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A myocardial infarction (MI), commonly known as a heart attack, occurs when
blood flow Hemodynamics American and British English spelling differences#ae and oe, or haemodynamics are the Fluid dynamics, dynamics of blood flow. The circulatory system is controlled by homeostasis, homeostatic mechanisms of autoregulation, just as hydraul ...
decreases or stops to the
coronary artery The coronary arteries are the arterial blood vessels of coronary circulationCoronary () may, as shorthand in English, be used to mean: * Coronary circulation, the system of arteries and veins in mammals ** Coronary artery disease Coronary art ...
of the
heart The heart is a cardiac muscle, muscular Organ (biology), organ in most animals, which pumps blood through the blood vessels of the circulatory system. The pumped blood carries oxygen and nutrients to the body, while carrying metabolic waste ...

heart
, causing damage to the
heart muscle Cardiac muscle (also called heart muscle or myocardium) is one of three types of vertebrate Vertebrates () comprise all species of animal Animals (also called Metazoa) are multicellular eukaryotic organisms that form the Kingdom (biolo ...

heart muscle
. The most common symptom is
chest pain Chest pain is pain or discomfort in the chest, typically the front of the chest. It may be described as sharp, dull, pressure, heaviness or squeezing. Associated symptoms may include pain in the shoulder, arm, upper abdomen, or jaw, along with nau ...
or
discomfort Comfort (or being comfortable'')'' is a sense of physical or psychological ease, often characterized as a lack of hardship. Persons who are lacking in comfort are uncomfortable, or experiencing discomfort. A degree of psychological comfort c ...

discomfort
which may travel into the shoulder, arm, back, neck or jaw. Often it occurs in the center or left side of the chest and lasts for more than a few minutes. The discomfort may occasionally feel like
heartburn Heartburn, also known as pyrosis, cardialgia or acid indigestion, is a burning sensation in the central chest or upper central abdomen. The discomfort often rises in the chest and may radiate to the neck, throat, or angle of the arm. Heartbur ...
. Other symptoms may include
shortness of breath Shortness of breath (SOB), also known as dyspnea (BrE British English (BrE) is the standard dialect A standard language (also standard variety, standard dialect, and standard) is a language variety that has undergone substantial codificati ...
, nausea, feeling faint, a
cold sweat "Cold Sweat" is a song performed by James Brown and written with his bandleader Alfred "Pee Wee" Ellis. Brown recorded it in May 1967. An edited version of "Cold Sweat" released as a two-part single on King Records (USA), King Records was a No. 1 ...
or feeling tired. About 30% of people have atypical symptoms. Women more often present without chest pain and instead have neck pain, arm pain or feel tired. Among those over 75 years old, about 5% have had an MI with little or no history of symptoms. An MI may cause
heart failure Heart failure (HF), also known as congestive heart failure (CHF) and (congestive) cardiac failure (CCF), is a caused by the failure of the 's function as a pump supporting the ; its result from a structural and/or functional abnormality of the ...
, an
irregular heartbeat Arrhythmia, also known as cardiac arrhythmia or heart arrhythmia, is a group of conditions in which the heartbeat is irregular, too fast, or too slow. The heart rateHeart rate is the speed of the heartbeat measured by the number of contraction ...
,
cardiogenic shock Cardiogenic shock (CS) is a medical emergency resulting from inadequate blood flow due to the dysfunction of the ventricles of the heart.Textbooks of Internal MedicinHarrison's Principles of Internal Medicine 16th Edition, The McGraw-Hill McG ...
or
cardiac arrest Cardiac arrest is a sudden loss of Circulatory system, blood flow throughout the body resulting from the failure of the heart to pump effectively. It is a rapidly fatal medical emergency requiring immediate intervention with cardiopulmonary resus ...
. Most MIs occur due to
coronary artery disease Coronary artery disease (CAD), also called coronary heart disease (CHD), ischemic heart disease (IHD), or simply heart disease, involves the reduction of blood flow to the heart muscle Cardiac muscle (also called heart muscle or myocardium) is ...
. Risk factors include
high blood pressure Hypertension (HTN or HT), also known as high blood pressure (HBP), is a long-term Long-Term Capital Management L.P. (LTCM) was a hedge fund''A financial History of the United States Volume II: 1970–2001'', Jerry W. Markham, Chapter 5: "Bank ...

high blood pressure
,
smoking Smoking is a practice in which a substance is burned and the resulting smoke File:Wood Volatility Basis Dataset.jpg, Volatility distribution of volatile organic compound emissions in wood smoke. Smoke is a collection of airborne partic ...

smoking
,
diabetes Diabetes mellitus (DM), commonly known as diabetes, is a group of metabolic disorders characterized by a high blood sugar level over a prolonged period of time. Symptoms often include frequent urination, increased thirst and increased appeti ...
,
lack of exercise Increases in sedentary behaviors such as watching television are characteristic of a sedentary lifestyle A sedentary lifestyle is a type of lifestyle involving little or no physical activity Physical activity is defined as any voluntary bod ...
,
obesity Obesity is a medical condition A disease is a particular abnormal condition that negatively affects the structure or function of all or part of an organism, and that is not due to any immediate external injury. Diseases are often ...

obesity
, high blood cholesterol, poor diet and excessive alcohol intake. The complete blockage of a
coronary artery The coronary arteries are the arterial blood vessels of coronary circulationCoronary () may, as shorthand in English, be used to mean: * Coronary circulation, the system of arteries and veins in mammals ** Coronary artery disease Coronary art ...
caused by a rupture of an
atherosclerotic plaque An atheroma, or atheromatous plaque ("plaque"), is an abnormal accumulation of material in the inner layer of the wall of an artery An artery (plural arteries) () is a blood vessel that takes blood away from the heart to one or more parts of ...

atherosclerotic plaque
is usually the underlying mechanism of an MI. MIs are less commonly caused by
coronary artery spasmCoronary () may, as shorthand in English, be used to mean: * Coronary circulation, the system of arteries and veins in mammals ** Coronary artery disease Coronary artery disease (CAD), also called coronary heart disease (CHD), ischemic heart di ...
s, which may be due to
cocaine Cocaine (from , from , ultimately from : ''kúka'') is a and obtained primarily from the leaves of two coca species native to South America, ' and '. It is most commonly used as a and . After extraction from coca leaves and further proc ...

cocaine
, significant emotional stress (commonly known as Takotsubo syndrome or ''broken heart syndrome'') and extreme cold, among others. A number of tests are useful to help with diagnosis, including
electrocardiogram Electrocardiography is the process of producing an electrocardiogram (ECG or EKG). It is a graph of voltage Voltage, electric potential difference, electromotive force emf, electric pressure or electric tension is the difference in elec ...

electrocardiogram
s (ECGs), blood tests and
coronary angiography A coronary catheterization is a minimally invasive procedure to access the coronary circulation and blood filled chambers of the heart The heart is a muscle, muscular Organ (anatomy), organ in most animals, which pumps blood through the ...
. An ECG, which is a recording of the heart's electrical activity, may confirm an ST elevation MI (
STEMI A myocardial infarction (MI), commonly known as a heart attack, occurs when blood flow decreases or stops to a part of the heart The heart is a muscle, muscular Organ (anatomy), organ in most animals, which pumps blood through the blo ...
), if
ST elevation ST elevation refers to a finding on an electrocardiogram Electrocardiography is the process of producing an electrocardiogram (ECG or EKG). It is a graph of voltage Voltage, electric potential difference, electromotive force emf, elect ...
is present. Commonly used blood tests include
troponin image:Troponin Ribbon Diagram.png, 400px, Ribbon representation of the human cardiac troponin core complex (52 kDa core) in the calcium-saturated form. Blue = troponin C; green = troponin I; magenta = troponin T.; ; rendered with PyMOL Troponin, or ...
and less often creatine kinase MB. Treatment of an MI is time-critical.
Aspirin Aspirin, also known as acetylsalicylic acid (ASA), is a medication A medication (also called medicament, medicine, pharmaceutical drug, medicinal drug or simply drug) is a drug Uncoated tablets, consisting of about 90% acetylsalicy ...

Aspirin
is an appropriate immediate treatment for a suspected MI.
Nitroglycerin Nitroglycerin (NG), also known as nitroglycerine, trinitroglycerin (TNG), nitro, glyceryl trinitrate (GTN), or 1,2,3-trinitroxypropane, is a dense, colorless, oily, explosive An explosive (or explosive material) is a reactive substance that c ...
or
opioid Opioids are substances that act on opioid receptor Opioid receptors are a group of inhibitory G protein-coupled receptors with opioids as ligands. The endogenous opioids are dynorphins, enkephalins, endorphins, endomorphins and nocicepti ...
s may be used to help with chest pain; however, they do not improve overall outcomes.
Supplemental oxygen Oxygen therapy, also known as supplemental oxygen, is the use of oxygen as a medical therapy, medical treatment. This can include for Hypoxia (medical), low blood oxygen, carbon monoxide toxicity, cluster headaches, and to maintain enough oxygen w ...

