Twin AV Node and Induced Supraventricular Tachycardia in Fontan Palliation Patients

Catheter Ablation of Atrioventricular Nodal Reentrant Tachycardia in Patients With Congenital Heart Disease

Atrioventricular (AV) nodal reentrant tachycardia represents the most common regular supraventricular arrhythmia in humans, and catheter ablation of the so called slow AV nodal pathway has been effectively performed for decades. In patients with congenital heart disease, a combination of different factors makes catheter ablation of AV nodal reentrant tachycardia substrate particularly challenging, including abnormal venous access to intracardiac structures, abnormal intracardiac anatomy, potentially deviant and often unpredictable sites of the specific conduction system, loss of traditional anatomic landmarks, and congenital cardiac surgery that may complicate the access to the AV nodal area. Published experiences have confirmed the efficacy and the relative safety of such procedures when performed by experts, but the risk of complications, in particular AV block, remains non-negligible. A thorough knowledge and understanding of anatomic and electrical specificities according to underlying phenotype are essential in addressing these complex cases. Considering the major consequences associated with AV block in patients with complex congenital heart disease, particularly those without low risk access for transvenous ventricular pacing (eg, single ventricle physiology or Eisenmenger syndrome), the individual risk-benefit ratio should be carefully evaluated. The decision to defer ablation may be the wisest approach in selected patients with either infrequent or hemodynamically tolerated arrhythmias, or when the location of the AV conduction pathways remains uncertain. This narrative review aims to synthetize existing literature on catheter ablation of AV nodal reentrant tachycardia in congenital heart disease, to present main features of common associated pathologies, and to discuss approaches to mapping and safely ablating the slow AV nodal pathway in challenging cases.

Multicenter Outcomes of Catheter Ablation for Atrioventricular Reciprocating Tachycardia Mediated by Twin Atrioventricular Nodes

OBJECTIVES

This study sought to describe the electrophysiologic properties and catheter ablation outcomes for T-AVRT.

BACKGROUND

Although catheter ablation for atrioventricular (AV) reciprocating tachycardia via twin AV nodes (T-AVRT) is an established entity, there are few data on the electrophysiological properties and outcomes of this procedure.

METHODS

An international, multicenter study was conducted to collect retrospective procedural and outcomes data for catheter ablation of T-AVRT.

RESULTS

Fifty-nine patients with T-AVRT were identified (median age at procedure, 8 years [interquartile range, 4.4-17.0 years]; 49% male). Of these, 55 (93%) were diagnosed with heterotaxy syndrome (right atrial isomerism in 39, left atrial isomerism in 8, and indeterminate in 8). Twenty-three (39%) had undergone Fontan operation (12 extracardiac, 11 lateral tunnel). After the Fontan operation, atrial access was conduit or baffle puncture in 15 (65%), fenestration in 5 (22%), and retrograde in 3 (13%). Acute success was achieved in 43 (91%) of 47 attempts (targeting an anterior node in 23 and posterior node in 24). There was no high-grade AV block or change in QRS duration. Over a median of 3.8 years, there were 3 recurrences. Of 7 patients with failed index procedure or recurrent T-AVRT, 6 (86%) were associated with anatomical hurdles such as prior Fontan or catheter course through an interrupted inferior vena cava-to-azygous vein continuation (P = 0.11).

CONCLUSIONS

T-AVRT can be targeted successfully with low risk for recurrence. Complications were rare in this population. Anatomical challenges were common among patients with reduced short and long-term efficacy, representing opportunities for improvement in procedural timing and planning.

Retrograde sharp potential resembling the his-bundle electrogram: is this a case of atrioventricular re-entrant tachycardia involving twin atrioventricular nodes with the anterior node exhibiting only retrograde conduction?

A 2-year-old male with right isomerism was referred for supraventricular tachycardias. Atrial pacing study revealed that anterograde conduction was only through the posterior atrioventricular node. During the mapping of ventriculoatrial conduction, we identified a sharp potential resembling a His-bundle electrogram with a decremental property at the anterior wall of the common atrium. Catheter ablation for the potential eliminated the anterior ventriculoatrial conduction, thereby indicating retrograde activation of the possible anterior atrioventricular node.

