Sustained improvement in exercise tolerance following physiological cardiac pacing

Fifty-three patients have received ‘physiological’pacemakers,37 with atrioventricular (AV) block having atrial synchronousunits (VAT or VDD) implanted and the remaining 16 patients withboth AV block and sick sinus syndrome having ‘universal’(DDD) pacemakers. Effort tolerance was assessed by serial bicycleergometry and in 16 patients direct comparisons between ventricularpacing and atrial synchronous pacing could be made acutely.Physiological pacemakers were found to increase maximum efforttolerance by 43% compared to pre-pacing values (P<0.01).The increase was sustained over a mean of 33 months post pacing.The atrial synchronous mode increased maximum effort toleranceby 34% acutely compared to ventricular inhibited pacing. Dualchambered ‘physiological’ pacemakers represent asignificant therapeutic advance over standard ventricular inhibitedpacemakers.     

一种新的双腔起搏模式——AAISafeR与DDD模式的对比临床研究

目的评价存在自身房室传导置入双腔起搏器的患者,分别以DDD模式和AAISafeR模式工作3个月后心室起搏百分比以及临床指标。方法因病窦综合征置入Ela Symphony D 2450 DR2550系列双腔起搏器的患者30例,随机分为两组DDD组和AAISafeR组,3个月后交叉程控为AAISafeR和DDD,再随访3个月。结果没有观察到与AAISafeR有关的不良反应;AAISafeR模式能显著降低心室起搏的百分比51.3%(2%～91%)与0.9%(0～3%),(P=0.001);2.94%(0～18%)与41.18%(0～65%),(P=0.000);DDD模式工作3个月,左房直径、左室舒张末径、左室收缩末径均比术前增加,左室射血分数降低,差异有显著性,AAI SafeR模式工作3个月,除左房内径明显增大外,其余指标无明显改变;30例患者,在6个月的随访中,21例因不同程度的房室传导阻滞,AAI模式暂时转换为DDD模式。结论AAISafeR起搏模式能够有效降低心室起搏的百分比;AAISafeR起搏模式能够在出现房室传导阻滞的情况下,迅速安全的转换为DDD模式。     

病窦综合征患者AAI和VVI起搏的远期随访分析

分析并比较病窦综合征 (SSS)患者AAI和VVI起搏的远期效果。对 1 4 0例AAI起搏、4 3例VVI起搏的SSS患者进行定期随访并行临床、心电图和Holter检查。结果 :随访 5 2± 4 .3(6～ 1 4 4 )个月 ,AAI组发生间歇性文氏型房室阻滞 (AVB) 1例。VVI起搏组阵发性房性心律失常、持续性心房颤动、脑栓塞、心源性死亡的发生率明显较AAI组高(分别为 39.5 3%vs 5 .71 %、1 8.6 0 %vs 1 .4 3%、9.3%vs 0 .71 %、1 1 .6 3%vs 0 .71 % ,P均 <0 .0 1 )。快速房性心律失常的发生率VVI组明显增加 (39.5 3%vs 1 8.6 0 % ,P <0 .0 1 ) ,AAI组明显减少 (5 .71 %vs 1 8.5 7% ,P <0 .0 1 )。无 1例近期和远期电极脱位。结论 :AAI起搏时远期AVB和电极脱位发生率很低 ,并且快速性房性心律失常、脑栓塞、心源性死亡事件的发生率低于VVI起搏     

