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Glossary

A

Acetylsalicylic acid (ASA)

A non-steroidal anti-inflammatory drug that inhibits platelet aggregation.

Acute coronary syndrome (ACS)

A range of acute myocardial ischaemic states encompassing unstable angina, non-ST-elevation myocardial infarction and ST-elevation myocardial infarction.

Angina

Chest pain caused by insufficient blood supply to the heart muscle.

Anticoagulant

An agent that is given to prevent blood from clotting or to prevent existing clots from getting larger.

Anticoagulation

An agent that is given to prevent blood from clotting or to prevent existing clots from getting larger.

Antiphospholipid antibodies

Autoimmune antibodies, including anticardiolipin antibodies and lupus anticoagulant, produced against phospholipid in cell membranes. The production of these antibodies may lead to formation of blood clots, pregnancy loss or pregnancy-related complications, and is known as antiphospholipid syndrome.

Antiplatelet agent

An agent that inhibits platelet aggregation and thereby inhibits clot formation and arteriothrombotic events.

Antiplatelet

An agent that inhibits platelet aggregation and thereby inhibits clot formation and arteriothrombotic events.

Antiplatelets

An agent that inhibits platelet aggregation and thereby inhibits clot formation and arteriothrombotic events.

Antithrombotic therapy

A therapy that reduces the formation of blood clots.

Antithrombotic

A therapy that reduces the formation of blood clots.

Aortic disease

A widening/ballooning of a portion of the aorta (aortic aneurysm) or a tear in the wall of the aorta (aortic dissection).

Aortic regurgitation

When a heart valve fails to close tightly and allows blood to flow in both directions.

Apixaban

An oral, direct Factor Xa inhibitor (Eliquis®) that has received regulatory approval for venous thromboembolism prevention in adult patients undergoing elective hip or knee replacement surgery, the treatment and secondary prevention of deep vein thrombosis and pulmonary embolism in adults, and the prevention of stroke and systemic embolism in adult patients with non-valvular atrial fibrillation.

Argatroban

An intravenously administered direct thrombin inhibitor used for the prophylaxis and treatment of thrombosis in patients with heparin-induced thrombocytopenia.

Arrhythmia

Abnormal heart rhythm as opposed to normal sinus rhythm. In arrhythmia, electrical impulses that coordinate heart rhythm are disturbed, causing the heart to beat too fast, too slow or irregularly.

Atherosclerosis

A condition in which the arterial wall thickens as a result of the accumulation of fatty deposits including cholesterol. It is a chronic inflammatory response in the arterial walls, promoted by low-density lipoproteins and caused largely by the accumulation of white blood cells, macrophages and vascular smooth muscle cells.

Atherosclerotic plaque

A thickening of the arterial wall, which may consist of cholesterol, calcium, cellular debris and vascular smooth muscle cells. The plaque may grow and lead to narrowing of the artery, causing serious problems, including heart attack, stroke or even death.

Atherothrombotic event

Formation of a blood clot within an artery as a result of atherosclerosis (build-up of fatty material within the artery).

Atrial fibrillation (AF)

The most common type of cardiac arrhythmia (irregular heartbeat) associated with an increased risk of stroke, congestive heart failure and mortality.

B

Betrixaban

An oral Factor Xa inhibitor (Bevyxxa®) that selectively blocks the active site of Factor Xa and does not require a cofactor (such as anti-thrombin) for activity. Betrixaban inhibits free Factor Xa and prothrombinase activity. By directly inhibiting Factor Xa, betrixaban decreases thrombin generation.

Biomarker

A biomarker (biological marker) is an indicator of a biological state that is objectively measured and evaluated as an indicator of normal biological processes, pathogenic processes or pharmacological responses to a therapeutic intervention. Examples of biomarkers associated with venous thromboembolism include D-dimer and soluble P-selectin.

Bioprosthetic mitral valve

A replacement mitral valve made out of natural, non-synthetic tissue, e.g. porcine heart valve.

Bivalirudin

A parenteral reversible direct inhibitor (Angiomax®) of thrombin that inhibits both circulating and clot-bound thrombin and also thrombin-mediated platelet activation and aggregation.

C

Cardiac biomarker

A substance released into the blood when the heart is damaged or stressed.

