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Arrhythmia, also known as cardiac arrhythmia or heart arrhythmia, is a group of conditions in which the
heartbeat Heartbeat or heartbeats may refer to: Physiology *Cardiac cycle, of the heart *Contraction of the cardiac muscle, muscles of the heart, or a perceived effect of it, such as: **Heart sounds, the noises generated by the beating heart and the resulta ...
is irregular, too fast, or too slow. The
heart rate Heart rate is the speed of the heartbeat Heartbeat or heartbeats may refer to: Physiology *Cardiac cycle, of the heart *Contraction of the cardiac muscle, muscles of the heart, or a perceived effect of it, such as: **Heart sounds, the noises gene ...

heart rate
that is too fast – above 100 beats per minute in adults – is called
tachycardia Tachycardia, also called tachyarrhythmia, is a heart rate that exceeds the normal resting rate. In general, a resting heart rate over 100 beats per minute is accepted as tachycardia in adults. Heart rates above the resting rate may be normal (s ...
, and a heart rate that is too slow – below 60 beats per minute – is called
bradycardia Bradycardia is a condition typically defined wherein an individual has a resting heart rateHeart rate is the speed of the heartbeat measured by the number of contractions (beats) of the heart The heart is a muscle, muscular Organ (anatom ...
. Some types of arrhythmias have no
symptoms Signs and symptoms are the observed or detectable signs, and experienced symptoms of an illness, injury, or condition. A sign for example may be a higher or lower temperature than normal, raised or lowered blood pressure or an abnormality showi ...

symptoms
. Symptoms, when present, may include
palpitations Palpitations are perceived abnormalities of the heartbeat characterized by awareness of cardiac muscle contractions in the chest, which is further characterized by the hard, fast and/or irregular beatings of the heart. Symptoms include a rapid ...
or feeling a pause between heartbeats. In more serious cases, there may be
lightheadedness Lightheadedness is a common and typically unpleasant sensation of dizziness or a feeling that one may faint. The sensation of lightheadedness can be short-lived, prolonged, or, rarely, recurring. In addition to dizziness, the individual may feel ...
, passing out,
shortness of breath Shortness of breath (SOB), also known as dyspnea (BrE British English (BrE) is the standard dialect A standard language (also standard variety, standard dialect, and standard) is a language variety that has undergone substantial codificat ...
or
chest pain Chest pain is pain or discomfort in the chest, typically the front of the chest. It may be described as sharp, dull, pressure, heaviness or squeezing. Associated symptoms may include pain in the shoulder, arm, upper abdomen, or jaw, along with na ...
. While most types of arrhythmia are not serious, some predispose a person to complications such as
stroke A stroke is a medical condition A disease is a particular abnormal condition that negatively affects the structure or function (biology), function of all or part of an organism, and that is not due to any immediate external injury. Dis ...

stroke
or
heart failure Heart failure (HF), also known as congestive heart failure (CHF) and (congestive) cardiac failure (CCF), is a Syndrome, set of manifestations caused by the failure of the heart's function as a pump supporting the Circulatory system, blood flow t ...
. Others may result in sudden death. There are four main groups of arrhythmia: extra beats,
supraventricular tachycardia Supraventricular tachycardia (SVT) is an umbrella term for arising from the . This is in contrast to the other group of fast heart rhythms - , which start within the . There are four main types of SVT: , , (PSVT) and . The symptoms of SVT incl ...
s,
ventricular arrhythmia Arrhythmia, also known as cardiac arrhythmia or heart arrhythmia, is a group of conditions in which the is irregular, too fast, or too slow. The that is too fast – above 100 beats per minute in adults – is called , and a heart rate that i ...
s and
bradyarrhythmia Bradycardia is a condition typically defined wherein an individual has a resting heart rate of under 60 beats per minute (BPM) in adults, although some studies use a heart rate of less than 50 BPM. Bradycardia typically does not cause symptoms u ...
s. Extra beats include
premature atrial contraction Premature atrial contractions (PACs), also known as atrial premature complexes (APC) or atrial premature beats (APB), are a common cardiac dysrhythmia Arrhythmia, also known as cardiac arrhythmia or heart arrhythmia, is a group of conditions i ...
s,
premature ventricular contraction :This is the article for the heart condition generally referred to as PVC. For PVC pipe, see Polyvinyl chloride''. A premature ventricular contraction (PVC) is a relatively common event where the heart rate, heartbeat is initiated by Purkinje fi ...
s and
premature junctional contractionsPremature junctional contractions (PJCs), also called atrioventricular junctional premature complexes or junctional extrasystole, are premature cardiac electrical impulses originating from the atrioventricular node of the heart or "junction". This a ...
. Supraventricular tachycardias include
atrial fibrillation Atrial fibrillation (AF or A-fib) is an abnormal heart rhythm (arrhythmia) characterized by the rapid and irregular beating of the atrial chambers of the heart. It often begins as short periods of abnormal beating, which become longer or cont ...

atrial fibrillation
,
atrial flutter Atrial flutter (AFL) is a common abnormal heart rhythm that starts in the atrial chambers of the heart The heart is a muscle, muscular Organ (anatomy), organ in most animals, which pumps blood through the blood vessels of the circulatory ...
and
paroxysmal supraventricular tachycardia Paroxysmal supraventricular tachycardia (PSVT) is a type of supraventricular tachycardia, named for its intermittent episodes of abrupt onset and termination. Often people have no symptoms. Otherwise symptoms may include palpitations, feeling lig ...
. Ventricular arrhythmias include
ventricular fibrillation Ventricular fibrillation (V-fib or VF) is an abnormal heart rhythm in which the ventricles of the heart The heart is a cardiac muscle, muscular Organ (biology), organ in most animals, which pumps blood through the blood vessels of the ci ...

