Nucleosides are glycosylamines that can be thought of as nucleotides without a phosphate group . A nucleoside consists simply of a nucleobase (also termed a nitrogenous base) and a five-carbon sugar ( ribose or 2'-deoxyribose) whereas a nucleotide is composed of a nucleobase, a five-carbon sugar, and one or more phosphate groups. In a nucleoside, the anomeric carbon is linked through a glycosidic bond to the N9 of a purine or the N1 of a pyrimidine . Nucleotides are the molecular building blocks of DNA and RNA .
87-470: (adenosine may be safe to the fetus in pregnant women) Adenosine ( symbol A ) is an organic compound that occurs widely in nature in the form of diverse derivatives. The molecule consists of an adenine attached to a ribose via a β-N 9 - glycosidic bond . Adenosine is one of the four nucleoside building blocks of RNA (and its derivative deoxyadenosine is a building block of DNA ), which are essential for all life on Earth. Its derivatives include
174-411: A blood test for biomarkers (the cardiac protein troponin ). 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 . The phrase "heart attack" is often used non-specifically to refer to myocardial infarction. An MI is different from—but can cause— cardiac arrest , where
261-658: A cold sweat , feeling tired , and decreased level of consciousness . 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 , an irregular heartbeat , cardiogenic shock or cardiac arrest . Most MIs occur due to coronary artery disease . Risk factors include high blood pressure , smoking , diabetes , lack of exercise , obesity , high blood cholesterol , poor diet, and excessive alcohol intake . The complete blockage of
348-475: A coronary artery caused by a rupture of an atherosclerotic plaque is usually the underlying mechanism of an MI. MIs are less commonly caused by coronary artery spasms , which may be due to cocaine , significant emotional stress (often known as Takotsubo syndrome or broken heart syndrome ) and extreme cold, among others. Many tests are helpful to help with diagnosis, including electrocardiograms (ECGs), blood tests and coronary angiography . An ECG, which
435-534: A purine structure and bind to some of the same receptors as adenosine. Methylxanthines act as competitive antagonists of adenosine and can blunt its pharmacological effects. Individuals taking large quantities of methylxanthines may require increased doses of adenosine. Caffeine acts by blocking binding of adenosine to the adenosine A 1 receptor , which enhances release of the neurotransmitter acetylcholine . Caffeine also increases cyclic AMP levels through nonselective inhibition of phosphodiesterase. "Caffeine has
522-474: A benefit of 15 to 45%. 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 quitting smoking reduce the risk of cardiovascular disease. Substituting unsaturated fats such as olive oil and rapeseed oil instead of saturated fats may reduce
609-428: A common, and sometimes the only symptom, occurring when damage to the heart limits the output of the left ventricle , with breathlessness arising either from low oxygen in the blood or pulmonary edema . Other less common symptoms include weakness, light-headedness , palpitations , and abnormalities in heart rate or blood pressure . These symptoms are likely induced by a massive surge of catecholamines from
696-498: A dose of 12 mg can be given 1–2 minutes after the first dose. When given to dilate the arteries, such as in a "stress test", the dosage is typically 0.14 mg/kg/min, administered for 4 or 6 minutes, depending on the protocol. The recommended dose may be increased in patients on theophylline since methylxanthines prevent binding of adenosine at receptor sites. The dose is often decreased in patients on dipyridamole (Persantine) and diazepam (Valium) because adenosine potentiates
783-480: 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. 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 , possible causes for
870-410: A mechanism that requires the adenosine A 2A receptor. Adenosine has been shown to promote thickening of hair on people with thinning hair. A 2013 study compared topical adenosine with minoxidil in male androgenetic alopecia , finding it was as potent as minoxidil (in overall treatment outcomes) but with higher satisfaction rate with patients due to “faster prevention of hair loss and appearance of
957-431: 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 21, which contains genes CDKN2A and 2B, although
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#17327798392511044-463: 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. One analysis has found an increase in heart attacks immediately following
1131-406: A myocardial infarction. Spasm of coronary arteries, such as Prinzmetal's angina may cause blockage. 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 ( infarction ), chiefly through necrosis , and do not grow back. A collagen scar forms in their place. When an artery
1218-543: 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 , sestamibi ( MIBI scans ) or tetrofosmin ; or a PET scan using 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
