INTRODUCTION — In 1930, Louis Wolff, Sir John Parkinson, and Paul Dudley White published a seminal article describing 11 patients who suffered from attacks of tachycardia associated with a sinus rhythm electrocardiographic (ECG) pattern of bundle branch block with a short PR interval [1]. This was subsequently termed the Wolff-Parkinson-White (WPW) syndrome, although earlier isolated case reports describing similar findings had already been published. In 1943, the ECG features of preexcitation were correlated with anatomic evidence for the existence of anomalous bundles of conducting tissue that bypassed all or part of the normal atrioventricular (AV) conduction system (figure 1).
AV reentrant (or reciprocating) tachycardia (AVRT) is a reentrant tachycardia with an anatomically defined circuit that consists of two distinct pathways, the normal AV conduction system and an AV accessory pathway, linked by common proximal (the atria) and distal (the ventricles) tissues. While other arrhythmias can utilize the accessory pathway for conduction from the anatomic site of tachycardia origin to other regions of the heart (eg, atrial fibrillation and atrial flutter) (figure 2), AVRT is a specific reentrant tachycardia in which the accessory pathway is necessary for initiation and maintenance of the tachycardia [2].
The different types of AVRT, along with their ECG findings, will be discussed here. The approach to treatment of arrhythmias associated with an accessory pathway is presented in detail separately. (See "Treatment of arrhythmias associated with the Wolff-Parkinson-White syndrome".)
NORMAL AV CONDUCTION VERSUS ACCESSORY AV PATHWAY CONDUCTION — Normal AV conduction occurs through the AV node. However, in the presence of an accessory pathway, conduction from the atria to the ventricles may occur in a variety of ways (exclusively via the AV node, exclusively via the accessory pathway, or a combination of both). Normal and accessory AV conduction are discussed in detail elsewhere. (See "Wolff-Parkinson-White syndrome: Anatomy, epidemiology, clinical manifestations, and diagnosis", section on 'Normal AV conduction versus accessory AV pathway conduction'.)
TACHYCARDIAS REQUIRING AN AV ACCESSORY PATHWAY FOR INITIATION AND MAINTENANCE — AVRT is a reentrant tachycardia with an anatomically defined circuit that consists of two distinct pathways, the normal AV conduction system and an AV accessory pathway, linked by common proximal (the atria) and distal (the ventricles) tissues. If sufficient differences in conduction time and refractoriness exist between the normal conduction system and the accessory pathway, a properly timed premature impulse of atrial, junctional, or ventricular origin can initiate reentry. (See "Reentry and the development of cardiac arrhythmias".)
The two major types of this arrhythmia in persons with an AV accessory pathway are narrow complex (orthodromic) and wide complex (antidromic) AVRT. The width of the QRS complex can usually distinguish between these paroxysmal arrhythmias:
●Narrow QRS complex (orthodromic AVRT) – If the tachycardia has a narrow QRS complex, the antegrade limb (ie, the pathway that conducts the supraventricular impulse to the ventricle) is the AV node/His-Purkinje system. In this setting, any preexcitation (manifest as a delta wave on the surface ECG) seen during sinus rhythm is lost since antegrade conduction is not occurring via the accessory pathway (ie, the ventricle is not preexcited) (figure 3 and waveform 1 and waveform 2). (See 'Narrow complex AVRT' below.)
●Wide QRS complex (antidromic AVRT) – If the tachycardia has a wide QRS complex, the possibilities include AVRT with antegrade conduction over the accessory pathway (antidromic AVRT) or orthodromic AVRT with aberrant QRS conduction resulting in a wide QRS complex (figure 4 and waveform 3 and waveform 4). (See 'Wide complex AVRT' below and "Left bundle branch block", section on 'Functional LBBB' and "Wide QRS complex tachycardias: Approach to the diagnosis".)
