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Ablation: A form of treatment that uses electrical energy, heat, cold, alcohol, or other modalities to destroy a small section of damaged heart tissue.

Aldosterone: A hormone secreted by the adrenal glands that signals the kidneys to conserve sodium and water; the result is higher blood pressure.

Alpha blockers: A group of drugs that lower blood pressure by blocking the effects of adrenaline or adrenaline-like substances on cells’ alpha receptors. Alpha blockers are also known as alpha-adrenergic antagonists, alpha-adrenergic blocking agents, and alpha-adrenergic blockers.

Aneurysm: A weak spot in a blood vessel wall that can balloon out. An aneurysm can be life-threatening if it bursts.

Angina: The medical term for chest pain or discomfort that occurs when the heart muscle (myocardium) is not getting as much blood as it needs. Stableangina, also known as angina pectoris, is a predictable form usually triggered by activity or stress and generally relieved by nitroglycerin or rest. Unstable angina is unexpected chest pain of increasing intensity and/or frequency, often occurring at rest. Unstable angina should be treated as an emergency, just like a heart attack or stroke.

Angiogenesis: The formation of new blood vessels.

Angiography: An X-ray test used to detect diseases of the blood vessels. It is performed during cardiac catheterization.

Angioplasty: A procedure used to widen narrowed arteries, most commonly by inserting a thin tube, or catheter, into the affected artery and inflating a balloon.

Angiotensin: A chemical produced by the body that constricts blood vessels and stimulates the release of aldosterone.

Angiotensin II receptor blockers (ARBs): A class of drugs that blocks the effects of angiotensin. Like ACE inhibitors, they keep coronary arteries open, lower blood pressure, and reduce the heart’s workload.

Angiotensin-converting enzyme (ACE) inhibitor: A class of drugs that stops the production of angiotensin. This lowers blood pressure and reduces the heart’s workload. ACE inhibitors are used to treat high blood pressure and heart failure.

Ankle-brachial index: A test that compares blood pressure at the ankle with blood pressure at the elbow. It is used to screen for the presence of significant peripheral artery disease.

Anticoagulants: Drugs that diminish the blood’s ability to clot. Anticoagulants are sometimes called blood thinners although they do not actually thin the blood. Commonly used anticoagulant drugs include heparin and warfarin.

Antihypertensives: Medications used to treat high blood pressure.

Antioxidant: A substance that inhibits tissue oxidation.

Antiplatelets: Medications that interfere with blood clotting by inhibiting the activity of platelets.

Aorta: The large artery emerging from the heart’s left ventricle that distributes blood to the body.

Aortic valve: A three-flap valve between the left ventricle and the aorta.

Aphasia: Inability to speak; a common occurrence after a stroke affecting the left hemisphere of the brain, where language is processed.

Apolipoproteins: Proteins that combine with cholesterol and triglyceride to form lipoproteins.

Arrhythmia: An abnormal heart rhythm.

Arterial Pressure: The pressure that the artery walls exert on blood flow; in general, the less elastic the arteries, the greater the arterial resistance and the higher the blood pressure.

Arterioles: Small, muscular branches of arteries.

Arteriosclerosis: A term encompassing a variety of conditions in which artery walls thicken and become less flexible. Sometimes called hardening of the arteries. Arteriosclerosis occurs when cholesterol-rich plaque forms on the inner lining of arteries (atherosclerosis), when artery walls become calcified, or when high blood pressure thickens the muscular wall of arteries.

Arteriovenous Malformation: An abnormal tangle of blood vessels in which the arteries feed directly into the veins.

Artery: Vessels that carry blood from the heart to the various parts of the body.

Asystole: The absence of electrical activity in the heart.

Atherosclerosis: Thickening of the inner layer of artery walls from the buildup of fat and cholesterol that narrows the passageway and restricts blood flow. Atherosclerosis is the disease responsible for most heart attacks and many strokes.

Atherosclerotic Plaque: A cholesterol-rich deposit on an artery wall.

