Earliest Atrial Activation Site Research Articles

Is the conventional deployment of electrode catheters appropriate to diagnose the circuit of atypical atrioventricular nodal reentrant tachycardia? -New insights into the retrograde slow pathways-

Abstract During atypical atrioventricular nodal reentrant tachycardia (AVNRT), the earliest atrial activation site following retrograde slow pathway conduction is either at the exit of the left inferior extension (LIE) in the coronary sinus (CS) or that of the right inferior extension (RIE) on the tricuspid annulus (TA). In an EP study, LIE can be detected by the CS catheter, but absence of catheters at the RIE can lead to it being missed. Aim To evaluate the electrophysiological characteristics of the retrograde slow pathway. Methods We assessed patients with atypical AVNRT using electro-anatomical 3D mapping. Results Among 14 patients (9 females, age 59±17), with a total of 18 atypical AVNRTs (15 fast/slow and 3 slow/slow), 4 patients had LIE, 6 had RIE, and 4 had both. The LIE exits were inside the CS, while those of RIE were on the posterior TA. During AVNRT or ventricular pacing, the local electrogram of RIE preceded that of the CS ostium and HBE by 24±12 and 34±12 ms respectively. Examination of activation times at the CS ostium and HBE showed that the nearer to the exit of RIE they were, the earlier they were excited. Conclusion The retrograde slow pathway of atypical AVNRT can have an exit site at the LIE or RIE, or both. Accurate identification of inferior extensions of the AV node is critical for diagnosis and treatment. We recommend placing a catheter on the posterior TA or 3D mapping the area for RIE exit detection in atypical AVNRT patients.

Case report: Para Hisian Atrial Tachycardia

Case report: Para Hisian Atrial Tachycardia

Paradigm shift of catheter ablation of atypical atrioventricular nodal tachycardia: 3D mapping-based ablation of exits of slow pathway

Abstract Background In current practice, the ablation target of atypical atrioventricular nodal tachycardia (AVNRT) is the earliest atrial activation site in the coronary sinus (CS) or conventional slow pathway (SP) region. Objectives The purpose of this study was to map the site of earliest retrograde atrial activation using electroanatomic 3D mapping during atypical AVNRT and to evaluate successful ablation sites. Methods Forty-two patients with a total of 49 AVNRTs (slow/fast 30; fast/slow 15; slow/slow 4) underwent EP study and ablation. Among them there were 14 patients (10 women, 60±19 y/o) in whom 19 atypical AVNRT (fast/slow 15; slow/slow 4) were induced. Results The intracardiac electrocardiograms or 3D mapping of the exit site during tachycardia revealed that 7 patients had exit sites solely inside the CS (left inferior extension=LIE), 3 solely in the right postero-septal tricuspid annulus (TA) (right inferior extension=RIE), and 4 had both LIE and RIE exits. The distance from the CS ostium to LIE exits was 14±6 mm. RIE exits were located on the TA posterior to the CS ostium (between 5 and 6 o’clock in the LAO projection). Ablation targeting these exits or traditional SP succeeded in long term elimination of AVNRT in 13 of the 14 patients (93%). There were no complications. Conclusions Catheter ablation targeting the exit sites of LIE or RIE mapped at the CS or TA holds promise as an effective and safe alternative approach to the current targets of ablation for atypical AVNRT cases.Distribution of exit sites during atypicthe circuit of atypical AVNRT：the exit s

Paradigm Shift for Catheter Ablation of Atypical Atrioventricular Nodal Re-Entrant Tachycardia: 3-Dimensional Mapping–Based Ablation

