Retrograde dual atrioventricular nodal pathways

Thirty-one (3.5 percent) of 887 studied patients had retrograde dual atrioventricular (A-V) nodal pathways, as manifested by discontinuous retrograde A-V nodal conduction curves (29 patients) or by two sets of ventriculoatrial (V-A) conduction intervals at the same paced cycle length (2 patients). All patients had A-V nodal reentrant ventricular echoes of the unusual variety induced with ventricular stimulation (25 patients had single, 2 patients had double and 4 patients had more than three ventricular echoes). The weak link of the reentrant circuit was always the retrograde slow pathway. Eleven of the 31 patients also had anterograde dual A-V nodal pathways (bidirectional dual pathways). Eight patients (26 percent) had spontaneous as well as inducible A-V nodal reentrant paroxysmal supraventricular tachycardia (of the unusual type in three and the usual type in five). In addition, three patients (10 percent) had only inducible supraventricular tachycardia (two of the unusual and one of the usual type).Retrograde dual A-V nodal pathways are uncommon. They are associated with the finding of at least single A-V nodal reentrant ventricular echoes (all patients), anterograde dual pathways (one third of patients) and A-V nodal reentrant paroxysmal supraventricular tachycardia of the usual or unusual variety (one third of patients).     

Simultaneous anterograde fast-slow atrioventricular nodal pathway conduction after procainamide

Three patients with paroxysmal supraventricular tachycardia underwent electrophysiologic studies that included His bundle recordings, incremental atrial and ventricular pacing and extrastimulation before and after intravenous infusion of 500 mg of procainamide. In all three patients the tachycardia was induced during atrial pacing or premature atrial stimulation, or both. Two of the three patients had discontinuous atrioventricular (A-V) nodal curves with induction of a slow-fast tachycardia during failure in anterograde fast pathway conduction and one patient had a smooth A-V nodal curve with induction of a slow-fast tachycardia at critical A-H interval delays. After procainamide: (1) in all three patients atrial pacing induced A-V nodal Wenckebach periodicity (cycle length 300 to 400 ms) resulting in simultaneous anterograde fast and slow pathway conduction (one atrial beat resulting in two QRS complexes) and retrograde fast pathway conduction initiating an echo response or a slow-fast tachycardia, or both; (2) in all three patients there was enhanced conduction and shortening of refractoriness of the anterograde fast pathway and depressed conduction and lengthening of refractoriness of the retrograde fast pathway; and (3) in two patients there was inability to sustain tachycardia because of selective block within the retrograde fast pathway. In conclusion: (1) procainamide altered conduction and refractoriness of the anterograde fast and slow pathways so that simultaneous conduction could occur during atrial pacing, resulting in a double ventricular response and a slow-fast echo or tachycardia, or both; and (2) the differential effects of procainamide on anterograde fast and retrograde fast pathways suggests two functional A-V nodal fast pathways, one for anterograde and the other for retrograde conduction.     

Incessant nonreentrant atrioventricular nodal tachycardia due to multiple nodal pathways treated by radiofrequency ablation of the slow pathways

In patients with dual AV nodal physiology, simultaneous anterograde fast and slow pathway conduction resulting in an unusual form of nonreentrant AV nodal tachycardia has been observed. We describe the case of a young patient with an incessant form of complex supraventricular tachycardia who underwent electrophysiologic evaluation, which showed simultaneous conduction via multiple AV nodal pathways that caused a unique form of incessant nonreentrant AV nodal tachycardia. Radiofrequency ablation of the spatially closed intermediate and slow pathways effectively treated the tachycardia. The electrophysiologic determinants of simultaneous conduction through the multiple nodal pathways and the apparently different behavior of the fast pathway before and after ablation are discussed.     

