Citizendia

Atrial fibrillation
Classification and external resources
The P waves, which represent depolarization of the atria, are irregular or absent during atrial fibrillation.
ICD-10I48.
ICD-9427.31
DiseasesDB1065
MedlinePlus000184
eMedicinemed/184  emerg/46
MeSHD001281

Atrial fibrillation (AF or afib) is a cardiac arrhythmia (abnormal heart rhythm) that involves the two upper chambers (atria) of the heart. The International Statistical Classification of Diseases and Related Health Problems (most commonly known by the abbreviation ICD) provides codes to classify Diseases The International Statistical Classification of Diseases and Related Health Problems 10th Revision ( ICD -10) is a coding of diseases and signs symptoms abnormal findings I00-I99 - Diseases of the Circulatory system (I00-I02 Acute rheumatic fever ( Rheumatic fever without mention of Heart The International Statistical Classification of Diseases and Related Health Problems (most commonly known by the abbreviation ICD) provides codes to classify Diseases The following is a list of codes for International Statistical Classification of Diseases and Related Health Problems. The Diseases Database is a free Website that provides information about the relationships between medical conditions Symptoms, and Medications. MedlinePlus, with the MedlinePlus Medical Encyclopedia, is a website network containing Health information from the world's largest medical Library eMedicine is an online clinical medical knowledge base that was founded in 1996 by Scott Plantz and Richard Lavely two medical doctors Medical Subject Headings ( MeSH) is a huge Controlled vocabulary (or metadata system for the purpose of indexing journal articles and books Dysrhythmia redirects here For the American band see Dysrhythmia (band. In Anatomy, the atrium (plural atria) refers to a chamber or space The heart is a muscular organ in all Vertebrates responsible for pumping Blood through the Blood vessels by repeated rhythmic It can often be identified by taking a pulse and observing that the heart beats don't occur at regular intervals, but a conclusive indication of AF is the absence of P waves on an electrocardiogram (ECG). In Medicine, a person's pulse is the throbbing of their arteries. AF is the most common arrhythmia; risk increases with age, with 8% of people over 80 having AF. In AF, the normal electrical impulses that are generated by the sinoatrial node are overwhelmed by disorganized electrical impulses that originate in the atria and pulmonary veins, leading to conduction of irregular impulses to the ventricles that generate the heartbeat. The Sinoatrial node (abbreviated SA node or SAN, also called the sinus node) is the impulse generating (pacemaker tissue located in the Right atrium 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 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 AF is to become a chronic condition. Chronic AF leads to a small increase in the risk of death. [1][2]

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. A palpitation (medical term ectopic heart beat) is an abnormal awareness of the beating of the Heart, whether it is too slow too fast irregular Angina pectoris, commonly known as angina, is severe Chest pain due to Ischemia (a lack of blood and hence Oxygen supply of the heart Heart failure is a Cardiac condition that occurs when a problem with the structure or function of the Heart impairs its ability to supply Patients with AF usually have a significantly increased risk of stroke (up to 7 times that of the general population). A stroke is the rapidly developing loss of brain functions due to a disturbance in the blood vessels supplying blood to the brain Stroke risk increases during AF because blood may pool and form clots in the poorly contracting atria and especially in the left atrial appendage (LAA). The left atrial appendage (LAA (left auricular appendix left auricula left auricle is a conical muscular pouch connected to the Left atrium of the Heart. The level of increased risk of stroke depends on the number of additional risk factors. If the AF patient has none, the risk of stroke is similar to that of the general population. [3] However, many patients do have additional risk factors and AF is a leading cause of stroke. [4]

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. Synchronized electrical cardioversion is the process by which an abnormally fast Heart rate or Cardiac arrhythmia is terminated by the delivery of a therapeutic dose Surgical and catheter-based therapies may also be used to prevent recurrence of AF in certain individuals. People with AF are often given anticoagulants such as warfarin to protect them from stroke. An anticoagulant is a substance that prevents coagulation; that is it stops Blood from clotting Warfarin (also known under the brand names Coumadin, Jantoven, Marevan, and Waran) is an Anticoagulant.

