Retrograde Atrioventricular Nodal Research Articles

An observational study on efficacy of atrioventricular nodal slow pathway ablation in patients with atrioventricular nodal reentrant tachycardia and its influence on atrioventricular conduction function.

The study aimed to evaluate the effectiveness of atrioventricular nodal slow pathway ablation in patients with atrioventricular nodal reentrant tachycardia (AVNRT) and examine its impact on the atrioventricular conduction function. A retrospective analysis was performed on the clinical data of 90 AVNRT patients who underwent radiofrequency ablation at our institution between August 2018 and February 2021. Based on the presence or absence of slow pathway conduction during the procedure, patients were classified into the slow pathway elimination group (SPE group) and the slow pathway improvement group (SPI group). Procedure-related parameters, His bundle electrogram, atrioventricular nodal effective refractory period (AVN-ERP), Wenckebach point of anterograde atrioventricular nodal conduction (AVN-WKB), Wenckebach point of retrograde atrioventricular nodal conduction (VAV-WKB), myocardial function were compared between the 2 groups. Additionally, the recurrence rates 1 and 2 years post-ablation were noted. Both groups reported a 100% success rate for the procedure. Post-ablation, 42 patients exhibited persisting atrioventricular nodal slow pathway, whereas 48 showed its disappearance, signifying the absence of the jump phenomenon and atrial echo. Post-ablation, the SPI group showed an increase in slow pathway AVN-ERP compared to pre-ablation values (P < .05), with no significant change in the fast pathway AVN-ERP (P > .05). The SPE group showed a reduction in both slow pathway and fast pathway AVN-ERP post-ablation (P < .05). Post-ablation, both slow pathway and fast pathway AVN-ERP in the SPI group were higher than in the SPE group (P < .05). AVN-WKB and VAV-WKB values increased in both groups after ablation (P < .05). There were no recurrences 1 or 2 years after ablation in the SPE group and 1 case of recurrence 2 years after ablation in the SPI group (2.38%). Different ablation endpoints during radiofrequency ablation had no apparent impact on atrioventricular conduction time, recurrence rate, and myocardial function in patients with AVNRT, but they advanced AVN-WKB and VAV-WKB. Slow pathway improvement led to an elongation of slow pathway AVN-ERP, while slow pathway elimination resulted in a reduction of both slow pathway and fast pathway AVN-ERP.

Landiolol, an intravenous β1-selective blocker, is useful for dissociating a fusion of atrial activation via accessory pathway and atrioventricular node.

During ventricular pacing, a fusion of atrial activation may occur owing to the simultaneous retrograde conduction of the atrioventricular (AV) node and accessory pathway (AP), potentially leading to an inaccurate mapping of the atrial AP insertion site. We tested the hypothesis that landiolol, an ultra-short-acting intravenous β1-blocker, could dissociate a fusion of atrial activation. We conducted a prospective before-and-after study to investigate the effect of landiolol on retrograde conduction via the AV node and AP. We enrolled 21 consecutive patients with orthodromic AV reciprocating tachycardia who underwent electrophysiological studies at our hospital between January 1, 2018, and August 31, 2020. Six patients exhibited a fusion of atrial activation. After landiolol administration (10 μg/kg/min), the effective refractory period was unchanged in AP (280 [240-290] ms vs. 280 [245-295] ms, p = .91), whereas that of the AV node was prolonged (275 [215-380] ms vs. 332 [278-445] ms, p = .03). The Wenckebach pacing rate via retrograde AV node decreased after landiolol administration (180 [140-200] beats per minute [bpm] vs. 140 [120-180] bpm, p = .02). Thus, landiolol decreased the minimum ventricular pacing rate required to dissociate a fusion of atrial activation (180 [160-200] bpm vs. 140 [128-155] bpm, p = .007). Radiofrequency catheter ablation under landiolol administration successfully eliminated AP in all patients during ventricular pacing without complications or recurrence. Landiolol inhibited the AV node without affecting the AP and helped dissociate a fusion of atrial activation at a lower ventricular pacing rate.

A clue to the triples from an echo.

A clue to the triples from an echo.