Effects of upright posture on atrioventricular nodal reentry and dual atrioventricular nodal pathways

The electrophysiologic effects of upright posture (45 degrees upright tilt) were studied in 17 patients with dual atrioventricular (AV) nodal pathways, AV nodal reentry or both. Discontinuous AV nodal conduction curves were observed in 16 patients while supine, but in only 11 patients while upright. Fast pathway refractoriness was shortened: the anterograde fast pathway effective refractory period decreased from 360 +/- 22 to 275 +/- 14 ms (mean +/- standard error of the mean), the anterograde fast pathway block cycle length shortened from 448 +/- 28 to 348 +/- 20 ms and the retrograde fast pathway block cycle length shortened from 425 +/- 29 to 338 +/- 24 ms (all p less than 0.01). The anterograde slow pathway block cycle length shortened from 378 +/- 29 to 316 +/- 17 ms (p less than 0.05). AV nodal reentrant tachycardia was induced in 5 patients while supine (2 sustained, 3 nonsustained) and in 6 patients while upright (4 sustained, 2 nonsustained). Tachycardia cycle length shortened during upright posture, from 413 +/- 30 to 345 +/- 22 ms (p less than 0.01), primarily due to shortened anterograde slow pathway conduction time, from 322 +/- 23 to 268 +/- 20 ms (p less than 0.05). Upright posture thus enhances conduction in patients with dual AV nodal pathways, facilitating AV nodal reentry. Electrophysiologic testing in the upright position may yield additional clinical important information in patients with dual AV nodal pathways.     

Premature atrial complex with P'R prolongation indicates multiple atrioventricular nodal pathways.

BACKGROUND: The goal of the present study was to test if ambulatory Holter recordings can predict the electrophysiologic study (EPS) findings in patients with supraventricular tachycardia (SVT). METHODS AND RESULTS: The study involved 110 patients with SVT who underwent Holter recording, and then EPS. The hypotheses were that (1) a P'R interval of premature atrial complexes (PACs) between 280 and 400 ms in the Holter recordings predicted dual atrioventricular nodal (AVN) pathways, (2) P'R interval >400 ms predicted triple or more AVN pathways, and (3) SVT initiated by a single PAC suggested easy SVT induction during the EPS. The EPS revealed dual AVN pathways in 14 (93%) of 15 patients with P'R intervals between 280 and 400 ms on the Holter recordings, and triple or more AVN pathways in 18 (90%) of 20 patients with P'R intervals >400 ms. In addition, a single extrastimulus easily induced SVT during the EPS in 11 (85%) of 13 patients in whom SVT was initiated by a single PAC during Holter recording. CONCLUSION: The ambulatory Holter recording criteria specifically predicted the EPS findings, thereby providing useful advance information.     

'Uninterrupted' anterograde atrioventricular excitation conduction in patients with paroxysmal reciprocal atrioventricular nodal tachycardias

Different variants of anterograde atrioventricular conduction of excitation were distinguished basing on data obtained from 150 patients with paroxysmal reciprocal atrioventricular nodal tachycardias. Excitation conduction during programmed and accelerating atrial transesophageal pacing allowed to assess characteristics of excitation conduction along fast and slow conduction pathways in atrioventricular node. Some parameters were suggested that allowed to predict possibility of detection of different variants of anterograde atrioventricular conduction of excitation. Electrophysiological mechanisms of detection of various types of atrioventricular conduction curves are discussed.     

Neck pounding during sinus rhythm: a new clinical manifestation of dual atrioventricular nodal pathways

Objective—To determine the clinical and electrophysiological characteristics of patients with paroxysmal palpitations and neck pounding during sinus rhythm.
Methods—Clinical, electrocardiographic, and electrophysiological characteristics of six patients with paroxysmal palpitations and neck pounding during sinus rhythm were studied in basal conditions and when symptomatic. Response to treatment was observed.
Results—Baseline ECGs were normal (four patients) or had first degree atrioventricular block with intermittent PR shortening. During symptoms, narrow QRS rhythms were seen without visible P waves (three patients) or with P waves partially hidden in the QRS complex (three patients). Dual atrioventricular nodal pathways were found in all five patients who had electrophysiological studies. In these patients the slow pathway conduction time was long enough (mean (SD), 425 (121) ms) for ventricular activation after slow pathway conduction during sinus rhythm to coincide with the next atrial depolarisation, causing neck pounding during exercise (four patients) or at rest (two patients). Tachycardia was not induced in any patient. Medical treatment aggravated symptoms in three patients. A pacemaker was successfully used in two.
Conclusions—Neck pounding during sinus rhythm is a clinical manifestation of dual atrioventricular nodal pathways. Medical treatment may aggravate symptoms but a pacemaker may offer definitive relief.

