Atrial ectopic tachycardia (AET) is a rare arrhythmia; however, it is the most common form of incessant supraventricular tachycardia (SVT) in children. Atrial ectopic tachycardia is believed to be secondary to increased automaticity of a nonsinus atrial focus or foci. This arrhythmia, which is also known as ectopic atrial tachycardia or automatic atrial tachycardia, has a high association with tachycardia-induced cardiomyopathy. Atrial ectopic tachycardia is often refractory to medical therapy and is not usually responsive to direct current (DC) cardioversion.
The diagnosis of atrial ectopic tachycardia is based on the presence of a narrow complex tachycardia (in the absence of aberrancy or preexisting bundle branch block) with visible P waves at an inappropriately rapid rate. The rates range from 120 to 300 beats per minute (bpm) and are typically higher than 200 bpm, although physiologic rates may be observed (see Electrocardiography).
Patients with atrial ectopic tachycardia may present with circulat ory collapse similar to patients with cardiomyopathy. Immediate rate control is desired in these cases. Three options are available for long-term treatment of patients with atrial ectopic tachycardia: medication to suppress the arrhythmia or control the ventricular response, catheter ablation, or, uncommonly, surgery (see Treatment and Management).
Go to Atrial Tachycardia and Multifocal Atrial Tachycardia for information on these topics.
Spontaneous depolarization is a phenomenon of automatic myocardium. The sinus node is usually the pacemaker of the heart, because it has the most rapid spontaneous rate of firing. A small cluster of cells with abnormal automaticity is presumed to be responsible for atrial ectopic tachycardia. The conduction spreads from this cluster to the surrounding atrium and to the ventricles via the atrioventricular (AV) node. A conduction delay from atrium to ventricle often occurs, with most patients demonstrating first-degree AV block and some showing second-degree block.
Because atrial ectopic tachycardia is often incessant, tachycardia-induced cardiomyopathy is commonly observed. Although the exact underlying mechanism of the development of cardiac dysfunction in the setting of chronic arrhythmias is unknown, numerous reports have documented improved cardiac function following ventricular rate control and treatment of the arrhythmia.
Atrial ectopic tachycardia is usually idiopathic. Occasionally, mycoplasmal or viral infections, such as respiratory syncytial virus, may trigger this arrhythmia, although more complex atrial tachycardias, such as chaotic atrial tachycardia, are more frequently found in this scenario. Atrial tumors have been reported to be associated with atrial ectopic tachycardia. Reports of familial cases with an autosomal dominant inheritance are present in the literature.[1] This arrhythmia is also observed in patients who have congenital heart disease and have undergone surgical treatment of this congenital heart disease.
The adult form of atrial ectopic tachycardia may have a different etiology and natural history than the pediatric form.
Although the exact incidence is unknown and few large series have been reported, atrial ectopic tachycardia reportedly comprises 5-10% of pediatric SVTs. Although estimates of the incidence of pediatric SVTs widely vary, atrial ectopic tachycardia likely occurs with an incidence of approximately 1 case per 10,000 children.
Atrial ectopic tachycardia is predominantly observed in infants and children; this accounts for a peak of 11-16% of tachycardias for which a mechanism is determined in young childhood.
Atrial ectopic tachycardia is generally well tolerated. Syncope is unusual, and cardiac arrest is rare, except when encountered as a complication of treatment. Tachycardia-induced cardiomyopathy is the most significant sequela of atrial ectopic tachycardia and may be insidious. The time to development depends on the rate and duration of the tachycardia; however, ventricular dilatation may be present on initial presentation. This can also be reversed with successful treatment of the arrhythmia.
Several reports have documented the spontaneous remission of atrial ectopic tachycardia in the pediatric population and in young adults.[2] This may occur in as many as one third of patients following withdrawal of medication. A review from Texas Children's Hospital suggests that children younger than 3 years have a better response to medication and a higher rate of spontaneous resolution of the arrhythmia.[3]
For patient education information, see the Heart Health Center, as well as Supraventricular Tachycardia.
