Management of supraventricular tachycardia (SVT) in children

INTRODUCTION — Supraventricular tachycardia (SVT) can be defined as an abnormally rapid heart rhythm originating above the ventricles, often (but not always) with a narrow QRS complex; it conventionally excludes atrial flutter and atrial fibrillation [1].

The management of SVT in children will be reviewed here. Two major issues will be addressed: acute management to terminate the arrhythmia and chronic therapy to prevent recurrence. The clinical features of the different types of SVT are discussed separately. (See "Clinical features and diagnosis of supraventricular tachycardia (SVT) in children".)

Management of patients with preexcitation on electrocardiogram (Wolff-Parkinson-White pattern) (waveform 1) but without a symptomatic arrhythmia is discussed separately. (See "Wolff-Parkinson-White syndrome: Anatomy, epidemiology, clinical manifestations, and diagnosis", section on 'Risk stratification of asymptomatic patients with WPW pattern' and "Treatment of arrhythmias associated with the Wolff-Parkinson-White syndrome", section on 'Asymptomatic patients'.)

ACUTE MANAGEMENT — Acute management of the child who presents with SVT can be a challenge because the exact mechanism of the tachycardia often is unknown. The treatment strategy depends upon the patient's presentation and clinical status (hemodynamically stable or unstable). The approach consists of initiating therapy while continuing to assess the patient's condition (table 1). The following discussion is generally in agreement with the 2010 Pediatrics Advanced Life Support guidelines developed by the American Heart Association (AHA) and the International Liaison Committee on Resuscitation (ILCOR) (algorithm 1) [2]. The AHA/ILCOR guidelines were updated in 2015; however, the guidelines for tachyarrhythmias remained unchanged [3].

Hemodynamic assessment and monitoring — An infant or child who presents with a tachyarrhythmia should have an immediate hemodynamic assessment and an electrocardiogram (ECG) performed (table 1 and algorithm 1). A 15-lead ECG is generally preferred. This includes the 12 standard leads plus leads V3R and V4R (right-sided leads analogous to V3 and V4 on the left) and V7 (left posterior axillary line at V4 level). Continuous ECG monitoring during therapeutic maneuvers provides insight into the cause of tachycardia and helps in the planning of chronic therapy.

The most important initial clinical determination to make in children presenting with a tachyarrhythmia is whether there are signs of hemodynamic instability, including hypotension, heart failure, poor perfusion, shock, or decreased level of consciousness. Unstable patients require immediate intervention to terminate the rhythm.

Affected children can be asymptomatic except for fussiness or palpitations or may be unconscious with signs of cardiovascular collapse. The acute management depends on whether the patient is hemodynamically stable or not (table 1).

A broader discussion of the approach to assessing children with tachycardia is presented separately. (See "Approach to the child with tachycardia", section on 'Algorithmic approach'.)

Unstable patients — Unstable patients with hemodynamic compromise (eg. depressed consciousness, poor perfusion, hypotension, or other signs of shock or severe heart failure) require immediate termination of the tachyarrhythmia (table 1). Cardioversion is the definitive intervention.

Interventions while preparing to cardiovert — While preparing to cardiovert, supplemental oxygen and other respiratory support should be provided as needed. Adenosine may be given while preparing to cardiovert if the drug is readily available and the child has intravenous (IV) access. Similarly, vagal maneuvers can be attempted while preparing for cardioversion or drug therapy, but cardioversion should not be delayed to administer vagal maneuvers. (See 'First-line therapy (adenosine)' below and 'Vagal maneuvers' below.)

In general, the child should be given adequate analgesia and sedation before cardioversion [4,5]. Rarely, a child is too critically ill to delay the procedure for administration of sedation. The approach to procedural sedation in children is discussed separately. (See "Procedural sedation in children: Approach".)

Cardioversion — Cardioversion is the definitive intervention to terminate SVT in children who are hemodynamically unstable. Direct current cardioversion is performed using an energy dose of 0.5 to 1 J/kg, which can be increased to 2 J/kg if the lower dose is ineffective [2,6]. A narrow complex tachycardia should be converted in synchronous mode, in which a shock is not delivered during the vulnerable repolarization period; this will avoid possible precipitation of ventricular fibrillation. Additional details of the procedure, including electrode size and choice of handheld paddles versus self-adhesive pads, are provided separately. (See "Technique of defibrillation and cardioversion in children (including automated external defibrillation)", section on 'Procedure'.)

Synchronous direct-current cardioversion is highly effective for all types of SVT and restores sinus rhythm in >95 percent of cases when properly administered [7-10]. (See "Cardioversion for specific arrhythmias", section on 'Efficacy'.)

Stable patients — In patients who are hemodynamically stable, additional time can be given to evaluate the rhythm and to attempt vagal maneuvers to terminate the tachyarrhythmia. If the rhythm does not terminate with vagal maneuvers, adenosine is given.

Diagnostic evaluation — The following findings support the presence of an SVT [2]:

●Abrupt onset of tachycardia

●Heart rate >220 beats/min in infants and >180 beats/min in children

●P waves absent or abnormal

●Heart rate does not vary with activity

The vast majority of SVT episodes in children with structurally normal hearts involve classic atrioventricular (AV) reentry. The potential mechanisms include:

●AV reentrant tachycardia (AVRT) due to either a manifest or concealed accessory pathway (see "Atrioventricular reentrant tachycardia (AVRT) associated with an accessory pathway")

●AV nodal reentrant tachycardia (AVNRT) (see "Atrioventricular nodal reentrant tachycardia")

The discussion in this topic focuses primarily on these common mechanisms. Rare pediatric cases may involve other mechanisms such as atrial ectopic tachycardia or atrial flutter. The diagnostic evaluation of AVRT, AVNRT, and other types of SVT is discussed in greater detail separately. (See "Clinical features and diagnosis of supraventricular tachycardia (SVT) in children", section on 'Diagnosis' and "Atrial tachyarrhythmias in children".)

