Irregular heart rhythm (arrhythmias) in children

INTRODUCTION — The child with an irregular heart rhythm poses a common problem that has numerous etiologies ranging from normal benign variants to malignant arrhythmias. Determining the underlying cause of an irregular rhythm is important as it may be a life-threatening or serious condition. In most cases, the cause of an irregular heart rhythm is identified by an in-depth history, physical examination, and electrocardiogram (ECG), which can be completed by the primary clinician. In some cases, referral to a pediatric cardiologist is required for further diagnostic workup and, if necessary, treatment.

The etiology and evaluation of an irregular heart rhythm in children will be reviewed here. Tachycardia and bradycardia in children and the approach to the child with palpitations are discussed separately. (See "Approach to the child with tachycardia" and "Bradycardia in children" and "Approach to the child with palpitations".)

TYPES OF IRREGULAR HEART RHYTHM

Asymptomatic child — An irregular heart rhythm may be detected in an asymptomatic child during a routine physical examination or evaluation for some other issue. In this setting, the most common rhythm irregularities include:

●Sinus arrhythmia (waveform 1)

●Ventricular premature beats (VPBs) (waveform 2), bigeminy (waveform 3), or trigeminy (waveform 4)

●Premature atrial contractions (PACs; also referred to as premature atrial beats, premature supraventricular complex, or premature supraventricular beats) (waveform 5)

VPBs and PACs are most likely to be noted in asymptomatic children, though they can also occur in symptomatic children.

Sinus arrhythmia — Sinus arrhythmia is a normal physiologic variant characterized by an increased heart rate during inspiration and a decreased heart rate during expiration (waveform 1). Rhythm variability is caused, in part, by changes in parasympathetic input to the heart, which is mediated by the vagus nerve. Vagal tone, in turn, is modulated by the respiratory cycle. During expiration, enhanced vagal tone lowers the heart rate, and, during inspiration, vagal withdrawal increases the heart rate. Sinus arrhythmia is abolished during active exercise because vagal tone is decreased and the sympathetic tone is increased, resulting in a rapid heart rate throughout the respiratory cycle.

Sinus arrhythmia is a benign condition, even in individuals (eg, physically trained athletes) in whom this vagal/respiratory heart rate pattern is markedly pronounced. The diagnosis is made by electrocardiogram (ECG). (See 'Electrocardiogram' below.)

Ventricular premature beats — VPBs, also referred to as premature ventricular contractions, are premature depolarizations of the ventricles leading to early systolic contraction of the ventricles (waveform 2). VPBs are usually followed by a pause and occur without regularity, resulting in an irregular heart rhythm. VPBs also may, on occasion, occur in an irregular pattern (eg, every other beat [bigeminy] (waveform 3) or every third beat [trigeminy] (waveform 4)).

In an asymptomatic healthy child, VPBs that occur in isolation are generally benign and produce few or no symptoms. VPBs commonly occur in infancy, decline in incidence in early childhood, and become increasingly common again in adolescence and adulthood.

VPBs rarely cause true hemodynamic compromise, except in patients with frequent VPBs and severely depressed left ventricular function or when they are concurrent with bradycardia. In these patients, VPBs may be associated with an increased risk of a malignant arrhythmia, such as sustained ventricular tachycardia (VT). Frequent or polymorphic VPBs also may be a harbinger of a more malignant arrhythmia, such as catecholaminergic polymorphic VT and arrhythmogenic right ventricular dysplasia. (See "Causes of wide QRS complex tachycardia in children", section on 'Ventricular tachycardia'.)

The clinical significance and evaluation of VPBs are discussed separately. (See "Premature ventricular complexes: Clinical presentation and diagnostic evaluation".)

Premature atrial contractions — PACs are early depolarizations of atrial myocardium that lead to propagation of electrical impulses through the atrium and to the ventricle via the atrioventricular (AV) node. These electrical impulses result in early systolic ventricular contraction (waveform 5). Although PACs occur most commonly in isolation in infants and young children, they can occur throughout childhood. In asymptomatic children, PACs are benign and are unlikely to be associated with sustained tachyarrhythmias. (See "Supraventricular premature beats".)

