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 
Context 2: Paper Info

Title: On the Role of Emergent Communication for Social Learning in Multi-Agent Reinforcement Learning
Publish Date: Unkown
Author List: Seth Karten, Siva Kailas, Huao Li, Katia Sycara

Figure

Figure1 By using contrastive learning, our method seeks similar representations between the state-message pair and future states while creating dissimilar representations with random states Thus satisfying the utility objective of the information bottleneck The depicted agents are blind and cannot see other cars 
Figure 2 An example of two possible classes, person and horse, from a single observation in the Pascal VOC game 
Figure 3  Blind Traffic Junction Left: Our method uses compositional complexity and contrastive utility to outperform other baselines in terms of performance and sample complexity The legend provides the mean ± variance of the best performance Right: Top: success, contrastive, and complexity losses for our method Right, Bottom: success, autoencoder loss for ae-comm with supervised pretraining 
Figure 4  Pascal VOC Game Representing compositional concepts from raw pixel data in images to communicate multiple concepts within a single image Our method significantly outperforms ae-comm and no-comm due to our framework being able to learn composable, independent concepts 
Figure 5  Blind Traffic Junction Social shadowing enables significantly lower sample complexity when compared to traditional online MARL 
Beta ablation: Messages are naturally sparse in bits due to the complexity loss Redundancy measures the capacity for a bijection between the size of the set of unique tokens and the enumerated observations and intents Min redundancy is 1 0 (a bijection) Lower is better 

abstract

Explicit communication among humans is key to coordinating and learning  Social learning, which uses cues from experts, can greatly benefit from the usage of explicit communication to align heterogeneous policies, reduce sample complexity, and solve partially observable tasks  Emergent communication, a type of explicit communication, studies the creation of an artificial language to encode a high task-utility message directly from data 
However, in most cases, emergent communication sends insufficiently compressed messages with little or null information, which also may not be understandable to a third-party listener  This paper proposes an unsupervised method based on the information bottleneck to capture both referential complexity and task-specific utility to adequately explore sparse social communication scenarios in multi-agent reinforcement learning (MARL) 
We show that our model is able to i) develop a natural-language-inspired lexicon of messages that is independently composed of a set of emergent concepts, which span the observations and intents with minimal bits, ii) develop communication to align the action policies of heterogeneous agents with dissimilar feature models, and iii) learn a communication policy from watching an expert's action policy, which we term 'social shadowing' 

INTRODUCTION

Social learning agents analyze cues from direct observation of other agents (novice or expert) in the same environment to learn an action policy from others  However, observing expert actions may not be sufficient to coordinate with other agents  Rather, by learning to communicate, agents can better model the intent of other agents, leading to better coordination 
In humans, explicit communication for coordination assumes a common communication substrate to convey abstract concepts and beliefs directly , which may not be available for new partners  To align complex beliefs, heterogeneous agents must learn a message policy that translates from one theory of mind to another to synchronize coordination 
Especially when there is complex information to process and share, new agent partners need to learn to communicate to work with other agents  Emergent communication studies the creation of artificial language  Often phrased as a Lewis game, speakers and listeners learn a set of tokens to communicate complex observations  
However, in multi-agent reinforcement learning (MARL), agents suffer from partial observability and non-stationarity (due to unaligned value functions) , which aims to be solved with decentralized learning through communication  In the MARL setup, agents, as speakers and listeners, learn a set of tokens to communicate observations, intentions, coordination, or other experiences which help facilitate solving tasks  
Agents learn to communicate effectively through a backpropagation signal from their task performance   This has been found useful for applications in human-agent teaming , multirobot navigation , and coordination in complex games such as StarCraft II   Communication quality has been shown to have a strong relationship with task performance , leading to a multitude of work attempting to increase the representational capacity by decreasing the convergence rates  
Yet these methods still create degenerate communication protocols , which are uninterpretable due to joined concepts or null (lack of) information, which causes performance degradation  In this work, we investigate the challenges of learning a arXiv:2302 14276v1 LG] 28 Feb 2023 messaging lexicon to prepare emergent communication for social learning (EC4SL) scenarios 
We study the following hypotheses: H1) EC4SL will learn faster through structured concepts in messages leading to higher-quality solutions, H2) EC4SL aligns the policies of expert heterogeneous agents, and H3) EC4SL enables social shadowing, where an agent learns a communication policy while only observing an expert agent's action policy 
By learning a communication policy, the agent is encouraged to develop a more structured understanding of intent, leading to better coordination  The setting is very realistic among humans and many computer vision and RL frameworks may develop rich feature spaces for a specific solo task, but have not yet interacted with other agents, which may lead to failure without alignment 
We enable a compositional emergent communication paradigm, which exhibits clustering and informativeness properties  We show theoretically and through empirical results that compositional language enables independence properties among tokens with respect to referential information  Additionally, when combined with contrastive learning, our method outperforms competing methods that only ground communication on referential information 
We show that contrastive learning is an optimal critic for communication, reducing sample complexity for the unsupervised emergent communication objective  In addition to the more human-like format, compositional communication is able to create variable-length messages, meaning that we are not limited to sending insufficiently compressed messages with little information, increasing the quality of each communication 
In order to test our hypotheses, we show the utility of our method in multi-agent settings with a focus on teams of agents, high-dimensional pixel data, and expansions to heterogeneous teams of agents of varying skill levels  Social learning requires agents to explore to observe and learn from expert cues 
We interpolate between this form of social learning and imitation learning, which learns action policies directly from examples  We introduce a 'social shadowing' learning approach where we use first-person observations, rather than third-person observations, to encourage the novice to learn latently or conceptually how to communicate and develop an understanding of intent for better coordination 
The social shadowing episodes are alternated with traditional MARL during training  Contrastive learning, which works best with positive examples, is apt for social shadowing  Originally derived to enable lower complexity emergent lexicons, we find that the contrastive learning objective is apt for agents to develop internal models and relationships of the task through social shadowing 
The idea is to enable a shared emergent communication substrate (with minimal bandwidth) to enable future coordi-nation with novel partners  Our contributions are deriving an optimal critic for a communication policy and showing that the information bottleneck helps extend communication to social learning scenarios 
In real-world tasks such as autonomous driving or robotics, humans do not necessarily learn from scratch  Rather they explore with conceptually guided information from expert mentors  In particular, having structured emergent messages reduces sample complexity, and contrastive learning can help novice agents learn from experts 
Emergent communication can also align heterogeneous agents, a social task that has not been previously studied 