ECG Response: December 22/29, 2015

HomeCirculationVol. 132, No. 25ECG Response: December 22/29, 2015 Free AccessResearch ArticlePDF/EPUBAboutView PDFView EPUBSections ToolsAdd to favoritesDownload citationsTrack citationsPermissions ShareShare onFacebookTwitterLinked InMendeleyReddit Jump toFree AccessResearch ArticlePDF/EPUBECG Response: December 22/29, 2015 Originally published22 Dec 2015https://doi.org/10.1161/CIRCULATIONAHA.115.020213Circulation. 2015;132:2423ECG Challenge: A 65-year-old man with a history of hypertension being treated with a β-blocker presents to his physician for a routine physical examination. His pulse is noted to be slower than usual; hence, an ECG is obtained.Download figureDownload PowerPointThere is a regular rhythm at a rate of 48 bpm. The QRS complex duration is normal (0.08 second), and there is a normal morphology, as well as an axis between 0° and 90° (positive QRS complex in leads I and aVF). The QT/QTc intervals are normal (440/390 milliseconds). P waves are seen (+), but there is no relationship to the QRS complexes; that is, there are variable PR intervals. This represents atrioventricular dissociation. The P waves are positive in leads I, II, aVF, and V4 through V6. Hence, there is an underlying sinus rhythm. Most of the PP intervals are constant (└┘) with a rate of 75 bpm. There are 2 causes of atrioventricular dissociation: complete (third-degree) heart block in which the atrial rate is faster than the rate of the QRS complexes or an accelerated lower pacemaker (ie, junctional or ventricular) in which the atrial rate is slower than the rate of the QRS complexes. This is therefore complete heart block, and the escape rhythm is junctional. The etiology of the escape rhythm is not based on the rate of the escape rhythm but it established by the QRS morphology, which in this case is normal. There are 2 longer PP intervals (↔). Each of these longer PP intervals is associated with a QRS complex (third, fourth, and sixth; [v]) that has a slightly different morphology as a result of a negative deflection that is seen after these QRS complexes (^). This represents a retrograde P wave, a result of ventriculoatrial conduction associated with the junctional complex. As a result of retrograde atrial activation, the sinus node is reset, accounting for the long PP interval. Although there is complete atrioventricular block, ventriculoatrial conduction may be seen in up to 40% of cases. This is attributable to different antegrade and retrograde atrioventricular nodal conduction parameters; dual atrioventricular nodal pathways, 1 of which is capable of ventriculoatrial conduction; or the presence of a concealed bypass tract that conducts only in a retrograde fashion.In addition, 2 premature P wave (*) have a morphology that is different from the morphology of the sinus P waves. These are premature atrial complexes that are not conducted, that is, blocked premature atrial complexes. These non conducted P waves can also reset the sinus node automaticity.Please go to the journal’s blog, OpenHeart, for more ECG Challenges: http://goo.gl/tQPNFp. Challenges are posted on Tuesdays and Responses on Wednesdays.FootnotesCorrespondence to Philip J. Podrid, MD, West Roxbury VA Hospital, Section of Cardiology, 1400 VFW Pkwy, West Roxbury, MA 02132. E-mail [email protected] Previous Back to top Next FiguresReferencesRelatedDetailsCited By Kim H, Lee C, Lee H and Yang H EUU FTA (EU's FTA Strategies in Its New Trade Policy Initiatives and Policy Implications), SSRN Electronic Journal, 10.2139/ssrn.2946654 December 1, 2015Vol 132, Issue 25 Advertisement Article InformationMetrics © 2015 American Heart Association, Inc.https://doi.org/10.1161/CIRCULATIONAHA.115.020213PMID: 26700009 Originally publishedDecember 22, 2015 PDF download Advertisement

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.

