prompt_front: Now, answer the following question based on the text below, only give me the answer and do not output any other words.

Question: What is the purpose of an ICD?

Read the following text and answer briefly.

Context 1: Do you know the difference between V T  and T V?
Like any exclusive club, heart disease has its own jargon, understandable only by other members of the club, particularly by cardiac care providers  For example, I remember lying in my CCU bed (that’s the Coronary Intensive Care Unit), trying to memorize the letters LAD (that’s the Left Anterior Descending, the large coronary artery whose 99% blockage had caused my MI (myocardial infarction – in my case, the so-called ‘widowmaker’ heart attack) 
To help others needing simultaneous translation of this new lingo in your research or in your own medical records, here’s a helpful list of some of the most common acronyms/terms you’ll likely find around the cardiac ward 
NOTE from CAROLYN: This entire patient-friendly, jargon-free glossary (all 8,000 words!) is also part of my book “A Woman’s Guide to Living with Heart Disease“ (Johns Hopkins University Press, November 2017) 
AA – Anti-arrhythmic: Drugs used to treat patients who have irregular heart rhythms 
Ablation – See Cardiac Ablation 
ACE Inhibitor – Angiotension Converting Enzyme inhibitor: A drug that lowers blood pressure by interfering with the breakdown of a protein-like substance involved in regulating blood pressure 
ACS – Acute Coronary Syndrome: An emergency condition brought on by sudden reduced blood flow to the heart  The first sign of acute coronary syndrome can be sudden stopping of your heart (cardiac arrest) 
AED – Automatic External Defibrillator: A portable defibrillator for use during a cardiac emergency; it can be used on patients experiencing sudden cardiac arrest by applying a brief electroshock to the heart through electrodes placed on the chest 
AF or Afib – Atrial Fibrillation: An irregular and often rapid heart rate that can cause poor blood flow to the body  Afib symptoms include heart palpitations, shortness of breath, weakness or fainting  Episodes of atrial fibrillation can come and go, or you may have chronic atrial fibrillation 
AFL – Atrial Flutter: A type of arrhythmia where the upper chambers of the heart (the atria) beat very fast, causing the walls of the lower chambers (the ventricles) to beat inefficiently as well 
A-HCM – Apical Hypertrophic Cardiomyopathy: Also called Yamaguchi Syndrome or Yamaguchi Hypertrophy, a non-obstructive form of cardiomyopathy (a disease of the heart muscle that leads to generalized deterioration of the muscle and its pumping ability) in which a portion of the heart muscle is hypertrophied (thickened) without any obvious cause although there may be a genetic link  It was first described in individuals of Japanese descent 
AI – Aortic Insufficiency: A heart valve disease in which the aortic valve does not close tightly, leading to the backward flow of blood from the aorta (the largest blood vessel) into the left ventricle (a chamber of the heart) 
AIVR – Accelerated Idioventricular Rhythm: Ventricular rhythm whose rate is greater than 49 beats/min but less than 100 beats/min, usually benign  (Ventricles are the two main chambers of the heart, left and right) 
Angina (stable) – A condition marked by distressing symptoms typically between neck and navel that come on with exertion and go away with rest, caused by an inadequate blood supply to the heart muscle typically because of narrowed coronary arteries feeding the heart muscle  Also known as Angina Pectoris  Unstable angina (UA) occurs when fatty deposits (plaques) in a blood vessel rupture or a blood clot forms, blocking or reducing flow through a narrowed artery, suddenly and severely decreasing blood flow to the heart muscle  Unstable angina is not relieved by rest; it’s dangerous and requires emergency medical attention 
Antiplatelet drugs – Medications that block the formation of blood clots by preventing the clumping of platelets (examples: Plavix, Effient, Brillinta, Ticlid, etc)  Heart patients, especially those with implanted stents after PCI, are often prescribed dual antiplatelet therapy (DAPT) which includes one of these prescribed meds along with daily low-dose aspirin 
Aorta – The main artery of the body, carrying blood from the left side of the heart to the arteries of all limbs and organs except the lungs 
Aortic Stenosis: A disease of the heart valves in which the opening of the aortic valve is narrowed  Also called AS 
Aortic valve – One of four valves in the heart, this valve allows blood from the left ventricle to be pumped up (ejected) into the aorta, but prevents blood from returning to the heart once it’s in the aorta 
AP – Apical Pulse: A central pulse located at the apex (pointy bottom) of the heart 
Apex – the lowest (pointy) tip of the heart that points downward at the base, forming what almost looks like a rounded point 
Apical Hypertrophic Cardiomyopathy (A-HCM): Also called Yamaguchi Syndrome or Yamaguchi Hypertrophy, a non-obstructive form of cardiomyopathy (a disease of the heart muscle that leads to generalized deterioration of the muscle and its pumping ability) in which a portion of the heart muscle is hypertrophied (thickened) without any obvious cause  There may be a genetic link  It was first described in people of Japanese descent 
Arrhythmia – A condition in which the heart beats with an irregular or abnormal rhythm 
AS – Aortic Stenosis: A disease of the heart valves in which the opening of the aortic valve is narrowed 
ASD – Atrial Septal Defect: See Septal Defect 
Atrial Flutter – A heart rhythm problem (arrhythmia) originating from the right atrium, most often involving a large circuit that travels around the area of the tricuspid valve (between the right atrium and the right ventricle (this is called typical atrial flutter)  Less commonly, atrial flutter can also result from circuits in other areas of the right or left atrium that cause the heart to beat fast (called atypical atrial flutter) 
Atrial Septum, the membrane that separates the left and the right upper chambers of the heart (the atria) 
Atrium – A chamber of the heart that receives blood from the veins and forces it into a ventricle or ventricles  Plural: atria 
AV – Atrioventricular: A group of cells in the heart located between the upper two chambers (the atria) and the lower two chambers (the ventricles) that regulate the electrical current that passes through it to the ventricles  Also Atrioventricular Block: An interruption or disturbance of the electrical signal between the heart’s upper two chambers (the atria) and lower two chambers (the ventricles)  Also Aortic valve: The valve that regulates blood flow from the heart into the aorta 
AVNRT – Atrioventricular Nodal Re-entry Tachycardia: a heart rhythm problem that happens when there’s an electrical short circuit in the centre of the heart, one of the most common types of SVT, most often seen in people in their twenties and thirties, and more common in women than in men 
BAV – Bicuspid Aortic Valve: The most common malformation of the heart valves in which the aortic valve has only two cusps instead of three 
BB – Beta Blocker: A blood pressure-lowering drug that limits the activity of epinephrine, a hormone that increases blood pressure 
BBB – Bundle Branch Block: – A condition in which parts of the heart’s conduction system are defective and unable to normally conduct the electrical signal, causing an irregular heart rhythm (arrhythmia) 
BMI – Body mass index: A number that doctors use to determine if you’re overweight  BMI is calculated using a formula of weight in kilograms divided by height in meters squared (BMI =W [kg]/H [m2])  Better yet, just click here to figure out your own BMI 
BNP blood test – BNP (B-type Natriuretic Peptide) is a substance secreted from the ventricles or lower chambers of the heart in response to changes in pressure that happen when heart failure develops and/or worsens  The level of BNP in the blood increases when heart failure symptoms worsen, and decreases when the heart failure condition is stable 
BP – Blood Pressure: The force or pressure exerted by the heart in pumping blood; the pressure of blood in the arteries  See also hypertension 
BrS – Brugada Syndrome: Brugada syndrome is a genetic heart disease that is characterized by distinctively abnormal electrocardiogram (EKG/ECG) findings and an increased risk of sudden cardiac arrest 
CAA – Coronary artery anomaly: A congenital defect in one or more of the coronary arteries of the heart 
CABG – Coronary Artery Bypass Graft: A surgical procedure that reroutes blood flow around a diseased or blocked blood vessel that supplies blood to the heart by grafting either a piece of vein harvested from the leg or the artery from under the breastbone 
CA – Coronary Artery: The arteries arising from the aorta that arch down over the top of the heart and divide into branches  They provide blood to the heart muscle 
CAD – Coronary Artery Disease: A narrowing of the arteries that supply blood to the heart  The condition results from a plaque rupture/blood clot or spasm and greatly increases the risk of a heart attack 
Cardiac Ablation – A procedure performed by an Electrophysiologist (EP) – a cardiologist with specialized training in treating heart rhythm problems – that typically uses catheters — long, flexible tubes inserted through a vein in the groin and threaded to the heart — to correct structural problems in the heart that cause an arrhythmia  Cardiac ablation works by scarring or destroying the tissue in your heart that triggers an abnormal heart rhythm 
Cardiac Arrest – Also known as Sudden Cardiac Arrest: The stopping of the heartbeat, usually because of interference with the electrical signal that regulates each heartbeat (often associated with coronary heart disease)  Can lead to Sudden Cardiac Death 
Cardiac Catheterization – An invasive procedure in which a catheter is inserted through a blood vessel in the wrist/arm or groin with x-ray guidance  This procedure can help provide information about blood supply through the coronary arteries, blood pressure, blood flow throughout the chambers of the heart, collection of blood samples, and x-rays of the heart’s ventricles or arteries  It’s typically performed in the cath lab during angiography 
Cardiac Resynchronization Therapy (CRT) also called bi-ventricular pacemaker: an electronic pacing device that’s surgically implanted in the chest to treat the delay in heart ventricle contractions that occur in some people with heart failure 
Cardiac Tamponade – Pressure on the heart that occurs when blood or fluid builds up in the space between the heart muscle (myocardium) and the outer covering sac of the heart (pericardium)  Also called Tamponade 
Cardiomyopathy – a chronic disease of the heart muscle (myocardium), in which the muscle is abnormally enlarged, thickened, and/or stiffened 
