Adenosine can improve the intra-atrial conduction block along the mitral annulus during accessory pathway ablation

A 10-year-old boy with a supraventricular tachycardia was referredfor catheter ablation. An electrophysiologic study revealeda left lateral concealed accessory pathway (AP). A few radiofrequency(RF) applications targeting the AP resulted in an inadvertentintra-atrial conduction block at the mitral isthmus withoutany damage to the AP. Adenosine was then administered duringleft ventricular pacing. Soon after that, the conduction atthe mitral isthmus recovered partially, and that change disappearedsoon. Those findings suggested that the administration of adenosinemay transiently recover the conduction at the mitral isthmusdamaged by RF ablation.     

Intra-atrial conduction block along the mitral valve annulus during accessory pathway ablation: evidence for a left atrial "isthmus"

INTRODUCTION: We observed a change in the atrial activation sequence during radiofrequency (RF) energy application in patients undergoing left accessory pathway (AP) ablation. This occurred without damage to the AP and in the absence of a second AP or alternative arrhythmia mechanism. We hypothesized that block in a left atrial "isthmus" of tissue between the mitral annulus and a left inferior pulmonary vein was responsible for these findings. METHODS AND RESULTS: Electrophysiologic studies of 159 patients who underwent RF ablation of a left free-wall AP from 1995 to 1999 were reviewed. All studies with intra-atrial conduction block resulting from RF energy delivery were identified. Fluoroscopic catheter positions were reviewed. Intra-atrial conduction block was observed following RF delivery in 11 cases (6.9%). This was evidenced by a sudden change in retrograde left atrial activation sequence despite persistent and unaffected pathway conduction. In six patients, reversal of eccentric atrial excitation during orthodromic reciprocating tachycardia falsely suggested the presence of a second (septal) AP. A multipolar coronary sinus catheter in two patients directly demonstrated conduction block along the mitral annulus during tachycardia. CONCLUSION: An isthmus of conductive tissue is present in the low lateral left atrium of some individuals. Awareness of this structure may avoid misinterpretation of the electrogram during left AP ablation and may be useful in future therapies of atypical atrial flutter and fibrillation.     

Role of bipolar electrogram polarity mapping in localizing recurrent conduction in the isthmus early and late after ablation of atrial flutter

Objectives. Bipolar electrogram polarity was analyzed to localize the recurrent conduction site in the isthmus between the tricuspid annulus (TA) and inferior vena cava (IVC) in recurrent atrial flutter (AF).Background. Despite the initial successful linear isthmus ablation, recurrence of transisthmus conduction and AF is not uncommon. It is unclear how the recurrent conduction site can be identified.Methods. Fourteen patients with recurrent AF were studied: four with late recurrence remote from the first ablation and 10 with early recurrence within 60 minutes after the initial successful ablation. Bipolar electrogram polarity mapping was performed during low lateral right atrium (LLRA) pacing during sinus rhythm while recording bipolar electrograms from the septal portion of the isthmus along the previously ablated line. The septal side of the isthmus from TA to IVC was arbitrarily divided into five sites, and the bipolar electrodes with cathode at the tip and anode at the second was placed at each site. The recurrent conduction site was localized by analyzing the polarity of the bipolar electrogram recorded at each site.Results. All recurrent AF was due to reentry around TA. During pacing from LLRA, as the mapping electrode was moved from TA to IVC side, the major polarity of the electrogram changed from negative to positive in all patients. A transitional electrogram with the equal amplitudes in positive and negative components was recorded between the sites showing mainly negative and positive electrograms, indicating electrogram polarity reversal at this site. Application of radiofrequency energy to this single site resulted in the elimination of transisthmus conduction in all patients with a single application in 11 patients and 2 or 3 in the remaining 3.Conclusions. Bipolar electrogram polarity mapping with attention to the polarity reversal point is useful for identifying and ablating the recurrent conduction site.     