Differential sequential septal pacing: A simple maneuver to differentiate nodal versus extranodal ventriculoatrial conduction

Distinguishing retrograde nodal conduction from extranodal conduction using an accessory pathway (AP) can sometimes be challenging. To distinguish nodal from extranodal ventriculoatrial (VA) conduction regardless of AP location by proposing a simple method. This method is based on the principle that moving the pacing site progressively from the basal region toward the entrance of the His-Purkinje system should shorten VA time for nodal but not for AP conduction. Sixty-seven patients with supraventricular tachycardia were prospectively recruited. Quadripolar catheters were placed at the right ventricular (RV) apex, right atrium, and His and coronary sinus. The RV septum was sequentially paced at 4 sites: (1) basal, (2) high midventricle, (3) low midventricle, and (4) apex at a cycle length 100 ms shorter than the resting cycle length. The stimulus-to-atrial (SA) interval was measured by using the proximal coronary sinus atrial electrogram. Group 1 (n = 33) had nodal VA conduction; all patients had typical atrioventricular nodal reentrant tachycardia. Group 2 (n = 34) had extranodal VA conduction via an AP: 19 left-sided, 6 right-sided, and 9 posteroseptal. In group 1, the SA interval decreased significantly as pacing site moved closer toward the apex (site 1: 166 ± 35 ms, site 2: 153 ± 32 ms, site 3: 149 ± 32 ms, site 4: 154 ± 33 ms, P < .001, respectively, at sites 2-4 compared with site 1). In contrast, in group 2, the SA interval increased significantly toward the apex (site 1: 149 ± 45 ms, site 2: 158 ± 43 ms, site 3: 161 ± 43 ms, and site 4: 163 ± 40 ms, P < .001, respectively, at sites 2-4 compared with site 1). The SA interval at the high midventricular site (site 2) - SA interval at the base (site 1) ≤ 0 ms for nodal and > 0 ms for extranodal conduction had optimal sensitivity and specificity (nodal: selectivity = 97.0% and specificity = 85.3%; extranodal: selectivity = 85.3% and specificity = 97.0%). Differential sequential pacing of the RV septum reliably distinguishes retrograde atrioventricular nodal conduction from AP conduction.

第19回 臨床不整脈研究会 僧帽弁輪後壁の減衰伝導特性を有する潜在性副伝導路に,逆行性房室結節左側伝導路を合併しアブレーションに難渋したlong RP'tachycardiaの1例

第19回 臨床不整脈研究会 僧帽弁輪後壁の減衰伝導特性を有する潜在性副伝導路に,逆行性房室結節左側伝導路を合併しアブレーションに難渋したlong RP'tachycardiaの1例

Atrioventricular Nodal Reentrant Tachycardia

Atrioventricular nodal reentrant tachycardia (AVNRT) represents the most common regular supraventricular arrhythmia in humans.1 The precise anatomic site and nature of the pathways involved have not yet been established, and several attempts to provide a reasonable hypothesis based on anatomic or anisotropic models have been made.2 There has been considerable evidence that the right and left inferior extensions of the human atrioventricular (AV) node and the atrionodal inputs they facilitate may provide the anatomic substrate of the slow pathway, and a comprehensive model of the tachycardia circuit for all forms of AVNRT based on the concept of atrionodal inputs has been proposed.2 Still, however, the circuit of AVNRT remains elusive. Recently, time-honored conventional schemes for the diagnosis and classification of the various forms of the arrhythmia have been refuted in part by evolving evidence. Recognition of the various types of AVNRT is important, however, to expedite diagnosis and allow implementation of appropriate ablation therapy without complications. We present an update on AVNRT with a particular emphasis on electrophysiological criteria used for the differential diagnosis of regular, supraventricular tachycardias. Typically, AVNRT is a narrow-complex tachycardia, ie, QRS duration <120 ms, unless aberrant conduction, which is usually of the right bundle-branch type, or a previous conduction defect exists. Tachycardia-related ST depression and RR-interval variation may be seen. RR alternans in AVNRT has been attributed to the proposed model of a figure of 8 reentry with continuous crossing over of antegrade activation through an inferior input to the contralateral superior input via the node.2 In the typical form of AVNRT (slow-fast), abnormal (retrograde) P′ waves are constantly related to the QRS and in the majority of cases are indiscernible or very close to the QRS complex (RP′/RR <0.5). Thus, P′ waves are either masked by the QRS complex or …

Predictors of Complete Heart Block After Transcoronary Ablation of Septal Hypertrophy: Results of a Prospective Electrophysiological Investigation in 172 Patients With Hypertrophic Obstructive Cardiomyopathy