BackgroundIn current practice, the ablation target of atypical atrioventricular nodal re-entrant tachycardia (AVNRT) is the earliest atrial activation site in the coronary sinus (CS) or conventional slow pathway region. ObjectivesThe purposes of this study were to map the site of earliest retrograde atrial activation using electroanatomic three-dimensional mapping during atypical AVNRT and to evaluate successful ablation sites. MethodsA total of 42 patients with a total of 49 AVNRTs (slow/fast: 30; fast/slow: 15; slow/slow: 4) underwent electrophysiological study and ablation. Among them there were 14 patients (10 women; 60 ± 19 years of age) in whom 19 atypical AVNRT (fast/slow: 15; slow/slow: 4) were induced. ResultsThe intracardiac electrocardiograms or three-dimensional mapping of the exit site during tachycardia revealed that 7 patients had exit sites solely inside the CS (left inferior extension [LIE]), 3 solely in the right postero-septal tricuspid annulus (TA; right inferior extension [RIE]), and 4 had both LIE and RIE exits. The distance from the CS ostium to LIE exits was 14 ± 6 mm. RIE exits were located on the TA posterior to the CS ostium (between 5 and 6 o’clock in the left anterior oblique projection). Ablation targeting these exits or conventional slow pathway succeeded in long-term elimination of AVNRT in 13 of the 14 patients (93%). There were no complications. ConclusionsCatheter ablation targeting the exit sites of LIE or RIE mapped at the CS or TA holds promise as an effective and safe alternative approach to the current targets of ablation for atypical AVNRT cases.

PO-04-109 OUTCOMES OF RADIOFREQUENCY CATHETER ABLATION OF DISTINCT ANTERO-SEPTAL ACCESSORY PATHWAYS BY CONVENTIONAL ELECTROPHYSIOLOGICAL MAPPING

Ablation of para-hisian accessory pathways (APs) is challenging because of their proximity to the conduction system. A high incidence of atrio-ventricular (AV) conduction injury (up to 50%) was observed for the ablation of true para-hisian APs. In this retrospective study, we report the outcomes of a large series of patients with antero-septal APs (including true para-hisian APs) who underwent radiofrequency catheter ablation (RFCA). Among 1676 consecutive patients undergoing RFCA of APs between January 2016 and September 2022 in our center, 276 patients with an isolated antero-septal AP were enrolled. Conventional intracardiac mapping and fluoroscopy were used in all procedures. All procedures were performed by an experienced operator with a standard 3.5 mm irrigated tip catheter. A para-hisian AP was confirmed when an His potential was recorded by the distal ablation catheter at the site of earliest atrial activation during orthodromic AVRT or after ablation of the manifest AP. APs were categorized as true para-hisian if a sharp high-amplitude His potential was recorded. Among the 276 patients (mean age 27±10 years; 150 males) with an antero-septal AP: 55 patients (20%) had a true para-hisian AP (Group 1); 89 patients (32%) had a not-sharp low-amplitude His potential (Group 2); 132 patients (48%) had no His potential recorded (Group 3). The three Groups showed no significant difference in clinical (age, sex, history of AF and AVRT, structural heart disease) and EPS variables (conduction properties of APs and inducibility of AVRT and AF). Inferior vena cava (n=260) and aortic retrograde (n=16, targeting the left basal septum) approaches were used. Procedural acute success (no evidence of residual preexcitation or abnormal retrograde conduction) was obtained in all patients. No patient experienced acute severe complications. RF ablation time was longer in Group 1 (135±41 sec vs 115±27 sec [Group 2] vs 92 sec ±18 sec [Group 3], p=0.03). Accelerated junctional rhythm during RFCA was more frequent in Group 1 (25% vs 14% [Group 2] vs 3% [Group 3], p=0.02). After a median follow-up of 40 (2-78) months no high-grade AV block was reported. 1 patient of Group 1 had a recurrent para-hisian AP and underwent a second successful RFCA. In this large series of antero-septal APs (including a high number of true para-hisian APs), electrophysiologically-guided RFCA was safe and highly effective.

Notable Pacemaker Shift in the Sinoatrial Node After Administration of Isoproterenol.

A 63-year-old woman underwent a redo catheter ablation for recurrent atrial fibrillation (AF) after an initial cryoballoon ablation. After confirming the electrical isolation of 4 pulmonary veins, empiric superior vena cava (SVC) isolation was performed without documenting AF triggers. A 20-pole PentaRay NAV catheter (Biosense Webster, Diamond Bar, CA) was used to create an activation map during sinus rhythm to identify the anatomic location of the sinoatrial node (SAN). The earliest atrial activation site (EAS) at baseline was the basal lateral wall of the right atrial appendage (Fig. 1A).

