Left Septal Slow Pathway Ablation for Atrioventricular Nodal Reentrant Tachycardia

Upper common pathway analysis using late atrial premature depolarization in atrioventricular nodal reentry tachycardia

BACKGROUND

Anatomic and electrophysiologic findings suggest that the actual circuit of atrioventricular nodal reentrant tachycardia (AVNRT) involves the perinodal atrium. However, occasional instances in which the atrium is dissociated from the AVNRT have led to the concept of an upper common pathway (UCP).

OBJECTIVE

We aimed to assess the prevalence of UCP in AVNRT using a late atrial premature depolarization (LAPD) maneuver.

METHODS

Patients who were diagnosed with typical AVNRT by electrophysiologic studies were enrolled. For evaluation of the presence of UCP, an LAPD was given at the coronary sinus ostium (osCS) during AVNRT, and then pacing was repeated incrementally every 10 ms. Electrograms in the earliest retrograde atrial activation site (ERAS) near the proximal His were mapped and recorded during the pacing. Results were interpreted as follows: absence of UCP-an LAPD from the osCS can reset the tachycardia without depolarizing the ERAS; presence of UCP-an LAPD from the osCS can depolarize the ERAS without resetting the tachycardia; and indeterminate-an LAPD from the osCS either resets the ERAS and tachycardia simultaneously or does not reset both.

RESULTS

The LAPD maneuver was performed in 126 patients with AVNRT. It demonstrated an absence of UCP in 121 (96.0%) patients and the presence of UCP in 3 (2.4%) patients; the result was indeterminate in 2 (1.6%) patients.

CONCLUSION

The LAPD maneuver revealed that the presence of UCP is indicated in only rare cases of AVNRT. In most AVNRT cases, the atrium is involved in the reentry circuit.

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.

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.

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.

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.

Quantitative assessment of the fast pathway in atrioventricular nodal reentrant tachycardia

BACKGROUND

Mathematical modelling has allowed calculation of the length of the slow and fast pathways in typical atrioventricular nodal reentrant tachycardia (AVNRT). The length of the slow pathway has been correlated with the measured length of the right inferior extension in human histologic specimens, but no histology data exist about the fast pathway.

METHODS

In preparations of cadaveric human hearts, the AV node was identified, and the site of the fast pathway was projected according to both existing evidence and results of our electroanatomic mapping. This permitted measurement of the length of the fast pathway as a limb of the tachycardia circuit.

RESULTS

Measurements of the length of the projected area of the fast pathway on histology specimens were performed in 8 hearts. The estimated length of the fast pathway was 39.6 ± 5.8 mm (range: 30.4-45.9 mm). These numbers are comparable to those produced by mathematical calculations of the length of the fast pathway.

CONCLUSIONS

Typical AVNRT uses a circuit from the AV node to the septal isthmus of an average size of 5-6 cm, confined within the pyramid of Koch.

Anatomy for ablation of atrioventricular nodal reentry tachycardia and accessory pathways

The atrioventricular (AV) valve plane and the central septum are of particular importance for electrophysiological diagnosis and interventional therapy of supraventricular tachycardias because accessory electrical connections of various types may be present in addition to the specific conduction system. Although modern 3D electroanatomic reconstruction systems including high-density mapping can be of great assistance, detailed knowledge of the anatomic structures involved, their complex three-dimensional arrangement, and their electrical properties in conjunction with electrophysiological features of supraventricular arrhythmias is essential for safe and efficient electrophysiological treatment. The aim of this article is to present current anatomical, topographical, and electrophysiological findings against the background of historical, seminal, and still indispensable literature.

Catheter ablation via the left atrium for atrioventricular nodal reentrant tachycardia: A narrative review

Background

Since 1996, it has been recognized that catheter ablation for atrioventricular nodal reentrant tachycardia (AVNRT) may require an approach through the left atrium.

Objective

The purposes are to present a case report and to provide a comprehensive narrative review on this topic.

Methods

A literature review of all articles that provided detailed information on patients who underwent catheter ablation via the left atrium for AVNRT was performed. The primary search queried PubMed using Medical Subject Headings (MeSH) terms "atrioventricular nodal reentrant tachycardia" and "left." The secondary search was performed by manual review of reference lists and Google Scholar citations of manuscripts retrieved by the primary search. The review was limited to the English language.

Results

The searches yielded 30 articles that described 79 patients. A case report was added. Therefore, the final review consisted of 80 patients. The prevalence of left atrial ablation for patients with AVNRT undergoing catheter ablation at tertiary care centers was approximately 1%. Failed right atrial ablation, with or without coronary sinus ablation, was the most common indication for left atrial ablation. Pooled data from 3 cohort studies estimated the acute success rate for radiofrequency ablation of the slow pathway at the septal or inferoparaseptal segments of the mitral valve annulus after failed right-sided ablation to be 90%. There were no reports of atrioventricular block requiring permanent pacemaker implantation.

Conclusion

Catheter ablation of the slow pathway via the left atrium is an important technique for AVNRT cases that are refractory to conventional ablation.

Left sided ablation for Atrioventricular Nodal Re-entrant Tachycardia: Frequency, Characteristics and Outcomes

Background

Left-sided ablation, targeting left inferior AV nodal extensions, is thought to be necessary for success in a small proportion of atrioventricular nodal re-entrant tachycardia (AVNRT) ablations; however Indian data are scarce in this regard.

Methods

Consecutive cases of AVNRT undergoing slow pathway ablation in a single centre over an 18-month period were retrospectively analyzed. Left-sided ablation at the posteroseptal mitral annulus was performed if right-sided ablation failed to abolish AVNRT.