Atherothrombotic Stroke: A type of stroke that occurs when a large artery to the brain is completely blocked by the formation of a clot.

Atrial Fibrillation: A common heart rhythm disturbance in which the atria quiver ineffectually, allowing blood to pool in the left atrium and form clots that may travel to the brain and cause an embolic stroke.

Atrioventricular (AV) Node: A major part of the electrical system in the heart that acts as a gateway between the atria and the ventricles. An electrical signal generated by the sinoatrial node (the heart’s natural pacemaker) moves through the heart until it reaches the atrioventricular node, a cluster of cells at the bottom of the right atrium. The AV node delays the signal before it is passed to the ventricles. This lets the atria fully contract before the ventricles contract.

Atrium (plural, atria): One of the heart’s two upper chambers. The right atrium receives deoxygenated blood from the body; the left atrium receives oxygenated blood from the lungs.

Autonomic Nervous System: The part of the nervous system that controls involuntary processes, such as heartbeat and breathing. Its two arms are the sympathetic and parasympathetic nervous systems.

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Basilar Artery: The artery that supplies blood to the cerebellum, the brainstem, and the back of the brain.

Beta-Blockers: A class of drugs that slows the heartbeat, lessens the force of each contraction, and reduces the contraction of blood vessels in the heart, brain, and throughout the body by blocking the action of beta-adrenergic substances such as adrenaline (epinephrine) at the beta receptor. Beta blockers, also known as beta-adrenergic blocking agents, are used to treat many cardiovascular conditions, including abnormal heart rhythms, angina, and high blood pressure. They also improve survival after a heart attack.

Blood Pressure: The force the heart exerts against the walls of the arteries. Optimal blood pressure is less than 140/80 mm Hg.

Body Mass Index (BMI): A formula devised to compare body weight relative to height. To calculate your BMI using metric units, divide your weight in kilograms by your height in meters squared. Using English units, multiply your weight in pounds by 703, then divide the result by your height in inches, and divide that result by your height in inches. A healthy BMI is defined as 18.5 to 24.9. Calculators such as one from the National Heart, Lung, and Blood Institute simplify the process.

Bradycardia: A slow heart rate, usually below 60 beats per minute.

Brainstem: The brain structure that is the major communication route among the brain, spinal cord, and peripheral nerves; it controls heart rate, breathing, and other vital functions.

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C-Reactive Protein (CRP): A by-product of inflammation. An elevated level of high-sensitivity CRP can indicate chronic, system-wide inflammation which can increase the risk of heart attack or stroke.

Calcium Channel Blockers: A class of drugs that lowers blood pressure, slows the heart rate, and decreases the heart’s need for oxygen by blocking the movement of calcium into the heart and the muscle cells surrounding blood vessels.

Capillaries: Tiny blood vessels linking arteries and veins. Capillaries distribute oxygen-rich blood to the body’s tissues.

Cardiac Arrest: The sudden cessation of the heart’s contractions which circulate blood to the body and brain. Also called sudden cardiac arrest. Cardiac arrest usually occurs as a result of a rapid ventricular rhythm (ventricular tachycardia) or a chaotic one (ventricular fibrillation or cardiac standstill). Death occurs within minutes unless cardiopulmonary resuscitation and/or defibrillation devices are available.

Cardiac Resynchronization Therapy: A pacemaker-based therapy for heart failure that improves the heart’s pumping efficiency by coordinating (resynchronizing) the beat of the ventricles.

Cardiopulmonary Bypass: The use of a machine (heart/lung machine) to circulate and oxygenate the blood while surgery is performed on the heart.

Cardiopulmonary Resuscitation (CPR): A combination of chest compressions and mouth-to-mouth breathing that keep oxygenated blood circulating to the brain and other tissues.

Cardiovascular: Refers to the heart and blood vessels. ”cardio” = heart; ”vascular” = blood vessels.

