Pediatric Atrial Flutter

Atrial flutter is an electrocardiographic descriptor used both specifically and nonspecifically to describe various atrial tachycardias. The term was originally applied to adults with regular atrial depolarizations at a rate of 260-340 beats per minute (bpm). Historically, the diagnosis of atrial flutter was restricted to those patients whose surface electrocardiogram (ECG) revealed the classic appearance of "flutter waves." This sharp demarcation is used less frequently in the current era, where the more electrophysiologically descriptive "atrial reentry tachycardia" is used instead.

Atrial flutter is infrequent in children without congenital heart disease. In these patients with otherwise normal cardiac anatomy atrial reentry tachycardias are observed mostly during fetal life in late pregnancy, and during adolescence.

In the fetus, atrial flutter is defined as a rapid regular atrial rate of 300-600 bpm accompanied by variable degrees of atrioventricular (AV) conduction block, resulting in slower ventricular rates.

During this type of tachycardia, the atrial rate is so rapid that normal AV nodes usually display a physiologic second-degree block, with a resultant 2:1 conduction ratio. In individuals with AV nodal disease or increased vagal tone, or when certain drugs are used, higher degrees of AV block may develop, such as 3:1 or higher. In individuals with accessory AV nodal pathways, a 1:1 conduction ratio may occur through the accessory pathway with resultant ventricular rates of 260-340 bpm, which can cause sudden death. A 1:1 conduction ratio may also occur when the atrial rate is relatively slow (eg, < 340 bpm) during atrial flutter or when physiologic processes facilitate AV nodal conduction, such that a rapid ventricular response can still result in sudden death.

Patients who have undergone Mustard, Senning, or Fontan operations are more prone to developing this arrhythmia because of atrial scars from surgery and right atrial enlargement, usually seen after the classic Fontan operation. Similarly, patients who have undergone surgical repair of an atrial septal defect, total anomalous pulmonary venous connection, and tetralogy of Fallot may later develop atrial flutter.[1] Individuals with muscular dystrophies such as Emery-Dreifuss[2] and myotonic dystrophy[3] may also develop atrial flutter, as well as those with dilated, restrictive, and hypertrophic cardiomyopathies.

Treatment of children with atrial flutter depends on the age of presentation and baseline cardiac anatomy. Fetal atrial flutter is usually treated with oral maternal antiarrhythmic agents without need for further intervention if ventricular function is acceptable and if there is no placental edema. Once the baby is born, it usually responds well to oral antiarrhythmic medications and subsequently resolves. In the other age groups and in patients with baseline abnormal cardiac anatomy or surgical scars, it usually recurs. In general, treatment may involve medications, cardiac pacing, cardioversion, radiofrequency catheter ablation, or surgical procedures (see Treatment). Drug therapy of atrial flutter in children can be classified under the 3 broad headings of ventricular rate control, acute conversion, and chronic suppression (see Medication).

See Atrial Flutter and Emergent Management of Atrial Flutter for more information on these topics.

Patient education

For patient education information, see the Heart Health Center, as well as Atrial Flutter, Tetralogy of Fallot, and Supraventricular Tachycardia.

Atrial flutter is a reentrant arrhythmia circuit confined to the atrial chambers. As a rule, atrial flutter originates in the right atrium, whereas atrial fibrillation, which is more frequent in adults, originates in the left atrium.

A flutter circuit typically surrounds an anatomical or functional barrier and includes a zone of slow conduction (or conduction over an extended circuit) and an area of unidirectional block, as required for reentry of all types. Frequently, a premature beat blocks one limb of the circuit and is sufficiently delayed in the other limb (while traversing around the anatomical or functional barrier) to allow for recovery from refractoriness in the first limb.

The reentrant circuits that occur in children with atrial flutter after congenital heart disease surgery are believed to involve abnormal atrial tissue that has been subject to chronic cyanosis, inflammation secondary to surgery, scarring, and increased wall stress in cases of enlarged atria. Such circuits may encircle anatomical barriers such as atriotomy scars or surgical anastomoses, and they may use areas of slow conduction along baffle limbs and other sites of injury in addition to the tricuspid valve–coronary sinus isthmus.