Supplemental oxygen
is recommended in those with low oxygen levels or shortness of breath. In a STEMI, treatments attempt to restore blood flow to the heart and include
percutaneous coronary intervention Percutaneous coronary intervention (PCI) is a non-surgical procedure used to treat narrowing of the coronary arteries The coronary arteries are the arterial blood vessels of coronary circulation, which transport oxygenated blood to the heart m ...
(PCI), where the arteries are pushed open and may be
stent In medicine Medicine is the Art (skill), art, science, and Praxis (process) , practice of caring for a patient and managing the diagnosis, prognosis, Preventive medicine, prevention, therapy, treatment or Palliative care , palliation of their ...

stent
ed, or
thrombolysis Thrombolysis, also called fibrinolytic therapy, is the breakdown ( lysis) of blood clots formed in blood vessel The blood vessels are the components of the circulatory system that transport blood throughout the human body. These vessels trans ...
, where the blockage is removed using medications. People who have a non-ST elevation myocardial infarction (
NSTEMI A myocardial infarction (MI), commonly known as a heart attack, occurs when blood flow decreases or stops to a part of the heart The heart is a muscle, muscular Organ (anatomy), organ in most animals, which pumps blood through the blo ...
) are often managed with the blood thinner
heparin Heparin, also known as unfractionated heparin (UFH), is a medication and naturally occurring glycosaminoglycan . For polysaccharide nomenclature see here. R1, R2, R3 may have different values. Image:Hyaluronan.svg, 240px, Hyaluronic acid, Hyal ...

heparin
, with the additional use of PCI in those at high risk. In people with blockages of multiple coronary arteries and diabetes,
coronary artery bypass surgery Coronary artery bypass surgery, also known as coronary artery bypass graft (CABG, pronounced "cabbage") surgery, and colloquially heart bypass or bypass surgery, is a surgical procedure to reperfusion therapy, restore normal blood flow to an obs ...
(CABG) may be recommended rather than
angioplasty Angioplasty, also known as balloon angioplasty and percutaneous transluminal angioplasty (PTA), is a minimally invasive endovascular procedure used to widen narrowed or obstructed arteries or veins, typically to treat arterial atherosclerosis ...
. After an MI, lifestyle modifications, along with long-term treatment with aspirin,
beta blockers Beta blockers (beta-blockers, β-blockers, etc.) are a class of medications that are predominantly used to manage cardiac arrhythmia, abnormal heart rhythms, and to protect the heart from a second heart attack (myocardial infarction) after a firs ...
and
statin Statins, also known as HMG-CoA reductase inhibitors, are a of s that reduce and mortality in those who are at high risk of . They are the most common cholesterol-lowering drugs. (LDL) carriers of play a key role in the development of and ...

statin
s, are typically recommended. Worldwide, about 15.9 million myocardial infarctions occurred in 2015. More than 3 million people had an ST elevation MI, and more than 4 million had an NSTEMI. STEMIs occur about twice as often in men as women. About one million people have an MI each year in the United States. In the developed world, the risk of death in those who have had an STEMI is about 10%. Rates of MI for a given age have decreased globally between 1990 and 2010. In 2011, an MI was one of the top five most expensive conditions during inpatient hospitalizations in the US, with a cost of about $11.5 billion for 612,000 hospital stays.


Terminology

Myocardial infarction (MI) refers to tissue death (
infarction Infarction is tissue death ( necrosis) due to inadequate blood supply to the affected area. It may be caused by artery blockages, rupture, mechanical compression, or vasoconstriction. The resulting lesion A lesion is any damage or abnormal chan ...

infarction
) of the heart muscle (
myocardium Cardiac muscle (also called heart muscle or myocardium) is one of three types of vertebrate muscles, with the other two being skeletal muscle, skeletal and smooth muscle, smooth muscles. It is involuntary, striated muscle tissue, striated muscle t ...

myocardium
) caused by ischaemia, that is lack of oxygen delivery to myocardial tissue. It is a type of
acute coronary syndrome Acute coronary syndrome (ACS) is a syndrome (a set of signs and symptoms) due to decreased blood flow in the coronary arteries such that part of the heart muscle is unable to function properly or dies. The most common symptom is centrally l ...
, which describes a sudden or short-term change in symptoms related to blood flow to the heart. Unlike the other type of acute coronary syndrome,
unstable angina Unstable angina (UA), also called crescendo angina, is a type of angina pectoris Angina, also known as angina pectoris, is chest pain Chest pain is pain or discomfort in the chest, typically the front of the chest. It may be described as sharp ...
, a myocardial
infarction Infarction is tissue death ( necrosis) due to inadequate blood supply to the affected area. It may be caused by artery blockages, rupture, mechanical compression, or vasoconstriction. The resulting lesion A lesion is any damage or abnormal chan ...

infarction
occurs when there is cell death, this can be estimated by measuring by a
blood test A blood test is a laboratory A laboratory (; ; colloquially lab) is a facility that provides controlled conditions in which or technological research, s, and may be performed. Laboratory services are provided in a variety of settings: ...

blood test
for
biomarkers A biomarker, or biological marker is a measurable wikt:indicator, indicator of some biological state or condition. Biomarkers are often measured and evaluated using blood, urine, or soft tissues to examine normal biological processes, pathogenic pr ...
(the cardiac protein
troponin image:Troponin Ribbon Diagram.png, 400px, Ribbon representation of the human cardiac troponin core complex (52 kDa core) in the calcium-saturated form. Blue = troponin C; green = troponin I; magenta = troponin T.; ; rendered with PyMOL Troponin, or ...
). When there is evidence of an MI, it may be classified as an ST elevation myocardial infarction (STEMI) or Non-ST elevation myocardial infarction (NSTEMI) based on the results of an
ECG Electrocardiography is the process of producing an electrocardiogram (ECG or EKG). It is an of the which is a graph of versus time of the electrical activity of the heart using s placed on the skin. These electrodes detect the small electri ...

ECG
. The phrase "heart attack" is often used non-specifically to refer to myocardial infarction. An MI is different from—but can cause—
cardiac arrest Cardiac arrest is a sudden loss of Circulatory system, blood flow throughout the body resulting from the failure of the heart to pump effectively. It is a rapidly fatal medical emergency requiring immediate intervention with cardiopulmonary resus ...
, where the heart is not contracting at all or so poorly that all vital organs cease to function, thus might lead to death. It is also distinct from
heart failure Heart failure (HF), also known as congestive heart failure (CHF) and (congestive) cardiac failure (CCF), is a caused by the failure of the 's function as a pump supporting the ; its result from a structural and/or functional abnormality of the ...
, in which the pumping action of the heart is impaired. However, an MI may lead to heart failure.


Signs and symptoms

Chest pain that may or may not radiate to other parts of the body is the most typical and significant symptom of myocardial infarction. It might be accompanied by other symptoms such as sweating.


Pain

Chest pain Chest pain is pain or discomfort in the chest, typically the front of the chest. It may be described as sharp, dull, pressure, heaviness or squeezing. Associated symptoms may include pain in the shoulder, arm, upper abdomen, or jaw, along with na ...
is one of the most common symptom of acute myocardial infarction and is often described as a sensation of tightness, pressure, or squeezing. Pain radiates most often to the left arm, but may also radiate to the lower jaw, neck, right arm, back, and upper
abdomen The abdomen (colloquially called the belly, tummy, midriff or stomach) is the part of the body between the thorax (chest) and pelvis, in humans and in other vertebrates. The abdomen is the front part of the abdominal segment of the Trunk (anatomy) ...

abdomen
. The pain most suggestive of an acute MI, with the highest
likelihood ratio The likelihood function (often simply called the likelihood) describes the joint probability Given random variables X,Y,\ldots, that are defined on a probability space, the joint probability distribution for X,Y,\ldots is a probability distributi ...
, is pain radiating to the right arm and shoulder. Similarly, chest pain similar to a previous heart attack is also suggestive. The pain associated with MI is usually diffuse, does not change with position, and lasts for more than 20 minutes. It might be described as pressure, tightness, knifelike, tearing, burning sensation (all these are also manifested during other diseases). It could be felt as an unexplained anxiety, or even pain might be absent at all. Levine's sign, in which a person localizes the chest pain by clenching one or both fists over their
sternum The sternum or breastbone is a long flat bone located in the central part of the chest. It connects to the ribs via cartilage and forms the front of the rib cage, thus helping to protect the heart, human lung, lungs, and major blood vessels from in ...
, has classically been thought to be predictive of cardiac chest pain, although a prospective observational study showed it had a poor
positive predictive value 417x417px, Positive and negative predictive values - 2 The positive and negative predictive values (PPV and NPV respectively) are the proportions of positive and negative results in statistics Statistics is the discipline that concerns the ...
. Typically, chest pain because of ischemia, be it unstable angina or myocardial infarction, lessens with the use of
nitroglycerin Nitroglycerin (NG), also known as trinitroglycerin (TNG), nitro, glyceryl trinitrate (GTN), or 1,2,3-trinitroxypropane, is a dense, colorless, oily, explosive An explosive (or explosive material) is a reactive substance that contains a grea ...
, but nitroglycerin may also relieve chest pain arising from non-cardiac causes.


