低右房电图极性改变评价典型心房扑动射频消融结果

目的　在典型心房扑动 (房扑 )射频消融中观察临近峡部的低位右房心内电图极性改变 ,来迅速判断是否形成峡部双向阻滞。方法　对 10例典型房扑患者 ,沿三尖瓣环放置Halo电极 ,Halo远端紧邻峡部消融线 ,房扑发作中消融在房扑终止后行冠状窦起搏 ,窦性心律下消融则同时行冠状窦电极起搏 ,观察紧邻消融线低右房侧的心房电极电图起始部分的主波方向 (H电位 )的极性表现 ,并与最终双向阻滞评价结果比较。结果　 8例在窦性心律下行冠状窦电极起搏时消融 ,2例在房扑发作中消融。 10例患者最终消融结果均为双向阻滞。 2例房扑发作时H电位极性均为负向 ,8例窦性心律下H电位极性均为正向 ,峡部缓慢传导时该极性仍为正向 ,形成双向阻滞后H电位极性变为负向。结论　典型心房扑动行峡部线性消融时 ,行冠状窦起搏观察到紧邻峡部消融线低右房侧H电位的极性改变可能是峡部消融成功的新指标。该指标简单、快速、可靠性高。     

欧氏瓣对老年人Ⅰ型心房扑动射频消融的影响

目的探讨欧氏瓣对Ⅰ型心房扑动(简称房扑)导管射频消融即刻效果的影响。方法28例老年Ⅰ型房扑患者(呈逆钟向折返18例,顺钟向折返10例)在透视解剖标志和Halo电极三尖瓣环标测电图指引下,在房扑发作或冠状窦口起搏时以温控方式消融位于三尖瓣口和下腔静脉口之间的后峡部,消融方向从三尖瓣叶右室侧到下腔静脉开口。预设温度70℃,每点消融30s,每次移动消融电极3～5mm。观察下列指标:①房扑终止和后峡部阻滞时消融电极在消融线上所处的位置;②房扑终止后峡部残存传导间隙在消融线上所处的位置;③房扑终止后继续消融致后峡部完全阻滞的最终消融部位。结果根据右前斜位30°透视影像测得后峡部平均弧长(即消融线)为38.6±9.7mm。28例全部达到后峡部完全阻滞的消融终点,无并发症。与欧氏瓣有关的房扑终止率为100%(17/17),与欧氏瓣有关的后峡部完全阻滞发生率为92.9%(26/28)。结论欧氏瓣是Ⅰ型房扑后峡部消融线终点的重要标志,线性消融时欧氏瓣心室侧易残存传导间隙,消融该部位的残存传导间隙是Ⅰ型房扑后峡部消融的重要环节。     

典型心房扑动下腔静脉-三尖瓣环峡部电传导特性

目的比较典型心房扑动(房扑)与无房扑患者，下腔静脉-三尖瓣(TV—IVC)峡部的电传导特性。方法 12例同期来本院作射频消融的患者，A组6倒为频繁发作的典型房扑，B组6例为无房扑史的室上性心动过速(室上速)。观寨右房下侧壁(H1-2)和冠状窦口(CS9-10)以周期为600，500，400，300ms起搏时以及房扑和室上速时，TV—IVC峡部传导时间变化。基本刺激周期500ms时，分别测定峡部内、外侧局部心房不应期。结果 ①H1-2起搏时，A组蛱部传导时间较B组平均延长20.3%±11.6%(3.9％～28．9%，但P＞0．05)。CS9-10起搏时，A组峡部传导时间较B组传导时间平均延长27.1％±10.5%（12．5％～35.8％．但P>0．05)。②房扑时峡部传导时间133±6．6ms。室上速峡部传导时间61．1±12．7ms．两组(P<0．05)。③A、B组峡部局部心房有效不应期(ERP)差异无显著性。结论下腔静脉-三尖瓣峡部是折返环的一部分。但窦性心律时蛱部无显著传导延迟。房扑功能慢传导区不一定局限于该部位。     

