Retrograde Accessory Pathway Conduction Research Articles

Retrograde ventriculoatrial jump-What is the mechanism?

During ventricular extra stimuli(VES) protocol a VA jump was noted. In upper panel with VES @ 500/270 ms (Fig A) the His signal appeared after the A-EGM, ruling out pure nodal VA conduction and confirming presence of an accessory pathway (AP). The H signal was delayed due to probable retrograde RBBB. The atrium was already depolarised via AP and the VA traversing via left bundle-His-node got blocked with a H signal. In the lower panel with VES of 500/260 ms the retrograde AP conduction reached the effective refractory period and pure nodal VA conduction took place along with retrograde RBBB. The retrograde VA jump was hence due to a jump from AP to AV node.

Ultra-high resolution mapping and ablation of accessory pathway conduction.

Detailed mapping studies of accessory pathway (AP) conduction have not been previously performed using ultra-high resolution mapping systems. We sought to evaluate the clinical utility of ultra-high resolution mapping systems and the novel "Lumipoint" algorithm in AP ablation. This study included 17 patients who underwent AP mapping using minielectrode basket catheters and Rhythmia systems. Ablation was performed with 4-mm irrigated-tip catheters. Antegrade and retrograde AP conduction was observed in 6 and 16 patients. Atrial activation map was obtained during orthodromic tachycardia and ventricular pacing in 13 (76.5%) and 14 (82.3%) patients, and the earliest activation area was identical. Ventricular activation maps were created during atrial pacing in 3 patients. All maps showed focal activation patterns on global activation histograms, and the valley on the histogram highlighted the earliest activation area. "Complex activation" features further highlighted limited areas with continuous electrical activity during the time period in the majority. APs were located at the mitral and tricuspid annuli in 15 and 2 patients, and all were successfully eliminated with 3.4 ± 0.6s applications. No patients had recurrences during a median follow-up of 15 [10.5-22.5] months. At successful ablation sites, the local atrial and ventricular electrogram amplitudes and ratio tended to be greater, and fusion or continuous electrical activity between the atrial and ventricular components was more frequently observed on the minielectrode than ablation catheter (17/17 vs. 12/17, p = 0.005). Ultra-high resolution activation mapping and a novel algorithm facilitated the AP localization. The local electrogram characteristics differed between the minielectrode and ablation catheters.

Computer simulation of anterograde and retrograde accessory pathway conduction in WPW syndrome

Computer simulation of anterograde and retrograde accessory pathway conduction in WPW syndrome

Right free-wall accessory pathway with branched atrial insertions: Clinical, electrocardiographic, and electrophysiological characteristics

Right free-wall (RFW) accessory pathway (AP) with branched atrial insertions is a rare, underrecognized AP that may be associated with initial ablation failure. The purpose of this study was to investigate the clinical and electrophysiological characteristics of this AP. From January 2011 to March 2018, 10 patients identified with branched RFW-AP were enrolled in this study, and 30 consecutive patients with conventional RFW-APs served as control group. Right atrium (RA) was activation-mapped and 3-dimensionally reconstructed during AP-mediated orthodromic tachycardia or right ventricular pacing. Atrial insertions were defined as the earliest breakout sites, and their relationship with the tricuspid annulus (TA) were described and analyzed. An average of 3 separate atrial insertions on the atrial side were documented among these 10 cases (5 female and 5 male; mean age 38.0 ± 13.9 years). All atrial insertions were away from the TA. The nearest atrial insertions averaged 15.9 ± 3.4 mm away from the TA, and the farthest atrial insertions were 22.6 ± 5.7 mm away from the TA. Anterograde and retrograde AP conduction remained unaffected after ablation of the first earliest breakout site but were eliminated by ablating all insertions after an average of 2.5 (range 2-2.5) remaps, 3 sites of ablation (range 2.5-4.5), 21 (range 15.5-37.8) radiofrequency applications, and 659.5 (range 464.3-1144.3) seconds of radiofrequency ablation duration. After 12-month follow-up, no patients reported AP conduction recovery or recurrent tachycardia. RFW-AP with branched atrial insertions is an atypical AP variant and featured by >1 distinct atrial insertions on atrial side. Stepwise ablation rather than single focal ablation is required to eliminate all retrograde conduction.