Cardioversion – A medical procedure in which an abnormally fast heart rate (tachycardia) or cardiac arrhythmia like atrial fibrillation is converted to a normal rhythm using electricity or drugs  Synchronized electrical cardioversion uses a therapeutic dose of electric current to the heart at a specific moment in the cardiac cycle  Chemical cardioversion uses medications to convert to normal rhythm 
Cath lab – the room in the hospital/medical clinic where cardiac catheterization procedures take place (for example, when a stent is implanted into a blocked coronary artery) 
CCB – Calcium Channel Blocker: A drug that lowers blood pressure by regulating calcium-related electrical activity in the heart 
CDS – Cardiac Depression Scale: A scale that can help assess the effects of depression occurring as a result of a heart disease diagnosis 
CHF – Heart Failure (also called Congestive Heart Failure): A condition in which the heart cannot pump all the blood returning to it, leading to a backup of blood in the vessels and an accumulation of fluid in the body’s tissues, including the lungs 
CM – Cardiomyopathy: A disease of the heart muscle that leads to generalized deterioration of the muscle and its pumping ability 
CO – Cardiac Output: The amount of blood the heart pumps through the circulatory system in one minute 
Collateral arteries – These extra coronary blood vessels are sometimes able to bypass a blockage in an artery in order to supply enough oxygenated blood to enable the heart muscle to survive when in danger of being damaged because of blockage(s) 
Collateral arteries – Blood vessels that provide an alternative arterial supply of blood to an area of the heart that’s in danger of being deprived of oxygenated blood because of one or more blocked arteries 
Congenital heart defect – one of about 35 different types of heart conditions that happen when the heart or the blood vessels near the heart don’t develop normally before a baby is born (in about 1% of live births)  Because of medical advances that treat babies born with heart defects, there are now for the first time more adults with congenital heart disease than children 
Congestive heart failure (CHF) – a chronic progressive condition that affects the pumping power of your heart muscle  Often referred to simply as heart failure, CHF specifically refers to the stage in which fluid builds up around the heart and causes it to pump inefficiently 
COPD – Chronic Obstructive Pulmonary Disease: A lung disease defined by persistently poor airflow as a result of breakdown of lung tissue (known as emphysema) and dysfunction of the small airways Often associated with smoking, it typically worsens over time 
Coronary Microvascular Disease – A heart condition that causes impaired blood flow to the heart muscle through the small vessels of the heart  Also called Microvascular Disease or Small Vessel Disease 
Coronary Reactivity Test – An angiography procedure specifically designed to examine the blood vessels in the heart and how they respond to different medications  Physicians use these images to distinguish different types of blood vessel reactivity dysfunction (such as Coronary Microvascular Disease) 
Costochondritis– the cause of severe chest pain, but NOT heart-related; it’s an inflammation of the cartilage that connects a rib to the breastbone 
Coumadin – A drug taken to prevent the blood from clotting and to treat blood clots  Coumadin is believed to reduce the risk of blood clots causing strokes or heart attacks  See also Warfarin 
Cox Maze procedure – A complex “cut-and-sew” surgical procedure done to treat atrial fibrillation through a complicated set of incisions made in a maze-like pattern on the left and right atria (the upper chambers of the heart) to permanently interrupt the abnormal electrical signals that are causing the irregular heartbeats of Afib  See also: Mini-Maze 
CP – Chest Pain (may also be felt as squeezing, pressure, fullness, pressure, heaviness, burning or tightness in the chest) 
CPR – Cardiopulmonary Resuscitation: An emergency procedure in which the heart and lungs are made to work by manually compressing the chest overlying the heart and forcing air into the lungs, used to maintain circulation when the heart stops pumping during Cardiac Arrest  Current guidelines suggest hands-only CPR  See also AED 
CQ10 – Co-enzyme Q10: A dietary supplement sometimes recommended for heart patients taking statin drugs 
CRP – C-reactive protein: A byproduct of inflammation, produce by the liver, found in the blood in some cases of acute inflammation 
CRT – Cardiac Resynchronization Therapy also called bi-ventricular pacemaker: an electronic pacing device that’s surgically implanted in the chest to treat the delay in heart ventricle contractions that occur in some people with heart failure 
CT – Computed tomography (CT or CAT scan): An x-ray technique that uses a computer to create cross-sectional images of the body 
CTA – Computerized Tomographic Angiogram: An imaging test to look at the arteries that supply the heart muscle with blood  Unlike a traditional coronary angiogram, CT angiograms don’t use a catheter threaded through your blood vessels to your heart but instead rely on a powerful X-ray machine to produce images of your heart and heart vessels 
CV – Coronary Vein: One of the veins of the heart that drain blood from the heart’s muscular tissue and empty into the right atrium 
CV – Cardiovascular: Pertaining to the heart and blood vessels that make up the circulatory system 
DBP – Diastolic blood pressure: The lowest blood pressure measured in the arteries  It occurs when the heart muscle is relaxed between beats 
DCM – Dilated Cardiomyopathy: A disease of the heart muscle, primarily affecting the heart’s main pumping chamber (left ventricle)  The left ventricle becomes enlarged (dilated) and can’t pump blood to your body with as much force as a healthy heart can 
DDI – Drug-drug interaction: A situation in which a medication affects the activity of another medication when both are administered together 
DIL – Diltiazem: A calcium channel blocker drug that acts as a vasodilator; used in the treatment of angina pectoris, hypertension, and supraventricular tachycardia 
Diuretic – A class of drugs used to lower blood pressure  Also known as “water pills” 
Dobutamine stress echocardiography: This is a form of a stress echocardiogram diagnostic test  But instead of exercising on a treadmill or exercise bike to stress the heart, the stress is obtained by giving a drug that stimulates the heart and makes it “think” it’s exercising  The test is used to evaluate your heart and valve function if you are unable to exercise  It is also used to determine how well your heart tolerates activity, and your likelihood of having coronary artery disease (blocked arteries), and it can evaluate the effectiveness of your cardiac treatment plan  See also TTE and Stress Echocardiogram 
Dressler’s syndrome – Happens to a small number of people three to four weeks after a heart attack  The heart muscle that died during the attack sets the immune system in motion, calling on lymphocytes, one of the white blood cells, to infiltrate the coverings of the heart (pericardium) and the lungs (pleura)  It also starts generating antibodies, which attack those two coverings  Chest pain (CP) is the predominant symptom; treated with anti-inflammatory drugs 
Dual Antiplatelet Therapy – Medications that block the formation of blood clots by preventing the clumping of platelets (examples Plavix, Effient, Brillinta, Ticlid, etc ) are often prescribed along with aspirin as part of what’s known as dual antiplatelet therapy, especially to patients who have undergone PCI and stent implantation 
DVT – Deep Vein Thrombosis: A blood clot in a deep vein in the calf 
ECG / EKG – Electrocardiogram: A test in which several electronic sensors are placed on the body to monitor electrical activity associated with the heartbeat 
Ectopic beats – small changes in an otherwise normal heartbeat that lead to extra or skipped heartbeats, often occurring without a clear cause, most often harmless 
EF – Ejection Fraction: A measurement of blood that is pumped out of a filled ventricle  The normal rate is 50-60% 
EKG/ECG – Electrocardiogram: A test in which several electronic sensors are placed on the body to monitor electrical activity associated with the heartbeat 
Endothelium: A single-cell layer of flat endothelial cells lining the closed internal spaces of the body such as the inside of blood vessels  Endothelial dysfunction affects the ability of these cells to help dilate blood vessels, control inflammation or prevent blood clots  The endothelium is associated with most forms of cardiovascular disease, such as hypertension, coronary artery disease, chronic heart failure, peripheral vascular disease, diabetes, chronic kidney failure, and severe viral infections 
Enhanced External Counterpulsation – EECP is an FDA-approved non-invasive, non-drug treatment for angina  It works by promoting the development of collateral coronary arteries  The therapy is widely used in prominent heart clinics such as the Cleveland Clinic, Mayo Clinic and Johns Hopkins – especially for patients who are not good candidates for invasive procedures such as bypass surgery, angioplasty or stenting 
EP – Electrophysiologist: A cardiologist who has additional training in diagnosing/treating heart rhythm disorders 
EPS – Electrophysiology Study: A test that uses cardiac catheterization to study patients who have arrhythmias (abnormal hear rhythm)  An electrical current stimulates the heart in an effort to provoke an arrhythmia, which is immediately treated with medications  EPS is used primarily to identify the origin of the arrhythmia and to test the effectiveness of medications used to treat abnormal heart rhythms 
EVH – Endoscopic Vessel Harvesting: To create the bypass graft during CABG open heart surgery, a surgeon will remove or “harvest” healthy blood vessels from another part of the body, often from the patient’s leg or arm  This vessel becomes a graft, with one end attaching to a blood source above and the other end below the blocked area  See CABG 
Exercise stress test – An exercise test (walking/running on a treadmill or pedalling a stationary bike) to make your heart work harder and beat faster  An EKG is recorded while you exercise to monitor any abnormal changes in your heart under stress, with or without the aid of drugs to enhance this assessment  See also: MIBI, Echocardiogram, Nuclear Stress Test 
Familial hypercholesterolemia (FH) – A genetic predisposition to dangerously high cholesterol levels  FH is an inherited disorder that can lead to aggressive and premature cardiovascular disease, including problems like heart attacks, strokes, or narrowing of the heart valves 