Halo电极远端电位方向逆转作为典型心房扑动消融终点标准的观察

目的探讨一种通过Halo电极远端电位方向发生逆转来判断典型心房扑动(简称房扑)三尖瓣环峡部线性消融成功的方法。方法 20例典型房扑患者接受射频消融治疗,将Halo电极经右股静脉置于三尖瓣环上,从远端电极至近段电极呈顺时针方向。于窦性心律下,行三尖瓣环至下腔静脉之间线性消融,与此同时,于冠状窦口行S1S1500ms起搏。消融过程中,Halo电极标测显示远端电极及近端电极呈双向传导。以Halo电极远端电位方向逆转作为消融成功终点。结果 20例均消融成功,无消融并发症发生。消融后,反复电刺激未诱发房扑。术后随访6个月,未见房扑复发。结论冠状窦口起搏刺激下,Halo电极远端电位方向出现逆转可作为典型房扑三尖瓣环峡部线性消融成功的可靠指标。     

典型心房扑动消融术后峡部时间间期的变化预测双向阻滞的价值

通过比较心房扑动 (简称房扑 )成功消融前后右心房峡部时间间期 ,分析峡部时间间期的延长程度对峡部完全性双向阻滞的预测价值。选择 1996～ 2 0 0 2年在我院行射频消融治疗的典型房扑患者 30例 ,男 2 3例、女 7例 ,年龄 4 7.85± 9.35岁 ,采用解剖和影像定位法 ,在冠状静脉窦口持续起搏下消融峡部。结果 :2 9例消融成功 ,达到双向传导阻滞的标准 ,成功率 96 .6 7%。消融后起搏信号至右房下侧壁的时间间期 (SAH1 2 )和起搏信号至冠状窦口CS3 4的时间间期明显延长 (14 0 .4 7± 2 0 .4 8msvs73.82± 13.0 1ms ;138.17± 15 .5 5msvs77.6 3± 8.36ms ,P <0 .0 0 0 1)。 2 9例中有 17例在完全性传导阻滞前可以记录到不完全性传导阻滞 ,峡部不完全性传导阻滞时SAH1 2 比术前增加 4 5 .4 9%± 8.7%。消融前后右心房峡部传导时间间期增加≥ 5 0 % ,预测峡部完全性双向传导阻滞的灵敏度 10 0 % ,特异度 83.3%。结论 :右心房峡部传导时间间期的定量分析是判断峡部完全性双向传导阻滞的有价值的方法。     

非接触球囊导管标测系统指导心房扑动消融的初步经验

目的　评价非接触球囊导管标测系统在心房扑动 (房扑 )标测和射频消融中的临床应用。方法　 7例房扑患者 ,年龄 (6 0± 10 )岁 ,男 4例 ,女 3例。其中 1例为房间隔缺损修补术后 ,2例为采用常规方法消融典型房扑后复发患者。应用非接触球囊导管标测系统构建右房三维几何模型 ,标测心动过速的折返激动顺序和关键峡部 ,并利用其导航系统指导峡部的线性消融。消融后分别于峡部两侧起搏判断峡部阻滞情况。结果　 6例患者诱发出房扑 ,心动过速周长 (2 16± 2 2 )ms。6例房扑均为峡部依赖型 ,2例呈逆钟向传导 ,4例呈顺钟向传导 ;4例房扑呈双环折返激动 ;7例消融均成功 ,房扑不再诱发 ,峡部呈完全双向传导阻滞 ;手术时间 (30 0± 12 9)min ,X线曝光时间 (2 5 0± 6 5 )min ,放电次数 (2 5 7± 12 1)次。无手术并发症。随访 3～ 14个月无复发病例。结论　在房扑标测和消融中应用非接触球囊导管标测系统是安全有效的 ,不仅能确定折返环路 (特别是双环折返激动 )的顺序和关键峡部 ,而且能准确判断线性损伤的连续性 ,同时可减少X线曝光时间。     