Symptomatic child — Children with symptomatic arrhythmia may present with symptoms ranging from palpitations, to syncope, to aborted sudden cardiac death. In this setting, a sustained tachyarrhythmia is more likely to be the cause. Tachyarrhythmias in children can be classified as atrial, supraventricular, or ventricular.

Atrial arrhythmias — Atrial arrhythmias are most commonly seen in children with congenital heart disease (CHD) who have undergone cardiac surgery; they occur rarely in children without cardiac surgery or CHD. They include:

●Primary atrial tachycardia (ie, atrial ectopic tachycardia and focal atrial tachycardia) (waveform 6A-B) (see "Atrial tachyarrhythmias in children", section on 'Focal atrial tachycardia')

●Chaotic or multifocal atrial tachycardia (waveform 7) (see "Atrial tachyarrhythmias in children", section on 'Chaotic atrial tachycardia')

●Atrial flutter (waveform 8) (see "Atrial tachyarrhythmias in children", section on 'Atrial flutter and intraatrial reentry tachycardia')

●Atrial fibrillation (waveform 9) (see "Atrial tachyarrhythmias in children", section on 'Atrial fibrillation')

Atrial arrhythmias in children are discussed in greater detail in separate topic reviews. (See "Atrial tachyarrhythmias in children" and "Atrial arrhythmias (including AV block) in congenital heart disease".)

Supraventricular tachycardia — In reentrant supraventricular tachycardia (SVT) (waveform 10), an electrical impulse cycles repetitively through a circuit from the atria to the ventricles and back again, which results in rapid, regular ventricular contractions. Common clinical manifestations of reentrant SVT are palpitations, chest pain, fatigue, and lightheadedness. Infants may manifest with pallor, fussiness, irritability, poor feeding, and/or cyanosis. Most children tolerate short episodes of tachycardia well. However, prolonged episodes can precipitate heart failure.

Certain forms of SVT, such as AV reentrant tachycardia, may be associated with Wolff-Parkinson-White (WPW) syndrome (waveform 11). WPW syndrome is associated with an increased risk of sudden cardiac death. These patients are referred to a pediatric cardiologist for further diagnostic evaluation and management. SVT is discussed in greater detail separately. (See "Clinical features and diagnosis of supraventricular tachycardia (SVT) in children".)

Ventricular tachycardia — VT is relatively uncommon in children without underlying heart disease. Causes of VT in children include [1]:

●Inherited channelopathies (eg, long QT syndrome, Brugada syndrome (waveform 12), catecholaminergic polymorphic VT (waveform 13)). (See "Congenital long QT syndrome: Diagnosis" and "Brugada syndrome: Clinical presentation, diagnosis, and evaluation" and "Catecholaminergic polymorphic ventricular tachycardia".)

●Idiopathic VT (eg, right ventricular outflow tract tachycardia, which generally has a benign course). (See "Causes of wide QRS complex tachycardia in children", section on 'Right ventricular outflow tract tachycardia'.)

●Cardiomyopathy (eg, hypertrophic cardiomyopathy (waveform 14), arrhythmogenic right ventricular cardiomyopathy (waveform 15)). (See "Hypertrophic cardiomyopathy in children: Clinical manifestations and diagnosis" and "Arrhythmogenic right ventricular cardiomyopathy: Diagnostic evaluation and diagnosis".)

●Myocarditis. (See "Clinical manifestations and diagnosis of myocarditis in children".)

●Coronary heart disease – In contrast with adults, VT is rarely caused by coronary heart disease in children. However, structural coronary artery abnormalities (eg, left coronary arising from the right sinus) can present with VT. (See "Congenital and pediatric coronary artery abnormalities".)

●CHD – VT can occur as a late complication in children and adults with CHD and is associated with increased risk of mortality and serious morbidity. (See "Causes of wide QRS complex tachycardia in children", section on 'Congenital heart disease'.)

The causes, evaluation, and management of VT in children are discussed separately. (See "Causes of wide QRS complex tachycardia in children" and "Management and evaluation of wide QRS complex tachycardia in children".)

Sinus node dysfunction — In sinus node dysfunction, there is inappropriate sinus bradycardia or chronotropic incompetence (failure to appropriately elevate the heart rate in response to physiologic stress). This results in a slow heart rate and potential irregularity because of variations in the length of pauses in sinus activation and compensatory escape beats arising from other parts of the atrium, AV node, or ventricle.