Cardioversion: The use of an electrical shock to stop an abnormal heart rhythm ( arrhythmia) and restore a normal one (sinus rhythm ). Cardioversion can be external, using pads applied to the chest, or internal, from a pacemaker-like device called an implantable cardioverter defibrillator (ICD).

Carotid Artery: One of two major vessels, on either side of the neck, that supply blood to the brain; each one divides into external carotid, which carries blood to the face and neck, and the internal carotid, which carries blood to the brain.

Carotid Artery Disease: Narrowing of the carotid artery by the buildup of atherosclerotic plaque. Sometimes called carotid artery stenosis. It is a major risk factor for ischemic stroke.

Carotid Bruit: An abnormal sound heard with a stethoscope in the carotid artery; people who have carotid bruits have a greater risk of having a stroke.

Carotid Endarterectomy: A surgical procedure that removes plaque from the carotid artery and restores normal blood flow to the brain.

Cerebral Aneurysm: A weakening and ballooning of the wall of an artery in the brain.

Cerebral Angiography: An invasive imaging procedure used to make detailed x-ray pictures of the blood vessels in the brain; dye is injected into the carotid arteries to highlight the blood vessels on x-rays.

Cerebral Hemorrhage: Another term for brain hemorrhage.

Cerebral Infarction: The death of part of the brain from a lack of oxygen-carrying blood.

Cerebrovascular: Referring to the brain and its blood vessels.

Cerebrovascular Accident: The medical term for a stroke.

Cholesterol: A waxy, fat-like substance produced by the liver and found in all food from animal sources; an essential component of body cells and a precursor of bile acids and certain hormones.

Chylomicron: A large, extremely low-density lipoprotein that transports lipids in the bloodstream.

Circle of Willis: A group of arteries at the base of the brain that supplies blood to all parts of the brain and provides collateral routes for blood flow if a major vessel becomes blocked.

Collateral Circulation: Alternate routes of blood supply that develop when a coronary or cerebral artery is blocked.

Combined Hyperlipidemia: A condition in which cholesterol, LDL and triglyceride levels are very high.

Computed Tomography (CT): An imaging technique that uses a computer and x-rays passed through the body at different angles to create a detailed, nearly three-dimensional picture of the body.

Congestive Heart Failure: A term for heart failure, a disorder caused by a decrease in the heart’s ability to pump blood and which is associated with the accumulation of excess fluid in the lungs or extremities.

Coronary Arteries: Blood vessels that carry oxygen-rich blood to the heart muscle.

Coronary Arteriography: An x-ray procedure that shows blood moving through the blood vessels and heart. It involves the injection into the bloodstream of a fluid (contrast agent) that can be seen on the x-ray. Also known as coronary angiography; the resulting image is called an angiogram.

Coronary Artery Bypass Surgery: Surgery that bypasses a blocked coronary artery by grafting a blood vessel taken from another part of the body. It is used to restore blood flow to the heart muscle.

Coronary Artery Disease (CAD): Narrowing or blockage of the arteries that supply blood to the heart muscle. The condition can cause angina and heart attack.

Coronary Heart Disease (CHD): See coronary artery disease.

Creatine Kinase: An enzyme produced by skeletal tissue and heart muscle. One form, creatine kinase-MB, is produced only by the heart. The amount of creatinine kinase-MB circulating in the blood is usually elevated when there has been damage to heart muscle, such as with a heart attack. Testing for this enzyme is one way to determine if someone is having a heart attack.

CT Angiography (CTA): A form of high-speed CT scanning that allows doctors to determine the type of stroke and its extent.

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Defibrillation: The delivery of an electric shock to the heart to stop an abnormal rhythm and restore a normal heartbeat.

Diabetes: A disorder in which blood glucose (sugar) levels are elevated.

Diastole: The relaxation phase of the normal heart cycle.

Diastolic Blood Pressure: The bottom number of a blood pressure reading, such as 134/78. It represents the pressure in the arteries when the heart relaxes between beats. Blood pressure is measured in millimeters of mercury (mmHg).