Catheter ablation in children and patients with congenital heart disease: Review of 1021 procedures at a high-volume single center in Japan

Although pediatric catheter ablation therapy has often been described, few reports on outcomes in a large series of patients at a single center are available. The purpose of this study was to evaluate arrhythmia substrates, outcomes, and complications of catheter ablation in children and patients with congenital heart disease (CHD) performed at a single center. We retrospectively analyzed all pediatric patients <18 years and patients of all ages with CHD who underwent ablation therapy between June 2006 and May2018. A total of 1021 ablation procedures were performed in 877 patients (median age 12.5 years; range 2 months to 67 years). This cohort included 152 CHD patients, 90 small patients (<15 kg), and 14 infants (<1 year). The most frequent indication was Wolff-Parkinson-White pattern (WPW) (n = 287 [32.7%]). Of the 55 patients with asymptomatic WPW, 40 patients (72.7%) had retrograde accessory pathway conduction. Overall success and recurrence rates were 93.5% and 17.3%, respectively. Small patients and CHD patients had lower success rates. No deaths occurred. Serious complications occurred in 5 patients. Catheter ablation is safe and effective for treatment of arrhythmia in pediatric and CHD patients. However, ablation was less successful in small patients and CHD patients. The risk of complications was similar to those previously reported for catheter ablation in pediatric, CHD, and adult patients.

Validation of a novel automated signal analysis tool for ablation of Wolff-Parkinson-White Syndrome.

BackgroundIn previous pilot work we demonstrated that a novel automated signal analysis tool could accurately identify successful ablation sites during Wolff-Parkinson-White (WPW) ablation at a single center.ObjectiveWe sought to validate and refine this signal analysis tool in a larger multi-center cohort of children with WPW.MethodsA retrospective review was performed of signal data from children with WPW who underwent ablation at two pediatric arrhythmia centers from 2008–2015. All patients with WPW ≤ 21 years who underwent invasive electrophysiology study and ablation with ablation signals available for review were included. Signals were excluded if temperature or power delivery was inadequate or lesion time was < 5 seconds. Ablation lesions were reviewed for each patient. Signals were classified as successful if there was loss of antegrade and retrograde accessory pathway (AP) conduction or unsuccessful if ablation did not eliminate AP conduction. Custom signal analysis software analyzed intracardiac electrograms for amplitudes, high and low frequency components, integrated area, and signal timing components to create a signal score. We validated the previously published signal score threshold 3.1 in this larger, more diverse cohort and explored additional scoring options. Logistic regression with lasso regularization using Youden’s index criterion and a cost-benefit criterion to identify thresholds was considered as a refinement to this score.Results347 signals (141 successful, 206 unsuccessful) in 144 pts were analyzed [mean age 13.2 ± 3.9 years, 96 (67%) male, 66 (45%) left sided APs]. The software correctly identified the signals as successful or unsuccessful in 276/347 (80%) at a threshold of 3.1. The performance of other thresholds did not significantly improve the predictive ability. A signal score threshold of 3.1 provided the following diagnostic accuracy for distinguishing a successful from unsuccessful signal: sensitivity 83%, specificity 77%, PPV 71%, NPV 87%.ConclusionsAn automated signal analysis software tool reliably distinguished successful versus unsuccessful ablation electrograms in children with WPW when validated in a large, diverse cohort. Refining the tools using an alternative threshold and statistical method did not improve the original signal score at a threshold of 3.1. This software was effective across two centers and multiple operators and may be an effective tool for ablation of WPW.

Utility of Pre-Induction Ventriculoatrial Response to Adenosine in the Diagnosis of Orthodromic Reciprocating Tachycardia.