Sinus node dysfunction is uncommon in patients with structurally normal hearts. In contrast, it is a common complication in patients with complex CHD and it can be associated with inflammatory diseases such as myocarditis, Kawasaki disease, or rheumatic heart disease. (See "Bradycardia in children", section on 'Sinus node dysfunction' and "Sinus node dysfunction: Clinical manifestations, diagnosis, and evaluation".)

Second-degree heart block — Children who have second-degree AV block, in whom the organized atrial impulse fails to be conducted to the ventricle in a 1:1 ratio, may have a regularly irregular or irregularly irregular slow heart rate.

●In patients with Mobitz type 1 block (also referred to as Wenckebach block), the PR interval progressively lengthens until a sinus beat is not conducted through the AV node in a consistent pattern of timing, resulting in a regularly irregular heart rate (waveform 16A). Affected patients are generally asymptomatic. (See "Bradycardia in children", section on 'Mobitz type 1 block' and "Second-degree atrioventricular block: Mobitz type I (Wenckebach block)".)

●In patients with Mobitz type 2 block, a P wave suddenly fails to conduct without any change in PR interval. This rhythm may be a regularly irregular or irregularly irregular heart rate (waveform 16B). This condition may progress to complete heart block and is sometimes associated with CHD. (See "Bradycardia in children", section on 'Mobitz type 2 block' and "Second-degree atrioventricular block: Mobitz type II".)

INITIAL EVALUATION — The initial evaluation begins with a focused history and physical examination, regardless of the setting in which the irregular heart rhythm is first noted. The cause of an irregular heart rhythm is often diagnosed by an electrocardiogram (ECG), which should be obtained if the history and physical examination have not completely confirmed that the irregularity is due to a benign etiology (algorithm 1).

History — The history should focus on determining whether there are other signs of heart disease and begins to differentiate among the various causes of an irregular heart rhythm. (See 'Types of irregular heart rhythm' above.)

Important elements of the history include [2]:

●Palpitations – The presence of palpitations (awareness of the beating of the heart) may represent an abnormality in heart rate or rhythm. Palpitations can be manifestations of a single beat (eg, ventricular premature beats [VPBs]), nonsustained tachycardias, or a sustained tachycardia. An accurate description may be useful in identifying the underlying arrhythmia. For example, palpitations due to sinus tachycardia usually have a gradual onset and termination and are associated with anxiety or activity. In contrast, patients with reentrant tachyarrhythmia typically have a sudden onset and ending of palpitations that correlate with the opening and closing of the circuit responsible for the arrhythmia. (See "Approach to the child with palpitations".)

●Syncope – Although the range of causes of syncope (defined as sudden, brief loss of consciousness associated with loss of postural tone, from which recovery is spontaneous) is broad (table 1), a history of syncope increases the risk for an underlying serious cardiac disease and the potential for a life-threatening cardiac arrhythmia. As a result, an ECG is recommended as part of the initial evaluation for any child with a syncopal episode (algorithm 2). (See "Causes of syncope in children and adolescents" and "Emergency evaluation of syncope in children and adolescents".)

●Chest pain – Arrhythmias are rare causes of chest pain in children. (See "Causes of nontraumatic chest pain in children and adolescents", section on 'Cardiac disease'.)

●Family history – Familial sudden unexpected death has been associated with Wolff-Parkinson-White (WPW) syndrome, catecholaminergic polymorphic ventricular tachycardia (VT), and arrhythmogenic right ventricular cardiomyopathy, which may be preceded by frequent spontaneous premature beats. (See "Approach to sudden cardiac arrest in the absence of apparent structural heart disease", section on 'Familial SCD'.)

If any of these historical elements is suggestive of an underlying cardiac disorder, an ECG should be obtained as an initial part of the evaluation.

Physical examination — The physical examination should include a complete description of the irregular heart rhythm because several conditions have characteristic findings:

●Respiratory cycle – Any consistent change of the heart rate in relation to the respiratory cycle should be noted. It is helpful in a cooperative child to have the patient take large inspiration and hold it prior to exhaling while the rhythm is being assessed. Patients with sinus arrhythmia have a characteristic increased heart rate during inspiration that decreases with expiration. (See 'Sinus arrhythmia' above.)

