Paradoxical embolism

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Paradoxical embolism
Other namesCrossed embolism
Specialty Cardiology   OOjs UI icon edit-ltr-progressive.svg

An embolus , is described as a free-floating mass, located inside blood vessels that can travel from one site in the blood stream to another. An embolus can be made up of solid (like a blood clot), liquid (like amniotic fluid), or gas (like air). Once these masses get "stuck" in a different blood vessel, it is then known as an "embolism." An embolism can cause ischemia—damage to an organ from lack of oxygen. [1] A paradoxical embolism is a specific type of embolism in which the embolus travels from the right side of the heart (venous circulation) to the left side of the heart (arterial circulation) and lodges itself in a blood vessel known as an artery. [2] It is termed "paradoxical" because venous emboli will usually be lodged in pulmonary artery in an event called pulmonary embolism, instead of systemic circulation.

Contents

Pathophysiology

An embolism may be made from any one of numerous materials that may find itself in a blood vessel, including a piece of a thrombus, known as a thromboembolism, air from an intravenous catheter, fat globules from bone marrow, amniotic fluid during birth. [1] In order for an embolus to become a paradoxical embolus it must traverse from venous circulation, in the veins, to arterial circulation, in the arteries. There are many routes in which an embolism can traverse from the right (venous) side of the heart to the left (arterial) side of the heart. These routes include moving through a patent foramen ovale (a congenital hole connecting the right and left atria of the heart), a ventricular septal defect (a congenital hole connecting the ventricles), or a pulmonary arteriovenous fistula, where arteries in the lungs connect directly to veins without capillaries in between. [2] [3] Although there are many routes an embolism may take to enter the arterial circulation, the term paradoxical embolism most commonly refers to a clot passing through a patent foramen ovale. The formen ovale is open during development of the heart in a developing fetus, and normally closes soon after birth - studies have found that patent foramen ovale is present in a significant portion of the population into adulthood. [4]

Once an embolus enters arterial circulation it continually travels down arteries to smaller vessels before lodging itself in vessels and stopping blood flow to the tissues supplied by those blood vessels. Often, the embolus will reach the brain and cause permanent stoppage of blood flow to a region of the brain, a feared complication of paradoxical embolism. This stoppage of blood flow in the brain, or ischemia, is called a cerebral infarct, also known as a stroke. [5]

Epidemiology

Although aging data has suggested paradoxical emboli may cause up to 47,000 strokes per year, [6] it is difficult to measure the actual rates of paradoxical emboli because it remains challenging to definitively diagnose the disease. Because many strokes have no known cause, an individual who has an embolic event, often a stroke, and is found to have patent foramen ovale or right-to-left shunt, the speculative diagnosis of paradoxical embolism is given to the patient. [7] Although no conclusive evidence has reported a true prevalence of the disease, data suggests that the presence of patent foramen ovales and other inter-cardiac shunts are associated with large increase in the prevalence of strokes of unknown etiology, suggesting paradoxical embolism may be the cause. [7] Regardless of true disease prevalence, the difficulties surrounding diagnosis may lead it to be an under-recognized etiology of strokes.

Clinical Manifestations

Symptoms experienced by an individual with a paradoxical embolism can be from both the original site of thrombus and the location of where the emboli lodges. It is believed that the most common origin site of thrombus is from a deep vein thrombosis (DVT), however, in most patients with suspected paradoxical embolism no evidence of a DVT is found. [8] Symptoms of a DVT will include unilateral leg swelling and pain, warmth, and redness of the affected area. [9] This is due to the blockage of blood attempting to return to the heart through the venous system.