This study analyzed changes in intracardiac conduction during transcoronary ablation of septal hypertrophy (TASH) to identify predictors for pacemaker dependency after TASH. Transcoronary ablation of septal hypertrophy is an accepted therapeutic option in hypertrophic obstructive cardiomyopathy (HOCM). However, atrioventricular conduction disorders, requiring permanent pacemaker implantation, remain a major adverse effect. This study measured changes in intracardiac conduction in 172 consecutive patients during TASH by simultaneously recording electrophysiological parameters and correlated these parameters with the occurrence of complete heart block during continuous electrocardiographic monitoring for 8 days. Intraprocedural complete heart block occurred in 36 patients (20.1%) and was associated with a pre-existing bundle branch block (p = 0.010) or advanced age (p = 0.023). All patients with delayed complete heart block during follow-up (n = 15, 8.7%), occurring 1 to 6 days after TASH, showed lack of retrograde atrioventricular nodal conduction after TASH (p = 0.018). None of the patients with intact retrograde conduction after TASH developed delayed complete heart block. Further risk factors for delayed block were advanced age, intraprocedural complete heart block, and prolonged QRS duration before or after TASH (p < 0.05 for all). Permanent pacemaker implantation was performed in 20 patients. Measurement of intracardiac conduction during TASH improves the safety of the procedure by enabling identification of patients who are at risk of complete heart block after TASH. The duration of prophylactic temporary pacemaker backup should be prolonged up to day 6 after TASH in patients at increased risk (patients with retrograde atrioventricular block and at least 1 additional risk factor).

The Different Ablation Effects on Atrioventricular Nodal Reentrant Tachycardia in Children with and without Dual Nodal Pathways

Previous studies in adults have shown a significant shortening of the fast pathway effective refractory period (ERP) after successful slow pathway ablation. However, information on atrioventricular nodal reentrant tachycardia (AVNRT) in children is limited. The purpose of this retrospective study was to investigate the different effects of radiofrequency (RF) catheter ablation in pediatric AVNRT patients between those with and without dual atrioventricular (AV) nodal pathways. From January 1992 to August 2004, a total 67 pediatric patients with AVNRT underwent an electrophysiologic study and RF catheter ablation at our institution. We compared the electrophysiologic characteristics between those obtained before and after ablation in the children with AVNRT with and without dual AV nodal pathways. Dual AV nodal pathways were found in 37 (55%) of 67 children, including 36 (54%) with antegrade and 10 (15%) with retrograde dual AV nodal pathways. The antegrade and retrograde fast pathway ERPs in children with dual AV nodal pathways were both longer than the antegrade and retrograde ERPs in children without dual AV nodal pathways (300 +/- 68 vs 264 +/- 58 ms, P = 0.004; 415 +/- 70 vs 250 +/- 45 ms, P < 0.001) before ablation. In children with antegrade dual AV nodal pathways, the antegrade fast pathway ERP decreased from 300 +/- 68 ms to 258 +/- 62 ms (P = 0.008). The retrograde fast pathway ERP also decreased after successful ablation in the children with retrograde dual AV nodal pathways (415 +/- 70 vs. 358 +/- 72 ms, P = 0.026). The dual AV nodal physiology could not be commonly demonstrated in pediatric patients with inducible AVNRT. After a successful slow pathway ablation, the fast pathway ERP shortened significantly in the children with dual AV nodal pathways.

AB24-5: A novel pacing maneuver to identify the presence of a slowly conducting concealed accessory pathway

In the presence of retrograde atrioventricular (AV) nodal conduction, the use of ventricular (V) pacing to identify the presence of a concealed accessory pathway (AP) with slower retrograde conduction is limited. Use of standard V extrastimuli requires that the effective refractory period (ERP) of the AP is shorter than the ERP of the AV node. We describe a novel maneuver for identification of slowly conducting retrograde accessory pathways in the setting of faster retrograde AV nodal conduction.