●Isolated ectopy – An irregular, early heartbeat followed by a pause in the midst of an otherwise regular rhythm is suggestive of VPBs or premature atrial contractions (PACs). (See 'Ventricular premature beats' above and 'Premature atrial contractions' above.)

●Bradycardia – In patients with a slow heart rate and an irregularly regular rhythm that arises from a pause in an otherwise regular rhythm is suggestive of sinus node dysfunction or second-degree atrioventricular (AV) block. Patients with irregularly irregular bradycardia may have Mobitz type 2 AV block. (See "Bradycardia in children", section on 'Sinus node dysfunction' and "Bradycardia in children", section on 'Second-degree atrioventricular block'.)

●Tachycardia – A very rapid rhythm, especially in a symptomatic child, may suggest a tachyarrhythmia (eg, reentrant supraventricular tachycardia [SVT], multifocal atrial tachycardia, or VT). (See 'Symptomatic child' above.)

Other elements of the cardiac examination include inspection, palpation (apical impulse, heave, thrill), and auscultation of the heart to assess the heart sounds and detect the presence of a gallop or murmur. Any abnormality of the cardiac examination increases the likelihood of a significant cardiac disorder, and an ECG should be obtained as an initial part of the evaluation. (See "Approach to the infant or child with a cardiac murmur", section on 'Cardiovascular examination' and "Approach to the infant or child with a cardiac murmur", section on 'Auscultation of heart sounds and murmurs'.)

Electrocardiogram — If the history and physical examination have not confirmed that the irregularity is due to a benign etiology, the next step in the evaluation is to obtain an ECG. A 12-lead ECG with a 30-second "rhythm strip" can sometimes provide a diagnosis.

●Sinus arrhythmia (waveform 1) – The heart rate varies with the respiratory cycle. During the ECG, the child can be asked to hold their breath during inspiration, which is correlated with an increase in heart rate. (See 'Sinus arrhythmia' above.)

●VPBs and PACs may be found during a rhythm strip, depending upon their frequency (waveform 2 and waveform 3 and waveform 4 and waveform 5). (See 'Ventricular premature beats' above and 'Premature atrial contractions' above.)

●Second-degree AV block is identified by ECG (waveform 16A and waveform 16B).

●Although tachyarrhythmias are usually paroxysmal and may not be seen on ECG, there may be findings suggestive of an underlying diagnosis:

•A short PR interval and a delta wave with a wide QRS confirms preexcitation, most often in the form of WPW syndrome (waveform 11). (See "Wolff-Parkinson-White syndrome: Anatomy, epidemiology, clinical manifestations, and diagnosis", section on 'Electrocardiographic findings'.)

•Characteristic ECG findings in patients with arrhythmogenic right ventricular cardiomyopathy include T wave inversion in the right precordial leads (V1, V2, and V3) (waveform 17) and epsilon waves (waveform 18). (See "Arrhythmogenic right ventricular cardiomyopathy: Diagnostic evaluation and diagnosis", section on '12-lead ECG'.)

•A prolonged QTc interval may suggest congenital long QT syndrome (waveform 19). (See "Congenital long QT syndrome: Diagnosis", section on '12-lead ECG'.)

•Patients with Brugada syndrome may demonstrate pseudo-right bundle branch block and ST segment elevation in leads V1 to V2 (waveform 12).

•Patients with hypertrophic cardiomyopathy may have prominent voltages with localized or diffuse repolarization abnormalities (waveform 14); however, these findings are nonspecific. (See "Hypertrophic cardiomyopathy in children: Clinical manifestations and diagnosis", section on 'Electrocardiography'.)

CARDIAC REFERRAL AND FURTHER EVALUATION

Referral — A referral to a pediatric cardiologist is made when the initial evaluation does not result in a diagnosis, the patient is symptomatic, and/or the electrocardiogram (ECG) demonstrates a clinically significant abnormality (eg, Wolff-Parkinson-White [WPW] pattern, prolonged QTc interval, second- or third-degree atrioventricular [AV] block, sinus pauses or other signs of sinus node dysfunction, ventricular premature beats [VPBs], or paroxysms of supraventricular or ventricular tachycardia [VT]). Additional ECG findings that may warrant referral to a cardiologist are described in greater detail separately. (See "Suspected heart disease in infants and children: Criteria for referral", section on 'Electrocardiography'.)