1305-637: A person localizes the chest pain by clenching one or both fists over their sternum , has classically been thought to be predictive of cardiac chest pain, although a prospective observational study showed it had a poor positive predictive value . Typically, chest pain because of ischemia, be it unstable angina or myocardial infarction, lessens with the use of nitroglycerin , but nitroglycerin may also relieve chest pain arising from non-cardiac causes. Chest pain may be accompanied by sweating , nausea or vomiting, and fainting , and these symptoms may also occur without any pain at all. Dizziness or lightheadedness
1392-407: 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, and pain might be absent altogether. Levine's sign , in which
1479-587: A radical in the radical SAM enzymes. In individuals with supraventricular tachycardia (SVT), adenosine is used to help identify and convert the rhythm. Certain SVTs can be successfully terminated with adenosine. This includes any re-entrant arrhythmias that require the AV node for the re-entry, e.g., AV reentrant tachycardia (AVRT) and AV nodal reentrant tachycardia (AVNRT). In addition, atrial tachycardia can sometimes be terminated with adenosine. Fast rhythms of
1566-560: A rise in biomarkers, a rise in the ST segment , changes in the shape or flipping of T waves , new Q waves , or a new left bundle branch block can be used to diagnose an AMI. In addition, ST elevation 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 adjacent chest or limb leads . ST elevation
1653-409: 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 produce a waveform with different labeled features. In addition to
1740-406: A significant effect on blood cholesterol and thus recommendations about its consumption may not be needed. Trans fats 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. Family history of ischemic heart disease or MI, particularly if one has a male first-degree relative (father, brother) who had
1827-652: A three-dimensional structure similar to that of adenosine," which allows it to bind and block its receptors. Common contraindications for adenosine include Adenosine is an endogenous purine nucleoside that modulates many physiological processes. Cellular signaling by adenosine occurs through four known adenosine receptor subtypes ( A 1 , A 2A , A 2B , and A 3 ). Extracellular adenosine concentrations from normal cells are approximately 300 nM; however, in response to cellular damage (e.g., in inflammatory or ischemic tissue), these concentrations are quickly elevated (600–1,200 nM). Thus, in regard to stress or injury,
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#17327798392511914-601: Is a known risk factor, particularly high low-density lipoprotein , low high-density lipoprotein , and high triglycerides . Many risk factors for myocardial infarction are potentially modifiable, with the most important being tobacco smoking (including secondhand smoke ). Smoking appears to be the cause of about 36% and obesity the cause of 20% of coronary artery disease . Lack of physical activity has been linked to 7–12% of cases. Less common causes include stress-related causes such as job stress , which accounts for about 3% of cases, and chronic high stress levels. There
2001-454: Is a recording of the heart's electrical activity, may confirm an ST elevation MI ( STEMI ), if ST elevation is present. Commonly used blood tests include troponin and less often creatine kinase MB . Treatment of an MI is time-critical. Aspirin is an appropriate immediate treatment for a suspected MI. Nitroglycerin or opioids may be used to help with chest pain; however, they do not improve overall outcomes. Supplemental oxygen
2088-806: Is also an important modifiable risk. Short-term exposure to air pollution such as carbon monoxide , nitrogen dioxide , and sulfur dioxide (but not ozone ) has 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. Myocardial infarction can also occur as
2175-499: 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 or ventricular fibrillation . Noninvasive imaging plays an important role in
2262-525: Is believed to be an anti-inflammatory agent at the A 2A receptor. Topical treatment of adenosine to foot wounds in diabetes mellitus has been shown in lab animals to drastically increase tissue repair and reconstruction. Topical administration of adenosine for use in wound-healing deficiencies and diabetes mellitus in humans is currently under clinical investigation. Methotrexate 's anti-inflammatory effect may be due to its stimulation of adenosine release. In general, adenosine has an inhibitory effect in
2349-517: Is blocked, cells lack oxygen , needed to produce 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,
2436-433: Is common and occurs due to reduction in oxygen and blood to the brain. In females, the most common symptoms of myocardial infarction include shortness of breath, weakness, and fatigue . Females are more likely to have unusual or unexplained tiredness and nausea or vomiting as symptoms. Females having heart attacks are more likely to have palpitations, back pain, labored breath, vomiting, and left arm pain than males, although