Cardiac output

The volume of blood ejected by the ventricles per minute.

Cardiac troponins

A complex of three myocardial regulatory proteins – troponin I, C and T, which are found in varying amounts in skeletal and cardiac muscle. Together, these regulate the calcium-modulated interaction of actin and myosin. Troponin levels are sensitive markers of myocardial injury and various other heart disorders.

Cardioembolic stroke

Cardioembolic stroke is caused by a blood clot that originates in the heart. This type of stroke accounts for approximately 20% of all ischaemic strokes and is usually the most severe form of stroke because of the large size of the emboli.

Cardioembolic

A blood clot that originated in the heart and has broken away and travelled via the bloodstream to another part of the body, where it causes vessel obstruction.

Cardioembolism

A blood clot that originated in the heart and has broken away and travelled via the bloodstream to another part of the body, where it causes vessel obstruction.

Cardiogenic shock

A physiological state in which failure of the heart to pump efficiently prevents adequate blood flow to the organs and is usually fatal in the absence of immediate medical treatment.

Cardiopulmonary reserve

The interdependence of the heart, lungs and oxygen-carrying capacity of any given patient.

Cardioversion

A method of re-establishing normal sinus rhythm in patients with non-valvular atrial fibrillation that can be either electrical or pharmacological.

Catheter ablation

Commonly used technique to correct cardiac arrhythmias, including atrial fibrillation. Cardiac tissue causing the arrhythmia is destroyed and normal sinus rhythm is often restored.

Cerebrovascular disease

A group of diseases of the blood vessels supplying the brain, frequently caused by hypertension. Such diseases can include stroke, haemorrhagic stroke, ischaemia or other blood vessel dysfunctions.

CHA2DS2-VASc

An index to determine the risk of stroke in patients with atrial fibrillation, which includes additional stroke risk factors to the CHADS2 score. The CHA2DS2-VASc scheme assigns points for each of the following factors: Congestive heart failure/left ventricular dysfunction (1 point), Hypertension (1 point), Age ≥75 years [doubled] (2 points), Diabetes (1 point), Stroke/transient ischaemic attack/thromboembolism [doubled] (2 points) – Vascular disease (1 point), Age 65–74 years (1 point), and Sex category [female] (1 point).

CHADS2

An index to determine the risk of stroke in patients with atrial fibrillation. One point each is assigned for the presence of: Congestive heart failure, Hypertension, Age ≥75 years and Diabetes mellitus; and two points for a history of Stroke or transient ischaemic attack.

Chronic thromboembolic pulmonary hypertension (CTEPH)

A pulmonary vascular disease caused by obstruction of the major pulmonary arteries, including from a pulmonary embolism. Manifests as non-specific symptoms such as dyspnoea on exertion, fatigue and syncope, mainly caused by right heart failure.

Claudication

Cramp-like pains in the lower legs caused by poor circulation to the leg muscles.

Coagulation monitoring

Measurement of the ability of blood to clot and the time it takes to clot.

Coagulation

The process of formation of a blood clot.

Collagenous

Relating to or containing collagen.

Compression ultrasound

A technique combining real-time ultrasound imaging of the deep veins with venous compression to diagnose deep vein thrombosis.

Computed tomography (CT)

A radiographic technique, also known as a CT scan, which uses a computer to assimilate multiple X-ray images into a two-dimensional cross-sectional image. Types of computed tomography include:
Helical/spiral CT – a computed tomography technology involving movement in a helical pattern for the purpose of increasing resolution. Most modern hospitals use spiral CT scanners.
CT pulmonary angiography – highly sensitive and specific diagnostic test, involving injection of intravenous contrast medium to visualize the pulmonary arteries.
CT venography – contrast-enhanced axial CT images, also known as ‘indirect CT venography’, are acquired in conjunction with CT pulmonary angiography and not as a standalone examination.

Coronary artery bypass grafting (CABG)

A surgical procedure used to treat coronary heart disease, which involves taking a blood vessel from another part of the body, usually the chest or leg, and attaching it to the coronary artery above and below the narrowed area or blockage. This new blood vessel (graft) diverts the flow of blood around the part of the coronary artery that is narrowed or blocked.

Coronary artery disease (CAD)

A narrowing or blockage of the coronary arteries, usually caused by atherosclerosis.