In vivo recording of monophasic action potentials in awake dogs

Assessment of cardiac repolarization in dogs in vivo is of interest in numerous experimental canine models. Previous studies have used monophasic action potentials (MAPs) to investigate repolarization in vitro and in vivo in anesthetized animal models. Therefore, an approach for recording MAPs in awake dogs without the interference of anesthesia is desirable. We describe an experimental technique to record MAPs in conscious dogs by means of conventional rubber introducers which are implanted into the internal jugular vein. Atrial as well as ventricular MAPs can be simultaneously measured without complications. Pacing thresholds are low and stable over time. Continuous MAP recordings of stable amplitude can be achieved from the same endocardial site for periods up to 1 h. Antegrade and retrograde atrioventricular nodal conduction properties can be assessed. Programmed stimulation can be performed to simultaneously determine local refractory periods and MAP duration at cycle lengths from 500 to 200 ms. In awake, unsedated dogs measuring MAPs via rubber introducers permits safe, long-term recording of MAPs. Such recordings may be useful for safety pharmacologic studies in evaluating cardiovascular and noncardiovascular drugs with respect to their effects on repolarization. In various canine in vivo models including in vivo models of long QT syndrome, heart failures or sudden cardiac death, the present technique permits electrophysiologic measurements without the interference of anesthesia.

Electrophysiologic characteristics of diverse accessory pathway locations of antidromic reciprocating tachycardia

This study assessed antidromic reciprocating tachycardia (ART) in patients with paraseptal accessory pathways (APs). Previous clinical experience suggests that paraseptal APs are unable to serve as the anterograde limb during ART. Based on the reentry wavelength concept, we hypothesized that anatomic location of a paraseptal AP may not preclude occurrence of ART. If wavelength criteria were met due to prolonged conduction time retrogradely in the atrioventricular node or anterogradely in the AP, ART may be sustained. All patients who had ART in the electrophysiologic laboratory at our institution (1991 to 1998) were studied. Based on fluoroscopically guided electrophysiologic mapping and radiofrequency ablation, AP location was classified as paraseptal, posterior, or lateral. Conduction time and refractoriness measurements were made for all components of the ART circuit. Of 24 patients with ART, 5 (21%) had ART utilizing a paraseptal AP. Anterograde conduction time through the AP and retrograde atrioventricular nodal conduction time were significantly longer in patients with paraseptal versus lateral pathways. Isoproterenol was required for ART induction in 38% of patients with a posterior AP, 36% with lateral AP location, but not in patients with a paraseptal AP. There were no significant differences in tachycardia cycle length or refractoriness of anterograde and/or retrograde components of the macroreentry circuit between the 3 pathway locations. Thus, ART can occur in patients with a paraseptal AP. Slower anterograde pathway conduction, or retrograde atrioventricular nodal conduction renders the wavelength critical for completion of the antidromic reentrant circuit.

Variable effects of adenosine on retrograde conduction in patients with atrioventricular nodal reentry tachycardia.

Adenosine has been demonstrated to reliably produce transient block of atrioventricular nodal (AVN) conduction, and has been advocated as a method of differentiating retrograde conduction via the atrioventricular node from accessory pathway conduction. However, the response of retrograde AVN to adenosine in patients with typical atrioventricular nodal reentry tachycardia (AVNRT) remains unclear. We evaluated 13 patients (mean age 45 +/- 20 years) with typical AVNRT prior to AVN modification. During right ventricular pacing, a rapid bolus of adenosine (0.2 mg/kg; maximum 18 mg) was administered. Adenosine sensitivity, defined by transient ventriculoatrial block, was observed in six patients, while in seven patients ventriculoatrial conduction was unaffected. An adenosine bolus administered during sinus rhythm or atrial pacing resulted in antegrade atrioventricular block in all the adenosine resistant patients in whom this was performed (n = 6). Comparisons of AVN electrophysiological characteristics between the adenosine sensitive and adenosine resistant patients were performed. There was no difference with respect to ventriculoatrial effective refractory period, ventriculoatrial Wenckebach, AVNRT cycle length, and His to atrial echo interval in AVNRT. However, there was a trend toward a longer antegrade fast pathway ERP in the adenosine sensitive group (P = 0.07). Electrophysiological properties do not predict retrograde AVN adenosine sensitivity. Adenosine does not cause retrograde AVN block in all patients with AVNRT, and therefore cannot reliably distinguish between retrograde conduction via the AVN or an accessory pathway.