Narrow QRS complex tachycardia with and without ventriculoatrial block: What is the mechanism?

A 39-year-old woman with no structural heart disease underwent an electrophysiology study (EPS) to assess recurrent supraventricular tachycardia (SVT). The electrocardiogram did not show any preexcitation. The baseline atrio-His and His-ventricular intervals were 108 and 43 ms. Ventricular pacing demonstrated concentric, decremental ventriculoatrial (VA) conduction, and the single jump changed the earliest atrial activation site (EAAS) from the His bundle region to the proximal coronary sinus (CS) region.

Electrophysiological characteristics and catheter ablation of atypical fast-slow atrioventricular nodal reentrant tachycardia using an inferolateral left atrial slow pathway

Abstract Background Understandings of subtypes of atypical atrioventricular nodal reentrant tachycardia (AVNRT) using variants of slow pathway (SP) are still growing. Inferolateral (inf-lat-) left atrial (LA) SP is a rare variant extending into an inf-lat-LA along the mitral annulus (MA). Purpose To characterize an unknown subtype of atypical fast-slow (F/S-) AVNRT using an inf-lat-LA-SP as a retrograde limb (inf-lat-LA-F/S-AVNRT). Methods This Japanese multicenter retrospective study enrolled 4 patients of inf-lat-LA-F/S-AVNRT that was characterized by the earliest site of atrial activation during tachycardia (EAA) between 3 and 6 o'clock along the MA. The diagnosis was made by an exclusion of AV reentrant tachycardia (AVRT) and atrial tachycardia (AT) according to the standard criteria and was confirmed by successful elimination of tachycardia and the inf-lat-LA-SP. Results Surface ECG during tachycardia revealed long RP appearance except one who had short RP due to a short conduction time across the inf-lat-LA-SP. During tachycardia, far-field LA activation preceding near-field activation of coronary sinus (CS) musculature was visible in the CS recording in 2. Retrograde conduction via the inf-lat-LA-SP with a decremental delay was consistently reproducible with ventricular stimulation in 2, 1 of whom had double atrial response, while it was always masked by the presence of a retrograde conduction via the fast pathway in 1 and a retrograde block at the lower common pathway in 1. An injection of a small dose of ATP transiently interrupted a retrograde conduction over the inf-lat-LA-SP, suggesting its ATP-sensitivity. Exclusion of AVRT was made by no resetting of tachycardia with left ventricular extrastimulus in 2 and VA dissociation during overdrive pacing of tachycardia in remaining 2. Exclusion of AT was made by V-A-V response after ventricular entrainment in 1 and termination without atrial capture by ventricular pacing in 2. Ablation of the right-sided SP was unsuccessful to eliminate the tachycardia, but ablation at or near the EAA by transseptal approach was successful to cure the tachycardia, associated with an elimination of a retrograde conduction over the inf-lat-LA-SP following a development of an accelerated junction rhythm in all. Low-frequency potentials preceding local atrial activation, consistent with a retrograde activation via the inf-lat-LA-SP were detected along the MA medial to the EAA in 1. Conclusions Differential diagnosis of tachycardia with the EAA in the inf-lat-LA and especially long RP appearance should include inf-lat-LA-F/S-AVNRT. Presumed arrhythmogenic substrate of the inf-lat-LA-SP seemed to be consistent with the remnant of embryogenic AV ring tissue in the electropharmacological and locational characteristics. Successful elimination of this AVNRT can be obtained by ablation of the inf-lat-LA-SP, but not of the right-sided SP. Funding Acknowledgement Type of funding sources: None.

Last Entrainment Sequence: A Novel Diagnostic Technique for Atrial Tachycardia Mimicking Other Supraventricular Tachycardias.