Associated symptoms

Chest pain may be accompanied by
sweating Perspiration, also known as sweating, is the production of fluids secreted by the sweat glands in the skin of mammal Mammals (from Latin language, Latin , 'breast') are a group of vertebrate animals constituting the class (biology), cla ...
, nausea or vomiting, and
fainting Syncope, commonly known as fainting, is a loss of consciousness Consciousness, at its simplest, is or of internal and external existence. Despite millennia of analyses, definitions, explanations and debates by philosophers and scienti ...
, and these symptoms may also occur without any pain at all. In women, the most common symptoms of myocardial infarction include shortness of breath, weakness, and
fatigue Fatigue describes a state of tiredness that does not resolve with rest or sleep. In general usage, fatigue is synonymous with extreme tiredness or exhaustion that normally follows prolonged physical or mental activity. When it does not resolve ...
. Women are more likely to have unusual or unexplained tiredness and nausea or vomiting as symptoms. Women having heart attacks are more likely to have palpitations, back pain, labored breath, vomiting, and left arm pain than men, although the studies showing these differences had high variability. Women are less likely to report chest pain during a heart attack and more likely to report nausea, jaw pain, neck pain, cough, and fatigue, although these findings are inconsistent across studies. Women with heart attacks also had more indigestion, dizziness, loss of appetite, and loss of consciousness.
Shortness of breath Shortness of breath (SOB), also known as dyspnea (BrE British English (BrE) is the standard dialect A standard language (also standard variety, standard dialect, and standard) is a language variety that has undergone substantial codificat ...
is a common, and sometimes the only symptom, occurring when damage to the heart limits the
output Output may refer to: * The information produced by a computer, see * An output state of a system, see * , the amount of goods and services produced ** in economics, the value of net output or GDP plus intermediate consumption ** in economics, ...
of the
left ventricle A ventricle is one of two large chambers toward the bottom of the heart The heart is a muscle, muscular Organ (anatomy), organ in most animals, which pumps blood through the blood vessels of the circulatory system. The pumped blood carries ...
, with breathlessness arising either from low oxygen in the blood, or
pulmonary edema Pulmonary edema is fluid accumulation in the tissue and air spaces of the lungs. It leads to impaired gas exchange and may cause respiratory failure. It is due to either failure of the left ventricle of the heart to remove blood adequately ...

pulmonary edema
. Other less common symptoms include weakness, light-headedness,
palpitation Palpitations are perceived abnormalities of the heartbeat characterized by awareness of cardiac muscle contractions in the chest, which is further characterized by the hard, fast and/or irregular beatings of the heart. Symptoms include a rapid ...
s, and abnormalities in
heart rate Heart rate is the speed of the heartbeat Heartbeat or heartbeats may refer to: Physiology *Cardiac cycle, of the heart *Contraction of the cardiac muscle, muscles of the heart, or a perceived effect of it, such as: **Heart sounds, the noises gene ...

heart rate
or
blood pressure Blood pressure (BP) is the pressure Pressure (symbol: ''p'' or ''P'') is the force In physics Physics is the natural science that studies matter, its Elementary particle, fundamental constituents, its Motion (physics), motio ...

blood pressure
. These symptoms are likely induced by a massive surge of
catecholamines (noradrenaline) Image:Adrenalin - Adrenaline.svg">140px, epinephrine (adrenaline) A catecholamine (; abbreviated CA) is a monoamine neurotransmitter, an organic compound that has a catechol">organic_compound.html" ;"title="monoamine neurotra ...
from the
sympathetic nervous system The sympathetic nervous system (SNS) is one of two divisions of the autonomic nervous system, along with the parasympathetic nervous system. The enteric nervous system is sometimes considered part of the autonomic nervous system, and sometimes co ...
, which occurs in response to pain and, where present, low
blood pressure Blood pressure (BP) is the pressure Pressure (symbol: ''p'' or ''P'') is the force In physics Physics is the natural science that studies matter, its Elementary particle, fundamental constituents, its Motion (physics), motio ...

blood pressure
.
Loss of consciousness Unconsciousness is a state which occurs when the ability to maintain an awareness of self and environment is lost. It involves a complete, or near-complete, lack of responsiveness to people and other environmental stimulus A stimulus is somethin ...

Loss of consciousness
due to inadequate blood flow to the
brain A brain is an organ Organ may refer to: Biology * Organ (anatomy) An organ is a group of Tissue (biology), tissues with similar functions. Plant life and animal life rely on many organs that co-exist in organ systems. A given organ's tiss ...

brain
and
cardiogenic shock Cardiogenic shock (CS) is a medical emergency resulting from inadequate blood flow due to the dysfunction of the ventricles of the heart.Textbooks of Internal MedicinHarrison's Principles of Internal Medicine 16th Edition, The McGraw-Hill McG ...
, and sudden death, frequently due to the development of
ventricular fibrillation Ventricular fibrillation (V-fib or VF) is an abnormal heart rhythm in which the ventricles of the heart The heart is a cardiac muscle, muscular Organ (biology), organ in most animals, which pumps blood through the blood vessels of the ci ...

ventricular fibrillation
, can occur in myocardial infarctions. Cardiac arrest, and atypical symptoms such as
palpitations Palpitations are perceived abnormalities of the heartbeat characterized by awareness of cardiac muscle contractions in the chest, which is further characterized by the hard, fast and/or irregular beatings of the heart. Symptoms include a rapid ...
, occur more frequently in women, the elderly, those with diabetes, in people who have just had surgery, and in critically ill patients.


Silent infarction

"Silent" myocardial infarctions can happen without any symptoms at all. These cases can be discovered later on
electrocardiograms Electrocardiography is the process of producing an electrocardiogram (ECG or EKG). It is a graph of voltage Voltage, electric potential difference, electromotive force emf, electric pressure or electric tension is the difference in elec ...
, using blood enzyme tests, or at
autopsy An autopsy (post-mortem examination, obduction, necropsy, or autopsia cadaverum) is a surgical procedure that consists of a thorough examination Examination may refer to: * Physical examination, a medical procedure * Questioning and more speci ...
after a person has died. Such silent myocardial infarctions represent between 22 and 64% of all infarctions, and are more common in the
elderly An elderly woman at a Ringing Cedars' settlement in Russia.">Russia.html" ;"title="Ringing Cedars' settlement in Russia">Ringing Cedars' settlement in Russia. Old age refers to ages nearing or surpassing the life expectancy of human beings, a ...
, in those with
diabetes mellitus Diabetes mellitus, commonly known as just diabetes, is a group of metabolic disorder A metabolic disorder is a disorder that negatively alters the body's processing and distribution of macronutrients such as proteins, fats, and carbohydrates ...
and after
heart transplantation A heart transplant, or a cardiac transplant, is a surgical transplant procedure performed on patients with end-stage heart failure Heart failure (HF), also known as congestive heart failure (CHF), (congestive) cardiac failure (CCF), and decomp ...
. In people with diabetes, differences in
pain threshold The threshold of pain or pain threshold is the point along a line chart, curve of increasing perception of a stimulus (physiology), stimulus at which pain begins to be felt. It is an entirely subjective phenomenon. A distinction must be maintained b ...
,
autonomic neuropathy Autonomic neuropathy (AN or AAN) is a form of polyneuropathy Polyneuropathy ( poly- + neuro- + wikt:-pathy, -pathy) is damage or disease affecting peripheral nerves (peripheral neuropathy) in roughly the same areas on both sides of the body, fea ...
, and
psychological Psychology is the scientific Science (from the Latin Latin (, or , ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally spoken in the area around Rome, known ...

psychological
factors have been cited as possible explanations for the lack of symptoms. In heart transplantation, the
donor A donor in general is a person, organization or government which donation, donates something voluntarily. The term is usually used to represent a form of pure altruism, but is sometimes used when the payment for a service is recognized by all partie ...

donor
heart is not fully innervated by the nervous system of the recipient.