Coronary reperfusion

Restoration of blood supply to ischaemic heart tissue, using methods such as chemical dissolution of an occluding thrombus, administration of vasodilator drugs, angioplasty, catheterization or coronary artery bypass grafting.

Coronary revascularization

Restoration of blood supply to the heart, commonly performed using percutaneous coronary intervention or coronary artery bypass grafting procedures.

Creatinine clearance

The volume of blood plasma that is cleared of creatinine per unit time. Used to evaluate a patient’s renal function.

Cryptogenic stroke

A non-lacunar brain infarct without proximal arterial stenosis or an identified source of cardioembolism; also referred to as cryptogenic stroke.

Cryptogenic/idiopathic

Of unknown origin.

Cytokines

A family of diverse cell-signalling proteins secreted by many cells, which are used extensively in intercellular communication. Cytokines can be classified as proteins, peptides or glycoproteins.

D

D-dimer

A specific clinical marker of fibrin clot formation and endogenous fibrinolysis.

Dabigatran

A potent, competitive, reversible, oral direct thrombin inhibitor (Pradaxa®). Dabigatran directly inhibits free thrombin, fibrin-bound thrombin and thrombin-induced platelet aggregation. Because thrombin enables the conversion of fibrinogen into fibrin during the coagulation cascade, its inhibition prevents the development of a thrombus.

Dalteparin

A low molecular weight heparin (Fragmin®).

Danaparoid

A low molecular weight heparinoid (Orgaran®).

Deep vein thrombosis (DVT)

A thrombus in a deep vein, usually in the leg.

Diabetes mellitus

A disease characterized by hyperglycaemia due to defects in insulin production and/or action. There are two main types of diabetes mellitus: in type 1 diabetes, beta cells in the pancreas are damaged so that little or no insulin is produced; in type 2 diabetes, the pancreas does not produce enough insulin or the insulin does not work properly.

Direct Factor Xa inhibitors

A class of anticoagulant drugs that act directly on activated Factor X (Factor Xa) in the coagulation cascade and do not require antithrombin as a mediator. Examples include betrixaban, apixaban, edoxaban and rivaroxaban.

Direct thrombin inhibitors

A class of anticoagulant drugs that act directly on thrombin in the coagulation cascade. Examples include hirudin, bivalirudin, argatroban and dabigatran.

Dual antiplatelet therapy

Concurrent treatment with two antiplatelet agents.

Dyslipidaemia

An abnormal concentration of lipids or lipoproteins in the blood.

Dyspnoea

Difficult or laboured breathing; shortness of breath.

E

Echocardiogram

A sonogram that is used to obtain information about the size and shape of the heart. It can be used to detect the location and extent of any damage to heart tissue, as well as provide information on the direction of blood flow, ejection fractions and to detect thrombi inside the heart.

Echocardiography

A sonogram that is used to obtain information about the size and shape of the heart. It can be used to detect the location and extent of any damage to heart tissue, as well as provide information on the direction of blood flow, ejection fractions and to detect thrombi inside the heart.

Edoxaban

An oral, direct Factor Xa inhibitor (US: Savaysa®, Europe: Lixiana®) that selectively blocks the active site of Factor Xa and does not require a cofactor (such as anti-thrombin) for activity. Edoxaban inhibits free Factor Xa and prothrombinase activity. By directly inhibiting Factor Xa, edoxaban decreases thrombin generation.

Electrocardiogram (ECG)

An imaging technique used to record depolarization and repolarization voltages of the cardiac muscle, via detection of electrical activity by electrodes applied to the skin. Used to detect abnormal heart rhythms or cardiac muscle damage.

Emboli

Any detached, travelling intravascular mass carried by the circulation, which is capable of blocking arterial capillary beds at a site distant from its point of origin. If a thrombus breaks loose from its original site, it becomes a thromboembolus; if it is not broken down during transit, it may cause an embolism in another artery or vein.

Embolic stroke of undetermined source (ESUS)

A non-lacunar brain infarct without proximal arterial stenosis or an identified source of cardioembolism; also referred to as cryptogenic stroke.