典型心房扑动的CARTO系统标测和消融

评价非X线CARTO系统在指导导管射频消融典型心房扑动 (简称房扑 )中的临床应用。 5例典型房扑 ,均为男性 ,年龄 40 .4± 15 .7岁。除 1例为先天性三房心 (经外科矫正 )外 ,余均无器质性心脏病。心动过速周期 2 0 5± 2 8ms。位于三尖瓣环和下腔静脉口间的峡部为消融部位。运用CARTO系统实时标测右房三维结构 ,并指导导管标测和消融峡部。消融后分别在冠状静脉窦和低位后外侧右房以 5 0 0ms起搏重建三维电解剖图 ,判定完全双向传导阻滞。 5例均消融成功 ,房扑不再诱发及产生确定的峡部双向传导阻滞。放电次数为 12 .7± 6 .5。手术时间为 2 78± 49min ,曝光时间为 16± 7min。随访 1～ 3个月无病例复发。结论 :本研究表明在房扑标测和消融中应用CARTO系统是安全有效的。消融后峡部两侧分别起搏重建峡部三维电解剖图 ,可准确判断线性损伤的连续性 ,证实完全双向传导阻滞 ,有利减少复发率。同时可减少X线曝光时间。     

术中峡部传导间期百分比对典型心房扑动导管消融终点判定的有效性评估

目的 通过术中测量三尖瓣-下腔静脉峡部（CTI）依赖心房扑动（房扑）消融前后峡部传导间期百分比,探讨峡部传导间期百分比在CTI线性阻滞消融终点评估的临床价值。方法 本研究入组2021年2月至2023年2月诊断CTI依赖房扑并行射频消融治疗患者共37例（首都医科大学附属北京安贞医院35例,河北省儿童医院2例）,术中均诱发CTI依赖房扑,并采用解剖消融方法沿三尖瓣环至下腔静脉行线性消融,术后经右心房激动标测验证CTI呈线性阻滞。分别统计入组患者心动过速周长（TCL）、冠状窦起搏下消融前局部传导间期（P-ABL1）、冠状窦起搏下消融后局部传导间期（P-ABL2）,计算局部传导期间百分比（P-ABL2/TCL）。评估P-ABL2/TCL对诊断CTI双向传导阻滞的价值,并通过消融后激动顺序验证其有效性。结果 所有入组患者均采用解剖方法行射频消融,并行激动标测验证CTI呈线性阻滞。术中诱发TCL为（310.00±46.32）ms。术前测定P-ABL1为（92.16±27.65）ms,术后测量P-ABL2为（173.65±16.35）ms,两组数据差异有统计学意义（P <0.001）。术后P-...     

