Atrial fibrillation
Classification & external resources

The P waves, which represent depolarization of the atria, are irregular or absent during atrial fibrillation.
ICD-10	I48.
ICD-9	427.31
DiseasesDB	1065
MedlinePlus	000184
eMedicine	med/184  emerg/46

Atrial fibrillation (AF or afib) is a cardiac arrhythmia (abnormal heart rhythm) that involves the two upper chambers (atria) of the heart. It is defined as being irregularly irregular, and can often be identified as such when taking a pulse. Atrial fibrillation is the most common arrhythmia; risk increases with age, with 8% of people over 80 having AF. In atrial fibrillation, the electrical impulses that are normally generated by the sinoatrial node are replaced by disorganized activity in the atria, leading to irregular conduction of impulses to the ventricles that generate the heartbeat. The result is an irregular heartbeat. This may be continuous (persistent or permanent AF) or alternating between periods of a normal heart rhythm (paroxysmal AF). The natural tendency of atrial fibrillation is to become a chronic condition. Chronic AF leads to an increased risk of death.^[1] Image File history File links SinusRhythmLabels. ... The International Statistical Classification of Diseases and Related Health Problems (most commonly known by the abbreviation ICD) provides codes to classify diseases and a wide variety of signs, symptoms, abnormal findings, complaints, social circumstances and external causes of injury or disease. ... The International Statistical Classification of Diseases and Related Health Problems 10th Revision (ICD-10) is a coding of diseases and signs, symptoms, abnormal findings, complaints, social circumstances and external causes of injury or diseases, as classified by the World Health Organization (WHO). ... // I00-I99 - Diseases of the circulatory system (I00-I02) Acute rheumatic fever (I00) Rheumatic fever without mention of heart involvement (I01) Rheumatic fever with heart involvement (I02) Rheumatic chorea (I05-I09) Chronic rheumatic heart diseases (I05) Rheumatic mitral valve diseases (I050) Mitral stenosis (I051) Rheumatic mitral insufficiency (I06) Rheumatic aortic... The International Statistical Classification of Diseases and Related Health Problems (most commonly known by the abbreviation ICD) provides codes to classify diseases and a wide variety of signs, symptoms, abnormal findings, complaints, social circumstances and external causes of injury or disease. ... The following is a list of codes for International Statistical Classification of Diseases and Related Health Problems. ... The Disease Bold textDatabase is a free website that provides information about the relationships between medical conditions, symptoms, and medications. ... MedlinePlus (medlineplus. ... eMedicine is an online clinical medical knowledge base that was founded in 1996. ... Cardiac arrhythmia is any of a group of conditions in which the electrical activity of the heart is irregular or is faster or slower than normal. ... In anatomy, the atrium (plural: atria) is the blood collection chamber of a heart. ... The heart and lungs, from an older edition of Grays Anatomy. ... ˌ For other uses, see Pulse (disambiguation). ... The sinoAtrial node (abbreviated SA node or SAN, also called the sinus node) is the impulse generating (pacemaker) tissue located in the right atrium of the heart, and thus the generator of sinus rhythm. ... In the heart, a ventricle is a heart chamber which collects blood from an atrium (another heart chamber that is smaller than a ventricle) and pumps it out of the heart. ...

Atrial fibrillation is often asymptomatic, and is not in itself generally life-threatening, but may result in palpitations, fainting, chest pain, or congestive heart failure. Patients with atrial fibrillation are at significantly increased chance of stroke (about 2 to 7 times the regular population), and AF is a leading cause of stroke.^[2] A palpitation is an abnormal, rapid beating of the heart, brought on by overexertion, disease or drugs. ... It has been suggested that Central Ischaemic Response be merged into this article or section. ... angina tonsillaris see tonsillitis. ... Congestive heart failure (CHF), also called congestive cardiac failure (CCF) or just heart failure, is a condition that can result from any structural or functional cardiac disorder that impairs the ability of the heart to fill with or pump a sufficient amount of blood throughout the body. ... For other uses, see Stroke (disambiguation). ...

Atrial fibrillation may be treated with medications which either slow the heart rate or revert the heart rhythm back to normal. Synchronized electrical cardioversion may also be used to convert AF to a normal heart rhythm. Surgical and catheter-based therapies may also be used to prevent recurrence of atrial fibrillation in certain individuals. People with AF are often given anticoagulants such as warfarin to protect them from stroke. Through electricity or drug therapy, cardioversion converts heart arrhythmias to normal rhythms. ... An anticoagulant is a substance that prevents coagulation; that is, it stops blood from clotting. ... Warfarin (also known under the brand names of Coumadin, Jantoven, Marevan, and Waran) is an anticoagulant medication that is administered orally or, very rarely, by injection. ...

Classification

The American Heart Association, American College of Cardiology, and the European Society of Cardiology have proposed the following classification system based on simplicity and clinical relevance.^[3] The American Heart Association (AHA) is a non-profit organization in the United States that fosters appropriate cardiac care in an effort to reduce disability and deaths caused by cardiovascular disease and stroke American Stroke Association Web site. ... Categories: Organization stubs | Medical associations ... The European Society of Cardiology (ESC) represents more than 50,000 cardiology professionals across Europe and the Mediterranean. ...

• First detected atrial fibrillation: any patient newly diagnosed with atrial fibrillation fits in this category, as the exact onset and chronicity of the disease is often uncertain.
• Recurrent atrial fibrillation: any patient with 2 or more identified episodes of atrial fibrillation is said to have recurrent atrial fibrillation. This is further classified into paroxysmal and persistent based on when the episode terminates without therapy. Atrial fibrillation is said to be paroxysmal when it terminates spontaneously within 7 days, most commonly within 24 hours. Persistent or chronic atrial fibrillation is AF established for more than seven days. Differentiation of paroxysmal from chronic or established AF is based on the history of recurrent episodes and the duration of the current episode of AF.^[3][4][5]
• Lone atrial fibrillation (LAF) is defined as atrial fibrillation in the absence of clinical or echocardiographic findings of cardiopulmonary disease.^[3] Patients with LAF who are under 65 have the best prognosis.

Signs and symptoms

Atrial fibrillation is usually accompanied by symptoms related to the rapid heart rate. Rapid and irregular heart rates may be perceived as palpitations, exercise intolerance, and occasionally produce angina (if the rate is faster and puts the heart under strain) and congestive symptoms of shortness of breath or edema. Sometimes the arrhythmia will be identified only with the onset of a stroke or a transient ischemic attack (TIA, stroke symptoms resolving within 24 hours). It is not uncommon to identify atrial fibrillation on a routine physical examination or electrocardiogram (ECG/EKG), as it may be asymptomatic in many cases.^[3] A palpitation is an abnormal, rapid beating of the heart, brought on by overexertion, disease or drugs. ... angina tonsillaris see tonsillitis. ... Congestive heart failure (CHF), also called congestive cardiac failure (CCF) or just heart failure, is a condition that can result from any structural or functional cardiac disorder that impairs the ability of the heart to fill with or pump a sufficient amount of blood through the body. ... Dyspnea (Latin dyspnoea, Greek dyspnoia from dyspnoos - short of breath) or shortness of breath (SOB) is perceived difficulty breathing or pain on breathing. ... This page is about the condition called edema. ... A transient ischemic attack (TIA, often colloquially referred to as mini stroke) is caused by the temporary disturbance of blood supply to a restricted area of the brain, resulting in brief neurologic dysfunction that usually persists for less than 24 hours. ... “QRS” redirects here. ...

