High-frequency stimulation in the prevention of atrioventricular tachycardias: relation to stimulation site and location of the accessory conduction pathway

To assess the validity of train stimulation for the prevention of accessory pathway mediated atrioventricular tachycardia, thirteen patients were studied. Tachycardia was induced from high right atrium and coronary sinus by means of single extrastimuli; preventive stimulation at high right atrium and coronary sinus consisted of the delivery of a train of ten or eleven stimuli 10 ms apart, following the tachycardia initiating stimulus. Preventive train stimulation at the site of tachycardia induction was successful in all patients when the train exceeded the atrial effective refractory period of the initiating stimulus to achieve single atrial capture within the "preventive zone". In patients with a left-sided accessory pathway in whom tachycardia was induced from the coronary sinus, preventive stimulation at high right atrium failed because of interatrial conduction delay. It is concluded that train stimulation is an effective mode of prevention of atrioventricular reentrant tachycardia, yet preventive stimulation should be performed as close as possible to the reentry circuit to reduce interatrial conduction delay.     

Prevention of reciprocal tachycardia by programmed electrostimulation

10 patients with an accessory atrioventricular pathway were studied by means of programmed electrical stimulation to test the feasibility of tachycardia prevention with an extrastimulus delivered after the tachycardia-initiating beat. Reciprocating atrioventricular tachycardia was reproducibly initiated from high right atrium in all 10 patients with a single extrastimulus. A second extrastimulus delivered to the same site resulted in prevention of tachycardia in all patients, when this extrastimulus was given within a "preventive zone" which started 10 ms after the effective atrial refractory period of the tachycardia initiating beat. The average width of the preventive zone was 50 ms in our patients, independent of the initial tachycardia interval or tachycardia cycle length. Tachycardia prevention was always successful with a single atrial extrastimulus, whereas termination of an ongoing tachycardia required at least two atrial or ventricular extrastimuli.     

Train stimulation at the atria for prevention of atrioventricular tachycardia: dependence on accessory pathway location

In 12 patients with accessory pathway-mediated supraventricular tachycardia, programmed electrical stimulation with a rapid train of 10 stimuli was assessed for prevention of tachycardia induction. Tachycardia was induced with one or two extrastimuli from both the right and the left atrium (by way of the coronary sinus). Preventive train stimulation, with the train delivered after the tachycardia-initiating stimulus, was attempted at the site of tachycardia induction as well as at the opposite site. Prevention at the site of tachycardia induction was successful in all patients when the length of the train (90 ms) exceeded the effective refractory period of the tachycardia-initiating stimulus to achieve single atrial capture within the "preventive zone." However, in patients with a left-sided accessory pathway, preventive stimulation at the right atrium failed when tachycardia was induced from the coronary sinus because of interatrial conduction delay. It is concluded that train stimulation is an effective mode for supraventricular tachycardia prevention, yet the site of preventive stimulation should lie as close as possible to the anatomic site of the reentrant circuit to reduce interatrial conduction delay.     

Entrainment of circus movement tachycardia utilizing an accessory pathway with long retrograde conduction times during ventricular and atrial stimulation

An unusual case is presented in which a circus movement tachycardia incorporating an accessory pathway with long retrograde conduction time was transiently entrained. Overdrive high right atrial stimulation produced entrainment without atrial fusion since collision of anterograde and retrograde impulses took place within the accessory pathway. Tachycardia termination occurred when, at a faster pacing rate, an atrial impulse that collided in the accessory pathway was blocked at the atrioventricular (AV) node. In contrast, the entrainment seen during right ventricular apical stimulation was characterized by the occurrence of both fusion and collision within the ventricles. The tachycardia was terminated when a pure paced impulse that collided in the normal pathway was blocked in a retrograde direction in the accessory pathway. These data indicate that: 1) transient entrainment of this arrhythmia (circus movement tachycardia) can be identified by the classical criteria used to diagnose it, provided that fusion and collision occur within the ventricles; and 2) the accessory pathway is the weak link for tachycardia termination only during ventricular pacing since the AV node is the weak link during atrial stimulation.     

