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.     

Atrial tachycardia, 2:1 alternate Wenckebach periodicity, and atrial standstill

A case of atrial tachycardia, 2:1 alternate Wenckebach periodicity and atrial standstill is reported in an 80-year-old woman who complained of exertional dyspnea and occasional syncope for two years. Two blocked P' waves appeared after each Wenckebach period suggesting type B alternating Wenckebach phenomenon (Mobitz type II 2:1 A-V block distal, and Wenckebach conduction proximal).     

Atrial pacing-induced alternating Wenckebach periodicity and multilevel conduction block in children

Multilevel block within the atrioventricular (AV) node has not been previously described in children. Six children with atrial pacing-induced repetitive block are presented. The conduction patterns satisfy the requisites for alternating Wenckebach periodicity or multilevel AV block. In 2 patients the block is documented in the AV node and infra-His region. In 4 patients multilevel block within the AV node is postulated by deductive reasoning. In this study, 2 patterns of alternating Wenckebach periodicity are reported for the first time: sequences of 3:1 block with progressive prolongation of the conducted impulses terminating in 4:1 block; and sequences of 2:1 block with progressive prolongation of the conducted impulses terminating in 2 series of 3:1 block, in which the first conducted impulse following the first 2 blocked beats is not the shortest one, whereas that following the second 2 blocked beats is the shortest.     

Alternating reversed wenckebach periodicity: Concealed electrotonic conduction as a possible mechanism

Electrocardiograms were taken from a 67-year-old man with 2:1 atrioventricular block in whom alternating reversed Wenckebach periodicity was found. Long PR intervals of alternately conducted P waves progressively shortened until an alternate P wave was blocked. After an alternate P wave was blocked, the next alternate P wave was conducted to the ventricles with a markedly long PR interval. Then long PR intervals of alternately conducted P waves progressively shortened again until an alternate P wave was blocked. This is the first report on alternating reversed Wenckebach periodicity. It seems that concealed electrotonic conduction of alternately blocked impulses occurred as a possible mechanism.     

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.     

Prediction of complex atrioventricular conduction rhythms in humans with use of the atrioventricular nodal recovery curve

Theoretical considerations indicate that complex patterns of atrioventricular conduction produced by rapid atrial stimulation can be predicted from changes in atrioventricular conduction produced by premature stimulation of the atrium. The purpose of this study was to evaluate the validity of this theoretical approach in seven patients undergoing electrophysiologic investigation. The atrioventricular nodal recovery curve was determined at two different basic cycle lengths. Subsequently, periodic atrial stimulation was delivered for 30 sec periods over a range of frequencies giving 11, Wenckebach, reverse Wenckebach, and 21 rhythms. The recovery curve data was then used to compute the response to periodic stimulation by an iterative technique. The conduction patterns actually seen during periodic atrial stimulation showed close agreement with the computed patterns. This work thus provides a unified explanation for the appearance of Wenckebach, reverse Wenckebach, alternating Wenckebach, and high grade block rhythms.     

A new method for evaluating the effect of antiarrhythmic drugs on atrioventricular nodal conduction

Electrophysiological variables were studied in 19 patients before and after one of three commonly used antiarrhythmic agents. The pacing rate at which alternating Wenckebach periods appeared in eight patients was significantly reduced by intravenous digoxin (0.01 mg/kg body weight). The atrioventricular nodal conduction time (A-H interval) and Wenckebach point were not significantly altered by digoxin. Intravenous propranolol (0.1 mg/kg body weight) in four patients did not affect the A-H interval, but it reduced the pacing rates at which the Wenckebach point and alternating Wenckebach periods occurred. Intravenous disopyramide (2 mg/kg body weight) significantly increased the pacing rate required to produce alternating Wenckebach periods but did not significantly alter the other indicators of atrioventricular conduction in seven patients. It is concluded that the pacing rate required to produce alternating Wenckebach periodicity may be a useful and sensitive variable in the evaluation of the effect of antiarrhythmic agents on atrioventricular nodal conduction.     

A new method for evaluating the effect of antiarrhythmic drugs on atrioventricular nodal conduction.

