7/6/23, 11:12 AM Atrioventricular reentrant tachycardia (AVRT) associated with an accessory pathway - UpToDate Official reprint from UpToDate www.uptodate.com 2023 UpToDate, Inc. and/or its affiliates. All Rights Reserved. Atrioventricular reentrant tachycardia (AVRT) associated with an accessory pathway : Luigi Di Biase, MD, PhD, FHRS, FACC, Edward P Walsh, MD : Samuel L vy, MD, Bradley P Knight, MD, FACC : Susan B Yeon, MD, JD, FACC All topics are updated as new evidence becomes available and our peer review process is complete. Literature review current through: Jun 2023. This topic last updated: Aug 26, 2022. 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 https://www.uptodate.com/contents/atrioventricular-reentrant-tachycardia-avrt-associated-with-an-accessory-pathway/print 1/26 7/6/23, 11:12 AM Atrioventricular reentrant tachycardia (AVRT) associated with an accessory pathway - UpToDate 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 https://www.uptodate.com/contents/atrioventricular-reentrant-tachycardia-avrt-associated-with-an-accessory-pathway/print 2/26 7/6/23, 11:12 AM Atrioventricular reentrant tachycardia (AVRT) associated with an accessory pathway - UpToDate 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]. https://www.uptodate.com/contents/atrioventricular-reentrant-tachycardia-avrt-associated-with-an-accessory-pathway/print 3/26 7/6/23, 11:12 AM Atrioventricular reentrant tachycardia (AVRT) associated with an accessory pathway - UpToDate 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. https://www.uptodate.com/contents/atrioventricular-reentrant-tachycardia-avrt-associated-with-an-accessory-pathway/print 4/26 7/6/23, 11:12 AM Atrioventricular reentrant tachycardia (AVRT) associated with an accessory pathway - UpToDate 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'.) https://www.uptodate.com/contents/atrioventricular-reentrant-tachycardia-avrt-associated-with-an-accessory-pathway/print 5/26 7/6/23, 11:12 AM Atrioventricular reentrant tachycardia (AVRT) associated with an accessory pathway - UpToDate 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 https://www.uptodate.com/contents/atrioventricular-reentrant-tachycardia-avrt-associated-with-an-accessory-pathway/print 6/26 7/6/23, 11:12 AM Atrioventricular reentrant tachycardia (AVRT) associated with an accessory pathway - UpToDate 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 https://www.uptodate.com/contents/atrioventricular-reentrant-tachycardia-avrt-associated-with-an-accessory-pathway/print 7/26 7/6/23, 11:12 AM Atrioventricular reentrant tachycardia (AVRT) associated with an accessory pathway - UpToDate 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.) https://www.uptodate.com/contents/atrioventricular-reentrant-tachycardia-avrt-associated-with-an-accessory-pathway/print 8/26 7/6/23, 11:12 AM Atrioventricular reentrant tachycardia (AVRT) associated with an accessory pathway - UpToDate 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'.) Use of UpToDate is subject to the Terms of Use. REFERENCES https://www.uptodate.com/contents/atrioventricular-reentrant-tachycardia-avrt-associated-with-an-accessory-pathway/print 9/26 7/6/23, 11:12 AM Atrioventricular reentrant tachycardia (AVRT) associated with an accessory pathway - UpToDate 1. Wolff L, Parkinson J, White PD. Bundle-branch block with short P-R interval in healthy young people prone to paroxysmal tachycardia. 1930. Ann Noninvasive Electrocardiol 2006; 11:340. 2. Josephson ME. Preexcitation syndromes. In: Clinical Cardiac Electrophysiology, 4th, Lippinco t Williams & Wilkins, Philadelphia 2008. p.339. 3. Chugh A, Morady F. Atrioventricular reentry and variants. In: Cardiac electrophysiology from cell to bedside, 5th edition, Zipes DP, Jalife J (Eds), Saunders/Elsevier, Philadelphia 2009. p.60 5-614. 