Contents

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. The American Heart Association (AHA is a Non-profit organization in the United States that fosters appropriate The American College of Cardiology (ACC is a Nonprofit medical association established in 1949 to educate research and influence health care public policy [5]

AF CategoryDefining Characteristics
  First detected  only one diagnosed episode
  Paroxysmal  recurrent episodes that self-terminate in less than 7 days  
  Persistent  recurrent episodes that last more than 7 days
  Permanent  an ongoing long-term episode

All atrial fibrillation patients are initially in the category called first detected AF. These patients may or may not have had previous undetected episodes. If a first detected episode self-terminates in less than 7 days and then another episode begins later on, the case has moved into the category of paroxysmal AF. Although patients in this category have episodes lasting up to 7 days, in most cases of paroxysmal AF the episodes will self-terminate in less than 24 hours. [5] If instead the episode lasts for more than 7 days, it is unlikely to self-terminate[6] and it is called persistent AF. In this case, the episode may be terminated by cardioversion. Synchronized electrical cardioversion is the process by which an abnormally fast Heart rate or Cardiac arrhythmia is terminated by the delivery of a therapeutic dose If cardioversion is unsuccessful or it is not attempted, and the episode is ongoing for a long time (e. g. a year or more), the patient's AF is called permanent.

Using this system, it's not always clear what an AF case should be called. For example, a case may fit into the paroxysmal AF category some of the time, while other times it may have the characteristics of persistent AF. One may be able to decide which category is more appropriate by determining which one occurs most often in the case under consideration. [5]

Lone atrial fibrillation (LAF) is defined as atrial fibrillation in the absence of clinical or echocardiographic findings of cardiopulmonary disease, including hypertension. [5]

Signs and symptoms

Atrial fibrillation is usually accompanied by symptoms related to a 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. A palpitation (medical term ectopic heart beat) is an abnormal awareness of the beating of the Heart, whether it is too slow too fast irregular Angina pectoris, commonly known as angina, is severe Chest pain due to Ischemia (a lack of blood and hence Oxygen supply of the heart Heart failure is a Cardiac condition that occurs when a problem with the structure or function of the Heart impairs its ability to supply Dyspnea or dyspnoea (pronounced disp-nee-ah, IPA /dɪsp'niə/ from Latin dyspnoea, from Greek dyspnoia from Oedema (or Edema in American English formerly known as dropsy or hydropsy, is the increase of Interstitial fluid in any organ &mdash swelling Sometimes the arrhythmia will be identified only with the onset of a stroke or a transient ischemic attack (TIA). A transient ischemic attack ( TIA, often colloquially referred to as “ mini stroke ” is caused by the changes in the blood supply to a particular area of the It is not uncommon for a patient to first become aware of AF from a routine physical examination or ECG, as it may be asymptomatic in many cases. [5]

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. In Medicine, chest pain is a Symptom of a number of serious conditions and is generally considered a Medical emergency. Hyperthyroidism is the term for overactive tissue within the Thyroid gland resulting in overproduction and thus an excess of circulating free thyroid hormones Thyroxine The thyroid is one of the largest Endocrine glands in the body 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 In Medicine, diarrhea, also spelled diarrhoea (see spelling differences) is frequent loose or liquid Bowel movements Acute diarrhea 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 AF is at a higher risk of complications. Hypertension, also referred to as high blood pressure, HTN or HPN, is a medical condition in which the Blood pressure is chronically elevated Diabetes mellitus (ˌdaɪəˈbiːtiːz or /ˌdaɪəˈbiːtəs/ /məˈlaɪtəs/ or /ˈmɛlətəs/ often referred to simply as diabetes ( Ancient Greek: grc Heart failure is a Cardiac condition that occurs when a problem with the structure or function of the Heart impairs its ability to supply Rheumatic fever is an Autoimmune inflammatory Disease which may develop two to three weeks after a Group A streptococcal infection (such as [5]

Diagnosis

The evaluation of atrial fibrillation involves diagnosis, determination of the etiology of the arrhythmia, and classification of the arrhythmia. A minimal evaluation should be performed in all individuals with AF. This includes a history and physical examination, ECG, 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 ECGs during routine office visits found that the annual rate of detection of AF in elderly patients improved from 1. Screening, in medicine is a strategy used in a Population to detect a Disease in individuals without signs or Symptoms of that disease 04% to 1. 63%; selection of patients for prophylactic anticoagulation would improve stroke risk in that age category. [7]