Multi-Agent Signaling

Implicit communication conveys information to other agents that is not intentionally communicated   Implicit signaling conveys information to other agents based on one's observable physical position   Implicit signaling may be a form of implicit communication such as through social cues or explicit communication such as encoded into the MDP through "cheap talk"  
Unlike implicit signaling, explicit signaling is a form of positive signaling that seeks to directly influence the behavior of other agents in the hopes that the new information will lead to active listening  Multi-agent emergent communication is a type of explicit signaling which deliberately shares information 
Symbolic communication, a subset of explicit communication, seeks to send a subset of pre-defined messages  However, these symbols must be defined by an expert and do not scale to particularly complex observations and a large number of agents  Emergent communication aims to directly influence other agents with a learned subset of information, which allows for scalability and interpretability by new agents 

Emergent Communication

Several methodologies currently exist to increase the informativeness of emergent communication  With discrete and clustered continuous communication, the number of observed distinct communication tokens is far below the number permissible   As an attempt to increase the emergent "vocabulary" and decrease the data required to converge to an informative communication "language", work has added a bias loss to emit distinct tokens in different situations  
More recent work has found that the sample efficiency can be further improved by grounding communication in observation space with a supervised reconstruction loss   Information-maximizing autoencoders aim to maximize the state reconstruction accuracy for each agent  How-ever, grounding communication in observations has been found to easily satisfy these input-based objectives while still requiring a myriad more samples to explore to find a task-specific communication space  
Thus, it is necessary to use task-specific information to communicate informatively  This will enable learned compression for task completion rather than pure compression for input recovery  Other work aims to use the information bottleneck to decrease the entropy of messages   In our work, we use contrastive learning to increase representation similarity with future goals, which we show optimally optimizes the Q-function for messages 

Natural Language Inspiration

The properties of the tokens in emergent communication directly affect their informative ability  As a baseline, continuous communication tokens can represent maximum information but lack human-interpretable properties  Discrete 1-hot (binary vector) tokens allow for a finite vocabulary, but each token contains the same magnitude of information, with equal orthogonal distance to each other token 
Similar to word embeddings in natural language, discrete prototypes are an effort to cluster similar information together from continuous vectors   Building on the continuous word embedding properties, VQ-VIB , an information-theoretic observation grounding based on VQ-VAE properties , uses variational properties to provide word embedding properties for continuous emergent tokens 
Like discrete prototypes, they exhibit a clustering property based on similar information but are more informative  However, each of these message types determines a single token for communication  Tokens are stringed together to create emergent "sentences" 

Preliminaries

We formulate our setup as a decentralized, partially observable Markov Decision Process with communication (Dec-POMDP-Comm)  Formally, our problem is defined by the tuple, S, A, M, T , R, O, Ω, γ   We define S as the set of states, A i , i ∈ [1, N ] as the set of actions, which includes task-specific actions, and M i as the set of communications for N agents 
T is the transition between states due to the multi-agent joint action space T : S × A 1 ,    , A N → S  Ω defines the set of observations in our partially observable setting  Partial observability requires communication to complete the tasks successfully  O i : M 1 ,    , M N × Ŝ → Ω maps the communications and local state, Ŝ, to a distribution of observations for each agent 
R defines the reward function and γ defines the discount factor 