Vagal maneuvers — In children who have mild or no symptoms, vagal maneuvers should be attempted while supplies and personnel are assembled to proceed to medical therapy, if needed. These maneuvers should be performed while the ECG is continuously monitored. The ECG pattern seen during termination of the tachycardia can help determine its mechanism.

In infants, the vagal maneuver most commonly used is application of a bag filled with ice and cold water over the face for 15 to 30 seconds. This elicits the diving reflex, frequently interrupting the arrhythmia [11]. Another method that may be successful in infants is rectal stimulation using a thermometer.

In older children, vagal maneuvers include bearing down (Valsalva maneuver), blowing into an occluded straw, or assuming a head-down position for 15 to 20 seconds.

Carotid massage and orbital pressure should not be performed in children.

Vagal maneuvers are successful in 60 to 90 percent of cases [12-15]. (See "Vagal maneuvers".)

Supraventricular tachycardia refractory to vagal maneuvers — If the vagal maneuver does not convert SVT that is hemodynamically stable to normal rhythm, an IV catheter should be placed for the administration of antiarrhythmic drugs. Adenosine is the preferred drug for acute management of SVT because it successfully converts approximately 75 to 95 percent of cases and, while side effects are common, they are generally mild and short lived.

First-line therapy (adenosine) — Adenosine is considered the drug of choice for acute medical conversion of SVT in children (table 1 and waveform 2 and algorithm 1) [2,16-19].

●Dosing and administration – We suggest the following procedure for adenosine administration:

•The usual initial dose is 0.1 mg/kg IV (maximum dose 6 mg).

•Adenosine should administered by rapid IV injection at a site as close to the central circulation as possible, followed immediately by a 5 mL normal saline flush. The use of two syringes (one with adenosine and the other with normal saline flush) connected to a three-way stopcock is a useful way of ensuring rapid and effective drug delivery.

•The patient should be supine and should have continuous ECG and blood pressure monitoring.

•If no response is seen within two minutes, the dose should be doubled (ie, 0.2 mg/kg IV, maximum dose 12 mg).

An alternative regimen consists of an initial bolus of 0.05 mg/kg; if no response is seen within two minutes, the dose is increased by 0.05 mg/kg increments every two minutes until termination of the arrhythmia or a maximum dose of 0.25 to 0.35 mg/kg or 12 mg is given.

The IV injection procedure described above facilitates rapid delivery to the heart, which is necessary because the drug is quickly metabolized to an inactive form by an enzyme on the red cell surface. Higher doses are typically necessary when given peripherally compared with centrally [2]. In one study, the average effective dose was approximately 0.13 mg/kg (range 0.05 to 0.25 mg/kg) [20]. The wide range likely reflects differences in how the drug was given.

●Contraindications and cautions – Cautions with adenosine use include the following:

•Adenosine is contraindicated in patients with preexisting second- or third-degree heart block or sinus node disease [21].

•In patients with Wolff-Parkinson-White (WPW) syndrome, adenosine can precipitate atrial fibrillation that can degenerate into ventricular fibrillation. This is an extremely rare event and does not imply that adenosine should be avoided in patients with WPW. To the contrary, adenosine is considered the first-line treatment for SVT in patients with WPW. However, clinicians should be aware of this potential and emergency resuscitation equipment should be available [22]. (See "Treatment of arrhythmias associated with the Wolff-Parkinson-White syndrome", section on 'Orthodromic AVRT'.)

•Patients with asthma may experience acute bronchospasm with adenosine administration [23,24], though this is uncommon in children without an asthma history [25]. Underlying asthma is not a contraindication to using adenosine, but clinicians should be aware of the potential for bronchospasm. The mechanism for adenosine-induced bronchospasm is uncertain but may be related to stimulation or enhancement of mast cell-derived mediators [23].

•In patients who have undergone heart transplantation, adenosine administration can cause prolonged AV block. This is a consequence of parasympathetic denervation, which increases the sensitivity of the sinus and AV node receptors [26]. Thus, when adenosine is used to treat SVT in patients who have undergone heart transplant, we suggest starting with a low dose (0.025 mg/kg, maximum dose 1.5 mg) with gradual dose escalation. This dosing regimen appears to be safe in heart transplant patients [27].

●Side effects – Side effects, including flushing, nausea, vomiting, vague feeling of discomfort, chest pain, and dyspnea, are common with adenosine but usually resolve rapidly [18,20,25,28,29]. Serious side effects, such as arrhythmias, are rare [25]. Adenosine can precipitate atrial fibrillation, although this usually terminates spontaneously [20,22]. IV adenosine should be administered in a setting where appropriate monitoring and resuscitation equipment (eg, oxygen, defibrillator) are readily available and where adverse events can be managed.

In a multicenter report of 98 episodes of presumptive SVT episodes treated with IV adenosine in the emergency department setting, adverse effects were observed in 22 percent [25]. Patients who received multiple doses and/or doses >0.2 mg/kg were more likely to experience adverse effects compared with those who received a single-dose and total dose ≤0.2 mg/kg. The most common side effects were nausea/vomiting (10 percent), chest discomfort (6 percent), flushing (4 percent), headache (3 percent), dyspnea (2 percent), and bradycardia (2 percent). No patient experienced a hemodynamically significant arrhythmia.

●Efficacy and mechanism of action – The efficacy of adenosine for acute treatment of SVT in children is supported by retrospective case series [8,18,20,25,30-32]. In the available reports, adenosine terminated 80 to 95 percent of episodes of AVRT, which accounts for almost three-quarters of episodes of SVT [31,32] and approximately 75 percent of episodes due to other causes of SVT [18,20,25]. Early recurrence of the SVT after termination occurs in 25 to 30 percent of cases [18,20].