A third type of arrhythmia, permanent junctional reciprocating tachycardia, is a type of orthodromic AVRT that is typically seen in childhood. (See 'Permanent junctional reciprocating tachycardia' below.)
Narrow complex AVRT — Narrow complex (orthodromic) AVRT composes 90 to 95 percent of the reentrant tachycardias associated with the Wolff-Parkinson-White (WPW) syndrome [2,3]. Orthodromic AVRT can be initiated by atrial or ventricular premature beats (APBs or VPBs) (figure 3) [2].
●APBs initiating orthodromic AVRT are blocked in the accessory pathway but conduct antegrade to the ventricles over the AV node/His-Purkinje system. After conduction through the ventricles, the impulse then travels back to the atria in a retrograde fashion via the AV accessory pathway to complete the first reentrant loop.
●VPBs initiating orthodromic AVRT are blocked in the AV node/His-Purkinje system but conduct retrograde to the atria over the accessory pathway. After conduction through the atria, the impulse then travels back to the ventricles in an antegrade fashion via the normal AV conduction system to complete the reentrant circuit [2,4].
ECG findings in orthodromic AVRT — The ECG during orthodromic AVRT (waveform 1 and waveform 2) typically shows the following:
●Ventricular rate ranging from 150 to 250 (or greater) beats per minute and usually regular.
●Narrow QRS complexes (in the absence of underlying conduction system disease or in the absence of aberrancy).
●Inverted P waves with an RP interval that is usually less than one-half the tachycardia RR interval. (See "Narrow QRS complex tachycardias: Clinical manifestations, diagnosis, and evaluation", section on 'RP relationship'.)
●Constant RP interval regardless of the tachycardia cycle length [5].
Beat-to-beat oscillation in QRS amplitude (QRS alternans) sometimes occurs during orthodromic AVRT and is most commonly seen when the rate is very rapid [6,7]. The mechanism for QRS alternans is not clear but may in part result from oscillations in the relative refractory period of the AV node-His-Purkinje system [8,9].
Ischemic-appearing ST segment depression also can occur during orthodromic AVRT, even in young individuals who are unlikely to have coronary artery disease [10]. Several factors may contribute to the ST segment depression in these arrhythmias, including changes in autonomic nervous system tone, intraventricular conduction disturbances, a longer ventriculoatrial interval, and a retrograde P wave of longer duration that overlaps into the ST segment [11]. The location of the ST segment changes may vary with the location of the accessory pathway [12,13].
Wide complex AVRT — Wide complex (antidromic) AVRT is the least common arrhythmia associated with WPW syndrome, occurring in less than 10 percent of patients [2]. In a retrospective observational study of 807 patients (age range 5 to 85 years) with preexcitation on a surface ECG who also underwent invasive electrophysiologic studies (EPS), 63 patients (8 percent) were found to have inducible antidromic AVRT during EPS (compared with 55 percent rate of inducible orthodromic AVRT in the same population) [14]. In another retrospective study of 1147 pediatric patients (age less than 21 years) who underwent invasive EPS, antidromic AVRT was identified in only 30 patients (3 percent), with the accessory pathways in these patients having rapid anterograde conduction characteristics [15].
As with orthodromic AVRT, antidromic AVRT can be initiated by atrial or ventricular premature beats (APBs or VPBs) (figure 4) [2].
●APBs initiating antidromic AVRT are blocked in the AV node/His-Purkinje system but conduct antegrade to the ventricles over the accessory pathway. After conduction through the ventricles, the impulse then travels back to the atria in a retrograde fashion via the AV node/His-Purkinje system to complete the first reentrant loop.
●VPBs initiating antidromic AVRT are blocked in the accessory pathway but conduct retrograde to the atria over the AV node/His-Purkinje system. After conduction through the atria, the impulse then travels back to the ventricles in an antegrade fashion via the accessory pathway to complete the reentrant circuit.