Clinical and Electrophysiologic Characteristics and Long-Term Efficacy of Slow-Pathway Catheter Ablation in Patients With Spontaneous Supraventricular Tachycardia and Dual Atrioventricular Node Pathways Without Inducible Tachycardia

Objectives. We sought to investigate the long-term efficacy of slow-pathway catheter ablation in patients with spontaneous, documented paroxysmal supraventricular tachycardia (PSVT) and dual atrioventricular (AV) node pathways but without inducible tachycardia.Background. The lack of reproduction of clinical PSVT by programmed electrical stimulation, which is not uncommon in AV node reentrant tachycardia (AVNRT), is a dilemma in making the decision of the therapeutic end point of radiofrequency catheter ablation.Methods. Twenty-seven patients (group A) with documented but noninducible PSVT and with dual AV node pathways were prospectively studied. Programmed electrical stimulation could induce a single AV node echo beat in 12 patients, double echo beats in 4 patients and none in 11 patients at baseline or during isoproterenol infusion. Of the patients in group A, 16 underwent slow-pathway catheter ablation and 11 did not. The clinical and electrophysiologic characteristics of the 27 patients were compared with those of patients with dual AV node pathways and inducible AVNRT (group B, n = 55) and patients with dual AV node pathways alone without clinical PSVT (group C, n = 47).Results. During 23 ± 13 months of follow-up, none of the 16 patients with slow-pathway catheter ablation had recurrence of PSVT. However, 7 of the 11 patients without ablation had PSVT recurrence at 13 ± 14 months of follow-up (p < 0.03 by Kaplan-Meier analysis). Compared with groups B and C, group A consisted predominantly of men who had better retrograde AV node conduction and a narrower zone for anterograde slow-pathway conduction.Conclusions. Slow-pathway catheter ablation is highly effective in eliminating spontaneous PSVT in which the tachycardia is not inducible despite the presence of dual AV node pathways.

Effects of 2,3-butanedione monoxime on atrial-atrioventricular nodal conduction in isolated rabbit heart.

2,3-Butanedione monoxime (BDM) has been found to reversibly block cardiac contraction, without blocking electrical conduction. This study characterizes the dose-dependent effects of BDM on the conduction through the atrioventricular node (AVN) of rabbit heart. Thirteen isolated atrial-AVN preparations were used in control, during and after exposure to 5, 10, and 20 mM BDM. Anterograde and retrograde pacing protocols were used to obtain the Wenckebach cycle length, effective and functional refractory periods of the AVN, index of AVN conduction delay (the area under the AVN conduction curve), as well as index of intra-atrial conduction delay between the AVN inputs. Compared to control, 5 and 10 mM BDM produced either shortening or no effect on all of the above parameters except a slight (6% and 14%, respectively) increase in the intra-atrial delay. At 20 mM, BDM produced a further increase in the intra-atrial delay (up to 50%) as well as in the retrograde AVN conduction delay (up to 16%), while the characteristics of the anterograde conduction were still improved. The effects of perfusion with BDM on these parameters were reversible after washout. Aside from its known effect as an electromechanical uncoupler, BDM reversibly altered some of the electrical responses of the AVN. Most of these alterations, however, did not impede but rather improved AVN conduction. Since a dose of 10 mM is sufficient to fully eliminate undesirable motion, BDM should be considered a safe and valuable tool in AVN studies in vitro requiring a mechanically quiescent preparation.

Modification of atrioventricular nodal electrophysiology by selective radiofrequency delivery on the anterior or posterior approaches.