Embolic

Any detached, travelling intravascular mass carried by the circulation, which is capable of blocking arterial capillary beds at a site distant from its point of origin. If a thrombus breaks loose from its original site, it becomes a thromboembolus; if it is not broken down during transit, it may cause an embolism in another artery or vein.

Embolism

Any detached, travelling intravascular mass carried by the circulation, which is capable of blocking arterial capillary beds at a site distant from its point of origin. If a thrombus breaks loose from its original site, it becomes a thromboembolus; if it is not broken down during transit, it may cause an embolism in another artery or vein.

Embolization

The formation or development of an embolus.

Embolus

Any detached, travelling intravascular mass carried by the circulation, which is capable of blocking arterial capillary beds at a site distant from its point of origin. If a thrombus breaks loose from its original site, it becomes a thromboembolus; if it is not broken down during transit, it may cause an embolism in another artery or vein.

Endophlebectomy

A procedure that involves unblocking venous segments that are narrowed by intraluminal scars and masses to improve circulation.

Enoxaparin

A low molecular weight heparin (Clexane®, Lovenox®), administered subcutaneously or intravenously, that irreversibly inactivates Factor Xa and to a lesser extent Factor IIa (thrombin). This inactivation is mediated by antithrombin III.

Erythropoiesis

The formation or production of red blood cells.

F

Factor V Leiden

A variant of the human Factor V gene associated with hypercoagulability disorder, which is relatively common in some populations. Carriers of Factor V Leiden have a modest risk of developing venous thromboembolism.

Factor Xa

The active form of Factor X; it forms a complex with Factor Va, phospholipid and calcium to convert prothrombin to thrombin during the coagulation cascade.

Femoral vein

A large vein of the upper thigh and pelvic region.

Fibrillating

Rapid, irregular twitching/contraction of muscle fibres.

Fibrillation

Rapid, irregular twitching/contraction of muscle fibres.

Fibrin

An insoluble filamentous protein formed from fibrinogen by the action of thrombin as the end product of the coagulation cascade; fibrin proteins stick together to form the basis of a blood clot.

Fibrinogen

A soluble plasma protein that is converted to fibrin by thrombin during the formation of blood clots via the coagulation cascade.

Fibrinolysis

A process whereby thrombi are broken down by the enzyme plasmin. Primary fibrinolysis refers to the natural process of clot breakdown by the body whereas secondary fibrinolysis refers to the medical or disease-induced breakdown of clots.

Fibrinolytic

A process whereby thrombi are broken down by the enzyme plasmin. Primary fibrinolysis refers to the natural process of clot breakdown by the body whereas secondary fibrinolysis refers to the medical or disease-induced breakdown of clots.

Fondaparinux

A synthetic Factor Xa inhibitor (Arixtra®), fondaparinux inhibits Factor Xa by selectively binding to antithrombin, thereby interrupting the blood coagulation cascade and inhibiting thrombin formation and thrombus development.

H

Haematoma

An abnormal collection of blood outside of a blood vessel; can be caused by damage to the wall of a blood vessel and subsequent leakage of blood into surrounding tissues.

Haemodynamic decompensation

The inability of the blood circulation to maintain adequate physiological functioning.

Haemodynamically unstable

Blood perfusion that is not adequate to support normal organ function, normally as a result of low blood pressure.

Haemoglobinuria

The detection of free haemoglobin in the urine.

Haemoptysis

The coughing up of blood originating from the respiratory tract below the level of the larynx.

Haemorheology

The study of flow properties of blood and its elements (plasma and formed elements, including red blood cells, white blood cells and platelets).

Haemorrhagic stroke

The rupture of an artery in the brain resulting in bleeding in or around the brain.

Heart failure

A condition that may occur when cardiac output is insufficient to meet the needs of the body and lungs. It is commonly referred to as congestive heart failure. The symptoms of heart failure usually develop quickly (acute heart failure), but they can also develop gradually over time (chronic heart failure).

Heparin-induced thrombocytopenia (HIT)

Low platelet count as a result of heparin administration.

Heparin

An endogenous polysaccharide that exerts an anticoagulant effect by potentiating the activity of antithrombin. As a pharmaceutical product, heparin is available as unfractionated heparin (UFH) or low molecular weight heparin (LMWH).

Hyperhomocysteinemia

An abnormally high level of homocysteine in the blood as a consequence of vitamin B6/B12 and folic acid deficiency.