When a sperm meets an egg: block to polyspermy

Embryonic development is initiated after the fertilizing spermatozoon enters the egg and triggers a series of events known as egg activation. Activation results in an increase in intracellular calcium concentration, cortical granule exocytosis (CGE), cell cycle resumption and recruitment of maternal mRNA. CGE is an evolutionary developed mechanism that causes modification of the zona pellucida to prevent penetration of additional spermatozoa, ensuring successful egg activation and embryo development. The egg CGE is a unique and convenient mammalian model for studying the different proteins participating at the membrane fusion cascade, which, unlike other secretory cells, occurs only once in the egg's lifespan. This article highlights a number of proteins, ascribed to participate in CGE and thus the block to polyspermy. CGE can be triggered either by a calcium dependent pathway, or via protein kinase C (PKC) activation that requires a very low calcium concentration. In a recent study, we suggested that the filamentous actin (F-actin) at the egg's cortex is a dynamic network. It can be maneuvered towards allowing CGE by activated actin associated proteins and/or by activated PKC and its down stream proteins, such as myristoylated alanine-rich C kinase substrate (MARCKS). MARCKS, a protein known to cross-link F-actin in other cell types, was found to be expressed and colocalized with actin in non-activated MII eggs. We further demonstrated MARCKS dissociation from actin after activation by ionomycin, a process that can lead to the breakdown of the actin network, thus allowing CGE. The more we know of the intricate process of CGE and of the proteins participating in it, the more the assisted reproductive procedures might benefit from that knowledge.     

Double potentials along the ablation line as a guide to radiofrequency ablation of typical atrial flutter

OBJECTIVES: The purpose of this study was to determine the characteristics of double potentials (DPs) that are helpful in guiding ablation within the cavo-tricuspid isthmus. BACKGROUND: Double potentials have been considered a reliable criterion of cavo-tricuspid isthmus block in patients undergoing radiofrequency ablation of typical atrial flutter (AFL). However, the minimal degree of separation of the two components of DPs needed to indicate complete block has not been well defined. METHODS: Radiofrequency ablation was performed in 30 patients with isthmus-dependent AFL. Bipolar electrograms were recorded along the ablation line during proximal coronary sinus pacing at sites at which radiofrequency ablation resulted in incomplete or complete isthmus block. RESULTS: Double potentials were observed at 42% of recording sites when there was incomplete isthmus block, compared with 100% of recording sites when the block was complete. The mean intervals separating the two components of DPs were 65 +/- 21 ms and 135 +/- 30 ms during incomplete and complete block, respectively (p < 0.001). An interval separating the two components of DPs (DP(1-2) interval) <90 ms was always associated with a local gap, whereas a DP(1-2) interval > or =110 ms was always associated with local block. When the DP(1-2) interval was between 90 and 110 ms, an isoelectric segment within the DP and a negative polarity in the second component of the DP were helpful in indicating local isthmus block. A DP(1-2) interval > or =90 ms with a maximal variation of 15 ms along the entire ablation line was an indicator of complete block in the cavo-tricuspid isthmus. CONCLUSIONS: Detailed analysis of DPs is helpful in identifying gaps in the ablation line and in distinguishing complete from incomplete isthmus block in patients undergoing radiofrequency ablation of typical AFL.     

消融线径同侧心房近-远端起搏检测右心房峡部完全性阻滞的意义

射频消融阻断下腔静脉至三尖瓣环间的右心房峡部是治疗典型心房扑动（房扑）的有效方法。目前，多采用消融后分别起搏峡部两侧，观察心房激动顺序的变化或消融线径上的宽间期双电位来检测峡部完全阻滞的存在。本文提出另一种可靠而快捷的方法，对判断峡部完全性阻滞有较大价值。     

典型心房扑动消融术后峡部计时间期的变化预测双向阻滞的价值

典型的心房扑动(房扑)是右心房内的大折返所致已成共识，下腔静脉、三尖瓣环峡部是折返环的一部分。因此，射频消融下腔静脉、三尖瓣环峡部并产生峡部双向阻滞，是成功消融典型房扑和减少复发的可靠标志。目前，多采用心房激动顺序或消融部位的双电位技术确定峡部双向阻滞的存在。通过比较房扑成功消融前、后右心房峡部传导时间，从而提出峡部传导时间的延长程度对峡部完全性     

Necessity for biatrial ablation to achieve bidirectional cavotricuspid isthmus conduction block in a patient following senning operation

We report the case of a 28-year-old male patient with a 17-year history of recurrent symptomatic atrial tachyarrhythmia following Senning operation for transposition of the great arteries. Biatrial electroanatomic mapping and entrainment mapping revealed counterclockwise peri-tricuspid annulus reentry in which cavotricuspid isthmus tissue in both systemic and pulmonary venous atria was involved. Linear ablation of the cavotricuspid isthmus in the pulmonary venous atrium terminated the tachycardia but did not block the isthmus conduction, and the tachycardia was reinduced. Bidirectional isthmus conduction block could be achieved only after additional linear ablation targeting the cavotricuspid isthmus tissue in the systemic venous atrium. We conclude that biatrial ablation may be necessary in order to achieve bidirectional isthmus block and prevent tachycardia recurrence in some patients following Senning or Mustard operation.     