不同起搏模式对病态窦房结综合征患者心功能长期影响的探讨

目的前瞻性观察不同起搏模式对心功能长期的影响并探讨可能机制。方法 185例病态窦房结综合征（SSS）患者均采用常规方法经锁骨下静脉途径成功置入永久双腔心脏起搏器,术后即刻程控起搏器,根据SAS软件的PROC程序产生一组随机序列分为AAI（92例）及DDD（93例）起搏组。采用心脏超声观察术前,术后1、2、5年左室舒张末容积（LVEDV）、左室收缩末容积（LVESV）及左室射血分数（LVEF）的变化,比较两种起搏模式对左心功能的影响;术后1、2及5年进行随访结合起搏器程控记录房颤发生并记录DDD起搏组右室起搏百分比（VP%）,探讨VP%与心功能变化及房颤发生的关系。结果 AAI起搏组术前,术后1、2、5年随访LVEDV,LVESV及LVEF比较差异无统计学意义（P〉0.05）,DDD起搏组术前、术后1、2、5年LVEDV差异无统计学意义（P〉0.05）,术后5年LVESV（60.33±13.28）ml较术后1、2年增加,差异有统计学意义（F=2.7388,P〈0.05）,术后5年LVEF（41.75±8.74）%较术前、术后1、2年明显降低,差异有统计学意义（F=33.4393,P〈0.05）;AAI组与DDD组房颤的发生差异有统计学意义（P〈0.05）。术后5年DDD组中〈50%VP%,组中出现房颤患者为3例,≥50%VP%组中出现房颤患者为15例,两组之间房颤的发生率差异有统计学意义（P〈0.05）。结论在DDD起搏模式下,高的VP%可对患者的左心功能造成损害并增加房颤的发生。对于不合并房室传导阻滞的SSS患者,AAI起搏较DDD起搏能使患者更受益。     

AAI pacing mode: When is it indicated and how should it be achieved?

AAI pacing offers better hemodynamic characterstics than dual-chamber pacing and is the optimal mode for patents with sick sinus syndrome without AV conduction disorders. AAI pacing may be achieved by single-chamber atrial, by programming a dual-chamber pacemaker to the AAI mode, or by programming a dual-chamber pacemaker to DDD mode with a long AV delay. The annual incidence of AV block development in patients with sick sinus syndrome is low, probably 1-5%, but there is no method of detecting patients immune to future development of AV block. Chronotropic is often present in patients with sick sinus but the value of additional rate response is not yet established. Our recommendations for the choice of the method of pacing are discussed.     

预防病态窦房结综合征心房颤动的心脏起搏模式探讨

目的 :观察何种心脏起搏模式能有效预防病态窦房结 (病窦 )综合征心房颤动 (房颤 )的发作。方法 :对 4 5例安置心房按需起搏器 (AAI)及房室顺序起搏器 (DDD)的病窦综合征房颤患者进行了平均 3.3年的随访观察。结果 :4 5例病窦患者仅 1例出现房颤 (2 .2 % )。对 5个典型病例进行分析的结果提示 ,超速持续心房起搏可以抑制病窦患者房颤的发生。结论 :心脏起搏抑制房颤发生的机制可能与快频率起搏加速心房内传导、抑制了房性期前收缩、消除了窦性心动过缓和心脏长 短间歇有关。双心房或AA起搏方式可能是一种比较理想的预防房颤的方法     

AAI与DDD起搏对病窦综合征患者的影响

目的比较AAI与DDD起搏方式对有正常房室传导功能的病窦综合征患者预后的长期影响。方法104例因病窦综合征置入起搏器的患者,按不同起搏方式分为两组:AAI组36例,DDD组68例。术后随访内容包括起搏器程控,患者的症状、体征,心电图和/或动态心电图,超声心动图及心功能分级(NYHA)。主要终点为心房颤动(简称房颤)的发生率,次要终点为脑卒中的发生率,心功能分级及超声心动图检查指标。结果随访43.2±15.7(21～79)个月,①DDD组房颤发生率明显高于AAI组(20.6%vs5.6%,P<0.05),而脑卒中发生率无差异(7.4%vs2.8%,P>0.05);②左房内径、左室舒张末期内径和左室射血分数在AAI组置入前后无差异,而DDD组术后左房内径、左室舒张末期内径增大,左室射血分数下降(P均<0.05);③AAI组与DDD组比较,对心功能影响较小。结论对于房室传导功能正常的病窦综合征患者,与DDD起搏比较,AAI起搏房颤发生率较低,对心功能影响较小,更符合生理性。     

The role of pacing mode in the development of atrial fibrillation.