心室融合波伴心房激动提前对间隔旁路逆传的房室折返性心动过速的诊断作用

目的 观察心室融合波伴心房激动提前对间隔旁路逆传的顺向型房室折返性心动过速(OAVRT)的诊断作用。方法 按心内电生理检查标准和射频消融结果，将47例符合人选条件的患者分为两组：房室结折返性心动过速(AVNRT)组和间隔旁路逆传的0AVRT组，分别为24例和23例。心动过速时行心室期前程序刺激(RS2刺激)和心室快速刺激，测量体表心电图上心室融合波之后的心房激动时间是否提前。结果 RS2刺激和心室快速刺激均能形成多个心室融合波。AVNRT组无l例伴有心房激动提前(特异性100％)，而OAVRT组在心室刺激成分明显的心室融合波时，心房激动均被提前(敏感性100％)。两组间的差异十分显著(P＜0．001)。结论 心室融合波伴心房激动时间提前是诊断间隔旁路逆传OAVRT的可靠指标，具有敏感性和特异性高的特点，而且也可用于未能记录到希氏束电图的患者。     

Tachycardia prevention by programmed stimulation

Ten patients with an atrioventricular accessory pathway were studied by standard electrophysiologic techniques to determine if reentrant tachycardia can be prevented in these patients by delivery of a single extrastimulus, applied at a critical time after the tachycardia-initiating stimulus (or stimuli). In all 10 patients, reentrant tachycardia was reproducibly induced from the high right atrium with a single premature beat, and initiation of tachycardia could be prevented from the same site by a second premature beat. This second extrastimulus was effective if delivered within a zone that began 10 ms outside of the effective refractory period of the tachycardia-initiating stimulus and averaged 50 ms in width. This zone was termed the "preventive zone." The width of the preventive zone was independent of the initial tachycardia interval and the tachycardia cycle length. Prevention of reentrant tachycardia was always possible with a single atrial extrastimulus, whereas termination of the ongoing tachycardia required at least 2 atrial extrastimuli or stimulation from the right ventricle.     

心室起搏拖带对房室结折返性和间隔旁路参与的房室折返性心动过速的鉴别作用

目的　研究心动过速时心室起搏拖带对房室结折返性心动过速 (AVNRT )和间隔旁路参与的顺向型房室折返性心动过速 (间隔旁路ORT)的鉴别意义。方法　 30例AVNRT和 2 5例间隔旁路ORT病人在心动过速发生后 ,采用较心动过速的周长 (TCL)短 10～ 4 0ms的周长行右心室起搏拖带心动过速。测量右心室起搏之前的心室 心房 (VA)间期和TCL。停止起搏后 ,测量最后一次刺激信号至最后起搏拖带的心房激动 (SA)间期 ,以及起搏后间期 (PPI)。结果　所有 30例AVNRT病人的SA -VA间期 >85ms、PPI-TCL >115ms,而 2 5例ORT病人的SA -VA间期 <85ms、PPI-TCL <115ms。结论　PPI TCL和SA VA间期是鉴别AVNRT和间隔旁路ORT的非常可靠的指标 ,具有较高的特异性。     

Diagnosis of the mechanism of reciprocating tachycardia by a simplified electrophysiological study

The authors attempted to identify the parameters which best differentiated intranodal reentry from tachycardias associated with an accessory pathway during a simplified electrophysiological study. The data were obtained by using two catheters, one recording right atrial activity and the other delivering programmed stimulation in the right ventricle. Sixty-four patients in whom the mechanism of their tachycardias had previously been determined were studied. There were 19 intranodal and 45 accessory pathway tachycardias. The following parameters were studied: the ventriculo-atrial interval during tachycardia; the prematurity of atrial activity in response to programmed ventricular stimulation; the shortest ventriculo-atrial interval when the atrial activity was premature; the difference between the shortest ventriculo-atrial interval with atrial prematurity and the ventriculo-atrial interval during tachycardia; in the absence of prematurity the ventriculo-atrial interval with the shortest ventricular coupling was used. The ventriculo-atrial interval during tachycardia was shorter in intranodal reentry (43 ms vs 170 ms, p less than 0.001). This interval was greater than 120 ms only in accessory pathway tachycardias and was only under 75 ms in patients with intranodal tachycardias. Premature atrial activation was observed in 42% of intranodal and 98% of accessory pathway tachycardias (p less than 0.001). The predictive value for tachycardias involving an accessory pathway was 85% when the auriculogramme was premature and, conversely, it was 92% for intranodal tachycardia.(ABSTRACT TRUNCATED AT 250 WORDS)     