Diastolic Heart Failure: The inability of the heart to relax properly between beats (diastole ), making it difficult for the ventricles to fill completely with blood from the atria. This can occur when the heart muscle bulks up due to overwork or other causes or when the heart muscle stiffens and loses it flexibility.

Diuretic: A drug that can reduce the buildup of fluid in the lungs and other parts of the body by promoting the excretion of water and salts. Diuretics (also called water pills) are used to treat high blood pressure, heart failure, and some congenital heart defects.

Doppler Ultrasound: A noninvasive imaging method that uses high-frequency sound waves to view blood vessels and measure how fast blood is flowing through them.

Dysarthria: A speech disability caused by an injury to the brain centers controlling the face, mouth, neck, or throat. People with dysarthria may be able to understand speech and form the right words in their mind but cannot articulate them.

Dysphagia: Difficulty chewing and swallowing food. Dysphagia is extremely common after a stroke.

Dyspnea: Difficulty breathing or shortness of breath.

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Echocardiography: A diagnostic tool that uses high-frequency sound waves (ultrasound) to evaluate the heart's size, structure and motion.

Edema: Swelling due to the accumulation of fluid between cells.

Ejection Fraction: The percentage of blood pumped out of the ventricles with each heartbeat. A normal ejection fraction is typically between 55 and 70 percent.

Electrocardiogram (EKG): A recording of the electrical activity in the heart that is responsible for its contraction and relaxation.

Electron-Beam Computed Tomography (EBCT): A high-speed imaging technology use to evaluate the heart and measure calcium deposits in coronary arteries.

Electrophysiologic Testing: A procedure used to provoke known or suspected arrhythmias.

Embolic stroke: A type of stroke that occurs when a blood clot that has formed elsewhere in the body (embolus) breaks off and travels through the bloodstream until it blocks an artery that normally supplies blood to the brain.

Embolus: A blood clot or particle that forms in one part of the body then moves through the bloodstream and lodges in a blood vessel elsewhere, blocking blood flow.

Endarterectomy: Surgical removal of plaque or blood clots in an artery.

Endocarditis: An inflammation of the heart lining or valves, usually caused by bacterial infection.

Endocardium: The inner layer of the wall of the heart.

Epicardium: The outer layer of the wall of the heart.

Epinephrine: A chemical released by the sympathetic nervous system that constricts blood vessels and increases heart rate; also called adrenaline.

Essential Hypertension: High blood pressure for which there is no known underlying cause; also called primary hypertension.

Exercise Stress Test: The use of a treadmill, stationary bicycle, or other exercise machine while hooked up to heart-monitoring equipment. The test is used to determine if the heart's blood supply is sufficient and if the rhythm remains normal when the heart is stressed.

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Familial Combined Hyperlipidemia: An inherited disorder in which the liver overproduces very low-density lipoprotein, causing high levels of cholesterol or triglycerides, or both.

Familial Hypercholesterolemia: An inherited disorder in which the liver cannot properly remove low-density lipoprotein particles from the blood, causing a very high cholesterol level.

Fasting Lipid Profile: A laboratory test to determine the relative levels of high-density lipoprotein, low-density lipoprotein, triglycerides and total cholesterol in the blood. Also referred to as a lipoprotein analysis or full lipid profile.

Fatty Acids: The primary building blocks of lipids.

Fibrillation: Rapid and uncoordinated contractions of heart muscle fibers occurring in the upper chambers (atrial fibrillation) or lower chambers (ventricular fibrillation). When this occurs, the muscle may not properly contract or pump blood.

Fibrin: A stringy protein that is the principal component of a blood clot.

Fibrinogen: A chemical that is part of the blood-clotting process.

Foam Cells: Lipid-laden cells, named for their foamy appearance under the microscope. Foam cells are an early indicator of atherosclerosis.

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Heart Attack: The common term for a myocardial infarction. It refers to the damage that occurs when blood flow to part of the heart is blocked or drastically restricted. The blockage usually stems from the rupture of an atherosclerotic plaque.