ventricular fibrillation
and
ventricular tachycardia Ventricular tachycardia (V-tach or VT) is a type of regular, fast heart rate that arises from improper electrical activity in the ventricles of the heart The heart is a muscle, muscular Organ (anatomy), organ in most animals, which pump ...
. Arrhythmias are due to problems with the
electrical conduction system of the heart The electrical conduction system of the heart transmits signals generated usually by the sinoatrial node to cause contraction of the heart muscle. The Cardiac pacemaker, pacemaking signal generated in the sinoatrial node travels through the right ...

electrical conduction system of the heart
. Arrhythmias may also occur in children; however, the normal range for the heart rate is different and depends on age. A number of tests can help with diagnosis, including an
electrocardiogram Electrocardiography is the process of producing an electrocardiogram (ECG or EKG). It is a graph of voltage Voltage, electric potential difference, electromotive force emf, electric pressure or electric tension is the difference in elec ...

electrocardiogram
(ECG) and
Holter monitor In medicine Medicine is the Art (skill), art, science, and Praxis (process) , practice of caring for a patient and managing the diagnosis, prognosis, Preventive medicine, prevention, therapy, treatment or Palliative care , palliation of their ...

Holter monitor
. Most arrhythmias can be effectively treated. Treatments may include medications, medical procedures such as inserting a
pacemaker A cardiac pacemaker (or artificial pacemaker, so as not to be confused with the natural pacemaker of the heart The heart is a muscle, muscular Organ (anatomy), organ in most animals, which pumps blood through the blood vessels of the cir ...

pacemaker
, and surgery. Medications for a fast heart rate may include
beta blockers Beta blockers (beta-blockers, β-blockers, etc.) are a class of medications that are predominantly used to manage cardiac arrhythmia, abnormal heart rhythms, and to protect the heart from a second heart attack (myocardial infarction) after a firs ...
, or
antiarrhythmic agent Antiarrhythmic agents, also known as cardiac dysrhythmia medications, are a group of pharmaceuticals that are used to suppress abnormal rhythms of the heart (cardiac arrhythmias), such as atrial fibrillation, atrial flutter, ventricular tachycardia ...
s such as
procainamide Procainamide is a medication of the antiarrhythmic class used for the treatment of cardiac arrhythmias. It is classified by the Vaughan Williams classification system as class Ia; thus it is a sodium channel blocker of cardiomyocytes. In addit ...

procainamide
, which attempt to restore a normal heart rhythm. This latter group may have more significant side effects, especially if taken for a long period of time. Pacemakers are often used for slow heart rates. Those with an irregular heartbeat are often treated with blood thinners to reduce the risk of complications. Those who have severe symptoms from an arrhythmia may receive urgent treatment with a controlled electric shock in the form of
cardioversion Cardioversion is a medical procedure A medical procedure is a course of action intended to achieve a result in the delivery of healthcare. A medical procedure with the intention of determining, measuring, or diagnosing a patient condition or para ...

cardioversion
or
defibrillation Defibrillation is a treatment for life-threatening cardiac dysrhythmia Arrhythmia, also known as cardiac arrhythmia or heart arrhythmia, is a group of conditions in which the heartbeat is irregular, too fast, or too slow. The heart rate tha ...
. Arrhythmia affects millions of people. In Europe and North America, as of 2014, atrial fibrillation affects about 2% to 3% of the population. Atrial fibrillation and atrial flutter resulted in 112,000 deaths in 2013, up from 29,000 in 1990.
Sudden cardiac death Cardiac arrest is a sudden loss of blood flow resulting from the failure of the heart The heart is a muscle, muscular Organ (anatomy), organ in most animals, which pumps blood through the blood vessels of the circulatory system. The pump ...
is the cause of about half of deaths due to
cardiovascular disease Cardiovascular disease (CVD) is a class of diseases that involve the heart The heart is a cardiac muscle, muscular Organ (biology), organ in most animals, which pumps blood through the blood vessels of the circulatory system. The pumped ...
and about 15% of all deaths globally. About 80% of sudden cardiac death is the result of ventricular arrhythmias. Arrhythmias may occur at any age, but are more common among older people.


Classification

Arrhythmia may be classified by rate (
tachycardia Tachycardia, also called tachyarrhythmia, is a heart rate that exceeds the normal resting rate. In general, a resting heart rate over 100 beats per minute is accepted as tachycardia in adults. Heart rates above the resting rate may be normal (s ...
,
bradycardia Bradycardia is a condition typically defined wherein an individual has a resting heart rateHeart rate is the speed of the heartbeat measured by the number of contractions (beats) of the heart The heart is a muscle, muscular Organ (anatom ...
), mechanism (automaticity, re-entry, triggered) or duration (isolated premature beats; couplets; runs, that is 3 or more beats; non-sustained= less than 30 seconds or sustained= over 30 seconds). It is also appropriate to classify by site of origin:


Atrial arrhythmia

*
Sinus bradycardia Sinus bradycardia Bradycardia is a condition typically defined wherein an individual has a resting heart rate of under 60 beats per minute (BPM) in adults, although some studies use a heart rate of less than 50 BPM. Bradycardia typically does ...
* Premature atrial contractions (PACs) * Wandering atrial pacemaker *
Atrial tachycardia Atrial tachycardia is a type of heart rhythm problem in which the heart The heart is a muscle, muscular Organ (anatomy), organ in most animals, which pumps blood through the blood vessels of the circulatory system. The pumped blood carries ...
*
Multifocal atrial tachycardia Multifocal (or multiform) atrial tachycardia (MAT) is an abnormal heart rhythm, specifically a type of supraventricular tachycardia, that is particularly common in older people and is associated with exacerbations of chronic obstructive pulmonary ...
* Supraventricular tachycardia (SVT) *
Atrial flutter Atrial flutter (AFL) is a common abnormal heart rhythm that starts in the atrial chambers of the heart The heart is a muscle, muscular Organ (anatomy), organ in most animals, which pumps blood through the blood vessels of the circulatory ...
* *
AV nodal reentrant tachycardia AV-nodal reentrant tachycardia (AVNRT) is a type of abnormal fast heart rhythm. It is a type of supraventricular tachycardia (SVT), meaning that it originates from a location within the heart above the bundle of His. AV nodal reentrant tachycar ...