Consultation should be obtained more quickly in patients who have concerning symptoms (eg, syncope or heart failure symptoms) because of the increased risk of significant cardiac disease in such patients. Further testing is dependent upon the findings of the preceding evaluation, the setting in which the irregularity is first noted, and, if present, the frequency and duration of symptoms (algorithm 1).

Ambulatory electrocardiogram monitoring

●Holter monitor – A Holter monitor provides a continuous rhythm recording from adhesive electrodes for a minimum of 24 or 48 hours and up to 14 days. It is useful for assessing patients with frequent symptoms. Reports are available only after the monitoring period is complete and the data is analyzed in its entirety. Thus, this type of monitoring is appropriate for detecting events that do not need prompt reporting. (See "Ambulatory ECG monitoring", section on 'Continuous ambulatory ECG (Holter) monitor'.)

The Holter monitor is useful for determining the frequency and severity of abnormalities detected on ECG, such as VPBs, sinus node dysfunction, or second-degree AV block. Holter monitoring is generally not warranted for asymptomatic children with premature atrial contractions (PACs) or sinus arrhythmia already documented by ECG.

The Holter monitor uses a small, lightweight, battery-operated electromagnetic tape recorder or digital recorder, which records two or three channels of ECG data that provide the following information:

•Minimum, average, and maximum heart rate

•Longest pause in heart rate

•Number of VPBs and PACs

•Number of supraventricular tachyarrhythmia (SVT) runs, duration of the longest SVT run, and rate of the fastest SVT run

•Number of VT runs, duration of the longest VT run, and rate of the fastest VT run

In the symptomatic child, the patient/family should maintain a written diary of symptoms to correlate symptoms with the rhythm recording, which will help determine whether the symptoms are due to arrhythmias.

●Event monitors – In patients with intermittent or infrequent symptoms, event monitoring using a transtelephonic device is the preferred diagnostic test to determine whether symptoms are due to an underlying cardiac arrhythmia as they can be used for 30 to 60 days. In particular, transtelephonic monitoring is most useful in trying to determine whether SVT or VT is present. Transtelephonic monitor provides a rhythm recording, which can either be stored or transmitted by telephone to a health care provider. (See "Ambulatory ECG monitoring", section on 'Event (loop) monitor'.)

There are three basic types of transtelephonic monitors:

•Activation by the patient – The event monitor is activated by the patient at the onset of symptoms. The most common monitors are relatively small, handheld devices with electrodes that can record rhythm strips after an activation button is pressed. The strips can be transmitted via telephone lines to a computer system, where the data are analyzed and the rhythm strips can be printed.

•Continuous monitor – Loop monitors continuously monitor the rhythm. At activation, the preactivation rhythm of 5 to 10 seconds is also captured. These monitors can be set up to record automatically based on a preset heart rate criteria, so that they may be used to capture asymptomatic events or events that occur in young children who are not capable of activating the monitor. These monitors come in various forms including traditional, multilead-based systems and newer adhesive patches. Some of the adhesive systems have the benefit of being water-resistant but may be irritating on sensitive skin. (See "Ambulatory ECG monitoring", section on 'Event (loop) monitor'.)

•Mobile cardiac outpatient telemetry – These monitors are similar to the loop monitors but also allow for the pulling and analysis of data that does not meet preset criteria or that is not necessarily associated with patient activation. (See "Ambulatory ECG monitoring", section on 'Mobile cardiac outpatient telemetry (MCOT)'.)

One major impediment to these devices is that it may be difficult for a child to wear the leads for an extended period of time as the prolonged application of the leads can cause skin irritation.

●Patch monitors – Patch monitors are all-in-one small adhesive devices that do not require separate leads, wires, or battery packs. This makes them more convenient and less obtrusive than traditional Holter or event monitors. Patch monitors record only a single lead and are capable of continuously recording an ECG for up to 14 days. (See "Ambulatory ECG monitoring", section on 'Patch monitor'.)

