A unipolar coronary sinus mapping study of patients with left-sided atrioventricular accessory pathways

So-called unipolar 'PQS pattern' is widely accepted as a hallmark of successful catheter ablation of the left-sided atrioventricular accessory pathway. However, the unipolar nature of the electrogram and the site-dependent appearance of this characteristic pattern are poorly understood. Therefore, unipolar coronary sinus (CS) mapping was performed using a multipolar fine electrode in patients with Wolff-Parkinson-White (WPW) syndrome associated with an antegrade left-sided accessory pathway (case group) and those with a concealed left-sided accessory pathway or atrioventricular nodal reentrant tachycardia (control group) under sinus rhythm and fixed high right atrial, CS ostial, and distal pacing. In both groups, the unipolar CS atrial electrogram showed intrinsic negative deflection (initial positive followed by negative parts) with considerable variation depending on the recording site. This unipolar configuration of the atrial electrogram was not influenced by different activation sequences during pacing at various sites. The case group exhibited a unipolar 'PQS pattern' at successful ablation sites for the left lateral to anterolateral accessory pathway. However, this was not true for the left posteroseptal accessory pathway, possibly because the negative part of the atrial electrogram distorted the 'PQS pattern' as an intervening dip. In conclusion, the site-dependent variations of the unipolar CS atrial electrogram underlie the limited usefulness of the 'PQS pattern' in left posteroseptal accessory pathway localization.     

局部单极电图在房室结折返性心动过速射频消融术中的应用

目的探讨在特殊情况下,单极电图能否代替双极电图运用于房室结折返性心动过速射频消融术中弥补体表心电图中的不足。方法将冠状窦、希氏束及大头消融电极与胸导联相连,记录局部单极电图,运用于５例病人,观察心动过速、射频消融过程中心房波、心室波的关系,并与２０例房室结折返性心动过速病人双极记录的特征相比较。结果（１）心动过速均显示出逆Ａ呈向心性分布的特征（１００％ｖｓ１００％,Ｐ＞０．０５）;（２）消融过程中单极电图可清楚显示交界心律时的传导情况（１００％ｖｓ１００％,Ｐ＞０．０５）。结论在特殊情况下,使用局部单极电图可代替双极记录,弥补体表心电图在诊断房室结双径路以及射频消融术中的不足,避免完全性房室传导阻滞的发生。     

Randomized comparison of anatomic and electrogram mapping approaches to ablation of the slow pathway of atrioventricular node reentrant tachycardia

Objectives. The purpose of this study was to prospectively compare in random fashion an anatomic and an electrogram mapping approach for ablation of the slow pathway of atrioventricular (AV) node reentrant tachycardia.Background. Ablation of the slow pathway in patients with AV node reentrant tachycardia can be performed by using either an anatomic or an electrogram mapping approach to identify target sites for ablation. These two approaches have never been compared prospectively.Methods. Fifty consecutive patients with typical AV node reentrant tachycardia were randomly assigned to undergo either an anatomic or an electrogram mapping approach for ablation of the slow AV node pathway. In 25 patients randomly assigned to the anatomic approach, sequential radiofrequency energy applications were delivered along the tricuspid annulus from the level of the coronary sinus ostium to the His bundle position. In 25 patients assigned to the electrogram mapping approach, target sites along the posteromedial tricuspid annulus near the coronary sinus ostium were sought where there was a multicomponent atrial electrogram or evidence of a possible slow pathway potential. If the initial approach was ineffective after 12 radiofrequency energy applications, the alternative approach was then used.Results. The anatomic approach was effective in 21 (84%) of 25 patients, and the electrogram mapping approach was effective in all 25 patients (100%) randomly assigned to this technique (p = 0.1). The four patients with an ineffective anatomic approach had a successful outcome with the electrogram mapping approach. On the basis of intention to treat analysis, there were no significant differences between the electrogram mapping approach and the anatomic approach with respect to the time required for ablation (28 ± 21 and 31 ± 31 min, respectively, mean ± SD, p = 0.7) duration of fluoroscopic exposure (27 ± 20 and 27 ±18 min, respectively, p = 0.9) or mean number of radiofrequency applications delivered (6.3 ± 3.9 vs. 7.2 ± 8.0, p s 0.6). With both the anatomic and electrogram mapping approaches, the atrial electrogram duration and number of peaks in the atrial electrogram were significantly greater at successful target sites than at unsuccessful target sites.Conclusions. The anatomic and electrogram mapping approaches for ablation of the slow AV nodal pathway are comparable in efficacy and duration. If the anatomic approach is initially attempted and fails, the electrogram mapping approach may be successful at sites outside the areas targeted in the anatomic approach. With both the anatomic and electrogram mapping approaches, there are significant differences in the atrial electrogram configuration between successful and unsuccessful target sites.     

