不典型房室结折返性心动过速与房室折返性心动过速的电生理鉴别

房室结折返性心动过速(AVNRT)与房室折返性心动过速(AVRT)的鉴别有时较困难,尤其是不典型AVNRT与间隔旁道参与的AVRT鉴别,不典型AVNRT在心动过速发生时最早心房激动位于后间隔区域,与后间隔旁道引起的AVRT相似。通常检测房室结双径路的电生理方法仅能鉴别63%的不典型AVNRT。该文介绍了两者的主要电生理鉴别方法,包括希氏束旁起搏、在希氏束不应期给予心室期前程序刺激、心室或希氏束旁起搏后间期与心动过速周长之差(PPI-TCL)和刺激信号至心房波减去室房(SA-VA)间期的区别、校正的心室PPI-TCL和VA间期、心动过速时VA分离现象及TCL行心室起搏时的VA间期与心动过速时的VA间期之差等9种方法。     

希氏束旁起搏鉴别间隔部隐匿性AVRT与AVNRT的临床价值

目的探讨希氏束旁起搏鉴别间隔部隐匿性房室旁道与慢-快型房室结折返性心动过速(AVNRT)的临床价值. 方法采用希氏束逆传不应期心室早搏刺激法将61例患者分别诊断为37例慢-快AVNRT和24例间隔部房室折返性心动过速(AVRT);再对61例患者采用希氏束旁起搏方法进一步检测. 结果采用希氏束旁起搏法检测37例AVNRT患者中有6例未检测成功,其余31例均为逆传房室结图形;24例AVRT患者中4例未检测成功,15例呈逆传旁道/旁道图形,5例呈非逆传旁道/旁道图形.如以逆传旁道/旁道图形为标准,鉴别间隔快旁路引起的AVRT与慢-快型房室结折返性心动过速,敏感性75%,特异性可达100%.结论希氏束旁刺激法对鉴别诊断AVRT与AVNRT有较高的特异性.     

His束逆传不应期心室早搏刺激鉴别间隔隐匿性旁道与房室结折返性心动过速

探讨His束逆传不应期心室早搏刺激法临床应用时的注意事项。 37例慢 快型房室结折返性心动过速(AVNRT)和 2 0例间隔部隐匿性快旁道引起的房室折返性心动过速 (AVRT)患者 ,成功消融前在常规行腔内电生理检查的同时均行His束逆传不应期心室早搏刺激法。结果 :心动过速时His束逆传不应期内心室早搏刺激 ,37例AVNRT患者心房激动无明显提前 ,2 0例AVRT心房被提前激动超过 2 0 (30～ 5 0 )ms ,其中 9例终止心动过速 ,此方法鉴别AVRT和AVNRT特异度、灵敏度较高。结论 :心动过速时His束逆传不应期行心室早搏刺激法鉴别诊断AVRT和AVNRT操作简单、准确性高。但行此法检查时要求有持续发作的心动过速 ;能够标测出清晰的His束电位 ;心室早搏刺激最好与His束电位同步发放 ;反复多次重复检测以进一步提高诊断的正确性     

