Atypical Wenckebach periodicity simulating Mobitz II AV block.

Eleven patients were studied and a total of 144 Wenckebach cycles in the AV node and 118 Wenckebach cycles in the His-Purkinje system were analysed to determine the incidence of typical and atypical Wenckebach periodicity, with particular emphasis on one variant of atypical Wenckebach that may simulate a Mobitz type II block. This pseudo-Mobitz II pattern was defined as a long Wenckebach cycle in which, at least, the last three beats of the cycle show relatively constant PR intervals (variation of no more than 0.02 s in surface leads and no more than 10 ms in His bundle electrograms) and in which the PR interval immediately following the blocked beat is shorter than the PR interval before the block by 0.04 s or more. Atypical Wenckebach cycles were found to be more common than the typical variety at both the AV node (67%) and His-Purkinje system (69%). The pseudo-Mobitz II pattern was seen in 19 per cent of atypical AV nodal Wenckebach periods and in 17 per cent of atypical His-Purkinje system Wenckebach cycles. The need to discern a ''classical'' Mobitz II block from a pseudo-Mobitz II pattern, especially in the setting of an acute inferior myocardial infarction, is emphasised.     

An analysis of Wenckebach periodicity

His bundle electrograms of 40 patients developing Wenckebach block during atrial pacing and four with spontaneous Wenckebach block above the His were reviewed to determine the frequency of classical Wenckebach periodicity. Thirty patients had 143 Wenckebach cycles that were suitable for analysis. Cycles were evaluated for the following features: 1) the first A-H interval as the shortest, 2) the first R-R interval as the longest, 3) the last R-R interval as the shortest, 4) a progressive diminution of the increment of A-H interval prolongation, 5) a progressive diminution of the R-R interval and 6) the R-R interval containing the nonconducted A wave being equal to twice the A-A interval less the sum of the increments of A-H prolongation. Wenckebach cycles that occurred during atrial pacing were not significantly different from those that occurred spontaneously. Fifteen per cent of all cycles met all six criteria- 14% had five, 6% had four; 17% had three; 20% had two; 27% had one; and 1% had none. Short cycles were the most likely to show typical Wenckebach periodicity: 56% of the cycles with conduction ratios of 4:3, 28% with 5:4 and 4% with 6:5 met at least five criteria, whereas none of the 22 cycles having ratios 7:6 or greater had more than three features. The first A-H interval as the shortest was the most common feature occurring in 98% of cycles, whereas the features of a progressive diminution of the increments of the A-H interval prolongation or the progressive diminution of the R-R interval were the least common, occurring in 35% of cycles. These findings indicate, therefore, that classical Wenckebach periodicity is uncommon, especially when conduction ratios are 5:4 or greater. The implications of these observations and the suggested mechanisms are discussed and literature reviewed.     

Alternating Wenckebach periodicity: A common electrophysiologic response.

Alternating Wenckebach periods are defined as episodes of 2:1 atrioventricular (A-V) block in which conducted P-R intervals progressively prolong, terminating in two or three blocked P waves. In this study, His bundle recordings were obtained in 13 patients with pacing-induced alternating Wenckebach periods. Three patterns were noted: Pattern 1 (one patient with a narrow QRS complex) was characterized by 2:1 block distal to the H deflection (block in the His bundle) and Wenckebach periods proximal to the H deflection, terminating with two blocked P waves. Pattern 2 (four patients) was characterized by alternating Wenckebach periods proximal to the His bundle, terminating with three blocked P waves. Pattern 3 (eight patients) was characterized by alternating Wenckebach periods proximal to the His bundle, terminating with two blocked P waves. Alternating Wenckebach periods are best explained by postulating two levels of block. When alternating Wenckebach periods are terminated by three blocked P waves (pattern 2), the condition may be explained by postulating 2:1 block (proximal level) and type I block (distal level). When alternating Wenckebach periods are terminated by two blocked P waves (patterns 1 and 3), the condition may be explained by postulating type I block (proximal level) and 2:1 block (distal level). Pattern 1 reflects block at two levels, the A-V node and His bundle. Patterns 2 and 3 most likely reflect horizontal dissociation within the A-V node.     

