Complete abolition of the reentrant supraventricular tachycardia zone using a new modality of cardiac pacing with simultaneous atrioventricular stimulation

In an attempt to prevent recurrent reentrant supraventricular tachycardia, an experimentally designed new pacemaker has been developed. The pacemaker, when connected to both atrial and ventricular electrodes, is capable of sensing either an atrial or ventricular signal and, in turn, triggers simultaneous atrioventricular (A-V) stimulation. Efficacy of this pacemaker was tested in four patients with recurrent paroxysmal A-V nodal reentrant tachycardia during electrpphysiologic studies. After connection of the electrodes to the new pacemaker, all atrial or ventricular premature stimuli elicited simultaneous A-V stimulation with resultant impulse collision in the A-V junction. Consequently, the reentrant tachycardia zone was completely abolished in all patients. This study has thus demonstrated the clinical feasibility of simultaneous A-V pacing to abolish the supraventricular tachycardia zone in man.     

Combined bipolar dual chamber pacing and automatic implantable cardioverter/defibrillator

A 67 year old man with recurrent hypotensive ventricular tachycardia, amiodarone-induced bradyarrhythmias and severe cardiac dysfunction underwent simultaneous implantation of an automatic cardioverter/defibrillator and bipolar atrioventricular (AV) pacemaker. The pacing electrodes were placed epicardially near the right atrial appendage and on the lateral right ventricular wall. The rate detector of the automatic defibrillator was placed epicardially on the posterobasal left ventricular wall. Effective bipolar AV pacing produced no false counting of the heart rate by the automatic cardioverter/defibrillator, and ventricular tachycardia properly inhibited the pacemaker. Long-term follow-up study confirmed the safety of this treatment. With proper precautions, bipolar AV pacing can be safely combined with an automatic cardioverter/defibrillator.     

Multiple syncope mechanisms coexisting in a Brugada syndrome patient requiring a single therapeutic approach

We report the case of a Brugada syndrome patient with a history of syncopal and presyncopal episodes and evidence of sinus node and atrioventricular (AV) conduction abnormalities. The patient developed sinus bradycardia, sinoatrial conduction abnormalities, prolonged HV interval, early appearance of AV block, AV nodal reentrant tachycardia and polymorphic ventricular tachycardia in the electrophysiological study. He was treated with a dual-chamber pacemaker defibrillator. At the 9-year follow-up, the patient remained asymptomatic with several episodes of 1:1 AV-relationship tachycardia, interrupted with antitachycardia pacing, while the predominant pacing states of the device were AP-VS and AS-VP for most of the time.     

Sino-atrial syncope

Thirteen patients are described in whom cardiovascular syncope occurred due to disorder of sino-atrial conduction and depression of the atrioventricular (A-V) junctional escape pacemaker system. Significant atrioventricular block was not present in these patients. Two mechanisms of cardiac slowing were observed. Type I sino-atrial syncope was characterized in six patients by severe sino-atrial block and bradycardia. Type II sino-atrial syncope was characterized in seven patients who experienced periods of bradycardia and tachycardia, with asystole and syncope occurring at the termination of the tachycardia. In one of these patients it occurred transiently after an acute myocardial infarction. In twelve patients, sinoatrial syncope was a chronic and recurrent problem, and in eleven of these it was treated successfully with ventricular demand pacing.     

VDD起搏治疗幼儿完全性房室阻滞(附一例报告)

一例３．５岁的女性幼儿因室间隔缺损修补术致迟发性完全性房室阻滞（ＣＡＶＢ）而安置ＶＤＤ起搏器。经锁骨下静脉途径埋置单根心房感知、心室触发起搏电极，使之于右房内塑形并贴靠房壁；起搏器埋于同侧皮下胸大肌筋膜上囊袋内。术中测得起搏阈值０．１Ｖ、脉宽０．４ｍｓ、电极阻抗５２０Ω、Ａ波振幅１．５ｍＶ、Ｖ波振幅１０．６ｍＶ，Ａ波感知设定０．２５ｍＶ。术后房室同步起搏率１００％，临床症状改善。表明ＶＤＤ起搏器不仅埋置简便，而且具有房室同步、频率应答等生理性起搏特点，是治疗幼儿ＣＡＶＢ的理想起搏方式。     

The contribution of artificial pacemaking to understanding the pathogenesis of arrhythmias