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. [7]

Minimal evaluation

The minimal evaluation of atrial fibrillation should generally be performed in all individuals with AF. 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 AF (in which case the AF is found as an incidental finding on an ECG or physical examination) and those who have gross and obvious symptoms due to AF and can pinpoint whenever they go into AF 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. Renal function, in Nephrology, is an indication of the state of the Kidney and its role in Renal physiology. An electrolyte is any substance containing free Ions that behaves as an electrically conductive medium Thyroid-stimulating hormone (also known as TSH or thyrotropin) is a Peptide hormone synthesized and secreted by Thyrotrope cells in the Hyperthyroidism is the term for overactive tissue within the Thyroid gland resulting in overproduction and thus an excess of circulating free thyroid hormones Thyroxine Amiodarone is an Antiarrhythmic agent (medication used for irregular heart beat used for various types of tachyarrhythmias (fast forms of irregular heart beat both ventricular A complete blood count ( CBC) also known as full blood count ( FBC) or full blood exam ( FBE) or blood panel, is [5]

In acute-onset AF associated with chest pain, cardiac troponins or other markers of damage to the heart muscle may be ordered. In Medicine, chest pain is a Symptom of a number of serious conditions and is generally considered a Medical emergency. Troponin is a complex of three regulatory proteins that is integral to Muscle contraction in skeletal and Cardiac muscle, but not Smooth muscle Coagulation studies (INR/aPTT) are usually performed, as anticoagulant medication may be commenced. Coagulation is a complex process by which Blood forms Clots It is an important part of Hemostasis (the cessation of blood loss from a damaged vessel whereby The prothrombin time ( PT) and its derived measures of prothrombin ratio ( PR) and international normalized ratio ( INR) are measures An anticoagulant is a substance that prevents coagulation; that is it stops Blood from clotting [5]

Electrocardiogram

ECG of atrial fibrillation (top) and sinus rhythm (bottom). The purple arrow indicates a P wave, which is lost in atrial fibrillation.
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 (ECG), 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. [5]

When ECGs 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:[8]:

If paroxysmal AF is suspected but an ECG during an office visit only shows a regular rhythm, AF episodes may be detected and documented with the use of ambulatory Holter monitoring (e. A primary care physician, or PCP, is a Physician / medical doctor who provides both the first contact for a person with an undiagnosed health concern as well In Medicine, a Holter monitor (also called an ambulatory electrocardiography device) named after its inventor Dr g. for a day). If the episodes are too infrequent to be detected by Holter monitoring with reasonable probability, then the patient can be monitored for longer periods (e. g. a month) with an ambulatory event monitor. A cardiac event monitor is a device used to monitor patients with transient Cardiac symptoms [5]

Echocardiography

A non-invasive transthoracic echocardiogram (TTE) is generally performed in newly diagnosed AF, as well as if there is a major change in the patient's clinical state. An echocardiogram is a Sonography of the Heart. Also known as a cardiac ultrasound it uses standard ultrasound techniques to image two-dimensional slices of 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. Valvular heart disease is any disease process involving one or more of the valves of the heart (the aortic and mitral valves on the left and the pulmonary In Medicine, pulmonary hypertension (PH is an increase in blood pressure in the Pulmonary artery, Pulmonary vein, or pulmonary capillaries together known [5]

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

A chest X-ray is generally only performed if a pulmonary cause of atrial fibrillation is suggested, or if other cardiac conditions are suspected (particularly congestive heart failure. A chest X-ray, commonly abbreviated CXR, is a projection radiograph ( X-ray) taken by a Radiographer, of the Thorax which is used Heart failure is a Cardiac condition that occurs when a problem with the structure or function of the Heart impairs its ability to supply ) This may reveal an underlying problem in the lungs or the blood vessels in the chest. [5] In particular, if an underlying pneumonia is suggested, then treatment of the pneumonia may cause the atrial fibrillation to terminate on its own.