A generalized description of Wenckebach behavior with analysis of determinants of ventricular cycle-length variation during ambulatory electrocardiography

Although variation in ventricular cycle length during Wenckebach-type second-degree atrioventricular block traditionally has been explained by the direction of incremental change in PR lengthening preceding the blocked complex, changing PP intervals can also affect Wenckebach periodicity. A generalized algebraic solution was derived to define changing ventricular cycle length as a function of both changing PP and changing incremental PR interval behavior in Wenckebach block. Based on this solution, the determinants of cycle-length variation were examined for 65 episodes of Wenckebach block detected by ambulatory electrocardiography in 51 patients. As previously demonstrated, only 20% (13 of 65) of Wenckebach episodes were characterized by the "classic" shortening of RR intervals; in contrast, ventricular cycle length increased in 57% (37 of 65) and remained constant in 23% (15 of 65) of cases. Algebraic analysis of these episodes revealed that the direction of ventricular cycle-length change preceding the blocked complex was primarily determined by the direction of change of incremental PR intervals in only 35% (23 of 65) of Wenckebach episodes; RR change was governed by the direction of change of preceding PP intervals in 34% (22 of 65) and by equal change of PP and incremental PR intervals in 31% (20 of 65) of these episodes. Both inverse and concordant relationships between changing RP and PR intervals were primarily determined by the direction of PP variation during in vivo Wenckebach block. These data confirm that classic Wenckebach block is less common than "atypical" Wenckebach periodicity and demonstrate that RR variation in Wenckebach block is governed by the changing PP interval as often as by the changing incremental PR interval.     

Mechanisms and dynamics of episodes of progression of 2:1 atrioventricular block in patients with documented two-level conduction disturbances.

Twenty episodes of progression of 2:1 atrioventricular (AV) block were identified during incremental atrial stimulation in 7 patients with documented (2-level) block in the AV node and His-Purkinje system. All occurred at cycle lengths shorter than those at which stable 2:1 HV block had been detected. Thirteen episodes were typical since 2:1 increased to 3:1 AV block when an atrio-His (AH) Wenckebach period was completed with an atrial impulse that otherwise would have been conducted. These episodes occurred with dynamic A(M): V(N) ratios similar to those seen at the AV node. Seven atypical episodes were identified (while AH Wenckebach periods were occurring): (1) 2:1 increasing to 3:1 AV block and then to 4:1 AV block resulting from prolonged refractoriness in the His-Purkinje system subsequently followed by concealed conduction in the latter structure; (2) conversion of 3:2 directly into 3:1 AV block due to block of the next-to-last atrial impulse in the His-Purkinje system with completion of AH Wenckebach period with the following atrial impulse; and (3) 4:2 AV block presumably due to supernormal conduction in a transversely dissociated His-Purkinje system. These episodes occurred with A(M): V(N) ratios, which in other structures would have been indicative of different degrees of AV block. In conclusion, progression of 2:1 AV block during documented 2 level conduction disturbances (1) can be explained by mechanisms different than those currently known, and (2) has rich, but different dynamics from those observed exclusively in the AV node and exclusively in the His-Purkinje system.     

Evaluation of five computer programs in the diagnosis of second-degree AV block.

Five electrocardiogram (ECG) analyzing systems were tested with a microcomputer-based ECG signal generator to assess the accuracy of the systems in interpreting Wenckebach periodicity. Although normal sinus rhythm with normal PR intervals and sinus rhythms with first-degree atrioventricular (AV) block were diagnosed by all five systems, second-degree AV block with classic Wenckebach periodicity was routinely misdiagnosed by four of the five systems. No system recognized the atypical Wenckebach periods in a total of 200 trials, misinterpreting the phenomenon as atrial fibrillation, supraventricular rhythm, sinoatrial block, and other rhythm disturbances. In advanced AV block and a variety of ventricular arrhythmias, none of the five systems diagnosed second-degree AV block with Wenckebach periods. Marked unsatisfactory performance with regard to the diagnosis of Wenckebach periodicity indicates the urgent need for accelerated and comprehensive testing of ECG diagnostic equipment. The present generating device was seen as an effective troubleshooter in optimizing the diagnostic competency of computerized ECG systems.     