Although atrial ectopic tachycardia (AET) is occasionally encountered in patients following surgery for congenital heart disease, most patients have structurally normal hearts and are symptomatic. Palpitations, chest pain, lightheadedness, presyncope, and dyspnea are the most common symptoms.
Asymptomatic or preverbal patients may be noted to be tachycardic or dyspneic on routine evaluation. Difficulty feeding or diaphoresis may accompany the tachycardia in infants.
Exercise intolerance and heart failure are late manifestations of secondary cardiac dysfunction.
The history must be sufficiently broad to rule out causes of persistently elevated heart rates, such as hyperthyroidism, anemia, or catecholamine-producing malignancy. The family history is rarely positive for atrial ectopic tachycardia.
The heart rate is inappropriately elevated for the degree of activity. If second-degree atrioventricular (AV) block is present, the heart rate may be irregular. The patient may be tachypneic. In advanced cardiomyopathy, pulses and perfusion are poor, and evidence of cardiac enlargement is present. Hepatic and pulmonary congestion may be present.
During the arrhythmia in stable patients, 12-lead electrocardiography (ECG) is necessary. Laboratory testing is indicated for the exclusion of underlying systemic disorders. Echocardiography and Holter monitoring are also part of the standard workup. Electrophysiology testing may be useful in some patients. Exercise testing may occasionally unmask an intermittent atrial ectopic tachycardia (AET).
Go to Atrial Tachycardia and Multifocal Atrial Tachycardia for information on these topics.
Assess electrolyte levels, hematocrit levels, and thyroid function in patients with atrial ectopic tachycardia.
Also consider thyroid studies, as well as urine collections in some patients for assessment of possible pheochromocytoma.
Inspect the electrocardiogram (ECG) for P-wave axis and morphology, ventricular rate, and conduction block.
The diagnosis of atrial ectopic tachycardia is based on the presence of a narrow complex tachycardia (in the absence of aberrancy or preexisting bundle branch block) with visible P waves at an inappropriately rapid rate. The rates range from 120 to 300 beats per minute (bpm) and are typically higher than 200 bpm, although physiologic rates may be observed.
The P-wave axis is usually abnormal, although a focus near the sinus node can be mistaken for sinus tachycardia. Similarly, the P-wave morphology may be abnormal. Onset of the tachycardia occurs with a P wave identical to the subsequent P waves. The tachycardia may exhibit a "warming up," which refers to a progressively shortening P-P interval for the first few beats of the arrhythmia. Similarly, a "cooling down" may be observed at its termination. First-degree atrioventricular (AV) block is typical and second-degree AV block is common. The tachycardia cycle length and degree of AV block are influenced by the autonomic tone.
Ectopic atrial tachycardia usually creates a P wave that is at least slightly different from sinus rhythm, first-degree atrioventricular (AV) block, and possible periods of second-degree AV block without termination of tachycardia.
To differentiate atrial ectopic tachycardia from sinus tachycardia secondary to cardiomyopathy, Gelb and Garson demonstrated that negative late terminal P-wave forces in lead V2 occur more commonly in atrial ectopic tachycardia.[4] The rate is also usually higher in atrial ectopic tachycardia.
Algorithms to determine the site of the ectopic focus based on P-wave morphology are known. A negative or biphasic (positive, then negative) P wave in lead V1 indicated a right atrial tachycardia. A positive or biphasic (negative, then positive) P wave in ECG lead V1 indicated a left atrial tachycardia.[5]
Patients should undergo Holter monitoring to determine the time spent in tachycardia and the ventricular rates. Holter monitoring is particularly useful in identifying and analyzing onsets and offsets of tachycardia.
The Holter monitor findings often facilitate the diagnosis by revealing: (1) an elevated average heart rate over a 24-hour period, with reduced circadian variability; (2) a higher peak heart rate than normally encountered in sinus rhythm; or (3) periods of atrioventricular (AV) block, demonstrating 2 consecutive P waves at an elevated rate without an intervening QRS complex.