Transesophageal echocardiogram

A normal echocardiography (transthoracic or TTE) has a low sensitivity for identifying thrombi (blood clots) in the heart. A thrombus, or blood clot, is the final product of the Blood coagulation step in Hemostasis. If this is suspected - e. g. when planning urgent electrical cardioversion - a transesophageal echocardiogram (TEE) is preferred. An echocardiogram is a Sonography of the Heart. Also known as a cardiac ultrasound it uses standard ultrasound techniques to image two-dimensional slices of [5]

The TEE has much better visualization of the left atrial appendage than transthoracic echocardiography. The left atrial appendage (LAA (left auricular appendix left auricula left auricle is a conical muscular pouch connected to the Left atrium of the Heart. This structure, located in the left atrium, is the place where thrombus most commonly is formed in the setting of atrial fibrillation or flutter. The left atrium is one of the four chambers in the Human Heart. TEE has a very high sensitivity for locating thrombus in this area and can also detect sluggish bloodflow in this area that is suggestive of thrombus formation.

If no thrombus is seen on TEE, the incidence of stroke immediately after cardioversion is performed is very low.

Ambulatory holter monitoring

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 Medicine, a Holter monitor (also called an ambulatory electrocardiography device) named after its inventor Dr 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.

Exercise stress testing

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 that indirectly reflects arterial Blood flow to the Heart during Physical exercise

Etiology

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

Pathophysiology

Morphology

The primary pathologic 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 almost 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. Lamins are Fibrous proteins providing structural function and transcriptional regulation in the Cell nucleus.

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. The renin-angiotensin system (RAS or the renin-angiotensin-aldosterone system (RAAS is a hormone system that regulates Blood pressure and water ( fluid

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. The Sinoatrial node (abbreviated SA node or SAN, also called the sinus node) is the impulse generating (pacemaker tissue located in the Right atrium The atrioventricular node (abbreviated AV node) is an area of specialized tissue between the atria and the ventricles of the Heart, specifically Sick sinus syndrome, also called Sinus node dysfunction, is a group of abnormal heart rhythms ( Arrhythmias presumably caused by a malfunction of the Sinus Prolonged episodes of atrial fibrillation have been shown to correlate with prolongation of the sinus node recovery time,[5] [12][13] suggesting that dysfunction of the SA node is progressive with prolonged episodes of atrial fibrillation.

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). 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 The Sinoatrial node (abbreviated SA node or SAN, also called the sinus node) is the impulse generating (pacemaker tissue located in the Right atrium Myocardium is the muscular tissue of the Heart. Relationship to other layers The other tissues of the heart are the Endocardium 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.

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. The four pulmonary veins carry Oxygen -rich Blood from the Lungs to the left atrium of the Heart. 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 ECG; 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. Atrial flutter is an abnormal 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 left atrial appendage and predisposes to clotting. The left atrial appendage (LAA (left auricular appendix left auricula left auricle is a conical muscular pouch connected to the Left atrium of the Heart. Coagulation is a complex process by which Blood forms Clots It is an important part of Hemostasis (the cessation of blood loss from a damaged vessel whereby 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 as bowel ischemia or ischemia of the fingers or toes. This article concerns ischemia of the small bowel See Ischemic colitis for ischemia of the large bowel Mesenteric ischemia (Mesenteric

Treatment

The main goals of treatment of atrial fibrillation are to prevent temporary circulatory instability and to prevent stroke. A stroke is the rapidly developing loss of brain functions due to a disturbance in the blood vessels supplying blood to the brain Rate and rhythm control are principally used to achieve the former, while anticoagulation may be required to decrease the risk of the latter. An anticoagulant is a substance that prevents coagulation; that is it stops Blood from clotting [14] In emergencies, when circulatory collapse is imminent due to uncontrolled tachycardia, immediate cardioversion may be indicated. Synchronized electrical cardioversion is the process by which an abnormally fast Heart rate or Cardiac arrhythmia is terminated by the delivery of a therapeutic dose [5]

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. Synchronized electrical cardioversion is the process by which an abnormally fast Heart rate or Cardiac arrhythmia is terminated by the delivery of a therapeutic dose If rate and rhythm control can not be maintained by medication or cardioversion, electrophysiological studies with pathway ablation may be required. Cardiac electrophysiology is the Science of elucidating diagnosing and treating the electrical activities of the Heart. Radio Frequency Ablation ( RFA) of Lung kidney breast bone and Liver tumors RFA is performed to cure tumors in lung liver kidney bone and rarely in other [5]