Wenckebach second-degree A-V block in top-ranking athletes: an old problem revisited

The occurrence of Wenckebach second-degree (Mobitz I) A-V block in apparently normal persons still provides a puzzle for the cardiologist, as the benign nature of this event has been recently questioned. This problem becomes more intriguing when Wenckebach A-V block is encountered in asymptomatic top-ranking athletes, because of medico-legal implications. We report 10 cases of highly-trained athletes, including three with mitral valve prolapse (MVP) features, with a spontaneous or induced Wenckebach seconddegree A-V block.Previous ECGs of six subjects, dating from a maximum of 6 years to a minimum of 18 months, were available. Deterioration of A-V conduction has never been documented and all six cases have remained asymptomatic for the whole follow-up period.Athletes have been submitted to a protocol study consisting of ECG recording at rest, during, and after vagal and sympathetic reflex maneuvers, drug administration (isoproterenol and atropine), submaximal and maximal exercise.Nine subjects have been considered to have “normal” responses of the A-V node to provocative tests, since conduction disturbances were improved or normalized by reflex sympathetic stimulations and were completely normalized by autonomic drug administration and exercise.One athlete showed “abnormal” responses to tests. In order to give a conclusive prognostic and medico-legal assessment, we advised him to submit to an invasive electrophysiological investigation.Wenckebach second-degree A-V block in athletes may be a more common finding than so far described, especially when a systematic search is made. In our opinion, this event can still be considered a vagally-induced benign feature of athlete's heart, provided that an immediate improvement of A-V conduction is obtained in response to reflex sympathetic maneuvers, and that a complete normalization after sympathomimetic and vagolytic drug administration and physical exercise is observed.The clinical histories of our athletes and the observed complete disappearance of conduction disturbances after detraining, strongly support this opinion.Wenckebach second-degree A-V block in asymptomatic athletes with MVP features probably does not affect the prognosis if similar favorable responses to the aforesaid tests are observed.     

Alternating Wenckebach periods with acute myocardial infarction. Report of two cases.

This report describes two patients with the spontaneous occurrence of alternating Wenckebach periods during the course of acute myocardial infarction. Both patients demonstrated alternating Wenckebach periods which terminated in a sequence of two blocked P waves. In one patient, His bundle electrocardiographic study documented the site of block to be proximal to the His bundle. Alternating Wenckebach periods with the block proximal to the His bundle may be compatible with a benign prognosis.     

Concealed intraventricular conduction in the His bundle electrogram.

Multiple areas of concealed intraventricular conduction are deduced on the basis of aftereffects observed in His bundle recordings. Electrocardiograms and His bundle recordings are presented from two patients with unstable bilateral bundle branch block, the instability of which depended on the interval at which ventricular depolarization was initiated by sinus or paced impulses. This circumstance allows postulation of 1) concealed transseptal retrograde penetration of the left bundle branch system; 2) concealed transseptal retrograde penetration of the right bundle branch system; 3) alternate beat Wenckebach phenomenon with two areas of block in the bundle branch system with concealed penetration of the proximal area; 4) concealed re-entry in the right bundle branch system during an H-V Wenckebach cycle with resetting of the sequence of 2:1 H-V block and return of the re-entry wave to the A-V node causing subsequent A-H block; 5) proximal 2:1 block and distal Wenckebach block producing only two consecutively blocked beats; and 6) infrahisian Wenckebach block with changes both in A-V conduction and QRS contour.     

Wenckebach phenomenon occurring in the distal conducting system in a young adult.

This report describes the case of a young man who presented with right bundle-branch block and second degree atrioventricular block; intermittent episodes of Wenckebach periods were recorded. His bundle electrograms demonstrated progressive prolongation of the HV interval followed by block occurring distal to His. This report emphasizes the fact that the Wenckebach phenomenon as a manifestation of the distal conducting system disease can occur in young adults. The observations lend credence to the concept that Lenègre's disease can occur in young people.     

Wenckebach phenomenon occurring in the distal conducting system in a young adult.

This report describes the case of a young man who presented with right bundle-branch block and second degree atrioventricular block; intermittent episodes of Wenckebach periods were recorded. His bundle electrograms demonstrated progressive prolongation of the HV interval followed by block occurring distal to His. This report emphasizes the fact that the Wenckebach phenomenon as a manifestation of the distal conducting system disease can occur in young adults. The observations lend credence to the concept that Lenègre's disease can occur in young people.     

