High-density mapping of Koch's triangle during sinus rhythm and typical AV nodal reentrant tachycardia: new insight

Beyond the lens: Unveiling the invisible atrioventricular node in the era of high-density mapping

Numerous studies have clarified the histological characteristics of the area surrounding the atrioventricular (AV) node, commonly referred to as the triangle of Koch (ToK). Although it is suggested that the conduction of electric impulses from the atria to the ventricles via the AV node involves myocytes possessing distinct conduction properties and gap junction proteins, a comprehensive understanding of this complex conduction has not been fully established. Moreover, although various pathways have been proposed for both anterograde and retrograde conduction during atrioventricular nodal reentrant tachycardia (AVNRT), the reentrant circuits of AVNRT are not fully elucidated. Therefore, the slow pathway ablation for AVNRT has been conventionally performed, targeting both its anatomical location and slow pathway potential obtained during sinus rhythm. Recently, advancements in high-density three-dimensional (3D) mapping systems have facilitated the acquisition of more detailed electrophysiological potentials within the ToK. Several studies have indicated that the activation pattern, the low-voltage area within the ToK obtained during sinus rhythm, and the fractionated potentials acquired during tachycardia may be optimal targets for slow pathway ablation. This review provides an overview of the tissue surrounding the AV node as reported to date and summarizes the current understanding of AV conduction and AVNRT circuits. Furthermore, we discuss recent findings on slow pathway ablation utilizing high-density 3D mapping systems, exploring strategies for optimal slow pathway ablation.

A novel approach to typical atrioventricular nodal reentrant tachycardia with high-resolution mapping using the CARTO 3 cardiac mapping system

BACKGROUND

We hypothesized that high-resolution activation mapping during sinus rhythm (SR) in Koch's triangle (KT) can be used to describe the most delayed atrial potential around the atrioventricular node and evaluated whether ablation targeting of this potential is safe and effective for the treatment of patients with typical atrioventricular nodal reentrant tachycardia (AVNRT).

METHODS

We conducted a prospective, non-randomized, observational study using high-resolution activation mapping from the sinus node to KT with a PENTARAY or OCTARAY catheter using the CARTO 3 cardiac mapping system (Biosense Webster) during SR in 62 consecutive patients (22 men; age [mean ± standard deviation] = 55 ± 14 years) treated for typical AVNRT at our institution from August 2021 to March 2023.

RESULTS

In all cases, the most delayed atrial potential was observed near the His potential within KT. Ablation targeting of this potential helped successfully treat each case of AVNRT, with a junctional rhythm observed at the ablation site. Initial ablation was deemed successful in 55/62 patients (89%); in the remaining seven patients, lesion expansion resolved AVNRT. One procedural complication occurred, namely, a transient atrioventricular block lasting 45 s. One patient experienced a transient tachycardic episode by the 1-month follow-up, but no further episodes were noted up to the 1-year follow-up.

CONCLUSION

Activation mapping at KT during SR with the high-resolution CARTO system clearly revealed the most delayed atrial potential near the His potential within KT. Targeting this potential was a safe and effective treatment method for patients with typical AVNRT in our study.

Relationship between the atrial-activation pattern around the triangle of Koch and successful ablation sites in slow-fast atrioventricular nodal reentrant tachycardia

Background

The precise details of atrial activation around the triangle of Koch (ToK) remain unknown. We evaluated the relationship between the atrial-activation pattern around the ToK and success sites for slow-pathway (SP) modification ablation in slow-fast atrioventricular reentrant tachycardia (AVNRT).

Methods

Thirty patients with slow-fast AVNRT who underwent successful ablation were enrolled. Atrial activation around the ToK during sinus rhythm was investigated using ultra-high-density mapping pre-ablation. The relationships among features of atrial-activation pattern and success sites were examined.