Anticoagulation

Most patients with AF are at increased risk of stroke. The possible exceptions are those with lone AF (LAF). [3] 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, and diabetes. A systematic review is a Literature review focused on a single question which tries to identify appraise select and synthesize all high quality research evidence relevant to A stroke is the rapidly developing loss of brain functions due to a disturbance in the blood vessels supplying blood to the brain [15] For patients under the age of 60 with LAF, the risk of stroke is very low and is independent of whether the LAF was an isolated episode, paroxysmal, persistent, or permanent. [16] 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. Mitral Stenosis is a Valvular heart disease characterized by the narrowing of the orifice of the Mitral valve of the Heart. 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). Bleeding, technically known as hemorrhaging / haemorrhaging (see American and British spelling differences) is the loss of Blood from Those at a low risk may benefit from mild (and low-risk) anticoagulation with aspirin (or clopidogrel in those who are allergic to aspirin). Aspirin, or acetylsalicylic acid (ASA (əˌsɛtɨlsælɨˌsɪlɨk ˈæsɨd is a Salicylate drug, often used as an Analgesic to relieve Clopidogrel is a potent oral antiplatelet agent often used in the treatment of Coronary artery disease, Peripheral vascular disease, and Cerebrovascular In contrast, those with a high risk of stroke derive most benefit from anticoagulant treatment with warfarin or similar drugs. An anticoagulant is a substance that prevents coagulation; that is it stops Blood from clotting Warfarin (also known under the brand names Coumadin, Jantoven, Marevan, and Waran) is an Anticoagulant.

In the United Kingdom, the NICE guidelines recommend using a clinical prediction rule for this purpose. The United Kingdom of Great Britain and Northern Ireland, commonly known as the United Kingdom, the UK or Britain,is a Sovereign state located 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 [17] The CHADS2 score is the best validated clinical prediction rule for determining the 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 as hypertension and diabetes. CHADS score or CHADS2 score is a Clinical prediction rule for estimating the risk of Stroke in patients with non rheumatic In a comparison of seven prediction rules, the best was CHADS2 which performed similarly to the SPAF[18] and Framingham[19] prediction rules. 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 CHADS score or CHADS2 score is a Clinical prediction rule for estimating the risk of Stroke in patients with non rheumatic 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 [20]

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 from AF. [21][22]

Atrial fibrillation in the context of mitral stenosis is associated with a seventeen-fold increase in stroke risk. [4]

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 will 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

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). [23] 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. A medical guideline (also called a clinical guideline, clinical protocol or clinical practice guideline) is a document with the aim of guiding decisions [17]

In cases of chronic stable atrial fibrillation without any other risk factors for thromboembolism, the Seventh American College of Chest Physicians (ACCP) Conference on Antithrombotic and Thrombolytic Therapy recommends initiating warfarin without heparin bridging. [24] While there is a theoretical concern of causing a transient prothombotic state with the initiation of warfarin, a study comparing the initiation of warfarin alone with warfarin and low molecular weight heparin shows no significant difference in the concentrations of endogenous anticoagulants or in markers of active clot formation. In Medicine, low-molecular-weight heparin ( LMWH) is a class of Medication used as an Anticoagulant in diseases that feature Thrombosis [25]

Chronic anticoagulation

Among patients with "non-valvular" atrial fibrillation, anticoagulation with warfarin can reduce stroke by 60% while antiplatelet agents can reduce stroke by 20%. [26][27]. There is evidence that aspirin and clopidogrel are effective when used together, but the combination is still inferior to warfarin. Aspirin, or acetylsalicylic acid (ASA (əˌsɛtɨlsælɨˌsɪlɨk ˈæsɨd is a Salicylate drug, often used as an Analgesic to relieve Clopidogrel is a potent oral antiplatelet agent often used in the treatment of Coronary artery disease, Peripheral vascular disease, and Cerebrovascular Warfarin (also known under the brand names Coumadin, Jantoven, Marevan, and Waran) is an Anticoagulant. [28]

Warfarin treatment requires frequent monitoring with a blood test called the international normalized ratio (INR); this determines whether the correct dose is being used. The prothrombin time ( PT) and its derived measures of prothrombin ratio ( PR) and international normalized ratio ( INR) are measures 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). An artificial heart valve is a device which is implanted in the heart of patients who suffer from valvular diseases in their heart A high INR may indicate increased bleeding risk, while a low INR would indicate that there is insufficient protection from stroke.