三尖瓣环传导时间在确定典型心房扑动消融终点中的价值

目的评价三尖瓣环的传导时间在确定心房扑动(房扑)消融终点中的价值。方法19例经体表心电图证实为典型房扑的患者,在心动过速中根据房扑激动顺序及拖带标测证明折返环沿三尖瓣环运行。测定房扑周长(tachycardial interval,TCL)及起搏后间期(post-pacing interval,PPI)。在三尖瓣环与下腔静脉之间的峡部消融,经冠状窦口及低位右心房起搏证明峡部双向阻滞。分别在冠状窦口、冠状窦远端及高位右心房刺激,用大头电极在峡部消融线上记录在3个部位起搏时的双电位间期(double potential interval,DPI),DPI=刺激信号至第二个电位间期(T2)-刺激信号至第一个电位间期(T1);三尖瓣环传导时间(tricuspid valve annulus conductiontime,TACT),TACT=(T1 T2)-(PPI-TCL);计算TACT/TCL。结果19例患者在消融术中均形成峡部双向阻滞,无并发症发生,停用任何抗心律失常药物,平均随访(27±8)个月,复发1例,经再消融后成功。TCL为210~385ms(平均267·21±36·64ms),冠状窦近端测得的PPI为235~390ms(平均291·32±42·88ms),冠状窦远端PPI为273~450ms(平均334·25±43·04ms),高位右心房的PPI为230~385ms(平均277·13±35·91ms)。提示高位右心房及冠状窦口接近折返环(与TCL相比,P>0·05),而冠状窦远端远离折返环(与TCL相比,P<0·05)。经冠状窦口及低位右心房起搏证实峡部双向阻滞后,分别于冠状窦口、冠状窦远端及高位右心房起搏测定DPI,分别为(152·56±56·66)ms,(150·08±48·35)ms及(85·6±34·47)ms。高位右心房起搏时DPI与冠状窦起搏时比较差异有统计学意义(P<0·05)。3个部位计算的TACT分别为(234·72±58·03)ms、(219·73±40·87)ms,(232·3±43·24)ms,差异无统计学意义。三个部位计算的TACT/TCL分别为(0·87±0·14),(0·82±0·12)及(0·91±0·15),差异无统计学意义。结论三尖瓣环传导时间不受起搏部位的影响,仅与环内折返运动时间长短有关。不论房扑周长的长短及双电位间期的大小,只要三尖瓣环传导时间与房扑周长之比接近于1,提示峡部完全阻滞。     

单导管标测在心房扑动射频消融中的意义

目的:探讨单导管标测法在心房扑动(房扑)射频消融中的应用方法和效果。方法:阵发性心房颤动并发房扑患者行肺静脉电隔离术时采用单导管标测法消融房扑30例。所有患者行肺静脉电隔离术后,将10极冠状静脉窦(CS)导管远端2对电极放置于CS内,余位于CS外,并使之有一定的张力,使导管贴靠于三尖瓣环和低右房。用冷盐水灌注消融导管线性消融三尖瓣峡部,房扑发作患者在房扑下消融,窦律患者在CS远端电极起搏下消融,可在术中随时把大头消融导管置于希氏束部位,用于评价是否已完全达双向阻滞,即:起搏CS远端电极,刺激信号至CS近端电极A波的距离大于至希氏束A波的距离,则CS口至低右房单向阻滞;CS近端电极起搏,刺激信号至CS远端电极A波的距离大于至希氏束A波的距离,则低右房至CS口单向阻滞,从而达双向阻滞,CS近端电极起搏所需电压较高,有的患者可达24mA。结果:所用阵发性心房颤动并发房扑患者均成功行三尖瓣峡部线性射频消融,达到双向阻滞,无手术相关并发症,随访4个月～2年,无房扑复发。结论:单导管标测法对房扑患者行三尖瓣峡部线性射频消融操作简单、快速,可完全用于评价消融结果,成功率高,并且节省手术费用。     

Right ventricular pacing to assess transisthmus conduction in patients undergoing isthmus-dependent atrial flutter ablation: a new useful technique?

