Successful Slow Pathway Ablation Research Articles

The optimal slow pathway ablation site in atrioventricular nodal reentrant tachycardia cases with an inferiorly located His bundle.

The optimal slow pathway (SP) ablation site in cases with an inferiorly located His bundle (HIS) remains unclear. In 45 patients with atrioventricular nodal reentrant tachycardia, the relationship between the HIS location and successful SP ablation site was assessed in electroanatomical maps. We assessed the location of the SP ablation site relative to the bottom of the coronary sinus ostium in the superior-to-inferior (SPSI), anterior-to-posterior (SPAP), and right-to-left (SPRL) directions. The HIS location was assessed in the same manner. The HIS location in the superior-to-inferior direction (HISSI), SPSI, SPAP, and SPRL were 17.7±6.4, 1.7±6.4, 13.6±12.3, and -1.0±13.0mm, respectively. The HISSI was positively correlated with SPSI (R2=0.62; P<.01) and SPAP (R2=0.22; P<.01), whereas it was not correlated with SPRL (R2=0.01; P=.65). The distance between the HIS and SP ablation site was 17.7±6.4mm and was not affected by the location of HIS. The ratio of the amplitudes of atrial and ventricular potential recorded at the SP ablation site did not differ between the high HIS group (HISSI≥13mm) and low HIS group (HISSI<13mm) (0.10±0.06vs. 0.10±0.06; P=.38). In cases with an inferiorly located HIS, SP ablation should be performed at a lower and more posterior site than in typical cases.

Distinctive characteristics of His bundle potentials in patients with atrioventricular nodal reentrant tachycardia.

His bundle (HB) potentials vary in amplitude and duration in patients with and without slow pathways. The aim of this study was to determine the characteristics of HB potentials and to elucidate whether they can provide clues for identification of slow pathway (SP). The present research prospectively studied the electrophysiological findings of 162 patients with symptomatic atrioventricular nodal reentrant tachycardia (AVNRT) due to slow-fast or fast-slow type and atrioventricular reentrant tachycardia (AVRT). Maximal HB potential (HBmax, HB with the highest amplitude) among HB cloud was recorded in both groups. For AVNRT patients, the following were measured: (1) AH interval at the "jump" during programmed atrial stimulation (A2H2, taken as a reflection of SP conduction time); (2) Distance from HBmax to the successful SP ablation site (HBmax-ABL) and from HBmax to the ostium of coronary sinus (HBmax-CSO). HBmax was 0.29 ± 0.10 mV in AVNRT patients, whereas it was 0.17 ± 0.05 mV in AVRT group (p < 0.0001). Likewise, the HBmax duration was 22 ± 5 ms in AVNRT group and 16 ± 3 ms in AVRT group (p < 0.0001). The area under the receiver operating characteristic curve of HBmax amplitude in AVNRT patients was 0.86 and the optimal HBmax cut-off to predict AVNRT was ≥ 0.22 mV with a sensitivity of 0.78 and specificity of 0.84. HBmax-CSO was positively correlated with HBmax-ABL, and HBmax-ABL was positively correlated with A2H2. HBmax amplitudes were higher and durations longer in patients with AVNRT, as compared to those with AVRT. Moreover, the distance between HBmax and successful ablation site was positively correlated with the SP conduction time and with the distance from HBmax to the CSO.