Dependence of electrogram duration in right posteroseptal atrium and atrium-pulmonary vein junction on pacing site: mechanism and implications regarding atrioventricular nodal reentrant tachycardia and paroxysmal atrial fibrillation

INTRODUCTION: The fractionated atrial electrogram, a signal helpful in identifying the target site for radiofrequency catheter ablation of the slow AV nodal pathway, is considered to arise from nonuniform anisotropic electrical activity. However, the effects of pacing sites and radiofrequency ablation on these electrograms are not clear. Similarly, the nature of the fractionated atrial electrogram in the atrium-pulmonary vein junction has yet to be determined. METHODS AND RESULTS: Two experiments were performed in this study. Experiment 1 evaluated the fractionated atrial electrogram at target sites before and after slow AV nodal pathway ablation during sinus rhythm or during pacing from different sites. Group 1A consisted of 16 patients with dual AV nodal pathway physiology and AV nodal reentrant tachycardia who underwent successful ablation without residual slow AV nodal pathway. Group 1B consisted of 7 patients who underwent successful elimination of AV nodal reentry but with residual dual AV nodal pathway physiology. Group 1C consisted of 6 patients who still had AV nodal reentrant tachycardia after two applications of radiofrequency energy. In group 1D, there were 16 patients with dual AV nodal pathway physiology, but without inducible AV nodal reentrant tachycardia. In group 1E, there were 15 patients without dual AV nodal pathway physiology. Experiment 2 investigated the fractionated atrial electrogram in the ostium of the left and right superior pulmonary veins in 18 patients with paroxysmal atrial fibrillation (2A) and in 8 patients without paroxysmal atrial fibrillation (2B). Before radiofrequency ablation, electrogram duration in the right posteroseptal atrium during pacing from the middle coronary sinus or the right posterolateral atrium was shorter than that during pacing from the high right atrium (HRA) in all group 1 patients. After the successful elimination of the slow AV nodal pathway conduction in group 1A, atrial electrogram duration during HRA pacing was shorter than that before ablation. In experiment 2 patients, electrogram duration during pacing from the proximal or distal coronary sinus was shorter than that during pacing from HRA or sinus rhythm. CONCLUSION: These findings suggest that the fractionated atrial electrograms in the right posteroseptal atrium and ostium of left or right superior pulmonary veins are potentially consistent with nonuniform anisotropic propagation. Alternations of electrogram characteristics after successful radiofrequency ablation of the slow AV nodal pathway may arise from the changes of nonuniform anisotropic activity in the right posteroseptal atrium.     

Catheter ablation for cardiac arrhythmias

With the introduction of radiofrequency energy, catheter ablation has become an established technique for managing many cardiac rhythm disturbances. High efficacy and safety have been reported for accessory pathway ablation, selective fast and slow atrioventricular nodal pathway ablation to eliminate atrioventricular nodal reentrant tachycardia (while preserving atrioventricular conduction), atrioventricular junctional ablation to control the ventricular response to atrial tachyarrhythmias, ablation of the right bundle branch to eliminate bundle branch reentrant ventricular tachycardia, and ablation of the site of tachycardia origin in patients with ventricular tachycardia unassociated with structural heart disease. In addition, there has been active investigation into ablation techniques for more complex arrhythmias such as atrial tachycardia, atrial flutter, and ventricular tachycardia associated with structural heart disease.     

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.     

