Mahaim fiber: An atriofascicular or a long atrioventricular pathway?

There is debate concerning the distal insertion of Mahaim fibers. Some findings favor an atriofascicular fiber connected with the distal right bundle branch. Other findings favor a long atrioventricular (AV) structure inserting into the myocardium. A patient having a decrementally conducting accessory pathway is reported. Proximal and distal Mahaim potentials were recorded during sinus rhythm, atrial pacing, and antidromic tachycardia. Both proximal and distal M potentials always preceded the QRS complex during sinus rhythm and antidromic tachycardia earlier than the right bundle branch potential. During tachycardia, the distal M potential was recorded 6 ms before the retrograde right bundle potential. Other arguments consistent with an AV connection were a change in the QRS configuration during tachycardia after the first radiofrequency pulse at the site of the distal M potential and absence of right bundle branch block after successful ablation. Conduction through the proximal part of the Mahaim fiber was unaltered after ablation, as assessed by recording the proximal M potential. Electrophysiologic evidence is presented suggesting a long AV accessory pathway inserting close to the distal right bundle branch rather than an atriofascicular connection in this patient with a Mahaim fiber.     

Minimally decremental atriofascicular accessory pathway with bidirectional conduction

Atriofacicular pathways of Mahaim type are typically decrementally conducting accessory pathways without retrograde conduction properties, located on the right ventricular free wall at the tricuspid annulus. We report a patient with an atriofascicular pathway with minimal anterograde decremental conduction. Both long and short V-H antidromic atriofascicular reentrant tachycardias were induced and mechanism confirmed with electrophysiologic testing. Additionally, orthodromic atriofascicular reentrant tachycardia with narrow and right bundle branch block morphologies were inducible. Mahaim pathway was successfully ablated with elimination of both antidromic and orthodromic tachycardias.     

Spontaneous automaticity arising from a successfully ablated Mahaim fiber

The authors describe a 22-year-old woman with regular and irregular arrhythmias exhibiting left bundle branch block (LBBB) morphology at various heart rates. An atriofascicular fiber was diagnosed as the underlying mechanism for the antidromic reciprocating tachycardia. In addition, spontaneous automaticity of the Mahaim fiber was present during electrophysiologic study. The accessory pathway was ablated successfully, targeting a Mahaim potential at the supero-anterior tricuspid valve annulus. Relatively slow automatic rhythms with identical LBBB morphology were recorded immediately after ablation, as well as during long-term follow-up in a more sporadic and subclinical form. Abnormal automaticity arising from the distal portions of the remnant pathway was considered to be the origin of the slow ventricular rhythms in this peculiar case.     

Automaticity with anterograde conduction of a concealed accessory pathway due to radiofrequency energy application

We report a case of a patient with recurrent episodes of supraventricular tachycardia in which a concealed left-posterior accessory pathway-mediated orthodromic tachycardia was reproducibly induced during the EP study. Two interesting and very unusual electrophysiological phenomenon were observed at the same time during the ablation procedure of the accessory pathway: 1— Automaticity of the regular accessory atrioventricular pathway; 2— Emergence of manifest preexcitation following radiofrequency application exclusively during the automatic accessory pathway-mediated rhythm.     

房束旁道的电生理特点与Mahaim电位在射频导管消融中的意义

探讨房束旁道的电生理特点与Mahaim电位在射频导管消融 (RFCA)中的意义。 1997年 7月至 2 0 0 3年 1月对 3例拟诊为房束旁道引起的逆向型房室折返性心动过速的患者进行了电生理检查和RFCA。男 2例 ,女 1例 ,年龄分别为 18,2 3,2 5岁。心动过速发作史 7～ 16年 ,频率 180～ 2 30次 /分 ,发作时均有明显心悸 ,其中 1例伴头晕、胸闷。窦性心律时心电图 1例正常 ,另 2例示轻微预激。食管心房调搏与心房程序刺激均易诱发心动过速 ,心动过速时体表心电图呈宽QRS波形。 3例均在三尖瓣环右后侧壁标测到的Mahaim电位处 ,于窦性心律及心房起搏下放电消融。 2例彻底阻断旁道前向传导 ,另 1例反复放电未阻断旁道 ,但重复术前程序刺激心动过速不再诱发。分别随访 5年、2年、6个月心动过速均未复发。结论 :RFCA治疗房束旁道介导的心动过速安全有效 ,Mahaim电位在RFCA中具有重要指导价值。     