Impact of preoperative electrophysiological intervention on occurrence of peri/postoperative supraventricular tachycardia following Fontan surgery

BACKGROUND

Little is known about the effects of preoperative electrophysiological study (EPS) and catheter ablation (CA) in Fontan surgery candidates with supraventricular tachycardia (SVT).

OBJECTIVE

The purpose of this study was to investigate the clinical impact of EPS-guided intervention in Fontan surgery candidates with preceding SVT events.

METHODS

A total of 109 consecutive patients with a history of SVT before Fontan surgery were divided into 3 groups: 44 in whom EPS with CA was attempted (CA group); 21 in whom EPS without CA was attempted (EPS group); and 44 in whom EPS was not performed (N group). The incidence and diagnosis of SVT, acute success rate of CA, and risk factors of peri/postoperative SVT were retrospectively investigated.

RESULTS

The total incidence of SVT within 1 year after Fontan surgery was 34% (n = 37), with 91% of cases occurring within 1 month. Among the 71 SVT incidences diagnosed with EPS, 31 were atrioventricular reentrant tachycardias (AVRTs) involving twin atrioventricular nodes, 12 were atrioventricular nodal reentrant tachycardias, 12 were atrial tachycardias, 7 were orthodromic AVRTs via the accessory pathway, 7 were atrial flutters, and 2 were junctional tachycardias. The acute success rate of CA was 91% (48/53). The rate of peri/postoperative atrioventricular reciprocating SVT was significantly lower in the CA group than in the N or EPS group (11% vs 43% or 43%; P <.05). No/unsuccessful CA significantly increased the risk of peri/postoperative SVT in multivariate analysis (odds ratio 4.43; 95% confidence interval 1.69-11.59).

CONCLUSION

Preoperative CA reduces peri/postoperative SVT occurrence in Fontan surgery candidates at high risk for SVT.

Magnetic-guided catheter ablation of twin AV nodal reentrant tachycardia in a patient with left atrial isomerism, interrupted inferior vena cana, and Kawashima-Fontan procedure

Twin AV nodal reentrant tachycardia most commonly occurs in patients with complex congenital heart disease who have two distinct AV nodes, His bundles, and non‐preexcited QRS morphologies. Catheter ablation of the weaker AV node may be hindered by anatomical complexities. In such cases, remote magnetic guidance offers a potentially effective solution.

Introduction to the Congenital Heart Defects: Anatomy of the Conduction System

The position and course of the conduction system in congenital heart disease are intricately tied to the underlying congenital malformation. Although only subtle differences exist between the anatomy of the conduction axis for simple congenital heart lesions and normal anatomy, almost every patient with congenital heart disease harbors some important anatomic variation. This article summarizes the body of literature by retaining original classical concepts and by attempting to translate the available knowledge into useful points for the congenital heart disease specialist. This discussion spans the entire spectrum of simple to complex congenital heart disease.

Intraoperative Three-Dimensional Mapping of Supraventricular Tachycardia in a Young Fontan Patient

Preoperative tachycardia is uncommon before an initial Fontan procedure. Catheter intervention can risk complications in small patients. A patient with fetal tachycardia and double inlet left ventricle underwent Norwood and bidirectional Glenn procedures. She had persistent tachycardia. A three-dimensional electroanatomic mapping system was modified for the operative procedure; it was used to identify the arrhythmia substrate and cryoablate an atrioventricular nodal tachycardia. Mapping added 20 minutes to the operation. She is arrhythmia-free and off medication after 4 months. This three-dimensional system was successfully adapted for an intraoperative SVT ablation in this small patient, and it may be useful in other settings.

Electrophysiology Study for Complex Supraventricular Tachycardia in Congenital Heart Disease Patients With Single-Ventricle Physiology

BACKGROUND

Supraventricular tachycardia (SVT) is common in complex congenital heart disease (CCHD) patients with single-ventricle physiology and may cause hemodynamic deterioration. We reported the outcomes of catheter ablation for such complex SVT in these single-ventricle CCHD patients.