右中间隔心底部和心尖部刺激鉴别间隔部隐匿性房室旁道的作用

目的评价右中间隔心底部和心尖部刺激对间隔隐匿性房室折返性心动过速(AVRT)的诊断价值。方法通过希氏束逆传不应期行心室早搏刺激法将142例患者分为74例慢-快型房室结折返性心动过速(AVNRT)和68例间隔隐匿性快旁道引起的AVRT患者,成功消融前均常规行腔内电生理检查,并在此基础上加用同频率右中间隔心底部和心尖部刺激:窦性心律时以120次/min的相同频率,分别刺激心尖和心底部,比较各自右心室的V波至逆传心房产生逆传A波的时限(VA)。结果希氏束逆传不应期行心室早搏刺激检测结果:心动过速时,希氏束逆传不应期内心室早搏刺激,74例快-慢型AVNRT患者心房激动不能提前(变化小于10ms),68例AVRT患者心房均被提前激动超过20ms(30～50ms)。同频率心尖部和右中间隔心底部刺激法检测结果:心尖部刺激所测的VA减去自身心底刺激所测的VA差值AVNRT患者为-65～6(-41±17)ms;间隔旁道引起的AVRT患者22～63(34±10)ms,两者间差异有统计学意义(P<0.01)。各例间隔旁道引起的AVRT患者的差值均大于10ms,各例AVNRT患者均小于10ms,两者间无重叠现象出现。5例AVNRT患者和3例间隔旁道引起的AVRT患者检测失败。结论窦性心律时同频率心尖部、右中间隔心底部起搏刺激法鉴别诊断AVRT和AVNRT的敏感性和特异性很高,而且操作简单,便于在临床上推广应用。     

希氏束旁起搏鉴别间隔部隐匿性AVRT与AVNRT的临床价值

目的：探讨希氏束旁起搏鉴别间隔部隐匿性房室旁道与慢一快型房室结折返性心动过速（AVNRT）的临床价值。方法：采用希氏束逆传不应期心室早搏刺激法将61例患者分别诊断为37例慢一快AVNRT和24例间隔部房室折返性心动过速（AVRT）；再对61例患者采用希氏束旁起搏方法进一步检测。结果：采用希氏束旁起搏法检测37例AVNRT患者中有6例未检测成功，其余31例均为逆传房室结图形；24例AVRT患者中4例未检测成功，15例呈逆传旁道／旁道图形，5例呈非逆传旁道／旁道图形。如以逆传旁道／旁道图形为标准，鉴别间隔快旁路引起的AVRT与慢一快型房室结折返性心动过速，敏感性75％，特异性可达1009／6。结论：希氏束旁刺激法对鉴别诊断AVRT与AVNRT有较高的特异性。     

心室融合波伴心房激动提前对间隔旁路逆传的房室折返性心动过速的诊断作用

目的 观察心室融合波伴心房激动提前对间隔旁路逆传的顺向型房室折返性心动过速(OAVRT)的诊断作用。方法 按心内电生理检查标准和射频消融结果，将47例符合人选条件的患者分为两组：房室结折返性心动过速(AVNRT)组和间隔旁路逆传的0AVRT组，分别为24例和23例。心动过速时行心室期前程序刺激(RS2刺激)和心室快速刺激，测量体表心电图上心室融合波之后的心房激动时间是否提前。结果 RS2刺激和心室快速刺激均能形成多个心室融合波。AVNRT组无l例伴有心房激动提前(特异性100％)，而OAVRT组在心室刺激成分明显的心室融合波时，心房激动均被提前(敏感性100％)。两组间的差异十分显著(P＜0．001)。结论 心室融合波伴心房激动时间提前是诊断间隔旁路逆传OAVRT的可靠指标，具有敏感性和特异性高的特点，而且也可用于未能记录到希氏束电图的患者。     