BACKGROUND: Successful radiofrequency (RF) ablation of typical, isthmus-dependent atrial flutter requires establishment and confirmation of bidirectional conduction block across the cavotricuspid isthmus. Low atrial pacing usually is performed from the bipoles of the 20-pole Halo catheter, septal and lateral to the cavotricuspid isthmus ablation line. However, occasionally this is difficult because of high pacing thresholds and/or saturation of the atrial electrograms recorded near the pacing catheter. OBJECTIVES: The purpose of this study was to assess if right ventricular (RV) pacing and resulting retrograde atrial activation can be used to assess conduction block from the septum to the lateral wall in a clockwise direction. METHODS: Thirty-five consecutive male patients (mean age 64 +/- 10 years; mean ejection fraction 42 +/- 13%; mean left atrial dimension 44 +/- 6 mm) with typical isthmus-dependent atrial flutter were studied. The following electrophysiology catheters were used: 20-pole catheter along the tricuspid annulus, quadripolar catheters at the His and/or RV apex, and 8-mm ablation catheter. Following RF ablation of the cavotricuspid isthmus, bidirectional conduction block was confirmed in all 35 patients by pacing at a cycle length of 600 ms from bipoles septal and lateral to the cavotricuspid isthmus ablation line. Conduction times from pacing artifact to adjacent bipolar atrial electrograms and reversal of atrial activation pattern were analyzed. RV pacing was performed and retrograde atrial activation pattern assessed. If retrograde AV nodal conduction was absent, isoproterenol was infused intravenously at 2 microg/min, and RV pacing was repeated. The conduction time between the double potentials across the cavotricuspid isthmus ablation line was measured. RESULTS: Mean conduction times across the isthmus during septal (S), lateral (L), and RV pacing were 145 +/- 21 ms, 144 +/- 24 ms, and 129 +/- 20 ms, respectively. Retrograde AV nodal conduction was present in 34 of 35 patients (isoproterenol 8 patients). Evidence of conduction block by a clear change in activation pattern across the isthmus was seen during RV pacing in 33 of 35 patients with bidirectional conduction block. CONCLUSION: RV pacing is a simple and easy maneuver that can be performed to assess isthmus conduction in most patients.     

Incremental Pacing for the Diagnosis of Complete Cavotricuspid Isthmus Block During Radiofrequency Ablation of Atrial Flutter

Incremental Pacing for the Diagnosis of Cavotricuspid Isthmus Block.   Background: Complete conduction block of the cavotricuspid isthmus (CTI) reduces atrial flutter recurrences after ablation. Incremental rapid pacing may distinguish slow conduction from complete CTI conduction block.
Methods and Results: Fifty-two patients (67 ± 9 years) undergoing 55 CTI ablation procedures were included. With ablation, double potentials (DPs) separated by an isoelectric line of ≥30 ms were obtained. Incremental atrial pacing (600–250 ms) was performed from coronary sinus (CS) and low lateral right atrium (LLRA). A <20 ms increase in the DPs distance during incremental pacing was indexed as complete CTI block. In 8 patients, an initial <20 ms DPs distance increase was noted; direct complete isthmus block was suggested and no additional ablation performed. In the remaining, the CTI line was remapped for conduction gaps and additional radiofrequency energy pulses applied. Complete block, as indexed by incremental pacing, occurred in 46 of 55 procedures, with one flutter recurrence (follow-up 8 ± 2 months): DPs interval variation of 116 ± 20 to 123 ± 20 ms (CS), P = 0.21; and 122 ± 25 to 135 ± 35 ms (LLRA), P = 0.17. The remaining 9 patients (persistent rate-dependent DPs increase) presented 3 flutter recurrences, P = 0.01: DP distance from 127 ± 15 to 161 ± 18 ms (CS), P < 0.001; and 114 ± 24 to 142 ± 10 ms (LLRA), P = 0.007.
Conclusion: Incremental pacing distinguishes complete CTI block from persistent conduction. Such identification, accompanied by additional ablation to achieve block, should minimize flutter recurrences after ablative therapy. (J Cardiovasc Electrophysiol, Vol. 21, pp. 33–39, January 2010)     

Linear Ablation of Right Atrial Free Wall Flutter: Demonstration of Bidirectional Conduction Block as an Endpoint Associated With Long‐Term Success