Risk factors

The most prominent risk factors for myocardial infarction are older age, actively
smoking Smoking is a practice in which a substance is burned and the resulting smoke Smoke is a collection of airborne and es emitted when a material undergoes or , together with the quantity of air that is or otherwise mixed into the ma ...

smoking
,
high blood pressure Hypertension (HTN or HT), also known as high blood pressure (HBP), is a long-term Long-Term Capital Management L.P. (LTCM) was a hedge fund''A financial History of the United States Volume II: 1970–2001'', Jerry W. Markham, Chapter 5: "Bank ...

high blood pressure
,
diabetes mellitus Diabetes mellitus, commonly known as just diabetes, is a group of metabolic disorder A metabolic disorder is a disorder that negatively alters the body's processing and distribution of macronutrients such as proteins, fats, and carbohydrates ...
, and total
cholesterol Cholesterol is any of a class of certain organic Organic may refer to: * Organic, of or relating to an organism, a living entity * Organic, of or relating to an anatomical organ (anatomy), organ Chemistry * Organic matter, matter that has co ...

cholesterol
and
high-density lipoprotein High-density lipoprotein (HDL) is one of the five major groups of lipoprotein 250px, Structure of a chylomicron. ApoA, ApoB, ApoC, ApoE are apolipoproteins; green particles are phospholipids; T is triacylglycerol; C is cholesterol ester. A lipop ...
levels. Many risk factors of myocardial infarction are shared with
coronary artery disease Coronary artery disease (CAD), also called coronary heart disease (CHD), ischemic heart disease (IHD), or simply heart disease, involves the reduction of blood flow to the heart muscle Cardiac muscle (also called heart muscle or myocardium) is ...
, the primary cause of myocardial infarction, with other risk factors including male sex, low levels of physical activity, a past
family history Genealogy (from el, γενεαλογία ' "study of family trees") is the study of families In human society, family (from la, familia) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity ...
,
obesity Obesity is a medical condition A disease is a particular abnormal condition that negatively affects the structure or function of all or part of an organism, and that is not due to any immediate external injury. Diseases are often ...

obesity
, and alcohol use. Risk factors for myocardial disease are often included in risk factor stratification scores, such as the
Framingham Risk Score The Framingham Risk Score is a gender-specific algorithm of an algorithm (Euclid's algorithm) for calculating the greatest common divisor (g.c.d.) of two numbers ''a'' and ''b'' in locations named A and B. The algorithm proceeds by successive sub ...
. At any given age, men are more at risk than women for the development of cardiovascular disease. High levels of blood cholesterol is a known risk factor, particularly high
low-density lipoprotein Low-density lipoprotein (LDL) is one of the five major groups of lipoprotein which transport all fat molecules around the body in the extracellular water. These groups, from least dense to most dense, are chylomicrons (aka ULDL by the overall den ...
, low
high-density lipoprotein High-density lipoprotein (HDL) is one of the five major groups of lipoprotein 250px, Structure of a chylomicron. ApoA, ApoB, ApoC, ApoE are apolipoproteins; green particles are phospholipids; T is triacylglycerol; C is cholesterol ester. A lipop ...
, and high
triglycerides 300px, Example of an unsaturated fat triglyceride (C55H98O6). Left part: glycerol; right part, from top to bottom: palmitic acid, oleic acid">palmitic_acid.html" ;"title="glycerol; right part, from top to bottom: palmitic acid">glycerol; right par ...
. Many risk factors for myocardial infarction are potentially modifiable, with the most important being
tobacco smoking Tobacco smoking is the practice of burning tobacco Tobacco is the common name of several plants in the ' of the , and the general term for any product prepared from the of these plants. of tobacco are known, but the chief commerci ...

tobacco smoking
(including secondhand smoke). Smoking appears to be the cause of about 36% and obesity the cause of 20% of
coronary artery disease Coronary artery disease (CAD), also called coronary heart disease (CHD), ischemic heart disease (IHD), or simply heart disease, involves the reduction of blood flow to the heart muscle Cardiac muscle (also called heart muscle or myocardium) is ...
. Lack of physical activity has been linked to 7–12% of cases. Less common causes include stress-related causes such as
job stress Occupational stress is psychological stress In psychology Psychology is the science of mind and behavior. Psychology includes the study of consciousness, conscious and Unconscious mind, unconscious phenomena, as well as feeling and thoug ...
, which accounts for about 3% of cases, and chronic high stress levels.


Diet

There is varying evidence about the importance of
saturated fat A saturated fat is a type of fat In nutrition Nutrition is the biochemical and physiological process by which an organism In biology, an organism (from Ancient Greek, Greek: ὀργανισμός, ''organismos'') is any indivi ...
in the development of myocardial infarctions. Eating polyunsaturated fat instead of
saturated fat A saturated fat is a type of fat In nutrition Nutrition is the biochemical and physiological process by which an organism In biology, an organism (from Ancient Greek, Greek: ὀργανισμός, ''organismos'') is any indivi ...
s has been shown in studies to be associated with a decreased risk of myocardial infarction, while other studies find little evidence that reducing dietary saturated fat or increasing
polyunsaturated fat In nutrition Nutrition is the biochemical and physiological process by which an organism In biology, an organism (from Ancient Greek, Greek: ὀργανισμός, ''organismos'') is any individual contiguous system that embodies ...
intake affects heart attack risk. Dietary cholesterol does not appear to have a significant effect on blood cholesterol and thus recommendations about its consumption may not be needed.
Trans fats In nutrition Nutrition is the biochemical and physiological process by which an organism In biology, an organism (from Ancient Greek, Greek: ὀργανισμός, ''organismos'') is any individual contiguous system that embodies ...
do appear to increase risk. Acute and prolonged intake of high quantities of alcoholic drinks (3–4 or more daily) increases the risk of a heart attack.


Genetics

Family history of ischemic heart disease or MI, particularly if one has a male first-degree relative (father, brother) who had a myocardial infarction before age 55 years, or a female first-degree relative (mother, sister) less than age 65 increases a person's risk of MI. Genome-wide association studies have found 27 genetic variants that are associated with an increased risk of myocardial infarction. The strongest association of MI has been found with chromosome 9 on the short arm ''p'' at Locus (genetics), locus 21, which contains genes CDKN2A and 2B, although the single nucleotide polymorphisms that are implicated are within a non-coding region. The majority of these variants are in regions that have not been previously implicated in coronary artery disease. The following genes have an association with MI: PCSK9, SORT1, MIA3, WDR12, MRAS, PHACTR1, Lipoprotein(a), LPA, TCF21, MTHFDSL, ZC3HC1, CDKN2A, CDKN2B, 2B, ABO, PDGF0, APOA5, MNF1ASM283, Collagen, type IV, alpha 1, COL4A1, HHIPC1, SMAD3, ADAMTS7, RAS1, SMG6, SNF8, LDLR, SLC5A3, MRPS6, KCNE2.


Other

The risk of having a myocardial infarction increases with older age, low physical activity, and low socioeconomic status. Heart attacks appear to occur more commonly in the morning hours, especially between 6AM and noon. Evidence suggests that heart attacks are at least three times more likely to occur in the morning than in the late evening. Shift work is also associated with a higher risk of MI. And one analysis has found an increase in heart attacks immediately following the start of daylight saving time. Women who use combined oral contraceptive pills have a modestly increased risk of myocardial infarction, especially in the presence of other risk factors. The use of non-steroidal anti inflammatory drugs (NSAIDs), even for as short as a week, increases risk. Endometriosis in women under the age of 40 is an identified risk factor. Air pollution is also an important modifiable risk. Short-term exposure to air pollution such as carbon monoxide, nitrogen dioxide, and sulfur dioxide (but not ozone) have been associated with MI and other acute cardiovascular events. For sudden cardiac deaths, every increment of 30 units in Pollutant Standards Index correlated with an 8% increased risk of out-of-hospital cardiac arrest on the day of exposure. Extremes of temperature are also associated. A number of acute and chronic infections including ''Chlamydophila pneumoniae'', influenza, ''Helicobacter pylori'', and ''Porphyromonas gingivalis'' among others have been linked to atherosclerosis and myocardial infarction. As of 2013, there is no evidence of benefit from antibiotics or vaccination, however, calling the association into question. Myocardial infarction can also occur as a late consequence of Kawasaki disease. Calcium deposits in the coronary arteries can be detected with CT scans. Calcium seen in coronary arteries can provide predictive information beyond that of classical risk factors. Hyperhomocysteinemia, High blood levels of the amino acid homocysteine is associated with premature atherosclerosis; whether elevated homocysteine in the normal range is causal is controversial. In people without evident
coronary artery disease Coronary artery disease (CAD), also called coronary heart disease (CHD), ischemic heart disease (IHD), or simply heart disease, involves the reduction of blood flow to the heart muscle Cardiac muscle (also called heart muscle or myocardium) is ...
, possible causes for the myocardial infarction are coronary spasm or spontaneous coronary artery dissection, coronary artery dissection.