Additional findings in a patient with a paradoxical embolism will be dependent upon where the emboli lodges and disrupts blood flow. Three important clinical manifestations that may be caused by paradoxical embolism include a stroke, migraine, and acute myocardial infarction, also known as a heart attack. [7] A stroke and migraine in the setting of a paradoxical embolism are caused by the emboli disrupting blood flow in a cerebral artery. A myocardial infarction in the setting of a paradoxical embolism are caused by the emboli disrupting blood flow in a coronary artery. Physical findings that should be evaluated include a comprehensive neurological examination for evaluation of stroke symptoms such as weakness, gait changes, slurred speech, and facial droop. [10]

Additionally, if a paradoxical embolism is suspected in a patient, findings consistent with a congenital heart defect that may lead to right-to-left shunting can be evaluated. These include digital clubbing due to chronic hypoxemia in distal extremities or a widely-split S2, a pathological heartbeat pattern where the second heart sound has two components. [11]

Evaluation and Diagnosis

Resources suggest a paradoxical embolism should be expected when three findings are present simultaneously; a deep vein thrombosis (a thrombus occurring in a large vein, usually of the leg), a passageway or right-to-left shunt that allows an emboli across the heart, and evidence of arterial emboli. [10] Once suspicion is raised for a paradoxical embolism, a battery of tests may be ordered for the patient and a discussion regarding past medical history and family history is useful for identifying contributing risk factors.

History

It is essential to discuss if the patient has personal or family history of a patent foramen ovale or other congenital heart disease that may have allowed an embolus into arterial circulation. Additionally patients may be asked about a history of deep vein thrombosis or factors that contribute to DVT, including high blood pressure, high cholesterol, prior heart attacks, or diabetes. Use of substance that make blood clots more likely such as tobacco or estrogen may also be discussed. [11]

Laboratory Studies and other Diagnostic Tests

Specific blood tests known as coagulation studies may be ordered. These tests measure how quickly a blood clot can form and may include PT, PTT, INR, and Protein C and S levels. A complete blood count (CBC) can also be ordered to test for low platelets. [10] An EKG may be started to evaluate for abnormal heart rhythms, especially atrial fibrillation which often cause traditional emboli to form in the heart. Arterial blood gas measurements and metabolic panels may also be drawn for the purpose of supportive measures. [11]

Imaging

Imaging can be done for various reasons during a suspected paradoxical embolism including scanning for a DVT that may have caused the emboli, evaluating the brain for ischemic changes secondary to embolism, and to evaluate for heart defect that could cause an emboli to enter systemic circulation.

Ultrasound, MRI imaging, or CT scans of the lower extremities help to identify a possible DVT, which provides evidence that an emboli may have come from venous circulation. [10] Although these imaging modalities are used to evaluate for venous thromboembolism, their use in detecting heart defects is limited. The use of MRI to detect cardiac shunts is "controversial" and that the use of CT is not recommended due to exposure to ionizing radiation and lack of functional imaging. [7]

It is reported that transesophageal echocardiography or TEE, is the best non-invasive option for diagnosing intracardiac shunts like a patent foramen ovale. Additionally, there is a need for a color flow Doppler study or the injection of agitated saline/contrast medium followed by a Valsalva maneuver to visualize flow of blood from the lower pressure venous system to the higher pressure arterial system. [7]

Similar to a TEE, a transcranial Doppler sonography study is also described as helping to evaluate for right-to-left shunts of the heart. However, it can also be used to detect other forms of right-to-left shunts including pulmonary arteriovenous malformations because it too needs agitated saline/contrast injected, but rather than imaging the heart, observes if any microemboli appear in the middle cerebral artery, an artery or the brain, following a valsalva maneuver. [7]

Ear oximetry is also described as a fairly accurate screening tool for a shunt. It measures the oxygen saturation of blood as it passes through the ear. Following a valsalva maneuver, pressure increases in the right heart, deoxygenated blood is shunted into arterial circulation, and a decrease in oxygen saturation can then be measured in the capillaries of the ear. [7]

Treatment

Current recommendation suggest that the two major goals of treatment include medical management of the thrombotic event to help prevent further thrombus/embolus formation and closure of the patent foramen ovale or other route that let to a pardoxical embolism. [11]