METHODS AND RESULTS

Patients with single-ventricle physiology (defined as CCHD patients) who received electrophysiology studies and catheter ablation between 1995 and 2015 were studied. We enrolled 30 CCHD patients (18 with right atrial isomerism, 5 with left atrial isomerism, and 7 with other CCHDs; 17 male, 13 female). The age of onset of clinical SVT was 6.7 years (±4.7 years). Electrophysiology studies and ablation were performed at age 7.1 years (±3.9 years); body weight was 20.7 kg (±10.0 kg). Twin atrioventricular nodes were present in 60% of patients (right atrial isomerism, 72.2%; left atrial isomerism, 40%; other CCHDs, 42.9%). Manifested preexcitation was noted in 10% of patients. SVT was induced in 21 patients. Twin atrioventricular nodal reentrant tachycardia was the most common (57.1%), followed by atrioventricular reentrant tachycardia (28.6%), junctional tachycardia (14.3%), and atrioventricular nodal reentrant tachycardia (9.5%). Multiple arrhythmias were common (33.3%), particularly in patients with atrioventricular reentrant tachycardia (50%). Ablation successfully eliminated SVT in 12 of 14 patients (85.7%), with a recurrence rate of 16.7% during 6 years of follow-up.

CONCLUSIONS

Transcatheter ablation of complex SVT substrates, including minor atrioventricular node of twin atrioventricular nodal reentrant tachycardia, accessory pathways of atrioventricular reentrant tachycardia, and a slow pathway of atrioventricular nodal reentrant tachycardia, is effective in CCHD patients. The limitations are limited vascular access and the risk of atrioventricular block.

Efficacy of landiolol for the treatment of junctional ectopic tachycardia resulting from sepsis

Junctional ectopic tachycardia, after surgery for CHD, is a serious arrhythmia that can cause increased morbidity and mortality. We report a case of junctional ectopic tachycardia, preceded by sepsis, in a 4-year-old girl, 31 months after open-heart surgery. She was successfully treated using low-dose landiolol hydrochloride.

Successful radiofrequency catheter ablation of sinoatrial nodal reentrant tachycardia after a total cavo-pulmonary connection procedure with an extra-cardiac conduit

We report a tachyarrhythmia case of a 32-year-old female with a single ventricle and heterotaxy syndrome. She had surgery involving a total cavo-pulmonary connection procedure using an extra-cardiac conduit (EC) at the age of 17 years. A tachycardia was repetitively induced with single atrial extrastimuli. An activation map was created revealing a centrifugal propagation pattern from the high atrial wall adjacent to the EC. At that site, a structure resembling the crista terminalis was recognized with intracardiac echocardiography. Therefore, high output energy was required to eliminate the tachycardia. It was thought to be a sinoatrial nodal reentrant tachycardia. <Learning objective: Radiofrequency catheter ablation (RFCA) of supraventricular tachycardia (SVT) after a total cavo-pulmonary connection with an extra-cardiac conduit is challenging and the diagnosis of the SVT is difficult. However the electrophysiological features observed during the electrophysiological study using a three-dimensional mapping system, anatomical features observed with intracardiac echocardiography, and pharmacological features seen during a rapid intravenous injection of adenosine triphosphate can lead to an accurate diagnosis, and moreover lead to a successful RFCA.>.

Anatomic Challenges In Pediatric Catheter Ablation

Pediatric patients present unique anatomic challenges for catheter ablation. Small patient size requires special adaptation and understanding to perform safe procedures when clinically indicated. The anatomic variations of congenital heart disease also create problems that require pre-procedural preparation for each case in addition to a specialized understanding of a vast anatomic variation and surgical repairs. This understanding coupled with the knowledge of the pathophysiology of arrhythmia disorders and the biophysics of catheter ablation technology are required to perform successful and safe ablation procedures in this special population.

The conduction system in heterotaxy

Cardiac malformations associated with the syndrome of atriovisceral heterotaxy are among the most complex forms of congenital heart disease. Accordingly, the disposition of the specialized conduction tissue (the conduction system) is also variable and complex in these particular anomalies. The location of the conduction system and the degree of abnormalities of the conduction system correlate with the severity and location of the associated structural cardiac anomalies.

Magnetic navigation in adults with atrial isomerism (heterotaxy syndrome) and supraventricular arrhythmias

AIMS

We analysed the type and mechanism of supraventricular arrhythmias encountered in a series of symptomatic adults with atrial isomerism undergoing catheter ablation procedures.