This study sought to evaluate the utility of ventriculoatrial (VA) conduction patterns in response to adenosine in predicting inducibility of orthodromic reciprocating tachycardia (ORT). Adenosine is known to consistently block atrioventricular (AV) nodal conduction. We hypothesized that persistent VA conduction despite administration of adenosine would have a high predictive value for identifying the presence of a retrograde accessory pathway (AP) and associated ORT. A total of 168 patients undergoing electrophysiological study for supraventricular tachycardia (SVT) had assessment of VA conduction during ventricular pacing and adenosine administration. Standard pacing maneuvers were then used for induction and diagnosis of the SVT mechanism. Absence of VA block to adenosine (doses up to 24 mg) had 88% sensitivity and 91% specificity for identifying ORT (positive predictive value 76%, negative predictive value 96%). Four patients with adenosine-induced VA block andinducible ORT had decremental APs. Adenosine caused VA block in 6 patients with eccentric VA activation due to atypical AV nodal conduction, and concentric VA conduction persisted in all 12 patients with a septal AP. Adenosine unmasked free-wall APs in 10 patients by blocking AV nodal conduction, shifting VA activation from concentric to eccentric. The response of VA conduction to adenosine is a highly sensitive and specific method for detecting retrograde AP conduction and inducible ORT. Adenosine-induced VA block rules out inducible ORT due to a nondecremental AP. In cases of VA fusion, adenosine-induced block of AV nodal conduction can delineate the location of the AP atrial insertion site.

Serial assessment of accessory pathway antegrade conduction in children

There is limited longitudinal data on accessory pathway (AP) antegrade conduction throughout childhood, with implications for risk stratification. Ten patients underwent serial electrophysiology study (EPS) with assessment of fastest 1:1 AP conduction. The median age at first and follow-up EPS was 0 (median 4days) and 53months. Median fastest 1:1 AP conduction was 255ms at initial EPS and 275ms at follow-up (P=0.24). The interval of time between studies had no influence on stability over time, nor was there any appreciable effect following changes in retrograde AP conduction. In conclusion, no patient displayed any marked shortening of 1:1 AP conduction over time.

ASSA14-02-11 Catheter ablation of anteroseptal accessory pathway: Implication for the strategies of mapping and ablation

<h3>Objective</h3> Catheter ablation of anteroseptal atrioventricular (AV) accessory pathway (AP) is still challenging because of their proximity to the normal AV conduction system that may be damaged with ablation. Traditionally, catheter ablation of anteroseptal APs via the inferior vena cava approach. In a few cases, anteroseptal AP ablation may fail because of conservative energy delivery at these sites or anatomical factor. In the recent years, a few cases of successful anteroseptal AP ablation in the noncoronary cusp (NCC) or sub tricuspid annulus have been reported. However, when need to map and ablate from the NCC or sub tricuspid annulus in patients with anteroseptal APs and what will be the mapping results at the NCC in patients with anteroseptal APs successful ablated in the, right anteroseptal region (RAS) have not been well evaluated. The purpose of this study was to discuss the characteristics of surface ECG, anatomic consideration, electrophysiology, and the strategy of ablation of anteroseptal APs in order to increase the success rate and safety of radiofrequency catheter ablation. <h3>Methods</h3> There were 55 consecutive patients (age 53 ± 11 years, 36 male) out of 2200 patients presenting with anteroseptal APs who underwent RF ablation at our centre between July 2006 and March 2013. On the basis of successful ablation location, these patients were divided into right anteroseptal region group (RAS group, through inferior vena cava approach), noncoronary cusp group (NCC group, through retrograde aorta approach) and sub tricuspid annulus group (Sub-TA group, throngh superior vena cava approach). The clinical characteristics, surface electrocardiogram (ECG), intracardiac electrogram findings, and response to ablation in these patients between three groups were analysed. The strategies for mapping and ablation of anteroseptal APs were discussed. <h3>Results</h3> Successful ablation were achieved in all the 55 patients with anteroseptal APs. The sites with successful ablation were located in the RAS, adjacent to the His bundle region, in 48 patients including in 9 patients whose initial ablation were unsuccessful in the NCC. In the 4 cases with successful ablation in the NCC, the initial attempt ablation in the NCC without trying in the RAS was performed in 1 cases in whom the decision to target the NCC was based on previous experience of V-A fusion pattern adjacent to the His bundle region suggestive of an NCC AP site. In 1 of the 4 patients, irrigated energy (30–40 W and infusion rate of 17–30 ml/min) was used to eliminated the AP in the NCC after failed ablation with non-irrigated energy. There were 3 cases underwent successful ablation at Sub-TA region by a superior approach from the right internal jugular vein. There were no important complications during perioperative period. All the patients underwent a period of 8 months to 7 years of follow-up by telephone or outpatient department. Four patents ablated in RAS region recurred. No recurrence in patients underwent successful ablation in NCC or Sub-TA region. <h3>Conclusions</h3> The results of catheter ablation of anteroseptal APs in a large case series indicate that anteroseptal APs in most patients can be successful ablated in RAS region, but in a few patients, anteroseptal APs need to be ablated from the NCC or Sub-TA region. The pre-excitation characteristics have no meaningful differences among the RAS, NCC and Sub-TA group. The incidence of anteroseptal AP which had to be ablated from NCC is relatively low, so ablation from NCC was not a preferential approach. The VA fusion pattern in RAS during retrograde AP conduction may be helpful to differentiate or predict successful ablation from RAS, NCC or Sub-TA in most patients with anteroseptal AP.