2523-528: Is considered a class V antiarrhythmic agent . When adenosine is used to cardiovert an abnormal rhythm, it is normal for the heart to enter ventricular asystole for a few seconds. This can be disconcerting to a normally conscious patient, and is associated with angina-like sensations in the chest. Adenosine is used as an adjunct to thallium (TI 201) or technetium (Tc99m) myocardial perfusion scintigraphy (nuclear stress test) in patients unable to undergo adequate stress testing with exercise. When given for
2610-418: Is considered one of the most effective treatments for insomnia , utilizes short-term sleep deprivation to raise and regulate adenosine levels in the body, for the intended promotion of consistent and sustained sleep in the long term. A principal component of cannabis delta-9-tetrahydrocannabinol (THC) and the endocannabinoid anandamide (AEA) induces sleep in rats by increasing adenosine levels in
2697-442: Is found inside the artery walls. This causes dilation of the "normal" segments of arteries, i.e. where the endothelium is not separated from the tunica media by atherosclerotic plaque . This feature allows physicians to use adenosine to test for blockages in the coronary arteries, by exaggerating the difference between the normal and abnormal segments. The administration of adenosine also reduces blood flow to coronary arteries past
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2784-477: 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, a fast heart rate , hyperthyroidism , too few red blood cells in the bloodstream , or low blood pressure . Damage or failure of procedures such as percutaneous coronary intervention (PCI) or coronary artery bypass grafts (CABG) may cause
2871-430: Is one of the most common symptoms 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 pain most suggestive of an acute MI, with the highest likelihood ratio , is pain radiating to the right arm and shoulder. Similarly, chest pain similar to
2958-497: Is possible other pathways exist. When adenosine enters the circulation, it is broken down by adenosine deaminase , which is present in red blood cells and the vessel wall. Dipyridamole , an inhibitor of adenosine nucleoside transporter , allows adenosine to accumulate in the blood stream. This causes an increase in coronary vasodilatation . Adenosine deaminase deficiency is a known cause of immunodeficiency. The adenosine analog NITD008 has been reported to directly inhibit
3045-414: 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 (PCI), where the arteries are pushed open and may be stented , or thrombolysis , where the blockage is removed using medications. People who have a non-ST elevation myocardial infarction ( NSTEMI ) are often managed with
3132-412: 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. 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: A myocardial infarction
3219-491: Is unable to induce the secretion of growth hormone and increase its plasma levels. When it is administered intravenously, adenosine causes transient heart block in the atrioventricular (AV) node . This is mediated via the A 1 receptor , inhibiting adenylyl cyclase, reducing cAMP and so causing cell hyperpolarization by increasing K efflux via inward rectifier K channels , subsequently inhibiting Ca current. It also causes endothelial-dependent relaxation of smooth muscle as
3306-457: Is usually clinically classified as an ST-elevation MI (STEMI) or a non-ST elevation MI (NSTEMI). These are based on ST elevation , a portion of a heartbeat graphically recorded on an 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: There are many different biomarkers used to determine
3393-445: Is varying evidence about the importance of saturated fat in the development of myocardial infarctions. Eating polyunsaturated fat instead of saturated fats 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 intake affects heart attack risk. Dietary cholesterol does not appear to have
3480-515: The basal forebrain . These components also significantly increase slow-wave sleep during the sleep cycle , mediated by CB1 receptor activation . These findings identify a potential therapeutic use of cannabinoids to induce sleep in conditions where sleep may be severely attenuated. It also plays a role in regulation of blood flow to various organs through vasodilation . Nucleoside#List of nucleosides and corresponding nucleobases This list does not include modified nucleobases and
3567-514: The central nervous system (CNS). Caffeine 's stimulatory effects are credited primarily (although not entirely) to its capacity to block adenosine receptors, thereby reducing the inhibitory tonus of adenosine in the CNS. This reduction in adenosine activity leads to increased activity of the neurotransmitters dopamine and glutamate . Experimental evidence suggests that adenosine and adenosine agonists can activate Trk receptor phosphorylation through
Adenosine - Misplaced Pages Continue