AV nodal reentrant tachycardia


Junctional arrhythmia

*
AV nodal reentrant tachycardia AV-nodal reentrant tachycardia (AVNRT) is a type of abnormal fast heart rhythm. It is a type of supraventricular tachycardia (SVT), meaning that it originates from a location within the heart above the bundle of His. AV nodal reentrant tachycar ...

AV nodal reentrant tachycardia
*
Junctional rhythm Junctional rhythm describes an abnormal heart rhythm resulting from impulses coming from a locus of tissue in the area of the atrioventricular node The atrioventricular node or AV node is a part of the electrical conduction system of the heart Th ...
*
Junctional tachycardia Junctional tachycardia is a form of supraventricular tachycardia characterized by involvement of the AV node. It can be contrasted to atrial tachycardia. It is a tachycardia associated with the generation of impulses in a focus in the region of ...
*
Premature junctional contractionPremature junctional contractions (PJCs), also called atrioventricular junctional premature complexes or junctional extrasystole, are premature cardiac electrical impulses originating from the atrioventricular node The atrioventricular node or AV nod ...


Ventricular arrhythmia

*
Premature ventricular contraction :This is the article for the heart condition generally referred to as PVC. For PVC pipe, see Polyvinyl chloride''. A premature ventricular contraction (PVC) is a relatively common event where the heart rate, heartbeat is initiated by Purkinje fi ...
s (PVCs), sometimes called ventricular extra beats (VEBs) **Premature ventricular beats occurring after every normal beat are termed ventricular bigeminy **PVCs that occur at intervals of 2 normal beats to 1 PVC are termed "PVCs in trigeminy" **Three premature ventricular groups are termed a "run of PVCs" in general, runs lasting longer than three beats with an increased heart rate are referred to as ventricular tachycardia * Accelerated idioventricular rhythm *
Monomorphic ventricular tachycardia Ventricular tachycardia (V-tach or VT) is a type of regular, fast heart rate that arises from improper electrical activity in the ventricles of the heart The heart is a muscle, muscular Organ (anatomy), organ in most animals, which pump ...
*
Polymorphic ventricular tachycardia Ventricular tachycardia (V-tach or VT) is a type of regular, fast heart rate that arises from improper electrical activity in the ventricles of the heart The heart is a muscle, muscular Organ (anatomy), organ in most animals, which pump ...
*
Ventricular fibrillation Ventricular fibrillation (V-fib or VF) is an abnormal heart rhythm in which the Ventricle (heart), ventricles of the heart Fibrillation, quiver. It is due to disorganized electrical conduction system of the heart, electrical activity. Ventricular ...

Ventricular fibrillation
*
Torsades de pointes ''Torsades de pointes, torsade de pointes'' or ''torsades des pointes'' (TdP) (, , translated as "twisting of peaks") is a specific type of abnormal heart rhythm that can lead to sudden cardiac death Cardiac arrest is a sudden loss of blood ...
*
Arrhythmogenic right ventricular dysplasia Arrhythmogenic cardiomyopathy (ACM), arrhythmogenic right ventricular dysplasia (ARVD), or arrhythmogenic right ventricular cardiomyopathy (ARVC), is an inherited heart disease. ACM is caused by Genetic disorder, genetic defects of the parts of ...
*
Re-entry ventricular arrhythmia Re-entry ventricular arrhythmia is a type of paroxysmal tachycardia occurring in the ventricle (heart), ventricle where the cause of the Heart arrhythmia, arrhythmia is due to the electric signal not completing the normal circuit, but rather an al ...


Heart blocks

These are also known as AV blocks, because the vast majority of them arise from pathology at the
atrioventricular node The atrioventricular node or AV node is a part of the electrical conduction system of the heart The electrical conduction system of the heart transmits signals generated usually by the sinoatrial node to cause contraction of the heart muscle. Th ...
. They are the most common causes of bradycardia: * First-degree heart block, which manifests as PR prolongation * Second-degree heart block ** Type 1 Second degree heart block, also known as
Mobitz I Second-degree atrioventricular block (AV block) is a disease of the electrical conduction system of the heart The electrical conduction system of the heart transmits signals generated usually by the sinoatrial node to cause contraction of the ...
or Wenckebach ** Type 2 Second degree heart block, also known as Mobitz II *
Third-degree heart block Third-degree atrioventricular block (AV block) is a medical condition in which the nerve impulse generated in the sinoatrial node (SA node) in the atrium of the heart The heart is a muscle, muscular Organ (anatomy), organ in most animals ...
, also known as
complete heart block Third-degree atrioventricular block (AV block) is a medical condition in which the nerve impulse generated in the sinoatrial node The sinoatrial node (also known as the sinuatrial node, SA node or sinus node) is a group of cells located in the w ...
. First, second, and third-degree blocks also can occur at the level of the sinoatrial junction. This is referred to as
sinoatrial block A sinoatrial block (also spelled sinuatrial block) is a disorder in the normal rhythm of the heart, known as a heart block, that is initiated in the sinoatrial node. The initial action impulse in a heart is usually formed in the sinoatrial node ...
typically manifesting with various degrees and patterns of
sinus bradycardia Sinus bradycardia Bradycardia is a condition typically defined wherein an individual has a resting heart rate of under 60 beats per minute (BPM) in adults, although some studies use a heart rate of less than 50 BPM. Bradycardia typically does ...
.