Mechanism


Atherosclerosis

The most common cause of a myocardial infarction is the rupture of an atherosclerotic plaque on an artery supplying heart muscle. Plaques can become unstable, rupture, and additionally promote the formation of a thrombus, blood clot that blocks the artery; this can occur in minutes. Blockage of an artery can lead to tissue death in tissue being supplied by that artery. Atherosclerotic plaques are often present for decades before they result in symptoms. The gradual buildup of
cholesterol Cholesterol is any of a class of certain organic Organic may refer to: * Organic, of or relating to an organism, a living entity * Organic, of or relating to an anatomical organ (anatomy), organ Chemistry * Organic matter, matter that has co ...

cholesterol
and fibrous tissue in plaques in the wall of the coronary artery, coronary arteries or other arteries, typically over decades, is termed atherosclerosis. Atherosclerosis is characterized by progressive inflammation of the walls of the arteries. Inflammatory cells, particularly macrophages, move into affected arterial walls. Over time, they become laden with cholesterol products, particularly LDL, and become foam cells. A atheroma, cholesterol core forms as foam cells die. In response to growth factors secreted by macrophages, smooth muscle and other cells move into the plaque and act to stabilize it. A stable plaque may have a thick fibrous cap with calcification. If there is ongoing inflammation, the cap may be thin or ulcerate. Exposed to the pressure associated with blood flow, plaques, especially those with a thin lining, may rupture and trigger the formation of a blood clot (thrombus). The cholesterol crystals have been associated with plaque rupture through mechanical injury and inflammation.


Other causes

Atherosclerotic disease is not the only cause of myocardial infarction, but it may exacerbate or contribute to other causes. A myocardial infarction may result from a heart with a limited blood supply subject to increased oxygen demands, such as in fever, tachycardia, a fast heart rate, hyperthyroidism, anemia, too few red blood cells in the bloodstream, or hypotension, low blood pressure. Damage or failure of procedures such as
percutaneous coronary intervention Percutaneous coronary intervention (PCI) is a non-surgical procedure used to treat narrowing of the coronary arteries The coronary arteries are the arterial blood vessels of coronary circulation, which transport oxygenated blood to the heart m ...
or coronary artery bypass grafts may cause a myocardial infarction. Spasm of coronary arteries, such as Prinzmetal's angina may cause blockage.


Tissue death

If impaired blood flow to the heart lasts long enough, it triggers a process called the ischemic cascade; the heart cells in the territory of the blocked coronary artery die (:wikt:infarction, infarction), chiefly through necrosis, and do not grow back. A collagen scar forms in their place. When an artery is blocked, cells lack oxygen, needed to produce Adenosine triphosphate, ATP in mitochondria. ATP is required for the maintenance of electrolyte balance, particularly through the Na/K ATPase. This leads to an ischemic cascade of intracellular changes, necrosis and apoptosis of affected cells. Cells in the area with the worst blood supply, just below the inner surface of the heart (endocardium), are most susceptible to damage. Ischemia first affects this region, the ''subendocardial'' region, and tissue begins to die within 15–30 minutes of loss of blood supply. The dead tissue is surrounded by a zone of potentially reversible ischemia that progresses to become a full-thickness ''transmural'' infarct. The initial "wave" of infarction can take place over 3–4 hours. These changes are seen on gross pathology and cannot be predicted by the presence or absence of Q waves on an ECG. The position, size and extent of an infarct depends on the affected artery, totality of the blockage, duration of the blockage, the presence of Collateralization, collateral blood vessels, oxygen demand, and success of interventional procedures. Tissue death and myocardial scarring alter the normal conduction pathways of the heart, and weaken affected areas. The size and location puts a person at risk of Heart arrhythmia, abnormal heart rhythms (arrhythmias) or heart block, ventricular aneurysm, aneurysm of the heart ventricles, Dressler's syndrome, inflammation of the heart wall following infarction, and rupture of the heart wall that can have catastrophic consequences. Injury to the myocardium also occurs during re-perfusion. This might manifest as ventricular arrhythmia. The re-perfusion injury is a consequence of the calcium and sodium uptake from the cardiac cells and the release of oxygen radicals during reperfusion. No-reflow phenomenon–when blood is still unable to be distributed to the affected myocardium despite clearing the occlusion—also contributes to myocardial injury. Topical endothelial swelling is one of many factors contributing to this phenomenon.


Diagnosis


Criteria

A myocardial infarction, according to current consensus, is defined by elevated cardiac biomarkers with a rising or falling trend and at least one of the following: * Symptoms relating to ischemia * Changes on an
electrocardiogram Electrocardiography is the process of producing an electrocardiogram (ECG or EKG). It is a graph of voltage Voltage, electric potential difference, electromotive force emf, electric pressure or electric tension is the difference in elec ...

electrocardiogram
(ECG), such as ST segment changes, new left bundle branch block, or pathologic QRS complex#Q wave, Q waves * Changes in the motion of the heart wall on imaging * Demonstration of a thrombus on angiogram or at autopsy.


Types

A myocardial infarction is usually clinically classified as an ST-elevation MI (STEMI) or a non-ST elevation MI (NSTEMI). These are based on
ST elevation ST elevation refers to a finding on an electrocardiogram Electrocardiography is the process of producing an electrocardiogram (ECG or EKG). It is a graph of voltage Voltage, electric potential difference, electromotive force emf, elect ...
, a portion of a heartbeat graphically recorded on an
ECG Electrocardiography is the process of producing an electrocardiogram (ECG or EKG). It is an of the which is a graph of versus time of the electrical activity of the heart using s placed on the skin. These electrodes detect the small electri ...

ECG
. STEMIs make up about 25–40% of myocardial infarctions. A more explicit classification system, based on international consensus in 2012, also exists. This classifies myocardial infarctions into five types: # Spontaneous MI related to plaque erosion and/or rupture fissuring, or dissection # MI related to ischemia, such as from increased oxygen demand or decreased supply, e.g. coronary artery spasm, coronary embolism, anemia, arrhythmias, high blood pressure, or low blood pressure # Sudden unexpected cardiac death, including cardiac arrest, where symptoms may suggest MI, an ECG may be taken with suggestive changes, or a blood clot is found in a coronary artery by angiography and/or at autopsy, but where blood samples could not be obtained, or at a time before the appearance of cardiac biomarkers in the blood # Associated with coronary angioplasty or stents #* Associated with
percutaneous coronary intervention Percutaneous coronary intervention (PCI) is a non-surgical procedure used to treat narrowing of the coronary arteries The coronary arteries are the arterial blood vessels of coronary circulation, which transport oxygenated blood to the heart m ...
(PCI) #* Associated with stent thrombosis as documented by angiography or at autopsy # Associated with coronary artery bypass graft, CABG # Associated with spontaneous coronary artery dissection in young, fit women


Cardiac biomarkers

There are many different biomarkers used to determine the presence of cardiac muscle damage. Troponins, measured through a blood test, are considered to be the best, and are preferred because they have greater sensitivity and specificity for measuring injury to the heart muscle than other tests. A rise in troponin occurs within 2–3 hours of injury to the heart muscle, and peaks within 1–2 days. The level of the troponin, as well as a change over time, are useful in measuring and diagnosing or excluding myocardial infarctions, and the diagnostic accuracy of troponin testing is improving over time. One high-sensitivity cardiac troponin can rule out a heart attack as long as the ECG is normal. Other tests, such as CK-MB or myoglobin, are discouraged. CK-MB is not as specific as troponins for acute myocardial injury, and may be elevated with past cardiac surgery, inflammation or electrical cardioversion; it rises within 4–8 hours and returns to normal within 2–3 days. Copeptin may be useful to rule out MI rapidly when used along with troponin.