Luigi Luciani and the earliest graphic demonstration of Wenckebach periodicity

Using an isolated frog heart preparation with ligatures around the atria, Luigi Luciani, an Italian physiologist working in 1873 in Carl Ludwig's famous laboratory in Leipzig, was the first to demonstrate cardiac group beating, which he named periodic rhythm. He attributed this to increased resistance to impulse propagation between the atria and the ventricle. Karel F. Wenckebach, in his 1899 landmark report of group beating in a patient in which he also used pulse tracings, credited Luciani with this discovery. Wenckebach referred to the phenomena as "Luciani periods." With the advent of electrocardiography in the early 20th century, this form of group beating became known as Wenckebach periodicity and then as Mobitz type I atrioventricular block. We reanalyzed Luciani's original paper and pulse tracings, and we show that periodic rhythm does indeed meet the criteria of second-degree atrioventricular block as established by Wenckebach. We also reviewed the career of Luciani, who was an important investigator, outstanding teacher and mentor, and distinguished leader of 19th-century physiology. We conclude that Wenckebach still deserves to have his name eponymously attached to this type of atrioventricular block because he was the first to unravel the complicated relationship between atrial and ventricular conduction.     

Effects of proximal intra-atrial Wenckebach on distal atrioventricular nodal, and His-Purkinje, block with special reference to the theory of alternating Wenckebach periods

Intra-atrial Wenckebach patterns of stimulus-to-response intervals coexisting with distal, A-V nodal, and His-Purkinje, blocks occurred in eight patients during high right atrial stimulation at rapid rates. In two patients with 2:1 St-H block and in two patients with 4:1 St-V block, an increase in the degree of block occurred when the proximal intra-atrial Wenckebach cycle was completed with the stimulus which otherwise would have been propagated to the distal levels. However, the degree of block did not increase when the intra-atrial Wenckebach terminated in distally blocked stimuli. In one patient progression of 4:1 into 5:1 St-V block was due to the association of intra-atrial Wenckebach with alternating 2:1 block at the A-V nodal, and His-Purkinje, levels. Contrasting with most reports dealing with the mechanisms of alternating Wenckebach in a single structure, this study permitted the determination of the boundaries between proximal and more distal levels. It also showed that alternating Wenckebach cycles (of St-H intervals) ending with two consecutively blocked stimuli could result from the association of proximal intra-atrial Wenckebach with distal, A-V nodal Wenckebach, or abortive AW, cycles. The electrophysiology of documented two, or three, level block in different structures has validated previously made assumptions regarding multilevel block in a single structure.     

Dissociation of the atrioventricular node in acute inferior wall myocardial infarction. 1. Transverse dissociation (alternate Wenckebach periods)

Two cases of alternate Wenckebach periods developing during the acute phase of inferior wall myocardial infarction are presented. In both cases, syncope occurred and severe bradyarrhythmia was recorded on the day of admission. Electrophysiologic study performed in one patient and a narrow QRS complex in the other patient during the alternate Wenckebach periods confirmed the atrioventricular node as the level of block. Transverse dissociation of the atrioventricular node with two (or more) levels of block is the most acceptable explanation for this phenomenon. We suggest that alternate Wenckebach periods occurring during the acute phase of inferior wall myocardial infarction is a severe bradyarrhythmia, and prophylactic temporary pacing is recommended.     

Atrioventricular alternating Wenckebach periodicity: conduction patterns in multilevel block

Atrioventricular (A-V) conduction patterns were analyzed in three patients with atrial pacing-induced alternating Wenckebach periodicity. These cases were unique because in each (1) separate levels of block responsible for the conduction disturbance were located above and below the His bundle recording site, and (2) there were several departures from the simple alternating Wenckebach pattern. Apparent supernormal conduction, temporary 1:1 conduction and a specific form of gap in A-V conduction resulted from the interplay of many factors including a simple mathematic relation of the blocking ratio at the two levels, the characteristics of the Wenckebach cycles, and the cycle length-dependent features of refractory periods at the different sites. The findings indicate that (1) delay in proximal impulse transmission is usually the critical factor in overcoming prolonged distal refractoriness and producing variable conduction patterns during the course of alternating Wenckebach periodicity; (2) many irregularities in alternating Wenckebach periodicity can be explained by known electrophysiologic mechanisms; and (3) simple mathematic equations alone are too rigid to reflect properly the dynamic process underlying this conduction disturbance.     