Electrophysiological variables were studied in 19 patients before and after one of three commonly used antiarrhythmic agents. The pacing rate at which alternating Wenckebach periods appeared in eight patients was significantly reduced by intravenous digoxin (0.01 mg/kg body weight). The atrioventricular nodal conduction time (A-H interval) and Wenckebach point were not significantly altered by digoxin. Intravenous propranolol (0.1 mg/kg body weight) in four patients did not affect the A-H interval, but it reduced the pacing rates at which the Wenckebach point and alternating Wenckebach periods occurred. Intravenous disopyramide (2 mg/kg body weight) significantly increased the pacing rate required to produce alternating Wenckebach periods but did not significantly alter the other indicators of atrioventricular conduction in seven patients. It is concluded that the pacing rate required to produce alternating Wenckebach periodicity may be a useful and sensitive variable in the evaluation of the effect of antiarrhythmic agents on atrioventricular nodal conduction.     

Type A alternating Wenckebach periodicity in the re-entrant path of ventricular extrasystoles

A patient with ventricular extrasystoles is reported in whom Type A alternating Wenckebach periodicity in the re-entrant path of the extrasystoles is suggested for the first time. Namely, it appears that 2:1 exit block occurs at a proximal level in the re-entrant path and block of the Wenckebach form occurs at a distal level in the path. The presence of three-level block in the re-entrant path is also suggested in this patient.     

Permanent form of junctional reciprocating tachycardia with only even-numbered beats

An analysis of the electrocardiogram of a patient with the permanent form of junctional reciprocating tachycardia is presented. The patient demonstrated near-incessant tachycardia, with a 1:1 atrioventricular relationship and a retrograde P wave (P') occurring closer to the succeeding QRS complexes (ie, with a P'R interval that is shorter than the RP' interval). Each tachycardia episode was characterized by alternating short and long cardiac cycles due to alternation of retrograde conduction time (RP' interval), retrograde Wenckebach periodicity, and an even number of ectopic P' waves. The authors propose that there is an accessory AV connection with decremental functional properties that arborizes into two atrial branches with different conduction times. The fast branch initially exhibits a 3:2 retrograde conduction block followed by a cycle length-dependent 2:1 retrograde conduction block, thereby permitting alternate use of the slow branch, which is the weakest component of the reciprocating process.     

Type A alternating Wenckebach periodicity in the reentrant pathway of interpolated ventricular extrasystoles

A 67-year-old man with interpolated ventricular extrasystoles is reported in whom alternate sinus QRS complexes were followed by interpolated ventricular extrasystoles with progressively lengthening coupling intervals until one of these alternate sinus complexes failed to be followed by an extrasystole. This is the first report to suggest the presence of type A alternating Wenckebach periodicity in the reentrant pathway of interpolated ventricular extrasystoles. It is suggested that 2:1 block occurred at a proximal level in the reentrant pathway, while Wenckebach block occurred at a distal level in the pathway.     

Paroxysmal Mobitz type-I atrioventricular block Luciani-Wenckebach conduction, acute myocardial infarction and severe three vessels coronary artery disease

Paroxysmal atrioventricular block has been reported in patients without acute coronary syndrome and without significant coronary artery stenosis, in patients with acute coronary syndrome and without significant coronary artery stenosis, in patients without acute coronary syndrome and with significant coronary artery stenosis and in patients with acute coronary syndrome and significant coronary artery stenosis. Conflicting roles for alternating periods of second degree atrioventricular block (also known as Mobitz I or Luciani-Wenckebach periodicity) have been reported. Both hypotheses have been reported, that paroxysmal Wenckebach periods are compatible with a benign prognosis and that paroxysmal Wenckebach periods are associated with hemodynamic deterioration. We present a case of paroxysmal Mobitz Type-I atrioventricular block Luciani-Wenckebach conduction in a 75-year-old Italian man with acute myocardial infarction and severe three vessels coronary artery disease.     

