Glossary

Acute coronary syndrome (ACS)
This is an umbrella term used to cover any group of clinical symptoms compatible with acute myocardial ischaemia (chest pain due to insufficient blood supply to the heart muscle that results from coronary artery disease). Acute coronary syndrome covers the spectrum of clinical conditions ranging from unstable angina to STEMI and NSTEMI.

American College of Chest Physicians (ACCP)
Multidisciplinary international medical society based in Northbrook, Illinois, USA, that focuses on the treatment and prevention of all diseases of the chest. It has over 16,000 active members with physicians representing all chest medicine disciplines. Publishes the journal Chest.

Angina
Heart condition characterised by intermittent chest pain. Angina usually results from coronary artery disease and may further be classified as stable or unstable angina. Stable angina refers to the more common understanding of angina related to myocardial ischemia. Unstable angina may occur unpredictably at rest which may be a serious indicator of an impending heart attack.

Angiography
Angiography is imaging of the blood vessels using X-rays or magnetic resonance tomography. The vessels are visualised by injecting contrast medium into a vein. Angiography is used to diagnose disorders of the blood vessels.

Angiotensin-converting enzyme (ACE)
Hydrolase enzyme that cleaves angiotensin I (biologically inactive) to form active angiotensin II. The inhibition of ACE is used for the treatment of high blood pressure, heart failure, diabetic nephropathy, and to delay type 2 diabetes mellitus.

Antiplatelet drug
Antiplatelet drugs are generally used for the primary or secondary prevention of blood clots in patients with cardiovascular disease. Rather than acting on the coagulation cascade, antiplatelet drugs prevent platelets from joining together to form clots.

Antithrombin
Antithrombin, also known as antithrombin III, is the most important member of a larger family of antithrombins. It is a small protein molecule (a glycoprotein) produced in the liver that binds to a specific pentasaccharide sequence on heparin. This binding to heparin leads to an anticoagulant effect through two different mechanisms: It causes a conformational change in antithrombin that allows antithrombin to bind to
and thereby inhibit Factor Xa, which leads to a subsequent decrease in thrombin levels It causes a direct increase of thrombin inhibition as a result of antithrombin binding to the heparin pentasaccharide sequence and thrombin binding to an adjacent segment of heparin at the same time.

Arrhythmia
Any variation from the normal rhythm of the heart beat (e.g., sinus arrhythmia, premature beat, heart block, atrial fibrillation, atrial flutter, pulsus alternans, and paroxysmal tachycardia).

Aspirin
The brand name of acetylsalicylic acid (ASA), an antithrombotic medication that prevents thrombosis by inhibiting the activity of platelets – a component of blood that helps to prevent blood loss.

Clopidogrel
Oral antiplatelet agent used in the treatment of coronary artery disease, peripheral vascular disease and cerebrovascular disease.

Coagulation cascade
Series of reactions by which a small stimulus is amplified to produce rapid coagulation.

Coagulation factors
Group of plasma protein substances (Factor I to XIII) contained in the plasma, which act together to bring about blood coagulation.

Coagulation monitoring
Coagulation monitoring is practice of checking a specific coagulation parameter in order to adjust the dose. A precise adjustment of the drug intake allows the patient to stay within a defined therapeutic range, which is measured by prothrombin time or International Normalized Ratio (INR).

Committee for Medicinal Products for Human Use (CHMP)
The CHMP is responsible for preparing the European Medicines Agency’s (EMEA) opinions on all questions concerning medicinal products for human use. Assessments conducted by the CHMP are based on purely scientific criteria and determine whether or not the products concerned meet the necessary quality, safety, and efficacy requirements.

Compression ultrasonography
Ultrasonography scanning is widely used in medicine as an effective method of imaging the soft tissues of the body. Compression ultrasonography combines real-time imaging of the deep veins with venous compression to diagnose DVT. It has become the noninvasive method of choice for DVT diagnosis on the basis of its excellent accuracy and wide availability.

Computed tomography (CT)
Also know as CAT scan. A radiographic technique that uses a computer to assimilate multiple X-ray images into a two-dimensional cross-sectional image.

Congestive heart failure
Congestive heart failure (CHF) is a condition with impaired ability of the heart to fill with or pump a sufficient amount of blood through the body. Typical symptoms include shortness of breath with exertion, difficulty breathing when lying flat and leg or ankle swelling.

Coronary artery disease
Coronary artery disease (CAD) is the end result of the accumulation of plaques within the walls of the arteries that supply the muscle of the heart with oxygen and nutrients. The process by which the coronary arteries become narrowed or completely occluded is known as atherosclerosis.

Coumarin
A chemical found naturally in many plants, notably woodruff. It is the precursor
for warfarin.

Dabigatran
The active form of the prodrug dabigatran etexilate, an oral direct thrombin inhibitor.