Radiofrequency catheter ablation of both atrial ventricular nodal reentrant and atrial ventricular reentrant tachycardia in a single session

Radiofrequency catheter ablation is a new therapeutic approach to treat patients with symptomatic drug-resistant paroxysmal supraventricular tachycardia. Ablation of two accessory atrioventricular pathways in a single session has been frequently described previously. However, ablation in a single session of both the fast pathway, involved in atrial ventricular nodal reentrant tachycardia, and a concealed atrioventricular accessory pathway involved in a circus movement tachycardia has rarely been reported. A 57-year-old man with a grade III aortic incompetence had the infrequent association of atrial ventricular nodal reentrant tachycardia and orthodromic circus movement tachycardia due to a concealed accessory pathway. He presented with drug-resistant reentrant supraventricular tachycardia and, in a single session, underwent a successful radiofrequency catheter ablation of the fast atrial ventricular nodal pathway and a concealed posteroseptal accessory pathway. During a 10-month follow-up he was free of palpitations without any antiarrhythmic therapy and underwent elective aortic valve replacement.     

Second degree block during reciprocal atrioventricular nodal tachycardia.

Of 67 patients with reciprocal atrioventricular (A-V) nodal tachycardia consecutively studied by programmed electrical stimulation of the heart, nine patients showed second degree block toward the ventricle and one patient toward the atrium during tachycardia. In four patients the occurrence of block was critically related to the prematurity of the test stimulus initiating the tachycardia. In three patients block developed following increase in rate of tachycardia. In two patients block could be elicited by introducing premature ventricular stimuli during tachycardia. Our observations indicate that different mechanisms may be responsible for second degree block during reciprocal supraventricular tachycardia. The finding of second degree block during reciprocal supraventricular tachycardia excludes a tachycardia with A-V conduction over the A-V node - His pathway and V-A conduction over an accessory A-V pathway.     

室性心动过速合并室上性心动过速的射频消融

目的报道7例室性心动过速（VT）合并室上性心动过速（sVT）的射频消融。方法7例患者男6例,女1例,平均年龄（21±9）岁。阵发性心动过速病史（3．7±2．0）年。术中心房和心室刺激诱发VT和SVT,并进行消融。结果7例患者心房或心室刺激能反复诱发和终止VT合并SVT。法洛四联症矫治术后右心室VT合并三尖瓣环峡部依赖性心房扑动（AFL）1例,其余6例均为维拉帕米敏感性左心室特发性室速（ILVT）,分别合并AFL1例,左后间隔旁路参与的顺向型房室折返性心动过速（AVRT）1例,冠状静脉窦口慢旁路参与的顺向型AVRT1例,慢慢型房室结折返性心动过速（AVNRT）1例,左侧游离壁旁路参与的顺向型AVRT2例。7例患者的两种心动过速均成功消融,所有患者消融术后随访2年,无一例VT或SVT复发。结论VT合并SVT并不少见,消融术中应放置必需的心腔内电极导管,完成详细电生理检查,避免漏诊。一次消融应根除两种疾病。     

Prevention of reentrant tachycardia by single beat or repetitive stimulation

Eleven patients with an atrioventricular accessory pathway werestudied by programmed electrical stimulation to determine ifreentrant tachycardia could be prevented by delivery of eithera single atrial extrastimulus, applied at a critical time afterthe tachycardia-initiating stimulus (or stimuli), or a trainof stimuli. In all 11 patients, reentrant tachycardia was reproduciblyinduced from the high right atrium with a single premature beat,and in all patients initiation of tachycardia was preventedfrom the same site by a second premature beat. This second extrastimuluswas effective if delivered within a zone which began 10 ms outside the effective refractory period of the tachycardia-initiatingstimulus and averaged 61 ms in width. This was termed the ‘preventivezone’. In 7 patients the effect of train stimulationtothe high right atrium was studied. In all 7, the results wereconcordant with those obtained by single-beat stimulation. Anytrain which achieved single atrial capture within the preventivezone was effective in preventing tachycardia. Prevention wasalways possible with a single atrial extrastimulus or with single-capturetrain stimulation, whereas termination of an ongoing tachycardiarequired at least 2 atrial extrastimuli, or stimulation fromthe right ventricle.     