An attempt was made to find a better method of implementing warfarin therapy without the inconvenience of regular monitoring and risk of intracranial hemorrhage. A combination of aspirin and fixed-dose warfarin (initial INR 1. 2-1. 5) was tried. Unfortunately, in a study of AF patients with additional risk factors for thromboembolism, the combination of aspirin and the lower dose of warfarin was significantly inferior to the standard adjusted-dose warfarin (INR 2. 0-3. 0), yet still had a similar risk of intracranial hemorrhage. [29]

Elderly patients

The very elderly (patients aged 75 years or more) may benefit from anticoagulation provided that their anticoagulation 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. [30] 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. A randomized controlled trial (RCT is a type of scientific Experiment most commonly used in testing the Efficacy or Effectiveness of Healthcare The number needed to treat (NNT is an epidemiological measure used in assessing the effectiveness of a health-care intervention typically a treatment with Medication [31] Of note, this study had very low rate of hemorrhagic complications in the warfarin group.

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. A palpitation (medical term ectopic heart beat) is an abnormal awareness of the beating of the Heart, whether it is too slow too fast irregular Angina pectoris, commonly known as angina, is severe Chest pain due to Ischemia (a lack of blood and hence Oxygen supply of the heart Furthermore, AF with a persistent rapid rate can cause a form of heart failure called tachycardia induced cardiomyopathy. Heart failure is a Cardiac condition that occurs when a problem with the structure or function of the Heart impairs its ability to supply Tachycardia induced cardiomyopathy, also known as chronotropic cardiomyopathy and tachycardiomyopathy, is a weakening of the Myocardium (the muscle of the This can significantly increase mortality and morbidity, which can be prevented by early and adequate treatment of the AF.

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. [32]

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. [32] AF is associated with a reduced quality of life, and while some studies indicate that rhythm control leads to a higher quality of life, the AFFIRM study did not find a difference. [33]

In patients with a fast ventricular response, intravenous magnesium significantly increases the chances of successful rate and rhythm control in the urgent setting without significant side-effects. Magnesium (mægˈniːziəm is a Chemical element with the symbol Mg, Atomic number 12 Atomic weight 24 [34]

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:[5]

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). Diltiazem is a member of the group of drugs known as Benzothiazepines which are a class of Calcium channel blockers used in the treatment of Hypertension Verapamil (brand names Isoptin, Verelan, Calan, Bosoptin, Covera-HS) is an L-type Calcium channel blocker. Amiodarone is an Antiarrhythmic agent (medication used for irregular heart beat used for various types of tachyarrhythmias (fast forms of irregular heart beat both ventricular

Cardioversion

Rhythm control methods include electrical and chemical cardioversion:[5]

The main risk of cardioversion is systemic embolization of a thrombus (blood clot) from the previously fibrillating left atrium. A thrombus, or blood clot, is the final product of the Blood coagulation step in Hemostasis. 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. An echocardiogram is a Sonography of the Heart. Also known as a cardiac ultrasound it uses standard ultrasound techniques to image two-dimensional slices of [5]

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. A relapse (etymologically "who falls again" occurs when a person is affected again by a condition that affected them in the past 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.

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

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. Antiarrhythmic agents are a group of Pharmaceuticals that are used to suppress fast rhythms of the Heart ( Cardiac arrhythmias) such as Atrial fibrillation These medications are often used in concert with electrical cardioversion.

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. The atrioventricular node (abbreviated AV node) is an area of specialized tissue between the atria and the ventricles of the Heart, specifically For other uses see Pacemaker (disambiguation A pacemaker (or artificial pacemaker, so as not to be confused with the heart's natural pacemaker 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. [5]

Ablation is a newer technique and has shown some promise for cases of recurrent AF that are unresponsive to conventional treatments. Ablation is defined as the removal of material from the surface of an object by Vaporization, Chipping, or other erosive processes Radiofrequency ablation (RFA) uses radiofrequency energy to destroy abnormal electrical pathways in heart tissue. Radio Frequency Ablation ( RFA) of Lung kidney breast bone and Liver tumors RFA is performed to cure tumors in lung liver kidney bone and rarely in other The energy emitting probe (electrode) is placed into the heart through a catheter inserted into veins in the groin or neck. An electrode is an Electrical conductor used to make contact with a nonmetallic part of a circuit (e In Medicine a catheter is a tube that can be inserted into a body cavity duct or vessel 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.

