Embolism: Definition, Symptoms, Causes

Brief overview

• What is an embolism? Complete or partial blockage of a blood vessel by the body’s own or foreign material (e.g. blood clot) that enters the bloodstream.
• Symptoms: Different symptoms occur depending on which blood vessel is affected. Sudden pain often occurs, but sometimes those affected are symptom-free.
• Causes: An embolism (thromboembolism) is often caused by a blood clot (thrombus) that detaches from the vessel wall and enters the bloodstream.
• Treatment: The doctor usually treats an embolism with medication, in some cases also surgically. The aim of the treatment is to dissolve or remove the embolus.
• Prevention: Exercise regularly, drink enough, avoid being overweight, stop smoking; if necessary, thrombosis prophylaxis e.g. after operations (anticoagulant medication, compression stockings)
• Diagnosis: consultation with the doctor, physical examination (including ultrasound, CT, MRI, angiography)

The term embolism comes from the Greek (“embolla”) and means “to throw in”. In an embolism, a clot (“embolus” = vascular clot, plural “emboli”), which is washed in with the blood, blocks a blood vessel. It prevents the blood from flowing freely through the vessel.

As a result, the affected area is no longer supplied with sufficient oxygen and important nutrients. Over time, the tissue there dies, sometimes leading to life-threatening consequences such as a heart attack or stroke. In Germany, 20,000 to 25,000 people die from an embolism every year.

An embolus only causes an embolism if its diameter is larger than that of the blood vessel.

What types of embolism are there?

An embolism occurs in both the veins and the arteries. Emboli also form in both blood vessels. Doctors therefore differentiate between arterial and venous embolisms.

Arterial embolism

Arterial embolisms affect

• about 60 percent the brain
• about 28 percent the legs
• about 6 percent the arms
• about 6 percent of the organs (e.g. intestines, kidneys, spleen)

Venous embolism

In a venous embolism, the vascular clot forms in the veins – preferably in the legs or pelvis. It reaches the lungs via the right ventricle and the pulmonary artery, where it often causes a pulmonary embolism.

Paradoxical embolism

Paradoxical embolism – also known as crossed embolism – is a special form of embolism. The embolus forms in a vein and blocks an artery (but not the pulmonary arteries!). This is only possible if the embolus enters the left ventricle through gaps or small openings in the cardiac septum (e.g. due to a congenital heart defect). This means that the embolus does not enter the lungs as in a conventional venous embolism, but instead enters the arterial system of the blood circulation.

How does an embolism differ from a thrombosis?

The thrombus detaches from the inner wall of the vessel where it has formed and travels through the body via the bloodstream. If this clot (“embolus”) then blocks a vessel elsewhere in the body, doctors speak of an embolism (or thromboembolism).

What are the signs of an embolism?

Embolisms cause very different symptoms depending on where they occur in the body. While some are not noticeable at all, others lead to numerous symptoms and signs. Generally, people with an embolism experience severe pain that occurs suddenly. The embolus disrupts the blood supply, which means that the affected organ no longer functions properly. In some cases, the tissue at the affected site even dies.

Embolism in legs or arms

If an embolism occurs in a large artery in the leg or arm, the symptoms are usually very typical. They can be characterized by the “6P” (according to Pratt; six physical signs):

• Pain
• Paleness
• Paresthesia (numbness)
• Pulselessness (loss of pulse)
• Paralysis (paralysis)
• Prostation (shock)

In severe cases, an embolism in the arm or leg results in those affected no longer being able to move their arm or leg.

Embolism in the lung

A pulmonary embolism is characterized by pain in the lungs, sudden shortness of breath (dyspnoea), accelerated breathing (tachypnoea), palpitations (tachycardia), a feeling of oppression, an acute drop in blood pressure (hypotension) and circulatory shock. If large enough, an embolus in the lungs overloads the heart and leads to death.

Embolism in the brain

Embolism in the heart

In rare cases, an embolus blocks the coronary arteries and triggers a heart attack in those affected. In some severe cases, an embolism in the heart leads to heart failure.

Embolism in the internal organs

An embolism in the internal organs triggers various symptoms depending on the organ affected:

Kidneys

If the kidneys are affected by an embolism, this often leads to a kidney infarction. Those affected usually experience severe pain in the lumbar region and blood in the urine (hematuria). In extreme cases, kidney function may fail completely (kidney failure).

Spleen

Intestine

In the intestinal mesentery – the band of connective tissue that attaches the intestine to the abdomen and in which the blood vessels and nerves to the intestine run (known as the mesentery) – an embolism causes severe abdominal pain in those affected. They also often have bloody diarrhea and fever. Intestinal movements are also often reduced or stop altogether. In extreme cases, the affected section of bowel dies.

