rate (up to 300 mcg/kg/minute). Because of their longer half-lives, verapamil, diltiazem, and beta blockers have the potential to suppress arrhythmia recurrence. Thus, these drugs should be used in patients who have early arrhythmia recurrence after termination with adenosine. SUBSEQUENT MANAGEMENT The approach to the management of subsequent AVNRT episodes is based around acute management of recurrent episodes and/or preventive therapy to reduce or eliminate recurrences. Because AVNRT is usually well tolerated in the majority of patients, with a variety of safe and effective treatment options, and there are no compelling data favoring one therapy over another, the choice of long-term management strategies is largely influenced by patient preference. When working with a patient to select a treatment strategy, the following issues should be considered: Frequency of episodes Severity of symptoms Comorbid conditions Medication compliance Medication side effects Patients who have had syncope in the setting of AVNRT may be subject to driving restrictions, which vary between municipalities. (See "Syncope in adults: Management and prognosis", section on 'Driving restrictions'.) Acute management of recurrent episodes For the initial management of recurrent AVNRT, we generally work with the patient to develop a patient-directed treatment approach using either vagal maneuvers or an oral medication ("pill-in-the-pocket" approach). For most patients, we suggest a combination of one or more vagal maneuvers rather than the pill-in-the-pocket approach. Patients who have experienced prior episodes and who have been educated on the proper performance of vagal maneuvers are frequently able to terminate subsequent episodes by https://www.uptodate.com/contents/atrioventricular-nodal-reentrant-tachycardia/print 13/48 7/6/23, 1:48 PM Atrioventricular nodal reentrant tachycardia - UpToDate performing vagal maneuvers on their own. If one or more vagal maneuvers successfully terminate the arrhythmia, patients generally do not need to seek urgent medical attention. Conversely, patients should be instructed to consult with their clinician or seek medical attention if the arrhythmia persists in spite of several attempts at patient-directed vagal maneuvers. (See 'Vagal maneuvers' above.) An alternative patient-directed approach to the management of recurrent AVNRT is the pill-in- the-pocket approach. For selected patients with infrequent, well-tolerated, and long-lasting episodes of AVNRT, a single dose of an antiarrhythmic agent that was previously evaluated under observation can be effective for acute termination of the arrhythmia [40,55,56]. This strategy can both reduce the need for emergency department visits and avoid chronic medical therapy or invasive procedures. This approach has been evaluated with the nondihydropyridine calcium channel blockers, beta blockers, and the class IC antiarrhythmic drug flecainide [56]. However, based upon the efficacy of alternative, lower-risk therapies, and the efficacy of catheter ablation, flecainide is rarely used in the management of AVNRT. The choice of a particular agent will vary from patient to patient depending on comorbidities and patient preference. Preventive therapy The decision to treat with long-term preventive therapy is based upon the following factors: The frequency of the arrhythmia The severity of the symptoms Patient tolerance of medications Patient preference Many patients with infrequent episodes of AVNRT, or those with minimal or well-tolerated symptoms, may prefer a more conservative management approach with either no specific therapy or pharmacologic suppression. If pharmacologic therapy fails or if the side effects result from chronic medical therapy, catheter ablation remains an option. Conversely, for patients with significant symptoms, or for patients who prefer definitive therapy, even for rare, well-tolerated episodes, catheter ablation may be considered early in the patient's management [40,41]. No treatment Patients with infrequent and well-tolerated episodes of AVNRT may choose no chronic therapy. For these patients, we emphasize the patient-directed approach to the termination of recurrent episodes using one or more vagal maneuvers, with the ability to reassess long-term management options at any time should there be a change in the frequency or severity of recurrences. (See 'Acute management of recurrent episodes' above and "Vagal maneuvers".) https://www.uptodate.com/contents/atrioventricular-nodal-reentrant-tachycardia/print 14/48 7/6/23, 1:48 PM Atrioventricular