Adenosine-sensitive re-entrant atrial tachycardia (AT) originating from near the atrioventricular (AV) node or AV annulus resembles other supraventricular tachycardias (SVTs), and the differential diagnosis is sometimes challenging. This study sought to develop a novel technique to distinguish adenosine-sensitive re-entrant AT from AV nodal re-entrant tachycardia (AVNRT) and orthodromic reciprocating tachycardia (ORT). The study retrospectively studied 117 re-entrant SVTs that were successfully entrained by atrial overdrive pacing (AOP) (27 adenosine-sensitive re-entrant ATs, 63 AVNRTs, 27 ORTs). If the second atrial electrogram after AOP (A2) at the earliest atrial activation site (EAAS) accelerated to the pacing cycle length, the EAAS was considered orthodromically activated. Then, we compared the sequence of A2 and the last entrained His bundle (H∗) and QRS complex (V∗). The study hypothesized that the last entrained impulse would activate the EAAS before it enters the AV node, His bundle, and ventricle during AT (A2-H∗-V∗) but would activate the EAAS after the His bundle activation during AVNRT and ORT (H∗-V∗-A2 or H∗-A2-V∗). Orthodromic EAAS activation was documented during AOP in 84 SVTs (72%) when performing AOP from sites proximal to the entrance of SVTs. A2-H∗-V∗ responses were observed in 21 of 25 ATs, but were never for AVNRTs or ORTs. All ORTs and fast-slow AVNRTs had H∗-V∗-A2 responses. Eleven of 21 slow-fast AVNRTs had H∗-A2-V∗ responses. The sensitivity, specificity, and positive and negative predictive values of the A2-H∗-V∗ response for diagnosing AT were 84%, 100%, 100%, and 94%, respectively. The last entrainment sequence was useful for differentiating ATs with diagnostic difficulties.

Efficacy of catheter ablation from the noncoronary aortic cusp of verapamil-sensitive atrial tachycardia arising near the atrioventricular node.

The efficacy of catheter ablation from the noncoronary aortic cusp (NCC) of verapamil-sensitive atrial tachycardia arising near the atrioventricular node (AVN-AT) has yet to be fully clarified. We elucidated the determinant of an effective AVN-AT ablation from the NCC. After identifying the earliest atrial activation site (EAAS) during tachycardia, the direction of the slow conduction zone (SCZ) of the reentry circuit was identified by demonstrating manifest entrainment in 26 patients with AVN-AT. Catheter ablation was initially performed from the NCC irrespective of the local activation time. If NCC ablation was ineffective, catheter ablation was performed targeting the SCZ entrance. Then the anatomical relationship between the SCZ and the successful ablation site was elucidated. NCC catheter ablation terminated AVN-AT in 14 patients (NCC group) but not in 12 (non-NCC group). Catheter ablation targeting the SCZ entrance terminated all non-NCC group ATs. The local activation time at the NCC relative to the EAAS did not differ between the NCC and non-NCC groups (10.1 ± 6.5 ms vs 11.2 ± 4.8 ms; P = .6333). The direction of the SCZ was posterior to the EAAS in all NCC group patients; however, it was posterolateral (n = 5) and lateral (n = 7) to the EAAS in the non-NCC group, suggesting that the SCZ existed in the direction of the NCC in the NCC group but was away from the NCC in the non-NCC group. A close proximity between the NCC and the SCZ of the reentry circuit, but not the local activation time at the NCC, determined the efficacy of NCC catheter ablation in AVN-ATs.

Intermittent orthodromic capture of the earliest activation site during atrial pacing in a case with reentrant atrial tachycardia originating from the atrioventricular node vicinity.

Constant pacing (S1-S1: 520ms) from the right atrial appendage (RAA) during reentrant atrial tachycardia originating from the atrioventricular node vicinity. RA-FW 1-2 was constantly captured antidromically. However, the earliest atrial activation site (EAAS=His1-2) was orthodromically (red circle) and antidromically (blue square) captured at a ratio of 3:1. The electrogram morphology at the EAAS was different between orthodromically and antidromically electrograms captured during pacing. Moreover, the interval between the S1 and orthodromically captured electrogram was gradually prolonged.

Sinus Node Sparing Hybrid Thoracoscopic Ablation Outcomes in Patients with Inappropriate Sinus Tachycardia (SUSRUTA-IST) Registry.