Right atrial or ventricular pacing was performed on 36 occasions in 26 patients in an attempt to terminate a variety of tachyarrhythmias. Of 16 episodes of atrial flutter, 13 were terminated successfully; in 9 of the 13, sinus rhythm or the patient's pre-flutter rhythm was restored immediately, whereas in 4 patients, intervening atrial fibrillation or unstable atrial flutter occurred. Pacing terminated paroxysmal atrioventricular junctional or paroxysmal atrial tachycardia on 3 occasions; in a fourth patient, this tachyarrhythmia terminated during catheter manipulation. Six episodes of pacemaker-induced ventricular tachycardia were abolished by ventricular pacing. In 2 patients, atrial tachycardia was only transiently suppressed, and in 1 of these patients, d-c cardioversion produced a similar effect. Atrial fibrillation, spontaneously converting to atrial flutter, resulted during pacing for atrial tachycardia with block; the latter arrhythmia returned when the atrial flutter was terminated. Atrial fibrillation in 7 patients remained unaffected by atrial pacing. Based on the different electrophysiologic mechanisms responsible for reentrant excitation and automatic pacemaker discharge, an attempt has been made to determine the pathogenesis of the tachyarrhythmia by its response to pacing.     

Exercise capacity and spontaneous heart rhythm after transvenous fulguration of atrioventricular conduction.

Twenty nine patients who had had refractory supraventricular tachycardia were studied 4-36 (mean 16) months after transvenous fulguration of the atrioventricular junction. Twenty two had complete atrioventricular block, five partial atrioventricular block, and two had atrioventricular conduction via an accessory atrioventricular pathway. Though all patients were free of palpitation after the procedure, exertional dyspnoea had developed in 13 and in two patients pre-existing dyspnoea had worsened. During ventricular demand pacing, exercise time was reduced to 43% of the predicted value for their age and sex. The 16 patients with rate responsive pacemakers demonstrated a significantly better but still impaired exercise capacity during "physiological" pacing as compared with their performance during constant rate pacing. In patients with complete atrioventricular block there was an increase in spontaneous ventricular rate during exercise in seven patients and in response to the Valsalva manoeuvre in eight patients. This suggests that the intrinsic ventricular pacemaker is influenced by autonomic nervous system activity in some patients. It is concluded that though transvenous fulguration is successful in controlling tachycardia it may reduce exercise capacity. Most patients remain in complete atrioventricular block after the procedure and, in contrast with the practice as described in early reports, would benefit from "physiological" pacing--though even with this mode exercise capacity is likely to be abnormal.     

Double blind crossover comparison of the effects of dual chamber pacing (DDD) and ventricular rate adaptive (VVIR) pacing on neuroendocrine variables, exercise performance, and symptoms in complete heart block.

OBJECTIVE--To compare the effects of dual chamber pacing (DDD) and ventricular rate adaptive pacing (activity sensing) (VVIR) in patients with complete heart block. DESIGN--Double blind crossover comparison with one month in each pacing mode. PATIENTS--10 consecutive patients aged 23-74 presenting with complete anterograde atrioventricular block at rest and on exercise and with an intact atrial rate response received Synergyst I (Medtronic) pacemakers. MAIN OUTCOME MEASURES--Symptom scores, maximal exercise performance on a treadmill, and the plasma concentrations of atrial natriuretic peptide, adrenaline, and noradrenaline. RESULTS--No significant differences were identified between pacing modes in symptom scores for dyspnoea, fatigue, and mood disturbance; exercise time; and maximal oxygen consumption. One patient with intact ventriculoatrial conduction developed pacemaker syndrome during VVIR pacing. Resting plasma concentrations of atrial natriuretic peptide were raised in complete heart block and were restored to normal by DDD pacing but not by VVIR pacing. Resting plasma catecholamine concentrations were normal in complete heart block and in both pacing modes. During exercise the increase in the concentrations of all three hormones was similar in both pacing modes. CONCLUSIONS--In patients with complete anterograde and retrograde atrioventricular block, symptoms and maximal exercise performance were no better during DDD than during VVIR pacing.     

Double blind crossover comparison of the effects of dual chamber pacing (DDD) and ventricular rate adaptive (VVIR) pacing on neuroendocrine variables, exercise performance, and symptoms in complete heart block.

OBJECTIVE--To compare the effects of dual chamber pacing (DDD) and ventricular rate adaptive pacing (activity sensing) (VVIR) in patients with complete heart block. DESIGN--Double blind crossover comparison with one month in each pacing mode. PATIENTS--10 consecutive patients aged 23-74 presenting with complete anterograde atrioventricular block at rest and on exercise and with an intact atrial rate response received Synergyst I (Medtronic) pacemakers. MAIN OUTCOME MEASURES--Symptom scores, maximal exercise performance on a treadmill, and the plasma concentrations of atrial natriuretic peptide, adrenaline, and noradrenaline. RESULTS--No significant differences were identified between pacing modes in symptom scores for dyspnoea, fatigue, and mood disturbance; exercise time; and maximal oxygen consumption. One patient with intact ventriculoatrial conduction developed pacemaker syndrome during VVIR pacing. Resting plasma concentrations of atrial natriuretic peptide were raised in complete heart block and were restored to normal by DDD pacing but not by VVIR pacing. Resting plasma catecholamine concentrations were normal in complete heart block and in both pacing modes. During exercise the increase in the concentrations of all three hormones was similar in both pacing modes. CONCLUSIONS--In patients with complete anterograde and retrograde atrioventricular block, symptoms and maximal exercise performance were no better during DDD than during VVIR pacing.     

