The Wenckebach Phenomenon

Medicine has many great pioneers, and in 1899, one such pioneer - Karel Frederik Wenckebach made a discovery which, even to this day, remains one of the fundamental concepts within electrophysiology.Since the Wenckebach Phenomenon was first described, the field of electrophysiology has developed at a rapid pace, allowing us to observe this behaviour, and its complexities, in many new ways. In a similar way, this chapter will illustrate Wenckebach behaviour across a spectrum of modalities from the 12 lead ECG, through to the intra-cardiac recordings from both electrophysiological studies and implantable cardiac devices. In doing so, we continue to shed light on the phe-nomenon first identified through Wenckebach’s meticulous attention to detail some 120 years ago.     

Apparent bradycardia-dependent right bundle branch block associated with atypical atrioventricular Wenckebach periodicity as a possible mechanism

The Holter monitor electrocardiogram was taken from a 15-year-old male athlete. Intermittent right bundle branch block frequently occurred at rest. When sinus cycles gradually lengthened, sinus impulses were conducted to the ventricles with right bundle branch block (RBBB) in succession. When, thereafter, sinus cycles gradually shortened, sinus impulses were conducted without RBBB. However, it seems that these findings do not show true bradycardia-dependent RBBB. Atypical atrioventricular Wenckebach periodicity was occasionally found in which sudden shift from the period of comparatively short PR intervals to the period of long PR intervals occurred. In the Wenckebach periodicity, when a QRS complex occurs after a much longer pause, RBBB was not found, while when it occurs after a much shorter period, RBBB was found. This suggests that this case may be apparent bradycardia-dependent RBBB, namely, a form of tachycardia-dependent RBBB. This is the first report suggesting apparent bradycardia-dependent bundle branch block associated with gradual lengthening of sinus cycles, as a possible mechanism.     

Demonstration of a His-Purkinje Fatigue Phenomenon with Programmed Stimulation of the Right Ventricular Outflow Tract

This report describes the development of atrioventricular block by programmed stimulation of the right ventricular (RV) outflow tract in a patient with undiagnosed syncope. Burst pacing from the RV apex and outflow tract and programmed stimulation from the RV apex were unsuccessful. The observations were consistent with the fatigue phenomenon of the His-Purkinje system and illustrate the importance of an appropriate stimulation protocol in the electrophysiological evaluation of syncope.     

The morphology of the atrioventricular node in scleroderma -- a three-dimensional reconstruction

A new technique for looking at the atrioventricular node andbundle is described and applied to the conducting system insix patients with scleroderma. The conducting system blockswere removed, sectioned, appropriately stained and photographed.Outlines of the atrioventricular node and bundle were generatedand digitized. From the digital information three-dimensionalimages were generated and the atrioventricular node and bundlewere rotated so that the shape could be studied from any view.In striking contrast to normal atrioventricular nodal reconstructions,those from the patients who had scleroderma showed a narrowand flattened proximal atrioventricular node. The nodal microscopy,on the other hand, did not differ significantly in architecture.It is postulated that the alterations by fibrous replacementof the proximal node could account for the relatively high frequencyof atrioventricular conduction Scleroderma, problems in patientswith scleroderma and could paradoxically account for the relativelyfrequent occurrence of supraventricular tachycardias that arealso found in this disease.     

Permanent left bundle branch area pacing in a child with a third‐degree atrioventricular block: A case report

Permanent left bundle branch area pacing (LBBP) is a promising physiological pacing technique that has emerged in recent years. However, LBBP is almost exclusively clinically applied in adult patients. The feasibility and safety of the use of LBBP in children have not been well‐assessed. Here, we report the case of a 6‐year‐old child with a third‐degree atrioventricular block after surgical aortic valve replacement who successfully received a permanent LBBP.     

三度房室阻滞误诊原因分析

目的通过对既往诊断为三度房室阻滞的心电图资料的再分析,阐述三度房室阻滞的完整诊断标准及其原理。方法回顾性研究3家医院218例诊断为三度房室阻滞的心电图资料,统一以房室分离且满足:①RR间期>2倍的PP间期;②心室率<50bpm;③心房率<135bpm的诊断标准进行再诊断。结果经正确性评定原诊断正确者197例(90.4%),误诊者12例(5.5%),不确定者9例(4.1%)。误诊的12例心电图中,7例为二度2:1房室阻滞合并干扰性房室脱节,4例为高度房室阻滞合并干扰性房室脱节,1例为加速性交界区自主心律合并干扰性房室脱节。结论以“房室分离且房率快于室率”作为三度房室阻滞的诊断标准是不充分的,还应辅以“房率和室率都不太快、室率慢于房率的1/2”,才是完整的诊断标准。足够的心电图资料是确诊的重要保障。     

Pacemaker dependency after transcatheter aortic valve implantation with the self-expanding Medtronic CoreValve System

Background/objectives

To determine pacemaker (PM) dependency at follow-up visit in patients who underwent new permanent pacemaker implantation (PPI) following transcatheter aortic valve implantation (TAVI).