Medical treatment of inappropriate sinus tachycardia (IST) remains suboptimal. Radiofrequency sinus node (RF-SN) ablation has poor success and higher complication rates. We aimed to compare clinical outcomes of the novel SN sparing hybrid ablation technique with those of RF-SN modification for IST management. This is a multicenter prospective registry comparing the SN sparing hybrid ablation strategy with RF-SN modification. The hybrid procedure was performed using an RF bipolar clamp, isolating superior vena cava/inferior vena cava with the creation of a lateral line across the crista terminalis while sparing the SN region (identified by endocardial 3-dimensional mapping). RF-SN modification was performed by endocardial and/or epicardial mapping and ablation at the site of earliest atrial activation. Of the 100 patients (hybrid ablation group, n = 50; RF-SN group, n = 50), 82% were women, and the mean age was 22.8 years. Normal sinus rhythm and rate were restored in all patients in the hybrid group (vs 84% in the RF-SN group; P = .006). Hybrid ablation was associated with significantly better improvement in mean daily heart rate and peak 6-minute walk heart rate compared with RF-SN ablation. The RF-SN group had a significantly higher rate of redo procedures (100% vs 8%; P < .001), phrenic nerve injury (14% vs 0%; P = .012), lower acute pericarditis (48% vs 92%; P< .0001), permanent pacemaker implantation (50% vs 4%; P<.0001) than did the hybrid ablation group. The novel sinus node sparing hybrid ablation procedure appears to be more efficacious and safer in patients with symptomatic drug-resistant IST with long-term durability than RF-SN ablation.

Abstract 11080: A Young Woman with Incessant Left Atrial Tachycardia

Introduction: Left atrial tachycardia (AT) is uncommon and usually does not occur in the absence of congenital heart disease, or prior catheter ablation (CA). Case: A 29-year-old woman with a 2-year history of SVT refractory to metoprolol and no prior CA presented to the emergency department with palpitations. Initial ECG showed a regular, narrow complex, short RP tachycardia, at 180 bpm, insensitive to adenosine and 2 electrical cardioversions. Echocardiogram showed LVEF of 40%. The patient underwent an entirely non-fluoroscopic electrophysiology study using intracardiac echocardiography and electroanatomic mapping (EAM). AT (cycle length 300 ms) was induced by programmed atrial stimulation with isoproterenol infusion. AT was confirmed with ventriculo-atrial dissociation after pacing maneuvers and adenosine administration. Right atrial (RA) activation map revealed early atrial activation in the mid coronary sinus (CS), raising suspicion of a left atrial (LA) origin. LA was accessed via transseptal puncture. The site of earliest atrial activation was in the LA wall inferior to the left inferior pulmonary vein (LIPV) ostium and was successfully terminated with radiofrequency ablation (40 W, 5 to 10 g) (Figure) with no further inducibility. The patient's symptoms resolved after the procedure. Discussion: Left AT usually originates from PVs or the atrial wall. The EAM in this patient showed centrifugal activation consistent with a focal mechanism. Adenosine is generally not helpful in terminating AT but is useful in diagnosis. Rapid conduction across the LA to CS may have given rise to early activation in the mid CS on RA mapping. However, LA mapping revealed that atrial activation was earliest in the LA wall inferior to the LIPV. Conclusion: AT is unusual in young, healthy women. A high index of suspicion to perform transseptal puncture can lead to successful ablation of AT with LA origin. We surmise that the patient’s EF may improve with termination of the tachycardia.

Fast-slow atrioventricular nodal reentrant tachycardia phenotype mimicking the slow-slow type