An analysis was made in 14 isolated and perfused rabbit hearts of the electrophysiological effects of selective radiofrequency (RF) delivery in the anterior (group I, n = 7) or posterior zone (group II, n = 7) of the Koch triangle, with the aim of modifying atrioventricular nodal (AVN) conduction without suppressing 1:1 transmission. After opening the right atrium, RF was delivered (0.5 W) with a 1-mm diameter unipolar electrode positioned in the selected zone until a prolongation of no less than 15% was obtained in the Wenckebach cycle length (WCL). Before and after (30 min) RF, anterograde and retrograde AVN refractoriness and conduction were evaluated, stimulating from the crista terminalis (CT), the interatrial septum (IAS), and from the RV epicardium. After RF, the following percentage increments were observed in group I: AH(CT) = 36% +/- 9%, AH(IAS) = 38% +/- 11%, WCL(CT) = 28% +/- 8%, WCL(IAS) = 22% +/- 6%, functional refractory period (FRP) of the AVN(CT) = 13% +/- 11%, FRP-AVN(IAS) = 13% +/- 8%, retrograde WCL = 20% +/- 19%, and retrograde FRPVA = 13% +/- 16%. The increments observed in group II and the significances of the differences with respect to group I were: AH(CT) = 11% +/- 14% (P < 0.01), AH(IAS) = 19% +/- 32% (NS), WCL(CT) = 42% +/- 14% (P < 0.05), WCL(IAS) = 42% +/- 16% (P < 0.01), FRP-AVN(CT) = 28% +/- 28% (NS), FRP-AVN(LAS) = 21% +/- 19% (NS), retrograde WCL = 35% +/- 24% (NS), and retrograde FRP = 16% +/- 13% (NS). In both groups, the AH interval variations were not correlated with those of the rest of the parameters analyzed. Truncated nodal function curves suggestive of a dual AV nodal pathway were obtained in three experiments, though in only one of them was this observed under basal conditions. In the other two experiments, with dual AV nodal physiology only after RF (one from each group), AV nodal reentrant tachycardias were triggered with atrial extrastimulus at coupling intervals equal to or shorter than at those that cause a sudden lengthening of the AH interval, RF delivered in the anterior and posterior zones of the Koch triangle produced effects of different magnitude on the AH interval and Wenckebach cycle length. In the anterior zone the AH interval was prolonged to a greater extent, while in the posterior zone the effects were greater on the Wenckebach cycle length. No correlation existed between the variations in AH interval and Wenckebach cycle length, regardless of where RF was delivered. The evaluation of anterograde AV nodal refractoriness was similar when stimulating from the crista terminalis or from the interatrial septum. By delivering RF, it was possible to induce dual AV nodal physiology and reentrant tachycardias.

Accessory atrioventricular pathways with only antegrade conduction in patients with symptomatic Wolff-Parkinson-White syndrome. Clinical features, electrophysiological characteristics and response to radiofrequency catheter ablation.

Information about accessory pathways conducting only in the antegrade direction is limited. The purposes of the present study were to prospectively investigate the clinical features, electrophysiological characteristics, effects of radiofrequency catheter ablation and recurrent atrial fibrillation after successful ablation in patients with accessory pathways conducting only in the antegrade direction, and to compare them with those who had pathways capable of bidirectional conduction in a consecutive series of 759 patients. Electrophysiological studies and radiofrequency catheter ablation were performed in 33 study patients with antegrade-only accessory pathways and in 377 patients with bidirectional accessory pathways for comparison. The patients with accessory pathways conducting only in the antegrade direction were older (47 +/- 16 vs 40 +/- 16 years, P = 0.037) and had a higher incidence of atrial fibrillation (100% vs 27.1%, P < 0.001) as well as related syncope (33.3% vs 10.1%, P = 0.001). The study patients also had more accessory pathways located in the posterior septum and a higher incidence of retrograde atrioventricular nodal conduction. The biophysical variables, success and complication rates of radiofrequency ablation were similar in both groups. During the follow-up period of 32 +/- 12 months, symptomatic atrial fibrillation after successful ablation did not recur in 79% and 81% of patients with unidirectional and bidirectional accessory pathways, respectively. Furthermore, old age and cardiovascular diseases were independent predictors of recurrent atrial fibrillation after radiofrequency ablation. In conclusion, this study showed that atrial fibrillation with preexcitation was the usual presentation in patients who had symptomatic Wolff-Parkinson White syndrome with an antegrade-only accessory pathway, and might be related to antegrade conduction of the accessory pathway. Therefore elimination of antegrade-only and bidirectional pathways by radiofrequency ablation could prevent the recurrence of symptomatic atrial fibrillation in younger patients without cardiac disease.

