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 https://www.uptodate.com/contents/atrioventricular-nodal-reentrant-tachycardia/print 33/48 7/6/23, 1:48 PM Atrioventricular nodal reentrant tachycardia - UpToDate Atypical atrioventricular nodal reentrant tachycardia Shown are three simultaneous ECG leads (I, II, and III) during an uncommon or atypical form of an atrioventricular nodal reentrant tachycardia (AVNRT) in which antegrade conduction to the ventricle is via the fast pathway and retrograde atrial activation is by the slow pathway. As a result of delayed atrial activation, there is a long RP and short PR interval and a negative P wave in the inferior leads II and III. Graphic 66828 Version 2.0 https://www.uptodate.com/contents/atrioventricular-nodal-reentrant-tachycardia/print 34/48 7/6/23, 1:48 PM Atrioventricular nodal reentrant tachycardia - UpToDate 12 lead ECG of an uncommon form of an atrioventricular nodal reentrant tachycardia The 12 lead ECG shows a regular, narrow complex tachycardia at a rate of 130 beats per minute. The QRS complexes are normal. There is an abnormal "notching" within the ST segment, representing a retrograde P wave (*). The interval from the proceeding R wave (RP interval) is longer than the PR interval; this is a "long RP tachycardia," due to an atypical atrioventricular nodal reentrant tachycardia. Courtesy of Martin Burke, DO. Graphic 81639 Version 4.0 Normal ECG https://www.uptodate.com/contents/atrioventricular-nodal-reentrant-tachycardia/print 35/48 7/6/23, 1:48 PM Atrioventricular nodal reentrant tachycardia - UpToDate Normal electrocardiogram showing normal sinus rhythm at a rate of 75 beats/minute, a PR interval of 0.14 seconds, a QRS interval of 0.10 seconds, and a QRS axis of approximately 75 . Courtesy of Ary Goldberger, MD. Graphic 76183 Version 4.0 https://www.uptodate.com/contents/atrioventricular-nodal-reentrant-tachycardia/print 36/48 7/6/23, 1:48 PM Atrioventricular nodal reentrant tachycardia - UpToDate Typical atrioventricular nodal reentrant tachycardia The first two complexes are normal sinus beats with a normal P wave followed by a QRS complex. The third complex, an atrial premature beat (APB), has a prolonged PR interval; it initiates a common or typical atrioventricular nodal reentrant tachycardia (AVNRT) in which antegrade conduction to the ventricle is via the slow pathway and retrograde atrial activation is by the fast pathway. Although no distinct P wave is seen, the QRS complex has a small terminal deflection, known as a pseudo r', which is the P wave superimposed upon the terminal portion of the QRS complex. Graphic 54290 Version 3.0 https://www.uptodate.com/contents/atrioventricular-nodal-reentrant-tachycardia/print 37/48 7/6/23, 1:48 PM Atrioventricular nodal reentrant tachycardia - UpToDate 12 lead ECG of the common form of an atrioventricular nodal reentrant tachycardia The 12 lead ECG shows a regular narrow complex tachycardia with a rate of 135 beats per minute; no P waves can be seen. The QRS morphology is identical to that seen during sinus rhythm. Courtesy of Martin Burke, DO. Graphic 57001 Version 2.0 Normal ECG https://www.uptodate.com/contents/atrioventricular-nodal-reentrant-tachycardia/print 38/48 7/6/23, 1:48 PM Atrioventricular nodal reentrant tachycardia - UpToDate Normal electrocardiogram showing normal sinus rhythm at a rate of 75 beats/minute, a PR interval of 0.14 seconds, a QRS interval of 0.10 seconds, and a QRS axis of approximately 75 . Courtesy of Ary Goldberger, MD. Graphic 76183 Version 4.0 https://www.uptodate.com/contents/atrioventricular-nodal-reentrant-tachycardia/print 39/48 7/6/23, 1:48 PM Atrioventricular nodal reentrant tachycardia - UpToDate Causes of palpitations Cardiac Arrhythmias (tachyarrhythmias, bradyarrhythmias, and ectopic beats) due to: Structural heart disease Underlying conduction system abnormality Medical comorbidity (eg, COPD, pulmonary embolism) Idiopathic Mitral valve prolapse Pacemaker syndrome Atrial myxoma Intra-cardiac shunt High output states Normal pregnancy Anemia Paget disease of bone Fever Metabolic and endocrine Hypoglycemia Hyperthyroidism Pheochromocytoma Catecholamine excess Stress Exercise Substance use Cocaine Caffeine Alcohol Amphetamines Nicotine Medications Sympathomimetic agents Vasodilators Anticholinergics Beta blocker withdrawal https://www.uptodate.com/contents/atrioventricular-nodal-reentrant-tachycardia/print 40/48 7/6/23, 1:48 PM Atrioventricular nodal reentrant tachycardia - UpToDate Psychiatric disorders Generalized anxiety Panic disorder Somatization disorder COPD: chronic obstructive pulmonary disease. Graphic 64306 Version 3.0 https://www.uptodate.com/contents/atrioventricular-nodal-reentrant-tachycardia/print 41/48 7/6/23, 1:48 PM Atrioventricular nodal reentrant tachycardia - UpToDate Algorithm for the acute treatment of atrioventricular nodal reentrant tachycar AVNRT: atrioventricular nodal reentrant tachycardia; IV: intravenous; ECG: electrocardiogram; CCB: calcium channel blocker; ACLS: advanced cardiac life support; BB: beta blocker. https://www.uptodate.com/contents/atrioventricular-nodal-reentrant-tachycardia/print 42/48 7/6/23, 1:48 PM Atrioventricular nodal reentrant tachycardia - UpToDate Evidence of hemodynamic instability may include hypotension, altered mental status, or signs and symptom of chest pain or heart failure. If patient becomes hemodynamically unstable at any point, proceed with electrical cardioversion. If initial low-energy shock is unsuccessful, subsequent shocks should be attempted using higher energy levels. The exact energy level varies depending upon the type of defibrillator (ie, biphasic versus monophasic Patients should be sedated and monitored when undergoing electrical cardioversion. Most patients who remain hemodynamically stable and who are able to participate in vagal maneuvers should perform several attempts prior to pharmacologic therapy. Adenosine is administered by rapid IV injection over one to two seconds at a peripheral site, followed by a normal saline flush. The rapid administration of both the drug and the saline flush is most easily accomplishe through a three-way stopcock. The usual initial dose is 6 mg, which can be followed by a dose of 12 mg if not successful. A dose of 18 mg can be used if 12 mg fails to convert the patient to sinus rhythm. Repeated dosin beyond the 18 mg bolus is not usually effective. Adenosine can be readministered immediately, for up to three doses, if AVNRT reoccurs. If AVNRT continue to recur following successful termination(s) with adenosine, a second drug should be administered (eg, BB o CCB) in an attempt to suppress the arrhythmia. The choice between BB and CCB is usually based on familiarity with and availability of the particular agents Typical options and doses include: Verapamil 5 to 10 mg IV bolus over two minutes; if no response, an additional 10 mg IV bolus may be administered 15 to 30 minutes following the initial dose. Diltiazem 0.25 mg/kg (average dose 20 mg) IV bolus over two minutes; if no response, an additional 0. mg/kg (average dose 25 mg) IV bolus may be administered 15 to 30 minutes following the initial dose. Metoprolol 2.5 to 5 mg IV bolus over two to five minutes; if no response, an additional 2.5 to 5 mg IV bolus may be administered every 10 minutes to a total dose of 15 mg. Refer to UpToDate content on advanced cardiac life support. Diagnostic testing is usually indicated following the initial presentation with AVNRT or in patients with signs/symptoms of concurrent angina or heart failure. Stable patients can undergo diagnostic testing in an outpatient environment. Refer to UpToDate topics for diagnostic approach. * Preventive therapy may include no specific treatment, pharmacologic suppression, or catheter ablation depending upon the frequency of AVNRT, severity of associated symptoms, and patient preference. Graphic 126471 Version 1.0 https://www.uptodate.com/contents/atrioventricular-nodal-reentrant-tachycardia/print 43/48 7/6/23, 1:48 PM Atrioventricular nodal reentrant tachycardia - UpToDate Adult tachycardia with a pulse algorithm 2020 update Reprinted with permission. ACLS Provider Manual. Copyright 2020 American Heart Association, Inc. Graphic 130747 Version 10.0 https://www.uptodate.com/contents/atrioventricular-nodal-reentrant-tachycardia/print 44/48 7/6/23, 1:48 PM Atrioventricular nodal reentrant tachycardia - UpToDate Approach to adenosine dosing in stable adults with suspected supraventricular tachyarrhythmia This figure summarizes the initial dosing, administration, and need for repeat dosing of adenosine in a hemo stable adult with suspected AV node-dependent SVT. Adenosine can be used as a diagnostic aid to identify th rhythm or as a therapy to terminate SVTs that rely on AV node conduction. AV node-dependent SVTs include A reentrant tachycardia (AVNRT) and AV reentrant (or reciprocating) tachycardia (AVRT). The management of su node-dependent SVT in hemodynamically stable adults commonly starts with a trial of 1 or more vagal mane proceeding to adenosine therapy. If the patient has hemodynamically unstable SVT, cardioversion is indicate UpToDate content for