食管心脏电生理技术与临床应用（4）--食管心脏电生理技术基础

1食管心脏电生理检查的基本参数 1.1心脏起搏术语（1）S波：为刺激仪发放的电脉冲形成,在心电图上表现出高尖的钉状波。（2）起搏P波：有效起搏后的心房激动波,与S波密切相关,如S波后无P波表示该次电脉冲起搏无效（心房处于有效不应期时例外）。（3）起搏QRS波群：心房起搏激动沿房室结-希浦系统或房室旁道顺传形成的心室激动波,形态应与窦性激动一致。形态异常时,要根据电生理特性进行分析,注意房室传导关系和QRS形态。（4）S1引起的P波、QRS波群称为P1、R1,S2引起的P波、QRS波群称为P2、R2。余分别以此类推。（5）S-P间期：从S波起始到P波起始,代表电脉冲经食管至心房开始激动时的时距。（6）S-R间期：从S波起始到QRS波群起始,在S波有效起搏心房,但其后P波不清楚时代表房室传导时间。（7） P1-R1（S1-R1）间期：代表基础刺激时的房室传导时间。（8）P2-R2（S2-R2）间期：代表S2期前刺激时的房室传导时间。（9）逆行P波：在房室折返性心动过速、房室结折返性心动过速、室性心动过速、房室交接区性期前收缩、室性期前收缩等发生逆传时形成的P波,以P-波表示。（10）逆行心房激动顺序：①中心性激动：心律失常时激动沿房室结或间隔部房室旁道逆传至心房,造成间隔部心房肌先激动,然后分别向两侧心房传导,这种左、右心房几乎同时开始激动的顺序称为中心性激动。心电图表现出V1与食管导联的P-波几乎同时出现;②右侧偏心性激动：房室折返性心动过速时激动沿右侧壁房室旁道逆传至右心房,然后通过房间隔向左心房传播,这种逆传心房激动顺序称为右侧偏心性激动,心电图表现出V1的P-波早于食管导联出现;③左侧偏心性激动：房室折返性心动过速时激动沿左侧壁房室旁道逆传至左心房,然后通过房间隔?     

希氏束旁起搏鉴别间隔部隐匿性房室快旁道的临床价值

目的:探讨希氏束旁起搏鉴别间隔部隐匿性房室快旁道的临床价值。方法:采用希氏束逆传不应期心室期前收缩刺激法,将142例患者诊断为慢-快型房室结折返性心动过速(AVNRT)74例和间隔部隐匿性房室折返性心动过速(AVRT)68例。对142例患者采用希氏束旁起搏方法进一步检测。结果:希氏束旁刺激法检测结果显示,74例AVNRT患者中8例未检测成功,其余66例均为逆传房室结图形;68例AVRT患者中6例未检测成功,其余62例患者中48例均呈逆传旁道/旁道图形,14例呈非逆传旁道/旁道图形。如果以逆传旁道/旁道图形为标准鉴别间隔部快旁道引起的AVRT与慢-快型AVNRT,敏感性为77%,特异性为100%。结论:希氏束旁刺激法对间隔部隐匿性房室快旁道的鉴别诊断有很高的特异性。     

室性期前收缩揭示的室房传导现象

正心室异位搏动或起搏时,激动沿正常房室通道或旁道从心室传到心房时所表现的心电现象称为室房传导现象[1]。室房传导是房室结折返性心动过速、起搏介导性心动过速等心电现象的电生理基础,也是引发起搏器综合征的主要原因[1-2]。当心脏传导系及各腔室处于静息状态时,心房激动可通过房室交界区下传、并激动心室,同样,心室激动也可通过房室通道逆传心房。在有房室旁道解剖结构的基础上,心     

左侧斜行旁道心腔内心电图特征及射频导管消融

目的 探讨快速、准确标测左侧斜行旁道消融靶点的方法，提高导管消融成功率。方法 对66例AVRT患者在高位右心房刺激、心室刺激或室性期前收缩、诱发室上性心动过速及窦性心律时进行心腔内电生理检查，确定旁道的走行方向，标测心室及心房侧靶点图，记录消融靶点位置及消融时间。结果 发现6例旁道走行方向斜跨二尖瓣环并确定为斜行旁道，经主动脉逆行法最终全部消融成功，部分病例耗时较长。结论 如果冠状窦标测电极(CS)记录到的最早逆行心房激动点和最早顺传心室激动点不在同一记录直线上，在排除多旁道后应考虑斜行旁道的可能，同时可判断其斜行程度。最早逆行心房激动点和最早顺传心室激动点分别是心房侧和心室侧的消融靶点。如能标测到旁道电位，成功率更高。对于隐匿性左侧旁道，左心室起搏信号s到cs上最早逆传至A波的最短间隔处是很好的消融靶点。     

First postpacing interval after tachycardia entrainment with correction for atrioventricular node delay: A simple maneuver for differential diagnosis of atrioventricular nodal reentrant tachycardias versus orthodromic reciprocating tachycardias