3654-414: The coronary arteries of the heart , causing infarction (tissue death) to the heart muscle . The most common symptom is retrosternal chest pain or discomfort that classically radiates to the left shoulder, arm, or jaw. The pain may occasionally feel like heartburn . This is the dangerous type of Acute coronary syndrome . Other symptoms may include shortness of breath , nausea , feeling faint ,
3741-661: The elderly , in those with diabetes mellitus and after heart transplantation . In people with diabetes, differences in pain threshold , autonomic neuropathy , and psychological factors have been cited as possible explanations for the lack of symptoms. In heart transplantation, the donor heart is not fully innervated by the nervous system of the recipient. The most prominent risk factors for myocardial infarction are older age, actively smoking , high blood pressure , diabetes mellitus , and total cholesterol and high-density lipoprotein levels. Many risk factors of myocardial infarction are shared with coronary artery disease ,
3828-480: 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 , body mass index and waist circumference . However, there was insufficient evidence to show an effect on mortality or actual cardio-vascular events. Statins , drugs that act to lower blood cholesterol, decrease
3915-522: 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 , LPA , TCF21 , MTHFDSL , ZC3HC1 , CDKN2A , 2B , ABO , PDGF0 , APOA5 , MNF1ASM283 , COL4A1 , HHIPC1 , SMAD3 , ADAMTS7 , RAS1 , SMG6 , SNF8 , LDLR , SLC5A3 , MRPS6 , KCNE2 . The risk of having
4002-481: 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
4089-551: The sympathetic nervous system , which occurs in response to pain and, where present, low blood pressure . Loss of consciousness can occur in myocardial infarctions due to inadequate blood flow to the brain and cardiogenic shock , and sudden death , frequently due to the development of ventricular fibrillation . When the brain was without oxygen for too long due to a myocardial infarction, coma and persistent vegetative state can occur. Cardiac arrest, and atypical symptoms such as palpitations , occur more frequently in females,
4176-410: The A 2 adenosine receptors couple to G s , which stimulates adenylate cyclase activity. In addition, A 1 receptors couple to G o , which has been reported to mediate adenosine inhibition of Ca conductance, whereas A 2B and A 3 receptors also couple to G q and stimulate phospholipase activity. Researchers at Cornell University have recently shown adenosine receptors to be key in opening
4263-537: The United States. In the developed world, the risk of death in those who have had a 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. Myocardial infarction (MI) refers to tissue death ( infarction ) of
4350-432: The acute diagnostic algorithm; however, it can confirm a clinical suspicion of Chronic Coronary Syndrome when the patient's history, physical examination (including cardiac examination ) ECG, and cardiac biomarkers suggest coronary artery disease. 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
4437-409: The affected artery, totality of the blockage, duration of the blockage, the presence of 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 put a person at risk of abnormal heart rhythms (arrhythmias) or heart block , aneurysm of
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#17327798392514524-647: The blood thinner 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 (CABG) may be recommended rather than angioplasty . After an MI, lifestyle modifications, along with long-term treatment with aspirin, beta blockers and statins , 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
4611-502: The blood-brain barrier (BBB). Mice dosed with adenosine have shown increased transport across the BBB of amyloid plaque antibodies and prodrugs associated with Parkinson's disease, Alzheimer's, multiple sclerosis, and cancers of the central nervous system. Adenosine is an endogenous agonist of the ghrelin/growth hormone secretagogue receptor . However, while it is able to increase appetite , unlike other agonists of this receptor, adenosine
4698-484: The cell into nitrogenous bases , and ribose-1-phosphate or deoxyribose-1-phosphate . In medicine several nucleoside analogues are used as antiviral or anticancer agents. The viral polymerase incorporates these compounds with non-canonical bases. These compounds are activated in the cells by being converted into nucleotides. They are administered as nucleosides since charged nucleotides cannot easily cross cell membranes. In molecular biology, several analogues of
4785-414: The corresponding nucleosides Each chemical has a short symbol, useful when the chemical family is clear from the context, and a longer symbol, if further disambiguation is needed. For example, long nucleobase sequences in genomes are usually described by CATG symbols, not Cyt-Ade-Thy-Gua (see Nucleic acid sequence § Notation ). Nucleosides can be produced from nucleotides de novo , particularly in
4872-405: 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. Echocardiography may assist in modifying clinical suspicion of ongoing myocardial infarction in patients that can't be ruled out or ruled in following initial ECG and Troponin testing. Myocardial perfusion imaging has no role in