Asynchronous ventricular pacing has been shown to increase the risk of development of atrial fibrillation (AF) because of various mechanisms: retrograde atrioventricular (AV) conduction with increase in atrial pressure causing acute atrial stretch and reverse flow in the pulmonary veins, mitral regurgitation, reduced coronary blood flow, adverse neuroendocrine reactions, etc. Dual-chamber pacing preserves atrioventricular synchrony. However, in randomized multicentre trials comparing VVI(R) with DDD(R) pacing, AF is only slightly less frequent in the dual-chamber mode. This is most likely due to unnecessary ventricular pacing, which is frequent in dual-chamber pacing. At nominal values, dual-chamber devices usually do not permit intrinsic AV conduction but promote delivery of the ventricular stimulus at an inappropriate time in an inappropriate place. Programming of long AV delays facilitates spontaneous AV conduction but usually cannot completely avoid unnecessary ventricular pacing and causes other problems in the dual-chamber mode. Atrial septal lead placement can improve left-sided AV synchrony and promote spontaneous AV conduction. Programming of the AAI(R) mode is superior to the dual-chamber mode but cannot be used if AV conduction is impaired intermittently or permanently. Therefore, dedicated algorithms enhancing spontaneous AV conduction in the dual-chamber mode are desirable for a large proportion of pacemaker patients.     

Acquired atrioventricular block in a patient with sinus node disease on single-chamber atrial pacing

Single-chamber atrial pacing is the most physiological and yet economical modality of treatment in patients with symptomatic sinus node disease with normal atrioventricular conduction. However, because of the possibility of future development of a high-degree atrioventricular block and atrial fibrillation, most patients are implanted either dual- or single-chamber right ventricular pacemakers. We report a patient with symptomatic sinus node disease on single-chamber atrial pacing for the past 7 years who developed a progressive increase in the PR interval and ultimately presented with symptomatic high-degree atrioventricular block requiring pacemaker upgradation. The pacemaker was upgraded to the single-chamber ventricular mode with one additional ventricular lead introduced from the same side percutaneously.     

Comparison of atrial and VVI pacing modes in symptomatic sinus node dysfunction without associated tachyarrhythmias

The natural course of patients with symptomatic sinus node dysfunction who did not have associated tachyarrhythmias before pacemaker implantation was compared after VVI and atrial pacemaker implantation. Between April 1981 and June 1989, forty-seven such patients (mean age 52 + 13 years) received VVI pacemakers and forty patients (mean age 54 + 13 years) received AAI or DDD pacemakers. Baseline clinical characteristics and severity of sinus node dysfunction were comparable in the two groups. Over a follow up of 10 to 96 months (mean 49.2 + 26 months), 11 (23.4%) VVI patients were in functional class II or more compared to 2 (5%) atrially paced patients (p less than 0.01). Other complication rates were also higher in the VVI group as compared to AAI group viz. atrial fibrillation (21.2% vs 2.5% p less than 0.01) and stroke (10.6% vs 2.5%) though the number of deaths (14.9% vs 10%) was not significantly different in the two groups. Two patients in atrial paced group and one patient in VVI group developed first degree heart block. There was no incidence of second or third degree heart block. Transient loss of atrial sensing occurred in 3 patients and atrial lead displacement in 2 cases, but overall incidence of lead related problems was low and comparable in both groups. Thus atrial pacing is superior to ventricular pacing in sinus node dysfunction and risk of developing high grade atrioventricular block on follow up is low.     

Multicenter, prospective, randomized safety and efficacy study of a new atrial-based managed ventricular pacing mode (MVP) in dual chamber ICDs

BACKGROUND: Ventricular desynchronization caused by right ventricular pacing may impair ventricular function and increase risk of heart failure (CHF), atrial fibrillation (AF), and death. Conventional DDD/R mode often results in high cumulative percentage ventricular pacing (Cum%VP). We hypothesized that a new managed ventricular pacing mode (MVP) would safely provide AAI/R pacing with ventricular monitoring and DDD/R during AV block (AVB) and reduce Cum%VP compared to DDD/R. METHODS: MVP RAMware was downloaded in 181 patients with Marquis DR ICDs. Patients were initially randomized to either MVP or DDD/R for 1 month, then crossed over to the opposite mode for 1 month. ICD diagnostics were analyzed for cumulative percentage atrial pacing (Cum%AP), Cum%VP, and duration of DDD/R pacing for spontaneous AVB. RESULTS: Baseline characteristics included age 66 +/- 12 years, EF 36 +/- 14%, and NYHA Class II-III 36%. Baseline PR interval was 190 +/- 53 msec and programmed AV intervals (DDD/R) were 216 +/- 50 (paced)/189 +/- 53 (sensed) msec. Mean Cum%VP was significantly lower in MVP versus DDD/R (4.1 +/- 16.3 vs 73.8 +/- 32.5, P < 0.0001). The median absolute and relative reductions in Cum%VP during MVP were 85.0 and 99.9, respectively. Mean Cum%AP was not different between MVP versus DDD/R (48.7 +/- 38.5 vs 47.3 +/- 38.4, P = 0.83). During MVP overall time spent in AAI/R was 89.6% (intrinsic conduction), DDD/R 6.7% (intermittent AVB), and DDI/R 3.7% (AF). No adverse events were attributed to MVP. CONCLUSIONS: MVP safely achieves functional atrial pacing by limiting ventricular pacing to periods of intermittent AVB and AF in ICD patients, significantly reducing Cum%VP compared to DDD/R. MVP is a universal pacing mode that adapts to AVB and AF, providing both atrial pacing and ventricular pacing support when needed.     