Heart Block: The electrical signal that triggers a heart contraction to pass through the atrioventricular node is partially or completely blocked.

Heart Failure: The inability of the heart to pump enough blood to meet the needs of the body's organs.

Heart Murmur: An abnormal sound in the heart caused by defective heart valves or by holes in the heart walls.

Heart Rate: The number of times the heart contracts in a minute, normally 60–100 times.

Hemianopia: Defective vision or blindness in one side of the visual field in one or both eyes; may be caused by an embolic or low-flow transient ischemic attack or stroke in the posterior cerebral artery region.

Hemiparesis: Muscular weakness on one side of the body; if the right side is affected, the stroke damaged the left side of the brain.

Hemiplegia: Paralysis limited to one side of the body.

Hemorrhage: Severe bleeding leading to excessive blood loss.

Hemorrhagic Stroke: A type of stroke that occurs when a blood vessel ruptures, cutting off the supply of oxygen and nutrition to part of the brain.

Heparin: An anticoagulant drug that inhibits blood from clotting by interfering with coagulation factors. Heparin is usually administered in the hospital, either by injection or through an intravenous line.

High Blood Pressure: Increase in blood pressure above the normal range — that is, abnormally high pressure of blood flow against the artery walls; also called hypertension.

High-Density Lipoprotein (HDL): A lipoprotein that protects the arteries by transporting cholesterol from body cells to the liver and other sites for elimination; called good cholesterol.

Holter Monitor: A portable device that continuously measures and records the heart's electrical activity for 24 to 48 hours or longer.

Homocysteine: An amino acid formed as part of the normal breakdown of protein. High blood levels of homocysteine have been associated with an increased risk for heart disease. Folic acid and other B vitamins reduce blood levels of homocysteine.

Hydrogenation: The addition of hydrogen to a compound. Hydrogenation is used to solidify liquid vegetable oils. The process creates trans fats, which may be harmful to the heart and blood vessels.

Hypercholesterolemia: High levels of cholesterol in the blood.

Hypertension: The medical term for high blood pressure. Hypertension is a major risk factor for stroke because it puts excess stress on the walls of blood vessels and damages their delicate inner lining.

Hypertriglyceridemia: High levels of triglycerides in the blood. A normal triglyceride level is less than 150 mg/dL.

Hypotension: The medical term for low blood pressure.

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Implantable Cardioverter Defibrillator (ICD): A device implanted in the chest and connected to the heart that delivers a shock to stop a potentially deadly rhythm and restore a normal (sinus) rhythm.

Inferior Vena Cava: A major vein that carries blood from the lower body to the heart.

Intermittent Claudication: Periods of poor blood circulation in the legs that occurs during exercise or other physical activity that leads to pain, cramping, or fatigue in the legs and buttocks. The symptoms subside with rest. Intermittent claudication is a form of peripheral artery disease caused by the buildup of plaque in leg arteries.

Intra-Cerebral Hemorrhage: A hemorrhagic stroke that occurs when a blood vessel ruptures and bleeds into the brain tissue.

Ischemia: Decreased blood flow that limits the supply of oxygen and nutrients to organs or tissues. Ischemia usually occurs when a blood vessel is narrowed or blocked by plaque or a blood clot.

Ischemic Heart Disease: The most common form of heart disease, in which narrowed or blocked coronary arteries have difficulty supplying sections of the heart muscle with the blood they need (ischemia).

Ischemic Stroke: A stroke caused by an interruption in the flow of blood to the brain; almost always caused by a blood clot blocking a blood vessel.

Isolated Systolic Hypertension: A form of hypertension characterized by elevated systolic blood pressure and normal diastolic pressure.

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Labile Hypertension: Blood pressure that frequently fluctuates between normal and abnormal during the course of a day, often within only a few minutes.

Lacunar Stroke: A small ischemic stroke caused by the blockage of one of the smaller blood vessels in the brain; the most common effect is weakness or disability on one side of the body.