Sudden arrhythmic death syndrome

Sudden arrhythmic death syndrome Sudden arrhythmic death syndrome (SADS) is a sudden unexpected death of adolescents and adults, mainly during sleep Sleep is a naturally recurring state of mind and body, characterized by altered consciousness , an English Paracelsian ph ...
(SADS), is a term used as part of ''sudden unexpected death syndrome'' to describe sudden
death Death is the permanent, irreversible cessation of all biological functions that sustain a living Living or The Living may refer to: Common meanings *Life, a condition that distinguishes organisms from inorganic objects and dead organi ...

death
because of
cardiac arrest Cardiac arrest is a sudden loss of blood flow Hemodynamics American and British English spelling differences#ae and oe, or haemodynamics are the Fluid dynamics, dynamics of blood flow. The circulatory system is controlled by homeostasis, homeost ...
occasioned by an arrhythmia in the presence or absence of any structural heart disease on autopsy. The most common cause of sudden death in the US is
coronary artery disease Coronary artery disease (CAD), also called coronary heart disease (CHD), ischemic heart disease (IHD), or simply heart disease, involves the reduction of blood flow to the heart muscle Cardiac muscle (also called heart muscle or myocardium) i ...
specifically because of poor oxygenation of the heart muscle, that is
myocardial ischemia Coronary artery disease (CAD), also called coronary heart disease (CHD), Ischemia, ischemic heart disease (IHD), or simply heart disease, involves the reduction of blood flow to the myocardium, heart muscle due to build-up of plaque (atherosclero ...
or a
heart attack A myocardial infarction (MI), commonly known as a heart attack, occurs when blood flow Hemodynamics American and British English spelling differences#ae and oe, or haemodynamics are the Fluid dynamics, dynamics of blood flow. The circulatory sy ...

heart attack
Approximately 180,000 to 250,000 people die suddenly of this cause every year in the US. SADS may occur from other causes. There are many inherited conditions and heart diseases that can affect young people which can subsequently cause sudden death without advance symptoms. Causes of SADS in young people include viral myocarditis,
long QT syndrome Long QT syndrome (LQTS) is a condition in which repolarization of the heart after a Cardiac cycle, heartbeat is affected. It results in an increased risk of an cardiac arrhythmia, irregular heartbeat which can result in Syncope (medicine), faintin ...
,
Brugada syndrome Brugada syndrome (BrS) is a genetic disorder A genetic disorder is a health problem caused by one or more abnormalities in the genome In the fields of molecular biology and genetics, a genome is all genetic information of an orga ...
,
Catecholaminergic polymorphic ventricular tachycardia Catecholaminergic polymorphic ventricular tachycardia (CPVT) is an inherited genetic disorder that predisposes those affected to potentially life-threatening abnormal heart rhythms or Heart arrhythmia, arrhythmias. The arrhythmias seen in CPVT ...
,
hypertrophic cardiomyopathy Hypertrophic cardiomyopathy (HCM) is a condition in which the heart becomes hypertrophy, thickened without an obvious cause. The parts of the heart most commonly affected are the interventricular septum and the ventricles. This results in the hea ...
and
arrhythmogenic right ventricular dysplasia Arrhythmogenic cardiomyopathy (ACM), arrhythmogenic right ventricular dysplasia (ARVD), or arrhythmogenic right ventricular cardiomyopathy (ARVC), is an inherited heart disease. ACM is caused by Genetic disorder, genetic defects of the parts of ...
.


Fetal arrhythmia

Arrhythmias can also be found in the
fetus A fetus or foetus (; plural fetuses, feti, foetuses, or foeti) is the unborn offspring that develops from an animal embryo An embryo is the early stage of development of a multicellular organism A multicellular organism is an organism tha ...

fetus
. The normal heart rate of the fetus is between 110 and 160 beats per minute. Any rhythm beyond these limits is abnormal and classed as a fetal arrhythmia. These are mainly the result of premature atrial contractions, usually give no symptoms, and have little consequence. However, around one percent of these will be the result of significant structural damage to the heart.


Signs and symptoms

The term cardiac arrhythmia covers a very large number of very different conditions. The most common symptom of arrhythmia is an awareness of an abnormal heartbeat, called
palpitation Palpitations are perceived abnormalities of the heartbeat characterized by awareness of cardiac muscle contractions in the chest, which is further characterized by the hard, fast and/or irregular beatings of the heart. Symptoms include a rapid ...
s. These may be infrequent, frequent, or continuous. Some of these arrhythmias are harmless (though
distracting Distraction is the process of diverting the attention Attention is the behavioral and cognitive process Cognition () refers to "the mental action or process of acquiring knowledge and understanding through thought, experience, and the se ...
for patients) but some of them predispose to adverse outcomes. Some arrhythmias do not cause symptoms and are not associated with increased mortality. However, some asymptomatic arrhythmias ''are'' associated with adverse events. Examples include a higher risk of blood clotting within the heart and a higher risk of insufficient blood being transported to the heart because of a weak heartbeat. Other increased risks are of
embolization Embolization refers to the passage and lodging of an embolus within the circulatory system, bloodstream. It may be of natural origin (pathological), in which word sense, sense it is also called embolism, for example a pulmonary embolism; or it ...
and stroke, heart failure, and sudden cardiac death. If an arrhythmia results in a heartbeat that is too fast, too slow, or too weak to supply the body's needs, this manifests as lower blood pressure and may cause lightheadedness or dizziness, or syncope (
fainting Syncope, commonly known as fainting, is a loss of consciousness Consciousness, at its simplest, is sentience or awareness of internal and external existence. Despite millennia of analyses, definitions, explanations and debates by philos ...
). Some types of arrhythmia result in
cardiac arrest Cardiac arrest is a sudden loss of blood flow Hemodynamics American and British English spelling differences#ae and oe, or haemodynamics are the Fluid dynamics, dynamics of blood flow. The circulatory system is controlled by homeostasis, homeost ...
, or sudden death. Medical assessment of the abnormality using an
electrocardiogram Electrocardiography is the process of producing an electrocardiogram (ECG or EKG). It is a graph of voltage Voltage, electric potential difference, electromotive force emf, electric pressure or electric tension is the difference in elec ...