Dalteparin
A low-molecular-weight heparin. It is administered by subcutaneous injection.

Enoxaparin
A low-molecular-weight heparin currently regarded as the standard of care for VTE prevention in orthopaedic surgery. Enoxaparin is administered by subcutaneous injection and is associated with a low risk of heparin-induced thrombocytopaenia.

Factor Xa
The activated form of Factor X. It catalyses the conversion of prothrombin to thrombin in conjunction with other cofactors.

Fibrin
The primary end product of the coagulation cascade. Fibrin links itself into strands to form a net. This net traps blood cells and tightens itself through cross-linkages, resulting in a dense blood clot.

Fibrinolytic system
A system that balances the formation and dissolution of fibrin.

Fondaparinux
An indirect Factor Xa inhibitor comprising a synthetic pentasaccharide sequence matching the part of the heparin molecule that binds to antithrombin. It is administered by subcutaneous injection.

Haemostasis
The prevention of blood loss, either by the physiological properties of vasoconstriction and coagulation or by surgical means.

Heparin
An anticoagulant that exerts its activity by binding to antithrombin and greatly increasing its activity. The principal coagulation factors inhibited by heparin are Factors IIa and Xa. It is administered by intravenous or subcutaneous injection.

Heparin-induced thrombocytopaenia
Thrombocytopaenia (low platelet counts) due to the administration of heparin. While it is mainly associated with UFH, it can also occur with exposure to LMWH although at significantly lower rates. Despite the low platelet count, it is a thrombotic disorder with very high rates of thrombosis in the arteries, with or without venous complications.

Hypercoagulability
A potentially dangerous state of an increased tendency for blood to coagulate, even within blood vessels. Hypercoagulability can be an inherited condition (e.g., Factor V Leiden mutation) or acquired through circumstance (e.g., cancer).

Hypercoagulable state
Changes in the blood that promote coagulation.

Hypertension
Persistently high arterial blood pressure. Hypertension may have no known cause (essential or idiopathic hypertension) or be associated with other primary diseases (secondary hypertension). This condition is considered a risk factor for the development of heart disease, peripheral vascular disease, stroke, and kidney disease.

Intermittent pneumatic compression (IPC)
A mechanical method of preventing DVT in the legs. IPC machines use air bladders that are wrapped around the thigh and/or calf. These alternately inflate and deflate, squeezing the muscles and increasing blood flow.

International Normalised Ratio (INR)
A system for standardising the reports of blood clotting tests and used to monitor the effects of warfarin. INR values should remain within 2.0–3.0 to ensure optimal safety and efficacy in patients with atrial fibrillation.

Intravenous (iv)
Administration of liquid substances directly into the venous part of the bloodstream.

Ischaemic stroke
Potentially fatal brain damage due to interrupted blood supply to the brain caused by thrombosis or an embolism.

Low-molecular-weight heparin (LMWH)
An anticoagulant derived from unfractionated heparin (UFH), containing only the low-molecular-weight molecules of heparin. It binds to antithrombin, greatly increasing its activity. It inhibits coagulation Factor Xa and, to a lesser extent, Factor IIa. LMWHs are administered by subcutaneous injection.

Myocardial infarction
Destruction of heart tissue due to reduced blood flow to the heart. Also known as a heart attack. It usually results from coronary artery disease and is more severe than angina.

Nadroparin
A low-molecular-weight heparin. It is administered by subcutaneous injection.

Non-ST-segment elevation myocardial infarction (NSTEMI)
Acute ischaemia of heart tissue sufficient to cause tissue damage where there is no ST-segment elevation on electrocardiogram (ECG) recordings.

Oedema
The presence of abnormally large amounts of fluid in the intercellular tissue spaces of the body, usually used to describe demonstrable accumulation of excessive fluid in subcutaneous tissues.

Orthopaedic surgeon
A medically qualified specialist in surgery who has subspecialised in the surgery of bones.

Parenteral
Not through the alimentary canal but rather by injection through another route.

Pharmacokinetic
Relating to the disposition of drugs in the body (i.e., their absorption, distribution, metabolism, and elimination).

Plasmin
A component (enzyme) of the fibrinolytic system that breaks fibrin into small pieces.

Platelet
(Thrombocyte) Cell circulating in the blood that is involved in the cellular mechanisms of primary haemostasis leading to the formation of blood clots. When a blood vessel is injured, platelets gather at the site of injury and stick together to form a plug, thereby preventing blood loss.

Pleiotropic
Producing many effects in addition to primary one

Post-thrombotic syndrome
A syndrome that can follow a vascular thrombosis. Clinical signs and symptoms of this syndrome include chronic pain, swelling, oedema, discolouration, and in severe cases, venous ulceration. It is likely that valvular incompetence is associated with the clinical manifestations of post-thrombotic syndrome.