Electrocardiogram

Electrocardiograms (ECGs) are a series of leads placed on a person's chest that measure electrical activity associated with contraction of the heart muscle. The taking of an ECG is an important part of the workup of an AMI, and ECGs are often not just taken once but may be repeated over minutes to hours, or in response to changes in signs or symptoms. ECG readouts product a waveform with different labelled features. In addition to a rise in biomarkers, a rise in the ST segment, changes in the shape or flipping of T waves, new QRS complex#Q wave, Q waves, or a new left bundle branch block can be used to diagnose an AMI. In addition,
ST elevation ST elevation refers to a finding on an electrocardiogram Electrocardiography is the process of producing an electrocardiogram (ECG or EKG). It is a graph of voltage Voltage, electric potential difference, electromotive force emf, elect ...
can be used to diagnose an ST segment myocardial infarction (STEMI). A rise must be new in V2 and V3 ≥2 mm (0,2 mV) for males or ≥1.5 mm (0.15 mV) for females or ≥1 mm (0.1 mV) in two other contiguous leads, adjacent chest or limb leads. ST elevation is associated with infarction, and may be preceded by changes indicating ischemia, such as ST depression or inversion of the T waves. Abnormalities can help differentiate the location of an infarct, based on the leads that are affected by changes. Early STEMIs may be preceded by peaked T waves. Other ECG abnormalities relating to complications of acute myocardial infarctions may also be evident, such as atrial fibrillation, atrial or
ventricular fibrillation Ventricular fibrillation (V-fib or VF) is an abnormal heart rhythm in which the ventricles of the heart The heart is a cardiac muscle, muscular Organ (biology), organ in most animals, which pumps blood through the blood vessels of the ci ...

ventricular fibrillation
.


Imaging

Noninvasive imaging plays an important role in the diagnosis and characterisation of myocardial infarction. Tests such as chest X-rays can be used to explore and exclude alternate causes of a person's symptoms. Tests such as stress echocardiography and myocardial perfusion imaging can confirm a diagnosis when a person's history, physical examination (including cardiac examination) ECG, and cardiac biomarkers suggest the likelihood of a problem. Echocardiography, an ultrasound scan of the heart, is able to visualize the heart, its size, shape, and any abnormal motion of the heart walls as they beat that may indicate a myocardial infarction. The flow of blood can be imaged, and contrast dyes may be given to improve image. Other scans using radioactive contrast include SPECT CT-scans using thallium chloride, thallium, technetium (99mTc) sestamibi, sestamibi (MIBI scans) or tetrofosmin; or a PET scan using Fludeoxyglucose (18F), Fludeoxyglucose or rubidium-82. These nuclear medicine scans can visualize the perfusion of heart muscle. SPECT may also be used to determine viability of tissue, and whether areas of ischemia are inducible. Medical societies and professional guidelines recommend that the physician confirm a person is at high risk for myocardial infarction before conducting imaging tests to make a diagnosis, as such tests are unlikely to change management and result in increased costs. Patients who have a normal ECG and who are able to exercise, for example, do not merit routine imaging. File:UOTW 36 - Ultrasound of the Week 1.webm, Poor movement of the heart due to an MI as seen on ultrasound File:UOTW 36 - Ultrasound of the Week 2.webm, Pulmonary edema due to an MI as seen on ultrasound


Differential diagnosis

There are many causes of
chest pain Chest pain is pain or discomfort in the chest, typically the front of the chest. It may be described as sharp, dull, pressure, heaviness or squeezing. Associated symptoms may include pain in the shoulder, arm, upper abdomen, or jaw, along with nau ...
, which can originate from the heart, lungs, gastrointestinal tract, aorta, and other muscles, bones and nerves surrounding the chest. In addition to myocardial infarction, other causes include angina pectoris, angina, insufficient blood supply (ischemia) to the heart muscles without evidence of cell death, gastroesophageal reflux disease; pulmonary embolism, tumors of the lungs, pneumonia, rib fracture, costochondritis,
heart failure Heart failure (HF), also known as congestive heart failure (CHF) and (congestive) cardiac failure (CCF), is a caused by the failure of the 's function as a pump supporting the ; its result from a structural and/or functional abnormality of the ...
and other musculoskeletal injuries. Rarer severe differential diagnoses include aortic dissection, esophageal rupture, tension pneumothorax, and pericardial effusion causing cardiac tamponade. The chest pain in an MI may mimic
heartburn Heartburn, also known as pyrosis, cardialgia or acid indigestion, is a burning sensation in the central chest or upper central abdomen. The discomfort often rises in the chest and may radiate to the neck, throat, or angle of the arm. Heartbur ...
. Causes of sudden-onset breathlessness generally involve the lungs or heart – including
pulmonary edema Pulmonary edema is fluid accumulation in the tissue and air spaces of the lungs. It leads to impaired gas exchange and may cause respiratory failure. It is due to either failure of the left ventricle of the heart to remove blood adequately ...

pulmonary edema
, pneumonia, allergy, allergic reactions and asthma, and pulmonary embolus, ARDS, acute respiratory distress syndrome and metabolic acidosis. There are many different causes of fatigue, and myocardial infarction is not a common cause.


Prevention

There is a large crossover between the lifestyle and activity recommendations to prevent a myocardial infarction, and those that may be adopted as secondary prevention after an initial myocardial infarction, because of shared risk factors and an aim to reduce atherosclerosis affecting heart vessels. The influenza vaccine also appear to protect against myocardial infarction with a benefit of 15 to 45%.


Primary prevention


Lifestyle

Physical activity can reduce the risk of cardiovascular disease, and people at risk are advised to engage in 150 minutes of moderate or 75 minutes of vigorous-intensity aerobic exercise a week. Keeping a healthy weight, drinking alcohol within the recommended limits, and smoking cessation, quitting smoking reduce the risk of cardiovascular disease. Substituting
polyunsaturated fat In nutrition Nutrition is the biochemical and physiological process by which an organism In biology, an organism (from Ancient Greek, Greek: ὀργανισμός, ''organismos'') is any individual contiguous system that embodies ...
s such as olive oil and rapeseed oil instead of saturated fats may reduce the risk of myocardial infarction, although there is not universal agreement. Dietary modifications are recommended by some national authorities, with recommendations including increasing the intake of wholegrain starch, reducing sugar intake (particularly of refined sugar), consuming five portions of fruit and vegetables daily, consuming two or more portions of fish per week, and consuming 4–5 portions of unsalted Nut (fruit), nuts, seeds, or legumes per week. The dietary pattern with the greatest support is the Mediterranean diet. Vitamins and mineral supplements are of no proven benefit, and neither are plant stanols or Phytosterol, sterols. Public health measures may also act at a population level to reduce the risk of myocardial infarction, for example by reducing unhealthy diets (excessive salt, saturated fat, and trans fat) including food labeling and marketing requirements as well as requirements for catering and restaurants, and stimulating physical activity. This may be part of regional cardiovascular disease prevention programs or through the health impact assessment of regional and local plans and policies. Most guidelines recommend combining different preventive strategies. A 2015 Cochrane Review found some evidence that such an approach might help with 
blood pressure Blood pressure (BP) is the pressure Pressure (symbol: ''p'' or ''P'') is the force In physics Physics is the natural science that studies matter, its Elementary particle, fundamental constituents, its Motion (physics), motio ...

blood pressure
, body mass index and waist circumference. However, there was insufficient evidence to show an effect on mortality or actual cardio-vascular events.


Medication

Statins, drugs that act to lower blood cholesterol, decrease the incidence and mortality rates of myocardial infarctions. They are often recommended in those at an elevated risk of cardiovascular diseases. Aspirin has been studied extensively in people considered at increased risk of myocardial infarction. Based on numerous studies in different groups (e.g. people with or without diabetes), there does not appear to be a benefit strong enough to outweigh the risk of excessive bleeding. Nevertheless, many clinical practice guidelines continue to recommend aspirin for primary prevention, and some researchers feel that those with very high cardiovascular risk but low risk of bleeding should continue to receive aspirin.


Secondary prevention

There is a large crossover between the lifestyle and activity recommendations to prevent a myocardial infarction, and those that may be adopted as secondary prevention after an initial myocardial infarct. Recommendations include smoking cessation, stopping smoking, a gradual return to exercise, eating a healthy Diet (nutrition), diet, low in
saturated fat A saturated fat is a type of fat In nutrition Nutrition is the biochemical and physiological process by which an organism In biology, an organism (from Ancient Greek, Greek: ὀργανισμός, ''organismos'') is any indivi ...
and low in
cholesterol Cholesterol is any of a class of certain organic Organic may refer to: * Organic, of or relating to an organism, a living entity * Organic, of or relating to an anatomical organ (anatomy), organ Chemistry * Organic matter, matter that has co ...

cholesterol
, and Recommended maximum intake of alcoholic beverages, drinking alcohol within recommended limits, exercising, and trying to achieve a healthy weight. Exercise is both safe and effective even if people have had stents or heart failure, and is recommended to start gradually after 1–2 weeks. Counselling should be provided relating to medications used, and for warning signs of depression. Previous studies suggested a benefit from omega-3 fatty acid supplementation but this has not been confirmed.


Medications

Following a heart attack, nitrates, when taken for two days, and ACE inhibitor, ACE-inhibitors decrease the risk of death. Other medications include:
Aspirin Aspirin, also known as acetylsalicylic acid (ASA), is a medication A medication (also called medicament, medicine, pharmaceutical drug, medicinal drug or simply drug) is a drug Uncoated tablets, consisting of about 90% acetylsalicy ...