Hypertension

Abnormally high blood pressure (the UK National Institute for Health and Care Excellence defines stage 1 hypertension as blood pressure measured in the clinic of 140/90 mm Hg or higher and subsequent ambulatory blood pressure monitoring daytime average or home blood pressure monitoring average of 135/85 mm Hg or higher).

Hypertrophic cardiomyopathy

A thickening of the heart muscle, most commonly of the septum between the ventricles, below the aortic valve.

Hypotension

Abnormally low blood pressure, especially in the arteries of the systemic circulation. It is normally defined by systolic blood pressure of less than 90/60 mm Hg

I

Infarct

An area of tissue that is dying or dead as a result of obstruction of its local blood supply.

Intermittent pneumatic compression (IPC)

A therapeutic technique designed to improve venous circulation in the limbs of patients at risk of venous thromboembolism. Used in medical devices such as air pumps, inflatable auxiliary sleeves, gloves or boots.

International normalized ratio (INR)

A standardized measure of the ability of blood to clot, which is used to monitor anticoagulation levels in patients receiving vitamin K antagonist therapy.

Intracerebral haemorrhage

Rupture of a blood vessel within the brain, usually in areas such as the basal ganglia, cerebellum, brainstem or cortex.

Intracranial haemorrhage (ICH)

Bleeding within the skull.

Ischaemia

Oxygen deprivation in an organ or part of the body that is a result of inadequate blood supply.

Ischaemic

Oxygen deprivation in an organ or part of the body that is a result of inadequate blood supply.

L

Lacunar

Relating to the occlusion of a small artery that provides blood to the deep structures of the brain.

Laparoscopy

A minimally invasive surgical procedure using a fibre-optic instrument inserted through the abdominal wall to directly view the organs of the abdomen and pelvis.

Left atrial appendage (LAA)

Small ear-shaped sac in the muscle wall of the left atrium of the heart, in which thrombi can form, particularly in patients with non-valvular atrial fibrillation when blood is not pumped in the normal, orderly way.

Left atrium

Top-left chamber of the heart. In normal sinus rhythm, blood is squeezed out of the left atrium into the left ventricle (bottom-left chamber of the heart).

Left ventricular ejection fraction

The volume of blood pumped out of the left ventricle with each heartbeat or cardiac cycle, via the aortic valve into the systemic circulation.

Left ventricular systolic function

A measure of the functionality of the left ventricle to pump blood.

Lepirudin

A direct thrombin inhibitor (Refludan®) that can be used when heparins are contraindicated.

Low molecular weight heparin (LMWH)

An endogenous polysaccharide that exerts an anticoagulant effect by potentiating the activity of antithrombin. As a pharmaceutical product, heparin is available as unfractionated heparin (UFH) or low molecular weight heparin (LMWH).

M

Magnetic resonance imaging (MRI)

An imaging technique that uses the magnetic properties of hydrogen and its interaction with both a large external magnetic field and radio waves to produce highly detailed images of the human body (alternatively known as nuclear magnetic resonance, or NMR, imaging).

Mechanical aortic valve

A durable artificial valve created from man-made/synthetic materials.

Mechanical prophylaxis

The use of a compression device (e.g. compression stockings) to increase venous outflow or reduce stasis within the leg veins.

Mechanical prosthetic valve

A durable artificial valve created from man-made/synthetic materials.

Mechanical/prosthetic heart valve

A durable artificial valve created from man-made/synthetic materials.

Mitral regurgitation

When a heart valve fails to close tightly and allows blood to flow in both directions.

Mitral stenosis

Narrowing of the mitral valve, usually caused by disease, leading to obstructed blood flow from the left atrium to the left ventricle.

Mitral valve prolapse

A condition that occurs when a portion of the mitral valve slips back into the left atrium during ventricular contraction. Can lead to backflow of blood from the left ventricle to the left atrium.

Modified Rankin scale

A rating scale used to assess the degree of disability of a patient after a stroke.

Myocardial infarction (MI)

Damage to cardiac tissue caused by blockage of a coronary artery or coronary blood vessels preventing blood flow to the heart. Depending on the extent of blockage, myocardial infarction is classified as non-ST-elevation myocardial infarction (NSTEMI; partial artery blockage) or ST-elevation myocardial infarction (STEMI; complete artery blockage).