●Monitoring with smart mobile devices – The burgeoning industry of smartphones and smartwatches has made home monitoring more available and less expensive than it was when traditional medical devices were all that were available. However, not all have been approved by the US Food and Drug Administration. The rhythm recordings from these devices are generally limited to a single lead (usually limb lead I or inverted I). In addition, they afford limited recording time, usually missing the onset or termination of an abnormal rhythm. While these limitations usually do not preclude identification of atrial fibrillation or common forms of SVT, they may be less reliable for identifying uncommon forms of arrhythmia. As technology advances and arrhythmia detection algorithms further improve, these smartwatch monitors may prove to be a valuable tool for identifying and managing patients with arrhythmia. Data on how to best integrate such devices into optimal arrhythmia management are limited. (See "Ambulatory ECG monitoring", section on 'Commercially available wearable heart rhythm monitors'.)

Additional details of ambulatory ECG monitoring are provided separately. (See "Ambulatory ECG monitoring".)

Exercise testing — The goal of exercise testing is to observe the effect of enhanced sympathetic drive upon the rhythm status in a child found to have an ECG or Holter monitor abnormality. It permits an assessment of the following:

●Sinus node function – Exercise testing evaluates the ability of the sinus node to respond to stress by comparing the heart rate with normative data. Patients with sinus node dysfunction have chronotropic incompetence (failure to appropriately elevate the heart rate in response to physiologic stress). (See "Bradycardia in children", section on 'Sinus node dysfunction'.)

●Intracardiac conduction – For patients with AV block, exercise may demonstrate changes in conduction pattern, escape rates, or the development of ventricular ectopy. Results from exercise testing may assist in determining whether pacemaker placement is indicated. AV conduction that improves with exercise in patients is a reassuring sign.

●WPW syndrome – The sudden disappearance of the delta wave during exercise suggests that these patients are at low risk for sudden death. These results indicate that the accessory pathway is not rapidly conducted from the atrium to the ventricle, so that the resulting heart rate during an atrial arrhythmia would not be excessively fast and irregular. In contrast, patients in whom the ECG findings of WPW syndrome persist during exercise may still be at risk for sudden death and require further assessment with electrophysiology study (EPS) (algorithm 1). (See 'Electrophysiology study' below and "Clinical features and diagnosis of supraventricular tachycardia (SVT) in children", section on 'Exercise testing' and "Wolff-Parkinson-White syndrome: Anatomy, epidemiology, clinical manifestations, and diagnosis", section on 'Risk stratification of asymptomatic patients with WPW pattern'.)

●VPBs and risk of VT – An exercise test is performed to help determine if patients with frequent isolated VPBs are at risk for developing more complex and potentially dangerous VT. If, during exercise, ventricular ectopy is suppressed, the VPBs are determined to be benign. However, if ventricular ectopy worsens and the patient develops nonsustained or sustained VT, further invasive evaluation and management (ie, EPS) are required. If VPBs remain and there is no complex ectopy, the result of the exercise testing is equivocal. An equivocal exercise test does not help in the clinical evaluation of the patient, so the decision to proceed with further testing should be based upon the patient's history, physical, and other testing results.

Echocardiogram — The echocardiogram is performed when there is an increased likelihood for structural heart disease, as follows:

●Suspicion of structural heart disease based upon clinical findings other than the irregular heart rate.

●Sinus node dysfunction because this condition is uncommon in patients who have a structurally normal heart.

●AV block from acquired inflammatory diseases (eg, Lyme disease or autoimmune diseases contracted later in life) because there may be valvar or pericardial injury. An echocardiogram should also be performed in patients with AV block associated with myocarditis because of the increased risk of ventricular dysfunction [3].

●Severe chronic bradycardia, either due to sinus node dysfunction or AV block, because of the increased risk of ventricular dilation associated with prolonged bradycardia.

●Frequent VPBs and VT may be associated with structural problems, such as intracardiac tumors, cardiomyopathies, or congenital heart disease (CHD).

●SVT may be associated with CHD, and patients with SVT are at increased risk for developing myocardial dysfunction and heart failure. An echocardiogram should be performed after the initial presentation to detect the presence of CHD and should be repeated if the patient has a prolonged episode of tachycardia associated with signs or symptoms of heart failure to determine whether a tachycardia-induced cardiomyopathy is present.