As most cases of atrial fibrillation are secondary to other medical problems, the presence of chest pain or angina, symptoms of hyperthyroidism (an overactive thyroid gland) such as weight loss and diarrhea, and symptoms suggestive of lung disease would indicate an underlying cause. A previous history of stroke or TIA, as well as hypertension (high blood pressure), diabetes, heart failure and rheumatic fever, may indicate whether someone with atrial fibrillation is at a higher risk of complications.^[3] In medicine, chest pain is a symptom of a number of conditions and is generally considered a medical emergency, unless the patient is a known angina pectoris sufferer and the symptoms are familiar (appearing at exertion and resolving at rest, known as stable angina). When the chest pain is not... The latin word angina refers to a painful constriction or tightness somewhere in the body. ... Hyperthyroidism (or overactive thyroid gland) is the clinical syndrome caused by an excess of circulating free thyroxine (T4) or free triiodothyronine (T3), or both. ... The thyroid gland and its relations In anatomy, the thyroid (IPA θaɪɹoɪd) is an endocrine gland. ... Weight loss, in the context of medicine or health or physical fitness, is a reduction of the total body weight, due to a mean loss of fluid, body fat or adipose tissue and/or lean mass, namely bone mineral deposits, muscle, tendon and other connective tissue. ... Diarrhea, also spelled diarrhoea (see spelling differences), is a condition in which the sufferer has frequent watery, loose bowel movements (from the Greek word διάρροια; literally meaning through-flowing). Acute infectious diarrhea is a common cause of death in developing countries (particularly among infants), accounting for 5 to 8 million deaths... For other forms of hypertension, see Hypertension (disambiguation). ... For the disease characterized by excretion of large amounts of very dilute urine, see diabetes insipidus. ... Rheumatic fever is an inflammatory disease which may develop after a Group A streptococcal infection (such as strep throat or scarlet fever) and can involve the heart, joints, skin, and brain. ...

Diagnosis

The evaluation of atrial fibrillation involves diagnosis, determination of the etiology of the arrhythmia, and classification of the arrhythmia. A minimal evaluation performed should be performed in all individuals with atrial fibrillation. This includes a history and physical examination, surface electrocardiogram, transthoracic echocardiogram, and routine bloodwork. Certain individuals may benefit from an extended evaluation which may include an evaluation of the heart rate response to exercise, exercise stress testing, a chest x-ray, trans-esophageal echocardiography, and other studies.

Screening

Screening for atrial fibrillation is not generally performed, although a study of routine pulse checks or electrocardiograms during routine office visits, found that the annual rate of detection of atrial fibrillation in elderly patients improved from 1.04% to 1.63%; selection of patients for prophylactic anticoagulation would improve stroke risk in that age category.^[6] Screening, in medicine, is a strategy used to identify disease in an unsuspecting population. ... Lead II An electrocardiogram (ECG or EKG, abbreviated from the German Elektrokardiogramm) is a graphic produced by an electrocardiograph, which records the electrical voltage in the heart in the form of a continuous strip graph. ...

Routine primary care visit

This estimated sensitivity of the routine primary care visit is 64%. This low result probably reflects the pulse not being checked routinely or carefully.^[6] The sensitivity of a binary classification test or algorithm, such as a blood test to determine if a person has a certain disease, or an automated system to detect faulty products in a factory, is a parameter that expresses something about the tests performance. ...

Minimal evaluation

The minimal evaluation of atrial fibrillation should generally be performed in all individuals with atrial fibrillation. The goal of this evaluation is to determine the general treatment regimen for the individual. If results of the general evaluation warrant it, further studies may be then performed.

History and physical examination

The history of the individual's atrial fibrillation episodes is likely the most important part of the evaluation. Distinctions should be made to those who are entirely asymptomatic when they are in atrial fibrillation (in which case the atrial fibrillation is found as an incidental finding on an electrocardiogram or physical examination) and those who have gross and obvious symptoms due to atrial fibrillation and can pinpoint whenever they go into atrial fibrillation and revert to sinus rhythm.

Routine bloodwork

While many cases of AF have no definite cause, it may be the result of various other problems (see below). Hence, renal function and electrolytes are routinely determined, as well as thyroid-stimulating hormone (commonly suppressed in hyperthyroidism and of relevance if amiodarone is administered for treatment) and a blood count.^[3] In medicine (nephrology) renal function is an indication of the state of the kidney and its role in physiology. ... An electrolyte is a substance containing free ions that behaves as an electrically conductive medium. ... Thyroid-stimulating hormone (also known as TSH or thyrotropin) is a hormone synthesized and secreted by thyrotrope cells in the anterior pituitary gland which regulates the endocrine function of the thyroid gland. ... Hyperthyroidism (or overactive thyroid gland) is the clinical syndrome caused by an excess of circulating free thyroxine (T4) or free triiodothyronine (T3), or both. ... Amiodarone belongs to a class of drugs called Vaughan-Williams Class III antiarrhythmic agent. ... Schematics of shorthand for complete blood count commonly used by physicians. ...

In acute-onset AF associated with chest pain, cardiac troponins or other markers of damage to the heart muscle may be ordered. Coagulation studies (INR/aPTT) are usually performed, as anticoagulant medication may be commenced.^[3] In medicine, chest pain is a symptom of a number of conditions and is generally considered a medical emergency, unless the patient is a known angina pectoris sufferer and the symptoms are familiar (appearing at exertion and resolving at rest, known as stable angina). When the chest pain is not... Troponin Troponin is a complex of three proteins that is integral to muscle contraction in skeletal and cardiac muscle, but not smooth muscle. ... This article is about the clotting of blood. ... The prothrombin time (PT) and its derived measures of prothrombin ratio (PR) and international normalized ratio (INR) are measures of the extrinsic pathway of coagulation. ... An anticoagulant is a substance that prevents coagulation; that is, it stops blood from clotting. ...

Electrocardiogram

Main article: Electrocardiogram

ECG of atrial fibrillation (top) and sinus rhythm (bottom). The purple arrow indicates a P wave, which is lost in atrial fibrillation.

Atrial fibrillation is diagnosed on an electrocardiogram, an investigation performed routinely whenever irregular heart beat is suspected. Characteristic findings are the absence of P waves, with unorganized electrical activity in their place, and irregularity of R-R interval due to irregular conduction of impulses to the ventricles.^[3] “QRS” redirects here. ... Image File history File linksMetadata No higher resolution available. ... Image File history File linksMetadata No higher resolution available. ... “QRS” redirects here. ... “QRS” redirects here. ...

When electrocardiograms are used for screening, the SAFE trial found that electronic software, primary care physicians and the combination of the two had the following sensitivities and specificities:^[7]: A primary care physician, or PCP, is a physician who provides both the first contact for a person with an undiagnosed health concern as well as continuing care of varied medical conditions, not limited by cause, organ system, or diagnosis. ...

• Interpreted by software: sensitivity = 83%, specificity = 99%
• Interpreted by a primary care physician: sensitivity = 80%, specificity = 92%
• Interpreted by a primary care physician with software: sensitivity = 92%, specificity = 91%

If paroxysmal AF is suspected but the electrocardiogram shows a regular rhythm, episodes may be documented with the use of Holter monitoring (continuous ECG recording for 24 hours). If the symptoms are very infrequent, longer periods of continuous monitoring may be required.^[3] The sensitivity of a binary classification test or algorithm, such as a blood test to determine if a person has a certain disease, or an automated system to detect faulty products in a factory, is a parameter that expresses something about the tests performance. ... The specificity is a statistical measure of how well a binary classification test correctly identifies the negative cases, or those cases that do not meet the condition under study. ... “QRS” redirects here. ... Holter monitor In medicine, a Holter monitor (also called an ambulatory electrocardiography device), named after its inventor, Dr. Norman J. Holter, is a portable device for continuously monitoring the electrical activity of the heart for 24 hours or more. ...

Echocardiography

Main article: Echocardiogram

A transthoracic (non-invasive) echocardiogram is generally performed in newly diagnosed AF, as well as if there is a major change in the patient's clinical state. This ultrasound-based scan of the heart may help identify valvular heart disease (which may increase the risk of stroke manifold), left and right atrial size (which indicates likelihood that AF may become permanent), left ventricular size and function, peak right ventricular pressure (pulmonary hypertension), presence of left ventricular hypertrophy and pericardial disease.^[3] The echocardiogram is an ultrasound of the heart. ... The echocardiogram is an ultrasound of the heart. ... Wikipedia does not yet have an article with this exact name. ... In medicine, pulmonary hypertension (PH) is an increase in blood pressure in the pulmonary artery, pulmonary vein, or pulmonary capillaries, together known as the lung vasculature, leading to shortness of breath, dizziness, fainting, and other symptoms, all of which are exacerbated by exertion. ...

Significant enlargement of both the left and right atria is associated with long-standing atrial fibrillation and, if noted at the initial presentation of atrial fibrillation, suggests that the atrial fibrillation is likely of a longer duration than the individual's symptoms.