Multilevel block in the atrioventricular node during atrial tachycardia and flutter alternating with Wenckebach phenomenon

The electrocardiograms of 100 patients with rapid and regular PP intervals during atrial arrhythmias (because of atrial tachycardia or flutter, or pacing) were examined for periods of irregular atrioventricular conduction. This irregular conduction corresponds to an alternating Wenckebach phenomenon, of a type that can be determined from simple rules. The different types of conduction encountered in different patients and the changes seen in the same patient suggest that the atrioventricular node functions physiologically with 3 levels of sequential block. The different prevalence of the 2 types of alternating Wenckebach block may reflect functional differences at the level of the atrioventricular node.     

Multilevel block in the atrioventricular node during atrial tachycardia and flutter alternating with Wenckebach phenomenon.

The electrocardiograms of 100 patients with rapid and regular PP intervals during atrial arrhythmias (because of atrial tachycardia or flutter, or pacing) were examined for periods of irregular atrioventricular conduction. This irregular conduction corresponds to an alternating Wenckebach phenomenon, of a type that can be determined from simple rules. The different types of conduction encountered in different patients and the changes seen in the same patient suggest that the atrioventricular node functions physiologically with 3 levels of sequential block. The different prevalence of the 2 types of alternating Wenckebach block may reflect functional differences at the level of the atrioventricular node.     

AV nodal dual pathway electrophysiology and Wenckebach periodicity

Dual Pathways and Wenckebach Periodicity. Introduction: The precise mechanism(s) governing the phenomenon of AV nodal Wenckebach periodicity is not fully elucidated. Currently 2 hypotheses, the decremental conduction and the Rosenbluethian step‐delay, are most frequently used. We have provided new evidence that, in addition, dual pathway (DPW) electrophysiology is directly involved in the manifestation of AV nodal Wenckebach phenomenon. Methods and Results: AV nodal cellular action potentials (APs) were recorded from 6 rabbit AV node preparations during standard A1A2 and incremental pacing protocols. His electrogram alternans, a validated index of DPW electrophysiology, was used to monitor fast (FP) and slow (SP) pathway conduction. The data were collected in intact AV nodes, as well as after SP ablation. In all studied hearts the Wenckebach cycle started with FP propagation, followed by transition to SP until its ultimate block. During this process complex cellular APs were observed, with decremental foot formations reflecting the fading FP and second depolarizations produced by the SP. In addition, the AV node cells exhibited a progressive loss in maximal diastolic membrane potential (MDP) due to incomplete repolarization. The pause created with the blocked Wenckebach beat was associated with restoration of MDP and reinitiation of the conduction cycle via the FP wavefront. Conclusion: DPW electrophysiology is dynamically involved in the development of AV nodal Wenckebach periodicity. In the intact AV node, the cycle starts with FP that is progressively weakened and then replaced by SP propagation, until block occurs. AV nodal SP modification did not eliminate Wenckebach periodicity but strongly affected its paradigm. (J Cardiovasc Electrophysiol, Vol. pp.1‐7)     

Paradoxical Shortening of the Second PR Interval During 3:2 Atrioventricular Nodal Block

Paradoxical Shortening in Second-Degree AV Block. A patient with 3:2 second-degree AV block after acute inferior wall myocardial infarction showed consistent PR interval shortening on the second conducted beat in each periodicity. Intracardiac electrophysiologic evaluation revealed that the site of block was nodal. A typical Wenckebach pattern with prolongation of the AH interval was noted. The shorter PR resulted from a paradoxical shortening of the HV interval in the second beat, most likely due to supernormal conduction in the setting of concomitant trifascicular disease.     

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.     

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.     

Analysis of Luciani-Wenckebach periodism in A-V node. I. Typical features (author's transl)

Electrocardiograms of 20 patients developing Wenckebach A-V block duting atrial pacing and 20 with spontaneous Wenckebach block were reviewed to determine the frequency of typical features of classical Wenckebach periodicity. Few cases only met all six typical criteria. Cases with long cycles with conduction ratios of 5/4, with Wenchkebach point less than 130 min, and with first greater than A-H 110 msec were the most likely to show typical features. The implications of these observations are discussed on the basis of modern hypothesis of electrophysiological mechanisms of Wenckebach periodism.