Genesis of auricular fibrillation in the Wolff-Parkinson-White syndrome

Atrial fibrillation seems to be more common in the absence of associated cardiac disease in the Wolff-Parkinson-White syndrome (WPW) than in subjects of the same age without this condition. The aim of this study was to analyse the electrophysiological mechanism of AF and to establish its relationship to the accessory pathway. The series comprises 14 out of 51 patients with WPW undergoing classical endocavitary investigation associating the recording of cardiac potentials from the His bundle, right atrium (RA), left atrium (LA) via the coronary sinus and atrial and ventricular stimulation techniques. Three mechanisms of inducing AF were analysed : - AF triggered by RA stimulation : either by a premature extra stimulus or overdrive atrial pacing. In all cases, the accessory pathway was right sides. - AF triggered by overdrive ventricular pacing : three cases were left sided accessory pathways in which atrial desynchronisation was localised in the LA. - Conversion of reciprocating tachycardia to AF (9 cases). In 2 cases, this was preceded by a progressive acceleration of the heart rate. Of 3 left sided accessory pathways, the atrial desynchronisation was located in the LA in 2 cases. The factors which facilitate AF in THE WPW syndrome are discussed : increased atrial vulnerability, the role of the rapid return of ventricular excitation to the atria through the accessory pathway. Our observations suggest that the accessory pathway plays a role in the genesis of AF in the WPW syndrome.     

Electrophysiologic mechanisms of adverse effects of class I antiarrhythmic drugs (cibenzoline,pilsicainide, disopyramide,procainamide) in induction of atrioventricular re-entrant tachycardia

Summary We evaluated the electrophysiological mechanisms of adverse effects of class I antiarrhythmic drugs (cibenzoline in seven patients, pilsicainide in two, and disopyramide in two, and procainamide in three) in the induction of orthodromic atrioventricular re-entrant tachycardia (AVRT). In 14 patients (10 males, 4 females; mean age 37±18 years) who had inducible AVRT despite the administration of class I drugs, electrophysiological effects of class I antiarrhythmic drugs were evaluated using programmed electrical stimulation techniques. In 4 out of 6 patients with a manifest accessory pathway, class I drugs induced unidirectional conduction block of the accessory pathway (antegrade conduction block associated with preserved retrograde conduction) and enhanced the induction of AVRT with atrial extrastimulation. In eight patients with a concealed accessory pathway, the outward or inward expansion of the tachycardia induction zone was observed in patients who had greater prolongation of the conduction time than the refractory period of the retrograde accessory pathway after class I drugs. During ventricular extrastimulation, the induction of bundle branch reentry after class I drugs initiated the AVRT in patients with either manifest or concealed accessory pathways. We conclude that the adverse effects of class I drugs are mainly due to induction of unidirectional retrograde conduction of the manifest accessory pathway and the greater prolongation of the retrograde conduction time of the concealed accessory pathway than the refractory period, regardless of the subclassification of class I drugs.     

Radiofrequency Application to the Posteroseptal Region Alters Retrograde Accessory Pathway Activation