Procoagulant
A substance that promotes the coagulation of blood.

Prophylaxis
The prevention of a disease or pathological condition.

Prothrombin
Factor II, also called prothrombin, is converted into thrombin as part of the coagulation cascade.

Prothrombin time
Prothrombin time is a measure of how fast the extrinsic coagulation pathway is working and is used to determine the clotting tendency of blood. The reference range is approximately 12–15 seconds.

Prothrombinase complex
The prothrombinase complex consisting of the coagulation factors Xa and Va, phospholipid and calcium catalyzes the conversion of prothrombin (Factor II) to thrombin (Factor IIa).

Pulmonary hypertension
Persistent and abnormally high blood pressure in the pulmonary arteries. Pulmonary hypertension makes it difficult for blood to pass through the lungs, making it harder for the heart to pump blood and causing patients to become tired, dizzy, and short of breath.

Reverse Trendelenberg
A person in the 'Reverse Trendelenberg' position is lying on the back with their feet slightly lower than their head.

ST-segment elevation myocardial infarction (STEMI)
Acute ischaemia of heart tissue sufficient to cause tissue damage where there is ST-segment elevation on electrocardiographic (ECG) recordings.

Subcutaneous
Below the skin.

Tenase
The tenase complex is formed by the coagulation Factors VIII and IX, phospholipid and calcium, and is responsible for the activation of Factor X to Factor Xa.

Thrombin
Also called Factor IIa, thrombin performs two functions in the coagulation cascade: activating platelets, and catalysing the conversion of soluble fibrinogen into insoluble fibrin. It is formed from prothrombin by a reaction that is catalysed by Factor Xa.

Thromboplastin
A plasma protein present in tissues, platelets, and white blood cells necessary for the
coagulation of blood and, in the presence of calcium ions, necessary for the conversion
of prothrombin to thrombin. Also called Factor III.

Thromboprophylaxis
The use of medication or medical devices to prevent the formation of blood clots.

Tinzaparin
A low-molecular-weight heparin. It is administered by subcutaneous injection.

Tissue factor
Tissue factor is the cell surface receptor for Factor VIIa. The complex of tissue factor with Factor VIIa catalyses the conversion of Factor X into Factor Xa.

Tissue plasminogen activator
A component of the fibrinolytic system that converts plasminogen to plasmin.

Unfractionated heparin (UFH)
An anticoagulant that exerts its activity by binding to antithrombin and greatly increasing its activity. The principal coagulation factors inhibited by UFH are Factors IIa and Xa. It is administered by intravenous or subcutaneous injection.

Unstable angina
Unstable angina is a type of acute chest pain that occurs when the heart doesn’t get enough oxygen. It can be a warning sign of a heart attack.

Vascular injury
Damage to the endothelial layer (inner surface) of a blood vessel. This damage causes the release of tissue factor, which subsequently activates Factor X. Vascular injury can be caused, for example, by incisions made during surgery, the use of catheters, or the use of a tourniquet.

Venography
An X-ray of the veins performed by first injecting a radiopaque contrast (shows up on X-ray) into the vein in question and then taking a conventional X-ray. Used to demonstrate blockage of a vein. Commonly used in the lower extremities to diagnose DVT.

Venous catheter
A tube inserted into a vein to deliver medication (such as chemotherapy) to a patient.

Venous foot pump
There is a natural physiological pump formed by the venous plantar plexus in the sole of the foot, which imitates the natural sequence of physical venous flow. The venous foot pump consists of large venae comitantes of the lateral plantar artery that respond to the immediate effects of weight bearing rather than muscular movement.

Venous stasis
The presence of an abnormally low rate of blood flow in the veins. This can be caused by, for example, the use of a tourniquet or prolonged immobility.

Venous thromboembolism (VTE)
A condition in which a blood clot (thrombus) forms in a vein, which in some cases then breaks free and enters the circulation as an embolus, finally lodging in and completely obstructing a blood vessel, e.g., in lungs causing a PE. The term encompasses both DVT and PE.

Vitamin K
An essential cofactor in the carboxylation of glutamic residues on the procoagulant forms of Factors II, VII, IX, and X. This ultimately leads to increased formation of thrombin and fibrin.

Vitamin K antagonist (VKA)
Vitamin K antagonists block the regeneration of the reduced form of vitamin K.

Warfarin
A vitamin K antagonist. Most commonly used oral anticoagulant in chronic prevention or treatment of VTE.

Ximelagatran
Ximelagatran was the first member of the drug class of direct thrombin inhibitors that can be taken orally. It acted by directly inhibiting the actions of thrombin. Ximelagatran was withdrawn in February 2006 following safety data suggesting hepatotoxicity of the drug and that severe liver damage could develop after withdrawal.