An unusual type of antidromic reentry can also occur in patients with an atriofascicular fiber (sometimes referred to as a Mahaim fiber) that can be difficult to distinguish from antidromic reentry using a conventional AV accessory pathway reentry in the acute setting. (See "Atriofascicular ("Mahaim") pathway tachycardia".)
ECG findings in antidromic AVRT — The ECG during antidromic AVRT (figure 4 and waveform 3 and waveform 4) typically shows the following:
●Ventricular rate ranging from 150 to 250 (or greater) beats per minute and usually regular.
●Wide QRS complexes which are fully preexcited.
●Inverted P waves with an RP interval that is usually more than one-half the tachycardia RR interval and a short PR interval. (See "Narrow QRS complex tachycardias: Clinical manifestations, diagnosis, and evaluation", section on 'RP relationship'.)
●Constant RP interval regardless of the tachycardia cycle length [5].
Susceptibility to antidromic AVRT also appears to be dependent upon a transverse distance of at least 4 cm between the bypass tract and the normal AV conduction system. Consequently, most antidromic AVRTs use a left-sided accessory pathway as the antegrade route for conduction [2,5].
In some patients with antidromic AVRT and a left-sided accessory pathway, preexcitation may not be apparent in sinus rhythm because the time for the atrial impulse to reach the atrial insertion of the accessory pathway is longer than the time to reach the AV node (waveform 5).
A rare variant of antidromic AVRT can occur in patients with multiple accessory pathways when anterograde conduction occurs over one accessory pathways and retrograde conduction returns to the atrium via a second accessory pathway. In such cases, the AV node is not necessary for maintenance of reentry. The ECG during pathway-pathway tachycardia is indistinguishable from conventional antidromic AVRT, and confirmation of the precise circuit usually requires mapping at electrophysiology study. Approximately 10 percent of patients undergoing catheter ablation can be found to have multiple accessory pathways [16].
Permanent junctional reciprocating tachycardia — Permanent or incessant junctional reciprocating (or reentrant) tachycardia (PJRT) is a type of orthodromic AVRT that most often occurs in early childhood, although clinically asymptomatic patients presenting later in life are not uncommon. In the older patient, PJRT tends to be less incessant, perhaps due to variable autonomic tone, and has a somewhat slower ventricular rate, felt to be the result of a prolongation of retrograde conduction through the accessory pathway [17]. The heart rate is usually between 120 and 200 beats/minute, and the QRS duration is generally normal (waveform 6).
Chronic suppression of PJRT is usually not possible with drugs, and ablation of the accessory pathway is often necessary to achieve arrhythmia control [3,18-20]. The incessant nature of PJRT may result in dilated cardiomyopathy and heart failure; these changes are potentially reversible if the accessory pathway can be successfully ablated [3,17,18,21]. (See "Clinical features and diagnosis of supraventricular tachycardia (SVT) in children", section on 'Permanent junctional reciprocating tachycardia' and "Arrhythmia-induced cardiomyopathy" and "Treatment of arrhythmias associated with the Wolff-Parkinson-White syndrome", section on 'Catheter ablation'.)
ECG findings in PJRT — PJRT is an orthodromic AVRT mediated by a concealed, retrogradely conducting AV accessory pathway that has slow and decremental conduction properties [19,22,23]. Because of this, PJRT has similar ECG findings as seen in typical orthodromic AVRT. (See 'ECG findings in orthodromic AVRT' above.)
Nevertheless, one major ECG difference is seen between PJRT and typical orthodromic AVRT. The retrograde conduction properties of the accessory pathway in PJRT are slower compared with both the anterograde conduction properties of the AV node and the usual "fast" accessory pathways found in patients with AVRT [17]. Therefore, slow retrograde conduction over the accessory pathway causes the RP interval during PJRT to be long, usually more than one-half the tachycardia RR interval.