Role of transisthmus conduction intervals in predicting bidirectional block after ablation of typical atrial flutter

INTRODUCTION: Complete bidirectional cavotricuspid isthmus block is the endpoint for ablation of typical atrial flutter. The purpose of this study was to determine whether the extent of prolongation of the transisthmus interval after ablation predicts complete bidirectional block. METHODS AND RESULTS: Fifty-seven consecutive patients underwent 60 ablation procedures for isthmus-dependent atrial flutter. The clockwise and counterclockwise transisthmus intervals were determined before and after ablation during pacing from the low lateral right atrium and the coronary sinus. Bidirectional block was achieved with ablation in 55 (96%) of 57 patients. The transisthmus intervals before ablation and after complete transisthmus block were 100.3 +/- 21.1 msec and 195.8 +/- 30.1 msec, respectively, in the clockwise direction (P < 0.0001), and 98.2 +/- 24.7 msec and 185.7 +/- 33.9 msec, respectively, in the counterclockwise direction (P < 0.0001). An increase in the transisthmus interval by > or = 50% in both directions after ablation predicted complete bidirectional block with 100% sensitivity and 80% specificity. The positive and negative predictive values were 89% and 100%, respectively. The diagnostic accuracy of a > or = 50% prolongation in the transisthmus interval was 92%. CONCLUSION: Prolongation of the transisthmus interval by > or = 50% in the clockwise and counterclockwise directions is associated with a high degree of diagnostic accuracy and an excellent negative predictive value in determining complete bidirectional transisthmus block. This may be a useful and simple adjunctive criterion for assessment of complete transisthmus conduction block.     

Alcohol ablation of atrioventricular conduction

Transcoronary ablation of atrioventricular conduction by dehydrated alcohol was attempted in 14 patients with refractory atrial arrhythmias. Alcohol (0.5 or 1.0 ml) was delivered after selective catheterisation of the atrioventricular nodal artery in the 10 patients in whom the artery could be identified by cineangiography. The other four patients underwent electrical ablation when the nodal artery could not be catheterised. Temporary atrioventricular block induced by dilute contrast and cold saline (0.9%) confirmed that the catheter was in the correct position before the alcohol was delivered. In all 10 patients complete atrioventricular block developed after alcohol ablation. The block persisted in all four patients given 1.0 ml alcohol but not in four of the six given 0.5 ml. The mean (SD) creatine kinase (MB fraction) at four to six hours after ablation was 76.5 (49.5) IU after 1.0 ml and 75.5 (43.1) IU after 0.5 ml alcohol (normal less than 20 IU). The overall success rate of alcohol ablation in the whole group on an "intention to treat" basis was 43%. The procedure was a technical success in six of the 10 patients in whom the nodal artery was identified. Transcoronary alcohol ablation of atrioventricular conduction should be considered in patients in whom electrical techniques have been unsuccessful.     

差异性起搏法对典型心房扑动消融后峡部完全传导阻滞的预测价值

目的探讨一种简单的方法用以鉴别峡部消融线是完全阻滞还是存在缓慢传导,以降低典型心房扑动(简称房扑)消融后的复发率。方法前瞻性研究30例典型房扑患者消融后峡部的传导,放置20极Halo电极,使最远端的两对电极靠近阻滞线,分别起搏这两对电极并在消融线上标测局部双电位或多电位,我们假设局部电位的初始成分和终末成分分别代表消融线两侧的激动,当起搏部位由离消融线较近的电极对转为较远电极对起搏时,刺激信号到局部电位初始电位成分的时间将会延迟,而刺激信号到局部电位终末成分的时间变化取决于阻滞线是否完整。终末电位提前或不变提示完全阻滞,终末电位延迟提示阻滞线上有传导缝隙。结果用传统判断峡部阻滞的方法做参照标准,选取位点进行差异性起搏共54次,峡部完全阻滞前18次,峡部完全阻滞后36次。当起搏部位转为较远电极对时,初始电位均延迟,平均18±9ms,峡部不全阻滞时,终末电位延迟13±7ms,峡部完全阻滞后,终末电位提前12±8ms。差异性起搏对预测峡部完全阻滞的灵敏度达100%,特异度达88.9%。结论差异性起搏可准确鉴别峡部形成完全阻滞还是存在缓慢传导。     