N

Non-cardioembolic stroke

A stroke that is caused by an embolism that did not originate in the heart.

Non-ST-elevation myocardial infarction (NSTEMI)

A type of heart attack (myocardial infarction) where blood supply to the heart has been only partially, rather than completely, blocked.

Non-valvular atrial fibrillation (NVAF)

A subtype of atrial fibrillation where the patient has no mitral valve stenosis and no artificial heart valves.

Non-vitamin K antagonist oral anticoagulant (NOAC)

A group of anticoagulant drugs that includes the oral direct Factor Xa inhibitors and the oral direct thrombin inhibitors.

P

P-selectin

A cell adhesion molecule expressed on platelets and endothelial cells, which can be used as a biomarker of thrombogenesis.

P2Y12 inhibitor

An agent that binds to and inhibits the action of the P2Y12 receptor, thereby reducing platelet aggregation and blood clot formation. Examples include ticagrelor, clopidogrel and prasugrel.

Palpitation

A sensation of an irregular, hard or rapid heartbeat.

Parenteral

Administration of a drug via a route other than the gastrointestinal tract/digestive system, such as via subcutaneous, intramuscular or intravenous injection.

Paroxysmal atrial fibrillation

At least two recurrences of atrial fibrillation, interspersed with normal sinus rhythm, that stop within 7 days, but usually within 48 hours.

Patent foramen ovale (PFO)

When the foramen ovale, a small flap-like opening between the right and left atria, which is open during foetal development, fails to close after birth.

Percutaneous coronary intervention (PCI)

A non-surgical procedure in which a catheter is inserted into a blocked coronary artery so that a stent can be placed to allow the restoration of arterial blood flow to the cardiac tissue.

Perfusion imaging

A non-invasive imaging technique used to assess blood flow.

Peripheral arterial disease (PAD)

A condition where there is reduced blood flow to extremities, usually the legs, caused by atherosclerosis (narrowing of arteries).

Phlebitis

Inflammation of a vein.

Phlebotonic

A class of drugs derived from plant extracts and synthetic compounds commonly used to treat chronic venous insufficiency. They have been proposed to improve venous tone, stabilize capillary permeability and increase lymphatic drainage.

Plasmin/Fibrinolysin

A blood enzyme that degrades the fibrin in blood clots.

Platelet activation

The process by which platelets are stimulated by collagen exposed by a break in the endothelium or by thrombin generated in the coagulation cascade. Morphological changes then occur in the platelet surface that support the assembly of coagulation factors leading to platelet aggregation.

Platelet

An irregular, non-nucleated, disc-shaped element in the blood that is involved in blood clotting.

Post-partum

The period after childbirth through the first 6 weeks of an infant’s life.

Post-thrombotic syndrome (PTS)

The development of symptoms of chronic venous insufficiency as a long-term complication of deep vein thrombosis. Post-thrombotic syndrome is caused by venous hypertension, which leads to impaired venous return, reduced calf muscle perfusion and abnormal microvasculature function with increased tissue permeability.

Prasugrel

A platelet activation and aggregation inhibitor (US: Effient®; EU: Efient®), through the irreversible binding of its active metabolite to the P2Y12 class of ADP receptors on platelets. Because platelets participate in the initiation and/or evolution of thrombotic complications of atherosclerotic disease, inhibition of platelet function can result in a reduction in the rate of cardiovascular events.

Prosthetic heart valve

A durable artificial valve created from man-made/synthetic materials.

Prosthetic valve

A durable artificial valve created from man-made/synthetic materials.

Prothrombin G20210A mutation/Factor II mutation

A mutation in the gene responsible for the production of prothrombin that increases the tendency of the blood to clot.

Prothrombinase complex

A complex formed between Factor Xa, Factor Va, phospholipids and calcium ions. This complex catalyses the conversion of prothrombin to thrombin.

Pulmonary arterial hypertension (PAH)

A progressive disease caused by narrowing of blood vessels both within and connected to the lungs. It is characterized by an increase of blood pressure in the pulmonary artery, leading to symptoms including shortness of breath, dizziness and fainting.