Femoral Artery: a major artery in your groin/upper thigh area, through which a thin catheter is inserted, eventually making its way into the heart during angioplasty to implant a stent; currently the most widely used angioplasty approach in the United States, but many other countries now prefer the Radial Artery access in the wrist 
FFR – Fractional Flow Reserve: A test used during coronary catheterization (angiogram) to measure pressure differences across a coronary artery stenosis (narrowing or blockage) defined as as the pressure behind a blockage relative to the pressure before the blockage 
HC – High Cholesterol: When fatty deposits build up in your coronary arteries 
HCTZ – Hydrochlorothiazide: A drug used to lower blood pressure; it acts by inhibiting the kidneys’ ability to retain water  Used to be called “water pills” 
Heart Failure – a chronic progressive condition that affects the pumping power of your heart muscle  Sometimes called Congestive Heart Failure (CHF) 
Holter Monitor – A portable monitoring device that patients wear for recording heartbeats over a period of 24 hours or more 
HTN – Hypertension: High blood pressure, the force of blood pushing against the walls of arteries as it flows through them 
Hypokinesia – Decreased heart wall motion during each heartbeat, associated with cardiomyopathy, heart failure, or heart attack  Hypokinesia can involve small areas of the heart (segmental) or entire sections of heart muscle (global)  Also called hypokinesis 
ICD – Implantable Cardioverter Defibrillator: A surgically implanted electronic device to treat life-threatening heartbeat irregularities 
IHD – Ischemic Heart Disease: heart problems caused by narrowing of the coronary arteries, causing a decreased blood supply to the heart muscle  Also called coronary artery disease and coronary heart disease 
INR – International Normalized Ratio: A laboratory test measure of blood coagulation, often used as a standard for monitoring the effects of the anti-coagulant drug, warfarin (coumadin) 
IST – Inappropriate sinus tachycardia: A heart condition seen most often in young women, in which a person’s resting heart rate is abnormally high (greater than 100 bpm), their heart rate increases rapidly with minimal exertion, and this rapid heart rate is accompanied by symptoms of palpitations, fatigue, and/or exercise intolerance 
Interventional cardiologist – A cardiologist who is trained to perform invasive heart procedures like angiography, angioplasty, percutaneous coronary intervention (PCI), implanting stents, etc 
IVS – Interventricular Septum: The stout wall that separates the lower chambers (the ventricles) of the heart from one another 
IVUS – Intravascular Ultrasound: A form of echocardiography performed during cardiac catheterization in which a transducer (a device that can act as a transmitter (sender) and receiver of ultrasound information) is threaded into the heart blood vessels via a catheter; it’s used to provide detailed information about the blockage inside the blood vessels 
LAD – Left Anterior Descending coronary artery: One of the heart’s coronary artery branches from the left main coronary artery which supplies blood to the left ventricle 
LAFB – Left Anterior Fascicular Block: A cardiac condition,distinguished from Left Bundle Branch Block because only the anterior half of the left bundle branch is defective and more common than left posterior fascicular block 
LAHB – Left Anterior Hemiblock: The Left Bundle Branch divides into two major branches – the anterior and the posterior fascicles  Occasionally, a block can occur in one of these fascicles 
Left Circumflex Artery – The artery carries oxygenated blood from the heart to the body; it’s a branch of the Left Main Coronary Artery after the latter runs its course in between the aorta and the Main Pulmonary Artery 
Left Main Coronary Artery – The artery that branches from the aorta to supply oxygenated blood to the heart via the Left Anterior Descending Artery (LAD) and the Left Circumflex Artery 
Lipids – fat-like substances found in your blood and body tissues; a lipid panel is a blood test that measures the level of specific lipids in blood to help assess your risk of cardiovascular disease, measuring four types of lipids: total cholesterol, HDL cholesterol, LDL cholesterol, and triglycerides 
Lipoprotein-a or Lp(a) – molecules made of proteins and fat, carrying cholesterol and similar substances through the blood  A high level of Lp(a) is considered a risk factor for heart disease; detectable via a blood test 
Long QT syndrome (LQTS): A heart rhythm disorder that can potentially cause fast, chaotic heartbeats that may trigger a sudden fainting spell or seizure  In some cases, the heart may beat erratically for so long that it can cause sudden death 
LV – Left Ventricle – One of four chambers (two atria and two ventricles) in the human heart, it receives oxygenated blood from the left atrium via the mitral valve, and pumps it into the aorta via the aortic valve 
LVAD – Left ventricular assist device: A mechanical device that can be placed outside the body or implanted inside the body  An LVAD does not replace the heart – it “assists” or “helps” it pump oxygen-rich blood from the left ventricle to the rest of the body, usually as a bridge to heart transplant 
LVH – Left Ventricular Hypertrophy: A thickening of the myocardium (muscle) of the Left Ventricle (LV) of the heart  
Lumen – The hollow area within a tube, such as a blood vessel 
Main Pulmonary Artery – Carries oxygen-depleted blood from the heart to the lungs 
MIBI – Nuclear Stress Test/Cardiac Perfusion Scan/Sestamibi: tests that are used to assess the blood flow to the heart muscle (myocardium) when it is stressed by exercise or medication, and to find out what areas of the myocardium have decreased blood flow due to coronary artery disease  This is done by injecting a tiny amount of radionuclide like thallium or technetium (chemicals which release a type of radioactivity called gamma rays) into a vein in the arm or hand 
Microvascular disease – a heart condition that causes impaired blood flow to the heart muscle through the small blood vessels of the heart  Symptoms mimic those of a heart attack  Also called Coronary Microvascular Disease or Small Vessel Disease  I live with this diagnosis and have written more about it here, here and here 
Mini-Maze – a surgical procedure to treat atrial fibrillation, less invasive than what’s called the Cox Maze III procedure (a “cut-and-sew” procedure), and performed on a beating heart without opening the chest 
Mitral Valve: One of four valves in the heart, the structure that controls blood flow between the heart’s left atrium (upper chamber) and left ventricle (lower chamber)  The mitral valve has two flaps (cusps)  See also MV and/or Valves 
Mitral valve prolapse: a condition in which the two valve flaps of the mitral valve don’t close smoothly or evenly, but instead bulge (prolapse) upward into the left atrium; also known as click-murmur syndrome, Barlow’s syndrome or floppy valve syndrome 
MR – Mitral regurgitation: (also mitral insufficiency or mitral incompetence) a heart condition in which the mitral valve does not close properly when the heart pumps out blood  It’s the abnormal leaking of blood from the left ventricle, through the mitral valve and into the left atrium when the left ventricle contracts 
MRI – Magnetic Resonance Imaging: A technique that produces images of the heart and other body structures by measuring the response of certain elements (such as hydrogen) in the body to a magnetic field  An MRI can produce detailed pictures of the heart and its various structures without the need to inject a dye 
MS – Mitral Stenosis: A narrowing of the mitral valve, which controls blood flow from the heart’s upper left chamber (the left atrium) to its lower left chamber (the left ventricle)  May result from an inherited (congenital) problem or from rheumatic fever 
MUGA – Multiple-Gated Acquisition Scanning: A non-invasive nuclear test that uses a radioactive isotope called technetium to evaluate the functioning of the heart’s ventricles 
Murmur – Noises superimposed on normal heart sounds  They are caused by congenital defects or damaged heart valves that do not close properly and allow blood to leak back into the originating chamber 
MV – Mitral Valve: The structure that controls blood flow between the heart’s left atrium (upper chamber) and left ventricle (lower chamber) 
Myocardial Infarction (MI, heart attack) – The damage or death of an area of the heart muscle (myocardium) resulting from a blocked blood supply to the area  The affected tissue dies, injuring the heart 
Myocardium – The muscular tissue of the heart 
New Wall-Motion Abnormalities – Results seen on an echocardiogram test report (see NWMA, below) 
Nitroglycerin – A medicine that helps relax and dilate arteries; often used to treat cardiac chest pain (angina)  Also called NTG or GTN 
NSR – Normal Sinus Rhythm: The characteristic rhythm of the healthy human heart  NSR is considered to be present if the heart rate is in the normal range, the P waves are normal on the EKG/ECG, and the rate does not vary significantly 
NSTEMI – Non-ST-segment-elevation myocardial infarction: The milder form of the two main types of heart attack  An NSTEMI heart attack does not produce an ST-segment elevation seen on an electrocardiogram test (EKG)  See also STEMI 
Nuclear Stress Test – A diagnostic test that usually involves two exercise stress tests, one while you’re exercising on a treadmill/stationary bike or with medication that stresses your heart, and another set while you’re at rest  A nuclear stress test is used to gather information about how well your heart works during physical activity and at rest  See also: Exercise stress test, Nuclear perfusion test, MIBI 
Open heart surgery – Any surgery in which the chest is opened and surgery is done on the heart muscle, valves, coronary arteries, or other parts of the heart (such as the aorta)  See also CABG 
Pacemaker – A surgically implanted electronic device that helps regulate the heartbeat 
PAD – Peripheral Artery Disease: A common circulatory problem in which narrowed arteries reduce blood flow to the limbs, usually to the legs  Symptoms include leg pain when walking (called intermittent claudication) 
PAF – Paroxysmal Atrial Fibrillation: Atrial fibrillation that lasts from a few seconds to days, then stops on its own  See also Atrial Fibrillation 
Palpitations – A noticeably rapid, strong, or irregular heartbeat due to agitation, exertion or illness 
Paroxysmal Atrial Fibrillation – An unusual heart arrhythmia of unknown origin, at one time believed to be associated with an unusual sensitivity to alcohol consumption 