A paradoxical emboli should be medically managed similar to any other thromboembolism with medical anticoagulation. This is to prevent new or worsening blood clot formation that may occlude vessels and cause organ ischemia. [2] Some sources suggest anticoagulation with heparin be performed, while others give a list of reasonable drug options including anticoagulants like heparin and warfarin, anti-platelet therapy like aspirin and clopidogrel, and thrombolytic therapy like alteplase and streptokinase. [11] [2] If an embolus is causing life or limb-threatening ischemia, is located in a reasonable location, and is first visualized with fluoroscopy, catheter embolectomy can be performed to retrieve the clot as well. [2]

Surgical closure of a patent foramen ovale or other atrial septal defects is often done through an out-patient, percutaneous, surgery that has few complications. [7] Although closure of a patent foramen ovale or atrial septal defect theoretically removes the pathway for an arterial embolus to enter venous circulation and cause a paradoxical embolism, data suggests that closing intracardiac shunts is no more effective than medical management alone in preventing strokes. [2]

Related Research Articles

<span class="mw-page-title-main">Vein</span> Blood vessels that carry blood towards the heart

Veins are blood vessels in the circulatory system of humans and most other animals that carry blood towards the heart. Most veins carry deoxygenated blood from the tissues back to the heart; exceptions are those of the pulmonary and fetal circulations which carry oxygenated blood to the heart. In the systemic circulation, arteries carry oxygenated blood away from the heart, and veins return deoxygenated blood to the heart, in the deep veins.

<span class="mw-page-title-main">Embolism</span> Blockage of a blood vessel by a circulatory mass (embolus)

An embolism is the lodging of an embolus, a blockage-causing piece of material, inside a blood vessel. The embolus may be a blood clot (thrombus), a fat globule, a bubble of air or other gas, amniotic fluid, or foreign material.

<span class="mw-page-title-main">Thrombosis</span> Formation of blood clots inside the blood vessels

Thrombosis is the formation of a blood clot inside a blood vessel, obstructing the flow of blood through the circulatory system. When a blood vessel is injured, the body uses platelets (thrombocytes) and fibrin to form a blood clot to prevent blood loss. Even when a blood vessel is not injured, blood clots may form in the body under certain conditions. A clot, or a piece of the clot, that breaks free and begins to travel around the body is known as an embolus.

<span class="mw-page-title-main">Embolus</span> Unattached mass that travels through the bloodstream

An embolus is an unattached mass that travels through the bloodstream and is capable of creating blockages. When an embolus occludes a blood vessel, it is called an embolism or embolic event. There are a number of different types of emboli, including blood clots, cholesterol plaque or crystals, fat globules, gas bubbles, and foreign bodies, which can result in different types of embolisms.

<span class="mw-page-title-main">Thrombus</span> Blood clot

A thrombus, colloquially called a blood clot, is the final product of the blood coagulation step in hemostasis. There are two components to a thrombus: aggregated platelets and red blood cells that form a plug, and a mesh of cross-linked fibrin protein. The substance making up a thrombus is sometimes called cruor. A thrombus is a healthy response to injury intended to stop and prevent further bleeding, but can be harmful in thrombosis, when a clot obstructs blood flow through a healthy blood vessel in the circulatory system.

<span class="mw-page-title-main">Venous thrombosis</span> Blood clot (thrombus) that forms within a vein

Venous thrombosis is the blockage of a vein caused by a thrombus. A common form of venous thrombosis is deep vein thrombosis (DVT), when a blood clot forms in the deep veins. If a thrombus breaks off (embolizes) and flows to the lungs to lodge there, it becomes a pulmonary embolism (PE), a blood clot in the lungs. The conditions of DVT only, DVT with PE, and PE only, are all captured by the term venous thromboembolism (VTE).

<span class="mw-page-title-main">Air embolism</span> Vascular blockage by air bubbles

An air embolism, also known as a gas embolism, is a blood vessel blockage caused by one or more bubbles of air or other gas in the circulatory system. Air can be introduced into the circulation during surgical procedures, lung over-expansion injury, decompression, and a few other causes. In flora, air embolisms may also occur in the xylem of vascular plants, especially when suffering from water stress.