Aspirin
is continued indefinitely, as well as another antiplatelet agent such as clopidogrel or ticagrelor ("dual antiplatelet therapy" or DAPT) for up to twelve months. If someone has another medical condition that requires anticoagulation (e.g. with warfarin) this may need to be adjusted based on risk of further cardiac events as well as bleeding risk. In those who have had a stent, more than 12 months of clopidogrel plus aspirin does not affect the risk of death. Beta blocker therapy such as metoprolol or carvedilol is recommended to be started within 24 hours, provided there is no acute heart failure or heart block. The dose should be increased to the highest tolerated. Contrary to what was long believed, the use of beta blockers does not appear to affect the risk of death, possibly because other treatments for MI have improved. When beta blocker medication is given within the first 24–72 hours of a STEMI no lives are saved. However, 1 in 200 people were prevented from a repeat heart attack, and another 1 in 200 from having an abnormal heart rhythm. Additionally, for 1 in 91 the medication causes a cardiogenic shock, temporary decrease in the heart's ability to pump blood. ACE inhibitor therapy should be started within 24 hours, and continued indefinitely at the highest tolerated dose. This is provided there is no evidence of worsening kidney failure, hyperkalaemia, high potassium, low blood pressure, or known narrowing of the renal artery, renal arteries. Those who cannot tolerate ACE inhibitors may be treated with an angiotensin II receptor antagonist. Statin therapy has been shown to reduce mortality and subsequent cardiac events and should be commenced to lower LDL cholesterol. Other medications, such as ezetimibe, may also be added with this goal in mind. Aldosterone antagonists (spironolactone or eplerenone) may be used if there is evidence of left ventricular dysfunction after an MI, ideally after beginning treatment with an ACE inhibitor.


Other

A defibrillator, an electric device connected to the heart and surgically inserted under the skin, may be recommended. This is particularly if there are any ongoing signs of heart failure, with a low LVEF, left ventricular ejection fraction and a New York Heart Association grade II or III after 40 days of the infarction. Defibrillators detect potentially fatal arrhythmia and deliver an electrical shock to the person to depolarize a critical mass of the heart muscle.


Management

A myocardial infarction requires immediate medical attention. Treatment aims to preserve as much heart muscle as possible, and to prevent further complications. Treatment depends on whether the myocardial infarction is a STEMI or NSTEMI. Treatment in general aims to unblock blood vessels, reduce blood clot enlargement, reduce ischemia, and modify risk factors with the aim of preventing future MIs. In addition, the main treatment for myocardial infarctions with ECG evidence of ST elevation (STEMI) include
thrombolysis Thrombolysis, also called fibrinolytic therapy, is the breakdown ( lysis) of blood clots formed in blood vessel The blood vessels are the components of the circulatory system that transport blood throughout the human body. These vessels trans ...
or
percutaneous coronary intervention Percutaneous coronary intervention (PCI) is a non-surgical procedure used to treat narrowing of the coronary arteries The coronary arteries are the arterial blood vessels of coronary circulation, which transport oxygenated blood to the heart m ...
, although PCI is also ideally conducted within 1–3 days for NSTEMI. In addition to clinical judgement, risk stratification may be used to guide treatment, such as with the TIMI Risk Score, TIMI and GRACE Risk Score, GRACE scoring systems.


Pain

The pain associated with myocardial infarction is often treated with Nitroglycerin_(medication), nitroglycerin, a vasodilator, or
opioid Opioids are substances that act on opioid receptor Opioid receptors are a group of inhibitory G protein-coupled receptors with opioids as ligands. The endogenous opioids are dynorphins, enkephalins, endorphins, endomorphins and nocicepti ...
medications such as morphine. Nitroglycerin (given Sublingual administration, under the tongue or Intravenous therapy, injected into a vein) may improve blood supply to the heart. It is an important part of therapy for its pain relief effects, though there is no proven benefit to Case fatality rate, mortality. Morphine or other opioid medications may also be used, and are effective for the pain associated with STEMI. There is poor evidence that morphine shows any benefit to Outcome measure, overall outcomes, and there is some evidence of potential harm.


Antithrombotics

Aspirin Aspirin, also known as acetylsalicylic acid (ASA), is a medication A medication (also called medicament, medicine, pharmaceutical drug, medicinal drug or simply drug) is a drug Uncoated tablets, consisting of about 90% acetylsalicy ...

Aspirin
, an antiplatelet drug, is given as a loading dose to reduce the clot size and reduce further clotting in the affected artery. It is known to decrease mortality associated with acute myocardial infarction by at least 50%. P2Y12 inhibitors such as clopidogrel, prasugrel and ticagrelor are given concurrently, also as a loading dose, with the dose depending on whether further surgical management or fibrinolysis is planned. Prasugrel and ticagrelor are recommended in European and American guidelines, as they are active more quickly and consistently than clopidogrel. P2Y12 inhibitors are recommended in both NSTEMI and STEMI, including in PCI, with evidence also to suggest improved mortality. Heparins, particularly in the unfractionated form, act at several points in the clotting cascade, help to prevent the enlargement of a clot, and are also given in myocardial infarction, owing to evidence suggesting improved mortality rates. In very high-risk scenarios, Glycoprotein IIb/IIIa inhibitors, inhibitors of the platelet glycoprotein αIIbβ3a receptor such as eptifibatide or tirofiban may be used. There is varying evidence on the mortality benefits in NSTEMI. A 2014 review of P2Y12 inhibitors such as clopidogrel found they do not change the risk of death when given to people with a suspected NSTEMI prior to PCI, nor do heparins change the risk of death. They do decrease the risk of having a further myocardial infarction.


Angiogram

Primary
percutaneous coronary intervention Percutaneous coronary intervention (PCI) is a non-surgical procedure used to treat narrowing of the coronary arteries The coronary arteries are the arterial blood vessels of coronary circulation, which transport oxygenated blood to the heart m ...
(PCI) is the treatment of choice for STEMI if it can be performed in a timely manner, ideally within 90–120 minutes of contact with a medical provider. Some recommend it is also done in NSTEMI within 1–3 days, particularly when considered high-risk. A 2017 review, however, did not find a difference between early versus later PCI in NSTEMI. PCI involves small probes, inserted through peripheral blood vessels such as the femoral artery or radial artery into the blood vessels of the heart. The probes are then used to identify and clear blockages balloon angioplasty, using small balloons, which are dragged through the blocked segment, aspiration thrombectomy, dragging away the clot, or coronary stenting, the insertion of stents. Coronary artery bypass grafting is only considered when the affected area of heart muscle is large, and PCI is unsuitable, for example with difficult cardiac anatomy. After PCI, people are generally placed on aspirin indefinitely and on dual antiplatelet therapy (generally aspirin and clopidogrel) for at least a year.


Fibrinolysis

If PCI cannot be performed within 90 to 120 minutes in STEMI then fibrinolysis, preferably within 30 minutes of arrival to hospital, is recommended. If a person has had symptoms for 12 to 24 hours evidence for effectiveness of thrombolysis is less and if they have had symptoms for more than 24 hours it is not recommended. Thrombolysis involves the administration of medication that activates the fibrinolysis, enzymes that normally dissolve blood clots. These medications include tissue plasminogen activator, reteplase, streptokinase, and tenecteplase. Thrombolysis is not recommended in a number of situations, particularly when associated with a high risk of bleeding or the potential for problematic bleeding, such as active bleeding, past strokes or bleeds into the brain, or severe hypertension. Situations in which thrombolysis may be considered, but with caution, include recent surgery, use of anticoagulants, pregnancy, and proclivity to bleeding. Major risks of thrombolysis are major bleeding and intracranial bleeding. Pre-hospital thrombolysis reduces time to thrombolytic treatment, based on studies conducted in higher income countries, however it is unclear whether this has an impact on mortality rates.


Other

In the past, high flow oxygen was recommended for everyone with a possible myocardial infarction. More recently, no evidence was found for routine use in those with normal oxygen levels and there is potential harm from the intervention. Therefore, oxygen is currently only recommended if oxygen levels are found to be low or if someone is in respiratory distress. If despite thrombolysis there is significant
cardiogenic shock Cardiogenic shock (CS) is a medical emergency resulting from inadequate blood flow due to the dysfunction of the ventricles of the heart.Textbooks of Internal MedicinHarrison's Principles of Internal Medicine 16th Edition, The McGraw-Hill McG ...
, continued severe chest pain, or less than a 50% improvement in
ST elevation ST elevation refers to a finding on an electrocardiogram Electrocardiography is the process of producing an electrocardiogram (ECG or EKG). It is a graph of voltage Voltage, electric potential difference, electromotive force emf, elect ...
on the ECG recording after 90 minutes, then rescue PCI is indicated emergently. Those who have had
cardiac arrest Cardiac arrest is a sudden loss of Circulatory system, blood flow throughout the body resulting from the failure of the heart to pump effectively. It is a rapidly fatal medical emergency requiring immediate intervention with cardiopulmonary resus ...
may benefit from targeted temperature management with evaluation for implementation of hypothermia protocols. Furthermore, those with cardiac arrest, and ST elevation at any time, should usually have angiography. Aldosterone antagonists appear to be useful in people who have had an STEMI and do not have heart failure.