Electrophysiologic significance of discrete slow potentials in dual atrioventricular node physiology: Implications for selective radiofrequency ablation of slow pathway conduction

Atrioventricular (AV) node reentrant tachycardia is now routinely cured by selective radiofrequency ablation of slow AV node pathway conduction. However, debate remains concerning the optimum method for localizing the site at which radiofrequency energy should be delivered to eliminate slow-pathway conduction. Some investigators have proposed simple anatomy-guided ablations posteriorly near the ostium of the coronary sinus, whereas others suggest an electrophysiology-guided ablation using either recorded “slow potentials” or mapping of the retrograde atrial exit site of slow AV node pathway conduction when possible. To examine these issues, we systematically studied slow potentials recorded in the AV junction of patients undergoing radiofrequency catheter ablation for medically refractory AV node reentrant tachycardia. In 67 patients with the slow-fast form of AV node reentrant tachycardia, we performed detailed atrial mapping along the tricuspid annulus within the triangle of Koch. Two types of slow potentials were identified. Low-amplitude, low-frequency potentials, found in 48% of patients, were localized to the mid to posterior portions of the triangle of Koch, whereas high-amplitude, high-frequency potentials, observed in 22% of patients, were located only posteriorly near the ostium of the coronary sinus. In response to a bolus infusion of adenosine or incremental atrial pacing-induced AV node Wenckebach periodicity, the low-amplitude, low-frequency potentials showed an increased duration and further reduction in amplitude and frequency and often totally disappeared. In contrast, in spite of these maneuvers, the high-amplitude and high-frequency potentials remained unchanged. Of the 25 (37%) of 67 patients in whom the earliest retrograde atrial activation during ventriculoatrial slow AV nodal pathway conduction could be recorded, no patient exhibited low-amplitude, low-frequency potentials, and only 7 (28%) of 25 of these patients showed high-amplitude, high-frequency potentials. High-amplitude, high-frequency potentials persisted after successful radiofrequency ablation of slow pathway conduction. Fewer applications of radiofrequency energy were required for successful elimination of slow pathway conduction in patients in whom the retrograde atrial exit site of slow-pathway conduction could be localized, compared with those patients who only exhibited retrograde fast AV nodal pathway conduction. We conclude that high-amplitude, high-frequency potentials are part of atrial activity, whereas the origin of low-amplitude, low-frequency potentials is unclear and may represent either true intranodal biophysical electrical activity or merely artifact or far-field potentials. Regardless, the recording of high-amplitude or low-amplitude potentials is not required for successful ablation of slow-pathway conduction, although the ability to localize the retrograde atrial exit of slow-pathway conduction may assist in the ablation procedure.

Electrophysiologic characteristics and radiofrequency catheter ablation in patients with multiple atrioventricular nodal reentry tachycardias

Information about the mechanism and radiofrequency catheter ablation of multiple atrioventricular (AV) nodal reentry tachycardias is limited. Among the 550 consecutive patients with AV nodal reentry tachycardia, 36 with multiple forms of, AV nodal reentry tachycardia were included in this study. Electrophysiologic characteristics, as well as the efficacy and safety of radiofrequency ablation, were evaluated. Results showed that anterograde dual pathways were seen in 32 patients and triple pathways in 2, and retrograde dual pathways were seen in 23 patients and triple pathways in 11. Twenty-two patients had 2 types, 7 had 3 types, 5 had 4 types, and 2 had 5 types of AV nodal reentry tachycardia and echoes. After delivering radiofrequency energy to the target sites, 32 patients had no induction of AV nodal reentry tachycardia and only 4 had induction of 1 echo. Furthermore, 22 patients (61%) had simultaneous elimination or modification of the slow and/or intermediate pathways in the anterograde and retrograde direction. During the follow-up period of 19 ±14 months, 2 patients had recurrence of tachycardia. Thus, multiple anterograde and retrograde AV nodal pathways were present in the human AV node and they constituted the substrates of reentry circuits. Radiofrequency catheter ablation was safe and effective in eliminating the slow and intermediate pathways for maintenance of multiple AV nodal reentry tachycardias.