Atrioventricular Node Reentry Supraventricular Tachycardia Treatment & Management

Updated: Jan 25, 2022
  • Author: Glenn T Wetzel, MD, PhD; Chief Editor: Stuart Berger, MD  more...
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Treatment

Medical Care

Patients with known supraventricular tachycardia (SVT) who are presenting with recurrence and receiving effective therapy usually do not require admission. New patients are frequently admitted for a period of observation and to provide teaching and reassurance to the parent or child. Often, certain antiarrhythmic medications are initiated in the hospital while the patient is monitored for adverse effects (eg, proarrhythmia).

Emergency treatment of patients with hemodynamic instability in the setting of atrioventricular node reentrant tachycardia (AVNRT) is directed at converting the rhythm to sinus through a brief episode of AV block.

Perform synchronized electrical cardioversion if patients have a deteriorating condition or if there is no response to the initial attempts of conversion (see below).

The use of vagal maneuvers can be very helpful in the acute setting. In the infant, apply a plastic bag containing ice cubes and water to the face for 25-30 seconds to induce the diving reflex, a vagal stimulus. Note that this maneuver may be stressful to the infant and parents alike. In older children, other vagal maneuvers can be attempted, such as breathholding or the Valsalva maneuver. If this is not successful, the next step is to administer medication. The drug of choice is adenosine, administered from an intravenous site as close as possible to the heart. Importantly, data have indicated low efficacy of the initial recommended doses of adenosine. Use of esmolol, a short-acting beta-blocker, also has been successful.

Esophageal overdrive atrial pacing is also quite safe and effective in converting to sinus rhythm.

Recording of a long 3- or 12-lead rhythm strip during attempts to terminate the tachycardia may be invaluable in subsequent efforts to define the mechanism of SVT and should be routinely performed.

Transfer

Ideally, as with most tachycardias in children, transfer should take place after successful conversion has been achieved.

Diet

Patients with AVNRT should avoid caffeine-containing items so that SVT is not provoked by caffeine-induced premature beats.

Next:

Surgical Care

Catheter ablation

See also the Guidelines section for recommendations for the management of supraventricular tachycardia (SVT) by the European Society of Cardiology (ESC) and Association for European Paediatric and Congenital Cardiology (AEPC) (2019), [24] as well as those from the American College of Cardiology, American Heart Association, and the Heart Rhythm Society (ACC/AHA/HRS) (2015). [25]

Knowledge of the anatomy of the Koch triangle (ie, where the AV node is located) is needed to understand how slow pathway ablation is performed. The Koch triangle is defined by the ostium of the coronary sinus posteriorly. The apex of the triangle is defined anteriorly by the His bundle. The tendon of Todaro and the tricuspid valve annulus comprise the sides of the triangle. In the electrophysiology laboratory, landmarks of the Koch triangle are identified by one catheter recording the His deflection and a second catheter placed in the ostium of the coronary sinus. The Koch triangle is located between these two catheters.

The fast pathway is located anteriorly, along the tendon of Todaro. The slow pathway is generally located posterior-inferiorly, along the tricuspid annulus, near the ostium of the coronary sinus. However, less common variations have been described. [4, 26]

Ablation of atrioventricular node reentrant tachycardia (AVNRT) is accomplished by delivering either radiofrequency or cryothermal energy over the slow pathway. Because its location is more posterior and, thus, distant from the AV node, incidence of complete heart block with the use of radiofrequency energy is low (1.2%). [27] The overall success rate of radiofrequency ablation on AVNRT has been more than 98% over the past decade.

In adults with mild congenital heart disease, the European Society of Cardiology recommends catheter ablation over long-term medical therapy for symptomatic, sustained recurrent SVT (AVNRT, atrioventricular reciprocating tachycardia [AVRT], atrial tachycardia [AT], and intraatrial reentrant tachycardia [IART]), or if SVT is potentially related to sudden cardiac death (SCD). [28, 29]

Cryothermal energy has allowed catheter mapping of specific ablation targets. This is especially advantageous in children with AVNRT because it allows greater reversibility of conduction block, decreasing the risk of complete AV block. The use of cryothermal energy to map and ablate arrhythmia substrates has been shown to be safer than radiofrequency energy; however, early studies showed that this safety came at the expense of acutely lower success rates and higher recurrence rates at midterm follow-up. [30, 31, 32]

In 2005, success rates of 83% were achieved for pediatric AVNRT cryoablation for an international registry. No complications were reported, and, subsequently, the success rate for radiofrequency ablation in the four AVNRT cryoablation failures was 100% with the combined approach. [33] More recent studies have reported the initial success rate for AVNRT to be 96-100% although the recurrence rate remained high at 6-20%. [34, 35, 36, 37]