The larger the area that is cut off from the blood supply by the embolism, the more severe the symptoms usually are.

What causes an embolism?

There are various causes of an embolism. The embolus that blocks the vessel and thus triggers an embolism usually consists of the body’s own substances such as drops of fat, amniotic fluid, blood clots (thrombi) or air bubbles. In some cases, it also consists of foreign materials such as foreign bodies (e.g. parts of a hollow needle) or parasites (e.g. tapeworms).

Emboli can therefore be divided into

• Liquid emboli, e.g. consisting of drops of fat or amniotic fluid.
• Gaseous emboli, e.g. consisting of air bubbles.

Depending on the cause, the following emboli can be distinguished:

Thromboembolism

The most common form of embolism is thromboembolism. It is caused by a blood clot (thrombus) that detaches from the vessel wall and enters the bloodstream. This embolus then travels with the bloodstream through the body until it gets stuck at some point and blocks a vessel. This results in a thromboembolism.

Doctors differentiate between venous and arterial thromboembolism.

Venous thromboembolism (VTE)

The risk of venous thromboembolism is increased if someone is bedridden (e.g. people in need of care), after an operation (e.g. if you lie down a lot afterwards) or if those affected have an inflammation of the veins (thrombophlebitis).

Arterial thromboembolism (ATE)

In an arterial thromboembolism, the embolus originates from an artery. It usually originates in the left side of the heart. If the embolus becomes detached, it often reaches the brain (cerebral embolism) and triggers a stroke.

Heart disease is the most common cause of arterial thromboembolism, accounting for up to 90 percent of cases. These include, for example

• Arteriosclerosis (“hardening of the arteries”); the blood vessels narrow due to deposits of blood components (e.g. cholesterol, white blood cells)
• Injury or scarring of the inner lining of the vessel (endothelium)
• Coagulation disorders (thrombophilia)
• Inflammation of the inner lining of the heart (endocarditis)
• Dilation of the heart wall (aneurysm)

The most common embolisms are thromboembolisms that occur after a thrombosis of the deep leg veins (pulmonary embolism) and thromboembolisms in the arteries of the brain (stroke).

Tumor embolism

A tumor embolism is caused by spread cancer cells (tumor cells) or spread cancer tissue. The embolus (or so-called metastatic embolus) can cause metastases to form in other areas of the body.

Tumor embolisms often occur in people with advanced cancer. The reason for this is that cancer increases the blood’s ability to clot. This means that the blood clots faster. The more aggressive the cancer growth, the higher the risk of thrombosis and, subsequently, embolism.

Fat embolism

Bone marrow embolism

In some cases of bone fractures, bone marrow tissue enters the vascular system and triggers an embolism. This type of embolism therefore often occurs in fractures of long bones in which bone marrow is located. These include, for example, the upper arm bone (humerus), the forearm bones ulna (ulna) and radius (radius) as well as the thigh bone (femur).

Bacterial embolism (septic embolism)

In a bacterial embolism, bacteria enter the bloodstream and trigger an embolism. This occurs, for example, as a result of blood poisoning (sepsis) or inflammation of the inner lining of the heart (endocarditis). A septic embolus may lead to a purulent infection of the affected tissue.

In contrast to a septic embolus, a so-called bare embolus is not bacterially infected.

Gas embolism

A so-called decompression accident (decompression sickness) can also lead to a life-threatening gas embolism. Gas bubbles form in the blood vessels if the external pressure drops too quickly. This can happen, for example, if you emerge from the water too quickly (diver’s disease) or if you ascend too quickly.

Amniotic fluid embolism

If amniotic fluid enters the mother’s bloodstream via the uterus during birth, this can lead to amniotic fluid embolism (also known as “obstetric shock syndrome”). This is a rare but life-threatening birth complication that often leads to brain damage in mothers and children. The exact cause of an amniotic fluid embolism is not yet clear.

Parasite embolism

Foreign body embolism

In a foreign body embolism, foreign bodies enter the bloodstream. This is the case, for example, if parts of examination tools such as catheters (tubes that are inserted into organs) or cannulas (hollow needles) break off during an examination and enter the bloodstream. Other foreign bodies include shrapnel or shotgun pellets.

What are the risk factors for an embolism?

There are several factors that increase the risk of an embolism. One of the most important risk factors for thromboembolism, for example, is heart disease – in particular atrial fibrillation, in which blood clots form in the atria of the heart. Other risk factors are

• Smoking
• High-fat diet
• Little physical activity
• Vascular and heart disease, e.g. arteriosclerosis, heart failure
• Diabetes (diabetes mellitus)
• High blood pressure (hypertension)
• Pathological overweight (obesity)
• Cancer
• operations
• Increasing age
• Too little movement of the legs (due to bedriddenness, paralysis, rigid bandages or long journeys, especially air travel)
• Pregnancy and postpartum
• Serious injuries
• Previously suffered embolisms
• Venous diseases, e.g. phlebitis, varicose veins (varices)
• Female gender (women are more frequently affected than men)

The same risk factors apply to embolisms as to thrombosis.