Architecture

The policy network is defined by three stages: Observation Encoding, Communication, and Action Decoding  The best observation encoding and action decoding architecture is task-dependent, i e , using multi-layer perceptrons (MLPs), CNNs , GRUs , or transformer layers are best suited to different inputs 
The encoder transforms observation and any sequence or memory information into an encoding H  The on-policy reinforcement learning training uses RE-INFORCE or a decentralized version of MAPPO as specified by our experiments  Our work focuses on the communication stage, which can be divided into three substages: message encoding, message passing (often considered sparse communication), and message decoding 
We use the message passing from   For message decoding, we build on a multiheaded attention framework, which allows an agent to learn which messages are most important   Our compositional communication framework defines the message encoding, as described in section 4 

Objective

Mutual information, denoted as I(X; Y ), looks to measure the relationship between random variables, which is often measured through Kullback-Leibler divergence , I(X; Y ) = D KL (p(x, y)||p(x) ⊗ p(y))  The message encoding substage can be defined as an information bottleneck problem, which defines a tradeoff between the complexity of information (compression, I(X, X)) and the preserved relevant information (utility, I( X, Y )) 
The deep variational information bottleneck defines a trade-off between preserving useful information and compression   We assume that our observation and memory/sequence encoder provides an optimal representation H i suitable for sharing relevant observation and intent/coordination information  We hope to recover a representation Y i , which contains the sufficient desired outputs 
In our scenario, the information bottleneck is a trade-off between the complexity of information I(H i ; M i ) (representing the encoded information exactly) and representing the relevant information I(M j =i ; Y i ), which is signaled from our contrastive objective  In our setup, the relevant information flows from other agents through communication, signaling a combination of the information bottleneck and a Lewis game 
We additionally promote complexity through our compositional independence objective, This is formulated by the following Lagrangian, where the bounds on mutual information Î are defined in equations 1, 2, and 10  Overall, our objective is,

Complexity through Compositional Communication

We aim to satisfy the complexity objective, I(H i , M i ), through compositional communication  In order to induce complexity in our communication, we want the messages to be as non-random as possible  That is, informative with respect to the input hidden state h  In addition, we want each token within the message to share as little information as possible with the preceding tokens 
Thus, each additional token adds only informative content  Each token has a fixed length in bits W   The total sequence is limited by a fixed limit, L l W l ≤ S, of S bits and a total of L tokens  We use a variational message generation setup, which maps the encoded hidden state h to a message m; that is, we are modeling the posterior, π i m (m l |h) 
We limit the vocabulary size to K tokens, e j ∈ R D , j ∈ [1, K] ⊂ N, where each token has dimensionality D and l ∈ [1, L] ⊂ N  Each token m l is sampled from a categorical posterior distribution, 0 otherwise such that the message m l is mapped to the nearest neighbor e j   A set of these tokens makes a message m 
To satisfy the complexity objective, we want to use m i to well-represent h i and consist of independently informative m i l  

Independent Information

We derive an upper bound for the interaction information between all tokens  Proposition 4 1  For the interaction information between all tokens, the following upper bound holds: The proof is in Appendix A 1  Since we want the mutual information to be minimized in our objective, we minimize,

Input-Oriented Information

In order to induce complexity in the compositional messages, we additionally want to minimize the mutual information I(H; M ) between the composed message m and the encoded information h  We derive an upper bound on the mutual information that we use as a Lagrangian term to minimize  Proposition 4 2  For the mutual information between the composed message and encoded information, the following upper bound holds:
The proof is in Appendix A 1  Thus, we have our Lagrangian term, Conditioning on the input or observation data is a decentralized training objective 

Sequence Length

Compositional communication necessitates an adaptive limit on the total length of the sequence  Corollary 4 3  Repeat tokens, w, are redundant and can be removed  Suppose one predicts two arbitrary tokens, w k and w l   Given equation 1, it follows that there is low or near-zero mutual information between w k and w l  
A trivial issue is that the message generator will predict every available token as to follow the unique token objective  Since the tokens are imbued with input-oriented information (equation 2), the predicted tokens will be based on relevant referential details  Thus, it follows that tokens containing irrelevant information will not be chosen 
A nice optimization objective that follows from corollary 4 3 is that one can use self-supervised learning with an end-ofsequence (EOS) token to limit the variable total length of compositional message sequences  (3) Algorithm 1 Compositional Message Gen (h t ) m i ∼ N ( ĥ; µ, σ) 9: end for 10: return m

Message Generation Architecture

Now, we can define the pipeline for message generation  The idea is to create an architecture that can generate features to enable independent message tokens  We expand each compressed token into the space of the hidden state h (1-layer linear expansion) since each token has a natural embedding in R |h|  
Then, we perform attention using a softmin to help minimize similarity with previous tokens and sample the new token from a variational distribution  See algorithm 1 for complete details  During execution, we can generate messages directly due to equation 1, resolving any computation time lost from sequential compositional message generation 

Utility through Contrastive Learning

First, note that our Markov Network is as follows: H j → M j → Y i ← H i   Continue to denote i as the agent identification and j as the agent ID such that j = i  We aim to satisfy the utility objective of the information bottleneck, I(M j ; Y i ), through contrastive learning as shown in figure 1  Proposition 5 1 
Utility mutual information is lower bounded by the contrastive NCE-binary objective, The proof is in Appendix A 1  This result shows a need for gradient information to flow backward across agents along communication edge connections 