Abstract Background Fast-slow (F/S-) atrioventricular (AV) nodal reentrant tachycardia (AVNRT) is characterized by a short atrio-His (AH) interval and the earliest site of atrial activation (EAA) in the proximal coronary sinus (EAA-CS), while slow-slow (S/S-) AVNRT presents a long AH interval and EAA-CS. Those intracardiac appearances are initial indicators for making a diagnosis. Purpose To identify an unknown phenotype of F/S-AVNRT. Methods Among 46 consecutive patients with F/S-AVNRT, 6 patients (1 man, age 59±9) had an apparent but not typical (pseudo-) S/S-AVNRT during an electrophysiologic study. In 2 patients, pseudo-S/S-AVNRT was clinically documented. Results In all 6 patients, the diagnosis of F/S-AVNRT was made by an exclusion of atrial tachycardia with findings of 1) a V-A-V response following ventricular entrainment or 2) termination without atrial capture by ventricular pacing, and an exclusion of AV reentrant tachycardia with a ventriculoatrial dissociation during an initial (so-called QRS transition) zone of ventricular entrainment. An initial A-A-V activation sequence on atrial induction of F/S-AVNRT observed in 1 patient and Wenckebach-type AV block during ongoing F/S-AVNRT developing in 3 patients suggested the presence of the lower common pathway (LCP). Like the typical S/S-AVNRT, pseudo-S/S-AVNRT was induced with atrial stimulation after a jump in the AH interval or double ventricular response. However, in all patients, the pseudo-S/S-AVNRT transited to F/S-AVNRT following AV block in a single cycle and/or pseudo-S/S-AVNRT transited from spontaneously or triggered by atrial contractions. Importantly, on these transitions, the atrial cycle length (CL) and EAA-CS remained unchanged, that is, the atrial CL of S/S-AVNRT was almost identical to that of F/S-AVNRT, suggesting that the essential circuit of both tachycardias was identical. Actually, both tachycardias were cured by ablation at a single site in the traditional slow pathway (SP). Collectively, the pseudo-S/S-AVNRT was diagnosed as another phenotype of F/S-AVNRT accompanied by sustained antegrade conduction via another bystander (likely the left-sided or superior) SP breaking through the His bundle owing to the repetitive antegrade block at the LCP occurring by linking phenomenon, thus representing a long AH interval during the ongoing F/S-AVNRT. When the antegrade conduction is blocked at the bystander SP during the pseudo-S/S-AVNRT, releasing the linking phenomenon, the subsequent antegrade conduction reach the His-bundle via the fast pathway, thus returning to F/S-AVNRT. Conclusions An unknown, but not rare F/S-AVNRT phenotype exists that apparently mimics the typical S/S-AVNRT and is also an unknown subtype of apparent S/S-AVNRT. The presence of this pseudo-S/S-AVNRT suggests the limitation of classifying types of AVNRT based on AH and HA intervals during tachycardia. Understandings of this phenotype can advance a diagnosis of atypical AVNRT with multiple phenotypes. Funding Acknowledgement Type of funding sources: None.

B-PO05-131 TYPICAL BRIDGE FOR ATYPICAL AVNRT

Lower ablation success rates have been associated with atypical AVNRT. Evidence for ablation strategies for atypical AVNRT remain limited due to low prevalence. Anatomical ablation and identification of slow pathway through retrograde conduction have been reported. Voltage gradient mapping guided ablation has been evaluated in typical, “slow-fast” AVNRT. We describe two cases of atypical AVNRT that were successfully treated with targeting low voltage bridge for catheter ablation. N/A A 19yo man with symptomatic SVT presented for EPS and ablation. During EPS, tachycardia was initiated with atrial extrastimuli, and atypical AVNRT was diagnosed using standard pacing maneuvers (Figure, Panel A). A voltage map was created during sinus rhythm and low voltage bridge was identified (Figure, Panel B). Additionally, earliest atrial activation was mapped during tachycardia and localized to low voltage bridge (Figure, Panel C). RFA lesions were delivered over the low voltage bridge with associated junctional beats. He was non-inducible and is arrhythmia-free in follow up. Another case of atypical AVNRT in a 42yo male was approached similarly. Low voltage bridge was identified with voltage mapping during sinus rhythm and subsequently earliest atrial activation in tachycardia was identified. This case also demonstrated overlap in the localization of earliest atrial activation during tachycardia and low voltage bridge. To our knowledge, these are the first reported cases of atypical AVNRT successfully ablated by identifying a low voltage bridge, which correlated to site of earliest atrial activation, as a target for ablation.