4. Akhtar M, Lehmann MH, Denker ST, et al. Electrophysiologic mechanisms of orthodromic tachycardia initiation during ventricular pacing in the Wolff-Parkinson-White syndrome. J Am Coll Cardiol 1987; 9:89. 5. Cain ME, Luke RA, Lindsay BD. Diagnosis and localization of accessory pathways. Pacing Clin Electrophysiol 1992; 15:801. 6. Green M, Heddle B, Dassen W, et al. Value of QRS alteration in determining the site of origin of narrow QRS supraventricular tachycardia. Circulation 1983; 68:368. 7. Kay GN, Pressley JC, Packer DL, et al. Value of the 12-lead electrocardiogram in discriminating atrioventricular nodal reciprocating tachycardia from circus movement atrioventricular tachycardia utilizing a retrograde accessory pathway. Am J Cardiol 1987; 59:296. 8. Tchou PJ, Lehmann MH, Dongas J, et al. Effect of sudden rate acceleration on the human His-Purkinje system: adaptation of refractoriness in a dampened oscillatory pattern. Circulation 1986; 73:920. 9. Gallagher JJ, Sealy WC, Kasell J, Wallace AG. Multiple accessory pathways in patients with the pre-excitation syndrome. Circulation 1976; 54:571. 10. Man KC, Brinkman K, Bogun F, et al. 2:1 atrioventricular block during atrioventricular node reentrant tachycardia. J Am Coll Cardiol 1996; 28:1770. 11. Nelson SD, Kou WH, Annesley T, et al. Significance of ST segment depression during paroxysmal supraventricular tachycardia. J Am Coll Cardiol 1988; 12:383. 12. Riva SI, Della Bella P, Fassini G, et al. Value of analysis of ST segment changes during tachycardia in determining type of narrow QRS complex tachycardia. J Am Coll Cardiol 1996; 27:1480. 13. Scheinman MM, Wang YS, Van Hare GF, Lesh MD. Electrocardiographic and electrophysiologic characteristics of anterior, midseptal and right anterior free wall accessory pathways. J Am Coll Cardiol 1992; 20:1220. https://www.uptodate.com/contents/atrioventricular-reentrant-tachycardia-avrt-associated-with-an-accessory-pathway/print 10/26 7/6/23, 11:12 AM Atrioventricular reentrant tachycardia (AVRT) associated with an accessory pathway - UpToDate 14. Brembilla-Perrot B, Pauriah M, Sellal JM, et al. Incidence and prognostic significance of spontaneous and inducible antidromic tachycardia. Europace 2013; 15:871. 15. Ceresnak SR, Tanel RE, Pass RH, et al. Clinical and electrophysiologic characteristics of antidromic tachycardia in children with Wolff-Parkinson-White syndrome. Pacing Clin Electrophysiol 2012; 35:480. 16. Zachariah JP, Walsh EP, Triedman JK, et al. Multiple accessory pathways in the young: the impact of structural heart disease. Am Heart J 2013; 165:87. 17. Dorostkar PC, Silka MJ, Morady F, Dick M 2nd. Clinical course of persistent junctional reciprocating tachycardia. J Am Coll Cardiol 1999; 33:366. 18. Aguinaga L, Primo J, Anguera I, et al. Long-term follow-up in patients with the permanent form of junctional reciprocating tachycardia treated with radiofrequency ablation. Pacing Clin Electrophysiol 1998; 21:2073. 19. Guarnieri T, Sealy WC, Kasell JH, et al. The nonpharmacologic management of the permanent form of junctional reciprocating tachycardia. Circulation 1984; 69:269. 20. Ticho BS, Saul JP, Hulse JE, et al. Variable location of accessory pathways associated with the permanent form of junctional reciprocating tachycardia and confirmation with radiofrequency ablation. Am J Cardiol 1992; 70:1559. 21. Packer DL, Bardy GH, Worley SJ, et al. Tachycardia-induced cardiomyopathy: a reversible form of left ventricular dysfunction. Am J Cardiol 1986; 57:563. 22. Brugada P, Vanagt EJ, Bar FW, Wellens HJ. Incessant reciprocating atrioventricular tachycardia. Factors playing a role in the mechanism of the arrhythmia. Pacing Clin Electrophysiol 1980; 3:670. 