Though clinical trials are lacking in children, trials in adults have demonstrated that adenosine's efficacy in terminating SVT is comparable with that of verapamil [33]. In children, adenosine is preferred over verapamil because of its very short duration of action and because there are a number of settings in which verapamil should not be used (eg, infants <12 months old), as discussed below. (See 'Supraventricular tachycardia refractory to adenosine' below.)

Adenosine acts by interacting with A1 receptors on the surface of cardiac cells; the resulting effects include slowing of the sinus rate and an increase in the AV nodal conduction delay [30]. This interrupts the reentrant circuit of tachycardias that require the AV node for reentry.

Vagal stimulation caused by adenosine is brief and self-limited. The onset of effect is almost immediate: The half-life is less than 5 to 10 seconds. The effects of adenosine are diminished by methylxanthines such as caffeine or theophylline.

Supraventricular tachycardia refractory to adenosine — If adenosine fails to convert SVT to sinus rhythm, there are three potential explanations:

●The medication may not have been administered rapidly enough or close enough to the central circulation. In this case, the ECG recording during adenosine administration typically shows no interruption in the rhythm. Optimizing the administration technique in subsequent doses, as described above, may result in successful termination of the rhythm. (See 'First-line therapy (adenosine)' above.)

●The tachyarrhythmia may be due to an alternate mechanism such as atrial ectopic tachycardia (AET) or atrial flutter. The ECG recording during adenosine administration can be of diagnostic utility in these cases (waveform 3). Management of AET and atrial flutter are beyond the scope of this topic review. Consultation with a pediatric cardiologist is advised. (See "Atrial tachyarrhythmias in children", section on 'Management'.)

●The SVT may be truly refractory to adenosine.

For SVT that is refractory to adenosine, choices for IV antiarrhythmic therapy include procainamide and amiodarone. Verapamil is another option in older children; however, its use is limited. These drugs have potential for serious adverse effects and therefore consultation with a pediatric cardiologist is advised. Beta blocker therapy is an alternative to IV antiarrhythmic therapy if the SVT appears to be well tolerated (ie, hemodynamically stable and no symptoms) and the patient is in a closely monitored setting. Digoxin is not usually used, because of the delay in achieving therapeutic levels and the narrow therapeutic margin with the risk of serious toxicity [6]. In addition, digoxin should not be given if WPW syndrome is suspected, since it may potentiate accessory pathway conduction.

●Procainamide – SVT that is refractory to adenosine may respond to IV procainamide. In neonates, a loading dose of 7 to 10 mg/kg is given IV over 30 to 45 minutes. In infants and older children, the loading dose is 10 to 15 mg/kg. This is followed by a continuous IV infusion starting at 20 mcg/kg per minute. Plasma levels should be measured four hours after completion of the loading dose, during the maintenance infusion.

Procainamide has potential for serious adverse effects, and, therefore, consultation with a pediatric cardiologist is advised. Negative inotropic effects may occur following the administration of procainamide. In addition, procainamide can prolong the QT interval and therefore should not be given with other drugs that prolong QT. (See "Acquired long QT syndrome: Definitions, pathophysiology, and causes".)

Procainamide is a class IA antiarrhythmic drug that acts primarily by inhibiting phase 0 (sodium-dependent) depolarization and slows atrial conduction. Unlike adenosine and verapamil, procainamide acts by slowing conduction within the myocardium itself, rather than by blocking reentry at the AV node. As a result, procainamide may be used safely in patients with WPW syndrome without the risk of provoking accessory pathway conduction.

In a retrospective study of 40 episodes of acute refractory SVT managed at a single institution, the success rate with procainamide appeared to be superior to that of amiodarone (71 versus 34 percent) [34].

Procainamide's use in pediatric resuscitation is discussed in greater detail separately. (See "Primary drugs in pediatric resuscitation", section on 'Procainamide'.)

●Amiodarone – Amiodarone is generally reserved for SVT that is refractory to other agents (adenosine, procainamide) [35]. Like procainamide, it can be used safely in patients with WPW syndrome so long as the SVT has a narrow and regular QRS complex. Amiodarone is considered contraindicated in preexcited atrial fibrillation, which has an irregular and wide QRS complex. (See "Wolff-Parkinson-White syndrome: Anatomy, epidemiology, clinical manifestations, and diagnosis", section on 'Atrial fibrillation'.)

Different dosing regimens have been described. We typically use a bolus infusion of 5 mg/kg IV over 20 to 60 minutes. If there is no response, the bolus dose is repeated up to a total of 15 mg/kg. If the patient responds, this is followed by a continuous IV infusion of 10 to 15 mg/kg per day.

Adverse events are common with IV amiodarone use in children and may be severe. Consultation with a pediatric cardiologist is advised. Adverse effects such as nausea and vomiting are common. Severe adverse effects can also occur, including hypotension, bradycardia, AV block, and cardiovascular collapse [35-38]. ECG and blood pressure monitoring should be performed during administration of IV amiodarone. Both amiodarone and procainamide can prolong the QT interval, and they should not be given together. (See "Acquired long QT syndrome: Definitions, pathophysiology, and causes".)

Amiodarone is a class III antiarrhythmic agent. The IV preparation prolongs the refractory period of the AV node and, to a lesser degree, the duration of the action potential and the refractory period of both atrial and ventricular myocardium [39].

The efficacy of amiodarone in the acute treatment of SVT in children is supported by several small case series and one prospective dose-finding clinical trial [35,37,40,41]. The success rates in these reports range from 47 to 87 percent. Factors that likely influenced the success rates in these studies include the dose of amiodarone used, age of the child (success was less likely in infants <12 months [41]), and type of tachyarrhythmia studied (response rates were generally higher in studies limited to SVT compared with studies that included other tachyarrhythmias). In the one prospective clinical trial, which involved 61 children (mean age 4.1 years) with incessant tachyarrhythmias (SVT accounted for approximately one-half), the response time was fastest and the response rate was greatest in patients who received high-dose amiodarone (ie, 10 mg/kg loading dose followed by 10 mg/kg per day continuous infusion) [37]. However, dose-related adverse events were common, occurring in 87 percent of patients, including two deaths that were possibly drug-related. For this reason, IV amiodarone should be used with caution in patients who are otherwise hemodynamically stable and it should only be administered in an acute care setting where hypotension and bradycardia can be promptly treated.