Methods

Single center prospective observational study including 167 patients without previous PM implantation who underwent TAVI with the self-expanding Medtronic CoreValve System (MCS) between November 2005 and February 2011. PM dependency was defined by the presence of a high degree atrioventricular block (HDAVB; second [AV2] and third degree [AV3B]), or a slow (< 30 bpm) or absent ventricular escape rhythm during follow-up PM interrogation.

Results

A total of 36 patients (21.6%) received a new PM following TAVI. The indication for PM was AV2B (n = 2, 5.6%), AV3B (n = 28, 77.8%), postoperative symptomatic bradycardia (n = 3, 8.3%), brady–tachy syndrome (n = 1, 2.8%), atrial fibrilation with slow response (n = 1, 2.8%) and left bundle branch block (n = 1, 2.8%). Long term follow-up was complete for all patients and ranged from 1 to 40 months (median (IQR): 11.5 (5.0–18.0 months). Of those patients with a HDAVB, 16 out of the 30 patients (53.3%) were PM independent at follow-up visit (complete or partial resolution of the AV conduction abnormality). Overall, 20 out of the 36 patients (55.6%) who received a new PM following TAVI were PM independent at follow-up.

Conclusion

Partial and even complete resolution of peri-operative AV conduction abnormalities after MCS valve implantation occurred in more than half of the patients.     

Acquired nonsurgical complete atrioventricular block in a child with endocardial cushion defect

Acquired nonsurgical complete atrioventricular block is uncommon in children. We report an 11-year-old asymptomatic girl with endocardial cushion defect who gradually developed progressive conduction abnormality and complete atrioventricular block prior to open heart surgery. To our knowledge, a gradual progressive, nonsurgical, acquired atrioventricular block in endocardial cushion defect has not been described before. This report discusses the possible pathogenesis of acquired nonsurgical complete atrioventricular block in endocardial cushion defect and reviews the literature.     

射频消蚀术并发症及其防治

３４４例射频消蚀术中出现并发症９例（２．６％），其中心脏破裂致死１例（０．３％），ＩＩＩ度房室传导阻滞３例（０．９％），心室颤动２例（０．６％），主动脉瓣损伤、大头导管误入冠状动脉引起冠状动脉一过性缺血及股动脉术后出血形成巨大皮下血肿各１例。对各种并发症的防治进行了分析讨论。提出经验不足是产生并发症的主要原因。     

Unusual Wenckebach phenomenon due to an atrial tachycardia arising from the apex of Koch’s triangle in the presence of dual AV nodal physiology

A case of a patient with narrow QRS tachycardia and without structural heart disease is presented. The electrophysiologic study revealed an atrial tachycardia in the presence of dual atrioventricular (AV) nodal physiology and AV block at suprahisian level, the latter two leading to an unusual Wenckebach periodicity. The entire septal area was mapped as was the coronary sinus (CS) os and the earliest atrial activation was found at the apex of Koch’s triangle in close vicinity to the His bundle (HB). Cryomapping at that point reproducibly terminated the tachycardia without impairing AV conduction. Cryoablation rendered the tachycardia non-inducible. Discontinuous AV conduction persisted but AV nodal reentrant tachycardia (AVNRT) was not inducible. Six months later the patient is arrhythmia-free.     

Cystic tumour of the atrioventricular nodal region: report of a case successfully treated with surgery

A case is reported of a 59 year old woman who presented with palpitations. Electrocardiographic studies revealed atrial fibrillation and atrioventricular block. Echocardiography and magnetic resonance imaging showed a right atrial cystic mass attached to the interatrial septum. The patient underwent surgical excision of the mass. Histopathological findings were of a cystic tumour of the atrioventricular nodal region. This is the second report of this condition diagnosed antemortem and treated successfully with surgical excision.