electrocardiogram
is one way to diagnose and assess the risk of any given arrhythmia.


Mechanism

Tachyarrhythmias are the result of spontaneous action potentials arise from cardiac muscle cells.


Diagnostic

Cardiac arrhythmia is often first detected by simple but nonspecific means:
auscultation :''For the ancient monasterial worker, see Auscultare'' Auscultation (based on the Latin verb ''auscultare'' "to listen") is listening to the internal sounds of the body, usually using a stethoscope The stethoscope is an acoustic medical ...

auscultation
of the heartbeat with a
stethoscope The stethoscope is an acoustic medical Medicine is the science and Praxis (process) , practice of caring for a patient, managing the diagnosis, prognosis, Preventive medicine, prevention, therapy, treatment, Palliative care , palliation o ...

stethoscope
, or feeling for peripheral
pulse In medicine Medicine is the science Science () is a systematic enterprise that builds and organizes knowledge Knowledge is a familiarity, awareness, or understanding of someone or something, such as facts ( descriptive knowledge) ...

pulse
s. These cannot usually diagnose specific arrhythmia but can give a general indication of the heart rate and whether it is regular or irregular. Not all the electrical impulses of the heart produce audible or palpable beats; in many cardiac arrhythmias, the premature or abnormal beats do not produce an effective pumping action and are experienced as "skipped" beats. The simplest ''specific'' diagnostic test for assessment of heart rhythm is the
electrocardiogram Electrocardiography is the process of producing an electrocardiogram (ECG or EKG). It is a graph of voltage Voltage, electric potential difference, electromotive force emf, electric pressure or electric tension is the difference in elec ...

electrocardiogram
(abbreviated ECG or EKG). A
Holter monitor In medicine Medicine is the Art (skill), art, science, and Praxis (process) , practice of caring for a patient and managing the diagnosis, prognosis, Preventive medicine, prevention, therapy, treatment or Palliative care , palliation of their ...

Holter monitor
is an EKG recorded over a 24-hour period, to detect arrhythmias that may happen briefly and unpredictably throughout the day. A more advanced study of the heart's electrical activity can be performed to assess the source of the aberrant heart beats. This can be accomplished in an
electrophysiology study A cardiac electrophysiology study (EP test or EP study) is a minimally invasive procedure using catheters introduced through a vein Veins are blood vessels that carry blood towards the heart. Most veins carry deoxygenated blood from the tissu ...
, an endovascular procedure that uses a catheter to "listen" to the electrical activity from within the heart, additionally if the source of the arrhythmias is found, often the abnormal cells can be ablated and the arrhythmia can be permanently corrected. ' (TAS) instead uses an electrode inserted through the
esophagus The esophagus (American English American English (AmE, AE, AmEng, USEng, en-US), sometimes called United States English or U.S. English, is the set of varieties of the English language native to the United States. Currently, American E ...

esophagus
to a part where the distance to the posterior wall of the
left atrium The atrium (Latin ātrium, “entry hall”) is the upper chamber through which blood enters the Ventricle (heart), ventricles of the heart. There are two atria in the human heart – the left atrium receives blood from the pulmonary (lung) circula ...
is only approximately 5–6 mm (remaining constant in people of different age and weight). Transesophageal atrial stimulation can differentiate between
atrial flutter Atrial flutter (AFL) is a common abnormal heart rhythm that starts in the atrial chambers of the heart The heart is a muscle, muscular Organ (anatomy), organ in most animals, which pumps blood through the blood vessels of the circulatory ...
,
AV nodal reentrant tachycardia AV-nodal reentrant tachycardia (AVNRT) is a type of abnormal fast heart rhythm. It is a type of supraventricular tachycardia (SVT), meaning that it originates from a location within the heart above the bundle of His. AV nodal reentrant tachycar ...

AV nodal reentrant tachycardia
and orthodromic
atrioventricular reentrant tachycardia Atrioventricular reentrant tachycardia (AVRT), or atrioventricular reciprocating tachycardia, is a type of abnormal fast heart rhythm and is classified as a type of supraventricular tachycardia (SVT). AVRT is most commonly associated with Wolf ...
. It can also evaluate the risk in people with
Wolff–Parkinson–White syndrome Wolff–Parkinson–White syndrome (WPWS) is a disorder due to a specific type of problem with the electrical system of the heart The heart is a muscle, muscular Organ (anatomy), organ in most animals, which pumps blood through the blood v ...
, as well as terminate
supraventricular tachycardia Supraventricular tachycardia (SVT) is an umbrella term for arising from the . This is in contrast to the other group of fast heart rhythms - , which start within the . There are four main types of SVT: , , (PSVT) and . The symptoms of SVT incl ...
caused by
re-entry (MER) aeroshell, artistic rendition Atmospheric entry is the movement of an object from outer space Outer space is the expanse that exists beyond Earth and between astronomical object, celestial bodies. Outer space is not completely empt ...
.