nodal reentrant tachycardia - UpToDate Catheter ablation For patients with episodes of AVNRT that are either frequently occurring, refractory to medical therapy, poorly tolerated (eg, associated with near-syncope or syncope, angina, or severe dyspnea), or result in presentation to the emergency department or admission to the hospital, we recommend catheter ablation rather than chronic medical therapy as initial long-term management strategy. In such cases, the risks associated with recurrent arrhythmic events (eg, syncope with associated trauma) outweigh the procedural risks. In addition, the potential for definitive therapy makes ablation preferable to medical therapy in this setting. Catheter ablation offers the opportunity for definitive cure of AVNRT in greater than 95 percent of patients, with high rates of success in both the typical and atypical forms [57-59]. However, ablation is associated with a small but non-trivial rate of procedural complications. The most significant potential complication of radiofrequency ablation for AVNRT is AV block (approximately 1 percent). Historically, the risk of AV block requiring permanent pacing following ablation ranged from 1 to 3 percent, but in multiple contemporary cohorts, the need for permanent pacing following the procedure has consistently been <1 percent [58,60,61]. Older age and baseline PR interval prolongation are predictors of an increased risk of post-ablation AV block [62-65]. However, due to its high success rate in curing AVNRT by successful slow pathway ablation and low complication rate, catheter ablation is increasingly favored among patients with recurrent AVNRT [40,41]. (See "Overview of catheter ablation of cardiac arrhythmias", section on 'Complications'.) The general approach to the catheter ablation of AVNRT is based upon the concept of dual AV nodal pathways. The most common AVNRT circuit (80 to 90 percent) involves antegrade conduction down the slow pathway and retrograde conduction up the fast pathway. The ablation target is the posterior slow pathway ( figure 8) since ablation here carries the lowest risk of AV block, preserves fast pathway function (and a normal PR interval post-ablation), and is facilitated by reliable anatomic and electrophysiologic landmarks. The anterior fast pathway can also be ablated, but this approach is now limited to a few special circumstances since fast pathway ablation results in a long PR interval during sinus rhythm and is associated with a higher risk of heart block. During ablation for atypical "fast-slow" AVNRT, the slow pathway is the usual target. The slow pathway in these patients tends to be posteriorly located near the coronary sinus ostium as with patients who have typical AVNRT. However, there are reports of rare cases of atypical AV nodal reentry where the slow retrograde limb of the circuit is located more superiorly near the compact AV node [66]. The relative efficacy and costs of catheter ablation and medical therapy were compared in a series of 79 patients with newly documented supraventricular tachycardia (SVT) who were treated with either ablation or pharmacologic therapy, based upon patient preference [67]. After a follow-up period of 12 months, both medication and ablation decreased the frequency of https://www.uptodate.com/contents/atrioventricular-nodal-reentrant-tachycardia/print 15/48 7/6/23, 1:48 PM Atrioventricular nodal reentrant tachycardia - UpToDate arrhythmia-related symptoms, but ablation was more likely to result in complete abolition of symptoms (74 versus 33 percent). (See 'Chronic suppressive therapy' below.) Chronic suppressive therapy For patients with symptomatic episodes of AVNRT who are not candidates for or who have declined catheter ablation, chronic medical therapy using beta blockers, nondihydropyridine calcium channel blockers, or antiarrhythmic drugs can be initiated in an effort to suppress recurrent arrhythmias. There are few data comparing the relative efficacy of various agents used for chronic suppressive therapy of AVNRT. Because they are effective and well tolerated, the medications that are most commonly used for the chronic suppression of AVNRT are beta blockers (eg, metoprolol) and nondihydropyridine calcium channel blockers (eg, verapamil and diltiazem). Traditionally, beta blockers were preferred rather than calcium channel blockers unless the patient has reactive airway disease or another contraindication, although calcium channel blockers may have fewer side effects. The choice of a starting dose for chronic suppressive medication will vary depending