Keywords: neck pounding;  nodal conduction;  palpitations     

Dual atrioventricular nodal pathways associated with a gap phenomenon in atrioventricular nodal conduction

A 67 year old man underwent electrophysiologic study for evaluation of syncope. During atrial pacing at a basic cycle length of 600 ms, atrial premature stimuli were introduced at progressively shorter coupling intervals. The graph of atrial coupling intervals versus corresponding His bundle responses revealed an abrupt increase in atrioventricular (AV) nodal conduction time with coupling intervals from 320 to 340 ms. In an atrial coupling interval of less than 320 ms, conduction was again rapid until the effective refractory period of the atrium was reached. These unique findings are compatible with dual pathways and a gap phenomenon within the AV node.     

Effects of ablation, digitalis, and beta-blocker on dual atrioventricular nodal pathways and conduction during atrial fibrillation

INTRODUCTION: Modification of AV nodal conduction by radiofrequency ablation (RFA) results in a variable reduction in heart rate during atrial fibrillation (AF). Using AF induced in patients with dual AV nodal pathways as a model, we tested the effect of additional treatment with digitalis (ouabain) and beta-blocker (esmolol). METHODS AND RESULTS: Ten patients were randomized to control (group I) and studied only before ablation. AF was induced in 30 patients before and after slow pathway ablation (group II). Mean ventricular cycle lengths (AF CLmean) were recorded. Slow pathway conduction was eliminated after ablation in 10 patients (group IIA), whereas slow pathway conduction was still present in 20 patients (group IIB). Compared to pre-RFA there was a 10% increase in AF CLmean post-RFA (P < 0.01). During isoproterenol infusion the increase was 8% (P = NS). Adding digitalis and beta-blocker during isoproterenol infusion increased AF CLmean by 75% (95% in group IIA) compared to 36% in group I (P < 0.001 II vs I). CONCLUSION: Slow pathway ablation reduces ventricular rate during AF. Addition of digitalis and beta-blocker during isoproterenol infusion significantly decreases ventricular rate after ablation compared to the control group. The finding suggests that beta-blocker has significant effects on fast AV nodal pathway conduction during induced AF with isoproterenol infusion.     

Multiple anterograde atrioventricular node pathways in patients with atrioventricular node reentrant tachycardia

Objectives. This study sought to investigate electrophysiologic characteristics and possible anatomic sites of multiple anterograde slow atrioventricular (AV) node pathways and to compare these findings with those in dual anterograde AV node pathways.Background. Although multiple anterograde AV node pathways have been demonstrated by the presence of multiple discontinuities in the AV node conduction curve, the role of these pathways in the initiation and maintenance of AV node reentrant tachycardia (AVNRT) is still unclear, and possible anatomic sites of these pathways have not been reported.Methods. This study included 500 consecutive patients with AVNRT who underwent electrophysiologic study and radiofrequency ablation. Twenty-six patients (5.2%) with triple or more anterograde AV node pathways were designated as Group I (16 female, 10 male, mean age 48 ± 14 years), and the other 474 patients (including 451 with and 23 without dual anterograde AV node pathways) were designated as Group II (257 female, 217 male; mean age 52 ± 16 years).Results. Of the 21 patients with triple anterograde AV node pathways, AVNRT was initiated through the first slow pathway only in 3, through the second slow pathway only in 8 and through the two slow pathways in 9. Of the five patients with quadruple anterograde AV node pathways, AVNRT was initiated through all three anterograde slow pathways in three and through the two slower pathways (the second and third slow pathways) in two. After radiofrequency catheter ablation, no patient had inducible AVNRT. Eleven patients (42.3%) in Group I had multiple anterograde slow pathways eliminated simulataneously at a single ablation site. Eight patients (30.7%) had these slow pathways eliminated at different ablation sites; the slow pathways with a longer conduction time were ablated more posteriorly in the Koch's triangle than those with a shorter conduction time. The remaining seven patients (27%) had a residual slow pathway after delivery of radiofrequency energy at a single or different ablation sites. The patients in Group I had a longer tachycardia cycle length, poorer retrograde conduction properties and a higher incidence of multiple types of AVNRT than those in Group II.Conclusions. Multiple anterograde AV node pathways are not rare in patients with AVNRT. However, not all of the anterograde slow pathways were involved in the initiation and maintenance of tachycardia. Radiofrequency catheter ablation was safe and effective in eliminating critical slow pathways to cure AVNRT.     