BACKGROUND: The difference between the first postpacing interval (PPI) after tachycardia entrainment from the right ventricular apex and the tachycardia cycle length (TCL) can be used as an index of proximity to the circuit. OBJECTIVES: The purpose of this study was to determine whether the response to entrainment of tachycardia during ventricular stimulation with correction for AV node delay is a useful, simple maneuver for differentiating AV nodal reentrant tachycardia (AVNRT) from orthodromic reciprocating tachycardia (ORT) using a concealed accessory pathway. METHODS: The study consisted of 193 consecutive patients who underwent electrophysiologic study and ablation of regular paroxysmal supraventricular tachycardia without preexcitation during sinus rhythm. Tachycardia entrainment was attempted through trains of 5 to 15 right ventricular apex pacing pulses. The increment in AV nodal conduction time in the first PPI was subtracted from the PPI-TCL difference (corrected PPI-TCL). RESULTS: Electrophysiologic study demonstrated ORT in 84 patients and AVNRT in 109 patients. Transient entrainment was achieved in all but 12 patients. The mean corrected PPI-TCL difference was significantly shorter in 77 patients with ORT (66 +/- 27 ms) than in 104 AVNRT patients (151 +/- 28 ms; P <.0001). Patients with septal accessory pathways had shorter corrected PPI-TCL differences than patients with free-wall accessory pathways. The presence of a corrected PPI-TCL difference <110 ms identified all but one patient with ORT, and no patients with AVNRT had such a difference. CONCLUSION: The return cycle after tachycardia entrainment by right ventricular apex stimulation with correction for AV node delay is a rapid, useful maneuver for differential diagnosis of AVNRT vs ORT in patients without preexcitation. The presence of a corrected PPI-TCL <110 ms accurately identified with high reliability those patients with ORT.     

心室起搏拖带对房室结折返性和间隔旁路参与的房室折返性心动过速的鉴别作用

目的　研究心动过速时心室起搏拖带对房室结折返性心动过速 (AVNRT )和间隔旁路参与的顺向型房室折返性心动过速 (间隔旁路ORT)的鉴别意义。方法　 30例AVNRT和 2 5例间隔旁路ORT病人在心动过速发生后 ,采用较心动过速的周长 (TCL)短 10～ 4 0ms的周长行右心室起搏拖带心动过速。测量右心室起搏之前的心室 心房 (VA)间期和TCL。停止起搏后 ,测量最后一次刺激信号至最后起搏拖带的心房激动 (SA)间期 ,以及起搏后间期 (PPI)。结果　所有 30例AVNRT病人的SA -VA间期 >85ms、PPI-TCL >115ms,而 2 5例ORT病人的SA -VA间期 <85ms、PPI-TCL <115ms。结论　PPI TCL和SA VA间期是鉴别AVNRT和间隔旁路ORT的非常可靠的指标 ,具有较高的特异性。     

Significance of pacing cycle lengths in manifest entrainment of orthodromic circus movement tachycardia by ventricular pacing

The physiology of entrainment of orthodromic circus movement tachycardia (CMT) was studied using ventricular pacing during 18 episodes of induced CMT in 7 patients with atrioventricular (AV) accessory pathways. The first paced impulse was delivered as late as possible in the tachycardia cycle (mean 88 +/- 5% of the spontaneous cycle length [CL]). Entrainment was demonstrated by the following criteria: 1:1 retrograde conduction via the accessory pathway; capture of atrial, ventricular and His bundle electrograms at the pacing rate; and resumption of tachycardia at its previous rate after cessation of pacing. The number of ventricular paced impulses ranged from 5 to 14 (mean 8 +/- 3), and entrainment occurred in 2 to 7 paced cycles (mean 4 +/- 2). Orthodromic activation of a major part of the reentry circuit (manifest entrainment) was demonstrated during 9 episodes by the occurrence of His bundle electrogram preceding the first CMT QRS at the time anticipated from the last paced beat. In the 9 other episodes, persistent retrograde His bundle activation and AV nodal penetration by each paced impulse caused a delay (mean 79 +/- 25 ms) in activation of the His bundle preceding the first CMT QRS after the last paced beat. The mean pacing CL achieving manifest entrainment was 92 +/- 3% of the tachycardia CL, compared with 84 +/- 3% for retrograde AV nodal penetration (p less than 0.01). In conclusion, manifest entrainment of orthodromic CMT can be demonstrated by ventricular pacing at very long CLs; shorter CLs may cause CMT termination due to retrograde AV nodal penetration.     