upon the baseline heart rate and blood pressure. The dose of beta blocker or calcium channel blocker is titrated as tolerated with the dose limited to avoid hypotension (symptomatic hypotension or asymptomatic systolic blood pressure <100 mmHg) and bradycardia (heart rate <55 beats per minute). Among patients who do not respond to optimally titrated diltiazem, verapamil, or beta blockers and who do not want to pursue ablation, the following antiarrhythmic drugs may be considered: Flecainide (class IC) Propafenone (class IC) Sotalol (class III) Dofetilide (class III) Amiodarone (class III) The choice of a particular agent will need to be individualized in each patient based on other comorbidities. However, due to the potential for significant toxicities, including proarrhythmia, the use of class I and class III antiarrhythmic drugs for the management of AVNRT should be reserved for rare cases and should be administered in consultation with an electrophysiologist. In particular, because of the risk of toxicities with long-term use, amiodarone is usually avoided in young patients. (See "Amiodarone: Adverse effects, potential toxicities, and approach to monitoring".) SOCIETY GUIDELINE LINKS https://www.uptodate.com/contents/atrioventricular-nodal-reentrant-tachycardia/print 16/48 7/6/23, 1:48 PM Atrioventricular nodal reentrant tachycardia - UpToDate 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".) INFORMATION FOR PATIENTS UpToDate offers two types of patient education materials, "The Basics" and "Beyond the Basics." th th The Basics patient education pieces are written in plain language, at the 5 to 6 grade reading level, and they answer the four or five key questions a patient might have about a given condition. These articles are best for patients who want a general overview and who prefer short, easy-to-read materials. Beyond the Basics patient education pieces are longer, more th th sophisticated, and more detailed. These articles are written at the 10 to 12 grade reading level and are best for patients who want in-depth information and are comfortable with some medical jargon. Here are the patient education articles that are relevant to this topic. We encourage you to print or e-mail these topics to your patients. (You can also locate patient education articles on a variety of subjects by searching on "patient info" and the keyword(s) of interest.) Basics topic (see "Patient education: Supraventricular tachycardia (SVT) (The Basics)") SUMMARY AND RECOMMENDATIONS Definition and prevalence Atrioventricular nodal reentrant tachycardia (AVNRT) is a regular tachycardia that results from the formation of a reentry circuit confined to the AV node and perinodal atrial tissue. The physiologic substrate for AVNRT involves dual electrical pathways in or near the AV node. It is the most common form of regular, sustained, paroxysmal supraventricular tachycardia (PSVT), and it accounts for nearly two- thirds of all PSVTs. (See 'Introduction' above and 'Epidemiology' above.) Pathophysiology The simplest concept of AV nodal physiology that allows for reentry involves separate electrical pathways within or proximal to the AV node ( figure 3). The fast pathway conducts rapidly and has a relatively long refractory period, while the slow pathway conducts relatively slowly and has a shorter refractory period. Both typical and atypical forms of AVNRT can result from reentry involving the fast and slow pathways. Tachycardia is initiated by a premature beat. (See 'Anatomy and pathophysiology' above.) https://www.uptodate.com/contents/atrioventricular-nodal-reentrant-tachycardia/print 17/48 7/6/23, 1:48 PM Atrioventricular nodal reentrant tachycardia - UpToDate Symptoms Patients with AVNRT most commonly report palpitations, dizziness or lightheadedness, and dyspnea. Because of the paroxysmal nature of the arrhythmia, the onset and termination of the symptoms are usually sudden. Those with significant heart disease may have additional symptoms such as dyspnea and chest pain. (See 'Symptoms' above.) ECG features There are several features seen on an ECG that are helpful in confirming the diagnosis of AVNRT, including the ventricular rate, abrupt onset following a PAC, the relationship between QRS complexes and P waves, and spontaneous termination with AV block in the absence of a PAC. (See 'Electrocardiographic characteristics' above.) Initial management The initial management ( algorithm 1) of a patient presenting with a narrow QRS tachycardia and suspected AVNRT is guided by whether or not the patient is experiencing signs and