Differential diagnosis


Normal electrical activity

Each heartbeat originates as an electrical impulse from a small area of tissue in the right atrium of the heart called the sinus node or sinoatrial node (SA node). The impulse initially causes both atria to contract, then activates the atrioventricular node (AV node), which is normally the only electrical connection between the atria and the ventricles (main pumping chambers). The impulse then spreads through both ventricles via the
bundle of His Discovered in 1893 by Swiss Swiss may refer to: * the adjectival form of Switzerland *Swiss people Places *Swiss, Missouri *Swiss, North Carolina *Swiss, West Virginia *Swiss, Wisconsin Other uses *Swiss-system tournament, in various games and s ...
and the
Purkinje fibers The Purkinje fibers ( ; Purkinje tissue or subendocardial branches) are located in the inner Ventricle (heart), ventricular walls of the heart, just beneath the endocardium in a space called the subendocardium. The Purkinje fibers are specializ ...

Purkinje fibers
causing a synchronized contraction of the heart muscle and, thus, the pulse. In adults, the normal resting heart rate ranges from 60 to 90 beats per minute. The resting heart rate in children is much faster. In athletes, however, the resting heart rate can be as slow as 40 beats per minute, and be considered normal. The term
sinus arrhythmiaSinus arrhythmia is a commonly encountered variation of ''normal'' sinus rhythm A sinus rhythm is any cardiac rhythm in which depolarisation of the cardiac muscle begins at the sinus node. It is characterised by the presence of correctly oriented ...

sinus arrhythmia
refers to a normal phenomenon of alternating mild acceleration and slowing of the heart rate that occurs with breathing in and out respectively. It is usually quite pronounced in children and steadily decreases with age. This can also be present during
meditation Meditation is a practice where an individual uses a technique – such as mindfulness Mindfulness is the practice of purposely bringing one's attention in the present moment without evaluation,Mindfulness Training as a Clinical Interventio ...

meditation
breathing exercises that involve deep inhaling and breath holding patterns.


Bradycardias

A slow rhythm (less than 60 beats/min) is labelled
bradycardia Bradycardia is a condition typically defined wherein an individual has a resting heart rateHeart rate is the speed of the heartbeat measured by the number of contractions (beats) of the heart The heart is a muscle, muscular Organ (anatom ...
. This may be caused by a slowed signal from the sinus node (sinus bradycardia), by a pause in the normal activity of the sinus node (sinus arrest), or by blocking of the electrical impulse on its way from the atria to the ventricles (AV block or heart block). Heart block comes in varying degrees and severity. It may be caused by reversible poisoning of the AV node (with drugs that impair conduction) or by irreversible damage to the node. Bradycardias may also be present in the normally functioning heart of endurance athletes or other well-conditioned persons. Bradycardia may also occur in some types of seizures.


Tachycardias

In adults and children over 15, resting heart rate faster than 100 beats per minute is labeled
tachycardia Tachycardia, also called tachyarrhythmia, is a heart rate that exceeds the normal resting rate. In general, a resting heart rate over 100 beats per minute is accepted as tachycardia in adults. Heart rates above the resting rate may be normal (s ...
. Tachycardia may result in palpitation; however, tachycardia is not ''necessarily'' an arrhythmia. Increased heart rate is a normal response to physical exercise or emotional stress. This is mediated by the
sympathetic nervous system The sympathetic nervous system (SNS) is one of two divisions of the autonomic nervous system The autonomic nervous system (ANS), formerly the vegetative nervous system, is a division of the peripheral nervous system that supplies smooth muscle ...
on the
sinus node The sinoatrial node (also known as the sinuatrial node, SA node or sinus node) is a group of Cell (biology), cells located in the wall of the atrium (heart), right atrium of the heart. These Cell (biology), cells have the ability to spontaneously ...
and called sinus tachycardia. Other conditions that increase sympathetic nervous system activity in the heart include ingested or injected substances, such as
caffeine Caffeine is a central nervous system The central nervous system (CNS) is the part of the nervous system In biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structu ...

caffeine
or
amphetamines#REDIRECT Substituted amphetamine#REDIRECT Substituted amphetamine Substituted amphetamines are a class of compounds based upon the amphetamine structure; it includes all derivative In mathematics Mathematics (from Ancient Greek, Gre ...
, and an overactive thyroid gland (
hyperthyroidism Hyperthyroidism is the condition that occurs due to excessive production of thyroid hormone File:Thyroid_system.svg, upright=1.5, The thyroid The thyroid, or thyroid gland, is an endocrine gland in vertebrates. In humans it is in the neck ...
) or anemia. Tachycardia that is not sinus tachycardia usually results from the addition of abnormal impulses to the normal cardiac cycle. Abnormal impulses can begin by one of three mechanisms: automaticity, re-entry, or triggered activity. A specialized form of re-entry which is both common and problematic is termed fibrillation. Although the term "tachycardia" has been known for over 160 years, bases for the classification of arrhythmias are still being discussed.


Heart defects

Congenital heart defects are structural or electrical pathway problems in the heart that are present at birth. Anyone can be affected by this because overall health does not play a role in the problem. Problems with the electrical pathway of the heart can cause very fast or even deadly arrhythmias.
Wolff–Parkinson–White syndrome Wolff–Parkinson–White syndrome (WPWS) is a disorder due to a specific type of problem with the electrical system of the heart The heart is a muscle, muscular Organ (anatomy), organ in most animals, which pumps blood through the blood v ...
is due to an extra pathway in the heart that is made up of electrical muscle tissue. This tissue allows the electrical impulse, which stimulates the heartbeat, to happen very rapidly. Right ventricular outflow tract tachycardia is the most common type of ventricular tachycardia in otherwise healthy individuals. This defect is due to an electrical node in the right ventricle just before the pulmonary artery. When the node is stimulated, the patient will go into ventricular tachycardia, which does not allow the heart to fill with blood before beating again. Long QT syndrome is another complex problem in the heart and has been labeled as an independent factor in mortality. There are multiple methods of treatment for these including cardiac ablations, medication treatment, or lifestyle changes to have less stress and exercise.