Left Ventricular Hypertrophy: Thickening of the left ventricle, the chamber of the heart that pumps blood to the body.

Left-Ventricular Assist Device (LVAD): A surgically implanted pump that augments the pumping action of the left ventricle.

Lipids: Fats, oils, and waxes that serve as building blocks for cells or as energy sources. Lipids are also capable of accumulating in the artery walls to form plaque.

Lipoprotein: A combination of fat (lipid) and protein bound together as packages. The combination allows fats and cholesterol to move easily through the blood. See low-density lipoprotein and high-density lipoprotein.

Lipoprotein(A): A type of lipid that is similar in structure to low-density lipoprotein.

Lobar Hemorrhage: An intra-cerebral hemorrhage that occurs in the white matter beneath the cerebral cortex.

Low-Density Lipoprotein (LDL): Spherical particles that transport cholesterol from the liver to the rest of the body, which can cause the buildup of plaque in the arteries; called bad cholesterol because high levels are associated with a high risk for heart attack.

Lumbar Puncture: A procedure in which a hollow needle is inserted into the lower part of the spinal canal to withdraw fluid for testing. Also called a spinal tap.

Lumen: The open space inside a blood vessel.

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Magnetic Resonance Imaging (MRI): A noninvasive imaging technique that uses magnetic fields to capture detailed images of the brain or other organs and tissues.

Malignant Hypertension: A dangerous type of high blood pressure marked by an unusually sudden rise in blood pressure to very high levels, often accompanied by headache, blurred vision, and seizures.

Meninges: The membranes that cover and protect the brain and spinal cord.

Mitral Valve: A two-flap valve situated between the left atrium and the left ventricle.

Mitral Valve Prolapse: A valve problem in which one or both of the mitral valve flaps collapse backward into the left atrium. This may allow a small amount of blood to leak backward (regurgitate) through the valve.

Mitral Valve Stenosis: A narrowing of the mitral valve opening that limits blood flow from the left atrium to the left ventricle.

Monounsaturated Fats: A type of fat that is abundant in olive, peanut, sesame, and canola oils. Monounsaturated fats are good for the heart and arteries.

Myocardial Infarction: Medical term for heart attack, the sudden death of part of the heart muscle from lack of oxygen.

Myocarditis: Inflammation of the heart muscle (myocardium).

Myocardium: The middle layer of heart tissue. The muscular myocardium is sandwiched between the outer layer (epicardium) and the inner layer (endocardium).

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Neurotransmitters: Chemicals released by nerve cells that transmit messages to other nearby cells.

Neutropenia: An abnormally low number of white blood cells.

Nitroglycerin: A drug that relaxes blood vessels and increases the supply of blood and oxygen to the heart while reducing its workload. It is commonly used to treat angina.

Norepinephrine: A neurotransmitter that constricts blood vessels.

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Obstructive Sleep Apnea: A disorder characterized by heavy snoring and interrupted breathing during sleep. Often associated with obesity, obstructive sleep apnea is a risk factor for stroke.

Oxidation: A process in which oxygen combines with a substance, altering its structure.

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Pacemaker, Artificial: An electrical device that regulates the speed and rhythm of the heart when the heart can no longer do that itself.

Pacemaker, Natural: A specialized cluster of cells called the sinoatrial node in the top of the right atrium. The pacemaker produces a steady flow of “beat now” signals that flash across the atria and then pass through the atrioventricular node to the ventricles.

Palpitations: A sensation that the heart is beating rapidly and/or irregularly.

Pathology: The underlying abnormalities in biology and physiology that contribute to or are characteristic of a disease. Percutaneous Transluminal Coronary Angioplasty: Another name for angioplasty.

Perfusion: Blood flow.

Pericarditis: Inflammation of the pericardium, the heart's sac-like covering.

Pericardium: The fibrous sac that surrounds the heart.

Peripheral Artery Disease (Pad): A condition caused by atherosclerosis in the arteries in or leading to the legs.