Amiodarone's use in pediatric resuscitation is discussed in greater detail separately. (See "Primary drugs in pediatric resuscitation", section on 'Amiodarone'.)

●Verapamil – Verapamil is an effective acute therapy to slow AV nodal conduction and terminate SVT in children older than one year. Verapamil is administered as an IV infusion in a dose of 0.1 to 0.3 mg/kg with a maximum dose of 10 mg.

Adenosine is preferred over verapamil for first-line therapy because of its very short duration of action. In addition, there are a number of settings in which verapamil should not be used:

•In infants <1 year old because it may cause apnea, hypotension, bradycardia, and cardiovascular collapse [42,43]. The mechanism of this complication may be a poorly developed sarcoplasmic reticulum in infants, so that myocardial contractility depends solely on calcium channels.

•In children with heart failure [6,42].

•In children with known or suspected WPW syndrome since it may potentiate conduction down an antegrade conducting pathway and provoke ventricular fibrillation [6].

•In children with a wide QRS complex tachycardia since it can provoke severe hemodynamic deterioration in those who have ventricular tachycardia rather than an SVT [44].

●Beta blockers – In patients with SVT that does not initially respond to adenosine and in whom the rhythm appears to be well tolerated (ie, hemodynamically stable and no symptoms), beta blocker therapy with IV esmolol (loading dose 100 to 500 mcg/kg over one minute, followed by an infusion of 25 to 100 mcg/kg/min) or oral propranolol (0.5 mg/kg as a single dose) may be used as alternate or ancillary pharmacologic therapy, provided that the patient continues to be closely monitored until sinus rhythm is restored. If the patient does not self-convert after an hour, repeat dosing with adenosine can be attempted. (See 'First-line therapy (adenosine)' above.)

●Digoxin – Digoxin is not usually used for acute SVT treatment, because of the delay in achieving therapeutic levels and the narrow therapeutic margin with the risk of serious toxicity [6]. In addition, digoxin should not be given if WPW syndrome is suspected, since it may potentiate accessory pathway conduction.

Transesophageal pacing — Transesophageal pacing may be a useful adjunct to therapy for SVT in a child; however, it requires the expertise of cardiologists who are very familiar with the technique [6]. The technique involves electrical atrial stimulation until the tachyarrhythmia resolves or until other therapies can be initiated [6,45]. It can be used to determine the mechanism of and to terminate the tachycardia. This is particularly valuable in the management of the infant who is refractory to pharmacologic therapy or with incessant recurrence of SVT, in that it can be repeatedly used without additional exposure to the potential adverse effects of pharmacologic cardioversions. In one report involving 63 patients (mostly adults), transesophageal pacing successfully terminated SVT in all but one [45]. However, transesophageal pacing requires specialized personnel and equipment. Sedation of the child may be necessary because the procedure can be uncomfortable.

EVALUATION AFTER THE ACUTE EPISODE — After the acute episode is terminated, an electrocardiogram (ECG) and echocardiogram should be performed. The ECG is obtained to look for evidence of Wolff-Parkinson-White (WPW) syndrome (the presence of a wide QRS complex with a "delta wave") (waveform 1). (See "Clinical features and diagnosis of supraventricular tachycardia (SVT) in children", section on 'Electrocardiogram'.)

An echocardiogram should be obtained to assess for structural heart disease since SVT can be associated with congenital heart disease (21 percent of patients referred for catheter ablation in one series) [32].

The evaluation of children with SVT is discussed in greater detail separately. (See "Clinical features and diagnosis of supraventricular tachycardia (SVT) in children", section on 'Diagnosis'.)

REFERRAL — Infants and children with preexcitation on electrocardiogram (ECG) or documented SVT should be referred to a pediatric cardiologist/electrophysiologist to guide the diagnostic evaluation and to discuss risk assessment and management options.

Urgent referral is warranted for children who present with SVT associated with any of the following:

●Syncope

●Heart failure

●Incessant tachycardia

●Other concerning cardiac finding (eg, depressed ventricular function on echocardiogram)

In most other circumstances, referral can be done electively on an outpatient basis.

TREATMENT TO PREVENT SUPRAVENTRICULAR TACHYCARDIA RECURRENCES — Options for chronic management of SVT include expectant management, pharmacologic therapy, and catheter ablation. Each approach has advantages and disadvantages. The specific approach should be tailored to the individual patient based upon age and severity of symptoms (algorithm 2).

Infants <1 year — For infants with SVT, we suggest prophylactic pharmacologic therapy with propranolol. Expectant management is an alternative option after the first episode if the infant is asymptomatic and has normal ventricular function. We generally prefer initial pharmacologic therapy over expectant management because infants cannot complain of palpitations, and therefore detection of recurrences of SVT may be delayed even if parents are instructed to monitor the heart rate. Thus, infants are more likely to develop signs and symptoms of heart failure compared with older children [6]. Catheter ablation is generally not an option in infants, because the risk of complications is unacceptably high.

●Prophylactic medication (preferred) – We suggest treatment with a beta blocker as the first-line agent for chronic management of SVT in infants. This is based largely on the side effect profile of beta blockers, which is generally more favorable than that of other antiarrhythmic drugs. Observational data, clinical experience, and a single randomized clinical trial support this practice [46-50]. The preferred beta blocker for infants <12 months is propranolol (2 to 4 mg/kg per day orally divided into four doses). (See 'First-line prophylactic therapy (beta blocker)' below.)

The duration of therapy in infants <1 year is variable. In a multicenter cohort study of 278 infants treated for either six months or one year, no difference in SVT recurrence rate was seen over one year (12 percent in both groups) [51]. Independent risk factors for recurrence included combination antiarrhythmic regimens, WPW, and age >1 month at presentation.