Comparison of the catheter ablation outcome in patients between targeting the entrance and exit of the reentry circuit in verapamil-sensitive atrial tachycardia originating from the atrioventricular-node vicinity

Verapamil-sensitive atrial tachycardia originating from the atrioventricular node vicinity (AVN-AT) can be eliminated with radiofrequency energy (RF) deliveries targeting either the entrance or exit of its reentry circuit. However, the outcome of these different approaches has not been clarified well. Thus, we compared the catheter ablation outcome targeting the entrance of reentry circuit, identified by the entrainment method (Ent-Group; 21 patients) with that targeting the earliest atrial activation site (EAAS) during AT (Exit-Group; 16 patients). There was no significant difference in the tachycardia cycle length (441.4 ± 87.4 vs. 392.8 ± 64.8ms, p = 0.0704) or distance from the His bundle (HB) site to the EAAS (6.5 ± 2.0 vs. 7.6 ± 1.8mm, p = 0.0822) between the Ent- and Exit-Groups. However, distance from the successful ablation site to the HB site in the Ent-Group was significantly longer than that in the Exit-Group (13.4 ± 3.1 vs. 7.6 ± 1.8mm, p < 0.0001), resulting in more frequent transient atrioventricular block episodes in the Exit-Group than Ent-Group (31.3 vs. 0%, p < 0.01). Initial ATs (AT1s) were terminated in all patients in both Groups. However, ATs accompanied by shifting in the EAAS (AT2) were induced more frequently in the Exit-Group than Ent-Group (50.0 vs. 14.3%, p < 0.02) after eliminating AT1. RF deliveries to the EAAS eliminated all AT2s. The number of RF deliveries was greater in the Exit-Group than Ent-Group (6.9 ± 3.3 vs. 3.9 ± 1.6, p < 0.001). In conclusion, RF ablation targeting the entrance sites can avoid AVN injury and is superior in reducing the number of RF deliveries and occurrence of different ATs than targeting the exit sites in the AVN-AT.

Superior-Type Fast-Slow Atrioventricular Nodal Reentrant Tachycardia Phenotype Mimicking the Slow-Fast Type.

Superior-type fast-slow (sup-F/S-) atrioventricular nodal reentrant tachycardia (AVNRT) is a rare AVNRT variant using a superior slow pathway (SP) as the retrograde limb. Its intracardiac appearance, characterized by a short atrio-His (AH) interval and the earliest site of atrial activation in the His-bundle, is an initial indicator for making a diagnosis. Among 22 consecutive patients with sup-F/S-AVNRT, 3 (age, 68-81 years) patients had an apparent slow-fast (S/F-) AVNRT characterized by a long AH interval and the earliest site of atrial activation in or superior to the His-bundle region (tachy-long-AH). The diagnosis of sup-F/S-AVNRT was based on the standard criteria in 2 patients and on the occurrence of Wenckebach-type atrioventricular block during tachycardia, which was attributable to a block at the lower common pathway (LCP) below the circuit of the AVNRT, detected owing to the lower common pathway potentials, in one patient. As with the typical S/F-AVNRT, tachy-long-AH was induced after a jump in the AH interval. In contrast to typical S/F-AVNRT, fluctuation in the ventriculoatrial interval was observed during the tachy-long-AH. Ventricular overdrive pacing was unable to entrain or terminate the tachy-long-AH. Moreover, the tachy-long-AH reciprocally transited to/from sup-F/S-AVNRT spontaneously or was triggered by ventricular contractions while the atrial cycle length and earliest site of atrial activation remained unchanged. Both tachycardias were cured by ablation at a single site in the right-side para-Hisian region of 2 patients and the noncoronary aortic cusp of one patient. Collectively, the essential circuit of both tachycardias was identical, and the tachy-long-AH was diagnosed as another phenotype of sup-F/S-AVNRT accompanied by sustained antegrade conduction via another bystander slow pathway breaking through the His-bundle owing to the repetitive antegrade block at the lower common pathway, thus representing a long AH interval during the ongoing sup-F/S-AVNRT. An unknown sup-F/S-AVNRT phenotype exists that apparently mimics the typical S/F-AVNRT and is also an unknown subtype of apparent S/F-AVNRT.

Demonstration of the Anatomical Tachycardia Circuit in Sinoatrial Node Reentrant Tachycardia: Analysis Using the Entrainment Method.