107例心脏永久起搏器植入分析

目的:观察107例不同模式起搏器植入的疗效及并发症。方法:对107例不同模式的永久心脏起搏器植入患者进行随访观察,对术中疗效及术后各种并发症进行分析。结果:不同模式心脏永久起搏治疗均能显著改善患者症状 (总有效率97．1％)。生理性起搏(DDD及AAI模式)的治疗效果优于非生理起搏(VVI模式),分别增加左室射血分数48．3％,6．9％(P<0．01);手术并发症二者相仿,但非手术并发症VVI(7．9％)明显多于DDD及AAI模式 (4．6％)。结论:心脏永久起搏能有效改善缓慢心律失常患者的心功能,DDD及AAI模式优于VVI模式。     

Prevalence of atrial fibrillation and stroke in paced patients without prior atrial fibrillation: A prospective study

Background: Several reports suggest that the incidence of stroke and atrial fibrillation is reduced in patients receiving physiologic pacemakers, compared with patients receiving a ventricular pacemaker. Hypothesis: The study was undertaken to address the impact of different pacing modalities on the incidence of stroke and atrial fibrillation. Methods: We prospectively analyzed 210 consecutive patients. Those with previous episodes of cerebral ischemia and/ or atrial fibrillation were excluded from the study. The study population included 100 patients paced for total atrioventricular (AV) block or second-degree AV block (type II Mobitz) and 110 patients paced for sick sinus syndrome (SSS). The pacing mode was randomized. All patients underwent a brain computed tomography (CT) scan at the date of enrollment and after 1 and 2 years. Patients were followed for 2 years, and the incidence of atrial fibrillation and stroke was evaluated. Results: The incidence of atrial fibrillation was 10% at 1 year and 11% at 2 years. Comparing the different pacing modalities, we reported an increase in the incidence of atrial fibrillation in patients receiving ventricular pacing (p<0.05). On the other hand, no difference was found between patients paced for AV block and those paced for SSS. At the end of follow-up, we reported 29 cases of cerebral ischemia: 9 patients had AV block while 20 had SSS (p<0.05). Comparing the different pacing modalities, there was an increase in the incidence of stroke in patients receiving ventricular pacing (p< 0.05). Conclusion: There was an increase in the incidence of stroke and atrial fibrillation in patients with ventricular pacing.     

Atrial rate-responsive pacing in sinus node disease

Patients with sinus node disease (SND) who are unable to achieve an adequate increase in heart rate during exercise are candidates for atrial rate-responsive pacing (AAI-R). We have implanted 40 AAI-R systems in SND patients with an average follow-up of 12.5 +/- 8 (range 3-30) months. All the patients received an activity-sensing pulse generator (Activitrax, Medtronic or Sensolog, Siemens-Pacesetter) with a single atrial lead. Only patients with an intraoperative AV nodal block cycle-length above 100 beats min-1 were included. During follow-up, one patient was observed to have transient asymptomatic 2:1 AV-block during sleep. No patient developed persistent AV-block or chronic atrial fibrillation. Twelve patients with persistent chronotropic incompetence were assigned for a randomized double-blind crossover study, comparing exercise treadmill capacity in AAI-R with conventional atrial inhibited pacing (AAI). During AAI-R pacing the maximum heart rate during exercise was 120 +/- 1 beats min-1 compared with 97 +/- 21 beats min-1 during AAI pacing (P less than 0.01). The average exercise time increased from 11.2 +/- 2 min during AAI-pacing to 13.4 +/- 3 min during AAI-R pacing (P less than 0.01). AAI pacing should be considered for patients with SND and chronotropic incompetence.     