symptoms of hemodynamic instability related to the rapid heart rate (eg, hypotension, shortness of breath, chest pain suggestive of coronary ischemia, shock, and/or decreased level of consciousness). Hemodynamically unstable Rare patients who are severely hemodynamically unstable should undergo urgent cardioversion. (See 'Electrical cardioversion' above.) Hemodynamically stable For patients who are hemodynamically stable and able to effectively perform the vagal maneuvers, we recommend at least one or two attempts of a standard Valsalva maneuver, followed by at least one or two attempts using the modified Valsalva maneuver (if AVNRT persists), as the initial treatment for AVNRT rather than another vagal maneuver or adenosine (Grade 1B). (See 'Vagal maneuvers' above.) If vagal maneuvers cannot be performed or if they fail to terminate the arrhythmia, intravenous (IV) medical therapy that blocks AV nodal conduction is indicated as the next step. For patients with AVNRT that persists following vagal maneuvers (or in whom vagal maneuvers cannot be adequately performed), we recommend IV adenosine ( algorithm 3) rather than a calcium channel blocker or a beta blocker (Grade 1B). (See 'Adenosine' above.) If both vagal maneuvers and adenosine are ineffective, or when these options are followed by an immediate recurrence of the tachycardia, IV verapamil, diltiazem, or a beta blocker can be used to terminate or prevent recurrent AVNRT. (See 'Other AV nodal blocking drugs' above.) https://www.uptodate.com/contents/atrioventricular-nodal-reentrant-tachycardia/print 18/48 7/6/23, 1:48 PM Atrioventricular nodal reentrant tachycardia - UpToDate Management of recurrent episodes The approach to the management of subsequent AVNRT episodes is based around acute management of recurrent episodes and/or preventive therapy to reduce or eliminate recurrences. Because AVNRT is usually well- tolerated in the majority of patients, with a variety of safe and effective treatment options, and there are no compelling data favoring one therapy over another, the choice of long- term management strategies is largely influenced by patient preference. Initial management For the initial management of recurrent AVNRT, we generally work with the patient to develop a patient-directed treatment approach using either vagal maneuvers or an oral medication ("pill-in-the-pocket" approach). For most patients, we suggest a combination of one or more vagal maneuvers rather than the pill-in-the-pocket approach (Grade 2C). (See 'Acute management of recurrent episodes' above.) Infrequent and well-tolerated episodes Patients with infrequent and well-tolerated episodes of AVNRT may choose no chronic therapy. For these patients, we emphasize the patient-directed approach to the termination of recurrent episodes using one or more vagal maneuvers. (See 'No treatment' above.) Frequent or poorly tolerated episodes For patients with episodes of AVNRT that are either frequently occurring or poorly tolerated (eg, associated with near-syncope or syncope, angina, or severe dyspnea), we recommend catheter ablation rather than chronic medical therapy as initial long-term management strategy (Grade 1B). In such cases, the risks associated with recurrent arrhythmic events (eg, syncope with associated trauma) outweigh the procedural risks. In addition, the potential for definitive therapy makes ablation preferable to medical therapy in this setting. (See 'Catheter ablation' above.) For patients with poorly tolerated symptomatic episodes of AVNRT who are not candidates for or who have declined catheter ablation, chronic medical therapy using beta blockers, nondihydropyridine calcium channel blockers, or antiarrhythmic drugs can be initiated in an effort to suppress recurrent arrhythmias. Our experts typical prefer beta blockers rather than calcium channel blockers or antiarrhythmic drugs as the initial option for chronic medical therapy. (See 'Chronic suppressive therapy' above.) Use of UpToDate is subject to the Terms of Use. REFERENCES https://www.uptodate.com/contents/atrioventricular-nodal-reentrant-tachycardia/print 19/48 7/6/23, 1:48 PM Atrioventricular nodal reentrant tachycardia - UpToDate 1. Liuba I, J nsson A, S fstr m K, Walfridsson H. 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Significance of newly acquired negative T waves after interruption of paroxysmal reentrant supraventricular tachycardia with narrow QRS complex. Am J Cardiol 2000; 85:261. 38. Villain E, Vetter VL, Garcia JM, et al. Evolving concepts in the management of congenital junctional ectopic tachycardia. A multicenter study. Circulation 1990; 81:1544. 