Introduction: Radiofrequency applications to the posteroseptal region can ablate the atrioventricular accessory pathway residing in this area. In conjunction with the adjacent anatomic structures, however, ablative lesions which do not effectively ablate the accessory pathway could markedly alter retrograde atrial activation sequence and confound interpretation of further mapping of an accessory pathway.Methods and Results: Electrophysiologic studies, endocardial activation mapping and radiofrequency catheter ablation were undertaken in three patients with recurrent supraventricular tachycardia. Patients were initially thought to have a single posteroseptal accessory pathway; earliest ventrioatrial activation during tachycardias and during ventricular pacing was at the coronary sinus ostium, but initial radiofrequency applications were unsuccessful to ablate the pathway. After initial radiofrequency applications to the posteroseptal region, the earliest retrograde atrial activation changed to the right atrial free wall in two patients. Additional radiofrequency application to the posteroseptal area was able to ablate the single posteroseptal accessory pathway in one patient. Radiofrequency application to the right atrial free wall was required to stop tachycardia initiation in other patient. The third patient was suspected of having a slow-slow atrioventricular nodal reentry tachycardia. Radiofrequency application to the posteroseptal area changed the earliest retrograde atrial activation to the distal coronary sinus recording site, mimicking an accessory pathway at the left atrial free wall. Radiofrequency application to the anteroseptum was able to ablate the concealed accessory pathway.Conclusion: Radiofrequency applications to the posteroseptal region can markedly alter retrograde atrial activation, thereby confounding further mapping of the accessory pathway.     

Electrophysiologic manifestations of ventricular tachyarrhythmias provoking appropriate defibrillator interventions in high-risk patients with hypertrophic cardiomyopathy

Introduction: Our objective was to determine features of ventricular tachyarrhythmias triggering appropriate implantable cardioverter-defibrillator (ICD) interventions in hypertrophic cardiomyopathy (HCM).
Methods and Results: The study cohort was 68 high-risk HCM patients who received ICDs for primary sudden cardiac death prevention from 1995 to 2003. All episodes of sustained ventricular tachyarrhythmias identified by stored intracardiac electrograms were analyzed. Nine patients had 51 episodes of sustained ventricular tachyarrhythmic events that required device therapy (mean follow-up, 3.4 ± 2.2 years; cumulative event rate, 3.2% per year): five had 47 episodes of monomorphic ventricular tachycardia (VT); four each had one episode of ventricular fibrillation (VF). Sinus tachycardia or atrial fibrillation was the initiating rhythm in five of nine patients and in 43 of 51 episodes of events. Of the 17 episodes of monomorphic VT detected in the VT zone, 16 (94%) were terminated by antitachycardia pacing. Thirty episodes of monomorphic VT were detected in the VF zone and were terminated by defibrillation.
Conclusion: Sustained monomorphic VT is common in a high-risk cohort with HCM. Sinus tachycardia is often the initiating rhythm, suggesting that high sympathetic drive may be proarrhythmic when a susceptible substrate is present. Antitachycardia pacing is highly effective in terminating VT in this patient population.     

Double atrial responses to a single ventricular impulse due to simultaneous conduction via two retrograde pathways

Electrophysiologic studies were performed in two patients. In one patient (Case 1) with ventricular pre-excitation and paroxysmal supraventricular tachycardia, studies after diltiazem administration showed two QRS responses to a single atrial stimulus during atrial pacing at a cycle length of 300 ms. The first QRS response with full pre-excitation and short PR interval was consistent with accessory pathway conduction, while the second QRS response with a normal duration and an atrio-His bundle interval of 350 ms was consistent with normal pathway conduction. The second QRS response was followed by initiation of supraventricular tachycardia. Studies after verapamil administration on a separate day disclosed two atrial responses to a single QRS complex during ventricular pacing at cycle lengths between 330 and 280 ms, suggesting simultaneous retrograde accessory and normal pathway conduction. In Case 2 with a supraventricular tachycardia using a fast atrioventricular nodal pathway for anterograde and a slow ventriculoatrial pathway for retrograde conduction, two atrial responses to a single QRS complex were observed during ventricular pacing at cycle lengths between 500 and 400 ms. The first atrial response showed a stimulus to atrial interval of 120 ms and an atrial activation sequence with the low septal right atrium being earlier than other atrial sites, suggesting retrograde fast pathway conduction. The second atrial response showed a stimulus to atrial interval of 505 ms and an atrial activation sequence with low septal right atrium being simultaneous with the proximal coronary sinus, suggesting retrograde slow pathway conduction.(ABSTRACT TRUNCATED AT 250 WORDS)     