PDA – patent ductus arteriosus: A persistent opening between two major blood vessels leading from the heart  The opening is called ductus arteriosus and is a normal part of a baby’s circulatory system before birth that usually closes shortly after birth  But when it remains open, it’s called a patent ductus arteriosus  If it’s small, it may never need treatment, but a large PDA left untreated can allow poorly oxygenated blood to flow in the wrong direction, weakening the heart muscle and causing heart failure or other complications 
Pericardium: two thin layers of a sac-like tissue that surround the heart, hold it in place and help it work 
PET – Positron Emission Tomography: A non-invasive scanning technique that uses small amounts of radioactive positrons (positively charged particles) to visualize body function and metabolism  In cardiology, PET scans are used to evaluate heart muscle function in patients with coronary artery disease or cardiomyopathy 
PFO – Patent Forman Ovale: An opening between the left and right atria (the upper chambers) of the heart  Everyone has a PFO before birth, but in 1 out of every 3 or 4 people, the opening does not close naturally as it should after birth 
Plaque – A deposit of fatty (and other) substances in the inner lining of the artery wall; it is characteristic of atherosclerosis 
POTS – Postural Orthostatic Tachycardia Syndrome: A disorder that causes an increased heart rate when a person stands upright 
PPCM – Post-partum cardiomyopathy: A form of cardiomyopathy that causes heart failure toward the end of pregnancy or in the months after delivery, in the absence of any other cause of heart failure 
Preeclampsia – a late-pregnancy complication identified by spikes in blood pressure, protein in the urine, possible vision problems  Women who experience pregnancy complications like preeclampsia are at significantly higher risk for heart disease 
Prinzmetal’s Variant Angina – Chest pain caused by a spasm in a coronary artery that supplies blood to the heart muscle 
PSVT – Paroxysmal Supraventricular Tachycardia: – An occasional rapid heart rate (150-250 beats per minute) that is caused by events triggered in areas above the heart’s lower chambers (the ventricles)  “Paroxysmal” means from time to time  See also supraventricular tachycardia (SVT) 
Pulmonary Valve: One of the four valves in the heart, located between the pulmonary artery and the right ventricle of the heart, moves blood toward the lungs and keeps it from sloshing back into the heart 
PV – Pulmonary Vein: A vein carrying oxygenated blood from the lungs to the left atrium of the heart 
PVC – Premature Ventricular Contraction: An early or extra heartbeat that happens when the heart’s lower chambers (the ventricles) contract too soon, out of sequence with the normal heartbeat  In the absence of any underlying heart disease, PVCs do not generally indicate a problem with electrical stability, and are usually benign 
RA – Right Atrium: The right upper chamber of the heart  The right atrium receives de-oxygenated blood from the body through the vena cava and pumps it into the right ventricle which then sends it to the lungs to be oxygenated 
Radial Artery: the artery in the wrist where a thin catheter is inserted through the body’s network of arteries in the arm and eventually into the heart during a procedure to implant a stent  Doctors may also call this transradial access, the transradial approach, or transradial angioplasty  Because it’s associated with fewer complications, this is increasingly considered the default access approach in most countries, except in the U S  where the traditional Femoral Artery (groin) approach is still the most popular access 
RBBB – Right Bundle Branch Block: A delay or obstruction along the pathway that electrical impulses travel to make your heart beat  The delay or blockage occurs on the pathway that sends electrical impulses to the right side of your heart  See also Left Bundle Branch Block 
RCA – Right Coronary Artery: An artery that supplies blood to the right side of the heart 
Restenosis – The re-closing or re-narrowing of an artery after an interventional procedure such as angioplasty or stent placement  Sometimes called “stent failure” 
RHD – Rheumatic Heart Disease: Permanent damage to the valves of the heart caused especially by repeated attacks of rheumatic fever 
RM – Right Main coronary artery: A blood vessel that supplies oxygenated blood to the walls of the heart’s ventricles and the right atrium 
RV – Right Ventricle: The lower right chamber of the heart that receives de-oxygenated blood from the right atrium and pumps it under low pressure into the lungs via the pulmonary artery 
SA – Sinus node: The “natural” pacemaker of the heart  The node is a group of specialized cells in the top of the right atrium which produces the electrical impulses that travel down to eventually reach the ventricular muscle, causing the heart to contract 
SB – Sinus Bradycardia: Abnormally slow heartbeat 
SBP – Systolic Blood Pressure: The highest blood pressure measured in the arteries  It occurs when the heart contracts with each heartbeat  Example: the first number in 120/80 
SCAD – Spontaneous Coronary Artery Dissection: A rare emergency condition that occurs when a tear forms in one of the blood vessels in the heart, causing a heart attack, abnormalities in heart rhythm and/or sudden death  SCAD tends to strike young healthy women with few if any cardiac risk factors 
SD – Septal defect: A hole in the wall of the heart separating the atria (two upper chambers of the heart) or in the wall of the heart separating the ventricles (two lower chambers) 
Sestamibi stress test – See MIBI 
Short QT intervals (SQT): An abnormal heart rhythm where the heart muscle takes a shorter time to recharge between beats  It can cause a variety of complications from fainting and dizziness to sudden cardiac arrest 
Sick Sinus Syndrome (also known as sinus node dysfunction) is caused by an electrical problem in the heart; a group of related heart conditions that can affect how the heart beats, most commonly in older adults, although it can be diagnosed in people of any age  “Sick sinus” refers to the sinoatrial node (see below)  In people with sick sinus syndrome, the SA node does not function normally 
Sinoatrial node (SA): also commonly called the sinus node; it’s a small bundle of neurons situated in the upper part of the wall of the right atrium (the right upper chamber of the heart)  The heart’s electrical impulses are generated there  It’s the normal natural pacemaker of the heart and is responsible for the initiation of each heartbeat 
Spontaneous Coronary Artery Dissection (SCAD) – A rare emergency condition that occurs when a tear forms in one of the blood vessels in the heart, causing a heart attack, abnormalities in heart rhythm and/or sudden death  SCAD tends to strike young healthy women with few if any cardiac risk factors 
SSS – Sick Sinus Syndrome: The failure of the sinus node to regulate the heart’s rhythm 
ST – Sinus Tachycardia: A heart rhythm with elevated rate of impulses originating from the sinoatrial node, defined as greater than 100 beats per minute (bpm) in an average adult  The normal heart rate in the average adult ranges from 60–100 bpm  Also called sinus tach or sinus tachy 
Statins – Any of a class of drugs that lower the levels of low-density lipoproteins (LDL) – the ‘bad’ cholesterol in the blood – by inhibiting the activity of an enzyme involved in the production of cholesterol in the liver  Examples of brand name statins: Lipitor, Crestor, Zocor, Mevacor, Levachol, Lescol, etc  Also available as a cheaper generic form of the drug 
STEMI – ST-elevation heart attack (myocardial infarction)  The more severe form of the two main types of heart attack  A STEMI produces a characteristic elevation in the ST segment on an electrocardiogram (EKG)  The elevated ST segment is how this type of heart attack got its name  See also NSTEMI 
Stent – An implantable device made of expandable, metal mesh (looks a bit like a tiny chicken wire tube) that is placed (by using a balloon catheter) at the site of a narrowing coronary artery during an angioplasty procedure  The stent is then expanded when the balloon fills, the balloon is removed, and the stent is left in place to help keep the artery open  TRIVIA ALERT: the coronary stent was named after Charles Stent (1807-1885), an English dentist who invented a compound to produce dentures and other things like skin grafts and hollow tubes (essentially what a metal coronary stent is)  His real claim to fame occurred when he suggested using his material to coat underwater trans-Atlantic cable, which had broken several times as a result of corrosion by seawater  You’re welcome 
Stint – a common spelling mistake when what you really mean is the word “stent” (see above) 
Stress Echocardiography – A standard echocardiogram test that’s performed while the person exercises on a treadmill or stationary bicycle  This test can be used to visualize the motion of the heart’s walls and pumping action when the heart is stressed, possibly revealing a lack of blood flow that isn’t always apparent on other heart tests  The echocardiogram is performed just before and just after the exercise part of the procedure  See also TTE 
Sudden Cardiac Arrest – The stopping of the heartbeat, usually because of interference with the electrical signal (often associated with coronary heart disease)  Can lead to Sudden Cardiac Death 
Takotsubo Cardiomyopathy – A heart condition that can mimic a heart attack  Sometimes called Broken Heart Syndrome, it is not a heart attack, but it feels just like one, with common symptoms like severe chest pain and shortness of breath  It sometimes follows a severe emotional stress  Over 90% of reported cases are in women ages 58 to 75  Also referred to as Broken Heart Syndrome, stress cardiomyopathy, stress-induced cardiomyopathy or apical ballooning syndrome 
TAVR – Transcatheter aortic valve replacement: A minimally invasive procedure to repair a damaged or diseased aortic valve  A catheter is inserted into an artery in the groin and threaded to the heart  A balloon at the end of the catheter, with a replacement valve folded around it, delivers the new valve to take the place of the old  Also called TAVI (Transcatheter aortic valve implantation) 
Tetralogy of Fallot – A rare condition caused by a combination of four heart defects that are present at birth, affecting the structure of the heart and causing oxygen-poor blood to flow out of the heart and into the rest of the body  Infants and children with Tetralogy of Fallot usually have blue-tinged skin because their blood doesn’t carry enough oxygen  Often diagnosed in infancy, but sometimes not until later in life depending on severity 
Tg – Triglycerides: The most common fatty substance found in the blood; normally stored as an energy source in fat tissue  High triglyceride levels may thicken the blood and make a person more susceptible to clot formation  High triglyceride levels tend to accompany high cholesterol levels and other risk factors for heart disease, such as obesity 