隐匿性拖带时起搏后间期与慢径消融成功靶点的关系

评价应用隐匿性拖带方法对准确靶点消融的有效性及探讨常规慢径靶点部位与房室结折返性心动过速(AVNRT)折返环的关系。可反复诱发的持续性典型AVNRT的患者 34例 ,消融导管在后或中间隔标测到A/V≤ 0 .5处 ,然后诱发心动过速 ,在高位右房 (HRA)和冠状窦口 (CSO)超速起搏产生隐匿性拖带 ,并按常规方法进行慢径消融。比较隐匿性拖带时靶点部位起搏后间期与心动过速周长的差值 (PPI-TCL值 )在成功靶点与不成功靶点区别。结果 :HRA超速起搏发生隐匿性拖带时 ,His束记录部位A波均为逆向夺获。而CSO超速起搏拖带时 ,32例His束记录部位A波为顺向夺获 ,另 2例为逆向夺获。在这 32例中共记录 5 4个靶点 ,成功靶点的PPI-TCL值明显小于不成功靶点 (12 .4± 5 .8msvs 32 .1± 18.6ms,P <0 .0 1)。PPI-TCL值≤ 2 0ms对靶点成功消融的敏感性和特异性分别为 84%、81%。结论 :本研究提示常规慢径消融成功部位作为房室结外的后部延伸组织参与组成AVNRT折返环或距其非常近。在可持续发作和诱发的AVNRT患者中 ,CSO部位起搏拖带顺向心房夺获时 ,靶点部位测出的PPI-TCL值≤ 2 0ms,可作为一种新的慢径路电生理定位消融方法     

Perinodal slow potential as a local guide for transcatheter radiofrequency ablation of atrioventricular nodal reentrant tachycardia: therapeutic efficacy and electrophysiological mechanisms of success.

BACKGROUND--A specific local indicator in the Koch's triangle could be critical to the complication-free treatment of atrioventricular nodal reentrant tachycardia by transcatheter radiofrequency ablation. Recording of perinodal slow potential reflects a slow conduction area, and probably indicates the location of the slow pathway component of the circuit. Specific ablation of the slow pathway would carry the least risk of atrioventricular block. METHOD AND RESULTS--Guided by the mapped perinodal slow potential, atrioventricular nodal reentrant tachycardia was successfully eliminated in all of 55 consecutive patients in one session. Fifty two patients (94.5%) had confirmed slow potential at the final success sites. Despite the good result, the underlying electrophysiological mechanisms of early success from slow-potential-guiding catheter ablation were heterogeneous: selective slow pathway eradication in 31 patients (56.4%, group A), selective slow pathway modification in 18 patients (32.7%, group B), inadvertent fast pathway damage in six patients (10.9%, group C). Group B patients had the preservation of dual atrioventricular nodal pathways, adequate atrio-Hisian delay, fast pathway facilitation, and a higher frequency of inducible, single non-conducted nodal echo (15/18, 83.3% v 6/31, 19.4% in group A, P << 0.001). The upper communicating path of the circuit was implicated as another site of radiofrequency destruction. Three recurrences were documented in follow up study. However, reablation by the same approach caused complete atrioventricular block in one patient (1.7%, 1/58 procedures). None of the local characteristics of ablation sites was an independent predictor of procedure outcome. CONCLUSIONS--Perinodal slow potential is not a specific slow pathway indicator in transcatheter radiofrequency ablation of atrioventricular nodal reentrant tachycardia. Multiple strategic sites of the reentry circuit may be damaged through similar local signals.     

选择性改良房室结慢径中预示三度房室传导阻滞的新指标

目的探讨选择性改良房室结慢径放电过程中预示三度房室传导阻滞（AVB）的新指标。方法回顾性分析2010年1月至l2月期间在广东省心血管病研究所完成的房室结折返性心动过速（AVNRT）经导管射频消融（RFCA）治疗的患者资料,统计放电过程中出现一过性三度房室传导阻滞的发生率,分析放电过程中出现一过性三度房室传导阻滞前的心电现象。结果经心内电生理检查诊断为房室结折返性心动过速的患者412例,慢快型347例,84.2%;快慢型45例,10.9%;慢慢型20例,4.9%。均采用选择性改良房室结慢径治疗,成功率100%。复发2例,复发率0.5%,均在第二次消融成功。永久性房室结折返性心动过速罹患率为0。一过性房室结折返性心动过速为7例,罹患率1.7%。出现早发交界心律31例,罹患率为7.5%。总共放电1406次,出现早发交界心律的放电67次,发生率4.8%。在出现早发交界心律的放电过程中,即刻停止放电组一过性房室结折返性心动过速发生率是2.3%;延迟停止放电组一过性房室结折返性心动过速发生率是25.0%;两组发生率比较,差异有统计学意义（P=0.013）。结论早发交界心律也是预示三度AVB的指标之一,出现早发交界心律即刻停止放电是避免房室结折返性心动过速的有效方法。     

