abrupt, with rapid progression of cardiac, respiratory, and cerebral insufficiency. It typically lasts 3–5 days and often results in pulmonary infarction.
• Protracted (Subacute) Form – Develops when medium and large branches of the pulmonary artery are blocked, leading to multiple lung infarctions. The condition lasts for several weeks, with gradually worsening right ventricular and respiratory failure. Recurrent thromboembolism is common and can be fatal.
• Recurrent (Chronic) Form – Characterized by repeated thrombosis of lobar and segmental branches, leading to recurrent pulmonary infarctions and pleurisy, usually bilateral. Over time, right ventricular failure and pulmonary hypertension increase. This form is frequently seen in postoperative patients and individuals with cardiovascular or oncological diseases.

Classification

With prompt and adequate treatment, the mortality rate from pulmonary embolism does not exceed 10%, whereas without treatment, it can reach 30%.

The severity of clinical manifestations depends on the following factors:

• The speed at which blood flow disturbances develop in the pulmonary artery system
• The size and number of thrombosed arterial vessels
• The extent of pulmonary blood supply impairment
• The patient’s initial health status and presence of underlying conditions

The clinical presentation of pulmonary embolism can vary widely, from being completely asymptomatic to causing sudden death. Its symptoms are not specific and may resemble other pulmonary or cardiovascular diseases. However, a sudden onset of symptoms with no other apparent cause (such as pneumonia, myocardial infarction, or heart failure) strongly suggests pulmonary embolism.

Symptoms of a Blood Clot in the Lungs (Pulmonary Embolism)

What Are the Warning Signs of Pulmonary Embolism? In the classical clinical presentation of pulmonary embolism, several syndromes can be identified:

1. Pulmonary and Pleural Syndrome
   • Shortness of breath due to impaired lung ventilation and perfusion
   • Cough, accompanied by hemoptysis in 20% of cases
   • Chest pain, often localized in the lower part of the chest
   • In massive embolism, pronounced cyanosis of the upper body, neck, and face
2. Cardiac Syndrome
   • Discomfort and pain behind the sternum
   • Tachycardia and arrhythmias
   • Severe hypotension, potentially leading to a collapse-like state
3. Abdominal Syndrome
   • Less common but may present as upper abdominal pain due to stretching of the liver capsule (Glisson’s capsule) in the context of right ventricular failure or irritation of the diaphragm
   • Additional symptoms include vomiting, belching, and intestinal paralysis
4. Cerebral Syndrome
   • More frequently observed in elderly individuals with severe cerebral atherosclerosis
   • Symptoms include loss of consciousness, seizures, hemiparesis, and psychomotor agitation
5. Renal Syndrome
   • In some cases, patients experience secretory anuria after emerging from shock
6. Feverish Syndrome
   • Fever due to inflammatory processes in the lungs and pleura
   • Fever duration ranges from 2 to 15 days
7. Immunological Syndrome
   • Arises during the second or third week of the disease
   • Characterized by the presence of circulating immune complexes in the blood, eosinophilia, recurrent pleurisy, pulmonitis, and a urticarial-like skin rash

According to statistics, 3% of surgical procedures result in pulmonary embolism as a postoperative complication, with a fatality rate of 5.5%.

Diagnostics of Pulmonary Embolism

How do you rule out a pulmonary embolism? If a pulmonary embolism is suspected, a laboratory-instrumental examination complex is prescribed, including:

• X-rays of the chest organs – signs of pulmonary embolism include atelectasis, fullness of the roots of the lungs, symptom of amputation (sudden break of the vessel’s passage), and the Westermark sign (local reduction of pulmonary vascularization).
• Ventilation-perfusion lung scintigraphy – signs of a high probability of pulmonary embolism include normal ventilation and a decrease in perfusion in one or several segments. However, the diagnostic value of the method decreases in patients with past pulmonary embolism episodes, lung tumors, and chronic obstructive pulmonary disease.
• Angiopulmonography – a classic method for diagnosing pulmonary embolism; diagnostic criteria include detecting the thrombus contour and the sudden break of a branch of the pulmonary artery.
• Electrocardiography (ECG) – helps identify indirect signs of pulmonary embolism and rule out myocardial infarction.

Differential diagnosis is performed to distinguish pulmonary embolism from nonthrombotic embolism of the pulmonary artery (tumor, septic, fatty, or amniotic), psychogenic hyperventilation, rib fracture, pneumonia, bronchial asthma, pneumothorax, pericarditis, heart failure, and myocardial infarction.

Pulmonary Embolism Treatment

Patients with pulmonary embolism require urgent hospitalization in the intensive care unit. Drug treatment in the first stage consists of administering heparin, indirect anticoagulants, and fibrinolytic agents.

In cases of severe hypotension, infusion therapy is performed, and medications such as dopamine, dobutamine, and epinephrine hydrochloride are used. In recurrent cases of pulmonary embolism, with a prolonged or lifelong course, indirect anticoagulants, acetylsalicylic acid (Aspirin), or a cava filter (to prevent clots from entering the inferior vena cava) may be recommended.

The development of infarction pneumonia is an indication for the administration of broad-spectrum antibiotics.

In cases of massive pulmonary embolism and the ineffectiveness of conservative therapy, surgical intervention is performed in one of two ways:

• Closed embolectomy with an aspiration catheter.
• Open embolectomy in cardiopulmonary bypass.

Surgical treatment of pulmonary embolism carries a high risk of complications and deat

Possible Consequences and Complications of Pulmonary Embolism

Acute massive pulmonary embolism can cause sudden death. In cases where compensatory mechanisms have time to work, the patient does not die immediately but rapidly develops secondary hemodynamic disorders, which, in the absence of timely treatment, can be fatal. Possible complications of pulmonary embolism include:

• Acute pulmonary heart
• Pneumonia
• Pleurisy
• Lung abscess
• Gangrene of the lung

What Is the Survival Rate of Pulmonary Embolism?

With timely and adequate treatment of pulmonary embolism, the mortality rate does not exceed 10%; without treatment, it reaches 30%. The prognosis is worse in individuals with pre-existing heart or lung diseases.

Approximately 1% of patients who have had a pulmonary embolism develop chronic pulmonary hypertension in the long term.

Of all the autopsies conducted annually in Russia, pulmonary embolism is found in 4–15% of cases.

How to Prevent Blood Clots in the Lungs?

To prevent pulmonary embolism, preoperative preparation for patients with risk factors includes:

• Pneumatic compression
• Wearing compression garments (elastic stockings)
• Administration of small doses of heparin

In the postoperative period, small doses of heparin are injected subcutaneously, and indirect anticoagulants are prescribed.

For recurrent pulmonary embolism, indirect anticoagulants may be prescribed for life, and a decision may be made regarding the installation of a cava filter.

Sources and materials:

1. https://en.wikipedia.org/wiki/Pulmonary_embolism
2. https://medlineplus.gov/pulmonaryembolism.html
3. https://www.pennmedicine.org/for-patients-and-visitors/patient-information/conditions-treated-a-to-z/pulmonary-embolus
4. https://www.mayoclinic.org/diseases-conditions/pulmonary-embolism/symptoms-causes/syc-20354647
5. https://www.hopkinsmedicine.org/health/conditions-and-diseases/pulmonary-embolism
6. https://my.clevelandclinic.org/health/diseases/17400-pulmonary-embolism
7. https://www.msdmanuals.com/home/quick-facts-lung-and-airway-disorders/pulmonary-embolism-pe/pulmonary-embolism-pe
8. https://www.nhs.uk/conditions/pulmonary-embolism/