Experiments and Results

We condition on inputs, especially rich information (such as pixel data), and task-specific information  When evaluating an artificial language in MARL, we are interested in referential tasks, in which communication is required to complete the task  With regard to intent-grounded communication, we study ordinal tasks, which require coordination information between agents to complete successfully 
Thus, we consider tasks with a team of agents to foster messaging that communicates coordination information that also includes their observations  To test H1, structuring emergent messages enables lower complexity, we test our methodology and analyze the input-oriented information and utility capabilities 
Next, we analyze the ability of heterogeneous agents to understand differing communication policies (H2))  Finally, we consider the effect of social shadowing (H3), in which agents solely learn a communication policy from an expert agent's action policy  We additionally analyze the role of offline reinforcement learning for emergent communication in combination with online reinforcement learning to further learn emergent communication alongside an action policy 
We evaluate each scenario over 10 seeds 

Environments

Blind Traffic Junction We consider a benchmark that requires both referential and ordinal capabilities within a team of agents  The blind traffic junction environment requires multiple agents to navigate a junction without any observation of other agents  Rather, they only observe their own state location 
Ten agents must coordinate to traverse through the lanes without colliding into agents within their lane or in the junction



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 is the main methodology used in the research?

Read the following text and answer briefly.

Context 2:  Our training uses REINFORCE   Pascal VOC Game We further evaluate the complexity of compositional communication with a Pascal VOC   This is a two-agent referential game similar to the Cifar game but requires the prediction of multiple classes 
During each episode, each agent observes a random image from the Pascal VOC dataset containing exactly two unique labels  Each agent must encode information given only the raw pixels from the original image such that the other agent can recognize the two class labels in the original image  An agent receives a reward of 0 25 per correctly chosen class label and will receive a total reward of 1 if both agents guess all labels correctly 
See figure 2  Our training uses heterogeneous agents trained with PPO (modified from MAPPO repository)  For simplicity of setup, we consider images with exactly two unique labels from a closed subset of size five labels of the original set of labels from the Pascal VOC data  Furthermore, these images must be of size 375 × 500 pixels 
Thus, the resultant dataset comprised 534 unique images from the Pascal VOC dataset 

Baselines

To evaluate our methodology, we compare our method to the following baselines: (1) no-comm, where agents do not communicate; (2) rl-comm, which uses a baseline communication method learned solely through policy loss ; (3) ae-comm, which uses an autoencoder to ground communication in input observations ; (4) VQ-VIB, which uses a variational autoencoder to ground discrete communication in input observations and a mutual information objective to ensure low entropy communication  
We provide an ablation of the loss parameter β in table 1 in the blind traffic junction scenario  When β = 0, we use our compositional message paradigm without our derived loss terms  We find that higher complexity and independence losses increase sample complexity  When β = 1, the model was unable to converge 
However, when there is no regularization loss, the model performs worse (with no guarantees about referential representation)  We attribute this to the fact that our independence criteria learns a stronger causal relationship  There are fewer spurious features that may cause an agent to take an incorrect action 
In order to understand the effect of the independent concept representation, we analyze the emergent language's capacity for redundancy  A message token m l is redundant if there exists another token m k that represents the same information  With our methodology, the emergent 'language' converges to the exact number of observations and intents required to solve the task 
With a soft discrete threshold, the independent information loss naturally converges to a discrete number of tokens in the vocabulary  Our β ablation in table 1 yields a bijection between each token in the vocabulary and the possible emergent concepts, i e , the enumerated observations and intents  Thus for β = 0 1, there is no redundancy 
Sparse Communication In corollary 4 3, we assume that there is no mutual information between tokens  In practice, the loss may only be near-zero  Our empirical results yield independence loss around 1e − 4  In table 1, the size of the messages is automatically compressed to the smallest size to represent the information 
Despite a trivially small amount of mutual information between tokens, our compositional method is able to reduce the message size in bits by 2 3x using our derived regularization, for a total of an 8x reduction in message size over non-compositional methods such as ae-comm  Since the base unit for the token is a 32-bit float, we note that each token in the message may be further compressed 
We observe that each token uses three significant digits, which may further compress tokens to 10 bits each for a total message length of 20 bits 