The accessory pathway in patients with PJRT is most often located within the posteroseptal region, although other portions of the AV groove may also harbor this unique pathway [19,20,23,24]. P waves resulting from retrograde conduction are easily seen on the ECG and are inverted in leads 2, 3, aVF, and V3 to V6.
CLINICAL MANIFESTATIONS OF AVRT AND PJRT — The response to a rapid heart rate can be quite variable depending on how fast the heart is beating, resultant blood pressure and tissue perfusion, underlying comorbidities, and the sensitivity of the individual patient to the symptoms. Patients with AV reentrant (or reciprocating) tachycardia (AVRT) or permanent junctional reciprocating (or reentrant) tachycardia (PJRT) can present with a variety of symptoms, including:
●Palpitations
●Syncope or presyncope
●Lightheadedness or dizziness
●Diaphoresis
●Chest pain
●Shortness of breath
Most commonly, patients with AVRT present with palpitations, the sensation of a rapid or irregular heart beat felt in the anterior chest or neck. Because of the persistent nature and the rapid ventricular heart rate associated with PJRT, some patients with PJRT may present with findings of impaired left ventricular function compatible with a tachycardia-mediated cardiomyopathy. The presenting symptoms of tachycardias and tachycardia-mediated cardiomyopathy are discussed in greater detail separately. (See "Evaluation of palpitations in adults" and "Narrow QRS complex tachycardias: Clinical manifestations, diagnosis, and evaluation", section on 'Clinical manifestations' and "Arrhythmia-induced cardiomyopathy".)
DIAGNOSIS OF AVRT AND PJRT — The diagnosis of AV reentrant (or reciprocating) tachycardia (AVRT) or permanent junctional reciprocating (or reentrant) tachycardia (PJRT) typically requires only a surface electrocardiogram (ECG) which shows a heart rate greater than 100 beats per minute along with regularly occurring QRS complexes. An old ECG performed when the patient is not having a tachycardia can be helpful for identifying the presence of a delta wave suggesting preexcitation and an accessory pathway. Once a QRS complex width has been identified, further scrutiny of the ECG is required to identify the specific arrhythmia in a particular patient, as diagnostic evaluation and therapy will differ depending on the underlying arrhythmia (algorithm 1). (See 'ECG findings in orthodromic AVRT' above and 'ECG findings in antidromic AVRT' above and 'ECG findings in PJRT' above and "Narrow QRS complex tachycardias: Clinical manifestations, diagnosis, and evaluation", section on 'Evaluation'.)
Invasive electrophysiology testing is usually not required to broadly make the diagnosis of AVRT or PJRT, but on rare occasions it is needed to diagnose (and potentially treat with catheter ablation) the specific arrhythmia. (See "Narrow QRS complex tachycardias: Clinical manifestations, diagnosis, and evaluation", section on 'Electrophysiologic testing'.)
DIFFERENTIAL DIAGNOSIS — The differential diagnosis for patients with orthodromic AV reentrant (or reciprocating) tachycardia (AVRT) or permanent junctional reciprocating (or reentrant) tachycardia (PJRT) and a narrow QRS complex (<120 msec duration) includes other supraventricular tachyarrhythmias with regularly occurring, narrow QRS complexes (algorithm 1). This differential diagnosis is discussed in greater detail separately. (See "Narrow QRS complex tachycardias: Clinical manifestations, diagnosis, and evaluation", section on 'Types of narrow QRS complex tachycardia' and "Atrioventricular nodal reentrant tachycardia".)
For patients with a wide QRS complex tachycardia (ie, those with antidromic AVRT; or those with orthodromic AVRT or PJRT and underlying conduction system disease), ventricular tachycardia should be a part of the differential diagnosis along with aberrantly conducted supraventricular tachyarrhythmias (eg, focal atrial tachycardia and AV nodal reentry tachycardia). This differential diagnosis is discussed in greater detail separately. (See "Wide QRS complex tachycardias: Causes, epidemiology, and clinical manifestations", section on 'Differential diagnosis of WCT'.)