4959-616: 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. Electrocardiograms (ECGs) are
5046-461: The direct condensation of nucleobases with ribose to give ribonucleosides in aqueous microdroplets, a key step leading to RNA formation. Also, a plausible prebiotic process for synthesizing pyrimidine and purine ribonucleosides and ribonucleotides using wet-dry cycles was presented by Becker et al. Myocardial infarction A myocardial infarction ( MI ), commonly known as a heart attack , occurs when blood flow decreases or stops in one of
5133-466: The effects of these drugs. The recommended dose is also reduced by half in patients presenting congestive heart failure , myocardial infarction , shock , hypoxia , and/or chronic liver disease or chronic kidney disease , and in elderly patients. Dipyridamole potentiates the action of adenosine, requiring the use of lower doses. Methylxanthines (e.g. caffeine found in coffee, theophylline found in tea, or theobromine found in chocolate) have
5220-414: The elderly, those with diabetes, in people who have just had surgery, and in critically ill patients. "Silent" myocardial infarctions can happen without any symptoms at all. These cases can be discovered later on electrocardiograms , using blood enzyme tests, or at autopsy after a person has died. Such silent myocardial infarctions represent between 22 and 64% of all infarctions, and are more common in
5307-487: The energy carriers adenosine mono-, di-, and triphosphate , also known as AMP/ADP/ATP. Cyclic adenosine monophosphate (cAMP) is pervasive in signal transduction . Adenosine is used as an intravenous medication for some cardiac arrhythmias . Adenosyl (abbreviated Ado or 5'-dAdo ) is the chemical group formed by removal of the 5′-hydroxy (OH) group. It is found in adenosylcobalamin (an active form of vitamin B12 ) and as
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#17327798392515394-541: The evaluation or treatment of a supraventricular tachycardia (SVT), the initial dose is 6 mg to 12 mg, depending on standing orders or provider preference, given as a rapid parenteral infusion . Due to adenosine's extremely short half-life, the IV line is started as proximal (near) to the heart as possible, such as the antecubital fossa . The IV push is often followed with a flush of 10–20 mL of normal saline. If this has no effect (i.e., no evidence of transient AV block),
5481-676: The function of adenosine is primarily that of cytoprotection preventing tissue damage during instances of hypoxia , ischemia , and seizure activity. Activation of A 2A receptors produces a constellation of responses that in general can be classified as anti-inflammatory. Enzymatic production of adenosine can be anti- inflammatory or immunosuppressive . All adenosine receptor subtypes (A 1 , A 2A , A 2B , and A 3 ) are G-protein-coupled receptors . The four receptor subtypes are further classified based on their ability to either stimulate or inhibit adenylate cyclase activity. The A 1 receptors couple to G i/o and decrease cAMP levels, while
5568-637: The greatest support is the Mediterranean diet . Vitamins and mineral supplements are of no proven benefit, and neither are plant stanols or 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
5655-465: The heart is not contracting at all or so poorly that all vital organs cease to function, thus leading to death. It is also distinct from heart failure , in which the pumping action of the heart is impaired. However, an MI may lead to heart failure. 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. Chest pain
5742-410: The heart muscle ( myocardium ) caused by ischemia , the lack of oxygen delivery to myocardial tissue. It is a type of acute coronary syndrome , 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 , a myocardial infarction occurs when there is cell death , which can be estimated by measuring by
5829-430: The heart that are confined to the atria (e.g., atrial fibrillation and atrial flutter ) or ventricles (e.g., monomorphic ventricular tachycardia ), and do not involve the AV node as part of the re-entrant circuit, are not typically converted by adenosine. However, the ventricular response rate is temporarily slowed with adenosine in such cases. Because of the effects of adenosine on AV node-dependent SVTs, adenosine
5916-441: The heart ventricles , 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
6003-729: The heart, lungs , gastrointestinal tract , aorta , and other muscles, bones and nerves surrounding the chest. In addition to myocardial infarction, other causes include 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 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 . Causes of sudden-onset breathlessness generally involve
6090-402: 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