Communication Utility Results

Due to coordination in MARL, grounding communication in referential features is not enough  Finding the communication utility requires grounding messages in ordinal information  Overall, figure shows that our compositional, contrastive method outperforms all methods focused on solely input-oriented communication grounding 
In the blind traffic junction, our method yields a higher average task success rate and is able to achieve it with a lower sample complexity  Training with the contrastive update tends to spike to high success but not converge, often many episodes before convergence, which leaves area for training improvement 
That is, the contrastive update begins to find aligned latent spaces early in training, but it cannot adapt the methodology quickly enough to converge  The exploratory randomness of most of the early online data prevents exploitation of the high utility f + examples  This leaves further room for improvement for an adaptive contrastive loss term 
Regularization loss convergence After convergence to high task performance, the autoencoder loss increases in order to represent the coordination information  This follows directly from the information bottleneck, where there exists a tradeoff between utility and complexity  However, communication, especially referential communication, should have an overlap between utility and complexity 
Thus, we should seek to make the complexity loss more convex  Our compositional communication complexity loss does not converge before task performance convergence  While the complexity loss tends to spike in the exploratory phase, the normalized value is very small  Interestingly, the method eventually converges as the complexity loss converges below a normal- ized 0 3 
Additionally, the contrastive loss tends to decrease monotonically and converges after the task performance converges, showing a very smooth decrease  The contrastive f − loss decreases during training, which may account for success spikes prior to convergence  The method is able to converge after only a moderate decrease in the f + loss 
This implies empirical evidence that the contrastive loss is an optimal critic for messaging  See figure 3 

Heterogeneous Alignment Through Communication

In order to test the heterogeneous alignment ability of our methodology to learn higher-order concepts from highdimensional data, we analyze the performance on the Pascal VOC game  We compare our methodology against ae-comm to show that concepts should consist of independent information directly from task signal rather than compression to reconstruct inputs 
That is, we show an empirical result on pixel data to verify the premise of the information bottleneck  Our methodology significantly outperforms the observation-grounded ae-comm baseline, as demonstrated by figure 4  The ae-comm methodology, despite using autoencoders to learn observation-grounded communication, performs only slightly better than no-comm 
On the other hand, our methodology is able to outperform both baselines significantly  It is important to note that based on figure 4, our methodology is able to guess more than two of the four labels correctly across the two agents involved, while the baseline methodologies struggle to guess exactly two of thew four labels consistently 
This can be attributed to our framework being able to learn compositional concepts that are much more easily discriminated due to mutual independence 

Social Shadowing

Critics of emergent communication may point to the increased sample complexity due to the dual communication and action policy learning  In the social shadowing scenario, heterogeneous agents can learn to generate a communication policy without learning the action policy of the watched expert agents  To enable social shadowing, the agent will alternate between a batch of traditional MARL (no expert) and (1st-person) shadowing an expert agent performing the task in its trajectory 
The agent only uses the contrastive objective to update its communication policy during shadowing  In figure , the agent that performs social shadowing is able to learn the action policy with almost half the sample complexity required by the online reinforcement learning agent  Our results show that the structured latent space of the emergent communication learns socially benevolent coordination 
This tests our hypothesis that by learning communication to understand the actions of other agents, one can enable lower sample complexity coordination  Thus, it mitigates the issues of solely observing actions 

Discussion

By using our framework to better understand the intent of others, agents can learn to communicate to align policies and coordinate  Any referential-based setup can be performed with a supervised loss, as indicated by the instant satisfaction of referential objectives  Even in the Pascal VOC game, which appears to be a purely referential objective, our results show that intelligent compression is not the only objective of referential communication 
The emergent communication paradigm must enable an easy-to-discriminate space for the game  In multi-agent settings, the harder challenge is to enable coordination through communication  Using contrastive communication as an optimal critic aims to satisfy this, and has shown solid improvements  Since contrastive learning benefits from good examples, this method is even more powerful when there is access to examples from expert agents 
In this setting, the communication may be bootstrapped, since our optimal critic has examples with strong signals from the 'social shadowing' episodes  Additionally, we show that the minimization of our independence objective enables tokens that contain minimal overlapping information with other tokens 
Preventing trivial communication paradigms enables higher performance  Each of these objectives is complementary, so they are not trivially minimized during training, which is a substantial advantage over comparative baselines  Unlike prior work, this enables the benefits of training with reinforcement learning in multi-agent settings 
In addition to lower sample complexity, the mutual information regularization yields additional benefits, such as small messages, which enables the compression aspect of sparse communication  From a qualitative point of view, the independent information also yields discrete emergent concepts, which can be further made human-interpretable by a post-hoc analysis  
This is a step towards white-box machine learning in multi-agent settings  The interpretability of this learned white-box method could be useful in human-agent teaming as indicated by prior work   The work here will enable further results in decision-making from high-dimensional data with emergent concepts 
The social scenarios described are a step towards enabling a zero-shot communication policy  This work will serve as future inspiration for using emergent communication to enable ad-hoc teaming with both agents and humans 