Entrainment of circus movement tachycardia utilizing an accessory pathway with long retrograde conduction times during ventricular and atrial stimulation

An unusual case is presented in which a circus movement tachycardia incorporating an accessory pathway with long retrograde conduction time was transiently entrained. Overdrive high right atrial stimulation produced entrainment without atrial fusion since collision of anterograde and retrograde impulses took place within the accessory pathway. Tachycardia termination occurred when, at a faster pacing rate, an atrial impulse that collided in the accessory pathway was blocked at the atrioventricular (AV) node. In contrast, the entrainment seen during right ventricular apical stimulation was characterized by the occurrence of both fusion and collision within the ventricles. The tachycardia was terminated when a pure paced impulse that collided in the normal pathway was blocked in a retrograde direction in the accessory pathway. These data indicate that: 1) transient entrainment of this arrhythmia (circus movement tachycardia) can be identified by the classical criteria used to diagnose it, provided that fusion and collision occur within the ventricles; and 2) the accessory pathway is the weak link for tachycardia termination only during ventricular pacing since the AV node is the weak link during atrial stimulation.     

Electrocardiogram during tachycardia in patients with anterograde conduction over a Mahaim fiber: old criteria revisited.

OBJECTIVES: The aim of this study was to prospectively evaluate the sensitivity, specificity, and positive and negative predictive values of previously described ECG criteria to identify preexcited tachycardia due to decrementally conducting accessory pathways (QRS axis between 0 and -75 degrees , QRS width < or = 0.15 seconds, an R wave in lead I, an rS pattern in lead V(1), RS > 1 QRS transition > V(4), and cycle length between 220 and 450 ms). BACKGROUND: Preexcited tachycardia associated with decrementally conducting right-sided accessory pathways usually shows a rather "narrow" QRS complex and can be difficult to differentiate from supraventricular tachycardia (SVT) with left bundle branch block (LBBB) aberrant conduction. METHODS: We analyzed three groups of patients: 32 patients with an atriofascicular pathway (group I); 8 patients with long (n = 3) or short (n = 5) decrementally conducting right-sided AV pathway (group II); and a control group that consisted of 35 patients with SVT and LBBB (group III). RESULTS: Presence of all six criteria had 87.5% sensitivity in group I and a 0% sensitivity in group II. There were four false negatives in group I. The negative predictive value was 82.5%, with six false positives in group III (five patients with an aberrant LBBB-shaped tachycardia with ventriculoatrial conduction over an accessory AV pathway). The criterion cycle length was not helpful. CONCLUSIONS: Criteria for identifying a tachycardia with anterograde conduction over a Mahaim fiber are helpful only in atriofascicular pathways, with a sensitivity of 87.5% and a negative predictive value of 82.5%. The major cause of false positives was a tachycardia with aberrant LBBB conduction and ventriculoatrial conduction over an accessory AV pathway.     