<span class="mw-page-title-main">Ischemia</span> Restriction in blood supply to tissues

Ischemia or ischaemia is a restriction in blood supply to any tissue, muscle group, or organ of the body, causing a shortage of oxygen that is needed for cellular metabolism. Ischemia is generally caused by problems with blood vessels, with resultant damage to or dysfunction of tissue i.e. hypoxia and microvascular dysfunction. It also implies local hypoxia in a part of a body resulting from constriction.

<span class="mw-page-title-main">Deep vein thrombosis</span> Formation of a blood clot (thrombus) in a deep vein

Deep vein thrombosis (DVT) is a type of venous thrombosis involving the formation of a blood clot in a deep vein, most commonly in the legs or pelvis. A minority of DVTs occur in the arms. Symptoms can include pain, swelling, redness, and enlarged veins in the affected area, but some DVTs have no symptoms.

dextro-Transposition of the great arteries Medical condition

dextro-Transposition of the great arteries is a potentially life-threatening birth defect in the large arteries of the heart. The primary arteries are transposed.

<span class="mw-page-title-main">Atrial septal defect</span> Human heart defect present at birth

Atrial septal defect (ASD) is a congenital heart defect in which blood flows between the atria of the heart. Some flow is a normal condition both pre-birth and immediately post-birth via the foramen ovale; however, when this does not naturally close after birth it is referred to as a patent (open) foramen ovale (PFO). It is common in patients with a congenital atrial septal aneurysm (ASA).

<span class="mw-page-title-main">Thromboembolism</span> Obstruction of a blood vessel by a clot

Thromboembolism is a condition in which a blood clot (thrombus) breaks off from its original site and travels through the bloodstream to obstruct a blood vessel, causing tissue ischemia and organ damage. Thromboembolism can affect both the venous and arterial systems, with different clinical manifestations and management strategies.

<span class="mw-page-title-main">Atrium (heart)</span> Part of the human heart

The atrium is one of the two upper chambers in the heart that receives blood from the circulatory system. The blood in the atria is pumped into the heart ventricles through the atrioventricular mitral and tricuspid heart valves.

<span class="mw-page-title-main">Foramen ovale (heart)</span> Passageway between the atria of the human heart

In the fetal heart, the foramen ovale, also foramen Botalli or the ostium secundum of Born, allows blood to enter the left atrium from the right atrium. It is one of two fetal cardiac shunts, the other being the ductus arteriosus. Another similar adaptation in the fetus is the ductus venosus. In most individuals, the foramen ovale closes at birth. It later forms the fossa ovalis.

<span class="mw-page-title-main">Vascular disease</span> Medical condition

Vascular disease is a class of diseases of the vessels of the circulatory system in the body, including blood vessels – the arteries and veins, and the lymphatic vessels. Vascular disease is a subgroup of cardiovascular disease. Disorders in this vast network of blood and lymph vessels can cause a range of health problems that can sometimes become severe, and fatal. Coronary heart disease for example, is the leading cause of death for men and women in the United States.

In cardiology, a cardiac shunt is a pattern of blood flow in the heart that deviates from the normal circuit of the circulatory system. It may be described as right-left, left-right or bidirectional, or as systemic-to-pulmonary or pulmonary-to-systemic. The direction may be controlled by left and/or right heart pressure, a biological or artificial heart valve or both. The presence of a shunt may also affect left and/or right heart pressure either beneficially or detrimentally.

<span class="mw-page-title-main">CT pulmonary angiogram</span> Medical imaging of blood flow between heart and lungs

A CT pulmonary angiogram (CTPA) is a medical diagnostic test that employs computed tomography (CT) angiography to obtain an image of the pulmonary arteries. Its main use is to diagnose pulmonary embolism (PE). It is a preferred choice of imaging in the diagnosis of PE due to its minimally invasive nature for the patient, whose only requirement for the scan is an intravenous line.