Mechanisms and clinical significance of adenosine-induced dormant accessory pathway conduction after catheter ablation.

Adenosine can unmask dormant pulmonary vein conduction after isolation. The role of adenosine in uncovering dormant accessory pathway (AP) conduction after AP ablation is unknown. We evaluated 109 consecutive patients (age, 41 ± 28 years; 62 [57%] men) who were administered adenosine after successful AP ablation. Dormant AP conduction was defined as adenosine-induced recurrent AP conduction, as demonstrated by recurrent preexcitation or change in retrograde ventriculoatrial activation patterns. Dormant AP conduction was identified in 13 (12%) patients. Adenosine led to transient retrograde AP conduction in 6 patients and transient anterograde AP conduction in 8 patients. In all these cases, adenosine-induced AP conduction occurred during the bradycardia phase of adenosine effect and resulted in dormant AP conduction times shorter than atrioventricular nodal conduction times before adenosine administration. On the basis of analysis of timing of occurrence of dormant AP conduction, the mechanism of adenosine-induced AP conduction was determined to be caused by AP excitability recovery in ≥ 12 (92%) cases. The presence of dormant AP conduction was a significant predictor of chronic recurrent AP conduction requiring repeat ablation (odds ratio, 8.54; 95% confidence interval, 1.09-66.9; P=0.041). Adenosine can unmask dormant AP conduction after catheter ablation. Direct effects of adenosine on the AP, possibly via AP membrane potential hyperpolarization, are the dominant mechanism of adenosine-induced AP conduction after ablation. Dormant AP conduction is associated with higher rates of recurrent AP conduction requiring repeat ablation.

Measurement of the ventriculoatrial interval from the coronary sinus during para-Hisian pacing may fail to distinguish ventriculoatrial nodal conduction from conduction over a septal accessory pathway

BackgroundPara-Hisian pacing (PHP) helps differentiate retrograde conduction over an accessory pathway (AP) from retrograde conduction over the atrioventricular (AV) node. This study examined a potential limitation of this technique, focusing on the measurement of the ventriculoatrial (V–A) interval from the coronary sinus (CS) during PHP. MethodsOur subjects were 9 patients undergoing electrophysiological studies before successful catheter ablation of a posteroseptal AP. During PHP, retrograde conduction occurred over an AP when the pacing stimulus to atrium (S–A) interval recorded near the AP remained unchanged whether the His bundle (HB) was captured or not (pattern 1), or when a loss of HB capture was associated with an increase in the S–A interval and no change in the V–A interval near the AP (pattern 2). ResultsPatterns 1 and 2 were observed in 5 (56%) and 2 (22%) patients, respectively. However, in the remaining 2 patients (22%), loss of HB capture during PHP was associated with an increase in the S–A interval (as in pattern 2), whereas the V–A interval near the AP could not be measured because no ventricular electrogram was visible on the CS recording (pattern 3); therefore, the presence of AP could not be confirmed by PHP. In patterns 2 and 3, the atrial activation sequence remained unchanged whether the HB was captured or not. ConclusionsPHP may not be able to discriminate between a retrograde septal AP and AV nodal conduction in patients whose proximal CS recording shows no visible ventricular electrogram.