METHODS AND RESULTS

The study population included consecutive adults with atrial isomerism who had previously undergone surgical repair or palliation of the associated anomalies. Patients underwent electrophysiological study for symptomatic arrhythmia in our institution between 2010 and 2012 using magnetic navigation in conjunction with CARTO RMT and three-dimensional (3D) image integration. Eight patients (five females) with a median age of 33 years [interquartile range (IQR) 24-39] were studied. Access to the cardiac chambers of interest was obtained retrogradely via the aorta using remotely navigated magnetic catheters in six patients. Radiofrequency ablation successfully targeted twin atrioventricular (AV) nodal reentrant tachycardia in two patients, atrial fibrillation (AF) in three, focal atrial tachycardia (AT) mainly originating in the left-sided atrium in four patients, and macro-reentrant AT dependent on a right-sided inferior isthmus in three patients. The median fluoroscopy time was 3.0 min (IQR 2-11). After a median follow-up of 10 months (IQR 6-21), five of the ablated patients are free from arrhythmia; two patients experienced episodes of self-terminated AF and AT, respectively, within one month post-ablation; the remaining patient had only non-sustained AT during the electrophysiological study and was managed medically.

CONCLUSION

Various supraventricular tachycardia mechanisms are possible in adults with heterotaxy syndrome, all potentially amenable to radiofrequency ablation. The use of remote magnetic navigation along with 3D mapping facilitated the procedures and resulted in a short radiation time.

Late Arrhythmias Following Fontan Surgery

The incidence of atrial arrhythmias following Fontan repairs varies by the type of surgery and duration of follow-up. The incidence of late atrial tachycardia has been reduced from 60% to less than 20% by surgical modifications. Late ventricular tachycardia is reported in 3% to 12% of patients. Aggressive efforts to eliminate tachycardia and improve hemodynamics may improve clinical status.

A mouse model of conduction system patterning abnormalities in heterotaxy syndrome

Duplication or absence of parts of the specialized cardiac conduction system in patients with heterotaxy syndrome causes significant clinical disease, but the mechanistic basis by which embryonic disruption of left-right patterning alters conduction system patterning in these patients is not well understood. We sought to determine whether a mouse model of X-linked human heterotaxy recapitulates conduction system abnormalities identified in patients with heterotaxy. Cardiac structure and conduction system patterning were evaluated in Zic3 null embryos from e9.5 to e16.5 using genetic and molecular methods. Severe structural abnormalities involving atrial, ventricular, and conotruncal development were associated with a spectrum of disorganized and ambiguous arrangements throughout the conduction system, including the appearance of duplicated structures. The severity and location of conduction system abnormalities correlated with the severity and location of associated structural heart disease and were identifiable at the earliest stages examined. The Zic3 mouse model provides a novel tool to dissect the mechanistic underpinnings of conduction system patterning and dysfunction and its relationship to cardiovascular malformations, making it a promising model to improve understanding and risk assessment in the clinical arena.

Nodoventricular pathway associated with twin AV nodes: complexity of ablation in single ventricle physiology

We report the case of a patient with heterotaxy syndrome including complex single ventricular morphology and interrupted IVC in association with twin conduction systems and a nodoventricular accessory pathway connection. The presence of 3 distinct QRS morphologies was inadvertently discovered during a hemodynamic catheterization study and prompted formal EP testing prior to hepatic venous inclusion into the Fontan circuit and loss of access to the atrial chamber for testing and therapy. This patient underscores the importance of close surveillance and high index of suspicion of arrhythmia mechanisms in patients with heterotaxy syndrome in conjunction with single ventricle morphology.

Diagnosis of postoperative arrhythmias following paediatric cardiac surgery

Arrhythmias are commonly encountered in the paediatric intensive care unit setting, most frequently in the setting of postoperative congenital heart disease. Postoperative arrhythmias are an important cause of morbidity in children in the postoperative period following cardiac surgery for congenital cardiac lesions. It is important for all paediatric critical care physicians involved in the care of these children to understand the potential mechanisms involved and how to make an accurate diagnosis. The existing literature has focused on small groups and specific arrhythmias. There is a paucity of literature to guide the clinician in approaching arrhythmias in the paediatric intensive care unit setting. Our objective was to review the recognition and diagnosis of paediatric arrhythmias in the postoperative period following congenital cardiac surgery. Timely and accurate identification of the rhythm disturbance is mandatory and allows for the institution of effective, rhythm specific management strategies.