●Expectant management – Expectant management is an option for infants who are asymptomatic without hemodynamic compromise or ventricular dysfunction. However, this approach is chosen less often for infants because recurrences of SVT are more challenging to detect in this age group compared with older children. If expectant management is selected, the infant is monitored for 24 hours and teaching is provided to the parents prior to hospital discharge, as described below. (See 'First episode, minimal symptoms' below.)

Children ≥1 year — For children ≥1 year, the approach to chronic management depends on the severity of symptoms and the size of the child (algorithm 2).

First episode, minimal symptoms — We typically manage patients expectantly following the first episode of SVT if the child has no or only minimal symptoms and there is no hemodynamic instability or ventricular dysfunction. For such patients, we monitor the child for at least 24 hours, teach the parents how to check the heart rate, and instruct them in methods for terminating SVT episodes using vagal maneuvers (eg, applying an ice bag to the face, performing the Valsalva maneuver, assuming a head-down position, and other techniques). (See 'Vagal maneuvers' above.)

The rationale for this approach is that some patients (particularly those who are <5 years old at initial presentation) may outgrow the SVT and may not require chronic therapy, which may be associated with side effects. (See "Clinical features and diagnosis of supraventricular tachycardia (SVT) in children", section on 'Natural history'.)

As discussed above, this approach is used less often in infants because recurrences of SVT are more challenging to detect in this age group. (See 'Infants <1 year' above.)

Recurrent and/or symptomatic supraventricular tachycardia episodes — For children who have recurrent and/or symptomatic SVT episodes, we suggest intervention to prevent further recurrences. The choice of intervention depends on the size of the child; radiofrequency ablation (RFA) is generally reserved for patients ≥15 kg because of the increased risk of complications with RFA in small children.

●Children <15 kg – For infants and young children <15 kg who have frequent episodes of SVT or who become symptomatic during infrequent episodes, we suggest prophylactic medical therapy. The objective of medical treatment is to prevent episodes of SVT or to lessen symptoms during a recurrence. In our practice, we use long-term daily medication with a beta blocker for such children. We typically use a long-acting beta blocker such as atenolol or nadolol in children >1 year old. Both are given at a dose of 1 to 2 mg/kg per day orally. (See 'First-line prophylactic therapy (beta blocker)' below.)

Another form of treatment is "pulsed" or "cocktail" therapy, in which the patient takes an antiarrhythmic drug only during an episode of SVT in order to terminate the arrhythmia [6,52,53]; however, we do not generally use this approach.

●Children ≥15 kg – In children who are ≥15 kg, we suggest RFA rather than chronic antiarrhythmic medication therapy. RFA is an effective treatment for most types of SVT, and it avoids the adverse effects of chronic pharmacologic therapy. (See 'Catheter ablation' below.)

Failure of initial medical therapy — For patients managed with pharmacologic therapy who do not achieve adequate control of SVT with first-line therapy, options for second-line therapy include flecainide, sotalol, and amiodarone [54-60]. (See 'Second-line agents' below.)

RFA is another option for children who fail initial medical therapy, and this is the preferred approach for children ≥15 kg. RFA is generally not performed in children <15 kg unless the SVT is refractory to medical therapy or there are intolerable adverse effects from pharmacologic therapy. (See 'Catheter ablation' below.)

In one study, factors that predicted poor response to initial therapy included young age at presentation (<1 month), ventricular dysfunction at presentation, and slow retrograde conduction properties of the accessory pathway [61].

TREATMENT MODALITIES FOR PREVENTIVE THERAPY — Treatment options for long-term control of SVT include pharmacologic therapy and ablation of the reentrant pathway. The approach is tailored to the individual patient based upon age and severity of symptoms, as summarized in the figure and described above (algorithm 2). (See 'Treatment to prevent supraventricular tachycardia recurrences' above.)

Pharmacologic therapy

First-line prophylactic therapy (beta blocker) — For most patients who require pharmacologic prophylaxis for chronic SVT management, we suggest a beta blocker rather than digoxin or an antiarrhythmic drug. Our preference is based largely on the more favorable side effect profile of beta blockers compared with other antiarrhythmic drugs.

The choice of beta blocker is based upon age:

●Infants – In infants, we use propranolol (2 to 4 mg/kg per day orally divided into four doses)

●Older children – In older children, we use a longer-acting beta blocker such as atenolol or nadolol (both are given at a dose of 1 to 2 mg/kg per day orally)

Side effects of beta blockers include hypotension, bradycardia, emotional disturbances, and nightmares. (See "Major side effects of beta blockers".)

Beta blocker therapy has generally replaced digoxin, which was commonly used to treat SVT in the past, because beta blockers are better tolerated and do not require therapeutic drug monitoring. The rate of SVT recurrence in infants treated with propranolol appears to be comparable with that of digoxin [49,50]. In a multicenter clinical trial involving 71 infants with SVT randomized to propranolol or digoxin, rates of SVT recurrence were similar in both groups (33 and 34 percent, respectively) [49]. No deaths and no serious adverse events related to study medications were observed.

In a retrospective study evaluating data from the Pediatric Health Information System (PHIS) database (2003 to 2013) that included 851 infants <1 year old (44 percent were <30 days old) hospitalized for management of SVT, 73 percent were prescribed antiarrhythmic therapy [62]. Single-agent therapy with propranolol was the most common treatment (44 percent), followed by digoxin (24 percent) and amiodarone (16 percent); multiagent therapy was used in 10 percent of patients. The rate of readmission for SVT within 30 days of hospital discharge was low in this cohort (5 percent) and was similar among patients discharged on propranolol compared with other agents or no therapy.