Ablation of Right-Sided Accessory Pathways With Atrial Insertion Far From the Tricuspid Annulus Using an Electroanatomical Mapping System

It is difficult to ablate a right-sided accessory pathway (AP) with atrial insertion far from the tricuspid annulus (TA). We report our initial experience of ablating this rare AP by a 3-dimensional electroanatomical mapping system (CARTO). From January of 2006 to April of 2008, 18 patients with right-sided APs who failed previous outside ablations were enrolled in this study. Retrograde AP conduction was mapped during pacing at the right ventricular apex by activation-mapping the right atrium (RA) using a 3-dimensional electroanatomical mapping system. AP atrial insertion was defined as the earliest retrograde atrial activations and successful ablation of the APs at this site. Among the 18 patients who had failed previous ablation, 10 patients (7 patients with right manifest APs and 3 patients with right conceal APs) had atrial insertions far from the TA. Of the 10 patients, the atrial insertions were found at the base of the RA appendage in 3 patients, at the high lateral RA in 5 patients, at the low lateral RA in other 2 patients. Ablation at the atrial insertions successfully abolished the AP conduction. The mean distance between the atrial insertion sites and the TA was 20.2 ± 2.7 mm. No patients reported recovered AP conduction or recurrent tachycardias after 6-month follow-up. The right-sided APs may have atrial insertion far from the TA. These uncommon variation of APs can be reliably identified and ablated using CARTO system.

Measure twice, cut once: pitfalls in the diagnosis of supraventricular tachycardia.

In atrioventricular nodal and atrioventricular reentrant tachycardia, the relative timing of atrial and ventricular activation may sometimes be very similar, even during electrophysiological studies, and this may lead to an erroneous diagnosis and inappropriate treatment. As examples, we describe two cases that were recently referred to our hospital for a second opinion and treatment of paroxysmal supraventricular tachycardia. In both, the original diagnosis of the referring centres was commontype atrioventricular nodal reentrant tachycardia. Catheter ablation in those centres was unsuccessful. During our electrophysiological studies, however, an atrioventricular reentrant tachycardia was demonstrated, using a concealed accessory pathway for retrograde conduction in both patients. The accessory atrioventricular connection was successfully ablated and on follow-up both patients remained free of symptoms without medication. These findings illustrate the importance of complete electrophysiological analysis even for apparently simple supraventricular arrhythmias. (Neth Heart J 2010;18:78-84.).

Utilization of Retrograde Right Bundle Branch Block to Differentiate Atrioventricular Nodal from Accessory Pathway Conduction

Defining whether retrograde ventriculoatrial (V-A) conduction is via the AV node (AVN) or an accessory pathway (AP) is important during ablation procedures for supraventricular tachycardia (SVT). With the introduction of ventricular extrastimuli (VEST), retrograde right bundle branch block (RBBB) may occur, prolonging the V-H interval, but only when AV node conduction is present. We hypothesized that when AP conduction was present, the V-A interval would increase less than the V-H interval, whereas with retrograde nodal conduction, the V-A interval would increase at least as much as the V-H interval. We retrospectively reviewed the electrophysiological studies of patients undergoing ablation for AVN reentrant tachycardia (AVNRT) (55) or AVRT (50), for induction of retrograde RBBB during the introduction of VEST, and the change in the measured V-H and V-A intervals. Results were found to be reproducible between independent observers. Out of 105 patients, 84 had evidence of induced retrograde RBBB. The average V-H interval increase with induction of RBBB was 53.7 ms for patients with AVRT and 54.4 ms for patients with AVNRT (P = NS). The average V-A interval increase with induction of RBBB was 13.6 ms with AVRT and 70.1 ms with AVNRT (P < 0.001). All patients with a greater V-H than V-A interval change had AVRT, and those with a smaller had AVNRT. Induction of retrograde RBBB during VEST is common during an electrophysiological study for SVT. The relative change in the intervals during induction of RBBB accurately differentiates between retrograde AVN and AP conduction.