23. Critelli G, Gallagher JJ, Monda V, et al. Anatomic and electrophysiologic substrate of the permanent form of junctional reciprocating tachycardia. J Am Coll Cardiol 1984; 4:601. 24. Okumura K, Henthorn RW, Epstein AE, et al. "Incessant" atrioventricular (AV) reciprocating tachycardia utilizing left lateral AV bypass pathway with a long retrograde conduction time. Pacing Clin Electrophysiol 1986; 9:332. Topic 976 Version 28.0 https://www.uptodate.com/contents/atrioventricular-reentrant-tachycardia-avrt-associated-with-an-accessory-pathway/print 11/26 7/6/23, 11:12 AM Atrioventricular reentrant tachycardia (AVRT) associated with an accessory pathway - UpToDate GRAPHICS Types of accessory pathways Diagram of 4 types of abnormal conduction pathways: classic accessory atrioventricular pathway (red), atriofascicular pathway (green), fasciculoventricular pathway (light blue), and nodoventricular pathway (dark blue). The atrioventricular node and His-Purkinje system are represented in yellow. Atrioventricular, atriofascicular, and nodoventricular pathways are capable of supporting atrioventricular reciprocating tachycardias. In contrast, an isolated fasciculoventricular pathway can cause subtle preexcitation but does not support clinical tachycardia. Graphic 138850 Version 1.0 https://www.uptodate.com/contents/atrioventricular-reentrant-tachycardia-avrt-associated-with-an-accessory-pathway/print 12/26 7/6/23, 11:12 AM Atrioventricular reentrant tachycardia (AVRT) associated with an accessory pathway - UpToDate Sites of reentry in supraventricular tachyarrhythmias Reentry may occur around a fixed anatomic obstacle or may be functional, developing in the absence of an anatomic obstacle and resulting from the intrinsic heterogeneity of electrophysiologic properties of the myocardial tissue. Reentrant circuits leading to a supraventricular tachyarrhythmia may develop in various parts of the heart: within and around the sinoatrial node (sinus node reentry); within the atrial myocardium (atrial tachycardia, atrial flutter, or atrial fibrillation); within the atrioventricular (AV) node due to the presence of a slow and fast pathway (atrioventricular nodal reentrant tachycardia); or involving the AV node and an accessory pathway (AP) (atrioventricular reentrant tachycardia). LAF: left anterior fascicle; LPF: left posterior fascicle. Graphic 82249 Version 4.0 https://www.uptodate.com/contents/atrioventricular-reentrant-tachycardia-avrt-associated-with-an-accessory-pathway/print 13/26 7/6/23, 11:12 AM Atrioventricular reentrant tachycardia (AVRT) associated with an accessory pathway - UpToDate Orthodromic atrioventricular reentrant tachycardia (AVRT) in the setting of an accessory AV pathway The rhythm strip shows a sinus (S) beat that has a short PR interval and a wide QRS complex as a result of a delta wave (d). Panel A shows an atrial premature beat (APB,*) that is blocked in the accessory pathway (AP), which has a long refractory period but is conducted antegradely through the atrioventricular node (N) and the His-Purkinje system, resulting in a normal PR interval and a narrow and normal QRS complex, as seen on the rhythm strip. After normal myocardial activation, the impulse is conducted retrogradely along the AP, activating the atrium in a retrograde fashion (panel B), which results in a negative P wave. If this activation sequence repeats itself (panel C), an orthodromic atrioventricular reentrant (or reciprocating) tachycardia (AVRT) is established. Graphic 71302 Version 7.0 https://www.uptodate.com/contents/atrioventricular-reentrant-tachycardia-avrt-associated-with-an-accessory-pathway/print 14/26 7/6/23, 11:12 AM Atrioventricular reentrant tachycardia (AVRT) associated with an accessory pathway - UpToDate Electrocardiogram (ECG) showing