Improved method for evaluating ventriculoatrial conduction before implantation of atrial-sensing dual chamber pacemakers

Pacemaker-mediated tachycardia may occur when a spontaneous ventricular premature depolarization is retrogradely conducted to the atrium with a ventriculoatrial (VA) interval that exceeds the atrial refractory period of an atrial-sensing dual chamber pacemaker. Previous methods for evaluating VA conduction have failed to predict clinical occurrences of pacemaker-mediated tachycardia. In this study, maximal VA intervals after ventricular extrastimuli during atrial or atrioventricular (AV) sequential pacing were compared with intervals measured by the standard method of ventricular pacing. VA intervals were 201 +/- 53 ms during ventricular pacing and 224 +/- 52 ms after ventricular extrastimuli during atrial pacing (p = NS). VA intervals were 305 +/- 77 ms after ventricular extrastimuli during AV sequential pacing and were longer than VA intervals during ventricular pacing (p less than 0.001) or after ventricular extrastimuli during atrial pacing (p less than 0.01). Thus, the ventricular extrastimulus technique during AV sequential pacing reveals substantially longer VA intervals than does ventricular pacing and explains why pacemaker-mediated tachycardia might occur when pacemaker atrial refractory periods are designed or programmed according to VA intervals measured only during ventricular pacing.     

Prenatal diagnosis of polymorphic ventricular tachycardia using 64-channel magnetocardiography

We describe polymorphic ventricular tachycardia (VT) diagnosed using fetal magnetocardiography (FMCG). The fetus of a 33-year-old Japanese female at 24 weeks of pregnancy was diagnosed as bradycardia (60 beats/min) by fetal cardiotocography (CTG). Ultrasound findings indicated a diagnosis of an atrioventricular (AV) block involving extrasystole, but FMCG revealed a polymorphic VT followed by ventricular asystole. Standard ECG immediately after cesarean section at 37 weeks of pregnancy confirmed long QT syndrome followed by nonsustained polymorphic VT and an advanced AV block with wide QRS. Echocardiography demonstrated moderate left ventricular dysfunction in the neonate requiring implantation with a permanent pacemaker.     

Exercise capacity and spontaneous heart rhythm after transvenous fulguration of atrioventricular conduction

Twenty nine patients who had had refractory supraventricular tachycardia were studied 4-36 (mean 16) months after transvenous fulguration of the atrioventricular junction. Twenty two had complete atrioventricular block, five partial atrioventricular block, and two had atrioventricular conduction via an accessory atrioventricular pathway. Though all patients were free of palpitation after the procedure, exertional dyspnoea had developed in 13 and in two patients pre-existing dyspnoea had worsened. During ventricular demand pacing, exercise time was reduced to 43% of the predicted value for their age and sex. The 16 patients with rate responsive pacemakers demonstrated a significantly better but still impaired exercise capacity during "physiological" pacing as compared with their performance during constant rate pacing. In patients with complete atrioventricular block there was an increase in spontaneous ventricular rate during exercise in seven patients and in response to the Valsalva manoeuvre in eight patients. This suggests that the intrinsic ventricular pacemaker is influenced by autonomic nervous system activity in some patients. It is concluded that though transvenous fulguration is successful in controlling tachycardia it may reduce exercise capacity. Most patients remain in complete atrioventricular block after the procedure and, in contrast with the practice as described in early reports, would benefit from "physiological" pacing--though even with this mode exercise capacity is likely to be abnormal.     

Écoute croisée atrioventriculaire sur sondes unipolaires et pauses ventriculaires syncopales

In this article, we describe a case of ventricular asystole in a patient implanted with a cardiac pacemaker. The patient had a device replacement. The new pacemaker has been connected to old unipolar leads. The detection has been, inadvertently, programmed in a bipolar mode. This programmation induced an inhibition of the atrial and ventricular pacing due to oversensing of myopotentials. An inhibition of ventricular stimulation has been recorded also because of ventricular detection of the unipolar atrial stimulation (atrioventricular crosstalk). Lack of ventricular stimulation induced in this dependant patient ventricular asystole and syncope.     

Ventricular capture by anodal pacemaker stimulation.