Extended evaluation

An extended evaluation is generally not necessary in most individuals with atrial fibrillation, and is only performed if abnormalities are noted in the limited evaluation, if a reversible cause of the atrial fibrillation is suggested, or if further evaluation may change the treatment course.

Chest X-ray

Main article: Chest X-ray

A chest X-ray is generally only performed if a pulmonary cause of atrial fibrillation is suggested. This may reveal an underlying problem in the lungs or the blood vessels in the chest. ^[3] In particular, if an underlying pneumonia is suggested, then treatment of the pneumonia may cause the atrial fibrillation to terminate on its own. Frontal chest X-ray. ... Frontal chest X-ray. ...

Transesophageal echocardiogram

A normal echocardiography (transthoracic or TTE) has a low sensitivity for identifying thrombi (blood clots) in the heart. If this is suspected - e.g. when planning urgent electrical cardioversion - a transesophageal echocardiogram (TEE) is preferred.^[3] For Trombe wall (used in solar homes), see Trombe wall. ... The echocardiogram is an ultrasound of the heart. ...

The TEE has much better visualization of the left atrial appendage than transthoracic echocardiography. This structure, located in the left atrium, is the place where thrombus most commonly is formed in the setting of atrial fibrillation or flutter. TEE has a very high sensitivity for locating thrombus in this area^{[citation needed]} and can also detect sluggish bloodflow in this area that is suggestive of thrombus formation.^{[citation needed]} The left auricular appendix (left auricula, left auricle) is a conical muscular pouch connected to the left atrium of the heart. ... Anterior (frontal) view of the opened heart. ...

If no thrombus is seen on TEE, the incidence of stroke immediately after cardioversion is performed is very low.^{[citation needed]}

Ambulatory holter monitoring

Main article: Holter monitor

A holter monitor is a wearable ambulatory heart monitor that continuously monitors the heart rate and heart rhythm for a short duration, typically 24 hours. In individuals with symptoms of significant shortness of breath with exertion or palpitations on a regular basis, a holter monitor may be of benefit to determine if rapid heart rates (or unusually slow heart rates) during atrial fibrillation are the cause of the symptoms. Holter monitor In medicine, a Holter monitor (also called an ambulatory electrocardiography device), named after its inventor, Dr. Norman J. Holter, is a portable device for continuously monitoring the electrical activity of the heart for 24 hours or more. ... Holter monitor In medicine, a Holter monitor (also called an ambulatory electrocardiography device), named after its inventor, Dr. Norman J. Holter, is a portable device for continuously monitoring the electrical activity of the heart for 24 hours or more. ...

Exercise stress testing

Main article: Cardiac stress test

Some individuals with atrial fibrillation do well with normal activity but develop shortness of breath with exertion. It may be unclear if the shortness of breath is due to a blunted heart rate response to exertion due to excessive AV node blocking agents, a very rapid heart rate during exertion, or due to other underlying conditions such as chronic lung disease or coronary ischemia. An exercise stress test will evaluate the individual's heart rate response to exertion and determine if the AV node blocking agents are contributing to the symptoms. A cardiac stress test is a medical test performed to evaluate relative arterial blood flow increases to the left ventricular heart muscle during exercise, as compared to resting blood flow rates (i. ... A cardiac stress test is a medical test performed to evaluate relative arterial blood flow increases to the left ventricular heart muscle during exercise, as compared to resting blood flow rates (i. ...

Etiology

AF is linked to several cardiac causes, but may occur in otherwise normal hearts. Known associations include:

• Hypertension (High blood pressure)
• Primary heart diseases including coronary artery disease, mitral stenosis (e.g. due to rheumatic heart disease or mitral valve prolapse), mitral regurgitation, hypertrophic cardiomyopathy (HCM), pericarditis, congenital heart disease, previous heart surgery
• Lung diseases (such as pneumonia, lung cancer, pulmonary embolism, sarcoidosis)
• Excessive alcohol consumption ("binge drinking" or "holiday heart syndrome")
• Hyperthyroidism
• Carbon monoxide poisoning
• Dual-chamber pacemakers in the presence of normal atrioventricular conduction.^[8]
• A family history of AF increases risk by 30%.^[9] Various genetic mutations may be responsible.^[10]

For other forms of hypertension, see Hypertension (disambiguation). ... Coronary heart disease (CHD), also called coronary artery disease (CAD) and atherosclerotic heart disease, is the end result of the accumulation of atheromatous plaques within the walls of the arteries that supply the myocardium (the muscle of the heart). ... Mitral stenosis is a narrowing of the orifice of the mitral valve of the heart. ... Rheumatic fever is an inflammatory disease which may develop after an infection with streptococcus bacteria (such as strep throat or scarlet fever) and can involve the heart, joints, skin, and brain. ... Mitral valve prolapse (MVP) is a heart valve condition marked by the displacement of an abnormally thickened mitral valve leaflet into the left atrium during systole. ... Mitral regurgitation (MR), also known as mitral insufficiency, is the abnormal leaking of blood through the mitral valve, from the left ventricle into the left atrium of the heart. ... Hypertrophic cardiomyopathy, or HCM, is a disease of the myocardium (the muscle of the heart) in which a portion of the myocardium is hypertrophied (thickened) without any obvious cause. ... Pericarditis is inflammation of the sac surrounding the heart, the pericardium. ... Cross-section diagram of a normal human heart. ... Cardiac surgery is surgery on the heart, typically to correct congenital heart disease or the complications of ischaemic heart disease or valve problems caused by endocarditis. ... This article is about human pneumonia. ... Lung cancer is the malignant transformation and expansion of lung tissue, and is the most lethal of all cancers worldwide, responsible for 1. ... Alcoholic beverages An alcoholic beverage (also known as booze in slang term) is a drink containing ethanol, commonly known as alcohol, although in chemistry the definition of alcohol includes many other compounds. ... Drinking too much alcohol may qualify as binge drinking if it leads to at least two days of inebriation and the drinker neglects usual responsibilities The British Medical Association states that there is no consensus on the definition of binge drinking. ... Holiday Heart Syndrome is a consequence of binge drinking. ... Hyperthyroidism (or overactive thyroid gland) is the clinical syndrome caused by an excess of circulating free thyroxine (T4) or free triiodothyronine (T3), or both. ... Carbon monoxide poisoning occurs after the inhalation of carbon monoxide gas. ... The term pacemaker has multiple meanings: In sports, a pacemaker or pacer is a competitor who enters an athletics race with little or no intention of winning, but purely to set a fast pace for other competitors to follow. ... Family history is the study of multiple generations of people who appear to be related. ...

Pathophysiology

Morphology

The primary pathophysiologic change seen in atrial fibrillation is the progressive fibrosis of the atria. This fibrosis is primarily due to atrial dilatation, however genetic causes and inflammation may have a cause in some individuals.

Dilatation of the atria can be due to most any structural abnormality of the heart that can cause a rise in the intra-cardiac pressures. This includes valvular heart disease (such as mitral stenosis, mitral regurgitation, and tricuspid regurgitation), hypertension, and congestive heart failure. Any inflammatory state that affects the heart can cause fibrosis of the atria. This is typically due to sarcoidosis but may also be due to autoimmune disorders that create autoantibodies against myosin heavy chains. Mutation of the lamin AC gene is also associated with fibrosis of the atria that can lead to atrial fibrillation. A lamin is a fibrous protein that gives the cell nucleus its shape. ...

Once dilatation of the atria has occurred, this begins a chain of events that leads to the activation of the renin aldosterone angiotensin system (RAAS) and subsequent increase in matrix metaloproteinases and disintegrin, which leads to atrial remodeling and fibrosis, with loss of atrial muscle mass. Schematic depicting how the RAAS works. ...

This process is not immediate, and experimental studies have revealed patchy atrial fibrosis may precede the occurrence of atrial fibrillation and may progress with prolonged durations of atrial fibrillation.

Fibrosis is not limited to the muscle mass of the atria, and may occur in the sinus node (SA node) and atrioventricular node (AV node), correlating with sick sinus syndrome. Prolonged episodes of atrial fibrillation have been shown to correlate with prolongation of the sinus node recovery time,^{[citation needed]} suggesting that dysfunction of the SA node is progressive with prolonged episodes of atrial fibrillation. The sinoatrial node (abbreviated SA node, also called the sinus node) is the impulse generating (pacemaker) tissue located in the right atrium of the heart. ... The atrioventricular node (abbreviated AV node) is an area of specialized tissue between the atria and the ventricles of the heart, which conducts the normal electrical impulse from the atria to the ventricles. ... Sick sinus syndrome, also called Bradycardia-tachycardia syndrome is a group of abnormal heartbeats (arrhythmias) presumably caused by a malfunction of the sinus node, the hearts natural pacemaker. ...