Use of Propafenone in Patients With Supraventricular Tachycardia

Propafenone prolongs refractoriness and slows conduction of the atrium, atrioventricular node, and accessory atrioventricular pathway. By interfering with conduction in locations necessary to support supraventricular tachycardia, propafenone effectively treats several mechanisms of rhythm disturbance. Early experience shows that propafenone, when administered in the electrophysiology laboratory, effectively terminates or prevents reinduction of paroxysmal supraventricular reentrant tachycardia in 50% to 75% of patients. The most effective dose associated with the fewest side effects has been 2 mg/kg infused over 10 minutes. Long-term success with propafenone has been demonstrated in patients with paroxysmal atrial fibrillation, paroxysmal atrial flutter, atrioventricular node reentrant tachycardia, atrioventricular reentrant tachycardia using a concealed accessory pathway, and tachycardias associated with the Wolff-Parkinson-White syndrome, including paroxysmal atrial fibrillation and atrioventricular reentrant tachycardia. In 67% (range, 27% to 89%) of patients receiving long-term therapy with propafenone, episodes of supraventricular tachycardia have been either eliminated or significantly reduced in frequency and treatment has not had to be stopped because of side effects. The effective daily dose for longterm therapy has been 550 to 750 mg administered in three or four divided doses. Although the number of patients reported in the literature at this time is small, propafenone appears to be an effective agent for treating supraventricular tachycardia due to one of several mechanisms.     

His束逆传不应期心室早搏刺激鉴别间隔隐匿性旁道与房室结折返性心动过速

探讨His束逆传不应期心室早搏刺激法临床应用时的注意事项。 37例慢 快型房室结折返性心动过速(AVNRT)和 2 0例间隔部隐匿性快旁道引起的房室折返性心动过速 (AVRT)患者 ,成功消融前在常规行腔内电生理检查的同时均行His束逆传不应期心室早搏刺激法。结果 :心动过速时His束逆传不应期内心室早搏刺激 ,37例AVNRT患者心房激动无明显提前 ,2 0例AVRT心房被提前激动超过 2 0 (30～ 5 0 )ms ,其中 9例终止心动过速 ,此方法鉴别AVRT和AVNRT特异度、灵敏度较高。结论 :心动过速时His束逆传不应期行心室早搏刺激法鉴别诊断AVRT和AVNRT操作简单、准确性高。但行此法检查时要求有持续发作的心动过速 ;能够标测出清晰的His束电位 ;心室早搏刺激最好与His束电位同步发放 ;反复多次重复检测以进一步提高诊断的正确性     

Electrophysiologic characteristics and radiofrequency ablation of concealed nodofascicular and left anterograde atriofascicular pathways

INTRODUCTION: True nodoventricular or nodofascicular pathways and left-sided anterograde decremental accessory pathways (APs) are considered rare findings. METHODS AND RESULTS: Two unusual patients with paroxysmal supraventricular tachycardia were referred for radiofrequency (RF) ablation. Both patients had evidence of dual AV nodal conduction. In case 1, programmed atrial and ventricular stimulation induced regular tachycardia with a narrow QRS complex or episodes of right and left bundle branch block not altering the tachycardia cycle length and long concentric ventriculoatrial (VA) conduction. Ventricular extrastimuli elicited during His-bundle refractoriness resulted in tachycardia termination. During the tachycardia, both the ventricles and the distal right bundle were not part of the reentrant circuit. These findings were consistent with a concealed nodofascicular pathway. RF ablation in the right atrial mid-septal region with the earliest atrial activation preceded by a possible AP potential resulted in tachycardia termination and elimination of VA conduction. In case 2, antidromic reciprocating tachycardia of a right bundle branch block pattern was considered to involve an anterograde left posteroseptal atriofascicular pathway. For this pathway, decremental conduction properties as typically observed for right atriofascicular pathways could be demonstrated. During atrial stimulation and tachycardia, a discrete AP potential was recorded at the atrial and ventricular insertion sites and along the AP. Mechanical conduction block of the AP was reproducibly induced at the annular level and at the distal insertion site. Successful RF ablation was performed at the mitral annulus. CONCLUSION: This report describes two unusual cases consistent with concealed nodofascicular and left anterograde atriofascicular pathways, which were ablated successfully without impairing normal AV conduction system.