Case Report: Clinical AV Nodal Reentrant Tachycardia in a Patient with Left Sided Accessory Pathway and Immediate Occurrence of Antidromic AV Reentrant Tachycardia after Slow Pathway Ablation

The only inducible arrhythmia in a patient with exclusive antegrade conducting left anterolateral accessory pathway, consists of slow/fast atrioventricular nodal reentrant tachycardia. After radiofrequency catheter ablation of the slow pathway, true antidromic AV reentrant tachycardia was easily induced by atrial pacing. Following ablation of the accessory pathway no arrhythmia could be induced.     

Atrioventricular nodal reentry tachycardia in children: curative treatment by high frequency catheter ablation

BACKGROUND: Atrioventricular nodal reentrant tachycardia (AVNRT) is one of the most common forms of supraventricular tachycardia in the pediatric population. PATIENTS AND METHODS: 41 children with a mean age of 9.6 (3.7-16) years with recurrent atrioventricular nodal reentrant tachycardia (AVNRT) refractory to medical treatment (n = 38) and recurrent syncope (n = 3) underwent electrophysiologic (EP) study. In all patients dual AV-nodal physiology could be demonstrated during EP study and typical form of AVNRT (mean heart rate 220/min) could be induced by programmed atrial stimulation. A steerable 7 F ablation catheter was placed at the inferoparaseptal region of the tricuspid valve annulus close to the orifice of the coronary sinus with the intention to record a late fractionated local atrial electrogram during sinus rhythm. Starting at this point radiofrequency current (500 kHz) with a target temperature of 70 degrees C was delivered with the intention to ablate the slow pathway. If a slowly accelerated junctional rhythm (< 120/min) occurred during energy discharge, programmed atrial stimulation was repeated. Otherwise radiofrequency current was delivered step by step up to a septal position next to the tricuspid valve annulus. Slow pathway ablation was defined as lack of evidence of dual AV nodal pathways during repeated atrial stimulation. Slow pathway modulation was defined as maximal one atrial echoimpulse after ablation. RESULTS: The number of energy applications ranged from 1-19 (median 6). In 35/41 patients slow pathway ablation could be achieved; in six patients the slow pathway was modulated. In none of the patients permanent high grade AV block was observed. During follow-up (mean 4.1 years) two patients had a recurrent episode of AVNRT after slow pathway modulation. All other patients are still free of AVNRT without medical treatment. CONCLUSION: Selective radiofrequency current ablation/modulation of the slow pathway is a safe and curative treatment of AVNRT in young patients.     

Does radiofrequency ablation increase creatine kinase and troponin-T?

Radiofrequency ablation produces a focal area of myocardial necrosis. Creatine kinase (total & MB fraction) and troponin-T were analysed in 54 patients who underwent electrophysiological study and radiofrequency ablation for atrioventricular nodal reentrant tachycardia, atrioventricular reentrant tachycardia and idiopathic ventricular tachycardia. The age of the patients was 36 +/- 12 years; 17 patients underwent slow pathway modification for atrioventricular nodal reentrant tachycardia, 26 patients underwent accessory pathway ablation and 11 patients underwent ablation for idiopathic ventricular tachycardia. There was no significant rise in creatine kinase, creatine kinase total & MB fraction and troponin-T in the patients who underwent slow pathway ablation for atrioventricular nodal reentrant tachycardia. In patients with atrioventricular reentrant tachycardia, there was no significant rise in creatine kinase and creatine kinase total & MB fraction levels, while troponin-T levels rose from 0.13 +/- 0.06 to 0.29 +/- 0.16 eta g/ml (p < 0.05). There was an increase in creatine kinase, creatine kinase total & MB fraction and troponin-T levels after idiopathic ventricular tachycardia ablation from 68.4 +/- 44.9 to 138.0 +/- 81.7 IU (p < 0.05), 2.77 +/- 3.34 to 25.2 +/- 19.8 IU (p < 0.05) and 0.09 +/- 0.04 to 0.34 +/- 0.08 eta g/ml (p < 0.001) respectively. Radiofrequency ablation of atrioventricular nodal reentrant tachycardia does not cause any significant myocardial damage to raise any cardiac enzymes. Ablation of atrioventricular reentrant tachycardia results in only minor injury causing rise in only troponin-T levels. However, ventricular tachycardia ablation results in significant myocardial injury raising all the cardiac enzymes.     