Peripheral Vascular Disease: A general term for diseases of blood vessels outside the heart and brain. One of the most common forms is peripheral artery disease.

Physiatrist: A physician who specializes in physical medicine and rehabilitation.

Plaque: A fatty buildup of cholesterol, calcium, and other substances inside a blood vessel.

Plasmin: An enzyme that breaks down fibrin and dissolves blood clots.

Platelets: Minute, colorless disks in the blood that are instrumental in the clotting process.

Polyunsaturated Fats: A type of fat that is abundant in soybean, corn, cottonseed, safflower, and sunflower oils, as well as in fatty fish. One type, omega-3 fats, are especially important for cardiovascular health.

Prehypertension: A condition that increases the risk of developing high blood pressure; defined as 120–139 mm Hg systolic pressure or 80–89 diastolic pressure.

Premature Atrial Contraction (PAC): An early beat in an atrium that feels like the heart skipped a beat.

Premature Ventricular Contraction (PVC): An early beat in a ventricle that feels like the heart skipped a beat.

Pulmonary Veins: The veins that carry blood from the lungs to the left atrium.

Pulse Pressure: The difference between systolic and diastolic blood pressures (systolic pressure minus diastolic pressure = pulse pressure). It may help predict heart disease risk.

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Regurgitation: Leakage of blood back into a heart chamber that occurs when a heart valve doesn't close properly.

Renal Artery Stenosis: Narrowing of an artery that supplies blood to the kidney.

Renin: An enzyme released by the kidney that stimulates production of angiotensin.

Reperfusion Therapy: Techniques used to restart circulation to part of the heart or brain that has been cut off from blood flow during a heart attack or stroke. Reperfusion may entail the use of clot-dissolving drugs, balloon angioplasty, or surgery.

Resistant Hypertension: Blood pressure that remains persistently elevated despite drug therapy and lifestyle changes. Restenosis: Re-narrowing of a blood vessel that has been widened (with or without stents) during angioplasty.

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Saturated Fats: A type of fat that is abundant in red meat, lard, butter, cheese, and vegetable oils such as palm and coconut oil. A diet high in saturate fat increases the amount of low-density lipoprotein in the bloodstream as well as the risk of heart disease.

Secondary Hypertension: High blood pressure that has an identifiable, often correctable, cause.

Septum: The muscular wall dividing the left side of the heart from the right side.

Sinoatrial Node: The natural pacemaker of the heart. Located in the right atrium, the sinoatrial node, sometimes called the sinus node, initiates the heart's electrical activity.

Sinus Rhythm: The heart's “normal” rate and rhythm.

Sphygmomanometer: An instrument used to measure blood pressure.

Stable Angina: Chest pain or discomfort that predictably happens with physical activity or stress.

Statins: Cholesterol-lowering medications that interfere with the enzyme 3-hydroxy-3-methylglutaryl-coenzyme A reductase; also known as HMG-CoA reductase inhibitors. Statins work by changing the way the liver processes lipids.

Stenosis: The narrowing of a blood vessel or heart valve.

Stent: A wire mesh tube smaller than the spring inside a ballpoint pen that is inserted into a coronary artery to prop it open once a blockage has been cleared by angioplasty.

Stress Test: A diagnostic test in which cardiovascular measurements — including heart rate, blood pressure, and electrical activity — are recorded while the heart is being stressed (usually by having the person exercise on a treadmill or bicycle).

Stroke: A “brain attack.” Occurs when a blood vessel supplying the brain becomes obstructed or tears.

Subarachnoid Hemorrhage: A hemorrhagic stroke that occurs when a blood vessel on the surface of the brain bursts and bleeds into the space between the brain and the skull; usually caused by an aneurysm or other blood vessel malformation.

Superior Vena Cava: The major vein that carries deoxygenated blood from the upper body to the heart.

Supraventricular Tachycardia: An abnormally fast heartbeat originating in heart tissue above the ventricles.

Syncope: Fainting or loss of consciousness caused by a temporary shortage of oxygen in the brain.