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

Atrial activation during typical atrioventricular nodal reentrant tachycardia (AVNRT) exhibits anatomic variability and spatially heterogeneous propagation inside the Koch's triangle (KT). The mechanism of the reentrant circuit has not been elucidated yet. Aim of this study is to describe the distribution of Jackman and Haïssaguerre potentials within the KT and to explore the activation mode of the KT, in sinus rhythm and during the slow-fast AVNRT. Forty-five consecutive cases of successful slow pathway (SP) ablation of typical slow-fast AVNRT from the CHARISMA registry were included. The KT geometry was obtained on the basis of the electroanatomic information using the Rhythmia mapping system (Boston Scientific) (mean number of points acquired inside the KT = 277 ± 47, mean mapping time = 11.9 ± 4min). The postero-septal regions bounded anteriorly by the tricuspid annulus and posteriorly by the lateral wall toward the crista terminalis showed a higher prevalence of Jackman potentials than mid-postero-septal regions along the tendon of Todaro and coronary sinus (CS) (98% vs. 16%, p < 0.0001). Haïssaguerre potentials seemed to have a converse distribution across the KT (0% vs. 84%, p < 0.0001). Fast pathway insertion, as located during AVNRT, was mostly recorded in an antero-septal position (n = 36, 80%), rather than in a mid-septal (n = 6, 13.3%) or even postero-septal (n = 3, 7%) location. During typical slow-fast AVNRT, two types of propagation around the CS were discernible: anterior and posterior, n = 31 (69%), or only anterior, n = 14 (31%). During the first procedure, the SP was eliminated, and acute procedural success was achieved (median of 4 [3-5] RF ablations). High-density mapping of KT in AVNRT patients both during sinus rhythm and during tachycardia provides new electrophysiological insights. A better understanding and a more precise definition of the arrhythmogenic substrate in AVNRT patients may have prognostic value, especially in high-risk cases. Catheter Ablation of Arrhythmias With High Density Mapping System in the Real World Practice (CHARISMA) URL: http://clinicaltrials.gov/ Identifier: NCT03793998.

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

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

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

High incidence of atrial fibrillation after successful catheter ablation of atrioventricular nodal reentrant tachycardia: a 15.5-year follow-up

Atrioventricular nodal reentrant tachycardia (AVNRT) is the most common type of supraventricular tachycardia. Slow pathway (SP) ablation is the treatment of choice with a high acute success rate and a negligible periprocedural risk. However, long-term outcome data are scarce. The aim of this study was to assess long-term outcome and arrhythmia free survival after SP ablation. In this study, 534 consecutive patients with AVNRT, who underwent SP ablation between 1994 and 1999 were included. During a mean follow-up of 15.5 years, 101 (18.9%) patients died unrelated to the procedure or any arrhythmia. Data were collected by completing a questionnaire and/or contacting patients. Clinical information was obtained from 329 patients (61.6%) who constitute the final study cohort. During the electrophysiological study, sustained 1:1 slow AV nodal pathway conduction was eliminated in all patients. Recurrence of AVNRT was documented in 9 patients (2.7%), among those 7 patients underwent a successful repeat ablation procedure. New-onset atrial fibrillation (AF) was documented in 39 patients (11.9%) during follow-up. Pre-existing arterial hypertension (odds ratio 2.61, 95% CI 1.14–5.97, p = 0.023), age (odds ratio 1.05, 95% CI 1.02–1.09, p = 0.003) and the postinterventional AH interval (odds ratio 1.02, 95% CI 1.00–1.04, p = 0.038) predicted the occurrence of AF. The present long-term observational study after successful SP ablation of AVNRT confirms its clinical value reflected by low recurrence and complication rates. The unexpectedly high incidence of new-onset AF (11.9%) may impact long-term follow-up and requires further clinical attention.

A simplified approach for evaluating sustained slow pathway conduction for diagnosis and treatment of atrioventricular nodal reentry tachycardia in children and adults