Radiofrequency catheter ablation of both atrial ventricular nodal reentrant and atrial ventricular reentrant tachycardia in a single session

Radiofrequency catheter ablation is a new therapeutic approach to treat patients with symptomatic drug-resistant paroxysmal supraventricular tachycardia. Ablation of two accessory atrioventricular pathways in a single session has been frequently described previously. However, ablation in a single session of both the fast pathway, involved in atrial ventricular nodal reentrant tachycardia, and a concealed atrioventricular accessory pathway involved in a circus movement tachycardia has rarely been reported. A 57-year-old man with a grade III aortic incompetence had the infrequent association of atrial ventricular nodal reentrant tachycardia and orthodromic circus movement tachycardia due to a concealed accessory pathway. He presented with drug-resistant reentrant supraventricular tachycardia and, in a single session, underwent a successful radiofrequency catheter ablation of the fast atrial ventricular nodal pathway and a concealed posteroseptal accessory pathway. During a 10-month follow-up he was free of palpitations without any antiarrhythmic therapy and underwent elective aortic valve replacement.     

应用磁导航技术遥控标测和消融治疗快速性心律失常

目的在数种快速性心律失常中,观察应用磁导航技术行遥控标测和消融治疗的可行性与安全性。方法对复杂程度不同的心律失常患者,采用NiobeII磁导航系统(Stereotaxis,Inc)遥控操作,用HeliosII磁性标测和消融导管行射频温控消融治疗。结果12例入选,男8例,女4例,年龄36.83±13.05岁。4例有晕厥,1例有心脏骤停,5例有器质性心脏病。房室结折返性心动过速3例,左前游离壁房室旁道3例,右游离壁房室旁道1例,左后间隔房室旁道伴心房颤动1例,左中间隔房室旁道伴房室结折返性心动过速1例,心房扑动1例,房性早搏/心房颤动1例,室性早搏/心室颤动1例。采用遥控操作,12例均完成电生理检查,11例可准确到达靶点部位,行射频消融,10例成功。操作时间149.17±68.95min,未见并发症。结论对复杂程度不同的心律失常,不管患者有无器质性心脏病,采用磁导航技术均可安全与可靠地实施遥控标测和消融治疗。     

Tachycardia-induced tachycardia: definitive treatment with radiofrequency ablation. Presentation of three cases]

Tachycardia-induced tachycardia is the phenomenon in which one tachycardia degenerates into another. Few data are available in patients suffering from AV nodal reentrant tachycardia an atrial fibrillation. For related to AV nodal reentrant triggered by tachycardia; there is a possible effective treatment by eliminating the slow nodal pathway, with radiofrequency ablation, as shown by other authors. In this study we present data on three patients with repeated episodes of documented atrial fibrillation and at least one episode of AV nodal reentrant tachycardia or regular palpitations. Radiofrequency ablation of the slow AV nodal pathway was successfully performed in both, and at a follow up of 6, 9 and 10 months, respectively, no new episode of AV nodal reentrant tachycardia or atrial fibrillation was documented.     

Pseudo-Pacemaker Syndrome Following Inadvertent Fast Pathway Ablation for Atrioventricular Nodal Reentrant Tachycardia

Pseudo-Pacemaker Syndrome After AV Nodal Ablation. Atrioventricular nodal reentrant tachycardia that is refractory to drug treatment has recently been treated with radiofrequency catheter ablation. In this case report we describe a patient with atrioventricular nodal reentrant tachycardia in whom radiofrequency ablation of slow pathway was attempted, with inadvertent damage to the fast pathway. The patient developed marked first-degree atrioventricular block associated with symptoms mimicking pacemaker syndrome.     