Results

Of 30 patients (22 cryoablation; 8 radiofrequency ablation), 26 patients had a collision site of two wavefronts of delayed atrial activation within ToK, indicating a success site. The activation-search function of Lumipoint software, which highlights only atrial activation with a spatiotemporal consistency, showed non-highlighted area on the tricuspid-annulus side of ToK. In 23 of the patients, a spiky potential was recorded at that collision site outside the Lumipoint-highlighted area. Fifteen cryoablation patients with a success site coincident with a collision site outside the Lumipoint-highlighted area had significantly more frequent disappearances of SP after initial cryoablation (46.7% vs. 0%, p = .029), fewer cryoablations (3.7 ± 1.8 vs. 5.3 ± 1.3, p = .045), and shorter procedure times (170 ± 57 vs. 228 ± 91 min, p = .082) compared to the seven cryoablation patients without such sites. Four patients had transient AV block by ablation inside the Lumipoint-highlighted area with fractionated signals, but no patient developed permanent AV block or recurrence post-procedure (median follow-up: 375 days).

Conclusions

SP modification ablation at the collision site of atrial activation of the tricuspid-annulus side along with a spiky potential could provide a better outcome.

High-resolution mapping of the circuit of typical atrioventricular nodal reentrant tachycardia

BACKGROUND

Recent anatomic and electrophysiologic evidence has provided new insight into the anatomic substrate. Previous reports on electroanatomic mapping (EAM) of the circuit of atrioventricular nodal reentrant tachycardia (AVNRT) have been limited by mapping only the triangle of Koch on the right side of the septum and by the use of conventional mapping tools. The objectives are to obtain comprehensive high-resolution mapping of typical AVNRT and to investigate the role of the atrioventricular ring tissues in the circuit.

METHODS

We employed EAM with the use of novel modules and algorithms for studying typical AVNRT from the right and the left sides of the septum.

RESULTS

We performed extensive mapping of both the atrial septum and the septal vestibule of the tricuspid valve during typical AVNRT in 9 (6 females) patients, aged 49.6 ± 12.1 years. In two of these, left septal mapping was also obtained through the aorta. The earliest initial activation was variable, emanating from the superior or medial septum. The impulse consistently appeared below the orifice of the coronary sinus, at the site where its inferoanterior margin merged with the septal vestibule of the tricuspid valve at its entrance to the right atrium. It then returned to the initial activation site, presumably through the septal vestibular myocardium. The left septal activation area corresponded to that recorded on the right side.

CONCLUSIONS

Typical AVNRT uses a circuit confined within the pyramid of Koch from the AV node to the septal isthmus, involving the myocardial walls of the pyramidal space.

High-density mapping of Koch's triangle during sinus rhythm and typical atrioventricular nodal re-entrant tachycardia, integrated with direct recording of atrio-ventricular node structure potential

BACKGROUND

The mechanism of typical slow-fast atrioventricular nodal re-entrant tachycardia (AVNRT) and its anatomical and electrophysiological circuit inside the right atrium (RA) and Koch's Triangle (KT) are not well known.

OBJECTIVE

To identify the potentials of the compact AV node and inferior extensions and to perform accurate mapping of the RA and KT in sinus rhythm (SR) and during AVNRT, to define the tachycardia circuit.

METHODS

Consecutive patients with typical AVNRT were enrolled in 12 Italian centers and underwent mapping and ablation by means of a basket catheter with small electrode spacing for ultrahigh-density mapping and a modified signal-filtering toolset to record the potentials of the AV nodal structures.

RESULTS

Forty-five consecutive cases of successful ablation of typical slow-fast AVNRT were included. The mean SR cycle length (CL) was 784.1 ± 6 ms and the mean tachycardia CL was 361.2 ± 54 ms. The AV node potential had a significantly shorter duration and higher amplitude in sinus rhythm than during tachycardia (60 ± 40 ms vs. 160 ± 40 ms, p < .001 and 0.3 ± 0.2 mV vs. 0.09 ± 0.12 mV, p < .001, respectively). The nodal potential duration extension was 169.4 ± 31 ms, resulting in a time-window coverage of 47.6 ± 9%. The recording of AV nodal structure potentials enabled us to obtain 100% coverage of the tachycardia CL during slow-fast AVNRT.