PurposeDuring incremental atrial pacing in patients with atrioventricular nodal reentrant tachycardia, the PR interval often exceeds the RR interval (PR > RR) during stable 1:1 AV conduction. However, the PR/RR ratio has never been evaluated in a large group of patients with pacing from the proximal coronary sinus and after isoproterenol challenge. Our study validates new site of pacing and easier method of identification of PR > RR. Material and methodsA prospective protocol of incremental atrial pacing from the proximal coronary sinus was carried out in 398 patients (AVNRT-228 and control-170). The maximum stimulus to the Q wave interval (S-Q = PR), SS interval (S-S), and Q-Q (RR) interval were measured at baseline and 10 min after successful slow pathway ablation and after isoproterenol challenge (obligatory). ResultsThe mean maximum PR/RR ratios at baseline were 1.17 ± 0.24 and 0.82 ± 0.13 (p < 0.00001) in the AVNRT and controls respectively. There were no PR/RR ratios ≥1 at baseline and after isoproterenol challenge in 12.3% of the AVNRT group and in 95.9% of the control group (p < 0.0001). PR/RR ratios ≥1 were absent in 98% of AVNRT cases after slow pathway ablation/modification in children and 99% of such cases in adults (P = NS). The diagnostic performance of PR/RR ratio evaluation before and after isoproterenol challenge had the highest diagnostic performance for AVNRT with PR/RR > = 1 (sensitivity: 88%, specificity: 96%, PPV-97%, NPV-85%). ConclusionsThe PR/RR ratio is a simple tool for slow pathway substrate and AVNRT evaluation. Eliminating PR/RR ratios ≥1 may serve as a surrogate endpoint for slow pathway ablation in children and adults with AVNRT.

Intracardiacablation for atrioventricular nodal reentry tachycardia using a 6mm distal electrode cryoablation catheter: Prospective, multicenter, North American study (ICY-AVNRT STUDY).

Radiofrequency (RF) ablation is effective for slow pathway ablation, but carries a risk of inadvertent AV block requiring permanent pacing. By comparison, cryoablation with a 4-mm distal electrode catheter has not been reported to cause permanent AV block but has been shown to be less effective than RF ablation. We sought to define the safety and efficacy of a 6-mm distal electrode cryoablation catheter for slow pathway ablation in patients with atrioventricular nodal reentry tachycardia (AVNRT). Twenty-six U.S. and eight Canadian centers participated in the study. Patients with supraventricular tachycardia (SVT) thought likely to be AVNRT were enrolled. If AVNRT was inducible and confirmed to be the clinical SVT, then the slow pathway was targeted with a cryoablation catheter using a standardized protocol of best practices. Acute success was defined as inducibility of no more than one echo beat after cryoablation. Primary efficacy was defined as acute success and the absence of documented recurrent AVNRT over 6 months of follow-up. Primary safety was a composite of serious procedure-related adverse events and/or device-related complications. Note that 397 subjects met enrollment criteria after the EP study and received cryoablation. Mean ablation procedure duration (including a waiting period) was 89 ± 40minutes, and mean fluoroscopy time was 4.8 ± 5.9minutes. Isoproterenol was administered before cryoablation in 53% and after the last lesion in 85% of cases. Acute procedural success was realized in 95% (378 of 397) of subjects. No subject received a permanent pacemaker due to AV block. The slow pathway could not be ablated in 19 subjects, including: 12 due to inefficacy, 2 due to transient AV block, and 5 due to both inefficacy and transient AV block. RF ablation was used in the same procedure in 11 of 19 failed subjects, and was ineffective in 3 subjects. Among the group with acute success, 10 subjects (2.7%) had documented recurrent AVNRT over the 6-month follow-up period, and all occurred within 3 months of the index cryoablation. Serious procedure-related adverse events occurred in 4 subjects (1.0%), including one each: tamponade, pulmonary embolism, femoral vein hemorrhage, and diagnostic EP catheter knotting. None of these serious adverse events were related to use of the cryoablation catheter. Overall, 93% of subjects had successful slow pathway ablation at 6 months with the study cryoablation catheter. Cryoablation for AVNRT using a focal 6-mm catheter was safe and effective. It resulted in a low risk of recurrence over 6 months of follow-up with no incidence of AV block requiring permanent pacing.

Supraventricular tachycardia diagnosed by smartphone ECG

Diagnosis of paroxysmal supraventricular tachycardia (PSVT) may be difficult due to its episodic nature, which can be brief and self-limited, limiting the ability for clinicians to diagnose the specific rhythm...