Electrophysiology

Conduction
Sinus rhythm	Atrial fibrillation

The normal electrical conduction system of the heart allows the impulse that is generated by the sinoatrial node (SA node) of the heart to be propagated to and stimulate the myocardium (muscle of the heart). When the myocardium is stimulated, it contracts. It is the ordered stimulation of the myocardium that allows efficient contraction of the heart, thereby allowing blood to be pumped to the body. Image File history File links No higher resolution available. ... Image File history File links No higher resolution available. ... The normal electrical conduction in the heart allows the impulse that is generated by the sinoatrial node (SA node) of the heart to be propagated to (and stimulate) the myocardium (Cardiac muscle). ... The sinoAtrial node (abbreviated SA node or SAN, also called the sinus node) is the impulse generating (pacemaker) tissue located in the right atrium of the heart, and thus the generator of sinus rhythm. ... Myocardium is the muscular tissue of the heart. ...

In atrial fibrillation, the regular impulses produced by the sinus node to provide rhythmic contraction of the heart are overwhelmed by the rapid randomly generated electrical discharges produced by larger areas of atrial tissue, often localized to the pulmonary veins. It can be distinguished from atrial flutter, which is a more organized electrical circuit usually in the right atrium that produces characteristic saw-toothed p-waves on the electrocardiogram; in atrial flutter, the discharges circulate rapidly (at a rate of 300 beats per minute) around the atrium; in AF, there is no regularity of this kind at all. The pulmonary veins carry oxygen-rich blood from the lungs to the left atrium of the heart. ... Atrial flutter is an abnormal fast heart rhythm that occurs in the atria of the heart. ...

An organized electrical impulse in the atrium produces atrial contraction; the lack of such an impulse, as in atrial fibrillation, produces stagnant blood flow, especially in the atrial appendage and predisposes to clotting. The dislodgement of a clot from the atrium results in an embolus, and the damage produced is related to where the circulation takes it. An embolus to the brain produces the most feared complication of atrial fibrillation, namely stroke, while an embolus may also lodge in the mesenteric circulation (the circulation supplying the abdominal organs) or digit, producing organ-specific damage such a bowel ischemia or ischemia of the fingers or toes. This article is about the clotting of blood. ... This article concerns ischemia of the small bowel. ...

Treatment

The main goals of treatment of atrial fibrillation are to prevent temporary circulatory instability and to prevent stroke. Rate and rhythm control are principally used to achieve the former, while anticoagulation may be required to decrease the risk of the latter.^[11] In emergencies, when circulatory collapse is imminent due to uncontrolled tachycardia, immediate cardioversion may be indicated.^[3] For other uses, see Stroke (disambiguation). ... An anticoagulant is a substance that prevents coagulation; that is, it stops blood from clotting. ... This article or section does not cite any references or sources. ... Through electricity or drug therapy, cardioversion converts heart arrhythmias to normal rhythms. ...

The primary factors determining atrial fibrillation treatment are duration and evidence of hemodynamic instability. Cardioversion is indicated with new onset AF (for less than 48 hours) and with hemodynamic instability. If rate and rhythm control can not be maintained by medication or cardioversion, electrophysiological studies with pathway ablation may be required.^[3] Through electricity or drug therapy, cardioversion converts heart arrhythmias to normal rhythms. ... Cardiac electrophysiology is the science of the electric functioning of the heart. ... Radiofrequency ablation (RFA) uses radiofrequency energy to destroy abnormal electrical pathways in heart tissue. ...

Anticoagulation

Patients with atrial fibrillation, even lone atrial fibrillation without other evidence of heart disease, are at increased risk of stroke during long term follow up.^[12] A systematic review of risk factors for stroke in patients with nonvalvular atrial fibrillation concluded that a prior history of stroke or TIA is the most powerful risk factor for future stroke, followed by advancing age, hypertension, diabetes.^[13] The risk of stroke increases whether the lone atrial fibrillation was an isolated episode, recurrent, or chronic.^[14] The risk of systemic embolization (atrial clots migrating to other organs) depends strongly on whether there is an underlying structural problem with the heart (e.g. mitral stenosis) and on the presence of other risk factors, such as diabetes and high blood pressure. Finally, patients under 65 are much less likely to develop embolization compared with patients over 75. In young patients with few risk factors and no structural heart defect, the benefits of anticoagulation may be outweighed by the risks of hemorrhage (bleeding). Those at a low risk may benefit from mild (and low-risk) anticoagulation with aspirin (or clopidogrel in those who are allergic to aspirin). In contrast, those with a high risk of stroke derive most benefit from anticoagulant treatment with warfarin or similar drugs. Systematic reviews are named as the highest level of medical evidence, by evidence based medicine professionals. ... For other uses, see Stroke (disambiguation). ... Mitral stenosis is a narrowing of the orifice of the mitral valve of the heart. ... To meet Wikipedias quality standards, this article or section may require cleanup. ... This article is about the drug. ... A box of Plavix Clopidogrel is a potent oral antiplatelet agent often used in the treatment of coronary artery disease, peripheral vascular disease, and cerebrovascular disease. ... An anticoagulant is a substance that prevents coagulation; that is, it stops blood from clotting. ... Warfarin (also known under the brand names of Coumadin, Jantoven, Marevan, and Waran) is an anticoagulant medication that is administered orally or, very rarely, by injection. ...

In the United Kingdom, the NICE guidelines recommend using a clinical prediction rule for this purpose.^[15] The CHADS/CHADS2 score is the best validated clinical prediction rule for determining risk of stroke (and therefore who should be anticoagulated); it assigns points (totaling 0-6) depending on the presence or absence of co-morbidities such hypertension and diabetes. In a comparison of seven prediction rules, the best rules were the CHADS2 which performed similarly to the SPAF^[16] and Framingham^[17] prediction rules. ^[18] The National Institute for Health and Clinical Excellence or NICE is an agency of the National Health Service in the United Kingdom. ... A clinical prediction rule is type of medical research study in which researchers try to identify the best combination of medical sign, symptoms, and other findings in predicting the probability of a specific disease or outcome. ... For other uses, see Chad (disambiguation). ... A clinical prediction rule is type of medical research study in which researchers try to identify the best combination of medical sign, symptoms, and other findings in predicting the probability of a specific disease or outcome. ... The Framingham Heart Study is a cardiovascular study based in Framingham, Massachusetts. ... A clinical prediction rule is type of medical research study in which researchers try to identify the best combination of medical sign, symptoms, and other findings in predicting the probability of a specific disease or outcome. ...

To compensate for the increased risk of stroke, anticoagulants may be required. However, in the case of warfarin, if a patient has a yearly risk of stroke that is less than 2%, then the risks associated with taking warfarin outweigh the risk of getting a stroke. ^[19][20]

Atrial fibrillation in the context of mitral stenosis is associated with a seventeen-fold increase in stroke risk.^[2]

Acute anticoagulation

If anticoagulation is required urgently (e.g. for cardioversion), heparin or similar drugs achieve the required level of protection much quicker than warfarin, which may take several days to reach adequate levels. Heparin, a highly sulfated glycosaminoglycan is widely used as an injectable anticoagulant and has the highest negative charge density of any known biological molecule. ...

In the initial stages after an embolic stroke, anticoagulation may be risky, as the damaged area of the brain is relatively prone to bleeding (hemorrhagic transformation).^[21] As a result, a clinical practice guideline by National Institute for Health and Clinical Excellence recommends that anticoagulation should begin two weeks after stroke if no hemorrhage occurred.^[15] Clinical practice guidelines are collections of practical information for use by doctors and other medical professionals. ... The National Institute for Health and Clinical Excellence or NICE is an agency of the National Health Service in the United Kingdom. ...