Sinus node dysfunction with bradycardia is generally present in many of these patients years after surgery. This is a contributing factor for development and maintenance of atrial flutter.

Atrial flutter circuits in children with congenital heart disease are typically more variable than those seen in adults. For the most part, atrial flutter circuits in adults are confined to the tricuspid valve–coronary sinus isthmus (or isthmus-dependent flutter).

In the fetus, atrial flutter occurs mainly during the third trimester, although it can occur as early as midgestation.[4] The atrium is believed to reach a critical mass to support an intra-atrial macroreentry circuit at about 27-30 weeks’ gestation. One study demonstrated an association between fetal atrial flutter with atrioventricular reciprocating tachycardia and accessory pathways. They also found that, compared to the neonate, accessory pathways in the fetus had a greater propensity for spontaneous, natural conduction, a finding that may indicate accessory pathways often become nonfunctional at late stages of fetal development.[4]

Atrial flutter may comprise up to one third of all fetal tachyarrhythmias.[4] Most fetuses and neonates with atrial flutter have structurally normal hearts. However, when atrial flutter is detected in a fetus, structural cardiac anomalies such as Ebstein anomaly of the tricuspid valve and atrioventricular (AV) septal defects should be ruled out because of a higher incidence of such defects in these cases.

Some newborns and young children have associated conditions or anomalies that may predispose them to atrial flutter. Atrial septal aneurysms appear to be associated with sustained atrial arrhythmias in newborns, but this association is not as high as is seen in adult subjects. Restrictive cardiomyopathies are also associated with refractory atrial flutter. In Costello syndrome, the dysmorphic appearance is also associated with a dysrhythmia characterized as chaotic atrial tachycardia, and this dysrhythmia may include long episodes of atrial flutter.

Atrial flutter is not uncommon in the immediate postoperative period after congenital heart surgery. Surgery-induced inflammation of the pericardium, scarring, and volume overload may trigger atrial flutter.

Case reports have linked atrial flutter to ingestion of herbal medicines and certain foods. These episodes did not recur after avoidance of the triggers.

Atrial flutter and atrial fibrillation have been related to obesity, alcohol consumption, and hyperthyroidism.[5, 6, 7] One study reported that in adults, diabetes mellitus is a strong independent risk factor for development of atrial flutter and atrial fibrillation.[8]

Atrial flutter is most commonly seen after the Senning or Mustard surgical procedures for transposition of the great arteries (used in the past) and after Fontan repair. According to a United States study, 57% of patients with double-inlet left ventricle who undergo the Fontan operation may be expected to present with atrial flutter or fibrillation by 20 years after surgery.[9] This high prevalence of atrial flutter or fibrillation seen in the atriopulmonary connection type of Fontan operation, however, is not as frequent with the total cavopulmonary connection type of Fontan procedure. The mean annual incidence of new dysrhythmias (predominantly atrial flutter) after the Fontan operation is 5%. According to a multicenter study, tachyarrhythmia prevalence over time was similar between the intracardiac lateral tunnel and the extracardiac conduit Fontan operations.[10]

In an international review, atrial flutter accounted for 26.2% of all cases of fetal tachyarrhythmias, and supraventricular tachycardia (SVT) accounted for 73.2%.[11] In an earlier population study of 3383 English newborns by Southall and colleagues, only 1 newborn had atrial flutter.[12] This likely underestimated the incidence of atrial flutter in utero because spontaneous conversion often occurs during birth and subsequent recurrence is uncommon.

A long-term follow-up study into adulthood of patients undergoing the Mustard or Senning procedure for correction of D-transposition of the great arteries demonstrated SVT in 48%, of which atrial flutter was the most common type (73%). Arrhythmias accounted for 12.7% of pediatric cardiology consultations in a major pediatric academic medical center, of which atrial flutter was the second most common type.

Sexual and age-related differences in incidence

Following atrial septal defect repair, the prevalence of atrial flutter is higher in females (70.7%) than in males. Patients with Fontan repairs present with flutter either as children or as adults. Patients with repaired tetralogy of Fallot tend to present with atrial flutter as young adults. Because the Mustard and Senning procedures are now rarely performed, the cohort of patients with this substrate typically consists of older adolescents and adults.