Pulmonary embolism (PE)

A life-threatening condition caused by the blockage of a lung artery by an embolus, which has most-commonly developed in one of the deep veins of the leg.

Pulmonary Embolism Severity Index (PESI) and simplified PESI (sPESI)

Prognostic assessment tools to predict 30-day mortality after acute symptomatic pulmonary embolism.

Pulmonary endarterectomy

An operation that is performed to remove thrombi and scar tissue from the pulmonary arteries.

R

Recurrent event

An event that occurs more than once in a patient over time. Examples may include a recurrent venous thromboembolism (which could present as deep vein thrombosis or pulmonary embolism) or a recurrent acute coronary syndrome event.

Reduced ejection fraction

Lower-than-normal percentage of blood leaving the heart each time it contracts. An ejection fraction of ≥55% is considered normal and ≤50% is considered reduced (50–55% is borderline).

Reperfusion

Restoration of blood flow to an organ or tissue.

Revascularization

Restoration of adequate blood supply and improved oxygen levels to an area that has suffered ischaemia.

Rhythm disturbance

An abnormally fast heart rate (tachycardia) or an abnormally slow heart rate (bradycardia).

Right atrial appendage

A small muscular pouch that projects from the upper anterior portion of the right atrium.

Right-sided heart catheterization

A diagnostic procedure to assess blood flow through the heart and measure pressures inside the heart and lungs.

Risk factor

Any attribute, characteristic or exposure of an individual that increases the likelihood of developing a disease or injury. Transient risk factors are those that are temporary, such as major surgery, hospitalization and long-distance travel. Examples of persistent (permanent) risk factors include cancer or antiphospholipid syndrome.

Rivaroxaban

An oral, highly selective direct Factor Xa inhibitor (Xarelto®). Inhibition of Factor Xa interrupts the intrinsic and extrinsic pathways of the blood coagulation cascade, inhibiting both thrombin formation and the development of thrombi.

S

Sinus rhythm

Normal heart rhythm, as opposed to arrhythmia.

ST-elevation myocardial infarction (STEMI)

A type of heart attack (myocardial infarction) where a large area of the heart has been seriously damaged caused by total blockage of a coronary artery.

Stasis

A stoppage or slowdown in blood flow.

Stenosis

An abnormal narrowing or contraction of a vessel or opening.

Stent thrombosis

The development of a thrombus within an artery after implantation of a stent. A stent is a scaffold that is placed into diseased peripheral or coronary arteries. However, the body may have an immune response to the stent, leading to an inflammatory response and subsequent thrombosis.

Stent

A wire mesh, stainless steel tube that holds a cardiac artery open and keeps it from narrowing again.

Stroke

A sudden interruption in the blood supply of the brain. Ischaemic stroke, the most common type of stroke, occurs when an artery supplying blood to the brain becomes blocked, causing the surrounding brain tissue to die.

Syncope

The medical term for fainting, defined as a transient loss of consciousness and postural tone, characterized by rapid onset, short duration and spontaneous recovery.

T

Tachycardia

An abnormally rapid heart rhythm, where the heart is not able to efficiently pump oxygen-rich blood to the body.

Tachypnoea

Abnormally rapid breathing (also known as polypnoea).

Thrombectomy

Surgical excision of a thrombus from a blood vessel.

Thrombin/Factor IIa

An enzyme that activates several factors involved in the coagulation cascade (Factors V, VIII, XI, and XIII) and converts fibrinogen to fibrin, resulting in clot formation. Thrombin also activates platelets and promotes platelet aggregation.

Thrombocytopenia

A reduction in the platelet count below the normal lower limit (usually defined as 150–450×109/l).

Thromboembolic

The obstruction of a blood vessel by a blood clot that has become dislodged from another blood vessel.

Thromboembolism

The obstruction of a blood vessel by a blood clot that has become dislodged from another blood vessel.

Thrombogenic

Causing coagulation of blood or thrombi.

Thrombolysis

The dissolution of a blood clot.

Thrombolytic therapy

The use of drugs to break up or dissolve blood clots. A commonly used thrombolytic drug is tissue plasminogen activator.

Thrombophilia(s)

An abnormality of blood coagulation that increases the risk of thrombosis. Otherwise known as a hypercoagulable or prothrombotic state, thrombophilias may be hereditary (e.g. protein C or S deficiency; Factor V Leiden) or acquired (factors such as increasing age, surgery or active cancer).