Perform echocardiography with a focus on cardiac function and dimensions to rule out cardiomyopathy and associated congenital heart disease.[6] The earliest manifestation of cardiomyopathy may be ventricular dilatation. A decreased shortening fraction follows. Reversal of these findings after treatment follows a reciprocal pattern. Diastolic function abnormalities may also occur in tachycardia-induced cardiomyopathy, and they may be the last parameter to correct after therapy.
Atrial angiography may occasionally be helpful as a roadmap during radiofrequency (RF) catheter ablation.
Although invasive studies are not usually necessary to make a diagnosis of atrial ectopic tachycardia, in some patients, an esophageal electrophysiology recording may be useful to assist confirmation of the diagnosis; the response to overdrive pacing can also be assessed. Many automatic foci transiently suppress when overdrive pacing is performed.
An invasive electrophysiology study can also be performed for these indications, but this is usually performed in patients undergoing attempt at radiofrequency (RF) ablation.
In patients with ectopic atrial tachycardias arising from the pulmonary veins, an esophageal recording may also be helpful in localizing the site of tachycardia.
The response of atrial ectopic tachycardia to adenosine may be persistent in the setting of atrioventricular (AV) block or a transient slowing of the tachycardia; it rarely terminates. Direct current (DC) cardioversion usually does not terminate the arrhythmia.
Endomyocardial biopsy findings often reveal vacuolized myocytes in the setting of tachycardia-induced cardiomyopathy.
Acute atrial ectopic tachycardia (AET) may be a medical emergency, requiring immediate rate control. More frequently, patients are evaluated in the clinical setting, and hospitalization is often only necessary for initiation of certain antiarrhythmic medications. Although surgical cryoablation has previously been used to treat patients with atrial ectopic tachycardia, this has been primarily supplanted by catheter radiofrequency (RF) ablation techniques.
Go to Atrial Tachycardia and Multifocal Atrial Tachycardia for information on these topics.
For patients who present in cardiac arrest or with hemodynamic compromise, establish the circulation, airway, and breathing, the CABs, as is standard; provide appropriate monitoring; make sure that a defibrillator is available; and attempt conversion with a defibrillator if necessary.
Patients with atrial ectopic tachycardia (AET) may present with circulatory collapse similar to patients with cardiomyopathy. Although these patients may benefit from afterload reduction and inotropy, primary therapy aimed at reversing their tachycardia is usually more successful.
Immediate rate control is desired in the child who requires significant support, including intubation, in the intensive care unit (ICU). This can often be achieved without resorting to negatively inotropic antiarrhythmic agents. Digitalization and the use of intravenous (IV) amiodarone may quickly achieve rate control. An additional maneuver involves the use of atrial pacing (eg, esophageal, transthoracic, transvenous) to overdrive the atrial tachycardia to a point of consistent 2:1 atrioventricular (AV) block, thus lowering the ventricular response rate. In the era of radiofrequency (RF) ablation, most patients who require this degree of support undergo an attempt at ablation of the focus, particularly if it is an incessant tachycardia. The use of inotropic agents such as epinephrine may increase the tachycardia rate and cause clinical deterioration.
Three options are available for treatment of patients with atrial ectopic tachycardia (AET), including medication to suppress the arrhythmia or control the ventricular response, surgery, or radiofrequency (RF) ablation.
Long-term oral medication is the mainstay of therapy in patients not undergoing RF ablation. Class IC and III antiarrhythmic agents are generally the most effective, and a staged approach is recommended. Medical therapy may be effective in as many as 75% of patients, but more than one medication is usually needed.
Radiofrequency (RF) ablation can be curative for atrial ectopic tachycardia and can be performed with a high degree of success, a low complication rate, and a low recurrence rate. Success rates range from 75-100%. The complication rates are similar to other RF ablation procedures, with a higher risk of recurrence. The encircling technique uses 2 catheters capable of delivering RF energy as mapping catheters, alternating the reference and roving catheters, until no site provides an earlier signal than the reference. This early reference catheter is then used to deliver ablation. Atrial angiography may occasionally be helpful as a roadmap during RF catheter ablation.