VVI与AAI起搏对病态窦房结综合征合并阵发性房性快速心律失常的影响

目的比较ＶＶＩ与ＡＡＩ起搏对病态窦房结综合征（病窦综合征）合并阵发性房性快速心律失常的远期影响。方法分别对４１和３８例病窦综合征合并阵发性房性心律失常的患者行ＶＶＩ和ＡＡＩ起搏,术后进行了临床、心电图、２４小时动态心电图的定期随访,随访时间分别为３９±２．６和２４±１．８个月。结果ＶＶＩ组２１例（５１．２％）发展成持续性心房颤动,２０例阵发性房性心律失常发作次数及持续时间较术前显著增加（Ｐ＜０．０５）,６例（１４．１％）出现血栓栓塞,无１例死亡,无电极移位等并发症。ＡＡＩ组,所有患者生活质量明显改善,１９例（５０％）阵发性心房颤动、心房扑动发作的频度及持续时间较术前显著减少（Ｐ＜０．０５）,无１例发展为持续性心房颤动、血栓栓塞和死亡,１例（３％）出现电极移位,１例（３％）出现一度房室阻滞。结论ＡＡＩ起搏是一种安全、可靠的起搏方式,对病窦综合征合并的阵发性房性心律失常有明显的抑制作用,显著优于ＶＶＩ。     

DDD and single-lead VDD pacing: evaluation of atrial signal dynamic changes

BACKGROUND: Single-lead VDD pacing systems are an alternative to conventional DDD pacemakers in patients with atrioventricular (AV) block and normal sinus function. HYPOTHESIS: The aim of this study was to assess changes of P-wave amplitude occurring in dynamic conditions in two groups of patients with a single-lead VDD and with a DDD pacing system, respectively. METHODS: Twenty-eight patients with second- or third-degree AV block and normal sinus function were enrolled prospectively into the study. Seventeen patients were implanted with a single-lead VDD pacing system and 11 with a DDD pacemaker. Patients were evaluated at 3 months (all patients) and at 6 months (26 patients) at supine and in dynamic conditions (postural changes, hyperventilation, and during exercise). RESULTS: Mean P-wave values at supine were 1.92 +/- 1.10 mV at 3 months and 1.76 +/- 1.01 mV at 6 months for VDD systems, and 4.63 +/- 2.18 mV at 3 months and 4.58 +/- 2.80 mV at 6 months for DDD pacemakers. In dynamic conditions, P-wave amplitude changes compared with supine condition ranged between -74 and +226% in VDD, and between -53 and +138% in DDD; however P-wave amplitudes showed no significant changes compared with baseline. Moreover, changes in atrial signal amplitudes did not occur randomly, and in both systems P-wave amplitudes remained significantly correlated with supine values. CONCLUSIONS: A wide range of P-wave amplitude variations occurs in different postural conditions or during exercise, both with single-lead VDD and DDD pacing systems. However, with appropriate programming of atrial sensitivity based on supine values, constant atrial tracking can be maintained.     

Patient with sick sinus syndrome and implanted dual-chamber pacemaker with reduced P-wave duration following low interatrial septal pacing: Case report