One study reported that the recurrence rate of atrial flutter and fibrillation in women with preexisting cardiac rhythm disorders during pregnancy was the highest of all the studied arrhythmias, reaching 52%.[13]

Neonatal atrial flutter is usually a self-limiting illness, requiring only conversion of the rhythm with esophageal atrial pacing or cardioversion. Incisional reentrant atrial tachycardia following complex atrial surgery in the repair of congenital heart disease may occur early in the postoperative period; this event is predictive of the occurrence of late postoperative flutter. The prevalence of atrial flutter in several classes of postoperative patients increases with the duration of follow-up.

Morbidity and mortality in patients with atrial flutter largely depend on the following factors:

• Age at presentation

• Cardiac anatomy (normal anatomy vs congenital heart disease)

• Integrity and anatomy of the myocardial conduction system (normal sinus node vs sinus node dysfunction; atrioventricular (AV) block vs normal AV node, with or without accessory pathways)

• Ventricular function

• Prompt recognition of the arrhythmia and initiation of adequate therapy

The fetus with atrial flutter may have significant morbidity and be at risk for mortality. According to one review, hydrops fetalis developed in as many as 40% of fetuses with atrial flutter. The mortality rate in these fetuses was 8%.[11]

Mortality in newborns with atrial flutter is uncommon. Most patients remain in sinus rhythm following their initial conversion, and the need for antiarrhythmic prophylaxis in these patients during infancy is debated.

In patients with postoperative atrial flutter that develops late following repair of congenital heart disease, the outcome depends on the atrial flutter rate, conduction ratio, and presence of ventricular dysfunction. In patients who have undergone the Mustard procedure, Holter recordings incidentally capturing episodes of sudden fatality confirm that rapidly conducted atrial flutter is the dysrhythmia most frequently responsible for these fatalities.

In contrast, patients who have undergone the Fontan procedure rarely die suddenly but frequently present with symptomatic atrial flutter. This may be caused by a relatively slower atrial flutter rate, a higher degree of AV conduction block, or both.

Prolonged episodes of atrial flutter in asymptomatic or mildly symptomatic patients may be associated with development of atrial thrombi and although this is rare in the congenital heart disease population as is the possibility of thromboembolic event.

When women with heart disease and arrhythmias reach childbearing age, arrhythmias can recur during pregnancy. These arrhythmias significantly increase the risk both for the mother and fetus.

The setting and associated features of atrial flutter are an important aspect of the assessment of atrial flutter. This information may guide the design of a treatment plan, particularly in patients with repaired congenital heart disease.

Atrial flutter may be perceived as a regular or irregular palpitation, the latter suggesting variable atrioventricular (AV) conduction. The flutter may be associated with syncope, severe presyncope, or chest pain, suggesting either periods of 1:1 conduction ratio or associated ventricular dysfunction. Characterizing a history of previous self-terminating episodes is important. Rare and minimally symptomatic self-terminating episodes of atrial flutter are likely to require less treatment.

The presence of associated sinus node disease with episodes of sinus bradycardia may provide an indication for pacemaker therapy. This finding also adds to the antiarrhythmic medical options for atrial flutter.

Repaired congenital heart disease

Understanding the specific anatomy and surgical repair for each patient is important. Certain types of repair are more commonly associated with late atrial flutter than others.

In Fontan-type operations, atriopulmonary connections are associated with a risk of atrial flutter that is 2.5-fold higher than with the total cavopulmonary connection. Extracardiac Fontan repairs may have an even lower frequency of atrial flutter.

The type of repair may influence the technical approach to electrophysiological study, pacemaker placement, potential radiofrequency ablation therapy, or potential Fontan surgical revision. For example, patients who have the classic Fontan operation are amenable to ablation attempts of the atrial flutter in the electrophysiology laboratory because the right atrium can be approached via the inferior and/or superior vena cava. In addition, endocardial pacemaker leads can be inserted if the patient has sinus node dysfunction.

However, patients who have an extracardiac Fontan repair in which the right atrium has been bypassed with a baffle require open-heart surgery if ablation is contemplated, which is performed at the time of their Fontan revision. In addition, only epicardial pacemaker leads can be placed in these patients.