Results

From January 2017 to June 2018, out of 215 consecutive supraventricular tachycardia (SVT) cases, 154 (71.6%) were AVNRT (47.1 ± 13.1 years, 46.1% male). Trans-septal ablation was required in 5 (3.2%) cases (mean age 48.8 ± 9.4 years; 4 female, 1 male); all with typical (slow-fast) form of AVNRT. Compared with cases needing only right-sided ablation, radiofrequency time (50.8 ± 16.9 vs. 9.9 ± 8.5 min; p = 0.005) and procedure time (166.0 ± 35.0 vs 79.6 ± 35.9 min; p = 0.004) were significantly longer for trans-septal cases, while baseline intervals and tachycardia cycle length were not significantly different. Junctional ectopy was seen in only 2 of the 5 cases during left-sided ablation, but acute success (non-inducibility) was obtained in 3 cases. There were no instances of AV block. Over mean follow-up of 12.2 ± 4.0 months, clinical recurrence of AVNRT occurred in one case, while others remained arrhythmia-free without medication.

Conclusion

Left-sided ablation was required in a small proportion of AVNRT ablations. Trans-septal approach targeting the posteroseptal mitral annulus was safe and yielded good mid-term clinical success.

A unified theory for the circuit of atrioventricular nodal re-entrant tachycardia

Atrioventricular nodal re-entrant tachycardia (AVNRT) is the most common regular tachycardia in the human, but its exact circuit remains elusive. In this article, recent evidence about the electrophysiological characteristics of AVNRT and new data on the anatomy of the atrioventricular node, are discussed. Based on this information, a novel, unified theory for the nature of the circuit of the tachycardia is presented.

Treatment of left-sided extension of AV node: A valuable integration of advance imaging modalities and cryoablation

We present a case of successful cryoablation of the left extension of the atrioventricular (AV) node for treatment of a recurrent atrioventricular nodal reentry tachycardia without the use of fluoroscopy. Three-dimensional electroanatomic mapping system and intracardiac echocardiography were used to navigate catheters in the heart and position them according to anatomical landmarks. Due to the nature of cryoablation lesion formation, lesions were able to be applied safely in right atrium, as well as in left atrium, without damaging AV node or bundle of His.

Simple differential entrainment screens ablation strategy for slow-fast atrioventricular nodal reentrant tachycardia

BACKGROUND

Ablation of slow-fast atrioventricular nodal reentrant tachycardia (S/F-AVNRT) is occasionally refractory. We hypothesized that the site of ablation for curing S/F-AVNRT can be screened by simple differential atrial entrainment pacing (EP) from the high right atrium (HRA) and proximal coronary sinus (prox-CS).

METHODS

We enrolled 43 patients with S/F-AVNRT who underwent successful differential atrial EP followed by successful ablation of slow pathway (SP) using step-wise approach, and compared the atrio-His (A-H) interval at the recording of His bundle immediately after EP from the HRA [A-H(HRA)], with the interval between atrial deflection at the prox-CS and His bundle electrogram after EP at an identical cycle length from the prox-CS [A-H (prox-CS)].

RESULTS

A typical A-H(CS) shorter than A-H(HRA), consistent with typical SP conduction, was observed in 39 patients (91%), and an atypical A-H(HRA) shorter than A-H(CS) was observed in 4 patients (9%). Successful ablation was obtained at the posteroseptum/midseptum in 32/7 patients with typical responses but only at the midseptum in all 4 patients with atypical responses (P = .0027). The atypical responses predicted a necessity for ablation at the midseptum, with positive and negative predictive values of 100% and 82%, respectively. The mechanism of an atypical response remains unclear but may involve an anatomical variation of Koch's triangle and/or the participation of a variant of the SP, including the superior SP, over which retrograde conduction was observed more frequently in patients with atypical responses (P = .0013).

CONCLUSIONS

Differential atrial EP predicts the ablation site for successfully curing S/F-AVNRT.

What Cannot be Missed: Must-read Papers, 2018

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Atypical Fast-Slow Atrioventricular Nodal Reentrant Tachycardia Utilizing a Slow Pathway Extending to the Inferolateral Right Atrium

Background: The existence of atypical fast-slow (F/S) atrioventricular (AV) nodal reentrant tachycardias (NRT) using slow pathway (SP) variants connected to the right atrial (RA) inferolateral (inf) free wall (FW) along the tricuspid annulus (TA), has been neither confirmed nor precisely characterized.

Methods and Results: We studied 7 patients (mean age, 48±16 years; 5 men) with F/S-AVNRT with long RP intervals and an earliest atrial activation at the RA inf-FW along the TA (inf-F/S-AVNRT). AV reentrant tachycardia was excluded on observation of the transition zone criteria in all 7 patients. Atrial tachycardia was excluded on the observation of a V-A-V activation sequence after the induction or entrainment of the tachycardia from the right ventricle in all. During the tachycardia, low-frequency, fractionated potentials (LP) preceding the local atrial electrogram were recorded near the site of the earliest atrial activation in 6 patients. Observations of conduction delay and block of the LP during ventricular entrainment or ablation of the tachycardia indicated that LP reflect retrograde activation via the inf-SP. Retrograde SP conduction was interrupted at the site of earliest atrial activation in 3 patients, and in the right posterior septum in 4 patients.

Conclusions: inf-F/S-AVNRT are distinct supraventricular tachycardia incorporating an SP variant connected to the RA inf-FW along the TA in the retrograde direction, which were eliminated by ablation.

Catheter Ablation of Atrioventricular Nodal Re-entrant Tachycardia: Facts and Fiction

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