Another study using data from the PHIS database (2004 to 2015) identified 1339 neonates ≤2 days old who were treated with antiarrhythmic medication(s) for SVT or other nonventricular dysrhythmia [63]. Propranolol use steadily increased during the study period, while digoxin use decreased. In propensity score matching analysis, mortality appeared to be lower among patients treated with propranolol compared with digoxin; however, the finding was not significantly significant (odds ratio 0.64, 95% CI 0.28-1.41).

In a single-center study of 287 infants (median age 17 days), therapy with high-dose enteral propranolol (mean dose 3.6 mg/kg per day) controlled SVT in 67 percent of patients [46]. In this cohort, control of SVT was maintained during outpatient therapy in approximately 90 percent of patients continuing on the medication. Only one patient experienced a clinically significant adverse event (bradycardia) during institution of therapy that resulted in discontinuation of the medication. Patients who failed monotherapy with propranolol were more likely to have congenital heart disease or Wolff-Parkinson-White (WPW) syndrome and were switched successfully to sotalol (n = 53), digoxin (n = 12), amiodarone (n = 7), flecainide (n = 7), or combination therapy.

Second-line agents — For patients who do not achieve adequate control of SVT with beta blocker therapy, options for second-line pharmacologic therapy include flecainide, sotalol, and amiodarone [54-60]. Verapamil should not be used in infants <1 year and children with WPW syndrome. These restrictions limit verapamil's use as a second-line agent in pediatric patients. Digoxin is rarely used to treat SVT in contemporary practice. It was commonly used in the past, but it has been replaced by other more effective and better-tolerated agents.

Second-line drugs may be effective alone or in combination. Their efficacy for the treatment of refractory SVT in children is supported by small case series [54-60].

The side effects of these drugs are generally more serious than those seen with beta blockers. The side effects of each agent are discussed in greater detail separately:

●Flecainide – Flecainide is generally well tolerated, but it can be proarrhythmic and is associated with a variety of noncardiac side effects, including dizziness, blurred vision, headache, and nausea. (See "Major side effects of class I antiarrhythmic drugs", section on 'Flecainide'.)

●Sotalol – Sotalol is generally well tolerated. Major cardiac side effects bradycardia and proarrhythmia. Noncardiac side effects may include fatigue, weakness, and dizziness. (See "Clinical uses of sotalol", section on 'Major side effects'.)

●Amiodarone – Adverse effects associated with amiodarone are summarized in the table and are discussed separately (table 2). (See "Amiodarone: Adverse effects, potential toxicities, and approach to monitoring".)

There are few data comparing these drugs in children with SVT. In the available case series, success rates of these agents ranged from 20 to 100 percent [54-60]. In a case series of 78 infants with refractory SVT (approximately one-half had underlying congenital heart disease), 90 percent achieved control of SVT with high-dose sotalol therapy (median dose 152 mg/m² per day, range 65 to 244 mg/m² per day) [64]. No patients experienced clinically significant QTc prolongation or proarrhythmia. In another retrospective study of 33 infants with SVT (all cases were due to atrioventricular [AV] reentrant tachycardia) treated initially with digoxin, 58 percent had multiple recurrences on digoxin and were transitioned to flecainide, which controlled the SVT in all cases [54]. In a report of 74 children with recurrent SVT treated with oral flecainide (n = 47) or oral amiodarone (n = 27), the proportion of patients who achieved complete or partial success was similar in both groups (81 and 78 percent, respectively) [60]. Of the five children who failed amiodarone and subsequently switched to flecainide, four achieved success. Side effects were generally minor and were less common with flecainide compared with amiodarone (9 versus 22 percent).

Combination therapy is generally reserved for patients with difficult-to-control arrhythmia and requires careful monitoring for proarrhythmic effects [58]. The use of combinations of drugs is variable from institution to institution and patient to patient.

Catheter ablation — Catheter ablation is the definitive therapy for SVT. As discussed in the following sections, success rates at most experienced centers are >90 percent and complication rates are low. However, the risk of complications is increased in infants and small children, which limits its use in that population.

●Indications – We suggest radiofrequency ablation (RFA) for children who are ≥15 kg and who either have frequent episodes of SVT or become symptomatic during infrequent episodes (algorithm 2). For such patients, elective RFA is generally preferred over chronic antiarrhythmic therapy because it avoids the adverse effects of pharmacologic therapy. However, the choice of treatment should be based on shared decision-making with the family.

We agree with the following clinical indications for RFA developed by the Pediatric and Congenital Electrophysiology Society (PACES) and the Heart Rhythm Society (HRS):

•Documented recurrent or persistent SVT that is associated with ventricular dysfunction (in patients ≥15 kg)

•Documented recurrent or persistent SVT when medical therapy is either not effective or is associated with intolerable adverse effects (in patients of any size)

•Documented recurrent or persistent SVT (in patients ≥15 kg) when the family wishes to avoid chronic antiarrhythmic medications

•Documented recurrent SVT that is associated with acute hemodynamic compromise (hypotension or syncope) or that requires emergency medical care or electrical cardioversion (in patients ≥15 kg)

Additional indications are beyond the scope of this topic and are based on other clinical presentations and electrophysiologic (EP) testing, as detailed in the PACES/HRS consensus statement [65].

Although there are data documenting the efficacy of RFA in smaller children [66-68], we generally avoid the procedure in patients <15 kg unless the patient is refractory to medical therapy because of increased risk of complications in small children [69,70].

The role of RFA in asymptomatic patients with WPW pattern on electrocardiogram remains controversial. This is discussed separately. (See "Treatment of arrhythmias associated with the Wolff-Parkinson-White syndrome", section on 'Asymptomatic patients'.)

●Technique – RFA is performed as part of an invasive EP study. Sedation is provided to minimize discomfort and prevent patient movement during the procedure; general anesthesia is often necessary for young children [6,65].

The EP study is performed in two stages:

•Determining the mechanism of SVT and localizing the pathway – In this stage, transvenous catheter electrodes are inserted and manipulated for pacing and recording. The pattern of recordings obtained during normal sinus rhythm, in response to pacing, and during the SVT (if it can be induced) is used to make a definitive diagnosis of the mechanism of the SVT.