Atrial flutter also has prognostic significance in this setting. Several studies have shown that atrial flutter in the early postoperative period in patients who have undergone the Fontan operation predicts both early operative mortality and recurrence of the arrhythmia.

In patients with congenital heart disease who have undergone surgery, episodes of atrial flutter have been shown to increase in frequency over time.

Physical examination in patients with atrial flutter should assess the likely conduction ratio and rate of flutter and assess for signs of associated ventricular dysfunction or heart failure. Depending on the ventricular rate and the individual's tolerance to that rate, symptoms may range from palpitations, dyspnea, presyncope, or syncope to sudden death. If the ventricular response is rapid, atrial flutter may cause significant morbidity secondary to hemodynamic deterioration due to low cardiac output.

If the ventricular response is slow enough to permit a sustained arrhythmia, atrial thrombosis with consequent thromboembolism may result. In patients who have undergone surgery for congenital heart disease, new onset of atrial arrhythmias such as atrial flutter may indicate elevated right atrial pressure and, thus, the need for surgery (eg, conduit obstruction in a patient with a Rastelli-type surgery).

In patients who have undergone the Fontan, Mustard, or Senning operation, the presence of superficial venous collateralization suggests associated obstruction of major venous pathways. This may interfere with evaluation and management.

Complications

Episodes of atrial flutter may be associated with low cardiac output, brain and other end-organ injury, and sudden or subacute death.

Heart failure, thrombosis, and thromboembolism are other recognized complications.

A 12-lead to 15-lead electrocardiogram (ECG) is the mainstay of atrial flutter diagnosis. Atrial flutter is a reentrant arrhythmia circuit confined to the atrial chambers. Such a circuit may be macroscopic and, therefore, amenable to mapping by techniques using standard electrophysiologic catheters or it may be microscopic and amenable to mapping only in the research laboratory using fine electrode arrays.

Depending on the drug used, patients receiving antiarrhythmic therapy may benefit from the monitoring of specific drug blood levels and electrolyte and creatinine levels or ECG monitoring of the QTc (eg, class III agents).

Electrophysiologic studies may be useful for mapping arrhythmia circuits. Consider transesophageal echocardiography in patients with associated structural or functional heart disease to ascertain the presence of intracardiac thrombi, myocardial dysfunction, or hemodynamically important residual structural defects that could predispose them to atrial flutter.

Coagulation studies

Optimize anticoagulation through monitoring of coagulation profiles in patients receiving heparin or warfarin. In patients with documented intracardiac thrombi, monitor for the presence of associated thrombophilia, as indicated.

A rapid atrial tachycardia with uniform P waves with flutter morphology and variable atrioventricular (AV) block indicates that atrial flutter or atrial ectopic tachycardia is present. See the image below.

If the onset of tachycardia was recorded, the absence of "warm-up" of the tachycardia cycle length makes atrial flutter the most likely diagnosis. Similarly, sudden termination of the tachycardia points to atrial flutter.

If the conduction ratio is consistently 1:1, the diagnosis is more difficult. The QRS complex may be aberrantly conducted at this rate, and ventricular tachycardia must be considered in the differential diagnosis. A 1:1 conduction ratio may produce a ventricular rate of 300 beats per minute in children, in patients with the pre-excitation syndrome, in those whose AV nodes conduct rapidly, and occasionally in patients with hyperthyroidism.

With a 2:1 conduction ratio, every other flutter wave may be hidden within the QRS complex. In this case, the electrocardiographic (ECG) findings often suggest a mild sinus tachycardia with first-degree AV block. Because adrenergic states that cause sinus tachycardia usually shorten rather than prolong the PR interval, the differential diagnosis of atrial flutter should be considered.

Assessment of heart rate or conduction ratio responses to vagal maneuvers or adenosine may be helpful.

According to one study, V1 was the most important ECG lead that aided diagnosis of the supraventricular tachycardia (SVT) mechanism; the study also reported that combining V1 with the inferior limb lead III increased the chances of identifying the SVT mechanism from 80% to 96%.[14]

In patients with possible atrial flutter occurring soon after the repair of congenital heart disease, the use of temporary atrial pacing wires is extremely helpful in diagnosis and therapy. Unipolar atrial wire recordings or bipolar recordings with a simultaneously recorded surface ECG may be used to confirm a suspected atrial flutter with 2:1 conduction ratio by unmasking the second flutter wave.