Ablation of Right Atrial Free Wall Flutter. Introduction: Ablation for atypical atrial flutter (AFL) is often performed during tachycardia, with termination or noninducibility of AFL as the endpoint. Termination alone is, however, an inadequate endpoint for typical AFL ablation, where incomplete isthmus block leads to high recurrence rates. We assessed conduction block across a low lateral right atrial (RA) ablation line (LRA) from free wall scar to the inferior vena cava (IVC) or tricuspid annulus in 11 consecutive patients with atypical RA free wall flutter. Method and results: LRA block was assessed following termination of AFL, by pacing from the ablation catheter in the low lateral RA posterior to the ablation line and recording the sequence and timing of activation anterior to the line with a duodecapole catheter, and vice versa for bidirectional block. LRA block resulted in a high to low activation pattern on the halo and a mean conduction time of 201 ± 48 ms to distal halo. LRA conduction block was present in only 2 out of 6 patients after termination of AFL by ablation. Ablation was performed during sinus rhythm (SR) in 9 patients to achieve LRA conduction block. No recurrence of AFL was observed at long‐term follow‐up (22 ± 12 months); 3 patients developed AF. Conclusion: Termination of right free wall flutter is often associated with persistent LRA conduction and additional radiofrequency ablation (RFA) in SR is usually required. Low RA pacing may be used to assess LRA conduction block and offers a robust endpoint for atypical RA free wall flutter ablation, which results in a high long‐term cure rate. (J Cardiovasc Electrophysiol, Vol. 21, pp. 526‐531, May 2010)     

Validation of Coronary Sinus Activation Pattern During Left Atrial Appendage Pacing for Beat‐to‐Beat Assessment of Mitral Isthmus Conduction/Block

Assessment of Mitral Isthmus . Introduction: Mitral isthmus (MI) ablation for treatment of perimitral flutter is often performed during atrial fibrillation (AF) ablation but is technically challenging. Traditional assessment of MI conduction by left atrial activation mapping while pacing from either side of the line is time‐consuming, and cannot be performed during ongoing ablation. Analysis of the coronary sinus (CS) activation pattern during left atrial appendage (LAA) pacing has been proposed as a simpler technique for evaluating MI conduction, enabling beat‐to‐beat assessment of conduction during ablation procedures and prompt identification of conduction block. Methods: MI conduction was evaluated in 40 patients undergoing MI ablation using both: ((i) endocardial activation mapping and other standard techniques, and (ii) CS activation pattern during LAA pacing (change from distal‐to‐proximal activation to proximal‐to‐distal taken to signify the onset of MI block) Results: CS activation sequence was used to assess conduction in 39 of 40 patients (unable to advance CS catheter distally in one case). MI block was achieved in 36 of 39 cases. The mean MI conduction time (LAA to distal CS) was 92.9 ± 25.9 ms prior to ablation and 178.4 ± 59.9 ms after MI block was confirmed. The mean step‐out in conduction time at point of block was 80.8 ± 40.6 ms. In all individuals in whom CS activation indicated block, there was concordance with endocardial activation, differential pacing and, where detectable, presence of widely split double potentials. CS lesions were required to achieve block in 24 of 36 (67%) successful cases. Radiofrequency application time and procedure time to achieve MI block were 10.8 ± 6.0 minutes and 21.1 ± 15.3 minutes, respectively. (J Cardiovasc Electrophysiol, Vol. 21, pp. 418–422, April 2010)     

Characteristics of virtual unipolar electrograms for detecting isthmus block during radiofrequency ablation of typical atrial flutter

OBJECTIVES: The purpose of this study was to investigate the characteristics of the second component of local virtual unipolar electrograms recorded at the ablation line during coronary sinus (CS) pacing after radiofrequency ablation (RFA) of the cavotricuspid isthmus (CTI) for typical atrial flutter (AFL). BACKGROUND: Radiofrequency ablation of the CTI can produce local double potentials at the ablation line. The second component of unipolar electrograms represents the approaching wavefront in the right atrium opposite the pacing site. We hypothesized that the morphologic characteristics of the second component of double potentials would be useful in detecting complete CTI block. METHODS: Radiofrequency ablation of the CTI was performed in 52 patients (males = 37, females = 15, 62 +/- 12 years) with typical AFL. The noncontact mapping system (Ensite 3000, Endocardial Solutions, St. Paul, Minnesota) was used to guide RFA. Virtual unipolar electrograms along the ablation line during CS pacing after RFA were analyzed. Complete or incomplete CTI block was confirmed by the activation sequence on the halo catheter and noncontact mapping. RESULTS: Three groups were classified after ablation. Group I (n = 37) had complete bidirectional CTI block. During CS pacing, the second component of unipolar electrograms showed an R or Rs pattern. Group II (n = 12) had incomplete CTI block. The second component of unipolar electrograms showed an rS pattern. Group III (n = 3) had complete CTI block with transcristal conduction. The second component of unipolar electrograms showed an rSR pattern. CONCLUSIONS: A predominant R-wave pattern in the second component of unipolar double potentials at the ablation line indicates complete CTI block, even in the presence of transcristal conduction.     