TIA – Transient Ischemic Attack: A stroke-like event that lasts only for a short time and is caused by a temporarily blocked blood vessel 
TEE – Transesophageal echocardiogram: This test involves an ultrasound transducer inserted down the throat into the esophagus in order to take clear images of the heart structures without the interference of the lungs and chest 
Treadmill Stress Test – See Exercise Stress Test 
troponin – a type of cardiac enzyme found in heart muscle, and released into the blood when there is damage to the heart (for example, during a heart attack)  A positive blood test that shows elevated troponin is the preferred test for a suspected heart attack because it is more specific for heart injury than other blood tests, especially the newer high sensitivity troponin tests (hs-cTnT) 
TTE – Transthoracic Echocardiogram: This is the standard echocardiogram, a painless test similar to X-ray, but without the radiation, using a hand-held device called a transducer placed on the chest to transmit high frequency sound waves (ultrasound)  These sound waves bounce off the heart structures, producing images and sounds that can be used by the doctor to detect heart damage and disease 
TV – Tricuspid Valve: One of four one-way valves in the heart, a structure that controls blood flow from the heart’s upper right chamber (the right atrium) into the lower right chamber (the right ventricle) 
UA or USA – Unstable Angina: Chest pain that occurs when diseased blood vessels restrict blood flow to the heart; symptoms are not relieved by rest; considered a dangerous and emergency crisis requiring immediate medical help 
Valves: Your heart has four one-way valves that keep blood flowing in the right direction  Blood enters the heart first through the tricuspid valve, and next goes through the pulmonary valve (sometimes called the pulmonic valve) on its way to the lungs  Then the blood returning from the lungs passes through the mitral (bicuspid) valve and leaves the heart through the aortic valve 
Vasodilator: A drug that causes dilation (widening) of blood vessels 
Vasospasm: A blood vessel spasm that causes sudden constriction, reducing its diameter and blood flow to the heart muscle  See also Prinzmetal’s Variant Angina 
VB – Ventricular Bigeminy: A heart rhythm condition in which the heart experiences two beats of the pulse in rapid succession 
Vena Cava – a large vein that carryies de-oxygenated blood into the heart  There are two in humans, the inferior vena cava (carrying blood from the lower body) and the superior vena cava (carrying blood from the head, arms, and upper body) 
Ventricle – each of the two main chambers of the heart, left and right 
VF – Ventricular Fibrillation: A condition in which the ventricles (two lower chambers of the heart) contract in a rapid, unsynchronized fashion  When fibrillation occurs, the ventricles cannot pump blood throughout the body  Most sudden cardiac deaths are caused by VF or ventricular tachycardia (VT) 
VLDL – Very Low Density Lipoprotein: Molecules made up of mostly triglycerides, cholesterol and proteins  VLDL, also known as the “very bad” cholesterol, carries cholesterol from the liver to organs and tissues in the body  It may lead to low density lipoproteins (LDL), associated with higher heart disease risks  VLDL levels are tricky to measure routinely, and are usually estimated as a percentage of your triglyceride levels  By reducing triglycerides, you are usually also reducing your VLDL levels 
Warfarin – A drug taken to prevent the blood from clotting and to treat blood clots  Warfarin is believed to reduce the risk of blood clots causing strokes or heart attacks  Also known as Coumadin 
Widowmaker heart attack – The type of heart attack I survived, since you asked  A nickname doctors use to describe a severely blocked left main coronary artery or proximal left anterior descending coronary artery of the heart  This term is used because if the artery gets abruptly and completely blocked, it can cause a massive heart attack that will likely lead to sudden cardiac death  Please note the gender imbalance here: despite the number of women like me who do experience this type of cardiac event, doctors are not calling this the widowermaker, after all 
WPW – Wolff-Parkinson-White Syndrome: A condition in which an extra electrical pathway connects the atria (two upper chambers) and the ventricles (two lower chambers)  It may cause a rapid heartbeat 
NOTE FROM CAROLYN: I was very happy when we were able to include this entire glossary in my book, “A Woman’s Guide to Living with Heart Disease“ (Johns Hopkins University Press, 2017) 
Are we missing any important heart acronyms/terms from this list? Let me know!
Please can someone explain something for me  I am a 53 yr old woman and generally fit and healthy  Had 2 ECG’s due to a one off dizzy spell during a stressful time dealing with my fathers terminal diagnosis  The 2nd ECG request did give me concern as i did not know why i had to have one  On 24/01/19 at my doctors appointment she explained that on 3 the leads it showed inverted T waves  And she explained that it may suggest angina  I was so shocked  Wasn’t expecting that  She gave me a GNT (nitroglycerin) spray in case I do get pain and take 75Mg of aspirin  I’m now waiting for a Cardiology referral 
I am so stressed and consumed by what might be wrong  My maternal grandmother had angina and valve issues  Her 3 brothers all had double bypasses  Could I have inherited this? I am not overweight at 63kg and 5 ft 9  I walk 20-25 miles a week at work and general walking here and there  I started HRT (patches evorol 25 -50) in July as menopause pain was making me feel like I was 90 and was getting me down 
I am worried so much now and analysing every ache/ twinge I get  I feel like a hypochondriac at the moment  I’m worried what will happen at the cardiologist and what the test will entail and tell me  I am waiting on cholesterol test which I had on 25/01/19  Can I have inverted T waves and be fine  Please help I am so scared and crying far too much 
Hello Colleen – the first thing is: please take a big deep breath before you read another word here! I’m not a physician so of course cannot comment on your specific case, but I can tell you generally that the definition of “angina” (as this glossary lists above) is “distressing symptoms”, typically chest pain that gets worse with exertion, and goes away with rest  That’s classic stable angina… typically caused by something that’s reducing blood flow to the heart muscle (causing the chest pain of angina) 
A family history that might make a difference for you personally is only in what’s called your ‘first degree’ relatives: for example, if your mother or sister were diagnosed with heart disease before age 65, or if your Dad or brother were diagnosed before age 55, then doctors would consider that you have a family history as a risk factor for heart disease  There’s little if any scientific evidence that a grandparent or uncle’s heart disease history has any effect on your own risk 
It is a very good thing that you’re having further tests and a referral to a cardiologist, if only to ease your mind  There are many reasons for inverted T-waves, ranging from cardiac issues to completely benign conditions  One way of looking at this is choosing to believe that seeing a cardiologist will ease your mind one way or the other – so this is something to look forward to, not dread  If the cardiologist spots something suspicious, a treatment plan will be created  If not, you can wave goodbye and go back to happily living your life 
Try thinking of this cardiology appointment just as you would if your car were making some frightening noises and you were bringing it to your mechanic for a check up  You could work yourself into a complete state worrying ahead of time if the car trouble is going to be serious, or you could look at this appointment as the solution – at last! – to figuring out what’s wrong so the mechanic can recommend the next step 
Thank you for this list of so many definitions provided in plain English  what a valuable resource this is  THANK YOU, I have been looking for translations FOR PATIENTS not med school graduates– like this for three years 
My family doctor had me wear a 24 hr EKG  After reading the results, she has scheduled a scope to look inside my heart by a specialist  Completely forgoing a stress test  Said I have major changes in the EKG, what type of changes could they be looking at? Had LAD STENT INSERTED 7 YRS AGO – WHAT COULD THEY BE LOOKING FOR?
This is a great wealth of information, Carolyn! I looked and did not see my diagnosis, which is aortic stenosis  I looked under aortic as well as stenosis  Did I just miss it somehow?
I learned some new information, I am a bit familiar now, but not when I had my MI, it was like learning a new language  But, my favorite part was seeing SCAD on this list! Thank you 
Thanks and welcome! I was thinking of editing that SCAD definition actually: I suspect that that it isn’t so much that SCAD is “rare”, but it’s more that it’s “rarely correctly diagnosed” 
I totally agree that SCAD is not as rare as I believed for many years  Once awareness is spread to all medical staff, I believe many lives will be saved  Hoping for a brighter future for all SCAD patients 
I hope so too, Cathy  Perhaps when more SCAD studies (like Mayo Clinic’s) are published and read by more and more MDs, it will no longer be “rarely correctly diagnosed” 
It’s great to see IST on here  I was diagnosed with it 9 years ago and the lack of awareness is frustrating 
What a great resource for heart patients and their families!
Thanks so much, Ashley  I recently updated my original 2011 list after the world-famous Cleveland Clinic tweeted their glossary recently and I noticed that their list had a few glaring omissions (like SCAD and Brugada Syndrome) so this made me wonder what my list might be missing, too  Let me know if there’s anything else you think should be included, okay?
How is your health these days? How are you feeling?
New for me too  I have just been diagnosed with A-HCM: Apical Hypertrophic Cardiomyopathy 
I’ll add that one to my list, Kathleen – thanks!
Just saw this, Carolyn, and you’ve compiled a great resource  One note on A-HCM: Present thinking is that it’s due to a genetic modification  Runs in families though sometimes occurs spontaneously  I have not as yet done genetic testing, though it’s been offered 
Thanks Kathleen – like many cardiac diagnoses, it sounds like a moving target… Good luck to you!
This list is great  I’ve just been diagnosed and am utterly overwhelmed  Even in the WomenHeart online support community, I often have no clue most days what others are talking about with all these initials about their heart tests and specific disease  This is VERY helpful, thank you SO MUCH  Love your website which has been a godsend since my diagnosis 