39. Fishberger SB, Rossi AF, Messina JJ, Saul JP. Successful radiofrequency catheter ablation of congenital junctional ectopic tachycardia with preservation of atrioventricular conduction in a 9-month-old infant. Pacing Clin Electrophysiol 1998; 21:2132. 40. Page RL, Joglar JA, Caldwell MA, et al. 2015 ACC/AHA/HRS Guideline for the Management of Adult Patients With Supraventricular Tachycardia: A Report of the American College of Cardiology/American Heart Association Task Force on Clinical Practice Guidelines and the Heart Rhythm Society. 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Pacing Clin Electrophysiol 1997; 20:1698. 65. Reithmann C, Hoffmann E, Gr newald A, et al. Fast pathway ablation in patients with common atrioventricular nodal reentrant tachycardia and prolonged PR interval during sinus rhythm. Eur Heart J 1998; 19:929. 66. Kaneko Y, Naito S, Okishige K, et al. Atypical Fast-Slow Atrioventricular Nodal Reentrant Tachycardia Incorporating a "Superior" Slow Pathway: A Distinct Supraventricular Tachyarrhythmia. Circulation 2016; 133:114. https://www.uptodate.com/contents/atrioventricular-nodal-reentrant-tachycardia/print 24/48 7/6/23, 1:48 PM Atrioventricular nodal reentrant tachycardia - UpToDate 67. Bathina MN, Mickelsen S, Brooks C, et al. Radiofrequency catheter ablation versus medical therapy for initial treatment of supraventricular tachycardia and its impact on quality of life and healthcare costs. Am J Cardiol 1998; 82:589. Topic 902 Version 46.0 https://www.uptodate.com/contents/atrioventricular-nodal-reentrant-tachycardia/print 25/48 7/6/23, 1:48 PM Atrioventricular nodal reentrant tachycardia - UpToDate GRAPHICS Electrophysiologic characteristics of the different types of supraventricular tachycardia (SVT) Characteristic Reentrant Triggered Automatic Initiation by extrastimuli and/or continuous pacing Yes Yes No Initiation by continuous pacing depends upon the rate No Yes No and number of stimuli Termination by extrastimuli Yes No No Termination by continuous pacing (overdrive) Yes Yes No Overdrive suppression of tachycardia No No Yes Overdrive enhancement of tachycardia Yes Yes No Entrainment possible Yes No No First P wave identical to P waves in arrhythmia No Sometimes Yes Warm-up or acceleration of pacemaker after onset No Sometimes Yes Graphic 53347 Version 2.0 https://www.uptodate.com/contents/atrioventricular-nodal-reentrant-tachycardia/print 26/48 7/6/23, 1:48 PM Atrioventricular nodal reentrant tachycardia - UpToDate Schematic representation of Koch's triangle and environment Around the compact atrioventricular (AV) node is an extended zone with transitional cells. LBB: left bundle branch; RBB: right bundle branch. Graphic 69647 Version 2.0 https://www.uptodate.com/contents/atrioventricular-nodal-reentrant-tachycardia/print 27/48 7/6/23, 1:48 PM Atrioventricular nodal reentrant tachycardia - UpToDate Koch's triangle and fast and slow pathways Schematic representation of Koch's triangle which is bounded by the tricuspid ring and the tendon of Todoro. The tendon of Todoro and the tricuspid ring are in close proximity forming the apex of the triangle near the His bundle at the membranous septum. Koch's triangle can be divided into thirds: the anterior contains the compact AV node; the posterior contains the coronary sinus; and the middle or mid-septal third is between the anterior and posterior portions. The anterior third is associated with fast pathways, and the middle and posterior thirds with slow pathways. Graphic 52196 Version 2.0 https://www.uptodate.com/contents/atrioventricular-nodal-reentrant-tachycardia/print 28/48 7/6/23, 1:48 PM Atrioventricular nodal reentrant tachycardia - UpToDate Slow-fast form of atrioventricular nodal reentrant tachycardia (AVNRT) Representation of dual pathway physiology involving the atrioventricular (AV) node and perinodal atrial tissue in the common form of AVNRT. Left panel: A normal sinus beat (A ) is conducted through the fast pathway (F) to the final common pathway (fcp) in the AV node and into the Bundle of His. The conduction through the slow pathway (S) runs into the refractory period of the impulse through the fast pathway and is extinguished. 