CONCLUSION

Detailed recording of the potentials of nodal structures is possible by means of multipolar catheters for ultrahigh-density mapping, allowing 100% of the AVNRT CL to be covered. These results also have clinical implications for the ablation of right-septal and para-septal arrhythmias.

Activation pattern within Koch's triangle during sinus rhythm in patients with and without atrioventricular nodal reentrant tachycardia

BACKGROUND

Several studies have visualized the slow pathway during sinus rhythm using high-density mapping of Koch's triangle (KT) in patients with atrioventricular nodal reentrant tachycardia (AVNRT). However, it is unclear whether the slow pathway can be visualized in all people. Therefore, we evaluated the activation pattern within KT during sinus rhythm in patients with and without AVNRT.

METHODS

High-density mapping using the Advisor HD Grid mapping catheter (Abbott) within KT during sinus rhythm was created in 10 patients with slow-fast AVNRT and 30 patients without AVNRT.

RESULTS

In 8 (80%) patients with AVNRT, the activation pattern pivoting around a block line (BL) within KT was observed. In 12 (40%) patients without AVNRT, similar activation pattern pivoting around BL was observed, but jump was observed in 11 (92%) of these patients. In all patients, the activation pattern pivoting around BL was observed in 17 (85%) of 20 patients with jump, but only 3 (15%) of 20 patients without jump (p < 0.0001). During jump, there was a long period of no potential from the last atrial potential within KT to the His bundle potential, suggesting the slow pathway conduction through the rightward inferior extension that cannot be visualized. A linear ablation between the pivot point and the septal tricuspid annulus was successful for slow-fast AVNRT.

CONCLUSION

Although the slow pathway could not be visualized using high-density mapping during sinus rhythm, the activation pattern pivoting around BL within KT was observed in most patients with the dual pathway physiology, with or without AVNRT.

Combination of Slow Pathway Late Activation Maps and Voltage Gradient Maps in Guidance of Atrioventricular Nodal Reentry Tachycardia Cryoablation

BACKGROUND

The optimal strategy for electroanatomic mapping-guided cryoablation of atrioventricular nodal reentry tachycardia (AVNRT) remains unclear.

OBJECTIVE

To investigate the effectiveness of slow pathway late activation mapping (SPLAM) and voltage gradient mapping for AVNRT cryoablation.

METHODS

From June 2020 to February 2022, all consecutive patients with AVNRT underwent SPLAM to define the wave collision point and voltage gradient mapping to define the low voltage bridge (LVB). Conventional procedures performed from August 2018 to May 2020 served as control.

RESULTS

The study and control groups comprised 36 (aged 16.5±8.2 years) and 37 patients (aged 15.5±7.3 years), respectively. Total procedural times were comparable, and acute success rates were 100% in both groups. Compared to controls, number of cryomapping attempts (median 3 vs. 5, p=0.012) and cryoablation applications (median 1 vs. 2, p<0.001) were significantly lower in the study group. At a median follow-up of 14.6 and 18.3 months, recurrence rates were 5.6% (2 patients) and 10.8% (4 patients) in the study and control groups (p=0.402), respectively. Mapping of Koch's triangle took 11.8±3.6 min, in which 1562±581 points were collected. In SPLAM, wave collision points were defined and compatible with the final successful lesion sites in all patients, including those with multiple slow pathways. LVB could not be defined in 6 patients (16.7%), and LVB was not compatible with the final successful lesion in another 6 (16.7%).

CONCLUSIONS

For AVNRT cryoablation, SPLAM could effectively guide the localization of slow pathway ablation sites and was particularly beneficial in patients with multiple slow pathways.

High-density electro-anatomical activation mapping to guide slow pathway modification in patients with persistent left superior vena cava

BACKGROUND

Slow pathway (SP) mapping and modification can be challenging in patients with persistent left superior vena cava (PLSVC) due to anatomical variance of Koch's triangle (KT) and coronary sinus (CS) dilatation. There is a lack of studies using detailed 3-dimensional (3D) electro-anatomical mapping (EAM) to investigate conduction characteristics and guide ablation targets in this condition.