ground_truth: Implantable Cardioverter Defibrillator (ICD) is a surgically implanted electronic device to treat life-threatening heartbeat irregularities.

prompt_front: Now, answer the following question based on the text below, only give me the answer and do not output any other words.

Question: What are the three subsets into which the parameter space V is divided?

Read the following text and answer briefly.

Context 2: Paper Info

Title: An CUSUM Test with Observation-Adjusted Control Limits in Change Detection
Publish Date: March 9, 2023
Author List: Fuquan Tang (from Department of Statistics, Shanghai Jiao Tong University), Dong Han (from Department of Statistics, Shanghai Jiao Tong University)

Figure

exp{−cg(µ)(θ − x Hv (θ) + o(1))} for 1 ≤ k ≤ ac − 1, bc ≤ n ≤ m, where Zi = −g ′ (µ)(Z i − µ)/a and Hv (θ) = ln hv (θ) + ( ac k − 1) ln ĥv (θ), ĥv (θ) = E v (e θ Zi ) 
i < cg(µ)(1 + o(1))) exp{−cg(µ)θ * v (1 + o(1))} (A  5) for ac ≤ k ≤ bc − 1, bc ≤ n ≤ m,andP v (
i + g ′ (µ)a −1 Tc(g)−1 i=Tc(g)−ac (Z i − µ)] −→ µas c → ∞ By the uniform integrability of {T c (g)/c} and using Theorem A 1 1 in Gut's book(1988), we haveE v (T c (g)) = (1 + o(1)) cg(µ) µfor a large c This completes the proof of Theorem 2 Proof of Theorem 4  Since g(x) < 0 for x > a * , a * ≤ µ * and µ * ≥ 0, it follows thatP v m Ẑm < cg( Ẑm ), Ẑm > a * ≤ P v ( Ẑm < µ * )andP v (T c (g) > m) = P v n i=n−k+1 Z i < cg( Ẑn ), 1 ≤ k ≤ n, 1 ≤ n ≤ m ≤ P v m Ẑm < cg( Ẑm ) = P v m Ẑm < cg( Ẑm ), Ẑm ≤ a * + P v m Ẑm < cg( Ẑm ), Ẑm > a * ≤ 2P v ( Ẑm < µ * ) Furthermore,P v ( Ẑm < µ * ) = P v ( m i −Z i > −mµ * ) = P v ( m i (µ − Z i ) > m(µ − µ * )) = P v (e θ m i (µ−Z i ) > e θm(µ−µ * ) ) ≤ e −m[θ(µ−µ * )−ln M (θ)] ,whereM(θ) = E v (e θ(µ−Z 1 )) and the last inequality follows from Chebychev's inequality Note thath(θ) = θ(µ − µ * ) − ln M(θ) attains its maximum value h(θ * ) = θ * (µ − µ * ) − ln M(θ * ) > 0 at θ = θ * > 0, where h ′ (θ * ) = 0  So, E v (T c (g)) = 1 + ∞ m=1 P v (T c (g) > m) ≤ 1 + m=1 −m[θ * (µ−µ * )−ln M (θ * )] = e θ * (µ−µ * )−ln M (θ * ) + 1 e θ * (µ−µ * )−ln M (θ * ) − Let k > 1 It follows that E vk (T c (g) − k + 1) + = ∞ m=1 P vk (T c (g) > m + k − 1, T c (g) > k − 1) ≤ (a 0 + 1)(k − 1)P 0 (T c (g) > k − 1) + ∞ m≥(a 0 +1)(k−1) P vk (T c (g) > m + k − 1) Similarly, we haveP vk (T c (g) > m + k − 1) = P vk n i=n−k+1 Z i < cg( Ẑn ), 1 ≤ k ≤ n, 1 ≤ n ≤ m + k − 1 ≤ 2P vk ( Ẑm+k−1 < µ * ) − Z i ) > m(µ − µ * ) + (k − 1)(µ 0 − µ * ) ≤ 2 exp{−m θ * (µ − µ * ) − ln M(θ * ) + k − 1 m [µ 0 − µ * − ln M 0 (θ * )] } ≤ e −mb for m ≥ (a 0 + 1)(k − 1), since θ * (µ − µ * ) − ln M(θ * ) + k − 1 m [µ 0 − µ * − ln M 0 (θ * )] ≥ b for m ≥ (a 0 + 1)(k−1) Thus, E vk (T c (g) − k + 1) + ≤ (a 0 + 1)(k − 1)P 0 (T c (g) ≥ k) + m≥(a 0 +1)(k−1) e −mb ≤ (a 0 + 1)(k − 1)P 0 (T c (g) >≥ k) + 2e −(a 0 +1)(k−1)b 1 − e −b  
Simulation of E τ i ,v and J ACE for detecting two mean shifts v = 0 1, v = 1 The parameters for T * M are k1=1, k2=150, r 1 = 5 2 * 10 −5 , r 2 = 1 1 * 10 −5 , and the expectation and standard deviation in both cases are 1717 06with 13459 80 and 3918 33 with 16893 25,respectively 

abstract

In this paper, we not only propose an new optimal sequential test of sum of logarithmic likelihood ratio (SLR) but also present the CUSUM sequential test (control chart, stopping time) with the observation-adjusted control limits (CUSUM-OAL) for monitoring quickly and adaptively the change in distribution of a sequential observations 
Two limiting relationships between the optimal test and a series of the CUSUM-OAL tests are established  Moreover, we give the estimation of the in-control and the out-of-control average run lengths (ARLs) of the CUSUM-OAL test  The theoretical results are illustrated by numerical simulations in detecting mean shifts of the observations sequence 

INTRODUCTION

In order to quickly detect a change in distribution of observations sequence without exceeding a certain false alarm rate, a great variety of sequential tests have been proposed, developed and applied to various fields since proposed a control chart method, see, for example, , , One of popular used sequential tests is the following upper-sided CUSUM test which was proposed by  
where c > 0 is a constant control limit, Z i = log[p v 1 (X i )/p v 0 (X i )], p v 0 (x) and p v 1 (x) are prechange and post-change probability density functions respectively for a sequence of mutually independent observations {X i , i ≥ 1}, that is, there is a unknown change-point τ ≥ 1 such that X 1 ,    , X τ −1 have the probability density function p v 0 , whereas, X τ , X τ +1 ,     have the probability density function p v 1  
By the renewal property of the CUSUM test T C we have , where E 1 (T C ) is the out-of-control average run length (ARL 1 ), P k and E k denote the probability and expectation respectively when the change from p v 0 to p v 1 occurs at the change-point τ = k for k ≥ 1  Though we know that the CUSUM test is optimal under Lorden's measure (see Moustakides 1986 and Ritov 1990), the out-of-control ARL 1 of the CUSUM test is not small, especially in detecting small mean shifts ( see Table in Section 4) 
In other words, the CUSUM test is insensitive in detecting small mean shifts  Then, how to increase the sensitivity of the CUSUM test ? Note that the control limit in the CUSUM test is a constant c which does not depend on the observation samples  Intuitively, if the control limit of the CUSUM test can become low as the samples mean of the observation sequence increases, then the alarm time of detecting the increasing mean shifts will be greatly shortened 
Based on this idea, by selecting a decreasing function g(x) we may define the ( upper-sided ) CUSUM chart T C (cg) with the observation-adjusted control limits cg( Ẑn ) ( abbreviated to the CUSUM-OAL chart ) in the following where c > 0 is a constant and Ẑn = n i=1 Z i /n  In other words, the control limits cg( Ẑn ) of the CUSUM-OAL test can be adjusted adaptively according to the observation information { Ẑn } 
Note that the control limits cg( Ẑn ) may be negative  In the special case, the CUSUM-OAL chart T C (cg) becomes into the conventional CUSUM chart T C (c) in (1) when g ≡ 1  Similarly, we can define a down-sided CUSUM-OAL test  In this paper, we consider only the upper-sided CUSUM-OAL test since the properties of the down-sided CUSUM-OAL test can be obtained by the similar method 
The main purpose of the present paper is to show the good detection performance of the CUSUM-OAL test and to give the estimation of its the in-control and out-of-control ARLs  The paper is organized as follows  In Section 2, we first present an optimal SLR sequential test, then define two sequences of the CUSUM-OAL tests and prove that one of the two sequences of CUSUM-OAL tests converges to the optimal test, another sequences of CUSUM-OAL tests converges to a combination of the optimal test and the CUSUM test 
The estimation of the in-control and out-of-control ARLs of the CUSUM-OAL tests and their comparison are given in Section 3  The detection performances of the three CUSUM-OAL tests and the conventional CUSUM test are illustrated in Section 4 by comparing their numerical out-ofcontrol ARLs  Section 5 provides some concluding remarks 
Proofs of the theorems are given in the Appendix 