心房扑动伴交替性文氏现象的心电图与临床分析

目的：探讨心房扑动伴交替性文氏现象的心电图特点与临床意义。方法回顾性分析13例心房扑动伴交替性文氏现象患者的临床资料。根据心电图表现,将这13例患者分为 A、B 两型。结果13例患者中10例患器质性心脏病,3例为非器质性心脏病患者。10例器质性心脏病患者中有7例经胺碘酮或普罗帕酮复律转为窦性心律时,仍存在一度房室阻滞或二度Ⅰ型房室阻滞,提示此7例交替性文氏现象多为病理性阻滞;3例非器质性心脏病患者中有2例（肺炎、创伤性颅脑损伤）恢复窦性心律未见房室阻滞,提示为功能性阻滞。所有患者均获临床治愈或好转出院。结论心房扑动伴交替性文氏现象为房室结双层阻滞,B 型略多于 A 型。该现象如果见于器质性心脏病患者,恢复窦性心律多数存在房室阻滞,提示可能为病理性阻滞。如果为病理性阻滞,应用抗心律失常药物时应适当减量,以免发生高度或三度房室阻滞。     

Extra AV nodal Wenckebach periodicity

Extra AV nodal Wenckebach periodicity was diagnosed in seven patients. The most frequent form of this conduction abnormality was an exit block. The underlying block was localized in the sinoatrial junction and in the atria in two patients; the AV junction and the ventricle were the site of the Wenckebach periodicity in one case each. In extra AV nodal exit block, the actual conduction delay is not seen on the ECG and the diagnosis is based on the progressive shortening of the P-P or R-R intervals followed by a pause which is less than twice the shortest P-P (R-R) interval depending on the level of the block. A Wenckebach periodicity in the bundle branches or within the reentry pathway each occurred in one patient. In these forms of Wenckebach periodicity, the diagnosis is established more readily because the conduction delay can be demonstrated on the surface ECG. The clinical significance of extra AV nodal Wenckebach periodicity is discussed.     

Clinical significance of junctional pacemaker automaticity in patients with sick sinus syndrome.

This study aimed to examine the characteristics and the clinical significance of atrio-ventricular (AV) junctional automaticity in sick sinus syndrome. Maximum sinus node recovery time (max SRT) or maximum junctional recovery time (max JRT), and AV nodal Wenckebach block rate were evaluated before and after pharmacologic autonomic blockade (AB) in 43 patients with sick sinus syndrome. Max JRT shorter than 3000 msec was obtained after AB in 13 patients (group 1) and apparent enhancement of junctional automaticity after AB was observed in these patients. Thirty patients showed max JRT or max SRT longer than 3000 msec after AB (group 2). The Wenckebach block rate increased significantly after AB in group 1 but did not change significantly in group 2. The Wenckebach block rate after AB in group 1 was significantly higher than that in group 2. Max JRT was obtained only after AB in 8 patients in group 1 (subgroup 1), and in 9 in group 2 (subgroup 2). Max SRT before AB and the intrinsic heart rate were not significantly different between these subgroups. Only one of 8 patients in subgroup 1 had a history of near syncope. On the other hand, syncope was observed in 5 patients, and near syncope in one, in group 2. In conclusion, intrinsic junctional automaticity is preserved in some patients with sick sinus syndrome, and might compensate for sinus node dysfunction to prevent clinical symptoms. Organic impairment should affect conductivity as well as automaticity in the AV junction.     

Double Wenckebach phenomenon in atrioventricular node and His bundle. Electrophysiological demonstration in a case of atrial flutter.

In a case of atrial flutter with a 9:2 atrioventricular response, the only possible way to explain the conduction pattern was 3:1 block in the atrioventicular node (which is 3:2 Wenckebach sequence in the N zone and a 2:1 block at the junction of the node with the bundle of His) plus 3:2 Wenckebach sequence distal to the H deflection. The recording of the His bundle deflection confirmed this analysis.     

Atrioventricular block at nodal and infrahissian level during atrial tachycardia. Apropos of a case]

The authors report the case of a patient with atrial tachycardia and surface electrocardiographic signs of left anterior hemiblock and complete right bundle branch block with 10/3 atrioventricular block. The regularity of the RR intervals which were an exact multiple of the atrial cycle suggested the absence of a Wenckebach phenomenon. The sequence of atrioventricular conduction cannot be explained by classical models of intranodal conduction. Endocavitary recordings confirmed this hypothesis. They showed block at 2 levels: supra- and infrahisian. The suprahisian block functioned in the 2/1 mode and the infrahisian block in the 5/3 mode without incremental conduction distal to the His potential before the apparition of block. A double zone of intrahisian block could explain the observed sequence of atrioventricular conduction. The absence of Wenckebach phenomenon on the surface ECG during tachycardia could be a sign of infrahisian block. The authors suggest that the association of this sequence of atrioventricular conduction with intraventricular conduction defects is a formal indication for electrophysiological studies.