Coronary thrombosis is defined as the formation of a blood clot inside a blood vessel of the heart. This blood clot may then restrict blood flow within the heart, leading to heart tissue damage, or a

myocardial infarction A myocardial infarction (MI), commonly known as a heart attack, occurs when blood flow decreases or stops to the coronary artery of the heart, causing damage to the heart muscle. The most common symptom is chest pain or discomfort which ma ...

, also known as a heart attack. Coronary thrombosis is most commonly caused as a downstream effect of atherosclerosis, a buildup of

cholesterol Cholesterol is any of a class of certain organic molecules called lipids. It is a sterol (or modified steroid), a type of lipid. Cholesterol is biosynthesized by all animal cells and is an essential structural component of animal cell memb ...

and fats in the artery walls. The smaller vessel diameter allows less blood to flow and facilitates progression to a

. Leading risk factors for coronary thrombosis are high

LDL cholesterol Low-density lipoprotein (LDL) is one of the five major groups of lipoprotein that transport all fat molecules around the body in extracellular water. These groups, from least dense to most dense, are chylomicrons (aka ULDL by the overall densi ...

, smoking,

sedentary lifestyle Sedentary lifestyle is a Lifestyle (social sciences), lifestyle type, in which one is physically inactive and does little or no physical movement and or exercise. A person living a sedentary lifestyle is often sitting or lying down while enga ...

, and

hypertension Hypertension (HTN or HT), also known as high blood pressure (HBP), is a long-term medical condition in which the blood pressure in the arteries is persistently elevated. High blood pressure usually does not cause symptoms. Long-term high b ...

Signs and symptoms

A coronary thrombus is

asymptomatic In medicine, any disease is classified asymptomatic if a patient tests as carrier for a disease or infection but experiences no symptoms. Whenever a medical condition fails to show noticeable symptoms after a diagnosis it might be considered a ...

until it causes significant obstruction, leading to various forms of

angina Angina, also known as angina pectoris, is chest pain or pressure, usually caused by insufficient blood flow to the heart muscle (myocardium). It is most commonly a symptom of coronary artery disease. Angina is typically the result of obstr ...

or eventually a

. Common warning symptoms are crushing chest pain, shortness of breath, and upper body discomfort.

Pathogenesis

Coronary thrombosis and

are sometimes used as synonyms, although this is technically inaccurate as the thrombosis refers to the blocking of blood vessels with a thrombus, while myocardial infarction refers to heart

tissue death Necrosis () is a form of cell injury which results in the premature death of cells in living tissue by autolysis. Necrosis is caused by factors external to the cell or tissue, such as infection, or trauma which result in the unregulated diges ...

due to the consequent loss of blood flow to the heart. Due to extensive

collateral circulation Collateral circulation is the alternate circulation around a blocked artery or vein via another path, such as nearby minor vessels. It may occur via preexisting vascular redundancy (analogous to engineered redundancy), as in the circle of Wil ...

, a coronary thrombus does not necessarily cause tissue death and may be asymptomatic. The formation of coronary thrombosis generally follows the same mechanism as other blood clots in the body, the

coagulation cascade Coagulation, also known as clotting, is the process by which blood changes from a liquid to a gel, forming a blood clot. It potentially results in hemostasis, the cessation of blood loss from a damaged vessel, followed by repair. The mechani ...

. Also applicable is the Virchow's triad of blood stasis,

endothelial The endothelium is a single layer of squamous endothelial cells that line the interior surface of blood vessels and lymphatic vessels. The endothelium forms an interface between circulating blood or lymph in the lumen and the rest of the ve ...

injury, and

hypercoagulable state Thrombophilia (sometimes called hypercoagulability or a prothrombotic state) is an abnormality of blood coagulation that increases the risk of thrombosis (blood clots in blood vessels). Such abnormalities can be identified in 50% of people who ...