orthodromic atrioventricular reentrant tachycardia (AVRT) Atrioventricular reentrant tachycardia (AVRT) is a supraventricular tachycardia associated with an accessory pathway connection between the atria and ventricles. The pathway may conduct antegrade only, retrograde only, or both antegrade and retrograde. AVRT is usually initiated by an atrial premature beat (arrow). The most common type of AVRT, termed orthodromic AVRT, uses the AV node and His Purkinje system (which has a relatively short refractory period) for antegrade conduction to the ventricles and the accessory AV pathway (which in these patients has a relatively long antegrade refractory period when compared to the node) for retrograde conduction. During orthodromic AVRT, QRS complexes are narrow. During sinus rhythm, however, wide and bizarre QRS complexes (indicative of the WPW pattern) are caused by conduction over both the accessory and normal pathways, resulting in a fusion beat. Since there is 1:1 retrograde activation of the atrium, a negative P wave may be present following the QRS complex. Graphic 54720 Version 5.0 Sinus rhythm The normal P wave in sinus rhythm is slightly notched since activation of the right atrium precedes that of the left atrium. The P wave is upright in a positive direction in leads I and II. A P wave with a uniform morphology precedes each QRS complex. The rate is between 60 and 100 beats per minute and the cycle length is uniform between sequential P waves and QRS complexes. In addition, the P wave morphology and PR intervals are identical from beat to beat. https://www.uptodate.com/contents/atrioventricular-reentrant-tachycardia-avrt-associated-with-an-accessory-pathway/print 15/26 7/6/23, 11:12 AM Atrioventricular reentrant tachycardia (AVRT) associated with an accessory pathway - UpToDate Graphic 69872 Version 2.0 https://www.uptodate.com/contents/atrioventricular-reentrant-tachycardia-avrt-associated-with-an-accessory-pathway/print 16/26 7/6/23, 11:12 AM Atrioventricular reentrant tachycardia (AVRT) associated with an accessory pathway - UpToDate 12-lead electrocardiogram (ECG) showing orthodromic atrioventricular reentrant tachycardia (AVRT) in a patient with an accessory AV pathway The 12-lead ECG from a patient with Wolff-Parkinson-White shows a regular tachycardia. However, in contrast to the QRS pattern during sinus rhythm, the QRS complexes are narrow, without evidence of a delta wave or pre-excitation; this is due to the fact that antegrade ventricular activation occurs via the normal atrioventricular node-His Purkinje pathway, while retrograde atrial activation is via the accessory pathway. Therefore, this is called an orthodromic atrioventricular reentrant tachycardia (OAVRT). Courtesy of Martin Burke, DO. Graphic 68804 Version 5.0 ECG in Wolff-Parkinson-White https://www.uptodate.com/contents/atrioventricular-reentrant-tachycardia-avrt-associated-with-an-accessory-pathway/print 17/26 7/6/23, 11:12 AM Atrioventricular reentrant tachycardia (AVRT) associated with an accessory pathway - UpToDate The 12-lead ECG shows the typical features of Wolff-Parkinson-White; the PR interval is short (*) and the QRS duration prolonged as a result of a delta wave (arrow), indicating ventricular preexcitation. Courtesy of Martin Burke, DO. Graphic 67181 Version 3.0 https://www.uptodate.com/contents/atrioventricular-reentrant-tachycardia-avrt-associated-with-an-accessory-pathway/print 18/26 7/6/23, 11:12 AM Atrioventricular reentrant tachycardia (AVRT) associated with an accessory pathway - UpToDate Antidromic atrioventricular reentrant tachycardia (AVRT) in the setting of an accessory AV pathway The rhythm strip shows a sinus (S) beat that has a short PR interval and a wide QRS complex as a result of a delta wave (d). Panel A shows the