Rehabilitation

Cardiopulmonary rehabilitation, Cardiac rehabilitation benefits many who have experienced myocardial infarction, even if there has been substantial heart damage and resultant left ventricular failure. It should start soon after discharge from the hospital. The program may include lifestyle advice, exercise, social support, as well as recommendations about driving, flying, sports participation, stress management, and sexual intercourse. Returning to sexual activity after myocardial infarction is a major concern for most patients, and is an important area to be discussed in the provision of holistic care. Exercise-based cardiovascular rehabilitation programs reduce cardiovascular mortality and subsequent hospitalization.


Prognosis

The prognosis after myocardial infarction varies greatly depending on the extent and location of the affected heart muscle, and the development and management of complications. Prognosis is worse with older age and social isolation. Anterior infarcts, persistent ventricular tachycardia or fibrillation, development of heart blocks, and left ventricular impairment are all associated with poorer prognosis. Without treatment, about a quarter of those affected by MI die within minutes and about forty percent within the first month. Morbidity and mortality from myocardial infarction has however improved over the years due to earlier and better treatment: in those who have a STEMI in the United States, between 5 and 6 percent die before leaving the hospital and 7 to 18 percent die within a year. It is unusual for babies to experience a myocardial infarction, but when they do, about half die. In the short-term, neonatal survivors seem to have a normal quality of life.


Complications

Complications may occur immediately following the myocardial infarction or may take time to develop. Heart arrhythmia, Disturbances of heart rhythms, including atrial fibrillation, ventricular tachycardia and ventricular fibrillation, fibrillation and heart block can arise as a result of ischemia, cardiac scarring, and infarct location. Stroke is also a risk, either as a result of Arterial embolism, clots transmitted from the heart during PCI, as a result of bleeding following anticoagulation, or as a result of disturbances in the heart's ability to pump effectively as a result of the infarction. mitral regurgitation, Regurgitation of blood through the mitral valve is possible, particularly if the infarction causes dysfunction of the papillary muscle. Cardiogenic shock as a result of the heart being unable to adequately pump blood may develop, dependent on infarct size, and is most likely to occur within the days following an acute myocardial infarction. Cardiogenic shock is the largest cause of in-hospital mortality. Rupture of the ventricular dividing wall or left ventricular wall may occur within the initial weeks. Dressler's syndrome, a reaction following larger infarcts and a cause of pericarditis is also possible. Heart failure may develop as a long-term consequence, with an impaired ability of heart muscle to pump, scarring, and an increase in the size of the existing muscle. Ventricular aneurysm, Aneurysm of the left ventricle myocardium develops in about 10% of MI and is itself a risk factor for heart failure, ventricular arrhythmia, and the development of embolism, clots. Risk factors for complications and death include age, Hemodynamics, hemodynamic parameters (such as
heart failure Heart failure (HF), also known as congestive heart failure (CHF) and (congestive) cardiac failure (CCF), is a caused by the failure of the 's function as a pump supporting the ; its result from a structural and/or functional abnormality of the ...
,
cardiac arrest Cardiac arrest is a sudden loss of Circulatory system, blood flow throughout the body resulting from the failure of the heart to pump effectively. It is a rapidly fatal medical emergency requiring immediate intervention with cardiopulmonary resus ...
on admission, Systole (medicine), systolic
blood pressure Blood pressure (BP) is the pressure Pressure (symbol: ''p'' or ''P'') is the force In physics Physics is the natural science that studies matter, its Elementary particle, fundamental constituents, its Motion (physics), motio ...

blood pressure
, or Killip class of two or greater), ST-segment deviation, diabetes, serum creatinine, Peripheral artery occlusive disease, peripheral vascular disease, and elevation of cardiac markers.


Epidemiology

Myocardial infarction is a common presentation of
coronary artery disease Coronary artery disease (CAD), also called coronary heart disease (CHD), ischemic heart disease (IHD), or simply heart disease, involves the reduction of blood flow to the heart muscle Cardiac muscle (also called heart muscle or myocardium) is ...
. The World Health Organization estimated in 2004, that 12.2% of worldwide deaths were from ischemic heart disease; with it being the leading cause of death in high- or middle-income countries and second only to Lower respiratory tract infection, lower respiratory infections in developing country, lower-income countries. Worldwide, more than 3 million people have STEMIs and 4 million have NSTEMIs a year. STEMIs occur about twice as often in men as women. Rates of death from ischemic heart disease (IHD) have slowed or declined in most high-income countries, although cardiovascular disease still accounted for one in three of all deaths in the US in 2008. For example, rates of death from cardiovascular disease have decreased almost a third between 2001 and 2011 in the United States. In contrast, IHD is becoming a more common cause of death in the developing world. For example, in India, IHD had become the leading cause of death by 2004, accounting for 1.46 million deaths (14% of total deaths) and deaths due to IHD were expected to double during 1985–2015. Globally, disability adjusted life years (DALYs) lost to ischemic heart disease are predicted to account for 5.5% of total DALYs in 2030, making it the second-most-important cause of disability (after Major depressive disorder, unipolar depressive disorder), as well as the leading cause of death by this date.


Social determinants of health

Social determinants such as Neighbourhood, neighborhood disadvantage, immigration status, lack of social support, social isolation, access to Health care, health services play an important role in myocardial infarction risk and survival. Studies have shown that low socioeconomic status is associated with an increased risk of poorer survival. There are well-documented disparities in myocardial infarction survival by socioeconomic status, Race and ethnicity in the United States, race, education, and census-tract-level poverty. Race: In the U.S. African Americans have a greater burden of myocardial infarction and other cardiovascular events. On a population level, there is a higher overall prevalence of risk factors that are unrecognized and therefore not treated, which places these individuals at a greater likelihood of experiencing adverse outcomes and therefore potentially higher morbidity and Mortality rate, mortality. Socioeconomic status: Among individuals who live in the low-Socioeconomic status, socioeconomic (SES) areas, which is close to 25% of the US population, myocardial infarctions (MIs) occurred twice as often compared with people who lived in higher SES areas. Immigration status: In 2018 many lawfully present immigrants who are eligible for coverage remain uninsured because immigrant families face a range of enrollment barriers, including fear, confusion about eligibility policies, difficulty navigating the enrollment process, and language and literacy challenges. Uninsured Undocumented immigrants (U.S.), undocumented immigrants are ineligible for coverage options due to their immigration status. Health care access: Lack of health insurance and financial concerns about accessing care were associated with delays in seeking emergency care for acute myocardial infarction which can have significant, adverse consequences on patient outcomes. Education: Researchers found that compared to people with graduate degrees, those with lower educational attainment appeared to have a higher risk of heart attack, dying from a cardiovascular event, and overall death.


Society and culture

Depictions of heart attacks in popular media often include collapsing or loss of consciousness which are not common symptoms; these depictions contribute to widespread misunderstanding about the symptoms of myocardial infarctions, which in turn contributes to people not getting care when they should.


Legal implications

At common law, in general, a myocardial infarction is a disease, but may sometimes be an injury. This can create coverage issues in the administration of no-fault insurance schemes such as workers' compensation. In general, a heart attack is not covered;Workers' Compensation FAQ
. Prairie View A&M University. Retrieved November 22, 2006.
however, it may be a Industrial injury, work-related injury if it results, for example, from unusual emotional stress or unusual exertion.SIGNIFICANT DECISIONS Subject Index
. Board of Industrial Insurance Appeals. Retrieved November 22, 2006.
In addition, in some jurisdictions, heart attacks suffered by persons in particular occupations such as police officers may be classified as line-of-duty injuries by statute or policy. In some countries or states, a person having suffered from an MI may be prevented from participating in activity that puts other people's lives at risk, for example driving a car or flying an airplane.


References


Sources

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Further reading

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External links

*
American Heart Association's Heart Attack web site
— Information and resources for preventing, recognizing, and treating a heart attack. * TIMI Score fo
UA/NSTEMI
an
STEMI

HEART Score for Major Cardiac Events
* {{Authority control Aging-associated diseases Causes of death Ischemic heart diseases Medical emergencies Articles containing video clips Wikipedia medicine articles ready to translate Acute pain Wikipedia emergency medicine articles ready to translate