Double potentials along the ablation line as a guide to radiofrequency ablation of typical atrial flutter

OBJECTIVES: The purpose of this study was to determine the characteristics of double potentials (DPs) that are helpful in guiding ablation within the cavo-tricuspid isthmus. BACKGROUND: Double potentials have been considered a reliable criterion of cavo-tricuspid isthmus block in patients undergoing radiofrequency ablation of typical atrial flutter (AFL). However, the minimal degree of separation of the two components of DPs needed to indicate complete block has not been well defined. METHODS: Radiofrequency ablation was performed in 30 patients with isthmus-dependent AFL. Bipolar electrograms were recorded along the ablation line during proximal coronary sinus pacing at sites at which radiofrequency ablation resulted in incomplete or complete isthmus block. RESULTS: Double potentials were observed at 42% of recording sites when there was incomplete isthmus block, compared with 100% of recording sites when the block was complete. The mean intervals separating the two components of DPs were 65 +/- 21 ms and 135 +/- 30 ms during incomplete and complete block, respectively (p < 0.001). An interval separating the two components of DPs (DP(1-2) interval) <90 ms was always associated with a local gap, whereas a DP(1-2) interval > or =110 ms was always associated with local block. When the DP(1-2) interval was between 90 and 110 ms, an isoelectric segment within the DP and a negative polarity in the second component of the DP were helpful in indicating local isthmus block. A DP(1-2) interval > or =90 ms with a maximal variation of 15 ms along the entire ablation line was an indicator of complete block in the cavo-tricuspid isthmus. CONCLUSIONS: Detailed analysis of DPs is helpful in identifying gaps in the ablation line and in distinguishing complete from incomplete isthmus block in patients undergoing radiofrequency ablation of typical AFL.     

Differential Pacing for Distinguishing Slow Conduction from Complete Conduction Block of the Tricuspid-Inferior Vena Cava Isthmus after Radiofrequency Ablation for Atrial Flutter—Role of Transverse Conduction through the Crista Terminalis

Background: Partial conduction block has been suggested a predictor of recurrence of atrial flutter (AFL).Aim: The aim of this study was to assess transverse conduction by the crista terminalis (CT) as a problem in evaluating isthmus block and the usefulness of differential pacing for distinguishing slow conduction (SC) and complete conduction block (CB) across the ablation line.Methods: We assessed 14 patients who underwent radiofrequency catheter ablation of the eustachian valve/ridge–tricuspid valve isthmus for typical AFL. Activation patterns along the tricuspid annulus (TA) suggested incomplete CB across the isthmus. In these patients, atrial pacing was performed from the low posteroseptal (PS) and anteroseptal (AS) right atrium (RA) while the ablation catheter was placed at the ablation line where double potentials (DPs) could be recorded. The pattern of activation of the RA free wall was assessed by a 20-pole catheter positioned along the CT during pacing from the coronary sinus (CS) ostium (CSos) and low lateral RA (LLRA).Results: Faster transverse conduction across the CT resulted in simultaneous or earlier activation of the distal halo electrodes than of the more proximal electrodes, suggesting incomplete conduction block across the isthmus. CB (13) and SC (1) were detected as changes in the activation times of the first and second components of DPs (DP1, DP2) during PS RA pacing and AS RA. Similar changes in the activation times DP1 and DP2 during AS RA pacing as compared to PS RA reflected SC through the isthmus, whereas increased DP1 activation time and decreased of DP2 activation time reflected complete conduction block across the isthmus.Conclusions: Transverse conduction across the CT influences the sequence of activation along the TA after isthmus ablation. Differential pacing can distinguish SC from complete conduction block across the ablation line in the isthmus.     