In patients without temporary atrial wires, the use of an esophageal electrode placed behind the left atrium is also extremely helpful for diagnosis and therapy. Bipolar recordings with a simultaneously recorded surface ECG can be optimized by advancing or withdrawing the electrode until the atrial electrogram is at its maximal size.

Modern atrial or dual-chamber pacemakers can provide a unipolar or bipolar atrial electrograms by telemetry from the device.

P-wave signal averaging using a specialized ECG has demonstrated some ability to differentiate adults who are likely to develop occurrences or recurrences of atrial fibrillation. This technique has been adapted to predict the occurrence of atrial flutter following the Fontan procedure.

Electrical termination of atrial flutter and additional testing can be performed through atrial wires, esophageal electrodes, permanent pacing systems, or during an intracardiac electrophysiology study. These studies may identify whether an arrhythmia is reproducibly overdriveable, and invasive testing may help identify the specific arrhythmia circuit.

Three-dimensional electroanatomical physiologic mapping of atrial arrhythmias is helpful, especially in patients who have undergone atriotomies because of the presence of multiple, extended, and/or complex reentry circuits.

The reentrant arrhythmia circuit confined to the atrial chambers may be macroscopic and mappable using standard electrophysiologic catheters or it may be microscopic and mappable only in the research laboratory using fine electrode arrays.

Postcatheterization precautions include hemorrhage, vascular disruption (if the patient underwent concomitant balloon dilation of a stenosed vessel), pain, nausea and vomiting, and arterial or venous obstruction from thrombosis or spasm. Complications may also include tachyarrhythmias or bradyarrhythmias.

In children with atrial flutter, medical care should be broadly directed at the following:

• Ensuring hemodynamic stability before, during, and after conversion to sinus rhythm

• Minimizing influences favoring initiation or maintenance of atrial arrhythmias (eg, electrolyte disturbances, pericardial effusion, indwelling atrial lines or catheters)

• Excluding or managing complications (eg, ventricular dysfunction, thromboembolic phenomena)

Restoring drug therapy may be indicated in some children with atrial flutter. Drug therapy in these cases can be classified under the 3 broad headings of ventricular rate control, acute conversion, and chronic suppression.

Thrombosis and thromboembolic events are recognized complications in patients with atrial flutter, particularly in the setting of repaired congenital heart disease, such as the Fontan procedure.[15] Patients who have thrombi identified on transesophageal echocardiography or have a history of chronic atrial flutter (>2 wk duration) should be treated with a period of anticoagulation (2-4 wk), if hemodynamically and symptomatically tolerated, before undergoing direct current (DC) cardioversion or other conversion of their rhythm.

A systematic review that analyzed data from 52 articles suggested that atrial flutter indeed confers a thromboembolic risk; a 0% to 38% prevalence of thrombus was seen, and a 21% to 28% prevalence of spontaneous echocardiographic contrast was observed.[16] In another study, there was a high incidence of thrombus/thromboembolism with atrial flutter or fibrillation in patients who underwent the Fontan surgery, but it was low in this population in the setting of electrical cardioversion and anticoagulation therapy.[15]

According to a legal precedent, patients with Mustard repair of transposition of the great vessels and sick sinus syndrome should not receive quinidine without a previously implanted pacemaker. However, quinidine is now recognized to have a detrimental adverse effect profile in general, and it is essentially no longer used in the treatment of rhythm disorders following congenital heart disease. Disagreement surrounds whether this recommendation should be extrapolated to other antiarrhythmics and other forms of repaired congenital heart disease.

See Atrial Flutter and Emergent Management of Atrial Flutter for more information on these topics.

Transfer considerations

As with most symptomatic arrhythmias, conversion should ideally be achieved before transfer, except in the case of a hemodynamically stable patient referred to an institution with clearly superior expertise and facilities for management of pediatric atrial flutter.