Chronic anticoagulation

Among patients with "non-valvular" atrial fibrillation, anticoagulation can reduce stroke by 60% while antiplatelet agents can reduce stroke by 20%. ^[22][23]. There is evidence that aspirin and clopidogrel are effective when used together, but the combination is still inferior to warfarin.^[24] This article is about the drug. ... A box of Plavix Clopidogrel is a potent oral antiplatelet agent often used in the treatment of coronary artery disease, peripheral vascular disease, and cerebrovascular disease. ... Warfarin (also known under the brand names of Coumadin, Jantoven, Marevan, and Waran) is an anticoagulant medication that is administered orally or, very rarely, by injection. ...

Warfarin treatment requires frequent monitoring with a blood test called the international normalized ratio (INR); this determines whether the correct dose is being used. In atrial fibrillation, the usual target INR is between 2.0 and 3.0 (higher targets are used in patients with mechanical artificial heart valves, many of whom may also have atrial fibrillation). A high INR may indicate increased bleeding risk, while a low INR would indicate that there is insufficient protection from stroke. The prothrombin time (PT) and its derived measures of prothrombin ratio (PR) and international normalized ratio (INR) are measures of the extrinsic pathway of coagulation. ... It has been suggested that this article or section be merged with Heart valve prosthesis. ...

Elderly patients

The very elderly (patients aged 75 years or more) may benefit from anticoagulation provided that their anticoaguation does not increase hemorrhagic complications, which is a difficult goal. Patients aged 80 years or more may be especially susceptible to bleeding complications, with a rate of 13 bleeds per 100 person-years.^[25] A rate of 13 bleeds per 100 person years would seem to preclude use of warfarin; however, a randomized controlled trial found benefit in treating patients 75 years or over with a number needed to treat of 50.^[26] Of note, this study had very low rate of hemorrhagic complications in the warfarin group. A randomized controlled trial (RCT) is a form of clinical trial, or scientific procedure used in the testing of the efficacy of medicines or medical procedures. ... The number needed to treat (NNT) is an epidemiological measure that indicates how many patients would require treatment with a form of medication to reduce the expected number of cases of a defined endpoint by one. ...

Rate control versus rhythm control

AF can cause disabling and annoying symptoms. Palpitations, angina, lassitude (weariness), and decreased exercise tolerance are related to rapid heart rate and inefficient cardiac output caused by AF. Furthermore, AF with a persistent rapid rate can cause a form of heart failure called tachycardia induced cardiomyopathy. This can significantly increase mortality and morbidity, which can be prevented by early and adequate treatment of the AF. A palpitation is an abnormal, rapid beating of the heart, brought on by overexertion, disease or drugs. ... angina tonsillaris see tonsillitis. ... Tachycardia induced cardiomyopathy, also known as chronotropic cardiomyopathy and tachycardiomyopathy, is a weakening of the myocardium (the muscle of the heart) that is due to prolonged periods of a fast heart rate. ...

There are two ways to approach these symptoms: rate control and rhythm control. Rate control treatments seek to reduce the heart rate to normal, usually 60 to 100 beats per minute. Rhythm control seeks to restore the normal heart rhythm, called normal sinus rhythm. Studies suggest that rhythm control is mainly a concern in newly diagnosed AF, while rate control is more important in the chronic phase. Rate control with anticoagulation is as effective a treatment as rhythm control in long term mortality studies, the AFFIRM Trial.^[27]

The AFFIRM study showed no difference in risk of stroke in patients who have converted to a normal rhythm with anti-arrhythmic treatment, compared to those who have only rate control.^[27]

Rate control

Rate control is achieved with medications that work by increasing the degree of block at the level of the AV node, effectively decreasing the number of impulses that conduct down into the ventricles. This can be done with:^[3]

• Beta blockers (preferably the "cardioselective" beta blockers such as metoprolol, atenolol, bisoprolol)
• Cardiac glycosides (i.e. digoxin)
• Calcium channel blockers (i.e. diltiazem or verapamil)

In addition to these agents, amiodarone has some AV node blocking effects (particularly when administered intravenously), and can be used in individuals when other agents are contraindicated or ineffective (particularly due to hypotension). Beta blockers or beta-adrenergic blocking agents are a class of drugs used to treat a variety of cardiovascular conditions and some other diseases. ... “Minax” redirects here. ... Atenolol is a drug belonging to the group of beta blockers, a class of drugs used primarily in cardiovascular diseases. ... Bisoprolol is a drug belonging to the group of beta blockers, a class of drugs used primarily in cardiovascular diseases. ... Cardiac glycosides are drugs used in the treatment of congestive heart failure and cardiac arrhythmia. ... Digoxin (INN) (IPA: ) is a purified cardiac glycoside extracted from the foxglove plant, Digitalis lanata. ... Calcium channel blockers are a class of drugs and natural substances with effects on many excitable cells of the body, like the muscle of the heart, smooth muscles of the vessels or neuron cells. ... Diltiazem is a member of the group of drugs known as Benzothiapines , which are a class of calcium channel blockers, used in the treatment of hypertension, angina pectoris, and some types of arrhythmia. ... Verapamil (brand names: Isoptin®, Verelan®, Calan®) is a medical drug that acts as an L-type calcium channel blocker. ... Amiodarone belongs to a class of drugs called Vaughan-Williams Class III antiarrhythmic agent. ...

Cardioversion

Main article: Cardioversion

Rhythm control methods include electrical and chemical cardioversion:^[3] Through electricity or drug therapy, cardioversion converts heart arrhythmias to normal rhythms. ... Through electricity or drug therapy, cardioversion converts heart arrhythmias to normal rhythms. ...

• Electrical cardioversion involves the restoration of normal heart rhythm through the application of a DC electrical shock.
• Chemical cardioversion is performed with drugs, such as amiodarone, dronedarone^[28], procainamide, ibutilide, propafenone or flecainide.

The main risk of cardioversion is systemic embolization of a thrombus (blood clot) from the previously fibrillating left atrium. Cardioversion should not be performed without adequate anticoagulation in patients with more than 48 hours of atrial fibrillation. Cardioversion may be performed in instances of AF lasting more than 48 hours if a transesophogeal echocardiogram (TEE) demonstrates no evidence of clot within the heart.^[3] Amiodarone belongs to a class of drugs called Vaughan-Williams Class III antiarrhythmic agent. ... Dronedarone (also known as SR33589) is a drug under development by Sanofi-Aventis, mainly for the indication of cardiac arrhythmias (irregular heartbeat). ... Procainamide (trade name Pronestyl®) is a pharmaceutical antiarrhythmic agent used for the medical treatment of cardiac arrhythmias, classified by the Vaughan Williams classification system as class Ia. ... Ibutilide (ibutilide fumarate) is a class III antiarrhythmic agent. ... Propafenone (pro-PA-fen-own) (brand name Rythmol SR®) is a class Ic anti-arrhythmic medication, which treats illnesses associated with rapid heart beats such as atrial and ventricular arrhythmias. ... Flecainide acetate is a class Ic antiarrhythmic agent used to prevent and treat tachyarrhythmias (abnormal fast rhythms of the heart). ... For Trombe wall (used in solar homes), see Trombe wall. ... An echocardiogram. ...

Whichever method of cardioversion is used, approximately 50% of patient relapse within one year, although the continued daily use of oral antiarrhythmic drugs may extend this period. The key risk factor for relapse is duration of AF, although other risk factors that have been identified include the presence of structural heart disease, and increasing age.^{[citation needed]} A relapse (etymologically, who falls again) occurs when a person is affected again by a condition that affected them in the past. ...

Maintenance of sinus rhythm

The mainstay of maintaining sinus rhythm is the use of antiarrhythmic agents. Recently, other approaches have been developed that promise to decrease or eliminate the need for antiarrhythmic agents.

Antiarrhythmic agents

Main article: Antiarrhythmic agent

The anti-arrhythmic medications often used in either pharmacological cardioversion or in the prevention of relapse to AF alter the flux of ions in heart tissue, making them less excitable, setting the stage for spontaneous and durable cardioversion. These medications are often used in concert with electrical cardioversion. Antiarrhythmic agents are a group of pharmaceuticals that are used to suppress fast rhythms of the heart (cardiac arrhythmias), such as atrial fibrillation, atrial flutter, ventricular tachycardia, and ventricular fibrillation. ... Antiarrhythmic agents are a group of pharmaceuticals that are used to suppress fast rhythms of the heart (cardiac arrhythmias), such as atrial fibrillation, atrial flutter, ventricular tachycardia, and ventricular fibrillation. ...