房室旁道间歇性逆传阻滞的探讨ioven

为探讨房室旁道间歇性逆传阻滞的发生机制及临床意义 ,对房室旁道患者射频导管消融术中作腔内电生理检查 ,观察房室顺传和室房逆传功能及途径。结果显示261例中有7例 (4例为隐匿性预激综合征 )为旁道逆向 (或双向 )传导阻滞 (2.7% )。尽管旁道间歇性逆传阻滞是一种少见现象 ,但由于旁道传导阻滞 ,无法对旁道进行定位及射频导管消融 ,因此了解旁道有无间歇性逆传阻滞 ,对射频导管消融治疗有临床意义     

Localization and radiofrequency ablation of atriofascicular pathways using electroanatomic mapping

Atriofascicular pathways supporting antidromic reentrant tachycardia are uncommon, and may be difficult to ablate. Traditional mapping can be associated with traumatic loss of atriofascicular conduction. Atriofascicular fibers can insert into the right bundle and will, therefore, first activate the right ventricle. In contrast to initial activation of the ventricle near the tricuspid annulus that can be seen in patients with right-sided decremental atrioventricular pathways. We used electroanatomic mapping to map and ablate the ventricular insertion of atriofascicular pathways in two patients during sinus rhythm and during atrial pacing. In our 2 cases an atriofascicular potential was recorded from below the tricuspid valve annulus and tagged. At this site, each pathway was ablated with one radiofrequency lesion. We describe 2 cases where electroanatomic mapping of the right ventricle was used to map and ablate atriofascicular pathways.     

Sequential dual chamber extrastimulation: A novel pacing maneuver to identify the presence of a slowly conducting concealed accessory pathway

BACKGROUND: Transient VA block can be created in the AV node (AVN) when an atrial extrastimulus is delivered at the AVN effective refractory period (ERP) due to anterograde concealed conduction. OBJECTIVE: We hypothesized that ventricular stimulation during pacing-induced AVN refractoriness could identify concealed accessory pathways (APs) that remain hidden with standard maneuvers. METHODS: Patients undergoing electrophysiological study for supraventricular tachycardia were screened for presence of an AP using standard pacing maneuvers and/or V pacing during adenosine infusion. The dual-chamber sequential extrastimulation maneuver consisted of an 8-beat drive train of simultaneous AV pacing at 600 msec, followed by an A2 delivered at AVN ERP, followed by a V2 delivered at the drive train cycle length (600 msec). Repeat drives were then performed with decrements of 10 msec for V2 until VA block was seen. Retrograde AVN and AP ERP were recorded with standard (V1, V2) and dual-chamber extrastimulation (A1/V1, A2, V2). Patients with an AP identified with standard pacing, manifest pre-excitation, or A ERP < AVN ERP were excluded. RESULTS: Fourteen patients with and 19 patients without an AP were studied. In all patients with an AP, exclusive VA conduction over the AP, without fusion, was seen with the described pacing maneuver. In patients without an AP, retrograde AV nodal ERP was extended by a mean of 138 +/- 46 msec (range 50 to 210 msec) with the A2. Anterograde concealed conduction into the AP was also seen in some patients who showed AP conduction during standard V1V2 pacing (mean retrograde extension of ERP 12 +/- 8 msec, range 0 to 20 msec). CONCLUSION: Dual-chamber sequential extrastimulation is a useful maneuver for identifying slowly conducting APs not revealed with standard pacing maneuvers because of an ERP and conduction time similar to the AVN. The maneuver uses anterograde concealed conduction to prolong AVN refractoriness much more than that of a concealed AP, thereby allowing the AP to become manifest with the V2.     