Embolectomy is the emergency interventional or surgical removal of emboli which are blocking blood circulation. It usually involves removal of thrombi, and is then referred to as thromboembolectomy or thrombectomy. Embolectomy is an emergency procedure often as the last resort because permanent occlusion of a significant blood flow to an organ leads to necrosis. Other involved therapeutic options are anticoagulation and thrombolysis.

<span class="mw-page-title-main">Arterial embolism</span> Interruption of blood flow to an organ

Arterial embolism is a sudden interruption of blood flow to an organ or body part due to an embolus adhering to the wall of an artery blocking the flow of blood, the major type of embolus being a blood clot (thromboembolism). Sometimes, pulmonary embolism is classified as arterial embolism as well, in the sense that the clot follows the pulmonary artery carrying deoxygenated blood away from the heart. However, pulmonary embolism is generally classified as a form of venous embolism, because the embolus forms in veins. Arterial embolism is the major cause of infarction.

<span class="mw-page-title-main">Arterial occlusion</span>

Arterial occlusion is a condition involving partial or complete blockage of blood flow through an artery. Arteries are blood vessels that carry oxygenated blood to body tissues. An occlusion of arteries disrupts oxygen and blood supply to tissues, leading to ischemia. Depending on the extent of ischemia, symptoms of arterial occlusion range from simple soreness and pain that can be relieved with rest, to a lack of sensation or paralysis that could require amputation.

References

  1. 1 2 Kumar, Vinay; Abbas; Aster (2018). Robbins Basic Pathology, Tenth Edition. Elsevier. pp. 97–119.
  2. 1 2 3 4 5 6 Amin; Kresowik; Nicholson (2014). Current Therapy in Vascular and Endovascular Surgery, Fifth Edition. Elsevier. pp. 629–631.
  3. ↑ Pollack, Jeffery (2021). Image-Guided Interventions: Pulmonary Arteriovenous Malformations. Elsevier. pp. 434–440.
  4. ↑ Maron, Bradley A.; Shekar, Prem S.; Goldhaber, Samuel Z. (2010-11-09). "Paradoxical Embolism". Circulation. 122 (19): 1968–1972. doi: 10.1161/CIRCULATIONAHA.110.961920 . PMID   21060086.
  5. ↑ Kemp; Brown; Burns (2008). Neuropathology. Pathology: The Big Picture. McGraw Hill. pp. Chapter 11.
  6. ↑ Meacham, Robert R. III; Headley, A. Stacey; Bronze, Michael S.; Lewis, James B.; Rester, Michelle M. (1998-03-09). "Impending Paradoxical Embolism". Archives of Internal Medicine. 158 (5): 438–448. doi:10.1001/archinte.158.5.438. ISSN   0003-9926. PMID   9508221.
  7. 1 2 3 4 5 6 7 8 Windecker, Stephan; Storteky, Stefan; Meier, Bernhard (2014). "Paradoxical Embolism". Journal of the American College of Cardiology. 64 (4): 403–415. doi:10.1016/j.jacc.2014.04.063. PMID   25060377.
  8. ↑ Saremi, Farhood (Oct 13, 2014). "Paradoxical Embolism: Role of Imaging in Diagnosis and Treatment Planning". RadioGraphics. 34 (6): 1571–1592. doi:10.1148/rg.346135008. PMID   25310418.
  9. ↑ "Deep vein thrombosis - Symptoms and causes". Mayo Clinic. Retrieved 2022-04-11.
  10. 1 2 3 4 "Paradoxical Embolism Clinical Presentation: History, Physical Examination, Complications". emedicine.medscape.com. Retrieved 2022-04-11.
  11. 1 2 3 4 5 Hakman, Eryk N.; Cowling, Kathleen M. (2022), "Paradoxical Embolism", StatPearls, Treasure Island (FL): StatPearls Publishing, PMID   29262019 , retrieved 2022-04-11
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