Radiofrequency ablation

In patients with AF where rate control drugs are ineffective and it is not possible to restore sinus rhythm using cardioversion, non-pharmacological alternatives are available. For example, to control rate it is possible to destroy the bundle of cells connecting the upper and lower chambers of the heart - the atrioventricular node - which regulates heart rate, and to implant a pacemaker instead. A more complex technique, which avoids the need for a pacemaker, involves ablating groups of cells near the pulmonary veins where atrial fibrillation is thought to originate, or creating more extensive lesions in an attempt to prevent atrial fibrillation from establishing itself.^[3] The atrioventricular node (abbreviated AV node) is an area of specialized tissue between the atria and the ventricles of the heart, which conducts the normal electrical impulse from the atria to the ventricles. ... A pacemaker, scale in centimeters A pacemaker (or artificial pacemaker, so as not to be confused with the hearts natural pacemaker) is a medical device which uses electrical impulses, delivered by electrodes contacting the heart muscles, to regulate the beating of the heart. ...

Ablation is a newer technique and has shown some promise for cases of recurrent AF that are unresponsive to conventional treatments. Radiofrequency ablation (RFA) uses radiofrequency energy to destroy abnormal electrical pathways in heart tissue. The energy emitting probe (electrode) is placed into the heart through a catheter inserted into veins in the groin or neck. Electrodes that can detect electrical activity from inside the heart are also inserted, and the electrophysiologist uses these to "map" an area of the heart in order to locate the abnormal electrical activity before eliminating the responsible tissue. Radiofrequency ablation (RFA) uses radiofrequency energy to destroy abnormal electrical pathways in heart tissue. ... For other uses, see Electrode (disambiguation). ... Catheter disassembled In medicine, a catheter is a tube that can be inserted into a body cavity, duct or vessel. ...

Most AF ablations consist of isolating the electrical pathways from the pulmonary veins (PV)^[29], which are located on the posterior wall of the left atrium. All veins from the body (including neck and groin) lead to the right atrium, so in order to get to the left atrium the catheters must get across the atrial septum. This is done by piercing a small hole in the septal wall. This is called a transeptal approach. Once in the left atrium, the physician may perform Wide Area Circumferential Ablation (WACA) to electrically isolate the PVs from the left atrium.^[30] The pulmonary veins carry oxygen-rich blood from the lungs to the left atrium of the heart. ...

Some more recent approaches to ablating AF is to target sites that are particularly disorganized in both atria as well as in the coronary sinus (CS). These sites are termed complex fractionated atrial electrogram (CFAE) sites.^[31]. It is believed by some that the CFAE sites are the cause of AF, or a combination of the PVs and CFAE sites are to blame. New techniques include the use of cryoablation (tissue freezing using a coolant which flows through the catheter), and microwave ablation, where tissue is ablated by the microwave energy "cooking" the adjacent tissue. The coronary sinus is a collection of veins joined together to form a large vessel that collects blood from the myocardium of the heart. ... Atrial fibrillation (AF or afib) is an abnormal heart rhythm (cardiac arrhythmia) which involves the two small, upper heart chambers (the atria). ...

This is an area of active research, especially with respect to the RF ablation technique and emphasis on isolating the pulmonary veins that enter into the left atrium. The main problem in 2006 is that the procedure is only 70-80% effective at best -- and causes stroke in about 1% of patients.

Surgical Maze procedure

Main article: Maze procedure

James Cox, MD, and associates developed the Cox maze procedure, an open-heart surgical procedure intended to eliminate atrial fibrillation, and performed the first one in 1987. "Maze" refers to the series of incisions made in the atria, which are arranged in a maze-like pattern. The intention was to eliminate AF by using incisional scars to block abnormal electrical circuits (atrial macroreentry) that AF requires. This procedure required an extensive series of endocardial (from the inside of the heart) incisions through both atria, a median sternotomy (vertical incision through the breastbone) and cardiopulmonary bypass (heart-lung machine). A series of improvements were made, culminating in 1992 in the Cox maze III procedure, which is now considered to be the "gold standard" for effective surgical cure of AF. The Cox maze III is sometimes referred to as the "traditional maze", the "cut and sew maze", or simply the "maze".^[32] The maze procedure is a collection of cardiac surgery procedures intended to cure atrial fibrillation (AF), a common disturbance of heart rhythm. ...

Minimaze surgery is minimally invasive cardiac surgery similarly intended to cure atrial fibrillation. The "Minimaze" procedure refers to "mini" versions of the original maze procedure. These procedures are less invasive than the Cox maze procedure and do not require a median sternotomy (vertical incision in the breastbone) or cardiopulmonary bypass (heart-lung machine). These procedures use microwave, radiofrequency, or acoustic energy to ablate atrial tissue near the pulmonary veins. A Heart-Lung Machine (upper right) in a Coronary Artery Bypass surgery (CABG) Cardiopulmonary bypass (CPB) is a technique that temporarily takes over the function of the heart and lungs during surgery. ...

Epidemiology

Atrial fibrillation is the most common arrhythmia found in clinical practice.^{[citation needed]} It also accounts for 1/3 of hospital admissions for cardiac rhythm disturbances^{[citation needed]}, and the rate of admissions for atrial fibrillation has risen in recent years.^[33] Approximately 2.2 million individuals in the United States and 4.5 million individuals in the European Union have atrial fibrillation.^[3][34]

The incidence of atrial fibrillation increases with age. The prevalence in individuals over the age of 80 is about 8%.^[35] In developed countries, the number of patients with atrial fibrillation is likely to increase during the next 50 years, due to the growing proportion of elderly individuals.^[36]

History

Because the diagnosis of atrial fibrillation requires measurement of the electrical activity of the heart, atrial fibrillation was not truly described until 1874, when Edmé Félix Alfred Vulpian observed the irregular atrial electrical behavior that he termed "fremissement fibrillaire" in dog hearts.^[37] In the mid-eighteenth century, Jean-Baptiste de Sénac made note of dilated, irritated atria in people with mitral stenosis.^[38] The irregular pulse associated with AF was first recorded in 1876 by Carl Wilhelm Hermann Nothnagel and termed "delirium cordis", stating that "[I]n this form of arrhythmia the heartbeats follow each other in complete irregularity. At the same time, the height and tension of the individual pulse waves are continuously changing".^[39] Correlation of delirium cordis with the loss of atrial contraction as reflected in the loss of a waves in the jugular venous pulse was made by Sir James MacKenzie in 1904.^[40] Willem Einthoven published the first electrocardiogram showing AF in 1906.^[41] The connection between the anatomic and electrical manifestations of AF and the irregular pulse of delirium cordis was made in 1909 by Carl Julius Rothberger, Heinrich Winterberg, and Sir Thomas Lewis.^[42][43][44] Edmé Félix Alfred Vulpian (born January 5, 1826, Paris, France; died May 18, 1887) was a French physician and neurologist. ... Jean-Baptiste de Sénac (1693-1770) was a French physician who was born in the town of Lombez. ... Mitral stenosis is a narrowing of the orifice of the mitral valve of the heart. ... Carl Wilhelm Hermann Nothnagel (September 28, 1841 - July 7, 1905) was a German internist who in 1876 described the irregular pulse associated with atrial fibrillation. ... The jugular venous pressure (JVP, sometimes referred to as jugular venous pulse) is the indirectly observed pressure over the venous system. ... Willem Einthoven Willem Einthoven (May 21, 1860 – September 29, 1927) was a Dutch doctor and physiologist. ... “QRS” redirects here. ...

See also

• Atrial flutter
• Ashman phenomenon

Atrial flutter is an abnormal fast heart rhythm that occurs in the atria of the heart. ... The Ashman phenomenon, also known as Ashman beats, describes a particular type of wide complex tachycardia (fast rhythm of the heart) that is often seen in atrial fibrillation. ...