In a 2010 survey of physicians who were largely invasive pediatric electrophysiologists (94%) who practice at mid- to high-volume centers (>50 ablation procedures/year), 41% of responders use cryoablation as first-line therapy for AVNRT. [38]

One study demonstrated that the fast pathway effective refractory period (ERP) prolongs during AV node modification by cryotherapy, and this can be used as a marker of success. This study indicates that prolongation of more than 20 ms in the fast pathway ERP during cryotherapy application is 70% sensitive and 72% specific for predicting successful slow pathway modification. Subsequent to the procedure, the fast pathway ERP shortens to below baseline levels. [39, 40]

A study of pediatric patients showed a trend toward improved initial success rates (98% vs 93%) and lower early recurrence rates (9% vs 18%) using a 6-mm tip cryoablation catheter as compared with a 4-mm tip catheter. [41] Use of an 8-mm tip cryoablation catheter has also been compared with radiofrequency ablation. [42]

A study in adult patients emphasized the importance of eliminating AH jumps with retrograde atrial (echo) beats in reducing the recurrence rate. [43] The applicability of this finding to the pediatric population is unclear as the typical findings of dual AV nodal physiology described in adult patients are less common in pediatric patients. [22] Persistent single echo beats may be an acceptable endpoint for slow pathway ablation in children. [23] Pediatric patients also exhibit an increased prevalence of inducible atypical arrhythmias. [44]

With the use of radiofrequency energy, the AV node can be modified by ablation of the slow pathway. The approaches to AV node slow pathway modification are generally anatomic (ie, creating a line or lines of block across the usual site of the slow-pathway entrance) or guided by slow-pathway potentials. [45] Successful deliveries of energy often are associated with a smooth and gradual acceleration of junctional tachycardia. [46] AV conduction must be assessed carefully during energy application to ensure that heart block is not created. Successful ablation usually is associated with a loss of the jump in conduction, fewer or no AV nodal echo beats, and failure to reinduce tachycardia.

With cryothermal energy, the advantage of using a moderate temperature cryo map (eg, −30°C) to identify a a target for subsequent full cryoablation (< −70°C) has been partly obscured by the finding that, in some patients, the mapped location does not predict the actual successful site, with a reported negative predictive value of 66% in some series. [47] Also, transient AV block was noted in other patients, where the map has previously shown to be a safe location. So far, no permanent AV block has been described with cryomapping/ablation.

A meta-analysis concluded that cryoablation is a safe and effective treatment. Late recurrences were more common with cryoablation; however, avoidance of AV nodal block was noted. [34] One study showed early transient AV block following cryotherapy in 18% of patients; however, in all patients, there was no evidence of AV nodal dysfunction 24 hours following the procedure. [48] Cryoablation has been shown to be more successful with increased individual experience in one study, in which there was a decreased recurrence rate from 28% in the first 25 cases to 8.9% in the last 45 cases. [35]

Postcatheterization complications include hemorrhage from the sheath access sites, pain, nausea and vomiting, rhythm abnormalities, and arterial or venous obstruction from thrombosis or spasm. Although the long-term sequelae of AVNRT ablation are unknown, one study of pediatric patients has described changes in atrial size and electrophysiology 2-5 years following ablation. [49, 50]

Current electroanatomic mapping systems have led to a significant decrease in fluoroscopy use and thus radiation exposure during electrophysiology studies and ablation. [51, 52] Intracardiac echocardiography has also been used in conjunction with electroanatomic mapping to lower radiation exposure. [53]

Some authors have suggested that cryoablation has a lower recurrence rate when performed at a younger age. [54]

Historically the electrophysiologic signal was equally important to the anatomic location for determination of appropriate ablation targets. However, increased use of high density, three-dimensional, electroanatomic voltage mapping of the Koch triangle has led to the development of observation of areas of low-voltage or voltage gradients, described as low-voltage bridges, which often coincide with areas of successful slow pathway cryoablation. Cryoablation guided by the low-voltage bridge approach has been found to be safe and effective and may result in a lower rate of tachycardia recurrence. [55, 56, 57]

Atrioventricular Node Reentry Supraventricular Tac Atrioventricular Node Reentry Supraventricular Tachycardia. Low voltage bridge in atrioventricular node reentry tachycardia (AVNRT). The images are a three-dimensional electroanatomic voltage map of the right atrium in the left anterior oblique projection with caudal angulation. The purple regions represent areas of high ("normal") atrial electrogram voltage, whereas gray and red regions have lower amplitude signals. The red region projecting from the tricuspid annulus (cutout) posteriorly toward the coronary sinus (thin purple cylinder) is a potential target for slow pathway ablation. The white spherical images are locations where cryotherapy of lesions were performed. The lesion highlighted in yellow represents the location of the successful slow pathway ablation. The others are "insurance" lesions.
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