TREATMENT OF AVRT AND PJRT — The approaches to both acute and chronic treatment of AV reentrant (or reciprocating) tachycardia or permanent junctional reciprocating (or reentrant) tachycardia are discussed separately. (See "Treatment of arrhythmias associated with the Wolff-Parkinson-White syndrome" and "Overview of the acute management of tachyarrhythmias", section on 'Regular narrow QRS complex tachyarrhythmias'.)
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 adults" and "Society guideline links: Catheter ablation of arrhythmias" and "Society guideline links: Supraventricular arrhythmias".)
SUMMARY AND RECOMMENDATIONS
●Atrioventricular reentrant (or reciprocating) tachycardia (AVRT) is a reentrant tachycardia with an anatomically defined circuit that consists of two distinct pathways, the normal AV conduction system and an AV accessory pathway (figure 1), linked by common proximal (the atria) and distal (the ventricles) tissues. (See 'Introduction' above.)
●The two major types of this arrhythmia in persons with an AV accessory pathway are orthodromic AVRT (including permanent junctional reciprocating tachycardia [PJRT]) and antidromic AVRT.
•Narrow complex (orthodromic) AVRT composes 90 to 95 percent of the reentrant tachycardias associated with the Wolff-Parkinson-White (WPW) syndrome. The ECG during orthodromic AVRT (waveform 1 and waveform 2) typically shows a regular ventricular rate ranging from 150 to 250 (or greater) beats per minute, narrow QRS complexes, inverted P waves with an RP interval that is usually less than one-half the tachycardia RR interval, and a constant RP interval. (See 'Narrow complex AVRT' above and 'ECG findings in orthodromic AVRT' above.)
•Wide complex (antidromic) AVRT is the least common arrhythmia associated with WPW syndrome, occurring in only 5 to 10 percent of patients. The ECG during antidromic AVRT (figure 4 and waveform 3 and waveform 4) typically shows a regular ventricular rate ranging from 150 to 250 (or greater) beats per minute, wide QRS complexes, inverted P waves with an RP interval that is usually more than one-half the tachycardia RR interval, and a constant RP interval. (See 'Wide complex AVRT' above and 'ECG findings in antidromic AVRT' above.)
•PJRT is a narrow complex (orthodromic) AVRT most often occurring in early childhood. PJRT has similar ECG findings as seen in typical orthodromic AVRT with one major difference; slow retrograde conduction over the accessory pathway causes the RP interval during PJRT to be long, usually more than one-half the tachycardia RR interval. (See 'Permanent junctional reciprocating tachycardia' above and 'ECG findings in PJRT' above.)
●Most commonly, patients with AVRT present with palpitations, the sensation of a rapid or irregular heart beat felt in the anterior chest or neck. Because of the persistent nature and the rapid ventricular heart rate associated with PJRT, some patients with PJRT may present with findings of impaired left ventricular function compatible with a tachycardia-mediated cardiomyopathy. (See 'Clinical manifestations of AVRT and PJRT' above.)
●The diagnosis of AVRT or PJRT typically requires only a surface electrocardiogram (ECG) which shows a heart rate greater than 100 beats per minute along with regularly occurring QRS complexes. An old ECG performed when the patient is not having a tachycardia can be helpful for identifying the presence of a delta wave suggesting preexcitation and an accessory pathway. Once a narrow QRS complex tachycardia has been identified, further scrutiny of the ECG is required to identify the specific arrhythmia in a particular patient. (See 'Diagnosis of AVRT and PJRT' above.)
●The differential diagnosis and approach to treatment for AVRT and PJRT are discussed in greater detail separately. (See "Treatment of arrhythmias associated with the Wolff-Parkinson-White syndrome" and "Narrow QRS complex tachycardias: Clinical manifestations, diagnosis, and evaluation", section on 'Types of narrow QRS complex tachycardia'.)
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