1 Middle panel: A critically timed atrial premature beat (A ) finds the fast pathway refractory in the antegrade direction but is able to conduct antegrade through the slow pathway, which has a shorter refractory period. If excitability in the fast pathway has recovered by 2 the time the impulse reaches the fcp, there may be retrograde activation of the fast pathway. Right panel: The retrograde impulse throws off an echo to the atrium (A*), and, if the slow pathway has recovered its excitability, the impulse reenters the slow pathway and produces ventricular depolarization (V*). If the mechanism persists, a repetitive circuit is established that creates a sustained reentrant tachycardia. The sequence of antegrade (S) and retrograde (F) conduction is called the slow-fast form of AVNRT. Graphic 79760 Version 6.0 https://www.uptodate.com/contents/atrioventricular-nodal-reentrant-tachycardia/print 29/48 7/6/23, 1:48 PM Atrioventricular nodal reentrant tachycardia - UpToDate Electrophysiologic study (EPS) in a patient with atrioventricular nodal reentrant tachycardia and dual AV nodal pathways The tracing shows three surface ECG leads (I, II, V1) and intracardiac recordings from the high right atrium (HRA), bundle of His (HIS), right ventricular apex (RVA), and coronary sinus (CS). During atrial pacing (S1) at a cycle length of 600 milliseconds (100 beats per minute), the AH interval is 120 milliseconds. An atrial premature beat (S2) is added at a coupling cyle of 420 milliseconds; this results in a prolongation of the PR interval and increase in the AH interval to 184 milliseconds. Courtesy of Martin Burke, DO. Graphic 60369 Version 4.0 https://www.uptodate.com/contents/atrioventricular-nodal-reentrant-tachycardia/print 30/48 7/6/23, 1:48 PM Atrioventricular nodal reentrant tachycardia - UpToDate Electrophysiologic study (EPS) in a patient with atrioventricular nodal reentrant tachycardia and dual AV nodal pathways The tracing shows three surface ECG leads (I, II, V1) and intracardiac recordings from the high right atrium (HRA), bundle of His (HIS), right ventricular apex (RVA), and coronary sinus (CS). During atrial pacing (S1) at a cycle length of 600 milliseconds (100 beats per minute), the AH interval is 120 milliseconds. An atrial premature beat (S2) is added at a coupling cyle of 410 milliseconds; this results in a prolongation of the PR interval and increase in the AH interval to 242 milliseconds, which represents a 60-millisecond increase compared with the AH when a premature beat was added with a coupling interval of 420 milliseconds. This represents a "jump" due to a shift of AV nodal conduction from the fast to slow AV nodal pathway. Since the fast pathway has time to recover, there is retrograde VA conduction via the fast pathway, resulting in the occurrence of a retrograde His depolarization (HIS "A") and an atrial echo beat at the CS os area (CS 10-9). Courtesy of Martin Burke, DO. Graphic 72161 Version 4.0 https://www.uptodate.com/contents/atrioventricular-nodal-reentrant-tachycardia/print 31/48 7/6/23, 1:48 PM Atrioventricular nodal reentrant tachycardia - UpToDate Generation of ECG in common form of atrioventricular nodal reentrant tachycardia (AVNRT) Ladder diagram of the common (slow-fast) form of AVNRT showing transmission of the impulse in atrial, atrioventricular (AV) nodal, and ventricular tissue and the resultant ECG. The first two cycles show the normal sinus beat (A ) conducting through the fast pathway (F) to the ventricle (V ) with the impulse blocked in the slow pathway. The premature atrial beat (A on ladder diagram, P on ECG) is timed critically; it finds the fast pathway refractory but is able to conduct through slow pathway, resulting in a long PR interval, and a ventricular depolarization (V ). It is also able to reenter and conduct 1 1 2 2 retrogradely up the now recovered fast pathway, resulting in an inverted P wave (A*) that is buried in the QRS complex. This atrial echo beat (A*) then reenters the now recovered slow pathway, which conducts anterogradely and results in ventricular depolarization (V*). The cycle repeats, and AV nodal reentry is established. ECG: electrocardiogram. Graphic 50122 Version 6.0 https://www.uptodate.com/contents/atrioventricular-nodal-reentrant-tachycardia/print 32/48 7/6/23, 1:48 PM Atrioventricular nodal reentrant tachycardia - UpToDate Uncommon fast-slow variant of atrioventricular nodal reentrant tachycardia (AVNRT) Diagrammatic representation in the circuit (left panel) and the ladder diagram (right panel) of the uncommon form of AVNRT (fast-slow variant). Antegrade conduction is through the fast (F) pathway and retrograde conduction is through the slow (S) pathway. Because of slow retrograde activation of the atrium, the P wave occurs after the QRS complex with a long RP interval and relatively short PR interval before the next QRS complex. ECG: electrocardiogram. Graphic 56806 Version 4.0