References

A digital object identifier (or DOI) is a standard for persistently identifying a piece of intellectual property on a digital network and associating it with related data, the metadata, in a structured extensible way. ... A digital object identifier (or DOI) is a standard for persistently identifying a piece of intellectual property on a digital network and associating it with related data, the metadata, in a structured extensible way. ... A digital object identifier (or DOI) is a standard for persistently identifying a piece of intellectual property on a digital network and associating it with related data, the metadata, in a structured extensible way. ... A digital object identifier (or DOI) is a standard for persistently identifying a piece of intellectual property on a digital network and associating it with related data, the metadata, in a structured extensible way. ... A digital object identifier (or DOI) is a standard for persistently identifying a piece of intellectual property on a digital network and associating it with related data, the metadata, in a structured extensible way. ... A digital object identifier (or DOI) is a standard for persistently identifying a piece of intellectual property on a digital network and associating it with related data, the metadata, in a structured extensible way. ... A digital object identifier (or DOI) is a standard for persistently identifying a piece of intellectual property on a digital network and associating it with related data, the metadata, in a structured extensible way. ... Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era in the 21st century. ... is the 227th day of the year (228th in leap years) in the Gregorian calendar. ... A digital object identifier (or DOI) is a standard for persistently identifying a piece of intellectual property on a digital network and associating it with related data, the metadata, in a structured extensible way. ... A digital object identifier (or DOI) is a standard for persistently identifying a piece of intellectual property on a digital network and associating it with related data, the metadata, in a structured extensible way. ... A digital object identifier (or DOI) is a standard for persistently identifying a piece of intellectual property on a digital network and associating it with related data, the metadata, in a structured extensible way. ... A digital object identifier (or DOI) is a standard for persistently identifying a piece of intellectual property on a digital network and associating it with related data, the metadata, in a structured extensible way. ... A digital object identifier (or DOI) is a standard for persistently identifying a piece of intellectual property on a digital network and associating it with related data, the metadata, in a structured extensible way. ... A digital object identifier (or DOI) is a standard for persistently identifying a piece of intellectual property on a digital network and associating it with related data, the metadata, in a structured extensible way. ... A digital object identifier (or DOI) is a standard for persistently identifying a piece of intellectual property on a digital network and associating it with related data, the metadata, in a structured extensible way. ... A digital object identifier (or DOI) is a standard for persistently identifying a piece of intellectual property on a digital network and associating it with related data, the metadata, in a structured extensible way. ...

External links

• American Heart Association page on atrial fibrillation
• Atrial fibrillation at patient.co.uk
• Bandolier (evidence-based medicine) resource on atrial fibrillation