•Ablating the pathway – After the mechanism of SVT is determined and the accessory pathway or AV nodal pathway is localized, a modified catheter is used that can deliver radiofrequency energy, which cauterizes the myocardial tissue and destroys the pathway. The standard energy source used for catheter ablation is radiofrequency current. Cryoenergy is an alternative that has been used in children with atrioventricular nodal reentrant tachycardia (AVNRT) [71-74]. In contrast, direct current ablation, which was employed prior to the development of RFA, was associated with a high incidence of complications and is no longer used clinically [75,76].

The technical details of catheter ablation are discussed in greater detail separately. (See "Overview of catheter ablation of cardiac arrhythmias".)

●Efficacy – In the available reports of RFA in children, acute procedural success rates ranged from 80 to 100 percent and recurrences occurred in 5 to 20 percent [32,69,70,77-80]. Success rates have generally improved since the early era of RFA in the 1990s, and rates of recurrence and complications have declined [32,81,82]. In the contemporary era, success rates for pediatric RFA in most experienced centers are >90 percent and complications occur in <5 percent of cases.

The success of RFA depends in part on the mechanism of SVT and the location of the accessory pathway. In a study from a multicenter pediatric RFA registry involving >2500 patients (1800 with accessory pathways, 800 with AVNRT), success rates were 94 percent for patients with accessory pathways and 97 percent for those with AVNRT [78]. For patients with accessory pathways, the highest success rates were seen in children with pathways located in the left free wall (98 percent), whereas success rates were somewhat lower for patients with right free wall, right septal, and left septal pathways (90, 89, and 88 percent, respectively). A study evaluating data from three large registries from three distinct eras (the pediatric RFA registry [1994 to 1997], the Prospective Assessment After Pediatric Cardiac Ablation registry [2002 to 2004], and the MAP-IT registry [2014 to 2016]) found that acute success rates improved over time for both accessory and slow pathway substrates while fluoroscopy and procedural time decreased [82]. Long-term follow-up studies from centers in Europe reported recurrence rates of 10 to 15 percent at follow-up of two to five years after RFA [79,81].

●Complications – Procedural complications associated with RFA are uncommon, occurring in <5 percent of cases [70,78,79,81,82]. In a report from the MAP-IT registry including 1417 procedures performed at 12 North American centers between 2014 and 2016, the reported complication rate was 3.6 percent [82]. Most studies assessing complications of RFA use a fairly broad definition, including major, minor, and transient adverse events.

In earlier registry studies, EP study-related complications were reported in 2.9 percent of procedures and ablation-related complications were reported in 3.2 percent [70,78]. The most common EP study-related complication was hematoma at the catheter insertion site (1.4 percent). The most common ablation-related complication was AV block (0.7 to 1.3 percent), which occurred only in patients with AVNRT or septal accessory pathways and did not occur in patients undergoing ablation of accessory pathways located in the right or left free wall. Other complications included right bundle branch block (0.7 percent), perforation and/or pericardial effusion (0.1 to 0.7 percent), brachial plexus injury (0.2 to 0.3 percent), valvular regurgitation (0.3 percent), emboli (0 to 0.2 percent), and pneumothorax (0 to 0.2 percent). There were four procedure-related deaths in the earliest cohort (0.1 percent) [70] and no deaths in the later cohort [78].

Risk factors for complications based largely on the experience reported in the Pediatric RFA registry studies from the 1990s to early 2000s include patient age <4 years, patient weight <15 kg, and center inexperience with the procedure [69,70,83,84].

Surgical therapy — Though surgical ablation is an effective treatment for drug-refractory SVT, it has largely been replaced by RFA. In the modern era, surgery is reserved for the rare instances in which an arrhythmia is refractory to attempted RFA and those occasions in which another cardiac surgical procedure is planned as part of the patient's management (eg, tricuspid valve repair for Ebstein anomaly) [85-87]. (See "Treatment of arrhythmias associated with the Wolff-Parkinson-White syndrome", section on 'Surgical ablation' and "Ebstein anomaly: Management and prognosis", section on 'Surgical or catheter intervention'.)

OUTCOME — Most infants and children who present with SVT recover fully; however, recurrences are fairly common.

●SVT recurrence – Most patients experience at least one recurrence of SVT after the initial episode. The likelihood of recurrence depends on the age at presentation, mechanism of SVT, and treatment given.

•For patients who present in infancy with atrioventricular reentrant tachycardia (which is the most common mechanism of SVT in children), symptoms often resolve by one year of age, though recurrences can occur later in life [88]. The natural histories of different types of SVT are discussed in greater detail separately. (See "Clinical features and diagnosis of supraventricular tachycardia (SVT) in children", section on 'Natural history'.)

•As discussed above, approximately 10 to 15 percent of patients who have undergone catheter ablation experience late recurrences. (See 'Catheter ablation' above.)

●Mortality – The risk of mortality associated with SVT is very low, though it is greater in patients with underlying structural heart disease (eg, congenital heart disease or cardiomyopathy) compared with those without structural heart disease [89,90]. In a population-based study from Taiwan that included 2021 infants and children with SVT with average follow-up of 10.8 years, the annual mortality rate was 0.2 percent per year [90]. Mortality was greatest among patients with congenital heart disease or cardiomyopathy. Similar findings were noted in a retrospective study of 1755 hospitalized pediatric and young adult patients (age <25 years) with SVT, in which hospital mortality was 6 percent among patients with structural heart disease compared with 1 percent in patients without structural heart disease [89].