. Atherosclerosis contributes to coronary thrombosis formation by facilitating blood stasis as well as causing local endothelial injury. Due to the large number of cases of myocardial infarction leading to death and disease in the world, there has been extensive study towards the generation of clots specifically in the

coronary arteries The coronary arteries are the arterial blood vessels of coronary circulation, which transport oxygenated blood to the heart muscle. The heart requires a continuous supply of oxygen to function and survive, much like any other tissue or organ ...

. Some areas of focus: * Coronary thrombosis can be a complication associated with drug-eluting stents. These stents that are placed to open up narrowed arteries are often infused with medicine to prevent repeat stenosis. However, they may actually lead to an increased coronary thrombus formation due to increased

tissue factor Tissue factor, also called platelet tissue factor, factor III, or CD142, is a protein encoded by the ''F3'' gene, present in subendothelial tissue and leukocytes. Its role in the clotting process is the initiation of thrombin formation from th ...

expression and delayed healing within the vessels. Furthermore, the downstream

endothelium The endothelium is a single layer of squamous endothelial cells that line the interior surface of blood vessels and lymphatic vessels. The endothelium forms an interface between circulating blood or lymph in the lumen and the rest of the ve ...

has been shown to be impaired, leading to an environment that favors formation of clots. Evidence remains inconclusive about whether these risks outweigh the benefit of a coronary arterial stent. *

Inflammation Inflammation (from la, inflammatio) is part of the complex biological response of body tissues to harmful stimuli, such as pathogens, damaged cells, or irritants, and is a protective response involving immune cells, blood vessels, and molec ...

may play a causal role in coronary artery disease and subsequent myocardial infarction due to coronary thrombosis. Increased levels of inflammation may lead to higher risk of clotting as well as an increased risk of stent/device subsequent thrombosis. There is an ongoing search for inflammatory

biomarker In biomedical contexts, a biomarker, or biological marker, is a measurable indicator of some biological state or condition. Biomarkers are often measured and evaluated using blood, urine, or soft tissues to examine normal biological processes, p ...

s that can help determine at-risk individuals. * Coronary "microembolization" is being explored as a focal point for coronary thrombus formation and subsequent sudden death due to acute myocardial infarction. * High mobility group box-1 (HMGB-1)

protein Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residues. Proteins perform a vast array of functions within organisms, including catalysing metabolic reactions, DNA replication, res ...

s as important mediators in thrombus formation. *

Coronary sinus In anatomy, the coronary sinus () is a collection of veins joined together to form a large vessel that collects blood from the heart muscle (myocardium). It delivers deoxygenated blood to the right atrium, as do the superior and inferior vena ...

thrombosis as a severe complication after procedures.. The coronary sinus is the venous counterpart to the coronary arteries, where de-oxygenated blood returns from heart tissue. A large thrombus here slows overall blood circulation to heart tissue as well as may mechanically compress a coronary artery.

Diagnosis

Coronary angiography of a STEMI patient, showing partial occlusion of left circumflex coronary artery

Clinical signs of MI or

if coronary thrombus is symptomatic: Imaging modalities used to evaluate the presence of coronary thrombi: * angioscopy * endocoronary

ultrasound Ultrasound is sound waves with frequencies higher than the upper audible limit of human hearing. Ultrasound is not different from "normal" (audible) sound in its physical properties, except that humans cannot hear it. This limit varies ...

coronary angiography Coronary () may, as shorthand in English, be used to mean: * Coronary circulation, the system of arteries and veins in mammals ** Coronary artery disease **Coronary occlusion ** A myocardial infarction, a heart attack As adjective * Referring to t ...

* magnetic resonance imaging (MRI)
Postmortem examiners may look for

Lines of Zahn Lines of Zahn are a characteristic of thrombi. They have layers, with lighter layers of platelets and fibrin, and darker layers of red blood cells. They are more present on thrombi formed with faster blood flow, more so on thrombi from the heart ...

, to determine whether blood clotted in the heart vessels before or after death.

Management

Management of symptomatic coronary thrombosis follows established treatment algorithms for myocardial infarction.Treatment options include: * emergency

coronary artery bypass grafting Coronary artery bypass surgery, also known as coronary artery bypass graft (CABG, pronounced "cabbage") is a surgical procedure to treat coronary artery disease (CAD), the buildup of plaques in the arteries of the heart. It can relieve chest pa ...