Accessory pathway reciprocating tachycardia involving twin AV nodes in a patient with atrioventricular discordance and mitral atresia

The atrioventricular (AV) conduction system in AV discordance remains unclear, especially in cases with complex cardiac anomaly. We report a case of accessory pathway reciprocating tachycardia in atrioventricular discordance (AVD) and mitral atresia with twin AV nodes. In this case, the anterior AV node was located along the atretic mitral valve. The anterior AV node was involved in tachycardia and the posterior AV node acted as a bystander during tachycardia. The anterior AV node in AVD can be located along the atretic mitral valve, and one of twin AV nodes might act as a bystander during AV reciprocating tachycardia.

Long-term outcome of twin atrioventricular node and supraventricular tachycardia in patients with right isomerism of the atrial appendage

BACKGROUND

Twin AV nodes and resulting supraventricular tachycardia (SVT) have been described in right atrial isomerism (RAI).

OBJECTIVE

We sought to analyze the long-term outcome of patients with RAI with a focus on rhythm disturbances.

METHODS

Retrospective study of 257 patients (152 male and 105 female, 1,171 patient-years) with RAI diagnosed between 1980 and 2005.

RESULTS

SVT in 68 patients (26%) occurred at various ages from the prenatal period to 15 years and was only significantly associated with balanced ventricles (P = .009). Cardioversion was achieved in by verapamil in 6 of 6 cases (100%), adenosine in 18 of 21 cases (88%) and propranolol in 10 of 12 cases (83%). Electrocardiographic evidence of twin AV nodes, as shown by 2 discrete non-pre-excited QRS complexes, was found in 28 of 44 (64%) patients with more than 2 electrocardiograms, and was more frequent in those with balanced ventricles rather than a dominant ventricle and would increase risk of SVT. Recurrence of SVT was documented in 27 (40%) patients 1 day to 4.5 years after the first episode. However, the occurrence or recurrence of SVT was not associated with increased all-cause or surgical mortality or sudden death. Successful catheter ablation of ventriculoatrial pathways with junctional ectopic tachycardia at radiofrequency energy delivery was obtained in 5 of 6 patients.

CONCLUSION

This study showed that twin AV nodes in RAI patients could be disclosed by serial electrocardiograms and that SVT, most likely a twin node tachycardia, was common and tended to recur but could be managed by ablation or medication.

Pediatric radiofrequency catheter ablation: results of initial 100 consecutive cases including congenital heart anomalies

Radiofrequency catheter ablation (RFCA) has recently become a management option for pediatric tachycardia. We reviewed the records of a total of 100 patients (aged 10 months to 19 yr) who had undergone RFCA, from March 2000 to June 2004. Types of arrhythmia (age, acute success rate) were as follows: atrioventricular reentrant tachycardia (AVRT, 9.0+/-3.7 yr, 66/67), atrioventricular nodal reentrant tachycardia (AVNRT, 13+/-2.5 yr, 16/16), ectopic atrial tachycardia (6.4+/-3.3 yr, 5/5), junctional ectopic tachycardia (10 month, 1/1), ventricular tachycardia (12+/-4.9 yr, 6/6), postsurgical intraatrial reentrant tachycardia (15.6+/-4.1 yr, 2/3), twin node tachycardia (4 yr, 0/1), and His bundle ablation (9 yr, 1/1). The age of AVNRT was older than that of AVRT (p=0.002). Associated cardiac disease was detected in 17 patients, including 6 univentricular patients, and 3 Ebstein's anomaly patients. RFCA for multiple accessory pathways required longer fluoroscopic times than did the single accessory pathway (53.9+/-4.8 vs. 36.2+/-24.1 min; p=0.03), and was associated with a higher recurrence rate (3/9 vs. 3/53; p=0.03). Regardless of the presence or absence of cardiac diseases, the overall acute success rate was 97% without major complications, the recurrence rate was 8.2%, and the final success rate was 97%. This experience confirmed the efficacy and safety of RFCA in the management of tachycardia in children.