Acute coronary syndrome (ACS)
An umbrella term used to cover any group of clinical symptoms compatible with an acute heart attack. The subtypes of acute coronary syndrome include unstable angina (in which the heart muscle is not damaged), and two forms of heart attack in which the heart muscle is damaged. These latter types are named according to the appearance of the electrocardiogram as non-ST segment elevation myocardial infarction (NSTEMI) and ST segment elevation myocardial infarction (STEMI).
Atrial fibrillation (AF)
A heart rhythm disorder where chambers in the upper heart (atria) beat more rapidly than those in the lower section of the heart. Blood is not pumped out of the upper chambers completely during beating, and may pool and form a clot. A stroke results if a section of clot dislodges from the upper chambers and becomes lodged in the brain.
Deep vein thrombosis (DVT)
A blood clot in a deep vein, usually resulting from damage to the vein or blood flow slowing down or stopping. Usually DVTs are found in the leg, but can also be in the arm.
Distal DVTs are found in deep veins of the calf, and are the most common type of DVT.
Proximal DVTs are found in the legs above the calf muscle up to the waist.
A modification of the effect of a drug when administered with another drug, usually either an increase or decrease in the action of either substance, or an effect not normally associated with either drug alone.
International Normalized Ratio (INR)
A system for assessing the clotting tendency of blood in patients receiving anticoagulant therapy. For patients with atrial fibrillation, the recommended target INR range is between 2 and 3. If the INR is higher than 3, patients are at risk of serious bleeding. If the INR is less than 2, patients are at risk of a blood clotting event.
Relative Risk Reduction (RRR)
Proportion of the control group experiencing a given outcome minus the proportion of the treatment group experiencing the outcome, divided by the proportion of the control group experiencing the outcome.
Vitamin K antagonist (VKA)
An anticoagulant that inhibits multiple steps in the blood clotting process. Administered orally, the dose varies by patient, and regular monitoring and dose adjustment is required. Vitamin K antagonists have interactions with food and other drugs. Due to the many limitations of this drug, many patients are actually not treated and many of those who are treated are outside of the required target INR range, which can be the cause for increased bleeding or a greater risk of stroke.