Appendix

A 1  Proofs Proposition 4 1 For the interaction information between all tokens, the following upper bound holds: Proof  Starting with the independent information objective, we want to minimize the interaction information, which defines the conditional mutual information between each token and, Let π i m (m l |h) be a variational approximation of p(m l |h), which is defined by our message encoder network 
Given that each token should provide unique information, we assume independence between m l   Thus, it follows that our compositional message is a vector, m = [m 1 ,       , m L ], and is jointly Gaussian  Moreover, we can define q( m|h) as a variational approximation to p(m|h) = p(m 1 ;       , m L |h) 
We can model q with a network layer and define its loss as || m − m|| 2   Thus, transforming equation 4 into variational form, we have, it follows that q( m|h) log q( m|h)d m ≥ q( m|h) log Thus, we can bound our interaction information, Proposition 4 2 For the mutual information between the composed message and encoded information, the following upper bound holds:
Proof  By definition of mutual information between the composed messages M and the encoded observations H, we have, Substituting q( m|h) for p( m|h), the same KL Divergence identity, and defining a Gaussian approximation z( m) of the marginal distribution p( m), it follows that, In expectation of equation 1, we have,
This implies that, for m = [m 1 ,       , m L ], there is probabilistic independence between m j , m k , j = k  Thus, expanding, it follows that, where z(m l ) is a standard Gaussian  Proposition 5 1  Utility mutual information is lower bounded by the contrastive NCE-binary objective, Proof  We suppress the reliance on h since this is directly passed through 
By definition of mutual information, we have, Our network model learns π R + (y|m) from rolled-out trajectories, R + , using our policy  The prior of our network state, π R − (y), can be modeled from rolling out a random trajectory, R−  Unfortunately, it is intractable to model π R + (y|m) and π R − (y) directly during iterative learning, but we can sample y + ∼ π R + (y|m) and y − ∼ π R − (y) directly from our network during training 
It has been shown that log p(y|m) provides a bound on mutual information , with the expectation over l p(m l , y l )  However, we need a tractable understanding of the information Y   In the information bottleneck, Y represents the desired outcome  In our setup, y is coordination information that helps create the desired output, such as any action a −  
This implies, y =⇒ a −   Since the transition is known, it follows that a − =⇒ s − f , a random future state  Thus, we have, π This is similar to the proof for lemma A 5, but requires assumptions on messages m from the emergent language  We note that when m is random, the case defaults to lemma A 5  Thus, we assume we have at least input-oriented information in m given sufficiently satisfying equation 2  Given a sufficient emergent language, it follows that y =⇒ a + , where a + is an intention action based on m 
Similarly, since the transition is known, a + =⇒ s + f , a desired goal state along the trajectory  Thus, we have, π R + (y|m) = p(s = s + f |y, m)  Recall the following (as shown in ), which we have adapted to our communication objective, Proposition A 3 (rewards → probabilities)  The Q-function for the goal-conditioned reward function r g (s t , m t ) = (1 − γ)p(s = s g |y t ) is equivalent to the probability of state s g under the discounted state occupancy measure:
and Lemma A 4  The critic function that optimizes equation 8 is a Q-function for the goal-conditioned reward function up to a multiplicative constant 1 The critic function f (s, m, s f ) = y enc(s f ) represents the similarity between the encoding y = enc(s, m) and the encoding of the future rollout s f  
Given lemmas A 5 A 6 A 8 and proposition A 7, it follows that equation 8 is the NCE-binary (InfoMAX ) objective, Î(M j , Y i ) = log σ(f (s, m, s + f )) + log 1 − σ(f (s, m, s − f )) which lower bounds the mutual information, I(M j , Y i ) ≥ Î(M j , Y i )  The critic function is unbounded, so we constrain it to [0, 1] with the sigmoid function, σ( * ) 
We suppress the reliance on h since this is directly passed through  By definition of mutual information, we have, Our network model learns π R + (y|m) from rolled-out trajectories, R + , using our policy  The prior of our network state, π R − (y), can be modeled from rolling out a random trajectory, R− 
Unfortunately, it is intractable to model π R + (y|m) and π R − (y) directly during iterative learning, but we can sample y + ∼ π R + (y|m) and y − ∼ π R − (y) directly from our network during training  It has been shown that log p(y|m) provides a bound on mutual information , with the expectation over l p(m l , y l ) 
However, we need a tractable understanding of the information Y   Lemma A 5  π R − (y) = p(s = s − f |y)  In the information bottleneck, Y represents the desired outcome  In our setup, y is coordination information that helps create the desired output, such as any action a −   This implies, y =⇒ a −   Since the transition is known, it follows that a − =⇒ s − f , a random future state 
Thus, we have, π R − (y) = p(s = s − f |y)  Lemma A 6  π R + (y|m) = p(s = s + f |y, m)  This is similar to the proof for lemma A 5, but requires assumptions on messages m from the emergent language  We note that when m is random, the case defaults to lemma A 5  Thus, we assume we have at least input-oriented information in m given sufficiently satisfying equation 2  Given a sufficient emergent language, it follows that y =⇒ a + , where a + is an intention action based on m 
Similarly, since the transition is known, a + =⇒ s + f , a desired goal state along the trajectory  Thus, we have, π R + (y|m) = p(s = s + f |y, m)  Recall the following (as shown in ), which we have adapted to our communication objective, Proposition A 7 (rewards → probabilities)  The Q-function for the goal-conditioned reward function r g (s t , m t ) = (1 − γ)p(s = s g |y t ) is equivalent to the probability of state s g under the discounted state occupancy measure:
and Lemma A 8  The critic function that optimizes equation 8 is a Q-function for the goal-conditioned reward function up to a multiplicative constant 1 p(s f ) : exp(f * (s, m, s f ) = 1 p(s f ) Q π s f (s, m)  The critic function f (s, m, s f ) = y enc(s f ) represents the similarity between the encoding y = enc(s, m) and the encoding of the future rollout s f  
Given lemmas A 5 A 6 A 8 and proposition A 7, it follows that equation 8 is the NCE-binary (InfoMAX ) objective, which lower bounds the mutual information, I(M j , Y i ) ≥ Î(M j , Y i )  The critic function is unbounded, so we constrain it to [0, 1] with the sigmoid function, σ( * ) 



ground_truth: An unsupervised method based on the information bottleneck and contrastive learning.