Electrophysiology study — Some patients with irregular heart rhythm may require an invasive EPS to provide a more definitive etiology and assessment of the severity of the arrhythmia, as well as an assessment of the risk of an associated malignant arrhythmia and sudden cardiac death (table 2).

EPS is a cardiac catheterization procedure during which the heart is stimulated and responses to these stimulations are assessed. This technique permits a detailed analysis of the mechanism underlying the cardiac arrhythmia and the precise location of the site of origin of the arrhythmia. The main risks of EPS are due to sedation, vascular complications, and bleeding.

Following the diagnostic EPS, mapping and ablation can be performed in patients with SVT or VT (table 3).

An overview of cardiac EPS and discussions on the use of EPS for specific arrhythmias are presented separately. (See "Invasive diagnostic cardiac electrophysiology studies".)

SOCIETY GUIDELINE LINKS — Links to society and government-sponsored guidelines from selected countries and regions around the world are provided separately. (See "Society guideline links: Arrhythmias in children".)

SUMMARY AND RECOMMENDATIONS

●Types of arrhythmias seen in children

•Normal benign variants seen in asymptomatic children – Common causes of irregular heart rhythm in an asymptomatic, otherwise healthy child include (see 'Asymptomatic child' above):

-Sinus arrhythmia (waveform 1)

-Ventricular premature beats (VPBs) (waveform 2), bigeminy (waveform 3), or trigeminy (waveform 4)

-Premature atrial contractions (PACs) (waveform 5)

•Tachyarrhythmias that are usually associated with symptoms – Children with sustained tachyarrhythmia may present with symptoms including pallor, palpitations, lightheadedness, or syncope. Causes in this setting include (see 'Symptomatic child' above):

-Supraventricular tachycardia (SVT) (waveform 10) is the most common tachyarrhythmia in childhood. (See "Clinical features and diagnosis of supraventricular tachycardia (SVT) in children".)

-Atrial tachyarrhythmias are relatively uncommon in children without underlying heart disease. They include primary atrial tachycardia (ie, atrial ectopic tachycardia and focal atrial tachycardia) (waveform 6A-B), chaotic or multifocal atrial tachycardia (waveform 7), atrial flutter (waveform 8), and atrial fibrillation (waveform 9). (See "Atrial tachyarrhythmias in children".)

-Ventricular tachycardia (VT) is relatively uncommon in children without underlying heart disease. (See "Causes of wide QRS complex tachycardia in children".)

•Irregular rhythm with low heart rate – Causes in this category include:

-Sinus node dysfunction (see "Bradycardia in children", section on 'Sinus node dysfunction' and "Sinus node dysfunction: Clinical manifestations, diagnosis, and evaluation")

-Second-degree heart block (waveform 16A-B) (see "Bradycardia in children", section on 'Second-degree atrioventricular block' and "Second-degree atrioventricular block: Mobitz type I (Wenckebach block)" and "Second-degree atrioventricular block: Mobitz type II")

●Initial evaluation – The initial evaluation, which can be completed by the primary care or urgent/emergency care provider, focuses on identifying the type of rhythm and determining the underlying cause (algorithm 1). This includes (see 'Initial evaluation' above):

•A focused history

•Physical examination

•Electrocardiogram (ECG)

In most cases, the cause of the abnormal heart rate is readily apparent from this evaluation.

●Referral – Referral to a pediatric cardiologist is warranted in any of the following scenarios (see 'Cardiac referral and further evaluation' above):

•Child has symptoms attributable to the abnormal heart rhythm

•ECG demonstrates a clinically significant abnormality

•Diagnosis is uncertain based upon the initial evaluation

Referral is generally not necessary for asymptomatic children with PACs or sinus arrhythmia documented on ECG.

●Further testing – Further testing depends upon the findings of the initial evaluation, the setting in which the irregularity is first noted, and the frequency and duration of symptoms if present (algorithm 1). Testing may include ambulatory ECG monitoring, exercise testing, echocardiogram, and/or electrophysiology study (EPS). (See 'Cardiac referral and further evaluation' above.)