Pace-termination of atrial flutter is best performed with a programmable stimulator that is capable of sensing atrial electrograms and delivering single, double, or multiple extrastimuli at adequate output and individually programmable cycle lengths down to 100 milliseconds.

Short discrete ramps or bursts of atrial stimuli are the most likely to produce a type I conversion of atrial flutter (immediate conversion to sinus rhythm), particularly if they can be delivered in or near the flutter circuit. If such a device is unavailable, a pacemaker capable of burst pacing at a specified rate may be used.

If pacing is performed via an esophageal electrode, the device should be capable of delivering stimuli at pulse widths of 9.9-20 milliseconds and outputs of 10-26 mA.

Patients who are treated with atrial antitachycardia pacing should undergo testing to confirm that their device is effective and not proarrhythmic.

R-wave synchronized cardioversion is the mainstay of therapy in patients who are unstable or if other therapies have failed. In patients who are stable and have chronic atrial flutter, perform cardioversion only after documentation of freedom from intracardiac thrombi or following a 2-week course of anticoagulation.

Cardioversion may be performed at increasing doses of 0.5, 1, 2, and 4 J/kg. Newer biphasic waveform defibrillators may allow for lower energy applications.[17]

Ideally, place defibrillator paddles or pads in an anteroposterior configuration, with the apex paddle located over the mid sternum and the base paddle between the scapulae. An anesthesiologist usually administers a brief general anesthetic, except in truly emergent circumstances that mandate immediate cardioversion.

Hemodynamic instability requires immediate cardioversion as described above. However, patients who are relatively stable may be allowed to remain in flutter while careful consideration of possible interventions is undertaken. The patient should rest in a supine position without undue excitement or agitation. Consider digoxin if not already in use because it frequently increases the conduction ratio and decreases the ventricular rate. However, this effect usually takes many hours.

Medications with the potential to slow the atrial rate without affecting the atrioventricular (AV) node should be used with caution because the conduction ratio often decreases to 1:1 AV association. This may result in a rapid ventricular rate and hemodynamic compromise.

Avoid adrenergic and atropinic agents during sedation or anesthesia for cardioversion. Ketamine is relatively contraindicated. Such agents may result in rapid 1:1 AV conduction, with resultant hemodynamic compromise. On the other hand, insufficient sedation during attempted esophageal overdrive pacing or a failed cardioversion may result in patient distress and 1:1 AV conduction ratio.

Although neonatal atrial flutter usually responds to single cardioversion, occasional cases may require multiple cardioversions and/or the need to add amiodarone.[18]

Currently, radiofrequency catheter ablation appears to be somewhat effective in treating postoperative intra-atrial reentrant tachycardia in children.

Because the flutter circuits and critical isthmuses are quite variable in these patients, mapping of flutter circuits may be enhanced by 3-dimensional electroanatomical display systems, identification of split potentials, and demonstration of concealed entrainment during pacing.

In patients with atrial flutter, surgical care may include one of the following procedures:

• Correction of hemodynamic lesions that could be causing atrial volume loading

• Specifically placed atrial incisions or cryoablation prophylactically to prevent atrial flutter

• Empiric or map-directed lesions to eliminate documented atrial flutter and its circuits

These surgeries include various modifications and updates to maze procedures and modifications of the Mustard and Fontan procedures. One study reported that a right-sided maze procedure in patients with atrial flutter or fibrillation undergoing congenital heart disease repair significantly reduced arrhythmia recurrence at a mean of 2.7 y after surgery.[19]

Aggressive strategies to convert atrial flutter and maintain sinus rhythm should be pursued in children. In rare cases of resistant chronic atrial flutter when only rate control can be accomplished, patients should avoid competitive sports. Also restrict the activities of patients likely to develop rapid conduction of intermittent acute episodes of flutter.

Atrial stretch, surgical scarring, and sinus node dysfunction all appear to play important roles in the development of atrial flutter in patients with congenital heart disease. The development of new surgical techniques to avoid atrial suture lines or dilatation and to prophylactically interrupt potential conduction isthmuses within the atria may reduce the frequency of this disorder in future surgical cohorts of patients with congenital heart disease.

Efforts directed at sparing the sinus node during surgery, coupled with more aggressive pacing strategies in patients with sinus node dysfunction, could also play an important role in prevention of atrial flutter.