Characterization of the Nodal Slow Pathway in Patients With Nodal Reentrant Tachycardia: Clinical Implications for Guiding Ablation

Introduction and objectivesNodal slow pathway ablation is the treatment of choice for nodal reentrant tachycardia. No demographic, anatomic, or electrophysiologic variables have been reported to predict an exact location of the slow pathway in the atrioventricular node or its proximity to the fast pathway. The purpose of this study was to analyze these variables. MethodsThe study prospectively included 54 patients (17 men; mean age, 55 [16] years) who had undergone successful slow pathway ablation. The refractory periods of both pathways and their differential conduction time were measured, and calculations were performed to obtain the distance from the His-bundle region (location of the fast pathway) to the coronary sinus ostium (to estimate the anteroposterior length of the triangle of Koch) and to the slow pathway area. ResultsThe differential conduction time (139 [98] ms) did not correlate with the His-coronary sinus distance (19 [6] mm; P=.6) or the His-slow pathway distance (14 [4] mm; P=.4). When the His-coronary sinus distance was larger, the His-slow pathway distance was also larger (r=0.652; P<.01) and the anatomic correlation between the triangle dimensions and the separation between the two pathways was confirmed. In patients older than 70 years, smaller triangle sizes and a shorter distance between both pathways were observed (P<.001). ConclusionsA greater anteroposterior dimension of the triangle of Koch is associated with a slow-pathway location farther from the fast pathway. In elderly patients the two pathways are closer together (higher risk of atrioventricular block).

Caracterización de la vía lenta nodular en pacientes con taquicardia por reentrada nodular: implicaciones clínicas para guiar la ablación

Introduction and objectivesNodal slow pathway ablation is the treatment of choice for nodal reentrant tachycardia. No demographic, anatomic, or electrophysiologic variables have been reported to predict an exact location of the slow pathway in the atrioventricular node or its proximity to the fast pathway. The purpose of this study was to analyze these variables. MethodsThe study prospectively included 54 patients (17 men; mean age, 55 [16] years) who had undergone successful slow pathway ablation. The refractory periods of both pathways and their differential conduction time were measured, and calculations were performed to obtain the distance from the His-bundle region (location of the fast pathway) to the coronary sinus ostium (to estimate the anteroposterior length of the triangle of Koch) and to the slow pathway area. ResultsThe differential conduction time (139 [98] ms) did not correlate with the His-coronary sinus distance (19 [6] mm; P=.6) or the His-slow pathway distance (14 [4] mm; P=.4). When the His-coronary sinus distance was larger, the His-slow pathway distance was also larger (r=0.652; P<.01) and the anatomic correlation between the triangle dimensions and the separation between the two pathways was confirmed. In patients older than 70 years, smaller triangle sizes and a shorter distance between both pathways were observed (P<.001). ConclusionsA greater anteroposterior dimension of the triangle of Koch is associated with a slow-pathway location farther from the fast pathway. In elderly patients the two pathways are closer together (higher risk of atrioventricular block).Full English text available from: www.revespcardiol.org/en

Slow pathway ablation for typical atrioventricular nodal re-entrant tachycardia significantly alters the autonomic modulation of atrioventricular conduction