(CABG) *

stent In medicine, a stent is a metal or plastic tube inserted into the lumen of an anatomic vessel or duct to keep the passageway open, and stenting is the placement of a stent. A wide variety of stents are used for different purposes, from expandab ...

implantation * intracoronary thrombolysis *

anticoagulation Anticoagulants, commonly known as blood thinners, are chemical substances that prevent or reduce coagulation of blood, prolonging the clotting time. Some of them occur naturally in blood-eating animals such as leeches and mosquitoes, where the ...

with

heparin Heparin, also known as unfractionated heparin (UFH), is a medication and naturally occurring glycosaminoglycan. Since heparins depend on the activity of antithrombin, they are considered anticoagulants. Specifically it is also used in the treat ...

or glycoprotein IIb/IIIa inhibitors * thrombus aspiration as reperfusion strategy * platelet P2Y12 receptor inhibitors: The CURE trial in 2001 determined that the addition of

clopidogrel Clopidogrel — sold under the brand name Plavix, among others — is an antiplatelet medication used to reduce the risk of heart disease and stroke in those at high risk. It is also used together with aspirin in heart attacks and following ...

showed a positive effect on cardiovascular mortality, non-fatal MI, and stroke at the cost of an increased risk of major bleeding. To address the possibility of identifying and treating asymptomatic coronary artery disease to prevent development of coronary thrombosis, the COURAGE trial was published in 2018. It determined that preemptive treatment with

percutaneous coronary intervention Percutaneous coronary intervention (PCI) is a non-surgical procedure used to treat narrowing of the coronary arteries of the heart found in coronary artery disease. The process involves combining coronary angioplasty with stenting, which is the ...

(PCI) did not lead to a difference in death or myocardial infarction over a 15-year period. There are numerous treatments currently being studied for management and prevention of coronary thrombosis. Statin drugs, in addition to their primary

-lowering mechanisms of action, have been studied to target a number of pathways that may decrease coronary

inflammation Inflammation (from la, inflammatio) is part of the complex biological response of body tissues to harmful stimuli, such as pathogens, damaged cells, or irritants, and is a protective response involving immune cells, blood vessels, and molec ...

and subsequent thrombosis. Another realm of potential treatments in early stages of adoption is in therapeutic use of contrast

on thrombus dissolution.

Notable people

Terminology

Thrombosis Thrombosis (from Ancient Greek "clotting") is the formation of a blood clot inside a blood vessel, obstructing the flow of blood through the circulatory system. When a blood vessel (a vein or an artery) is injured, the body uses platelets (th ...

is defined as the formation of a thrombus (blood clot) inside a

blood vessel The blood vessels are the components of the circulatory system that transport blood throughout the human body. These vessels transport blood cells, nutrients, and oxygen to the tissues of the body. They also take waste and carbon dioxide awa ...

, leading to obstruction of blood flow within the

circulatory system The blood circulatory system is a system of organs that includes the heart, blood vessels, and blood which is circulated throughout the entire body of a human or other vertebrate. It includes the cardiovascular system, or vascular system, tha ...

. Coronary thrombosis refers to the formation and presence of thrombi in the coronary arteries of the heart. Note that the heart does not contain veins, but rather

coronary sinus In anatomy, the coronary sinus () is a collection of veins joined together to form a large vessel that collects blood from the heart muscle (myocardium). It delivers deoxygenated blood to the right atrium, as do the superior and inferior vena ...

es that serve the purpose of returning de-oxygenated blood from the heart muscle. A thrombus is a type of embolism, a more general term for any material that partially or fully blocks a blood vessel. An atheroembolism, or cholesterol embolism, is when an atherosclerotic plaque ruptures and becomes an embolism. Atherosclerosis is the progressive thickening of blood vessels and plaque formation that eventually can lead to coronary artery disease (CAD).

References

External links

{{Circulatory system pathology Heart diseases