Thromboplastin reagent

Thromboplastin reagents are used to monitor oral anticoagulant therapy with vitamin K antagonists for patients with thromboembolic disorders.

Thromboprophylaxis

A measure or medication taken to reduce the likelihood of the formation of a thromboembolism (blood clot).

Thrombosis

The formation of a blood clot, or thrombus, inside a blood vessel. If this clot breaks loose and gets carried by the bloodstream to obstruct blood flow in another vessel, it becomes known as a thromboembolism.

Thrombus

A blood clot formed in a blood vessel or chamber of the heart.

Ticagrelor

A platelet aggregation inhibitor (Brilique®). Ticagrelor is an oral, direct-acting, selective and reversibly binding P2Y12 receptor antagonist that prevents ADP-mediated P2Y12-dependent platelet activation and aggregation. Because platelets participate in the initiation and/or evolution of thrombotic complications of atherosclerotic disease, inhibition of platelet function has been shown to reduce the risk of cardiovascular events.

Tissue factor

An important initiator of blood coagulation present in subendothelial tissue and leukocytes. In the extrinsic coagulation pathway, tissue factor binds Factor VIIa, leading to activation of coagulation Factors IX and X, which ultimately leads to fibrin formation.

Tissue plasminogen activator (tPA)

An enzyme that aids dissolution of a blood clot (thrombolysis) via activation of plasminogen (the inactive precursor of plasmin).

Transesophageal echocardiogram (TEE)

Diagnostic procedure in which a probe emitting ultrasonic sound waves is passed down the oesophagus to assess the function of the heart. The sound waves are converted to an echocardiogram image of the heart.

Transient ischaemic attack (TIA)

A form of stroke or mini-stroke that occurs when the symptoms last only a short time (usually a few minutes) and are resolved in less than 24 hours.

Transthoracic echocardiogram (TTE)

A diagnostic test using an ultrasound device placed on the patient’s chest wall to obtain an image of the heart and large vessels.

Transthoracic echocardiography

A diagnostic test using an ultrasound device placed on the patient’s chest wall to obtain an image of the heart and large vessels.

U

Unfractionated heparin (UFH)

An endogenous polysaccharide that exerts an anticoagulant effect by potentiating the activity of antithrombin. As a pharmaceutical product, heparin is available as unfractionated heparin (UFH) or low molecular weight heparin (LMWH).

V

Valve regurgitation

When a heart valve fails to close tightly and allows blood to flow in both directions.

Valvular atrial fibrillation (VAF)

A subtype of atrial fibrillation where the patient has mitral valve stenosis or artificial heart valves.

Vascular disease

Hardening of vessels (atherosclerosis), caused by fatty deposits (plaques or atheroma). Subsequent vessel obstruction may lead to lack of blood supply to vital organs and tissues.

Vasospasm

Spasm (sudden contraction) of blood vessels.

Vena cava filter

A device inserted into the inferior vena cava to prevent a blood clot from entering the lungs.

Venoactive

A class of drugs derived from plant extracts and synthetic compounds commonly used to treat chronic venous insufficiency. They have been proposed to improve venous tone, stabilize capillary permeability and increase lymphatic drainage.

Venous thromboembolism (VTE)

A condition that comprises deep vein thrombosis (a thrombus in a deep vein, usually in the leg) and pulmonary embolism (the blockage of a lung artery by an embolus).

Venous ulceration

A complication of deep vein thrombosis, in which valves in the leg veins are damaged by the thrombus, thereby causing blood to flow the wrong way in the vein and eventually damaging the skin.

Ventilation/perfusion scanning

An imaging test commonly performed to check for the presence of a thrombus or abnormal blood flow inside the lungs (such as a pulmonary embolism), by evaluating the circulation of air (ventilation) and blood (perfusion) within the lungs using radioactive materials.

Visceral adipose tissue

A hormonally active component of body fat that is deposited alongside the soft internal organs of the body.

Vitamin K antagonist (VKA)

A drug that blocks the action of vitamin K resulting in an anticoagulant effect. Examples include warfarin, acenocoumarol and phenprocoumon.

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