Electroanatomic Mapping of the Right Coronary Artery: A Novel Approach to Ablation of Right Free‐Wall Accessory Pathways

Catheter ablation of right free-wall (RFW) accessory pathways continues to be associated with lower success and higher recurrence rates compared with other pathway locations. Reliably identifying the precise location of RFW accessory pathways often contributes to the difficulty in ablating these pathways. Improved localization of RFW accessory pathways has been described utilizing multielectrode right coronary artery (RCA) catheterization. This approach has not been widely adopted, in part due to concerns of prolonged catheter placement within the RCA. We describe the technique of creating a 3-D electroanatomic map of the right atrioventricular groove, limiting the duration of a microcatheter within the RCA, to facilitate ablation of RFW accessory pathways. Following intracardiac identification of a RFW accessory pathway, an octapolar microcatheter was placed in the RCA. A 3-D electroanatomic map of the RCA was created during retrograde accessory pathway conduction using ventricular pacing. Immediately following creation of the map, the RCA catheter was removed. Endocardial mapping and ablation of the RFW accessory pathway was performed using the RCA electroanatomic map as a guide. This technique was used in four pediatric patients. The microcatheter was within the RCA for less than 1 min in all patients. Radiofrequency catheter ablation of the RFW accessory pathways were successfully performed with two lesions. There were no complications or recurrences at follow-up. The creation of a 3-D electroanantomic map of the RCA effectively localizes RFW accessory pathways and facilitates successful ablation. This technique minimizes the duration of RCA instrumentation.

Abstract 637: Utilization of Retrograde Right Bundle Branch Block to Differentiate Atrio Ventricular Nodal from Accessory Pathway Conduction

Determining whether retrograde ventriculoatrial (VA) conduction is through the AV node (AVN) or an accessory pathway (AP) is critical for successful ablation of supraventricular tachycardia (SVT). With introduction of ventricular extrastimuli (VEST), retrograde right bundle branch block (retro RBBB) may occur and result in abrupt VH interval prolongation. We hypothesized when retrograde conduction is via an AP, VA interval change is less than VH interval change, whereas with retrograde AVN conduction, VA interval change is equal to or greater than VH interval change. We retrospectively reviewed the electrophysiology (EP) studies of patients undergoing ablation for AVNRT (n=55) or AVRT (n=50). The intracardiac electrograms were reviewed for induction of retro RBBB and change in VH and VA intervals during VEST. Parahisian pacing, decremental pacing, arrhythmia diagnosis and ablation outcomes were reviewed. All results were found to be reproducible between two independent observers with inter and intra observer reliability scores of 1.00 for identification of retro RBBB and greater than 0.85 for measurement of VH and VA intervals. Of 105 patients, 84 (80%) had evidence of induced retro RBBB during VEST. The average VH interval increase with induction of retro RBBB was 53.7 ms for patients with retrograde AP conduction and 54.4 ms for patients with AVN conduction (p=ns). The average VA interval increase with induction of retro RBBB was 13.6 ms with AP conduction and 70.1 ms with AVN conduction (P &lt; 0.001). All patients with a greater VH than VA interval change had a final diagnosis of AVRT and those with a VH change less than VA change had AVNRT, yielding sensitivity and specificity of 100%. Using a cutoff of 50 ms for change in VA interval with onset of retro RBBB to diagnose AVNRT accurately identified AVNRT in 100% and AVRT in 95%. Induction of retro RBBB during VEST is common during EP studies for SVT. The relative change in the VH and VA intervals during retro RBBB accurately differentiates retrograde AVN from retrograde AP conduction with strong predictive accuracy. The use of retro RBBB based intervals is a useful technique facilitating the diagnosis of SVT in the EP laboratory, even in the absence of inducible tachycardia.