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: How many novels did Margaret Way write?

Read the following text and answer briefly.

Context 3: Margaret Way (b  Brisbane d  Cleveland, Queensland, Australia ) was an Australian writer of romance novels and women's fiction  A prolific author, Way wrote more than 120 novels since 1970, many through Mills & Boon, a romance imprint of British publisher Harlequin UK Ltd , owned by Harlequin Enterprises 

Biography
Before her marriage, she was a well-known pianist, teacher, vocal coach and accompanist  She began writing when her son, Laurence Way, was born, a friend took a pile of Mills & Boon books to her, she read all and decided that she also could write these types of novels  She began to write and promote her country with her stories set in Australia  She sold her first novels in 1970  Margaret Way lives with her family in her native Brisbane  Beginning in 2013, Margaret began to self-publish, releasing her first "e-book" mid-July 

Margaret died on the 10th of August 2022 in Cleveland, Queensland 

Bibliography

Single Novels
King Country (1970)
Blaze of Silk (1970)
The Time of the Jacaranda (1970)
Bauhinia Junction (1971)
Man from Bahl Bahla (1971)
Summer Magic (1971)
Return to Belle Amber (1971)
Ring of Jade (1972)
Copper Moon (1972)
Rainbow Bird (1972)
Man Like Daintree (1972)
Noonfire (1972)
Storm Over Mandargi (1973)
Wind River (1973)
Love Theme (1974)
McCabe's Kingdom (1974)
Sweet Sundown (1974)
Reeds of Honey (1975)
Storm Flower (1975)
Lesson in Loving (1975)
Flight into Yesterday (1976)
Red Cliffs of Malpara (1976)
Man on Half-moon (1976)
Swan's Reach (1976)
Mutiny in Paradise (1977)
One Way Ticket (1977)
Portrait of Jaime (1977)
Black Ingo (1977)
Awakening Flame (1978)
Wild Swan (1978)
Ring of Fire (1978)
Wake the Sleeping Tiger (1978)
Valley of the Moon (1979)
White Magnolia (1979)
Winds of Heaven (1979)
Blue Lotus (1979)
Butterfly and the Baron (1979)
Golden Puma (1980)
Temple of Fire (1980)
Lord of the High Valley (1980)
Flamingo Park (1980)
North of Capricorn (1981)
Season for Change (1981)
Shadow Dance (1981)
McIvor Affair (1981)
Home to Morning Star (1981)
Broken Rhapsody (1982)
The Silver Veil (1982)
Spellbound (1982)
Hunter's Moon (1982)
Girl at Cobalt Creek (1983)
No Alternative (1983)
House of Memories (1983)
Almost a Stranger (1984)
A place called Rambulara (1984)
Fallen Idol (1984)
Hunt the Sun (1985)
Eagle's Ridge (1985)
The Tiger's Cage (1986)
Innocent in Eden (1986)
Diamond Valley (1986)
Morning Glory (1988)
Devil Moon (1988)
Mowana Magic (1988)
Hungry Heart (1988)
Rise of an Eagle (1988)
One Fateful Summer (1993)
The Carradine Brand (1994)
Holding on to Alex (1997)
The Australian Heiress (1997)
Claiming His Child (1999)
The Cattleman's Bride (2000)
The Cattle Baron (2001)
The Husbands of the Outback (2001)
Secrets of the Outback (2002)
With This Ring (2003)
Innocent Mistress (2004)
Cattle Rancher, Convenient Wife (2007)
Outback Marriages (2007)
Promoted: Nanny to Wife (2007)
Cattle Rancher, Secret Son (2007)
Genni's Dilemma (2008)
Bride At Briar Ridge (2009)
Outback Heiress, Surprise Proposal (2009)
Cattle Baron, Nanny Needed (2009)

Legends of the Outback Series
Mail Order Marriage (1999)
The Bridesmaid's Wedding (2000)
The English Bride (2000)
A Wife at Kimbara (2000)

Koomera Crossing Series
Sarah's Baby (2003)
Runaway Wife (2003)
Outback Bridegroom (2003)
Outback Surrender (2003)
Home to Eden (2004)

McIvor Sisters Series
The Outback Engagement (2005)
Marriage at Murraree (2005)

Men Of The Outback Series
The Cattleman (2006)
The Cattle Baron's Bride (2006)
Her Outback Protector (2006)
The Horseman (2006)

Outback Marriages Series
Outback Man Seeks Wife (2007)
Cattle Rancher, Convenient Wife (2007)