Reliability of retrograde atrial activation patterns during ventricular pacing for localizing accessory pathways

Definitive localization of accessory pathways is based on atrial activation patterns during orthodromic supraventricular tachycardia when retrograde conduction occurs exclusively through the accessory pathway. In some patients, supraventricular tachycardia cannot be induced or is deleterious. To determine whether accessory pathway sites can be identified accurately during ventricular pacing, retrograde atrial activation was assessed during orthodromic supraventricular tachycardia and ventricular pacing at multiple cycle lengths in 41 patients with a single accessory pathway. To obviate retrograde fusion due to concomitant conduction through the normal atrioventricular (AV) conduction system that may obscure the location of the accessory pathway, the difference in conduction time from the site of earliest atrial activation to the His bundle atrial electrogram (delta A-SVT) was measured during orthodromic supraventricular tachycardia and compared with values observed during ventricular pacing (delta A-VP). Characteristic values for the delta A-SVT interval were identified for left lateral (66 +/- 17 ms), left posterior (50 +/- 8 ms), posteroseptal (33 +/- 7 ms), right free wall (22 +/- 15 ms) and anteroseptal (0 +/- 0 ms) accessory pathway sites. During ventricular pacing, the site with the earliest atrial electrogram was used to define the accessory pathway location only if the maximal value of the delta A-VP interval over the range of cycle lengths assessed was comparable with the value of the delta A-SVT interval characteristic of that region. Values of the delta A-SVT interval correlated closely with the maximal values of the delta A-VP interval (r = 0.91). With this approach, 40 (98%) of 41 accessory pathway sites were identified correctly during ventricular pacing.(ABSTRACT TRUNCATED AT 250 WORDS)     

Investigation of the preexcitation syndromes

Assessment of the localization and function of accessory atrioventricular pathways may be undertaken with noninvasive and invasive examination techniques. Noninvasive methods, however, such as electrocardiography, vectorcardiography, precordial mapping, echocardiography and scintigraphy do not enable exact delineation of the site of the accessory pathway since, in general, their use requires maximal preexcitation; moreover, they are of less value in the presence of septal bundles, multiple accessory pathways or intraventricular conduction disturbances. Accordingly, localization of accessory atrioventricular pathways is based on data obtained from intracardiac electrography such as the interval between stimulus and delta wave during atrial pacing, retrograde atrial sequence, VA conduction time at onset of right or left bundle branch block as well as responses to programmed ventricular stimulation during orthodromic reciprocating tachycardia. The most exact method for determination of the localization of the Kent bundle employs intraoperative endocardial and epicardial mapping with analysis of VA and AV conduction times during reciprocating tachycardia, ventricular stimulation and atrial pacing. The conduction properties of the accessory atrioventricular bundle may be estimated noninvasively based on the persistence of a delta wave as a function of the heart rate, the influence of antiarrhythmic agents on the anterograde conduction via the normal pathway as well as the shortest interval between two consecutive QRS complexes with delta waves during atrial fibrillation. Functional assessment is carried out invasively through recording the anterograde and retrograde refractory periods of the Kent bundle as well as observations during programmed atrial and ventricular stimulation or induced atrial fibrillation.     

The preexcitation index: an aid in determining the mechanism of supraventricular tachycardia and localizing accessory pathways

In this study we sought to determine whether characteristics of ventricular-induced atrial preexcitation during reciprocating tachycardia could help differentiate atrioventricular (AV) nodal reentry from orthodromic AV reentry using an accessory pathway and to identify the site of accessory pathways in patients with Wolff-Parkinson-White syndrome. Fifty-five patients with orthodromic AV reciprocating tachycardia and 22 patients with AV nodal reentrant tachycardia were studied with standard electrophysiologic techniques. There were 24 left free wall, 23 posterior septal, seven anterior septal, and one right free wall accessory pathways. Progressively premature right ventricular complexes (V2) were introduced during reciprocating tachycardia (V1V1). The V1V1 interval during tachycardia minus the longest V1V2 at which atrial preexcitation occurred defined a preexcitation index (PI). Atrial preexcitation occurred in 49 of 55 (89%) patients with AV reentry compared with only three of 22 (14%) patients with AV nodal reentry (p less than .001). In the three patients with AV nodal reentry who demonstrated atrial preexcitation, the PI was distinct from that of the septal pathways and was in the upper range of values for left free wall pathways. The percentage of tachycardias demonstrating atrial preexcitation was not different between the free wall and septal pathways, but His bundle activation was visible at the time of atrial preexcitation in only six of 17 (35%) left free wall compared with 13 of 16 (81%) posterior septal and seven of seven (100%) anterior septal pathways (p less than .05 free wall vs posterior or anterior septal).(ABSTRACT TRUNCATED AT 250 WORDS)     