A Single Mahaim Fiber Causing Both Antidromic and Orthodromic Reciprocating Tachycardia

We describe the case of a 56-year-old woman referred for electrophysiological (EP) testing for medically refractory supraventricular arrhythmias. During the EP study, the patient was found to have a right free wall atriofasicular (Mahaim type) accessory pathway and an inducible left bundle morphology preexcited tachycardia secondary to antidromic reciprocating tachycardia. The patient also had an inducible narrow complex orthodromic reciprocating tachycardia (ORT). Mapping revealed that the earliest site of retrograde atrial activation during ORT was along the lateral tricuspid annulus. This was the same location where the atriofasicular accessory pathway potential was recorded during sinus rhythm. Radiofrequency ablation at this site eliminated inducibility of both tachycardias and any evidence of antegrade or retrograde accessory pathway conduction. This report describes the case of a very rare right free wall Mahaim type fiber with both antegrade and retrograde conduction capabilities responsible for both antidromic and ORT.

Double potentials at successful catheter ablation site of left-sided retrograde accessory pathway: Mitral isthmus block or conduction through coronary sinus musculature

Introduction We studied three patients who had orthodromic atrioventricular reentrant tachycardia (AVRT) using left lateral accessory pathway (AP), with difficulty in identifying the earliest site of retrograde atrial activation. Methods and results Electrophysiological studies and radiofrequency ablation were performed in three patients with refractory AVRT (Case 1 was a 42-year-old woman, Cases 2 and 3 were a 52- and a 40-year-old man, respectively). During AVRT, a prolonged ventriculoatrial (VA) interval (100–180 ms) and nearly simultaneous excitation of both distal and proximal coronary sinus (CS) sites were observed. During both AVRT and ventricular pacing, double atrial potentials were recorded in all patients. Ablation of the mitral annular site showing double atrial potentials (with the first component being present just after the ventricular potential at the left lateral atrioventricular annulus) eliminated retrograde AP conduction. In Cases 1 and 2 the first component of the double potentials was atrial activation conducted through AP distal to mitral isthmus block and the second component was activation proximal to block that conducted turning around the left-sided pulmonary veins. In Case 3 the first component was CS musculature activation conducted through AP and the second component was left atrium activation via CS musculature. Conclusion In AVRT that has a long VA interval and difficulty in identifying the earliest site of retrograde atrial activation, two different mechanisms existed (mitral isthmus block and conduction through CS musculature). Careful mapping of double atrial potentials and continuous VA activation at the left lateral mitral annulus is essential for determination of a successful ablation site.

Successful Elimination of Concealed Accessory Pathway‐Mediated Tachycardia by Ablation of AV Nodal Slow Pathway

We report a case of atrioventricular reentrant tachycardia (AVRT) using a concealed para-Hisian accessory pathway for retrograde conduction, which also required anterograde conduction over the AV nodal slow pathway to maintain the tachycardia. The shortest VA interval during AVRT (70 ms) was noted at a site with His bundle electrogram amplitude of 0.25 mV. The AVRT was cured by radiofrequency ablation of the AV nodal slow pathway without affecting accessory pathway conduction. The patient has not reported any sustained palpitations at 2 years after ablation while receiving no medications. The case presented in this report illustrates a para-Hisian AVRT that was successfully eliminated by an unconventional approach of ablation of the atrial inputs to the AV nodal slow pathway.

Flutter-Like P Waves in a Case of Atrioventricular Reciprocating Tachycardia

Typical atrial flutter is characterized by its sawtooth flutter wave in leads II, III, aVF, and V1. Atrioventricular reciprocating tachycardia is characterized by its small retrograde P wave after completion of QRS complex, where sawtooth flutter-like P waves are rarely seen in the electrocardiogram during atrioventricular reciprocating tachycardia. We report on a 62-year-old patient who presented the characteristic sawtooth flutter-like P waves in the electrocardiogram during attack of supraventricular tachycardia. By electrophysiologic study, the mechanism of his supraventricular tachycardia was atrioventricular reciprocating tachycardia using the left posterior lateral concealed accessory pathway for retrograde conduction. The accessory pathway was successfully ablated by radiofrequency ablation therapy.