Noncontact mapping systems have gained an increasing role in the ablation of atrial ectopic tachycardia.[7, 8] The ability to localize the focus, including a nonsustained focus, with accuracy is an advantage of this technique. A limitation in the pediatric population is the size of the equipment and duration of the procedures. Cummings et al reported better results using a 3-dimensional mapping system than with conventional mapping in a series of 16 patients who underwent ablation.[9]
Atrial ectopic tachycardia (AET) is one of the incessant tachycardias, which may become associated with myocardial dysfunction if the average ventricular rate remains elevated over a long term.
Historically, patients have been advised to avoid caffeine and chocolate. The role of these dietary elements must be assessed in the individual patient; most cases are not related to these dietary elements.
Patients with atrial ectopic tachycardia (AET) should be monitored by a cardiologist.
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 while the guidelines are intended for adults (≥18 years of age) and offers no specific recommendations for pediatric patients, in some cases, the data from noninfant pediatric patients was reviewed and helped inform the guideline.[10]
The guidelines state that pharmacological therapy is largely based on practice patterns because random controlled trials (RCTs) of antiarrhythmic medications in children are lacking. Amiodarone, sotalol, propafenone, or flecainide can 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 medication in children because of the rare occurrence of adverse events. Catheter ablation can be successfully performed in children of all ages, with success rates comparable to those reported in adults.[10]
Drugs with some effect in atrial ectopic tachycardia (AET) include digoxin (used predominantly for rate control), amiodarone, propafenone, flecainide, sotalol, procainamide, and esmolol.[11] Only digoxin and oral amiodarone are devoid of negative inotropic effect. Adequate control may not require the complete abolition of all atrial ectopic beats or runs.
Clinical Context: Digoxin is a cardiac glycoside with direct inotropic effects in addition to indirect effects on the cardiovascular system. This agent acts directly on cardiac muscle, increasing myocardial systolic contractions, and its indirect actions result in increased carotid sinus nerve activity and enhanced sympathetic withdrawal for any given increase in mean arterial pressure. Digoxin is used to control ventricular rate when administering propafenone, flecainide, or procainamide.
Clinical Context: Amiodarone is a class III antiarrhythmic that may inhibit atrioventricular (AV) conduction and sinus node function. This agent prolongs action potential and refractory period in the myocardium and inhibits adrenergic stimulation. Before administrating amiodarone, control the ventricular rate and congestive heart failure (CHF), if present, with digoxin.
Clinical Context: Esmolol is a class II antiarrhythmic that is an excellent drug for use in patients at risk of complications from beta blockade, particularly for those with reactive airway disease, mild-to-moderate left ventricular (LV) dysfunction, and/or peripheral vascular disease. This drug has a short half-life of 8 min, which allows for titration to the desired effect and quick discontinuation if needed.
Clinical Context: Sotalol is a class III antiarrhythmic agent that blocks potassium channels, prolongs action potential duration, and and lengthens the QT interval. It is a noncardiac selective beta-adrenergic blocker.
Clinical Context: Propafenone is a class IC antiarrhythmic that has local anesthetic properties; it inhibits the fast sodium channels of the myocardial cell membrane and slows the rate of increase of the action potential. This drug treats life-threatening arrhythmias and possibly works by reducing spontaneous automaticity and prolonging the refractory period.
Clinical Context: Flecainide is a class IC antiarrhythmic agent that is used to treat life-threatening ventricular arrhythmias by causing a prolongation of refractory periods and decreasing action potential without affecting duration. This agent 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). However, its effects on AV nodal conduction time and intra-atrial conduction times, although present, are less pronounced than on ventricular conduction velocity.
Clinical Context: Procainamide is a class IA antiarrhythmic used for premature ventricular contractions (PVCs), ventricular tachycardias (VTs), and supraventricular tachycardias (SVTs). This drug increases the refractory period of the atria and ventricles. Myocardiac excitability is reduced by an increase in the threshold for excitation and inhibition of ectopic pacemaker activity.
These agents alter the electrophysiologic mechanisms responsible for arrhythmia.