Systole: The contraction phase of the normal heart cycle. During systole, blood is pumped into the aorta and the pulmonary artery.

Systolic Blood Pressure: The top number of a blood pressure reading, such as 134/78. It represents the pressure in the arteries during the heart's pumping phase. Blood pressure is measured in millimeters of mercury (mmHg).

Systolic Heart Failure: The inability of the heart to pump blood efficiently due to weakening and enlargement of the ventricles. Systolic heart failure is usually caused by coronary artery disease, high blood pressure, and valvular heart disease.

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Tachycardia: An abnormally fast heartbeat, usually above 100 beats per minute.

Thrombolysis: Breaking up a blood clot.

Thrombolytic Agents: Agents or medications that dissolve blood clots and restore blood flow through a blocked artery; used to treat heart attack and stroke. Also called “clot busters.” One example is tissue plasminogen activator.

Thrombosis: The formation of a blood clot (thrombus) inside a blood vessel or a chamber of the heart.

Thrombus: A blood clot that forms inside a blood vessel or chamber of the heart.

Tissue Plasminogen Activator (tPA): A clot-dissolving drug sometimes used to halt a heart attack or stroke. tPA must be used within a few hours after symptoms begin.

Trans Fats: A type of fat made during hydrogenation of liquid vegetable oil. Trans fats are found in many solid margarines, commercially prepared baked goods, and fried foods in many restaurants. Trans fats increase harmful low-density lipoprotein, decrease protective high-density lipoprotein, and promote blood clotting and inflammation.

Transcranial Doppler Scanning: An ultrasound technique that makes images of the major arteries at the base of the brain.

Transient Ischemic Attack (TIA): A brain attack that resolves on its own within 24 hours. A TIA is often the first sign of an impending stroke, but may cause damage on its own.

Tricuspid Valve: A three-flap valve that sits between the right atrium and the right ventricle.

Triglyceride: The primary type of fat in the body and in the diet, formed from three fatty-acid molecules and one glycerol molecule.

Troponins: Proteins found in heart muscle that leak into the circulation during a heart attack or other heart injury.

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Ultrasound: High-frequency sound waves used in medical diagnosis.

Unsaturated Fats: A type of fat in which some of the hydrogen atoms in each molecule have been replaced by double bonds; includes monounsaturated and polyunsaturated fats.

Unstable Angina: Unexpected chest pain or discomfort usually occurring at rest. Unstable angina should be treated as an emergency.

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Variant Angina Pectoris: Also called Prinzmetal's angina, these are attacks of chest pain caused by spasms of one or more coronary arteries almost always while a person is at rest.

Vascular: Referring to blood vessels.

Vasoconstrictors: Substances that constrict blood vessels.

Vasodilators: Substances that widen blood vessels.

Vasospasm: A frequent complication in which a blood vessel narrows.

Vein: A vessel that carries blood from the body back to the heart.

Ventricle: One of the two lower chambers of the heart. The right ventricle pumps blood to the lungs; the left ventricle pumps blood to the rest of the body.

Ventricular Fibrillation: A deadly heart rhythm in which the ventricles contract independently of the atria and in a chaotic manner.

Ventricular Tachycardia: A very fast heartbeat that starts in the ventricles. Ventricular tachycardia can be deadly if it renders the heart unable to pump enough blood to the body.

Venules: Small veins

Vertebral Artery: One of two blood vessels that run up the back of the neck and join at the base of the skull to form the basilar artery. The vertebral arteries carry blood from the heart to the brain.

Very-Low-Density Lipoprotein (VLDL): A lipoprotein that transports triglyceride made in the liver to fat tissue in the body. VLDL eventually becomes low-density lipoprotein after the triglyceride has been removed.

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Warfarin: An anticoagulant drug that prevents blood clotting; people taking it must have regular blood tests to make sure their blood does not clot too readily or too slowly.

White-Coat Hypertension: Blood pressure elevations that occur in the doctor's office but not at home.

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Many of these definitions can be found at