OBJECTIVES

To describe a novel technique of slow pathway mapping and ablation in sinus rhythm using 3D EAM in patients with PLSVC after validation in a cohort with normal coronary sinus anatomy.

METHODS

Seven patients with PLSVC and dual AV node physiology who underwent slow pathway modification with the use of 3D EAM were included. Twenty-one normal heart patients with AV nodal re-entrant tachycardias formed the validation group. High-resolution, ultra-high-density local activation timing (LAT) mapping of the right atrial septum and proximal coronary sinus in sinus rhythm was performed.

RESULTS

SP ablation targets were consistently identified by an area in the right atrial septum with the latest activation time and multi-component atrial electrogram (EGM) adjacent to a region with isochronal crowding (deceleration zone). In PLSVC patients, these targets were located at or within 1 cm of the mid anterior CS ostium. Ablation in this area led to successful SP modification reaching standard clinical endpoints with a median of 43 sec of radio frequency energy or 14 mins of cryoablation without complications.

CONCLUSION

High-resolution activation mapping of Koch's triangle in sinus rhythm can facilitate localisation and safe slow pathway ablation in patients with PLSVC.

New insights into atrioventricular nodal anatomy, physiology, and immunochemistry: A comprehensive review and a proposed model of the slow-fast atrioventricular nodal reentrant tachycardia circuit in agreement with direct potential recordings in the Koch's triangle area

Atrioventricular nodal reentrant tachycardia (AVNRT) is the most frequent regular tachycardia in humans. In this review, we describe the most recent discoveries regarding the anatomical, physiological, and molecular biological features of the atrioventricular junction that could underlie the typical slow-fast AVNRT mechanisms, as these insights could lead to the proposal of a new theory concerning the circuit of this arrhythmia. Despite several models have been proposed over the years, the precise anatomical site of the reentrant circuit and the pathway involved in the slow-fast AVNRT have not been conclusively defined. One possible way to evaluate all the hypotheses regarding the nodal tachycardia circuit in humans is to map this circuit. Thus, we tried to identify the slow potential of nodal and inferior extension structures by using automated mapping of atrial activation during both sinus rhythm and typical slow-fast AVNRT. This constitutes a first step toward the definition of nodal area activation in sinus rhythm and during slow-fast AVNRT. Further studies and technical improvements in recording the potentials of the atrioventricular node structures are necessary to confirm our initial results.

Slow-Pathway Visualization by Using Panoramic View: A Novel Ablation Technique for Ablation of Atrioventricular Nodal Reentrant Tachycardia

(1) Background: The panoramic view of a novel wide-band dielectric mapping system could show the individual anatomy. We aimed to compare the feasibility, efficacy and safety of the panoramic view guided approach for ablation of AVNRT with the conventional approach. (2) Methods: Ablation distributions in eight patients were retrospectively analyzed using the panoramic view. The para-slow-pathway (para-SP) region was divided into three regions, and the region that most frequently appeared with the appropriate junctional rhythm or eliminated the slow-pathway was defined as the adaptive slow-pathway (aSP) region. Twenty patients with AVNRT were then ablated in the aSP region under the panoramic view and compared with 40 patients using the conventional approach. (3) Results: Thirty ablation points were analyzed. The majority of effective points (95.0%) were located in the inferior and anterior portions of the para-SP region and defined as the aSP region. Baseline characteristics, fluoroscopic duration, and mean number of ablations were similar among the two groups. The panoramic view group had a significantly higher percentage of appropriate junctional rhythm (81.9% ± 26.0% vs. 55.7% ± 30.5%, p = 0.002) than the conventional group. (4) Conclusions: The use of the panoramic view for AVNRT ablation achieved similar clinical endpoints with higher ablation efficiency than the conventional approach.