房室结双径路合并房室旁路的折返性心动过速及射频消融治疗

目的本研究旨在探讨房室结双径路（ＤＡＶＮＰ）合并房室旁路（ＡＰ）的电生理特征和射频消融要求。方法对２１８例阵发性室上性心动过速（ＰＳＶＴ）进行电生理检查，观察ＰＳＶＴ的前传和逆传途径，然后对ＡＰ或房室结慢径（ＳＰ）进行消融治疗。结果２１８例ＰＳＶＴ中检出ＤＡＶＮＰ＋ＡＰ１０例，检出率为４．６％。其中ＳＰ前传、ＡＰ逆传（ＳＰ－ＡＰ折返）４例，快径（ＦＰ）前传、ＡＰ逆传（ＦＰ－ＡＰ折返）１例，ＳＰ－ＡＰ折返并ＦＰ－ＡＰ折返或ＳＰ／ＦＰ交替前传折返４例，ＳＰ前传、ＦＰ逆传（ＡＰ旁观）１例。１０例患者均作ＡＰ消融，诱发房室结折返性心动过速（ＡＶＮＲＴ）的３例加作ＳＰ消融，术后随访均无复发。结论ＤＡＶＮＰ合并ＡＰ者ＡＰ均作为逆传途径，阻断ＡＰ是消融关键；ＡＰ旁观者也应作ＡＰ消融；仅有ＡＨ跳跃延长者不必接受房室结改良；ＡＰ消融者应作ＤＡＶＮＰ电生理检查。     

Demonstration of dual atrioventricular nodal pathways in man

Electrophysiologic studies in a patient manifesting two P-R intervals revealed two ranges of atrioventricular (A-V) nodal conduction time (A-H intervals) and two A-V nodal effective and functional refractory periods. Similar demonstrations in patients with paroxysmal supraventricular tachycardia would strongly support the presence of longitudinal A-V nodal dissociation with reentry as a causative mechanism.     

Atrioventricular nodal gap conduction as a manifestation of dual nodal pathways

Electrophysiologic studies were performed in a 76 year old patient for evaluation of sinus bradycardia. Atrial extrastimuli were induced during sinus rhythm at progressively decreasing coupling (A1-A2) intervals. At an A1-A2 interval of 420 msec, right bundle branch block developed, and at 370 msec conduction failed below the His bundle. When the interval was reduced to 320 msec, conduction resumed with a normal QRS pattern with an abrupt increase in A-H intervals from 165 to 305 msec. These findings are interpreted as type I or atrioventricular (A-V) nodal gap conduction physiologically related to conversion from a rapid to a slow A-V nodal conduction mode.     

经房室结双径路引起的1:2房室传导现象

患者男性，44岁，因反复胸闷、心悸两年余就诊。临床诊断，心律失常、阵发性室上性心动过速。心电图（图1）示，窦性心律，P波几乎均落在前一激动的T波上，有的在T波升支处，有的在T波顶峰，并与之重叠，PP间期略不规则，0．58--0．64s。QRS波呈室上性。时限为0．08S，PR间期0．18s及0．50s。心动过速发作时P波后跟随1～2个QRS波，PR1间期为0．18s，PR2间期为0．50s，R1与R2之间无逆行P波。[第一段]     

Quadruple atrioventricular nodal pathways: involved in orthodromic atrioventricular reentrant tachycardia

Supraventricular tachycardia can be caused by multiple atrioventricular nodal pathways or atrioventricular accessory pathways. Herein, we report the case of a patient who was diagnosed with an orthodromic atrioventricular reentrant tachycardia that was caused by an unusual combination of quadruple atrioventricular nodal pathways and an atrioventricular accessory pathway. Radiofrequency catheter ablation of the accessory pathway successfully eliminated the arrhythmias and the patient's symptoms. Careful analysis of complete electrophysiologic studies can help in the diagnosis of such rare clinical presentations.     