Automaticity

Automaticity refers to a cardiac muscle cell firing off an impulse on its own. All of the cells in the heart have the ability to initiate an action potential; however, only some of these cells are designed to routinely trigger heartbeats. These cells are found in the conduction system of the heart and include the SA node, AV node, Bundle of His, and Purkinje fibers. The sinoatrial node is a single specialized location in the atrium that has a higher automaticity (a faster pacemaker) than the rest of the heart and, therefore, is usually responsible for setting the heart rate and initiating each heartbeat. Any part of the heart that initiates an impulse without waiting for the sinoatrial node is called an Cardiac ectopy, ectopic focus and is, by definition, a pathological phenomenon. This may cause a single premature beat now and then, or, if the ectopic focus fires more often than the sinoatrial node, it can produce a sustained abnormal rhythm. Rhythms produced by an ectopic focus in the atria, or by the
atrioventricular node The atrioventricular node or AV node is a part of the electrical conduction system of the heart The electrical conduction system of the heart transmits signals generated usually by the sinoatrial node to cause contraction of the heart muscle. Th ...
, are the least dangerous dysrhythmias; but they can still produce a decrease in the heart's pumping efficiency because the signal reaches the various parts of the heart muscle with different timing than usual and can be responsible for poorly coordinated contraction. Conditions that increase automaticity include
sympathetic nervous system The sympathetic nervous system (SNS) is one of two divisions of the autonomic nervous system The autonomic nervous system (ANS), formerly the vegetative nervous system, is a division of the peripheral nervous system that supplies smooth muscle ...
stimulation and Hypoxia (medical), hypoxia. The resulting heart rhythm depends on where the first signal begins: If it is the sinoatrial node, the rhythm remains normal but rapid; if it is an ectopic focus, many types of dysrhythmia may ensue.


Re-entry

Re-entrant arrhythmias occur when an electrical impulse recurrently travels in a tight circle within the heart, rather than moving from one end of the heart to the other and then stopping. Every cardiac cell can transmit Autowave, impulses of excitation in every direction but will do so only once within a short time. Normally, the action potential impulse will spread through the heart quickly enough that each cell will respond only once. However, if there is some essential heterogeneity of Refractory period (physiology), refractory period or if conduction is abnormally slow in some areas (for example in heart damage) so the myocardial cells are unable to activate the fast sodium channel, part of the impulse will arrive late and potentially be treated as a new impulse. Depending on the timing, this can produce a sustained abnormal circuit rhythm. As a sort of ''re-entry'', vortices of excitation in the myocardium (Autowave, autowave vortices) are considered to be the main mechanism of life-threatening cardiac arrhythmias. In particular, the autowave reverberator is common in the thin walls of the atria, sometimes resulting in
atrial flutter Atrial flutter (AFL) is a common abnormal heart rhythm that starts in the atrial chambers of the heart The heart is a muscle, muscular Organ (anatomy), organ in most animals, which pumps blood through the blood vessels of the circulatory ...
. Re-entry is also responsible for most
paroxysmal supraventricular tachycardia Paroxysmal supraventricular tachycardia (PSVT) is a type of supraventricular tachycardia, named for its intermittent episodes of abrupt onset and termination. Often people have no symptoms. Otherwise symptoms may include palpitations, feeling lig ...
, and dangerous
ventricular tachycardia Ventricular tachycardia (V-tach or VT) is a type of regular, fast heart rate that arises from improper electrical activity in the ventricles of the heart The heart is a muscle, muscular Organ (anatomy), organ in most animals, which pump ...
. These types of re-entry circuits are different from WPW syndromes, which utilize abnormal conduction pathways. Although omega-3 fatty acids from fish oil can be protective against arrhythmias, they can facilitate re-entrant arrhythmias.


Fibrillation

When an entire chamber of the heart is involved in multiple micro-reentry circuits and is, therefore, quivering with chaotic electrical impulses, it is said to be in fibrillation. Fibrillation can affect the atrium (
atrial fibrillation Atrial fibrillation (AF or A-fib) is an abnormal heart rhythm (arrhythmia) characterized by the rapid and irregular beating of the atrial chambers of the heart. It often begins as short periods of abnormal beating, which become longer or cont ...

atrial fibrillation
) or the ventricle (
ventricular fibrillation Ventricular fibrillation (V-fib or VF) is an abnormal heart rhythm in which the ventricles of the heart The heart is a cardiac muscle, muscular Organ (biology), organ in most animals, which pumps blood through the blood vessels of the ci ...

ventricular fibrillation
): ventricular fibrillation is imminently life-threatening. * Atrial fibrillation affects the upper chambers of the heart, known as the Atrium (heart), atria. Atrial fibrillation may be due to serious underlying medical conditions and should be evaluated by a physician. It is not typically a medical emergency. * Ventricular fibrillation occurs in the ventricles (lower chambers) of the heart; it is always a medical emergency. If left untreated,
ventricular fibrillation Ventricular fibrillation (V-fib or VF) is an abnormal heart rhythm in which the ventricles of the heart The heart is a cardiac muscle, muscular Organ (biology), organ in most animals, which pumps blood through the blood vessels of the ci ...