AN OPTIMAL SLR TEST, TWO CUSUM-OAL TESTS AND THEIR LIMITING RELATIONSHIPS

Let P 0 and E 0 denote the probability and the expectation respectively with the probability density p v 0 when there is no change for all the time  It is known that It follows from Proposition 2 38 in and (5 8)-(5 9) in Chow et al, P 108) that the following sequence test of sum of logarithmic likelihood ratio (SLR)
for B > 1, is optimal in the following sense min for P 0 (T SLR < ∞) = α, where c = log B and 0 < α < 1  In particular, if P 0 is the standard normal distribution with mean shift µ > 0 after changepoint, we have Z j − µ 0 = µX j , where µ 0 = −µ 2 /2  It follows from proposition 4 in that the SLR test T SLR in (4) is also optimal (minimal ARL 1 ) with the same false alarm probability P 0 (T < τ ) 
It can be seen that the in-control average run length of T SLR is infinite, that is, ARL 0 = E 0 (T SLR ) = ∞  However, the minimal ARL 1 with finite ARL 0 is a widely used optimality criterion in statistical quality control (see ) and detection of abrupt changes (see   In order to get finite ARL 0 for T SLR , we replace the constant control limit c of T SLR in (3) or (4) with the dynamic control limit n(µ 0 − r) and obtain a modified SLR test T SLR (r) in the following
for r ≥ 0  For comparison, the in-control ARL 0 of all candidate sequential tests are constrained to be equal to the same desired level of type I error, the test with the lowest out-of-control ARL v has the highest power or the fastest monitoring (detection) speed  In the following example 1, the numerical simulations of the out-of-control ARLs of the CUSUM-OAL tests T C (cg u,0 ) in detecting the mean shifts of observations with normal distribution will be compared with that of the SLR tests T * (r) and T * (0), and that of the CUSUM-SLR test T C (c) ∧ T * (0) := min{T C (c), T * (0)} in the following Table  
These comparisons lead us to guess that there are some limiting relationships between T C (cg u,r ) and T * (r), and T C (c g u ) and T C (c) ∧ T * (0), respectively  Example 1  Let X 1 , X 2 ,      be mutually independent following the normal distribution N(0, 1) if there is no change  After the change-point τ = 1, the mean E µ (X k ) ( k ≥ 1 ) will change from v 0 = 0 to v = 0 1, 0 25, 0 5, 0 75, 1, 1 25, 1 5, 3  Here, we let
, where v 1 = 1 is a given reference value which for the CUSUM test is the magnitude of a shift in the process mean to be detected quickly  We conducted the numerical simulation based on 1,000,000 repetitions  The following Table lists the simulation results of the ARLs of the tests T C (c), T C (c g u ) for u = 1, 10, 10 2 , 10 3 , 10 4 , T * (0 0007), T C (c) ∧ T * (0) and T * (0) for detecting the mean shifts, where the mean shift 0 0 means that there is no change which corresponds to the in-control ARL 0 and all tests have the common ARL 0 ≈ 1000 except the test T * (0) which has ARL 0 = ∞ 
The values in the parameters are the standard deviations of the tests  From the last row in Table , it's a little surprising that though the ARL 0 of T * (0) is infinite, that is, E 0 (T * (0)) = ∞, the detection speed of T * (0) is faster than that of the CUSUM chart T C for all mean shifts, in particular, for detecting the small mean shift 0 1, the speed of T * (0) is only 7 47 which is very faster than the speed, 439, of the CUSUM test 
Moreover, both control charts T * (0 0007) and T C (11 9271) ∧ T * (0) not only have the nearly same detection performance as T * (0) but also can have the finite in-control ARL 0   Note particularly that when the number u in g u is taken from 0 to 1, 10, 10 2 , 10 3 , 10 4 , the detection speed of T C (c g u ) is getting faster and faster, approaching to that of T C (c) ∧ T * (0) 
This inspires us to prove the following theoretic results  Let τ = 1 and {X k , k ≥ 1} be an i i d  observations sequence with Theorem 2 shows that when the constant control limit c of the CUSUM test T C (c) is replaced with the observation-adjusted control limits {cg u,r ( Ẑn )} and {c g u ( Ẑn )} respectively, the corresponding two CUSUM-OAL tests {T C (cg u,r )} and {T C (c g u )} will converge to the optimal SLR test T * (r) and the CUSUM-SLR test T C (c) ∧ T * (0) as u → ∞, respectively 
In other words, the fastest alarm times that {T C (cg u,r )} and {T C (c g u )} can be reached are T * (r) and T C (c) ∧ T * (0), respectively  u ≥ 0} can be seen as two "long bridges" connecting T C (c) and T * (r), and T C (c) and T C (c) ∧ T * (0), respectively 

ESTIMATION AND COMPARISON OF ARL OF THE CUSUM-OAL TEST

In this section we will give an estimation of the ARLs of the following CUSUM-OAL test that can be written as where g( ) is a decreasing function, Ẑn (ac x] denotes the smallest integer greater than or equal to x  Here Ẑn (ac) is a sliding average of the statistics, Next we discuss on the the post-change probability distribution in order to estimate the ARLs of T C (cg) 
Usually we rarely know the post-change probability distribution P v of the observation process before it is detected  But the possible change domain and its boundary (including the size and form of the boundary) about v may be determined by engineering knowledge, practical experience or statistical data 
So we may assume that the region of parameter space V and a probability distribution Q on V are known  If we have no prior knowledge of the possible value of v after the change time τ , we may assume that v occurs equally on V , that is, the probability distribution Q is an equal probability distribution (or uniform distribution ) on V  
For example, let P v be the normal distribution and v = (µ, σ), where µ and σ denote the mean and standard deviation respectively, we can take the set V = {(µ, σ) : and Q is subject to the uniform distribution U(V ) on V if v occurs equally on V , where the numbers µ 1 , µ 2 , σ 1 and σ 2 are known  It means that we know the domain of the possible post-change distributions, P v , v ∈ V , i e , the boundary ∂V of the parameter space V is known 
Next we shall divide the parameter space V into three subsets V + , V 0 and V − by the Kullback-Leibler information distance  Let and are two Kullblak-Leibler information distances between P v , P v 0 and P v , P v 1   Since I(p|q) = 0 if and only if p = q, where p and q are two probability measures, it follows that
, it means that P v is closer to P v 0 than to P v 1 according to the Kullblak-Leibler information distance  There is a similar explanation for v ∈ V + or ∈ V 0   Suppose the post-change distribution P v and the function g(x) satisfy the following conditions: (I) The probability P v is not a point mass at E v (Z 1 ) and P v (Z 1 > 0) > 0 
(II) The moment-generating function h v (θ) = E v (e θZ 1 ) satisfies h v (θ) < ∞ for some θ > 0  (III) The function g(x) is decreasing, its second order derivative function g ′′ (x) is continuous and bounded, and there is a positive number x * such that g(x * ) = 0  ) and and therefore, Θ ′ (θ(u)) = −H(θ(u)) = −H(θ * v ) = 0, Θ ′ (θ(1/x)) > 0 for x > 1/u and Θ ′ (θ(1/x)) < 0 for x > 1/u 
Hence, there exists a positive number b defined in (??)  It can be seen, the main part of ARL v (T c (g)) will be an exponential function, square function, and linear function of c when the process {Z k : k ≥ 0} has no change or a "small change", a "medium change" and a "large change" from P v 0 to P v , respectively 
Here, the "small change" (v ∈ V − ) means that P v is closer to P v 0 than to P v 1 , i e , I(P v |P v 0 ) < I(P v |P v 1 ), and the "large change" is just the opposite  The "medium change" (v ∈ V 0 ) corresponds to In this paper, we will use another method to prove Theorem 3 since Wald's identity and the martingale method do not hold or can not work for showing the ARLs estimation of the test T c (g) when g is not constant 
Next we compare the detection performance of the CUSUM-OAL test (ARL v (T c ′ (g))) with that of the CUSUM test (ARL v (T C (c))) by using (??) in Theorem 4 1  ) when µ 0 < µ < 0 and for θ * v 0 > g(µ)/g(µ 0 ) when µ ≥ 0  This means that ARL v (T c (g)) can be smaller than ARL v (T C (c)) as long as g(µ)/g(µ 0 ) is small for all µ > µ 0  