This report describes the case of an 86-year-old male with syncopal paroxysmal 2:1 atrioventricular block and a single chamber VVI pacemaker programmed to bipolar sensing and unipolar pacing. After recurrence of syncope, a complete loss of ventricular capture with regular ventricular sensing was observed on ECG; fluoroscopic examination suggested perforation of the right ventricle by the helix of the implanted screw-in lead. Reprogramming the pacemaker to bipolar pacing/sensing resulted in regular ventricular capture and sensing, suggesting effective anodal stimulation from the ring electrode permitting complete non-invasive palliation.     

Successful treatment of drug-resistant atrial tachycardia and intractable congestive heart failure with permanent coupled atrial pacing

Temporary coupled atrial stimulation slowed the ventricular rate by nearly 50% in an adolescent patient with intractable congestive heart failure and focal repetitive atrial tachycardia that was resistant to drug treatment. Because of the success with the temporary pacemaker, a specially designed permanent pacemaker was implanted to provide coupled atrial stimulation. The necessary electrophysiologic conditions for ventricular slowing by coupled atrial pacing are: (1) an atrial effective refractory period shorter than that of the atrioventricular junction, and (2) depolarization of the ectopic atrial pacemaker by the responses to coupled atrial stimulation. During a 4 year follow-up period the treatment resulted in elimination of the tachycardia, followed by return of the heart size to normal and complete clinical recovery. Coupled atrial stimulation can provide effective treatment in selected patients with disabling drug-resistant atrial tachycardia in whom this mode of therapy is shown to be effective by careful electrophysiologic studies.     

Atrial tracking (synchronous) pacing in a pediatric and young adult population

One hundred pediatric and young adult patients underwent implantation of an atrial tracking pacemaker. Seventy-four pacemakers paced in an atrioventricular (AV) sequential mode at the lower rate limit (DDD) while 26 paced in a ventricular demand mode at the lower rate limit (VDD). Five patients required reoperation during follow-up of 1 month to 2.5 years (mean 1.5 years). Six additional patients required programming to ventricular demand (3) or AV sequential (3) pacing, because of development of sinus bradycardia (2), atrial sensing problems (1) or pacemaker-mediated tachycardia (3). Pulse generators that could sense atrial signals less than 1.0 mV and had a programmable atrial refractory period did not require reprogramming out of the atrial tracking mode. No patient developed atrial flutter or fibrillation. Sensing problems during exercise occurred in 37% of the first 60 pacemakers but in none of the last 40, which had improved electronic components. Atrial tracking pacing is feasible in pediatric and young adult patients.     

Clinical Results with Catheter Ablation: AV Junction, Atrial Fibrillation and Ventricular Tachycardia

With the limitations of pharmacologic and device therapies for atrial fibrillation and ventricular tachycardia, catheter ablation is assuming a larger role in the management of patients with these common arrhythmias. Multiple case series and clinical trials have helped to define the evolving role of these techniques for ablation of the atrioventricular node, atrial fibrillation, and ischemic ventricular tachycardia. Based on very low complication rates, excellent efficacy and proven outcomes with radiofrequency ablation of the atrioventricular node, this approach with permanent pacing should play a larger role in the treatment of symptomatic patients with permanent atrial fibrillation. While linear ablation of atrial fibrillation has limited clinical utility for the treatment of this common arrhythmia, the results of multiple case series of focal atrial fibrillation ablation indicate the potential for an expanding role of this curative technique. Catheter ablation techniques for ventricular tachycardia in the setting of coronary artery disease have a role as supplemental therapy to the implantable cardioverter defibrillator in patients with recurrent pharmacologically refractory ventricular arrhythmias requiring frequent device interventions.     

置入双腔起搏心脏复律除颤器及经腋静脉送入心内电极的初步临床体会

目的初步评价新型双脏起搏心脏复律除颤器抗室性心动过速／心室颤动（室速／室颤）及心动过缓起搏的临床效果,了解经腋静脉送人心房及心室电极的安全性及有效性。方法７例室速及（或）室颤同时伴有心动过缓患者接受了双腔起搏心脏复律除颤器治疗,其中冠心病５例、扩张性心肌病２例。心房及心室电极均在Ｘ线透视、静脉注人造影剂指导下,直接穿刺腋静脉,从该静脉送人。结果脉冲发生器埋在左上胸皮下５例,埋在胸大肌与胸小肌之间２例。仪器对所有室速／室颤均能及时识别并成功治疗,同时提供有效的房室顺序起搏功能。所有心内电极均成功地经腋静脉送人,无并发症。结论双腔起搏心脏复律除颤器不但能有效地治疗严重室性心律失常,而且提供可靠的房室顺序性起搏功能。经腋静脉送入电极安全、可靠。