体表电位标测判定预激综合征旁路的评价

目的 评价体电位标测在房室旁路定位中的准确性和可行性。方法 ５２例常规行身频导管消融（ＲＦＣＡ）的显性激综合征（Ｗｏｌｆｆ－Ｐａｒｋｉｎｎｏｎ－Ｗｈｉｔｅ ｓｙｎｄｒｏｍｅ,ＷＰＷ）病人,订前后体表电位标测（Ｂｏｄｙ Ｓｕｒｆａｃｅ Ｐｏｔｅｎｉｔａｌ Ｍａｐｐｉｎｇ,ＢＳＰＭ）。旁路定位采用：（１）等电位图：除极４０ｍｓ后,稳定持续１０ｍｓ以上的极上值位置。（２）等积分图,等积分图中极小值的位置     

Functional bundle branch block and orthodromic reciprocating tachycardia cycle length: do not bet on accessory pathway location.

AIMS: To show 2 examples in which the analysis of the effect of bundle branch block on orthodromic reciprocating tachycardia cycle length was misleading. METHODS AND RESULTS: We performed an electrophysiological study in two patients with orthodromic reciprocating tachycardia showing a transition from wide to narrow QRS during tachycardia. Our two cases of left bundle branch block during reciprocating tachycardia using infero-septal pathways show that ventricular to atrial conduction time prolongation may be larger than 30 ms and may be concealed by a shortening of atrial to ventricular conduction time. In the 2 cases, the atrial insertion of the accessory pathway could be successfully ablated from the right atria at the ostium of the coronary sinus. CONCLUSIONS: The observation of the association between left bundle branch block and cycle length prolongation during reciprocating tachycardia may be associated with a successful ablation at the ostium of the coronary sinus.     

Part II—Clinical presentation,electrophysiologic characteristics,and when and how to ablate atriofascicular pathways and long and short decrementally conducting accessory pathways

Recognition of the presence, location, and properties of unusual accessory pathways for atrioventricular conduction is an exciting, frequently difficult, challenge for the clinical cardiac arrhythmologist. In this second part of our series of reviews relative to this topic, we discuss the steps required to achieve the correct diagnosis and appropriate management in patients with the so‐called “Mahaim” variants of pre‐excitation. We indicate that, nowadays, it is recognized that these abnormal rhythms are manifest because of the presence of atriofascicular pathways. These anatomical substrates, however, need to be distinguished from the other long and short accessory pathways which produce decremental atrioventricular conduction. The atriofascicular pathways, along with the long decrementally conducting pathways, have their atrial components located within the vestibule of the tricuspid valve. The short decremental pathways, in contrast, can originate in the vestibules of either the mitral or tricuspid valves. As a starting point, careful analysis of the 12‐lead electrocardiogram, taken during both sinus rhythm and tachycardias, should precede any investigation in the catheterization room. When assessing the patient in the electrophysiological laboratory, the use of programmed electrical stimulation from different intracardiac locations, combined with entrainment technique and activation mapping, should permit the establishment of the properties of the accessory pathways, and localization of its proximal and distal ends. This should provide the answer to the question “is the pathway incorporated into the circuit underlying the clinical tachycardia”. That information is essential for decision‐making with regard to need, and localization of the proper site, for catheter ablation.     

Catheter ablation of anteroseptal accessory pathway in the non-coronary aortic sinus.

We report a patient with atrioventricular reentrant tachycardia (AVRT) with bidirectional conduction over an anteroseptal accessory pathway (AP) who underwent successful ablation in the non-coronary aortic sinus (AS). In three previous attempts, the intracardiac recordings showed an anteroseptal AP with antegrade and retrograde conduction that failed to be ablated in spite of radiofrequency (RF) applications from the right and left anteroseptal regions. During the study, the earliest atrial activation during tachycardia was recorded in the non-coronary AS preceding the atrial activation at the His bundle (HB) region by 24 ms, and the anteroseptal AP was successfully blocked by one single ablation in the non-coronary AS. These data strongly suggest that careful mapping of an anteroseptal AP in the non-coronary AS may provide an alternative ablation approach in patients with previously failed ablation.     