快-慢型房室结折返性心动过速的电生理特征和射频消融治疗

报道８例快－慢型房室结折返性心动过速（ＡＶＮＲＴ）的电生理特征及射频消融治疗。其中３例为慢－快型ＡＶＮ－ＲＴ射频消融改良慢径后出现的快－慢型ＡＶＮＲＴ。８例均经消融慢径而成功终止心动过速。平均放电次数３±１．１次、平均放电时间１２０±３０．４ｓ、平均放电功率３０±１１Ｗ。随访６～２４个月，无复发。快－慢型ＡＶＮＲＴ具有以下临床电生理特征：①快径不应期短、慢径不应期长。②心内电刺激无房室结双径路现象。③心动过速能由心房刺激诱发。④心动过速时ＡＨ间期＜ＨＡ间期，冠状窦近端Ａ波最提前。熟悉快－慢型ＡＶＮＲＴ的电生理特征，对于鉴别房性心动过速及右后间隔旁道参与的房室折返性心动过速十分重要，也是指导快－慢型ＡＶＮＲＴ射频消融成功的关键。     

Dissimilar atrial rhythms: coexistence of reentrant atrial tachycardia, atrioventricular nodal reentrant tachycardia and interatrial conduction block

We report a patient in whom mapping of the right atrium with multipolar catheters and electroanatomic mapping revealed the presence of three dissimilar rhythms: a reentrant atrial tachycardia in the antero-lateral wall of the right atrium and an atrioventricular nodal reentrant tachycardia (AVNRT) isolated from each other and a conduction disturbance at the interatrial septum resulting in a rate-related interatrial block and a slow left atrial rhythm. The AVNRT was stopped with intravenous adenosine (6mg) and induced repeatedly by atrial extrastimuli associated with a critical atrioventricular delay and dual atrioventricular nodal pathways. Electroanatomic mapping disclosed extensive fibrosis isolating viable myocardium of the antero-lateral wall from the rest of the right atrium. The viable myocardium in the antero-lateral wall was activated by a reentrant rhythm circulating around an islet of fibrosis located in the middle of the viable tissue. The AVNRT was ablated by a standard approach and the reentrant atrial tachycardia by producing a linear lesion bridging the central islet of fibrosis with the anterior tricuspid annulus. This case highlights the complicated nature of some dissimilar atrial rhythms and the power of electroanatomic mapping tools to reveal the exact mechanism and guide radiofrequency ablation.     

The atrioventricular nodal reentrant tachycardia circuit: a proposal.

Several models of the atrioventricular nodal reentrant tachycardia circuit have been proposed. Recently, there has been experimental and clinical electrophysiology evidence that the right and left inferior extensions of the human atriventricular node and the atrionodal inputs they facilitate may provide the anatomic substrate of the slow pathway. Inferior nodal extensions appear to constitute a necessary limb of the tachycardia circuit in all forms of atrioventricular nodal reentrant tachycardia and represent the ablation target for all forms of this arrhythmia. Anatomic variations of multiple atrionodal inputs via atrial transitional cells may create the conditions for tachycardia inducibility and differing patterns of retrograde atrial activation. In the present article, we summarize the available evidence and propose a comprehensive model of the tachycardia circuit for all forms of atrioventricular nodal reentrant tachycardia based on the concept of atrionodal inputs.     

Dissimilar atrial rhythms: coexistence of reentrant atrial tachycardia, atrioventricular nodal reentrant tachycardia and interatrial conduction block

We report a patient in whom mapping of the right atrium with multipolar catheters and electroanatomic mapping revealed the presence of three dissimilar rhythms: a reentrant atrial tachycardia in the antero-lateral wall of the right atrium and an atrioventricular nodal reentrant tachycardia (AVNRT) isolated from each other and a conduction disturbance at the interatrial septum resulting in a rate-related interatrial block and a slow left atrial rhythm. The AVNRT was stopped with intravenous adenosine (6 mg) and induced repeatedly by atrial extrastimuli associated with a critical atrioventricular delay and dual atrioventricular nodal pathways. Electroanatomic mapping disclosed extensive fibrosis isolating viable myocardium of the antero-lateral wall from the rest of the right atrium. The viable myocardium in the antero-lateral wall was activated by a reentrant rhythm circulating around an islet of fibrosis located in the middle of the viable tissue. The AVNRT was ablated by a standard approach and the reentrant atrial tachycardia by producing a linear lesion bridging the central islet of fibrosis with the anterior tricuspid annulus. This case highlights the complicated nature of some dissimilar atrial rhythms and the power of electroanatomic mapping tools to reveal the exact mechanism and guide radiofrequency ablation.