arrhythmia arrhythmia arrhythmias, also known as cardiac arrhythmias, heart arrhythmias, or dysrhythmias, are irregularities in the heartbeat, including when it is too fast or too slow. a resting heart rate that is too fast – above 100 beats per minute in adults – is called tachycardia, and a resting heart rate that is too slow – below 60 beats per minute – is called bradycardia. some types of arrhythmias have no symptoms. symptoms, when present, may include palpitations or feeling a pause between heartbeats. in more serious cases, there may be lightheadedness, passing out, shortness of breath or chest pain. while most cases of arrhythmia are not serious, some predispose a person to complications such as stroke or heart failure. others may result in sudden death. not to be confused with erythema or erythremia. arrhythmiaother namescardiac arrhythmia, cardiac dysrhythmia, irregular heartbeat, heart arrhythmiaventricular fibrillation (vf) showing disorganized electrical activity producing a spiked tracing on an electrocardiogram (ecg)specialtycardiologysymptomspalpitations, lightheadedness, passing out, shortness of breath, chest paincomplicationsstroke, heart failureusual onsetolder agetypesextra beats, supraventricular tachycardias, ventricular arrhythmias, bradyarrhythmiascausesproblems with the electrical conduction system of the heartdiagnostic methodelectrocardiogram, holter monitortreatmentmedications, medical procedures (pacemaker), surgeryfrequencymillions arrhythmias are often categorized into four groups: extra beats, supraventricular tachycardias, ventricular arrhythmias and bradyarrhythmias. extra beats include premature atrial contractions, premature ventricular contractions and premature junctional contractions. supraventricular tachycardias include atrial fibrillation, atrial flutter and paroxysmal supraventricular tachycardia. ventricular arrhythmias include ventricular fibrillation and ventricular tachycardia. bradyarrhythmias are due to sinus node dysfunction or atrioventricular conduction disturbances. arrhythmias are due to problems with the electrical conduction system of the heart. a number of tests can help with diagnosis, including an electrocardiogram (ecg) and holter monitor. many arrhythmias can be effectively treated. treatments may include medications, medical procedures such as inserting a pacemaker, and surgery. medications for a fast heart rate may include beta blockers, or antiarrhythmic agents such as 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 or are medically unstable may receive urgent treatment with a controlled electric shock in the form of cardioversion or defibrillation. 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. however, in most recent cases concerning the sars-cov‑2 pandemic, cardiac arrhythmias are commonly developed and associated with high morbidity and mortality among patients hospitalized with the covid-19 infection, due to the infection's ability to cause myocardial injury. sudden cardiac death is the cause of about half of deaths due to cardiovascular disease 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. arrhythmias may also occur in children; however, the normal range for the heart rate varies with age. classification broad classification of arrhythmias according to region of heart required to sustain the rhythm arrhythmia may be classified by rate (tachycardia, bradycardia), 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). arrhythmias are also classified by site of origin: atrial arrhythmia sinus bradycardia sinus arrhythmia sinus tachycardia premature atrial contractions (pacs) wandering atrial pacemaker atrial tachycardia multifocal atrial tachycardia supraventricular tachycardia (svt) atrial flutter atrial fibrillation (afib) av nodal reentrant tachycardia junctional arrhythmia av nodal reentrant tachycardia junctional rhythm junctional tachycardia premature junctional contraction ventricular arrhythmia premature ventricular contractions (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, or 1 normal beat to 2 pvcs, are termed "pvcs in trigeminy" groups of three premature ventricular beats are called triplets and are considered a brief run of non-sustained ventricular tachycardia (nsvt); if the grouping lasts for more than 30 seconds, it is considered sustained ventricular tachycardia (vt). accelerated idioventricular rhythm monomorphic ventricular tachycardia polymorphic ventricular tachycardia ventricular fibrillation torsades de pointes arrhythmogenic right ventricular dysplasia re-entry ventricular arrhythmia heart blocks these are also known as av blocks, because the vast majority of them arise from pathology at the atrioventricular node. 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 or wenckebach type 2 second degree heart block, also known as mobitz ii third-degree heart block, also known as complete heart block first, second, and third-degree blocks also can occur at the level of the sinoatrial junction. this is referred to as sinoatrial block typically manifesting with various degrees and patterns of sinus bradycardia. sudden arrhythmic death syndrome sudden arrhythmic death syndrome (sads), is a term used as part of sudden unexpected death syndrome to describe sudden death because of cardiac arrest 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 specifically because of poor oxygenation of the heart muscle, that is myocardial ischemia or a 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, brugada syndrome, catecholaminergic polymorphic ventricular tachycardia, hypertrophic cardiomyopathy and arrhythmogenic right ventricular dysplasia. fetal arrhythmia arrhythmias may also occur in the 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 palpitations. these may be infrequent, frequent, or continuous. some of these arrhythmias are harmless (though distracting 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 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, dizziness, syncope or brain death due to insufficient supply of blood to the brain. some types of arrhythmia result in cardiac arrest, or sudden death. medical assessment of the abnormality using an electrocardiogram is one way to diagnose and assess the risk of any given arrhythmia. mechanism cardiac arrhythmia are caused by one of two major mechanism. the first of arrhythmia is a result of enhanced or abnormal impulse formation originating at the pacemaker or the his-purkinje network. the second is due to re-entry conduction disturbances. diagnostic cardiac arrhythmia is often first detected by simple but nonspecific means: auscultation of the heartbeat with a stethoscope, or feeling for peripheral pulses. 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 (abbreviated ecg or ekg). a 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, 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. transesophageal atrial stimulation (tas) instead uses an electrode inserted through the esophagus to a part where the distance to the posterior wall of the left atrium is only approximately 5–6 mm (remaining constant in people of different age and weight). transesophageal atrial stimulation can differentiate between atrial flutter, av nodal reentrant tachycardia and orthodromic atrioventricular reentrant tachycardia. it can also evaluate the risk in people with wolff–parkinson–white syndrome, as well as terminate supraventricular tachycardia caused by re-entry. normal electrical activity main article: electrical conduction system of the heart 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 and the 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 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 breathing exercises that involve deep inhaling and breath holding patterns. bradycardias normal sinus rhythm, with solid black arrows pointing to normal p waves representative of normal sinus node function, followed by a pause in sinus node activity (resulting in a transient loss of heartbeats). note that the p wave that disrupts the pause (indicated by the dashed arrow) does not look like the previous (normal) p waves – this last p wave is arising from a different part of the atrium, representing an escape rhythm. a slow rhythm (less than 60 beats/min) is labelled bradycardia. 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 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 on the sinus node and called sinus tachycardia. other conditions that increase sympathetic nervous system activity in the heart include ingested or injected substances, such as caffeine or amphetamines, and an overactive thyroid gland (hyperthyroidism) or anemia. tachycardia that is not sinus tachycardia