details on management of SVTs. https://www.uptodate.com/contents/atrioventricular-nodal-reentrant-tachycardia/print 45/48 7/6/23, 1:48 PM Atrioventricular nodal reentrant tachycardia - UpToDate AV: atrioventricular; SVT: supraventricular tachycardia; IV: intravenous; ACC: American College of Cardiology; American Heart Association; HRS: Heart Rhythm Society; ECG: electrocardiogram. Lower adenosine doses are indicated in certain clinical settings. If central venous administration is perform adenosine dose is 3 mg; if needed (SVT persists and there is no AV block), the dose may be increased to 6 mg mg for subsequent doses. For heart transplant recipients, the initial adenosine dose is 1 mg; if needed (SVT p there is no AV block), the dose may be increased to 2 mg and then 3 mg for subsequent doses. An 18 mg dose is more likely to be required to produce AV block in patients with a body weight >70 kg, par When a third dose is indicated, an alternative approach is to administer 12 mg (in those weighing >110 kg. [1] mg) as described in the 2015 ACC/AHA/HRS Guideline for the Management of Adult Patients with Supraventr Tachycardia. [2] SVT termination in response to adenosine includes SVT termination closely followed by SVT recurrence. Refer to UpToDate content on treatment of SVT for dosing of second-line AV nodal blockers. If the SVT pers second-line AV nodal blocker therapy, electrical cardioversion is performed, as discussed in UpToDate conten treatment of SVT. SVTs that are not AV node dependent include atrial flutter, atrial fibrillation, and atrial tachycardia. When AV is induced by adenosine, the ECG may reveal atrial activity diagnostic of these rhythms. References: 1. Prabhu S, Mackin V, McLellan AJA, et al. Determining the optimal dose of adenosine for unmasking dormant pulmonary vein co following atrial brillation ablation: Electrophysiological and hemodynamic assessment. DORMANT-AF study. J Cardiovasc Electr 28:13. 2. Page RL, Joglar JA, Caldwell MA, et al. 2015 ACC/AHA/HRS guideline for the management of adult patients with supraventricular report of the American College of Cardiology/American Heart Association Task Force on Clinical Practice Guidelines and the Hea Society. Circulation 2016; 133:e506. Graphic 141417 Version 3.0 https://www.uptodate.com/contents/atrioventricular-nodal-reentrant-tachycardia/print 46/48 7/6/23, 1:48 PM Atrioventricular nodal reentrant tachycardia - UpToDate Radiofrequency ablation sites in Koch's triangle Schematic representation of Koch's triangle which is bounded by the tricuspid ring and the tendon of Todoro. 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. The anterior and posterior approaches to ablate the fast and slow pathways, respectively, are indicated by the position of the catheters (shown in green). Graphic 62108 Version 1.0 https://www.uptodate.com/contents/atrioventricular-nodal-reentrant-tachycardia/print 47/48 7/6/23, 1:48 PM Atrioventricular nodal reentrant tachycardia - UpToDate Contributor Disclosures Bradley P Knight, MD, FACC Grant/Research/Clinical Trial Support: Abbott [Electrophysiology]; Atricure [Electrophysiology]; Biosense Webster [Electrophysiology]; Biotronik [Electrophysiology]; Boston Scientific [Electrophysiology]; BSCI [Electrophysiology]; MDT [Electrophysiology]; Philips [Electrophysiology]. Consultant/Advisory Boards: Abbott [Electrophysiology]; Atricure [Electrophysiology]; Biosense Webster [Electrophysiology]; Biotronik [Electrophysiology]; Boston Scientific [Electrophysiology]; BSCI [Electrophysiology]; CVRx [Heart failure]; MDT [Electrophysiology]; Philips [Electrophysiology]; Sanofi [Arrhythmias]. Speaker's Bureau: Abbott [Electrophysiology]; Biosense Webster [Electrophysiology]; Biotronik [Electrophysiology]; Boston Scientific [Transeptal catheterization]; BSCI [Electrophysiology]; MDT [Electrophysiology]. All of the relevant financial relationships listed have been mitigated. Mark S Link, MD No relevant financial relationship(s) with ineligible companies to disclose. Susan B Yeon, MD, JD, FACC No relevant financial relationship(s) with ineligible companies to disclose. Contributor disclosures are reviewed for conflicts of interest by the editorial group. When found, these are addressed by vetting through a multi-level review process, and through requirements for references to be provided to support the content. Appropriately referenced content is required of all authors and must conform to UpToDate standards of evidence. Conflict of interest policy https://www.uptodate.com/contents/atrioventricular-nodal-reentrant-tachycardia/print 48/48