房室结双径路或多径路室房传导及其伴发的特殊心电现象

目的探讨房室结双径路或多径路室房传导及其伴发的特殊心电现象和发生机制。方法通过常规心电图对6例异位心搏中出现的房室结双径路或多径路室房传导现象进行回顾性分析。结果其特征为：①心室搏动后跟随P^-波，R—P^-间期有两种或两种以上，相邻两个R—P^-间期差值60ms。②起搏源性室房文氏现象中，R—P^-间期成倍增长，有时伴心室回波。③室性期前收缩后跟随两次P^-波。形成1：2室房同步传导。结论通过推理性分析可在体表心电图上作出房室结双径路或多径路室房传导的诊断。     

Linking phenomenon in dual atrioventricular nodal pathways.

The linking phenomenon is an electrophysiological phenomenon of conduction between 2 different pathways, such as bundle branches, atrioventricular node (AVN) and accessory pathways. The present study used electrophysiological studies to investigate this phenomenon in 14 patients with dual AVN pathways. Decremental ramp pacing at intervals of 10 ms was carried out in high right atrium until the atrio-His (A-H) interval was abruptly prolonged (onset), then subsequent incremental ramp pacing at intervals of 10 ms proceeded until the A-H interval abruptly shortened (offset). The linking window (LW) was defined as the difference between the paced cycle lengths of the offset and the onset. The linking phenomenon occurred in 9 patients (64%). The onset depended on the functional refractory period of the fast pathway and once the linking was established in the dual pathways, the LW was related to the difference between the A-H interval immediately before and after the restoration of anterograde fast pathway conduction. These findings suggest that the linking phenomenon in dual AVN pathways occurs because of anterograde conduction block in the fast pathway and the subsequent concealed retrograde conduction of impulses propagated from the slow pathway.     

Effect of concealed anterograde impulse penetration on retrograde atrioventricular nodal conduction in man

The manner in which concealed anterograde impulse penetration may affect retrograde atrioventricular nodal conduction was studied systematically in 12 patients with intact ventriculoatrial (VA) conduction. After the last beat of a basic atrial drive (A1), an extrastimulus (A2) was introduced 20 msec inside the effective refractory period of the atrioventricular node. A ventricular extrastimulus (Vp) was then introduced at a progressively shorter A1Vp coupling interval both in the presence (method I) and absence (method II) of A2. In two patients, Vp was never conducted retrogradely to the atria with method I despite the presence of VA conduction during method II. In the remaining 10 patients, the VpAp interval was longer with method I vs method II; moreover, retrograde block of Vp ultimately occurred at a mean A2Vp coupling interval of 359 +/- 153 msec (range 190 to 540 msec) during method I despite the persistence of VA conduction during method II at comparable A1Vp coupling intervals. Before onset of retrograde block in method I, the VpAp curve took one of the following three forms: (1) crescendo, a progressively increasing VpAp interval; (2) flat, a constant VpAp interval, (four cases); or (3) discontinuous, a marked jump in the VpAp interval before the onset of retrograde block (two cases). Our findings may serve to elucidate some poorly understood electrophysiologic phenomena.     

房室结双径路及有关问题的研究

本文对５３例各种不同类型的心律失常进行了食管电生理检查，共检出房室结双径路２０例。９例有室上性心动过速（ＰＳＶＴ）史，其中４例诱发出ＰＳＶＴ（２０％），并通过超速抑制终止其发作；９例有窦缓史，其中２例经食管电生理检查诊断为病窦。在此类患者中，发现房室结双径路，在国内尚未见报道。经统计学处理，ＰＳＶＴ与窦缓两者的电生理参数除后者窦房结恢复时间显著延长（Ｐ＜０．０１）外，余均无显著差异。作者认为房室结双经路的存在与窦房结功能是否正常无关，并提出房室结双径路与病窦共存的电生理现象。在２０例房室结双径路中还发现多经路５例（２５％），房室传导间隙６例（３０％）。