射频导管消融术阻滞经冠状静脉窦传导通路的实验研究

目的　探讨利用射频导管消融术阻滞经冠状静脉窦的电传导通路的方法及可行性。方法　冠状静脉窦口内 5～ 10mm处射频导管消融 ,低位右心房起搏下 ,观察最早激动部位、冠状静脉窦激动顺序和时间、房间隔激动时间、心房激动时间。结果　 (1)冠状静脉窦口或近端射频导管消融可造成经冠状静脉窦电传导通路的完全或部分阻滞。表现在消融前 ,低位右心房起搏时 ,窦口处的电激动明显早于Bachmann束。消融后 ,窦口处的电激动迟于Bachmann束或两者基本一致 ;(2 )消融前后 ,心房激动时间由 (6 1 14± 8 36 )ms延长至 (88 4 3± 19 2 2 )ms,说明低位心房起搏时冠状静脉窦是优势传导通路 ;(3)消融前后的房间隔激动时间及冠状静脉窦激动时间分别为 (2 6 4 3± 8 87)ms对(15 2 8± 10 13)ms和 (39 4 3± 9 78)ms对 (38 0 0± 5 86 )ms。结论　冠状静脉窦近端射频导管消融术阻断经冠状静脉窦的电传导通路的方法是可行的     

Transcoronary chemical ablation of atrioventricular conduction

In seven patients with symptomatic atrial fibrillation and uncontrollable ventricular rates, selective catheterization of the atrioventricular (AV) nodal artery was performed to chemically destroy the AV node. Ethanol at a concentration of 96% and a dose of 0.5-2 ml was used after selective catheterization of the AV nodal artery had demonstrated temporary AV block after the administration of isotonic iced saline. Complete AV block was produced in five patients and AV conduction was sufficiently modified to control symptoms in the remaining two patients. A minimal enzyme rise occurred in six patients. A severe complication in the remaining patient occurred when, after 2 ml ethanol in the AV nodal artery, occlusion developed in the midright coronary artery that led to an inferior wall myocardial infarction. It is concluded that the AV nodal artery can be selectively catheterized using presently available angioplasty techniques. Ethanol can be used to destroy the AV node and block AV conduction.     

Advanced early and late atrioventricular block in acute inferior wall myocardial infarction

Seventy-six patients with acute inferior acute myocardial infarction (AMI) and advanced atrioventricular (AV) block are described. According to pre-established ECG criteria and time of appearance of the advanced AV block, patients were divided into two groups. The early block group consisted of 31 patients who developed advanced AV block during the hyperacute ECG stage of AMI. Advanced AV block in these patients was characterized by early appearance, short duration, third-degree type block, poor response to atropine, and increased need for pacemaker therapy. The late block group consisted of 45 patients who developed advanced AV block during subsequent ECG stages of AMI. Advanced AV block in these patients was characterized by late appearance, longer duration, second-degree type block, positive response to atropine, and diminished need for pacemaker therapy. Morbidity and mortality also differed between both groups. Patients with early block had more syncope (32% vs 2%, p < 0.0001), more left heart failure (36 vs 7%, p < 0.005), and more cardiogenic shock (39% vs 2%, p < 0.001) than patients with late block. The mortality rate in the early block group was high (23%) and similar to that reported in the literature, whereas the mortality rate in the late block group was low (7%, p < 0.05) and similar to the mortality rate reported for acute inferior AMI without advanced AV block. These data identify a subgroup of patients with acute inferior AMI and advanced AV block, which accounts for the high mortality rate reported in this group of patients.     

Alcohol ablation of atrioventricular conduction.

Transcoronary ablation of atrioventricular conduction by dehydrated alcohol was attempted in 14 patients with refractory atrial arrhythmias. Alcohol (0.5 or 1.0 ml) was delivered after selective catheterisation of the atrioventricular nodal artery in the 10 patients in whom the artery could be identified by cineangiography. The other four patients underwent electrical ablation when the nodal artery could not be catheterised. Temporary atrioventricular block induced by dilute contrast and cold saline (0.9%) confirmed that the catheter was in the correct position before the alcohol was delivered. In all 10 patients complete atrioventricular block developed after alcohol ablation. The block persisted in all four patients given 1.0 ml alcohol but not in four of the six given 0.5 ml. The mean (SD) creatine kinase (MB fraction) at four to six hours after ablation was 76.5 (49.5) IU after 1.0 ml and 75.5 (43.1) IU after 0.5 ml alcohol (normal less than 20 IU). The overall success rate of alcohol ablation in the whole group on an "intention to treat" basis was 43%. The procedure was a technical success in six of the 10 patients in whom the nodal artery was identified. Transcoronary alcohol ablation of atrioventricular conduction should be considered in patients in whom electrical techniques have been unsuccessful.