Keywords: atrioventricular block; cystic tumour; excision     

Case Report: Anterograde 2:1 and Retrograde 3:2 Wenckebach Block During Atrioventricular Nodal Tachycardia: Controversies of the Upper and Lower Common Pathways

The exact nature of the reentry circuit for the atrioventricular nodal reentrant tachycardia (AVNRT) and particularly the concept and role of the upper and lower common pathways is not well defined. Although it is well accepted that the His-Purkinje system and the ventricles are not an essential part of the tachycardia circuit, controversy still exists as to whether the atria are essential components of the circuit. We describe a patient in whom the AVNRT perpetuated despite the spontaneous development of 2:1 anterograde and 3:2 retrograde block. To our knowledge, such a combination of electrophysiological phenomenon has not been previously reported. The electrophysiological basis of these observations and their clinical implications are discussed.     

长期右心室心尖部起搏对三度房室阻滞患者心功能的影响

目的了解长期持续右心室心尖部（RVA）起搏对基础心功能正常患者心脏结构和功能的影响及其危险因素。方法选取基础心功能正常、因三度房室阻滞（AVB）而植入VVI或DDD起搏器的患者为研究对象,观察其是否出现心力衰竭相关症状或因心力衰竭入院,同时行超声心动图随访,并对相关临床因素进行分析。心力衰竭的定义为随访中出现因心力衰竭入院或死亡、或超声心动图示左心室射血分数（LVEF）≤0．40。左心室（LV）结构、功能受损是指超声心动图观察到的LV局部或总体收缩活动减弱、LVEF〈0．50或左心室舒张末期内径（LVEDD）〉56mm之任意一项。结果共141例患者平均随访8．3年后,8例（5．7％）出现心力衰竭,20例（14．2％）出现左心室结构、功能受损;其发生率均随起搏时间增长而增加。随访中患者平均LVEF下降、平均LVEDD增加,但其起搏前后的差异并无统计学意义。患者性别、植入起搏器时年龄、起搏模式以及是否合并高血压、糖尿病、冠心病、心房扑动和心房颤动等因素均与心力衰竭发生或左心室结构、功能受损无关。结论长期RVA起搏者存在心脏结构和功能受损的可能,起搏时问越长发生几率越高,但其危险因素尚不明确。     

Primo-implantation of a dual-chamber pacemaker in a patient with symptomatic first-degree AV block with proven AV dyssynchrony at an abnormally long PQ interval (pseudopacemaker syndrome)

First-degree atrioventricular block (first-degree AV block) is defined as a PR interval exceeding 200 ms [1]. The abnormally long PR interval may result in the condition resembling pacemaker syndrome, i.e. the collision of the atrial systole and the ventricular systole, being accompanied with similar symptoms including cardiac failure even if the systolic function of the left ventricle [2] is normal. This is called “pseudopacemaker syndrome” [3], [4], [5], [6], [7], [8], [9], [10]. This paper describes the case of a female patient with a significantly long PR interval after the replacement of the mitral valve, showing symptoms of pseudopacemaker syndrome. This is a relatively rare clinical condition. When it occurs, the implantation of a pacemaker in Class IIa [11] is recommended.     

The RR index test for the differentiation of atrioventricular nodal block from His--Purkinje block during incremental atrial pacing in patients with bifascicular block

AIMS: His—Purkinje block induced by incremental atrial pacingis highly predictive of an impending high degree atrioventricularblock in patients with bifascicular block. The His potentialis, however, sometimes not measurable or is lost in the ventriculardepolarization. The aim of this study was to evaluate whetherthe comparison of RR intervals before and after atrioventricularblock, induced by incremental atrial pacing, could differentiatebetween atrioventricular nodal and His—Purkinje blockin patients with bifascicular block. METHODS AND RESULTS: In 98 patients with bifascicular block, incremental atrial pacingwas performed as part of an invasive electrophysiological study.An ‘RR index’ was constructed by calculating thenumerical difference between the RR interval immediately beforeand after the atrioventricular block divided by the RR intervalimmediately before the pacing-induced block. Endocavitary recordingof the His bundle potential was used for defining the levelof atrioventricular block. The median RR index was 0·98(range 0·88–1·02) in recordings with His—Purkinjeblock and 0·49 (range 0·11–0·89)in recordings with atrioventricular nodal block (P<0·001).An RR index of 0·85 had a sensitivity of 100% and a specificityof 99% for the identification of atrioventricular block localizedto the His—Purkinje system. CONCLUSION: The use of an RR index is a helpful tool in the differentiationof His—Purkinje from atrioventricular nodal block in patientswith bifascicular block undergoing incremental atrial pacingas part of an invasive electrophysical study.