NUMERICAL SIMULATION AND A REAL EX-AMPLE ILLUSTRATION

4 1 Numerical Simulation of ARLs for τ ≥ 1 By the simulation results of ARLs in Table , we see that the detection performance of T * (r), T C (c)∧T * (0), T * (0) and T C (c g u ) for large u is much better than that of the conventional CUSUM test T C for τ = 1  The following Table illustrates the simulation values of E τ i ,v and J ACE of nine tests in detecting two mean shifts v = 0 1 and v = 1 after six change-points, τ i , 1 ≤ i ≤ 6 with ARL 0 (T ) = E 0 (T ) ≈ 500 
Note that H v (θ) is a convex function and H ′ v (0) = µ < 0  This means that there is a unique positive number   It follows from (A 9) that for a large c  Taking θ ց θ * v and u ′ ց u, we have for a large c  Thus, by (A 11) we have as c → ∞  By the properties of exponential distribution, we have for a large c 
To prove the downward inequality of (A 10), let where b is defined in (??) and without loss of generality, we assume that b > a  Obviously, Let k = xcg(µ)  By Chebyshev's inequality, we have Since Hv (θ) and H v (θ) are two convex functions and Let m = tcg(µ)θ * v /bc for t > 0  By (A 13), (A 14), (A 15) and Theorem 5 1 in Esary, Proschan and Walkup (1967) we have
Finally, as c → +∞, where θ 0 > 0 satisfies h v (θ 0 ) = 1  Thus as c → ∞  This implies that for a large c  This completes the proof of (A 10)  Let v ∈ V 0   Let m 1 = (cg(0)) 2 /σ 2   It follows that Note that for a large c, where A = |g ′ (0)|/a, and , where Φ( ) is the standard normal distribution  Let m 2 = (cg(0)) 2 /(8σ 2 ln c) 
Note that as c → ∞, where the third inequality comes from Theorem 5 1 in Esary, Proschan and Walkup (1967)  Thus, we have Let v ∈ V + and let The uniform integrability of {T c (g)/c} for c ≥ 1, follows from the well-known uniform integrability of {T 0 /c} (see Gut (1988)) 



ground_truth: The three subsets are V+, V0, and V-, determined by the Kullback-Leibler information distance.

prompt_front: Now, answer the following question based on the text below, only give me the answer and do not output any other words.

Question: What was the Buckeyes' record in their first game of the season?

Read the following text and answer briefly.

Context 3: The 1951 Ohio State Buckeyes baseball team represented the Ohio State University in the 1951 NCAA baseball season  The head coach was Marty Karow, serving his 1st year 

The Buckeyes lost in the College World Series, defeated by the Texas A&M Aggies 

Roster

Schedule 

! style="" | Regular Season
|- valign="top" 

|- align="center" bgcolor="#ccffcc"
| 1 || March 16 || at  || Unknown • San Antonio, Texas || 15–3 || 1–0 || 0–0
|- align="center" bgcolor="#ffcccc"
| 2 || March 17 || at B  A  M  C  || Unknown • San Antonio, Texas || 7–8 || 1–1 || 0–0
|- align="center" bgcolor="#ffcccc"
| 3 || March 19 || at  || Clark Field • Austin, Texas || 0–8 || 1–2 || 0–0
|- align="center" bgcolor="#ffcccc"
| 4 || March 20 || at Texas || Clark Field • Austin, Texas || 3–4 || 1–3 || 0–0
|- align="center" bgcolor="#ccffcc"
| 5 || March 21 || at  || Unknown • Houston, Texas || 14–6 || 2–3 || 0–0
|- align="center" bgcolor="#ffcccc"
| 6 || March 22 || at Rice || Unknown • Houston, Texas || 2–3 || 2–4 || 0–0
|- align="center" bgcolor="#ccffcc"
| 7 || March 23 || at  || Unknown • Fort Worth, Texas || 4–2 || 3–4 || 0–0
|- align="center" bgcolor="#ccffcc"
| 8 || March 24 || at TCU || Unknown • Fort Worth, Texas || 7–3 || 4–4 || 0–0
|- align="center" bgcolor="#ccffcc"
| 9 || March 24 || at  || Unknown • St  Louis, Missouri || 10–4 || 5–4 || 0–0
|-

|- align="center" bgcolor="#ccffcc"
| 10 || April 6 ||  || Varsity Diamond • Columbus, Ohio || 2–0 || 6–4 || 0–0
|- align="center" bgcolor="#ccffcc"
| 11 || April 7 ||  || Varsity Diamond • Columbus, Ohio || 15–1 || 7–4 || 0–0
|- align="center" bgcolor="#ffcccc"
| 12 || April 14 ||  || Varsity Diamond • Columbus, Ohio || 0–1 || 7–5 || 0–0
|- align="center" bgcolor="#ccffcc"
| 13 || April 20 ||  || Varsity Diamond • Columbus, Ohio || 10–9 || 8–5 || 1–0
|- align="center" bgcolor="#ccffcc"
| 14 || April 21 || Minnesota || Varsity Diamond • Columbus, Ohio || 7–0 || 9–5 || 2–0
|- align="center" bgcolor="#ffcccc"
| 15 || April 24 || at  || Unknown • Oxford, Ohio || 3–4 || 9–6 || 2–0
|- align="center" bgcolor="#ffcccc"
| 16 || April 27 || at  || Hyames Field • Kalamazoo, Michigan || 2–3 || 9–7 || 2–0
|- align="center" bgcolor="#ffcccc"
| 17 || April 28 || at Western Michigan || Hyames Field • Kalamazoo, Michigan || 5–7 || 9–8 || 2–0
|-

|- align="center" bgcolor="#ccffcc"
| 18 || May 1 || at  || Unknown • Athens, Ohio || 7–6 || 10–8 || 2–0
|- align="center" bgcolor="#ccffcc"
| 19 || May 4 ||  || Varsity Diamond • Columbus, Ohio || 12–6 || 11–8 || 3–0
|- align="center" bgcolor="#ccffcc"
| 20 || May 5 || Purdue || Varsity Diamond • Columbus, Ohio || 14–4 || 12–8 || 4–0
|- align="center" bgcolor="#ffcccc"
| 21 || May 8 ||  || Varsity Diamond • Columbus, Ohio || 6–8 || 12–9 || 4–0
|- align="center" bgcolor="#ccffcc"
| 22 || May 9 || at Dayton || Unknown • Dayton, Ohio || 11–2 || 13–9 || 4–0
|- align="center" bgcolor="#ccffcc"
| 23 || May 12 ||  || Varsity Diamond • Columbus, Ohio || 6–5 || 14–9 || 5–0
|- align="center" bgcolor="#ccffcc"
| 24 || May 12 || Indiana || Varsity Diamond • Columbus, Ohio || 5–2 || 15–9 || 6–0
|- align="center" bgcolor="#ccffcc"
| 25 || May 15 || Ohio || Varsity Diamond • Columbus, Ohio || 6–0 || 16–9 || 6–0
|- align="center" bgcolor="#ffcccc"
| 26 || May 18 || at  || Northwestern Park • Evanston, Illinois || 1–3 || 16–10 || 6–1
|- align="center" bgcolor="#ccffcc"
| 27 || May 19 || at Northwestern || Northwestern Park • Evanston, Illinois || 10–3 || 17–10 || 7–1
|- align="center" bgcolor="#ccffcc"
| 28 || May 22 || at Cincinnati || Carson Field • Cincinnati, Ohio || 8–4 || 18–10 || 7–1
|- align="center" bgcolor="#ccffcc"
| 29 || May 25 ||  || Varsity Diamond • Columbus, Ohio || 4–1 || 19–10 || 8–1
|- align="center" bgcolor="#ffcccc"
| 30 || May 25 || Michigan || Varsity Diamond • Columbus, Ohio || 3–6 || 19–11 || 8–2
|- align="center" bgcolor="#ffcccc"
| 31 || May 30 || Miami (OH) || Varsity Diamond • Columbus, Ohio || 3–4 || 19–12 || 8–2
|-

|- align="center" bgcolor="#ccffcc"
| 32 || June 1 || at  || Old College Field • East Lansing, Michigan || 8–0 || 20–12 || 9–2
|- align="center" bgcolor="#ccffcc"
| 33 || June 2 || at Michigan State || Old College Field • East Lansing, Michigan || 9–8 || 21–12 || 10–2
|-

|-
|-
! style="" | Postseason
|- valign="top"

|- align="center" bgcolor="#ccffcc"
| 34 || June 8 || Western Michigan || Varsity Diamond • Columbus, Ohio || 1–0 || 22–12 || 10–2
|- align="center" bgcolor="#ffcccc"
| 35 || June 8 || Western Michigan || Varsity Diamond • Columbus, Ohio || 2–4 || 22–13 || 10–2
|- align="center" bgcolor="#ccffcc"
| 36 || June 9 || Western Michigan || Varsity Diamond • Columbus, Ohio || 3–2 || 23–13 || 10–2
|-

|- align="center" bgcolor="#ffcccc"
| 37 || June 13 || Oklahoma || Omaha Municipal Stadium • Omaha, Nebraska || 8–9 || 23–14 || 10–2
|- align="center" bgcolor="#ffcccc"
| 38 || June 13 || Texas A&M || Omaha Municipal Stadium • Omaha, Nebraska || 2–3 || 23–15 || 10–2
|-

Awards and honors 
Dick Hauck
 First Team All-Big Ten

Stewart Hein
 First Team All-Big Ten

References 

Ohio State Buckeyes baseball seasons
Ohio State Buckeyes baseball
Big Ten Conference baseball champion seasons
Ohio State
College World Series seasons



ground_truth: They won their first game with a score of 15-3.