No specific guidelines have been developed for the management of pediatric atrial flutter. The 2015 American College of Cardiology, American Heart Association, and the Heart Rhythm Society (ACC/AHA/HRS) joint guidelines for the management of supraventricular tachycardia note that although the guidelines are intended for adults (age ≥18 years) and offer no specific recommendations for pediatric patients, in some cases, the data from noninfant pediatric patients was reviewed and helped to apprise the guidelines.[20]

The guidelines state that pharmacologic therapy for pediatric atrial flutter is largely based on practice patterns owing to the lack of random controlled trials of antiarrhythmic medications in children. Amiodarone, sotalol, propafenone, or flecainide may be used in infants. In older children, beta-blockers are used most often as the initial therapy. Flecainide is not used as a first-line agent in children because of the rare occurrence of adverse events. Catheter ablation may be successfully performed in children of all ages, with success rates comparable to those reported in adults.[20]

Drug therapy of atrial flutter in children can be classified under the 3 broad headings of ventricular rate control, acute conversion, and chronic suppression.

Digoxin is relatively safe for preventing rapid conduction of atrial flutter via the atrioventricular (AV) node to the ventricles, and some evidence indicates that this reduces symptomatology during flutter. Nevertheless, digoxin is unlikely to be particularly effective in the acute conversion or prevention of atrial flutter recurrence. It is devoid of negative inotropic effects (as is amiodarone) and is useful to control ventricular rate when using propafenone, flecainide, or procainamide.

Intravenous procainamide has been used with variable success to effect acute conversion of atrial flutter to sinus rhythm. Procainamide infusion should be preceded by digitalization to prevent procainamide-induced acceleration of AV node conduction to the ventricles.

The Vaughan Williams class III agents ibutilide and dofetilide may be used for acute conversion of atrial flutter and fibrillation. Both are more effective than other medications in converting atrial flutter, but their use is associated with QT prolongation with a nontrivial risk of induction of torsade de pointes polymorphic ventricular tachycardia. Clinical experience in adults is limited, and efficacy, dosing, and safety in children have not been established.

A relatively more recent drug, dronedarone, a less-lipophilic amiodarone analog, has been shown to prevent recurrence of atrial flutter and atrial fibrillation in adult patients, according to several multicenter trials. However, it increases mortality in patients with decompensated heart failure and therefore should be avoided in such cases.[21] Safety and efficacy of this drug have not been confirmed in patients younger than 18 years.

Fetal atrial flutter is the second most common intrauterine tachyarrhythmia. Treatment is aimed at controlling ventricular rate and, thus, avoiding hydrops fetalis. First-line treatment is digoxin administered to the mother, which provides a conversion rate to sinus rhythm of 45-52%. In addition, its positive inotropic effect may be beneficial. More recently, a retrospective study involving data from 21 fetuses with supraventricular tachycardia and 2 cases of atrial flutter suggests that flecainide may be effective and safe as first-line therapy for fetal supraventricular tachycardia.[22]  Of 17 fetuses treated with flecainide monotherapy, 15 converted to sinus rhythm while 2 were refractory.

Sotalol has also been used in numerous cases with success,  including children with incessant tachyarrhythmias.[23]  Maternal drug levels were not reliable predictors of successful therapy.[24, 25] Flecainide alone or in combination with digoxin is used as second-line treatment, although one study suggests that flecainide may be an effective first-line therapy for fetal supraventricular tachycardia.[26]  Fetal atrial flutter in a structurally normal heart seldom recurs after conversion before or after birth, and postnatal suppressive antiarrhythmic therapy may not be necessary.

Flutter in patients with repaired or palliated structural congenital lesions is more likely to recur, and long-term antiarrhythmic therapy aimed at flutter suppression is often instituted after the first or the second flutter episode.

Vaughan Williams class IC (eg, flecainide, propafenone) or class III (eg, sotalol, amiodarone) agents have been prescribed with variable success. Some authors have cautioned against use of flecainide in this setting, but the data are equivocal. Combinations of agents occasionally succeed after failure of single-agent therapy.