[pt:Fibrilação auricular]] For transport in plants, see Vascular tissue. ... A renal cell carcinoma (chromophobe type) viewed on a hematoxylin & eosin stained slide Pathologist redirects here. ... For other forms of hypertension, see Hypertension (disambiguation). ... In kidney, as a result of benign arterial hypertension, hyaline (pink, amorphous, homogeneous material) accumulates in the wall of small arteries and arterioles, producing the thickening of their walls and the narrowing of the lumens - hyaline arteriolosclerosis. ... While most forms of hypertension have no known underlying cause (and are thus known as essential hypertension or primary hypertension), in about 10% of the cases, there is a known cause, and thus the hypertension is secondary hypertension (or, less commonly, inessential hypertension). ... Renovascular hypertension (or renal hypertension) is a form of secondary hypertension. ... Ischaemic (or ischemic) heart disease is a disease characterized by reduced blood supply to the heart. ... Prinzmetals angina, also known as variant angina or angina inversa, is a syndrome typically consisting of angina (cardiac chest pain) at rest that occurs in cycles. ... Heart attack redirects here. ... Dresslers syndrome is a form of pericarditis that occurs in the setting of injury to the heart or the pericardium (the outer lining of the heart). ... Pulmonary circulation is the portion of the cardiovascular system which carries oxygen-depleted blood away from the heart, to the lungs, and returns oxygenated blood back to the heart. ... Cor pulmonale, also known as right heart failure, is a medical term used to describe a change in structure and function of the right ventricle of the heart as a result of a respiratory disorder. ... The pericardium is a double-walled sac that contains the heart and the roots of the great vessels. ... Pericarditis is inflammation of the sac surrounding the heart, the pericardium. ... Pericardial effusion is an abnormal accumulation of fluid in the pericardial cavity. ... Cardiac tamponade, also known as pericardial tamponade, is a medical emergency condition where liquid accumulates in the pericardium in a relatively short time. ... In the heart, the endocardium is the innermost layer of tissue that lines the chambers of the heart. ... Grays Fig. ... Endocarditis is an inflammation of the inner layer of the heart, the endocardium. ... The mitral valve (also known as the bicuspid valve or left atrioventricular valve), is a dual flap (bi = 2) valve in the heart that lies between the left atrium (LA) and the left ventricle (LV). ... Mitral regurgitation (MR), also known as mitral insufficiency, is the abnormal leaking of blood through the mitral valve, from the left ventricle into the left atrium of the heart. ... Mitral valve prolapse (MVP) is a heart valve condition marked by the displacement of an abnormally thickened mitral valve leaflet into the left atrium during systole. ... Mitral stenosis is a narrowing of the orifice of the mitral valve of the heart. ... The aortic valve is one of the valves of the heart. ... Aortic valve stenosis (AS) is a heart condition caused by the incomplete opening of the aortic valve. ... Aortic insufficiency (AI), also known as aortic regurgitation (AR), is the leaking of the aortic valve of the heart that causes blood to flow in the reverse direction during ventricular diastole, from the aorta into the left ventricle. ... The pulmonary valve, also known as pulmonic valve, is the semilunar valve of the heart that lies between the right ventricle and the pulmonary artery and has three cusps. ... Pulmonary valve stenosis is a medical condition in which outflow of blood from the right ventricle of the heart is obstructed at the level of the pulmonic valve. ... Pulmonary valve insufficiency (or incompetence, or regurgitation) is a condition where the pulmonary valve is not strong enough to prevent backflow into the right ventricle. ... The tricuspid valve is on the right side of the heart, between the right atrium and the right ventricle. ... Tricuspid valve stenosis is a valvular heart disease which results in the narrowing of the orifice of the tricuspid valve of the heart. ... Tricuspid insufficiency, also termed Tricuspid regurgitation, refers to the failure of the hearts tricuspid valve to close properly during systole. ... Myocardium is the muscular tissue of the heart. ... In medicine (cardiology), myocarditis is inflammation of the myocardium, the muscular part of the heart. ... Dilated cardiomyopathy or DCM (also known as congestive cardiomyopathy), is a disease of the myocardium (the muscle of the heart) in which a portion of the myocardium is dilated, often without any obvious cause. ... Hypertrophic cardiomyopathy, or HCM, is a disease of the myocardium (the muscle of the heart) in which a portion of the myocardium is hypertrophied (thickened) without any obvious cause. ... This article is considered orphaned, since there are very few or no other articles that link to this one. ... Restrictive cardiomyopathy (RCM) is the least common cardiomyopathy. ... Arrhythmogenic right ventricular dysplasia (ARVD, also known as arrhythmogenic right ventricular cardiomyopathy or ARVC) is a type of nonischemic cardiomyopathy that involves primarily the right ventricle. ... The normal electrical conduction in the heart allows the impulse that is generated by the sinoatrial node (SA node) of the heart to be propagated to (and stimulate) the myocardium (Cardiac muscle). ... A heart block is a disease in the electrical system of the heart. ... A heart block denotes a disease in the electrical system of the heart. ... First degree AV block or PR prolongation is a disease of the electrical conduction system of the heart in which the PR interval is lengthened. ... Second degree AV block is a disease of the electrical conduction system of the heart. ... Third degree AV block, also known as complete heart block, is a defect of the electrical system of the heart, in which the impulse generated in the atria (typically the SA node on top of the right atrium) does not propagate to the ventricles. ... Bundle branch block refers to a disorder of the hearts electrical conducting system. ... ECG characteristics of a typical LBBB showing wide QRS complexes with abnormal morphology in leads V1 and V6. ... Right bundle branch block (RBBB) is a cardiac conduction abnormality seen on electrocardiogram (EKG). ... Bifascicular block is a conduction abnormality in the heart where two of the three main fascicles of the His/Purkinje system are blocked. ... Trifascicular heart block is the triad of first degree heart block, right bundle branch block, and either left anterior or left posterior hemi block seen on an electrocardiogram (EKG). ... Pre-excitation syndrome is a condition where the the ventricles of the heart become depolarized too early, which leads to their premature contraction, causing arrhythmia. ... Wolff-Parkinson-White syndrome (WPW) is a syndrome of pre-excitation of the ventricles of the heart due to an accessory pathway known as the Bundle of Kent. ... Lown-Ganong-Levine syndrome (LGL) is a syndrome of pre-excitation of the ventricles due to an accessory pathway providing an abnormal electrical communication from the atria to the ventricles. ... The long QT syndrome (LQTS) is a heart disease in which there is an abnormally long delay between the electrical excitation (or depolarization) and relaxation (repolarization) of the ventricles of the heart. ... The term Stokes-Adams Attack refers to a sudden, transient episode of syncope, occasionally featuring seizures. ... Cardiac arrhythmia is any of a group of conditions in which the electrical activity of the heart is irregular or is faster or slower than normal. ... A supraventricular tachycardia (SVT) is a rapid rhythm of the heart in which the origin of the electrical signal is either the atria or the AV node. ... AV nodal reentrant tachycardia (AVNRT) is a type of reentrant tachycardia (fast rhythm) of the heart. ... Ventricular tachycardia (V-tach or VT) is a fast rhythm that originates in one of the ventricles of the heart. ... Atrial flutter is an abnormal fast heart rhythm that occurs in the atria of the heart. ... Ventricular fibrillation (V-fib or VF) is a cardiac condition which consists of a lack of coordination of the contraction of the muscle tissue of the large chambers of the heart that eventually leads to the heart stopping altogether. ... pac This page meets Wikipedias criteria for speedy deletion. ... This article does not cite any references or sources. ... An ectopic pacemaker or ectopic focus is an excitable group of cells that causes a premature heart beat outside the normally functioning SA node of the human heart. ... Sick sinus syndrome, also called Bradycardia-tachycardia syndrome is a group of abnormal heartbeats (arrhythmias) presumably caused by a malfunction of the sinus node, the hearts natural pacemaker. ... Cardiovascular disease refers to the class of diseases that involve the heart or blood vessels (arteries and veins). ... Cardiomegaly is a medical condition wherein the heart is enlarged. ... Although ventricular hypertrophy may occur in either the left or right or both ventricles of the heart , left ventricular hypertrophy (LVH) is more commonly encountered. ... Left ventricular hypertrophy (LVH) is the thickening of the myocardium (muscle) of the left ventricle of the heart. ... Right ventricular hypertrophy (RVH) is a form of ventricular hypertrophy affecting the right ventricle. ... Cerebrovascular disease is damage to the blood vessels in the brain, resulting in a stroke. ... This article needs cleanup. ... A cerebral hemorrhage is a bleed into the substance of the cerebrum. ... Extra-axial hematoma, or extra-axial hemorrhage is a subtype of intracranial hemorrhage, or bleeding within the intracranial space, that occurs within the skull but outside of the brain tissue itself. ... Nontraumatic epidural hematoma in a young woman. ... A subdural hematoma (SDH) is a form of traumatic brain injury in which blood collects between the dura (the outer protective covering of the brain) and the arachnoid (the middle layer of the meninges). ... Subarachnoid hemorrhage (SAH) is bleeding into the subarachnoid space surrounding the brain, i. ... Intra-axial hemorrhages, or intra-axial hematomas, are a subtype of intracranial hemorrhage that occur within the brain tissue itself. ... Intraventricular hemorrhage (or IVH) is a bleeding of the ventricles, where the cerebrospinal fluid is produced and circulates through towards the subarachnoid space. ... Intra-axial hemorrhages, or intra-axial hematomas, are a subtype of intracranial hemorrhage that occur within the brain tissue itself. ... Ischemia or infarction of the spinal cord in the distribution of the anterior spinal artery, which supplies the ventral two-thirds of the spinal cord and Medulla. ... Binswangers disease is a rare form of multi-infarct dementia caused by damage to deep white brain matter. ... Moyamoya disease is an extremely rare disorder in most parts of the world except in Japan. ... Section of an artery An artery or arterial is also a class of highway. ... An arteriole is a blood vessel that extends and branchs out from an artery and leads to capillaries. ... The word capillary is used to describe any very narrow tube or channel through which a fluid can pass. ... Renal artery stenosis is the narrowing of the renal artery. ... Aortic dissection is a tear in the wall of the aorta (the largest artery of the body). ... An aortic aneurysm is a general term for any swelling (dilatation or aneurysm) of the aorta, usually representing an underlying weakness in the wall of the aorta at that location. ... A plate from Grays Anatomy with yellow lines depicting the most common infrarenal location of the AAA. Abdominal aortic aneurysm, also written as AAA and often pronounced triple-A, is a localized dilatation of the abdominal aorta, that exceeds the normal diameter by more than 50%. The normal diameter... Post surgical photo of brain aneurysm survivor. ... Raynauds phenomenon (RAY-noz), in medicine, is a vasospastic disorder causing discoloration of the fingers, toes, and occasionally other extremities, named for French physician Maurice Raynaud (1834 - 1881). ... Raynauds disease (RAY-noz) is a condition that affects blood flow to the extremities which include the fingers, toes, nose and ears when exposed to temperature changes or stress. ... Buergers disease (also known as thromboangiitis obliterans) is an acute inflammation and thrombosis (clotting) of arteries and veins of the hands and feet. ... Arteritis is inflammation of the walls of arteries, usually as a result of infection or auto-immune response. ... Aortitis is the inflammation of the aorta. ... Intermittent claudication is a cramping sensation in the legs that is present during exercise or walking and occurs as a result of decreased oxygen supply. ... An arteriovenous fistula is an abnormal connection or passageway between an artery and a vein. ... In medicine, hereditary hemorrhagic telangiectasia (HHT), also known as Rendu-Osler-Weber syndrome, is a genetic disorder that leads to vascular malformations. ... A spider angioma (also known as a nevus araneus, spider nevus, or vascular spider) is a type of angioma found slightly below the skins surface, often containing a central red spot and reddish extensions which radiate outwards like a spiders web. ... In the circulatory system, a vein is a blood vessel that carries blood toward the heart. ... Lymph originates as blood plasma lost from the circulatory system, which leaks out into the surrounding tissues. ... Lymph nodes are components of the lymphatic system. ... Thrombosis is the formation of a clot or thrombus inside a blood vessel, obstructing the flow of blood through the circulatory system. ... Phlebitis is an inflammation of a vein, usually in the legs. ... It has been suggested that this article or section be merged into deep vein thrombosis. ... This article is about Deep-vein thrombosis. ... May-Thurner syndrome is deep vein thrombosis of the iliofemoral vein due to compression of the left common iliac vein by overlying right common iliac artery. ... A venous thrombosis is a blood clot that forms within a vein. ... In medicine (gastroenterology and hepatology), Budd-Chiari syndrome is the clinical picture caused by occlusion of the hepatic vein. ... Renal vein thrombosis (RVT) is the formation of a clot or thrombus obstructing the renal vein, leading to a reduction in drainage of the kidney. ... Paget-Schroetter disease (also Paget-von Schrötter disease) refers to deep vein thrombosis of an upper extremity vein, including the axillary vein or subclavian vein. ... Vein gymnastics in the barefoot park Dornstetten, Germany. ... A portacaval anastomosis is a specific type of anastomosis that occurs between the veins of portal circulation and those of systemic circulation. ... Hemorrhoids (AmE), haemorrhoids (BrE), emerods, or piles are varicosities or swelling and inflammation of veins in the rectum and anus. ... In medicine (gastroenterology), esophageal varices are extreme dilations of sub mucosal veins in the mucosa of the esophagus in diseases featuring portal hypertension, secondary to cirrhosis primarily. ... Cross section showing the pampiniform plexus Varicocele is an abnormal enlargement of the veins in the scrotum draining the testicles. ... Gastric varices are dilated submucosal veins in the stomach. ... Caput medusae means dilated veins around the umbilicus. ... Superior vena cava syndrome (SVCS) is a result of obstruction of the superior vena cava. ... Lymphadenopathy is a term meaning disease of the lymph nodes. ... Azskeptic 17:34, 10 July 2007 (UTC) Lymphedema, also spelled lymphoedema, also known as lymphatic obstruction, is a condition of localized fluid retention caused by a compromised lymphatic system. ... Lymphadenopathy is swelling of one or more lymph nodes. ...