三维标测指导下邻希氏束旁路消融的安全性和有效性

目的 描述邻希氏束旁路的电解剖特点,同时评价三维标测下邻希氏束旁路消融的安全性和有效性.方法 连续入选19例邻希氏束房室旁路折返性心动过速患者(男13例),年龄11 ～70(31.16±19.54)岁,采用三维标测指导旁路的射频消融治疗.所有患者旁路传导在放电后(3.57±1.71)s内阻断(即刻成功率100％).结果 顺向性房室折返性心动过速时靶点处室房间期(38.56±7.51) ms,明显短于希氏束区域[(51.11±8.07) ms,P＜0.001]和冠状静脉窦近端[(78.01±13.09)ms,P＜0.001].成功消融靶点与希氏束距离(6.42±1.71)mm,希氏束距离冠状静脉窦口(26.53±3.15) mm.靶点处的室/房波幅比为3.62±2.27,明确的希氏束电位(0.152±0.093) mV.平均随访(12.79±6.64)个月,18例患者无复发(远期成功率94.7％),且无房室传导损伤发生.结论 通过定量测量发现邻希氏束旁路极为靠近希氏束.采用三维标测指导消融邻希氏束旁路是安全有效的.     

旁道合并房室结双径路的电生理特征

采用经食管心房起搏和心内电生理检查方法，证实旁道（AP）合并房室给双径路（DAVNP）6例。心房程控起搏经房室结（AVN）前传有跳跃延长现象；诱发阵发性室上性心动过速（PSVT）时，表现为R－R间期长短交替或有两种频率的PSVT，其折返途径均为AVN前传，AP逆传。AP射频消融后，心房程控起搏经AVN仍有跳跃现象传导，但不能诱发PSVT，随访6～24月均无PSVT发作。     

主动脉无冠窦内射频消融前间隔房室旁路

目的 报道经主动脉无冠窦内射频消融前间隔房室旁路.方法 7例患者,男性4例,女性3例,平均年龄（38.4±14.7）岁.电生理检查证实存在房室旁路,并检查其前传逆传功能和诱发旁路参与的房室折返性心动过速.在心动过速时标测最早心房逆传激动点作为消融靶点.结果 7例心动过速时最早心房激动部位均位于前间隔区域,但经右心房途径反复消融均不能成功阻断旁路,而在无冠窦内可标测到最早逆传心房激动点并消融成功,无并发症出现.结论 主动脉无冠窦内消融可作为治疗前间隔房室旁路的一种新途径,特别适用于右心房前间隔区域消融失败的病例.     

后间隔房室旁路体表心电图的定位诊断

目的 探讨预激综合征在左、右及后间隔旁路的位置与体表心电图特征性改变的相关关系。方法 以80例预激综合征射频消融前后作对照,寻找体表心电图的特征性改变与左、右及后间隔旁路位置关系,确定体表心电图定位左、右及后间隔旁路的鉴别诊断标准,并计算其鉴别诊断的敏感性、特异性和准确率。结果 体表心电图的8大特征变化与预激左右后间隔旁路定位鉴别诊断有关,即V1导联QRS波形态、Δ波方向;Δ波及QRS波的额面电轴及二者差值;Ⅲ导联R／S波比值;胸前导联R／S＞1的转折点;PV1-PE间距。根据以上8大特点对术前80例预激重新定位,其鉴别诊断敏感性、特异度及准确率在右后间隔旁路分别是88．2％、83．3％和77．5％,而左后间隔是83．3％、88．2％、87．5％。结论 B型预激旁路绝大部分位于右后间隔旁路,但也不排除左后间隔旁路,尤其是左后旁路预激不安全时可出现B型预激改变,上述体表心电图的8大特征有助于二者鉴别诊断。