Atrioventricular (AV) conduction turbulence, biphasic dromotropic response of AV node to single ventricular premature contraction (VPC), consists of early shortening and later prolongation of AV conduction intervals due to the direct electrophysiological mechanisms and perturbation in autonomic modulation. We investigated the acute effect of radiofrequency catheter ablation of slow pathway on AV turbulence. The electrophysiological study was performed in 18 patients (7 men, mean age 49±15years) undergoing catheter ablation for AV nodal reentrant tachycardia. The stimulation protocol consisting of series of isolated VPC (coupling interval of 273±23ms) delivered from right ventricle apex during constant atrial pacing at 100bpm was performed immediately prior to and 8±4min after successful slow-pathway ablation. Averaged post-VPCs profiles of AV conduction intervals were analyzed by purpose-written software. The descriptors of AV turbulence, turbulence onset (TOAV), turbulence slope (TSAV), and AV recovery (R AV) were assessed. Slow-pathway ablation suppressed the AV nodal responsiveness to VPC as evidenced by significant reduction of AV turbulence indices: TOAV: -6.4±7.5% vs. -4.3±6.1% (p<0.05); TSAV: 2.0±2.6ms/RRi vs. 1.0±0.7ms/RRi (p<0.05); and R AV: -13.8±7.3% vs. -6.5±12.7% (p<0.05). Slow-pathway ablation significantly attenuated both vagal and non-autonomic modulation of AV nodal conduction. This effect is likely due to direct thermal injury of AV node associated with the change of properties of AV nodal fast-pathway although specific alteration of peri-AV nodal ganglionated plexi or their neural inputs into the AV node cannot be excluded.

Ablation of slow pathway in a patient with persistent left superior vena cava

We describe a case of successful radiofrequency ablation of slow pathway in a 54 year-old woman with persistent left superior vena cava. The ablation was performed using anatomical approach, outside the ostium of coronary sinus.

Ivabradine in the Treatment of Inappropriate Sinus Tachycardia in Patients after Successful Radiofrequency Catheter Ablation of Atrioventricular Node Slow Pathway

Inappropriate sinus tachycardia (IST) occurs relatively common after catheter ablation of slow pathway in patients with atrioventricular nodal reentrant tachycardia. The treatment of IST symptoms using β-blockers or calcium channel-blockers are often noneffective or not well tolerated. Ivabradine is a new heart rate (HR)-decreasing agent inhibiting sinus node If current. The purpose of the study was to evaluate the efficacy and safety of ivabradine in patients with persistent and β-blocker-resistant IST after successful radiofrequency (RF) ablation of atrioventricular node slow pathway. We enrolled 14 patients (42 ± 11 years; 10 women) affected by IST after RF ablation. Holter monitoring, treadmill stress test, and IST symptoms assessment were performed at baseline and after first, and second month of the study. We observed significant reduction of mean resting HR after 30 and 60 days of ivabradine treatment compared to baseline (P < 0.001). 24-hour Holter monitoring showed a significant reduction of mean HR and mean HR during daily activity (P < 0.001). The study revealed significant improvement in exercise capacity during treadmill exercise test on ivabradine therapy (P < 0.001). Significantly lower incidence of IST-related symptoms were registered after administration of If current inhibitor. After 2 months of treatment no patients reported severe complaints assessed by means of European Heart Rhythm Association score. We did not observe severe side effects during therapy. Ivabradine is an effective treatment option to reduce HR and symptoms in patients with IST after RF ablation of atrioventricular node slow pathway. The therapy with ivabradine is well tolerated even with maximum daily dose.

Successful Slow Pathway Ablation in a Patient with a Rare Unroofed Type Coronary Sinus

We report a case of atrioventricular nodal reentrant tachycardia coexistent with a coronary sinus (CS) anomaly. During a standard electrophysiological study, the CS could not be cannulated despite several attempts. A persistent left superior vena cava angiogram through the left brachial vein confirmed an unroofed type CS. Successful slow pathway ablation from the right posterior paraseptum lesion was achieved using an anatomical approach.