Patients with Wolff-Parkinson-White syndrome are at increased risk for sudden cardiac death, though the overall risk is low [91]. The cause of sudden cardiac death is not SVT but rather ventricular fibrillation, which can occur during an episode of atrial fibrillation if there is rapid conduction to the ventricle. This issue is discussed in greater detail separately. (See "Clinical features and diagnosis of supraventricular tachycardia (SVT) in children", section on 'Ventricular fibrillation and sudden death' and "Wolff-Parkinson-White syndrome: Anatomy, epidemiology, clinical manifestations, and diagnosis", section on 'Mechanism of and risk factors for SCD in WPW'.)

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" and "Society guideline links: Basic and advanced cardiac life support in children" and "Society guideline links: Supraventricular arrhythmias".)

SUMMARY AND RECOMMENDATIONS

●Acute management – The acute management of supraventricular tachycardia (SVT) in infants and children consists of interventions to terminate the tachyarrhythmia with ongoing assessment the patient's clinical status. The urgency and choice of treatment depend on the patient's hemodynamic stability (table 1) (see 'Acute management' above):

•Unstable SVT – Synchronized direct current cardioversion with 0.5 to 1 J/kg is the definitive treatment for SVT in children who are hemodynamically unstable (table 1 and algorithm 1). The dose can be increased to 2 J/kg if the lower dose is ineffective. Adenosine may be given while preparing to cardiovert if the drug is readily available and the child has intravenous (IV) access. Similarly, vagal maneuvers can be attempted while preparing for cardioversion or drug therapy, but cardioversion should not be delayed to administer vagal maneuvers. (See 'Unstable patients' above.)

•Stable SVT – In patients who are hemodynamically stable, additional time can be given to evaluate the rhythm. The approach to management of SVT in stable patients is as follows (table 1) (see 'Stable patients' above):

-We recommend vagal maneuvers as the initial intervention rather than pharmacologic therapy (Grade 1B). For an infant, this consists of applying an ice bag to the face for 15 to 30 seconds. In older children, vagal maneuvers include bearing down (Valsalva maneuver), blowing into an occluded straw, or assuming a head-down position for 15 to 20 seconds. (See 'Vagal maneuvers' above.)

-If vagal maneuvers are ineffective, we suggest IV adenosine rather than other antiarrhythmic drugs (Grade 2C). Adenosine is administered at a dose of 0.1 mg/kg (maximum 6 mg), followed by a rapid saline flush. If no response is seen within two minutes, the dose should be doubled (ie, 0.2 mg/kg IV, maximum 12 mg). (See 'First-line therapy (adenosine)' above.)

-For SVT that is refractory to adenosine, choices for IV antiarrhythmic therapy include procainamide and amiodarone. These drugs have potential for serious adverse effects, and, therefore, consultation with a pediatric cardiologist is advised. Verapamil is another option; however, it should not be used in infants <1 year old or patients with known or suspected Wolff-Parkinson-White (WPW) syndrome. Beta blocker therapy (eg, IV esmolol or oral propranolol) is an alternative to IV antiarrhythmic therapy if the SVT appears to be well tolerated (ie, hemodynamically stable and no symptoms) and the patient is in a closely monitored setting. (See 'Supraventricular tachycardia refractory to adenosine' above.)

●Evaluation after the episode – After the acute episode is terminated, an electrocardiogram (ECG) and echocardiogram should be performed to look for evidence of WPW syndrome (waveform 1) and structural heart disease. (See 'Evaluation after the acute episode' above and "Clinical features and diagnosis of supraventricular tachycardia (SVT) in children", section on 'Diagnosis'.)

●Chronic management – Options for chronic management of SVT include expectant management, pharmacologic therapy, and catheter ablation. The approach is tailored to the individual patient based upon age and severity of symptoms (algorithm 2) (see 'Treatment to prevent supraventricular tachycardia recurrences' above):

•Infants <1 year – For most infants with SVT, we suggest prophylactic pharmacologic therapy rather than expectant management (Grade 2C). However, expectant management is a reasonable option after the first episode if the infant is asymptomatic and hemodynamically stable with normal ventricular function. When prophylactic therapy is used, we suggest a beta blocker (eg, propranolol) as the first-line agent rather than other drugs (Grade 2C). This is based largely on the side effect profile of beta blockers, which is generally more favorable than that of other antiarrhythmic drugs. (See 'Infants <1 year' above and 'First-line prophylactic therapy (beta blocker)' above.)

•Children ≥1 year – For children ≥1 year, the approach to chronic management depends on the severity of symptoms and the size of the child (algorithm 2):

-First episode, minimal symptoms – For patients presenting after the first episode of SVT who have no or only minimal symptoms and who have no evidence of hemodynamic instability or ventricular dysfunction, we suggest expectant management rather than pharmacologic or catheter-based intervention (Grade 2C). The child is monitored for at least 24 hours, and the parents are taught how to check the heart rate. The parents (and child, if able) are also taught how to use vagal maneuvers (eg, applying an ice bag to the face, performing the Valsalva maneuver, assuming a head-down position, and other techniques) to assist in self-termination of SVT if it recurs. (See 'First episode, minimal symptoms' above and 'Vagal maneuvers' above.)

-Recurrent and/or symptomatic SVT episodes – For children who have frequent episodes of SVT or who become symptomatic during infrequent episodes, we suggest intervention to prevent further recurrences (Grade 2C). The choice of intervention depends on the size of the child. For most infants and young children <15 kg, we suggest prophylactic medical therapy rather than catheter ablation (Grade 2C). Pharmacologic therapy is preferred in this setting because the risk of complications with catheter ablation is increased in small children. We suggest a beta blocker (eg, atenolol, nadolol) as the first-line agent rather than other drugs (Grade 2C). For children who are ≥15 kg, we suggest catheter ablation rather than chronic antiarrhythmic medication (Grade 2C). (See 'Children ≥1 year' above and 'First-line prophylactic therapy (beta blocker)' above and 'Catheter ablation' above.)

●Outcome – Most infants and children who present with SVT recover fully; however, recurrences are common. The risk of mortality associated with SVT is very low. (See 'Outcome' above.)