Use of antiarrhythmic agents other than digoxin for the long-term suppression of atrial flutter in sinus node disease (a frequent coexisting finding) is particularly controversial. In patients with atrial flutter who have had the Mustard procedure, treatment with quinidine was associated with case reports of sudden death. This resulted in the recommendation of antibradycardia pacing initiation before antiarrhythmic drug therapy in these patients. This recommendation has gradually broadened to encompass other antiarrhythmic agents in patients with other types of repaired congenital heart disease.

Diltiazem can provide rapid, consistent, and safe temporary ventricular rate control in children.

Antibradycardia pacing may be directly advantageous in flutter suppression by reducing the frequency of flutter-inducing pauses and premature beats. It also provides a safety factor for more aggressive antiflutter drug therapy.

Class Summary

These agents alter the electrophysiologic mechanisms responsible for arrhythmia.

Digoxin (Lanoxin)

Digoxin is a cardiac glycoside with direct inotropic effects in addition to indirect effects on the cardiovascular system. It acts directly on cardiac muscle, increasing myocardial systolic contractions. Its indirect actions result in increased carotid sinus nerve activity and enhanced sympathetic withdrawal for any given increase in mean arterial pressure.

Procainamide

Procainamide is a class IA antiarrhythmic used for premature ventricular contractions (PVCs). It increases the refractory period of the atria and ventricles. Myocardiac excitability is reduced by increase in threshold for excitation and inhibition of ectopic pacemaker activity.

Propafenone (Rythmol, Rythmol SR)

Propafenone treats life-threatening arrhythmias. It may work by reducing spontaneous automaticity and prolonging the refractory period.

Amiodarone (Cordarone, Pacerone)

Amiodarone may inhibit AV conduction and sinus node function. It prolongs the action potential and refractory period in myocardium and inhibits adrenergic stimulation. Before administration, control ventricular rate and congestive heart failure (if present) with digoxin.

Diltiazem (Cardizem, Tiazac, Dilacor XR)

Diltiazem is an AV nodal blocking agent. It is administered IV temporarily (ie, < 24 h) until definitive treatment can be initiated.

Flecainide (Tambocor)

This agent treats life-threatening ventricular arrhythmias. It causes a prolongation of refractory periods and decreases action potential without affecting duration. Flecainide blocks sodium channels, producing a dose-related decrease in intracardiac conduction in all parts of the heart with greatest effect on the His-Purkinje system (H-V conduction). Effects on AV nodal conduction time and intra-atrial conduction times, although present, are less pronounced than on ventricular conduction velocity.

Sotalol (Betapace, Betapace AF, Sorine)

Sotalol is a class III antiarrhythmic agent that blocks potassium channels, prolongs action potential duration, and lengthens the QT interval. It is a non–cardiac selective beta-adrenergic blocker.

Ibutilide (Corvert)

This newer class III antiarrhythmic agent may work by increasing action potential duration, thereby changing atrial cycle length variability. Mean time to conversion is 30 minutes. Two-thirds of patients who convert are in sinus rhythm at 24 hours. Ventricular arrhythmias may occur, mostly PVCs; torsade de pointes is a rare complication.

Dofetilide (Tikosyn)

Recently approved by FDA for maintenance of sinus rhythm, dofetilide increases monophasic action potential duration, primarily because of delayed repolarization. It terminates induced reentrant tachyarrhythmias (eg, atrial fibrillation/flutter, ventricular tachycardia) and prevents their reinduction. It does not affect cardiac output, cardiac index, stroke volume index, or systemic vascular resistance in patients with ventricular tachycardia, mild-to-moderate CHF, angina, and either normal or reduced LVEF. There is no evidence of a negative inotropic effect.

Dronedarone (Multaq)

Dronedarone is a benzofuran derivative indicated to reduce the risk of cardiovascular hospitalization in patients with paroxysmal or persistent atrial fibrillation (AF) or atrial flutter (AFL), with a recent episode of AF/AFL. It is not effective in patients with permanent atrial fibrillation. It may cause bradycardia and QT prolongation. Dronedarone is contraindicated in patients with NYHA class IV heart failure or NYHA class II and class III heart failure who had a recent decompensation. Safety and efficacy of this drug have not been confirmed in patients younger than 18 years.