ventricular fibrillation
(VF, or V-fib) can lead to death within minutes. When a heart goes into V-fib, effective pumping of the blood stops. V-fib is considered a form of
cardiac arrest Cardiac arrest is a sudden loss of blood flow Hemodynamics American and British English spelling differences#ae and oe, or haemodynamics are the Fluid dynamics, dynamics of blood flow. The circulatory system is controlled by homeostasis, homeost ...
. An individual suffering from it will not survive unless cardiopulmonary resuscitation (CPR) and
defibrillation Defibrillation is a treatment for life-threatening cardiac dysrhythmia Arrhythmia, also known as cardiac arrhythmia or heart arrhythmia, is a group of conditions in which the heartbeat is irregular, too fast, or too slow. The heart rate tha ...
are provided immediately. CPR can prolong the survival of the brain in the lack of a normal pulse, but defibrillation is the only intervention that can restore a healthy heart rhythm. Defibrillation is performed by applying an electric shock to the heart, which resets the cells, permitting a normal beat to re-establish itself.


Triggered beats

Triggered beats occur when problems at the level of the ion channels in individual heart cells result in abnormal propagation of electrical activity and can lead to a sustained abnormal rhythm. They are relatively rare and can result from the action of anti-arrhythmic drugs, or after depolarizations.


Management

The method of cardiac rhythm management depends firstly on whether the affected person is stable or unstable. Treatments may include physical maneuvers, medications, electricity conversion, or electro- or cryo-cautery. In the United States, people admitted to the hospital with cardiac arrhythmia and conduction disorders with and without complications were admitted to the intensive care unit more than half the time in 2011.


Physical maneuvers

Several physical acts can increase parasympathetic nervous supply to the heart, resulting in blocking of electrical conduction through the AV node. This can slow down or stop several arrhythmias that originate above or at the AV node (see main article:
supraventricular tachycardia Supraventricular tachycardia (SVT) is an umbrella term for arising from the . This is in contrast to the other group of fast heart rhythms - , which start within the . There are four main types of SVT: , , (PSVT) and . The symptoms of SVT incl ...
s). Parasympathetic nervous supply to the heart is via the vagus nerve, and these maneuvers are collectively known as vagal maneuvers.


Antiarrhythmic drugs

There are many classes of antiarrhythmic medications, with different mechanisms of action and many different individual drugs within these classes. Although the goal of drug therapy is to prevent arrhythmia, nearly every antiarrhythmic drug has the potential to act as a pro-arrhythmic, and so must be carefully selected and used under medical supervision.


Other drugs

Several other drugs can be useful in cardiac arrhythmias. Several groups of drugs slow conduction through the heart, without actually preventing an arrhythmia. These drugs can be used to "rate control" a fast rhythm and make it physically tolerable for the patient. Some arrhythmias promote blood clotting within the heart and increase the risk of embolus and stroke. Anticoagulant medications such as warfarin and heparins, and anti-platelet drugs such as aspirin can reduce the risk of clotting.


Electricity

Arrhythmias may also be treated electrically, by applying a shock across the heart — either externally to the chest wall, or internally to the heart via implanted electrodes. Cardioversion is either achieved pharmacologically or via the application of a shock ''synchronized'' to the underlying heartbeat. It is used for the treatment of supraventricular tachycardias. In elective cardioversion, the recipient is usually sedated or lightly anesthesia, anesthetized for the procedure. Defibrillation differs in that the shock is not synchronized. It is needed for the chaotic rhythm of ventricular fibrillation and is also used for pulseless ventricular tachycardia. Often, more electricity is required for defibrillation than for cardioversion. In most defibrillation, the recipient has lost consciousness so there is no need for sedation. Defibrillation or cardioversion may be accomplished by an implantable cardioverter-defibrillator (ICD). Electrical treatment of arrhythmias also includes cardiac pacing. Temporary pacing may be necessary for reversible causes of very slow heartbeats, or
bradycardia Bradycardia is a condition typically defined wherein an individual has a resting heart rateHeart rate is the speed of the heartbeat measured by the number of contractions (beats) of the heart The heart is a muscle, muscular Organ (anatom ...
(for example, from drug overdose or myocardial infarction). A permanent artificial pacemaker, pacemaker may be placed in situations where the bradycardia is not expected to recover.


Electrical cautery

Some cardiologists further sub-specialize into electrophysiology. In specialized catheter, catheter laboratories, they use fine probes inserted through the blood vessels to map electrical activity from within the heart. This allows abnormal areas of conduction to be located very accurately and subsequently destroyed by heat, cold, electrical, or laser probes in a process called catheter ablation. This procedure may be completely curative for some forms of arrhythmia, but for others, the success rate remains disappointing.
AV nodal reentrant tachycardia AV-nodal reentrant tachycardia (AVNRT) is a type of abnormal fast heart rhythm. It is a type of supraventricular tachycardia (SVT), meaning that it originates from a location within the heart above the bundle of His. AV nodal reentrant tachycar ...

AV nodal reentrant tachycardia
is often curable by ablating one of the pathways in the Atrioventricular node, AV node (usually the slow pathway). Atrial fibrillation can also be treated, by performing a pulmonary vein isolation, but the results are less reliable.


Research

Arrhythmias due to medications have been reported since the 1920s with the use of quinine. In the 1960s and 1970s problems with antihistamines and antipsychotics were discovered. It was not until the 1980s that the underlying issue, QT interval#Abnormal intervals, QTc prolongation was determined.


See also

* Pre-excitation syndrome


References


External links

* {{DEFAULTSORT:Cardiac Arrhythmia Cardiac arrhythmia, Medical emergencies Wikipedia medicine articles ready to translate RTTEM