Barons of the Outback Series Multi-Author
Wedding At Wangaree Valley (2008)
Bride At Briar's Ridge (2008)

Family Ties Multi-Author
Once Burned (1995)

Hitched! Multi-Author
A Faulkner Possession (1996)

Simply the Best Multi-Author
Georgia and the Tycoon (1997)

The Big Event Multi-Author
Beresford's Bride (1998)

Guardian Angels Multi-Author
Gabriel's Mission (1998)

Australians Series Multi-Author
7  Her Outback Man (1998)
17  Master of Maramba (2001)
19  Outback Fire (2001)
22  Mistaken Mistress (2002)
24  Outback Angel (2002)
33  The Australian Tycoon's Proposal (2004)
35  His Heiress Wife (2004)

Marrying the Boss Series Multi-Author
Boardroom Proposal (1999)

Contract Brides Series Multi-Author
Strategy for Marriage (2002)

Everlasting Love Series Multi-Author
Hidden Legacy (2008)

Diamond Brides Series Multi-Author
The Australian's Society Bride (2008)

Collections
Summer Magic / Ring of Jade / Noonfire (1981)
Wife at Kimbara / Bridesmaid's Wedding (2005)

Omnibus in Collaboration
Pretty Witch / Without Any Amazement / Storm Over Mandargi (1977) (with Lucy Gillen and Margaret Malcolm)
Dear Caliban / Heart of the Eagle / Swans' Reach (1978) (with Jane Donnelly and Elizabeth Graham)
The Bonds of Matrimony / Dragon Island / Reeds of Honey (1979) (with Elizabeth Hunter and Henrietta Reid)
The Man Outside / Castles in Spain / McCabe's Kingdom (1979) (with Jane Donnelly and Rebecca Stratton)
Winds From The Sea / Island of Darkness / Wind River (1979) (with Margaret Pargeter and Rebecca Stratton)
Moorland Magic / Tree of Idleness / Sweet Sundown (1980) (with Elizabeth Ashton and Elizabeth Hunter)
The Shifting Sands / Portrait of Jaime / Touched by Fire (1982) (with Jane Donnelly and Kay Thorpe)
Head of Chancery / Wild Heart / One-Way Ticket (1986) (with Betty Beaty and Doris Smith)
Heart of the Scorpion / The Winds of Heaven / Sweet Compulsion (1987) (with Janice Gray and Victoria Woolf)
One Brief Sweet Hour / Once More With Feeling / Blue Lotus (1990) (with Jane Arbor and Natalie Sparks)
Marry Me Cowboy (1995) (with Janet Dailey, Susan Fox and Anne McAllister)
Husbands on Horseback (1996) (with Diana Palmer)
Wedlocked (1999) (with Day Leclaire and Anne McAllister)
Mistletoe Magic (1999) (with Betty Neels and Rebecca Winters)
The Australians (2000) (with Helen Bianchin and Miranda Lee)
Weddings Down Under (2001) (with Helen Bianchin and Jessica Hart)
Outback Husbands (2002) (with Marion Lennox)
The Mother's Day Collection (2002) (with Helen Dickson and Kate Hoffmann)
Australian Nights (2003) (with Miranda Lee)
Outback Weddings (2003) (with Barbara Hannay)
Australian Playboys (2003) (with Helen Bianchin and Marion Lennox)
Australian Tycoons (2004) (with Emma Darcy and Marion Lennox)
A Mother's Day Gift (2004) (with Anne Ashley and Lucy Monroe)
White Wedding (2004) (with Judy Christenberry and Jessica Steele)
A Christmas Engagement (2004) (with Sara Craven and Jessica Matthews)
A Very Special Mother's Day (2005) (with Anne Herries)
All I Want for Christmas    (2005) (with Betty Neels and Jessica Steele)
The Mills and Boon Collection (2006) (with Caroline Anderson and Penny Jordan)
Outback Desire (2006) (with Emma Darcy and Carol Marinelli)
To Mum, with Love (2006) (with Rebecca Winters)
Australian Heroes (2007) (with Marion Lennox and Fiona McArthur)
Tall, Dark and Sexy (2008) (with Caroline Anderson and Helen Bianchin)
The Boss's Proposal (2008) (with Jessica Steele and Patricia Thayer)
Island Heat / Outback Man Seeks Wife / Prince's Forbidden Virgin / One Night Before Marriage / Their Lost-and-found Family / Single Dad's Marriage Wish (2008) (with Robyn Donald, Marion Lennox, Carol Marinelli, Sarah Mayberry and Anne Oliver)
Australian Billionaires (2009) (with Jennie Adams and Amy Andrews)
Cattle Baron : Nanny Needed / Bachelor Dad on Her Doorstep (2009) (with Michelle Douglas)

External links
Margaret Way at Harlequin Enterprises Ltd

Australian romantic fiction writers
Australian women novelists
Living people
Year of birth missing (living people)
Women romantic fiction writers



ground_truth: Margaret Way wrote more than 120 novels.