New insights into typical atrial flutter ablation: extra-isthmus activation time on the flutter wave is predictive of extra-isthmus conduction time after isthmus block

Purpose

Catheter ablation of typical atrial flutter (AFl) is succesful if double electrograms on the ablation line are widely separated. Nevertheless, a small interval may also be compatible with complete isthmus block. Predicting such a situation may avoid useless additionnal radiofrequency (RF) applications. We postulated that measuring the extra-isthmus activation time (EIAT) on the counterclockwise (CCW) flutter wave is correlated with the extra-isthmus conduction time after a proven block.

Methods

Files of 76 patients (71 males, 71?±?12 years) ablated for typical CCW AFl were reviewed. Ten had 2/1 conduction prohibiting reliable measurement. Three patients with proven crista terminalis shunt were also excluded. In the remaining 63 patients, EIAT was measured on the surface ECG before the first RF pulse from the beginning of the negative deflection of the F wave in lead III to the end of the positive deflection (or beginning of the plateau). After successful ablation and completion of block, right atrial (RA) CCW (during low septal pacing), and clockwise (CW) (during low lateral pacing) activation times were measured.

Results

Flutter cycle length was 247?±?34 ms and EIAT was 142?±?25 ms. A bidirectionnal isthmus block was obtained in all patients after an RF delivery time of 623?±?546 s. At a pacing cycle length of 681?±?71 ms, RA CCW and CW activation times were 147?±?23 and 139?±?26 ms, respectively. There was a good correlation between EIA, RA CCW (r?=?0.75, p?<?0.0001), and CW (r?=?0.69, p?=?0.0002) activation times.

Conclusion

EIAT on the flutter wave is an easy and feasible measure. It is correlated with extra-isthmus RA conduction time after block completion. EIAT can be used as a measure to predict the post cavo-tricuspid isthmus block RA activation time.     

The usefulness of surface 12-lead electrocardiogram to predict intra-atrial conduction block after successful atrial flutter ablation

Intraatrial conduction block at the inferior vena cava-tricuspid annulus isthmus was shown to predict successful atrial flutter ablation. However, its demonstration requires the use of several electrode catheters. Thus, a simple approach using surface 12-lead ECG to prove the conduction block would be valuable. Twenty-two patients were prospectively studied during low septal and low lateral atrial pacing before and after successful atrial flutter ablation. Creation of the conduction block was confirmed by comparing the sequence of atrial activation using 3 multipolar catheters during atrial pacing before and after ablation. During low septal pacing, there was no significant difference before and after ablation in P-wave width, axis, or morphology. During low lateral atrial pacing, there was a significant P-wave axis rotation towards the right (from -67 +/- 27 degrees to +13 +/- 35 degrees, P <.001), and P-wave polarity in limb lead II changed from predominantly negative to predominantly positive in 21 of 22 patients. There was also an increase in P-wave width (from 136 +/- 32 to 169 +/- 36 ms, P <.001) and stimulus-to-QRS interval (from 268 +/- 61 ms to 343 +/- 95 ms, P <.001) during low lateral pacing that was not observed during low septal pacing. We conclude that creation of a conduction block in the inferior vena cava-tricuspid annulus isthmus modifies surface 12-lead ECG during low lateral atrial pacing only. We also suggest that P-wave polarity in limb lead II during low lateral pacing could be used as a noninvasive marker of unidirectional counter-clockwise conduction block during atrial flutter ablation.