What can be done to prevent an embolism?

The aim of treating an embolism is to ensure that sufficient blood flows through the blocked vessel again. To do this, doctors administer anticoagulant medication. In severe cases, the blood clot is dissolved with medication (medicinal thrombolysis) or surgically removed (embolectomy).

Medication

In severe cases, the blood clot is dissolved with medication. To do this, doctors administer so-called fibrinolytics (medicinal thrombolysis).

To prevent a new thromboembolism, the patient is then given anticoagulant medication in tablet form for several months (e.g. so-called DOACs or vitamin K antagonists such as phenprocoumon). This is called oral anticoagulation, which roughly translates as “blood clotting inhibition through medication”. The anticoagulant drugs are effective, but carry a certain risk of bleeding. Some patients therefore receive acetylsalicylic acid (e.g. ASA 100 mg) as long-term therapy to prevent blood clots and at the same time minimize the risk of bleeding.

Removal of the embolus using a catheter

Operation (embolectomy)

The last option for removing the blood clot is a surgical embolectomy. Doctors remove the embolus in an open operation. In the case of a pulmonary embolism, the patient is placed under general anesthesia and connected to a heart-lung machine.

How can an embolism be prevented?

If you want to prevent an embolism, it is important that you keep the risk as low as possible by taking the following measures:

Lifestyle changes

• If you are a smoker, stop smoking.
• Avoid being overweight and eat a balanced diet.
• Drink enough fluids (at least one and a half to two liters per day)
• Make sure you get regular exercise on long flights or car journeys.
• Have regular check-ups with your GP to detect and treat illnesses such as high blood pressure or diabetes mellitus at an early stage.

Preventing thrombosis

Because every injury activates blood clotting, operations also increase the risk of thrombosis or embolism. In pregnant women, childbirth also increases the risk of thrombosis or embolism. For this reason, doctors often prescribe heparin injections after an operation or birth, which those affected usually inject themselves under the skin once a day. Heparin inhibits blood clotting and thus prevents thromboses and embolisms.

To prevent an embolism, the doctor also often prescribes compression stockings (“thrombosis stockings”). As a rule, patients put these stockings on in the morning after getting up and take them off again in the evening before going to bed. They can also be worn continuously. Compression stockings support better blood flow in the leg and thus prevent thrombosis.

The duration of this thrombosis prophylaxis depends on the individual risk.

How does the doctor diagnose an embolism?

The first point of contact if an embolism is suspected is the family doctor. If they suspect that the symptoms are due to an embolism, they will usually refer the patient to hospital. There, a specialist in internal medicine (internist) with a specialization in vascular diseases (angiologist or phlebologist) will treat the patient further.

An embolism is often life-threatening. It is therefore important that the doctor clarifies symptoms that indicate an embolism immediately and acts accordingly.

Consultation with the doctor and physical examination

Blood test

The diagnosis of an embolism also includes a blood test. Certain blood values confirm the suspicion of an embolism. These include the so-called D-dimers. D-dimers are proteins that are produced when a blood clot breaks down. If they are elevated, this is an indication that a blood clot, i.e. a thrombosis or embolism, is being broken down somewhere in the body.

Ultrasound, CT, MRI

If the examination confirms the suspicion of an embolism, the doctor will carry out an imaging examination, e.g. using ultrasound (sonography), computer tomography (CT) or magnetic resonance imaging (MRI).

Angiography

The doctor uses computed tomography or magnetic resonance imaging to produce images of the blood vessels and vascular system (CT angiography or MRI angiography). To do this, the doctor injects contrast medium (iodine-containing, water-clear and colorless liquid that is visible in the X-ray image) into the blood vessel and then performs the computer tomography or magnetic resonance imaging. The interior of the vessel is then visible in the CT or MRI image. In this way, the doctor can see whether an embolus is blocking a vessel or whether the arterial wall is altered (e.g. narrowed) due to other causes such as arteriosclerosis (hardening of the arteries).

Scintigraphy

The doctor then examines the pulmonary blood flow. To do this, he injects weakly radioactive protein particles into one of the patient’s veins. These enter the lungs with the bloodstream, where they remain trapped in some of the finest blood vessels. Using a special camera (gamma camera, SPECT), the doctor makes these visible and produces images. He can then see where the blood flow is reduced by the blood clot.