Most AF ablations consist of isolating the electrical pathways from the pulmonary veins (PV)[36], which are located on the posterior wall of the left atrium. The four pulmonary veins carry Oxygen -rich Blood from the Lungs to the left atrium of the Heart. All other 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 transseptal approach. Once in the left atrium, the physician may perform Wide Area Circumferential Ablation (WACA) to electrically isolate the PVs from the left atrium. [37]

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). The coronary sinus is a collection of veins joined together to form a large vessel that collects blood from the Myocardium of the Heart. These sites are termed complex fractionated atrial electrogram (CFAE) sites. [38]. 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), microwave ablation, where tissue is ablated by the microwave energy "cooking" the adjacent tissue, and high intensity focused ultrasound (HIFU), which destroys tissue by heating. Cryoablation is a process that uses cold energy (cryo to kill tissue (ablation 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.

Efficacy and risks of catheter ablation of atrial fibrillation are areas of active debate. A worldwide survey of the outcomes of 8745 ablation procedures[39] demonstrated a 52% success rate (ranging from 14. 5% to 76. 5% among centers), with an additional 23. 9% of patients becoming asymptomatic with addition of an antiarrhythmic medication. In 27. 3% of patients, more than one procedure was required to attain these results. There was at least one major complication in 6% of patients. A thorough discussion of results of catheter ablation was published in 2007[40]; it notes that results are widely variable, due in part to differences in technique, follow-up, definitions of success, use of antiarrhythmic therapy, and in experience and technical proficiency.

Surgical 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. The Cox maze procedure is a type of heart surgery for Atrial fibrillation. "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". [41]

Minimaze surgery is minimally invasive cardiac surgery similarly intended to cure atrial fibrillation. The mini-maze procedures are Cardiac surgery procedures intended to cure Atrial fibrillation (AF a common disturbance of heart rhythm The "minimaze" procedures are "mini" versions of the original Cox maze procedure. The Cox maze procedure is a type of heart surgery for Atrial fibrillation. 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). The Cox maze procedure is a type of heart surgery for Atrial fibrillation. Cardiopulmonary bypass (CPB is a technique that temporarily takes over the function of the Heart and Lungs during surgery maintaining the circulation of blood They use microwave, radiofrequency, or acoustic energy to ablate atrial tissue near the pulmonary veins.

Epidemiology

Atrial fibrillation is the most common arrhythmia found in clinical practice. [5] It also accounts for 1/3 of hospital admissions for cardiac rhythm disturbances[5], and the rate of admissions for AF has risen in recent years. [42] Approximately 2. 2 million individuals in the United States and 4. 5 million in the European Union have AF. [5][43]

The incidence of atrial fibrillation increases with age. The prevalence in individuals over the age of 80 is about 8%. [44] 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. [45]

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. Edmé Félix Alfred Vulpian ( January 5, 1826, Paris, France – May 18, 1887) was a French Physician and [46] In the mid-eighteenth century, Jean-Baptiste de Sénac made note of dilated, irritated atria in people with mitral stenosis. Jean-Baptiste de Sénac (1693-1770 was a French physician who was born in the town of Lombez. Mitral Stenosis is a Valvular heart disease characterized by the narrowing of the orifice of the Mitral valve of the Heart. [47] 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. Carl Wilhelm Hermann Nothnagel ( September 28, 1841 - July 7, 1905) was a German Internist who in 1876 described the irregular pulse At the same time, the height and tension of the individual pulse waves are continuously changing". [48] 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. The jugular venous pressure (JVP sometimes referred to as jugular venous pulse) is the indirectly observed pressure over the venous system. [49] Willem Einthoven published the first ECG showing AF in 1906. Willem Einthoven ( Semarang, May 21, 1860 &ndash Leiden, September 29, 1927) was a Dutch doctor and physiologist [50] 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. [51][52][53]

See also

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External links

Dictionary

atrial fibrillation

-noun

  1. A cardiac arrhythmia (abnormal heart rhythm) that involves the two upper chambers (atria) of the heart.
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