BackgroundThe anatomical tachycardia circuit of sinoatrial node reentrant tachycardia (SANRT) has not been well clarified. This study aimed to elucidate the tachycardia circuit of SANRT.Methods and ResultsExit and entrance of the intranodal sinoatrial node conduction (I‐SANC) of the reentry circuit were identified in 15 SANRT patients. After identifying the earliest atrial activation site (EAAS) during the tachycardia (EAAS‐SANRT), rapid atrial pacing was delivered from multiple atrial sites to identify the entrainment pacing site where manifest entrainment and orthodromic capture of the EAAS‐SANRT were demonstrated. Radiofrequency energy was then delivered starting at a site 2 cm proximal to the EAAS‐SANRT in the direction of the entrainment pacing site and gradually advanced toward the EAAS‐SANRT until tachycardia termination to localize the I‐SANC entrance. The EAAS‐SANRT was orthodromically captured by pacing delivered from the distal coronary sinus (n=7), high posteroseptal right atrium (n=2), low posteroseptal right atrium (n=2), low anterolateral right atrium (n=2), or coronary sinus ostium (n=2). Radiofrequency energy delivery to the entrance of the I‐SANC, 10.4±2.8 mm away from the EAAS‐SANRT, terminated tachycardia immediately after onset of energy delivery (3.4±2.3 seconds). The successful ablation site was located further from the EAAS during sinus rhythm (EAAS‐sinus) than the EAAS‐SANRT (12.8±4.5 versus 7.2±3.1 mm; P<0.0001).ConclusionsThe reentry circuit of SANRT was composed of the entrance and exit of the I‐SANC being located at distinctly different anatomical sites. SANRT was eliminated by radiofrequency energy delivered to the I‐SANC entrance, which was further from the EAAS‐sinus than I‐SANC exit.

P1005Origin, distribution and timing of the slow pathway potentials recorded inside the Kock's triangle in Avnrt patients through High-density Mapping

Abstract Background Atrial activation during typical atrioventricular nodal reentrant tachycardia (AVNRT) exhibits anatomic variability and spatially heterogeneous propagation inside the Kock's Triangle (KT). The mechanism of the reentrant circuit has not been elucidated yet. Purpose To evaluate signal characteristics and find out the origin, distribution, and timing of the slow pathway (SP) potentials recorded in the KT. Methods The 3-D KT geometry was created during both sinus rhythm (SR) and tachycardia (TR) from the basket mapping catheter IntellaMap Orion and the Rhythmia Mapping System (Boston Scientific). The KT was divided into 8 regions moving from an antero-septal to postero-septal areas and bounded by tricuspid annulus (TA) anteriorly and tendon of Todaro (TT) posteriorly. Each area was characterized in terms of distribution and timing of Jackman (JP) and Haissaguerre (HP) potentials and signal amplitude. Results 20 consecutive successful SP ablation cases of AVNRT were included (mean RA acquired points = 6000±1100, 275±63 inside the KT; mean KT area=29±3mm2; mean mapping time=12±5 minutes). During SR, the site of earliest atrial activation within the KT was anterior in 80% of patients whereas a midseptal activation occurred less frequently (20%). The mid-septal regions bounded by TA anteriorly and TT posteriorly showed higher prevalence of JP as compared to antero-/mid-septal regions across TT both in SR and TR (77.4% vs 4.8% during SR, p&lt;0.0001; 84.1% vs 0% during TR, p&lt;0.0001, respectively). HPs seemed to have variable distribution across KT (50% of these potentials recorded in antero- to mid-septal regions across TT for SR, 52.3% for TR). The median signal voltage was 0.44 [0.2–0.9] mV during SR and 0.5 [0.22–0.895] mV during TR. The mid-septal region was the area of lowest voltage compared to other regions (0.2 [0.1–0.7] mV vs 0.5 [0.4–1.5] mV for SR, p&lt;0.0001; 0.2 [0.15–0.6] mV vs 0.6 [0.4–1.5] mV for TR, p&lt;0.0001, respectively). Conclusion JPs seem to be associated with low signal-amplitude areas whereas HPs seem to have variable distribution across KT. Although not perfectly known, the typical low-high-type double potential of JP might be therefore explained by wavefront collision in the lowest area of the KT. Acknowledgement/Funding None

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.