Preexcited reciprocating tachycardia in patients with Wolff-Parkinson-White syndrome: incidence and mechanisms

During the electrophysiologic study of 435 patients referred for evaluation of Wolff-Parkinson-White syndrome, 42 (10%) had preexcited reciprocating tachycardia (defined as a macro-reentrant tachycardia that used an accessory atrioventricular [AV] pathway for antegrade conduction). The ages of the patients ranged from 9 to 67 years (27 +/- 14). Thirty-three were male patients, nine female, and eight had Ebstein's anomaly. Preexcited reciprocating tachycardia cycle length was 220 to 430 msec (294 +/- 42). Significant hemodynamic compromise in the laboratory directly related to preexcitated reciprocating tachycardia occurred in only one patient. However, in 10 patients a transformation to atrial fibrillation was seen after a spontaneously occurring premature atrial contraction. Only 17 of the 42 patients with preexcited reciprocating tachycardia during electrophysiologic study had the same tachycardia documented clinically. These 17 patients were more often younger with multiple accessory pathways and with no history of orthodromic reciprocating tachycardia when compared with 25 patients in whom preexcited reciprocating tachycardia could be induced only in the laboratory. Preexcited reciprocating tachycardia was induced in the laboratory in 22 of 374 (6%) patients with single accessory pathways and in 20 of 61 (33%) of those with multiple accessory pathways. In the 20 patients with multiple accessory pathways, the spectrum of reentrant circuits included fusion over two or more accessory pathways or fusion over both an accessory pathway and the AV node. In the 22 patients with a single accessory pathway and true antidromic reciprocating tachycardia, all but two episodes were at least 4 cm from the AV node. No patient with true antidromic reciprocating tachycardia had a posterior septal accessory AV pathway. Only in patients with multiple accessory pathways was the posterior septal accessory AV pathway used as the antegrade limb.     

Mode of initiation of reciprocating tachycardia during programmed ventricular stimulation in the Wolff-Parkinson-White syndrome: With reference to various patterns of ventriculoatrial conduction

The mode of initiation of reciprocating tachycardia in relation to various patterns of ventriculoatrial (V-A) conduction induced by programmed right ventricular stimulation was systematically analyzed in 29 patients with the Wolff-Parkinson-White (WPW) syndrome, type A. His bundle activity and atrial electrograms near the atrial ends of the normal and accessory pathways were simultaneously recorded. V-A conduction time was plotted as a function of premature ventricular coupling intervals. Four groups of patients were observed. In Group I, four patients with absence of V-A conduction, reciprocating tachycardia could not be elicited. In Group II, three patients with persistent retrograde atrial fusion from the normal and accessory pathways, reciprocating tachycardia could not be elicited because of a constant impulse collision at the atrial level. In Group III, seven patients with predominant or exclusive V-A conduction over the normal pathway, concealed retrograde penetration of the accessory pathway might have prevented the initiation of reciprocating tachycardia in all patients. In Group IV, 15 patients with predominant or exclusive V-A conduction over the accessory pathway, reciprocating tachycardia could be elicited only in 7, and its initiation appeared to depend upon the depth of retrograde penetration of the normal pathway; the less the depth of such penetration, the easier it was to elicit a reciprocating tachycardia. Furthermore, with the production of progressively less deep retrograde penetration of the normal pathway, development of repetitive ventricular responses at short ventricular coupling intervals and shortening of the ventricular driving cycle length favored the induction of reciprocating tachycardia in patients in this group. The study demonstrates that the initiation of reciprocating tachycardia during programmed ventricular stimulation in patients with the WPW syndrome is related to various patterns of V-A conduction.