Effects of Slow Pathway Ablation on Fast Pathway Function in Patients With Atrioventricular Nodal Reentrant Tachycardia

In typical atrioventricular nodal reentrant tachycardia, radiofrequency (RF) ablation of the slow pathway (SP) is known to change the effective refractory period of the fast pathway (ERP(FP)) after successful RF ablation of the SP. The purpose of this study was to ascertain the mechanism of the ERP(FP) changes after SP ablation by comparing the results of both cryo- and RF ablation. A total of 112 patients were enrolled prospectively and their electrophysiological properties analyzed before and after successful SP ablation. Patients were grouped into cryoablation (n=54) and RF ablation (n=58) groups and each group was subdivided into complete ablation (CG) and modification (MG) based on the presence of the SP after successful ablation. CG was performed in 64 patients: 30 by cryoablation and 34 by RF ablation. In patients who underwent complete SP ablation, the ERP(FP) was shortened significantly after cryoablation (375 ± 74 vs. 281 ± 39 ms, P<0.01), without significant change in the atrio-His (AH) or sinus cycle length (SCL) interval. Similarly, the ERP(FP) was shortened significantly (358 ± 106 vs. 289 ± 84 ms, P=0.01) also after RF ablation without change in AH or SCL interval. ERP(FP) shortening was observed after complete SP ablation with both cryo- and RF ablation without significant changes in indices of autonomic activity.

Noncontact Mapping Guided Ablation of Atrioventricular Nodal Reentrant Tachycardia in a Patient with Persistent Left Superior Vena Cava

We described a successful slow-pathway (SP) ablation in a 30-year-old woman with persistent left superior vena cava (PLSVC) guided by 3-dimensional noncontact-mapping (NCM) system. She presented with frequent episodes of poorly tolerated paroxysmal supraventricular tachycardia. The course of the CS catheter was unusual, and the presence of PLSVC with right superior vena cava atresia was documented by venography. The baseline electrophysiologic study indicated the presence of common type AV nodal reentrant tachycardia (AVNRT). By anatomical approach, SP ablation was initially performed in the posteroinferior region of Koch triangle near the CS ostium, but AVNRT was still inducible. In order to avoid extensive ablation and the risk of AV node injury, we introduced a multielectrode array catheter for a NCM approach. We determined the earliest atrial activation area of the retrograde conduction using ventricular extrastimulation. To locate the SP, a right ventricle extrastimulus pacing with S1S1 interval 500 ms, and S1S2 interval started from 450 ms with a 10 ms decrement. In this way, the retrograde slow and fast pathway can be identified from the earliest atrial activation with a rS pattern on the virtual electrograms. Successful ablation was achieved at the site of retrograde SP with an accelerated junctional rhythm observed during RF application. After slow pathway ablation, dual AV nodal physiology disappeared, and AVNRT became non-inducible.

Posterior His Bundle Electrogram Location in a Patient With Atrioventricular Nodal Reentrant Tachycardia and Structurally Normal Heart

Atrioventricular (AV) nodal reentrant tachycardia is the most common form of paroxysmal supraventricular tachycardia in adults, and slow AV nodal pathway ablation has evolved into first-line therapy. Variations in conduction system anatomy are occasionally found at electrophysiological study and may make this ablation procedure very challenging. Here, we present the case of a 69-year-old man with a structurally normal heart and posterior displaced His bundle who underwent successful slow pathway ablation. Demonstration of the characteristic slow pathway recording and His bundle electrogram is strongly recommended prior to radiofrequency energy application in the posterior septal region.

Selective slow pathway ablation using transseptal approach in a patient with surgically corrected partial atrioventricular canal defect and atrioventricular nodal reentrant tachycardia of the common type

A 26-year-old woman with partial atrioventricular (AV) canal defect surgically closed with pericardial patch in a mode that the triangle of Koch had become part of the left atrium underwent successful slow pathway ablation for slow-fast AV nodal reentrant tachycardia. Transseptal approach was used because of the atypical post-operative anatomy. Transseptal catheter ablation of the slow pathway can be a reasonable and safe alternative in patients subjected to this type of operation.

Successful slow pathway ablation in a patient with persistent left superior vena cava

Persistent left superior vena cava (PLSVC) is a rare vascular variant which can add difficulties to slow pathway (SP) ablation procedures because of the disturbed anatomy of the triangle of Koch. We describe a case of a successful SP ablation using an anatomical approach in a patient with PLSVC.