6177-574: The key building blocks of life under plausible prebiotic conditions . According to the RNA world hypothesis free-floating ribonucleosides and ribonucleotides were present in the primitive soup. Molecules as complex as RNA must have arisen from small molecules whose reactivity was governed by physico-chemical processes. RNA is composed of purine and pyrimidine nucleotides, both of which are necessary for reliable information transfer, and thus Darwinian natural selection and evolution . Nam et al. demonstrated
6264-461: The liver, but they are more abundantly supplied via ingestion and digestion of nucleic acids in the diet, whereby nucleotidases break down nucleotides (such as the thymidine monophosphate ) into nucleosides (such as thymidine ) and phosphate. The nucleosides, in turn, are subsequently broken down in the lumen of the digestive system by nucleosidases into nucleobases and ribose or deoxyribose. In addition, nucleotides can be broken down inside
6351-666: The lungs or heart – including pulmonary edema , pneumonia, allergic reactions and asthma , and pulmonary embolus, acute respiratory distress syndrome and metabolic acidosis . There are many different causes of fatigue, and myocardial infarction is not a common cause. 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
6438-610: The myocardial infarction are coronary spasm or coronary artery dissection . 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 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 and fibrous tissue in plaques in
6525-409: The newly grown hairs” (further trials were called for to clarify the findings). Adenosine is a key factor in regulating the body's sleep-wake cycle . Adenosine levels rise during periods of wakefulness and lowers during sleep. Higher adenosine levels correlate with a stronger feeling of sleepiness , also known as sleep drive or sleep pressure. Cognitive behavioral therapy for insomnia (CBT-I), which
6612-400: The non-canonical sugar dideoxyribose, which lacks 3' hydroxyl group (which accepts the phosphate). DNA polymerases cannot distinguish between these and regular deoxyribonucleotides, but when incorporated a dideoxynucleotide cannot bond with the next base and the chain is terminated. In order to understand how life arose, knowledge is required of the chemical pathways that permit formation of
6699-437: The occlusion. Other coronary arteries dilate when adenosine is administered while the segment past the occlusion is already maximally dilated, which is a process called coronary steal . This leads to less blood reaching the ischemic tissue, which in turn produces the characteristic chest pain. Adenosine used as a second messenger can be the result of de novo purine biosynthesis via adenosine monophosphate (AMP), though it
6786-419: The physician confirm a person is at high risk for Chronic Coronary Syndrome before conducting diagnostic non-invasive 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, most likely do not merit routine imaging. There are many causes of chest pain , which can originate from
6873-471: 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. Atherosclerotic disease
6960-487: 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
7047-512: The primary cause of myocardial infarction, with other risk factors including male sex, low levels of physical activity, a past family history , obesity , and alcohol use . Risk factors for myocardial disease are often included in risk factor stratification scores, such as the Framingham Risk Score . At any given age, men are more at risk than women for the development of cardiovascular disease. High levels of blood cholesterol
7134-548: The recombinant RNA-dependent RNA polymerase of the dengue virus by terminating its RNA chain synthesis. This interaction suppresses peak viremia and rise in cytokines and prevents lethality in infected animals, raising the possibility of a new treatment for this flavivirus . The 7-deaza-adenosine analog has been shown to inhibit the replication of the hepatitis C virus . BCX4430 is protective against Ebola and Marburg viruses. Such adenosine analogs are potentially clinically useful since they can be taken orally. Adenosine
7221-486: 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 nuts , seeds , or legumes per week. The dietary pattern with
7308-399: 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
7395-400: The studies showing these differences had high variability. Females 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. Females with heart attacks also had more indigestion, dizziness , loss of appetite , and loss of consciousness. Shortness of breath is
7482-420: The sugar backbone exist. Due to the low stability of RNA, which is prone to hydrolysis, several more stable alternative nucleoside/nucleotide analogues that correctly bind to RNA are used. This is achieved by using a different backbone sugar. These analogues include locked nucleic acids (LNA), morpholinos and peptide nucleic acids (PNA). In sequencing, dideoxynucleotides are used. These nucleotides possess
7569-529: The wall of the 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 cholesterol core forms as foam cells die. In response to growth factors secreted by macrophages, smooth muscle and other cells move into
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