activation sequence with an atrial premature beat (APB,*). The impulse reaches the atrioventricular node (N) before it has repolarized and hence is blocked in this structure. However, the accessory pathway (AP), which has a short refractory period, is able to conduct the impulse antegradely, resulting in an APB with a widened QRS morphology similar to the sinus beat. As seen in panel B, following myocardial activation, the impulse is conducted retrogradely along the His-Purkinje system and AV node, resulting in retrograde atrial activation, seen on the rhythm strip as an inverted P wave. If this activation sequence repeats itself (panel C), a wide QRS complex antidromic atrioventricular reentrant (or reciprocating) tachycardia (AVRT) is established. Graphic 50433 Version 4.0 https://www.uptodate.com/contents/atrioventricular-reentrant-tachycardia-avrt-associated-with-an-accessory-pathway/print 19/26 7/6/23, 11:12 AM Atrioventricular reentrant tachycardia (AVRT) associated with an accessory pathway - UpToDate 12-lead electrocardiogram (ECG) showing antidromic atrioventricular reentrant tachycardia (AVRT) in a patient with an accessory AV pathway The 12-lead ECG of a patient with Wolff-Parkinson-White shows a regular tachycardia. The QRS complexes are widened and are identical to the QRS complexes seen in sinus rhythm; the antegrade conduction to the ventricle is via the accessory pathway and retrograde conduction is via the normal His- atrioventricular node pathway. This is, therefore, an antidromic atrioventricular reentrant tachycardia (AVRT). Courtesy of Martin Burke, DO. Graphic 54484 Version 20.0 ECG in Wolff-Parkinson-White https://www.uptodate.com/contents/atrioventricular-reentrant-tachycardia-avrt-associated-with-an-accessory-pathway/print 20/26 7/6/23, 11:12 AM Atrioventricular reentrant tachycardia (AVRT) associated with an accessory pathway - UpToDate The 12-lead ECG shows the typical features of Wolff-Parkinson-White; the PR interval is short (*) and the QRS duration prolonged as a result of a delta wave (arrow), indicating ventricular preexcitation. Courtesy of Martin Burke, DO. Graphic 67181 Version 3.0 https://www.uptodate.com/contents/atrioventricular-reentrant-tachycardia-avrt-associated-with-an-accessory-pathway/print 21/26 7/6/23, 11:12 AM Atrioventricular reentrant tachycardia (AVRT) associated with an accessory pathway - UpToDate 12-lead electrocardiogram (ECG) showing antidromic atrioventricular reentrant tachycardia (AVRT) The 12-lead ECG shows a wide complex tachycardia in a patient with Wolff- Parkinson-White syndrome and a left lateral accessory pathway. The QRS complexes are wide and have a morphology that is similar to that during sinus rhythm, confirming that this is an antidromic atrioventricular reentrant tachycardia. Graphic 71410 Version 5.0 https://www.uptodate.com/contents/atrioventricular-reentrant-tachycardia-avrt-associated-with-an-accessory-pathway/print 22/26 7/6/23, 11:12 AM Atrioventricular reentrant tachycardia (AVRT) associated with an accessory pathway - UpToDate WPW syndrome with a left posterior accessory pathway The 12 lead ECG from a patient with Wolff-Parkinson-White syndrome (WPW) shows a short PR interval and a delta wave which results in a widened QRS complex. The delta wave is positive in leads I, avL, and V1 to V6 and negative in leads II, III, and avF, compatible with a left posterior accessory pathway. Graphic 80663 Version 2.0 https://www.uptodate.com/contents/atrioventricular-reentrant-tachycardia-avrt-associated-with-an-accessory-pathway/print 23/26 7/6/23, 11:12 AM Atrioventricular reentrant tachycardia (AVRT) associated with an accessory pathway - UpToDate Permanent form of junctional tachycardia 12-lead ECG and lead II rhythm strip obtained from a patient with