Introduction:A dual-chamber pacemaker (DDD/R) for a sinus node disease is sometimes referred to as a physiological pacemaker as it maintains atrioventricular synchrony, however several clinical trials have proved its inferiority to a nonphysiological single-chamber ventricular back-up pacing.Patient concerns:A subject of the study is a 74-year-old woman with a sick sinus syndrome (SSS) and a previously implanted physiological DDD/R pacemaker. The SSS was diagnosed because of patient''s very slow sinus rhythm of about 36 bpm, and due to several episodes of dizziness. After the DDD/R implantation the percentage of atrial pacing approached 100%, with almost none ventricular pacing.Diagnoses:Sick sinus syndrome, complete Bachmann''s bundle block, atrial fibrillation, atrial flutter.Interventions:The patient was previously implanted with a physiological DDD/R pacemaker. Several years after the implantation, the atrial fibrillation was diagnosed and the pulmonary vein isolation was then performed by cryoablation. During the follow-up after pulmonary vein isolation, the improvement of mitral filling parameters was assessed using echocardiography. Shortly thereafter the patient developed the persistent paroxysm of a typical atrial flutter which was successfully terminated using a radiofrequency ablation. No recurrence thereof has been observed ever since (24 months).Outcomes:The atrial electrode of the pacing system was implanted within the low interatrial septal region that resulted in a reduced P-wave duration compared to native sinus rhythm P-waves. The said morphology was deformed because of the complete Bachmann bundle block. That approach, despite a nonphysiological direction of an atrial activation, yielded relatively short P-waves (paced P-wave: 179 ms vs intrinsic sinus P-wave: 237 ms). It also contributed to a significantly shorter PR interval (paced PR: 204 ms vs sinus rhythm PR: 254 ms).Conclusions:The authors took into consideration different aspects of alternative right atrial pacing sites. This report has shown that in some patients with a sinus node disease, low interatrial septal pacing can reduce the P-wave duration but does not prevent from the development of atrial arrhythmias.     

Pacemaker selection: time for a rethinking of complex pacing systems?

Evidence from randomized trials indicates that the clinical benefits of dual-chamber (DDD) pacing are modest: (i) no significant differences exist between physiological pacing and single-chamber pacing in mortality and stroke; (ii) ventricular desynchronization resulting from chronic right-ventricular pacing in DDD mode, induces a significantly increased incidence of atrial fibrillation (AF) and heart failure hospitalizations; (iii) AF pacing prevention and therapy algorithms have shown a modest to minimal or absent efficacy; (iv) the widespread use of physiological pacemakers is not an economically attractive strategy. Thus, these data provide a reliable body of evidence on which to make more rationale clinical decisions for individual patients and policy decisions for health costs saving. The cheaper single-chamber AAI(R) or VVI(R) has been shown to satisfy both conditions in most cases of sinus node disease and AV block.     

Inducibility of atrial fibrillation during atrioventricular pacing with varying intervals: role of atrial electrophysiology and the autonomic nervous system

INTRODUCTION: Patients receiving VVI pacemakers have a higher incidence of paroxysmal atrial fibrillation (AF) than those receiving DDD pacemakers. However, the mechanism behind the difference is not clear. The purpose of this study was to investigate whether atrial electrophysiology and the autonomic nervous system play a role in the occurrence of AF during AV pacing. METHODS AND RESULTS: The study population consisted of 28 patients who had (group I, n = 15) or did not have (group II, n = 13) AF induced by a single extrastimulus during pacing with different AV intervals. Atrial pressure, atrial size, atrial effective refractory periods, and atrial dispersion were evaluated during pacing with different AV intervals. Twenty-four-hour heart rate variability and baroreflex sensitivity also were examined. Atrial pressure, atrial size, effective refractory periods in the right posterolateral atrium and distal coronary sinus, and atrial dispersion increased as the AV interval shortened from 160 to 0 msec. During AV pacing, group I patients had greater minimal (52+/-17 vs 25+/-7 msec; P < 0.005) and maximal (76+/-16 vs 36+/-9 msec; P < 0.005) atrial dispersion than group II patients. The differences in atrial size and atrial dispersion among different AV intervals were greater in patients with AF than in those without AF. Baroreflex sensitivity (6.6+/-1.7 vs 3.9+/-1.0; P < 0.00005), but not heart rate variability, was higher in patients with AF than in those without AF. CONCLUSION: Abnormal atrial electrophysiology and higher vagal reflex activity can play important roles in the genesis of AF in patients receiving pacemakers.     

埋藏式心脏起搏器治疗病态窦房结综合症130例临床总结

目的:探讨在病态窦房结综合征(SSS)患者起搏治疗中各种起搏模式的比例及对患者临床预后的影响。方法:对我院130例行起搏器安装术SSS患者的资料,进行起搏模式及临床预后分析。结果:130例患者中生理性起搏(AAI／DDD)占27.6％,其中AAI起搏占11.2％,DDD起搏占16.4％;心室按需型起搏(VVI)占72.4％。植入起搏器能明显改善SSS患者的临床症状,在生理性起搏组中永久性房颤、心衰的发生率以及患者死亡率均明显低于非生理性起搏组(P<0.05~<0.01),手术并发症发生率为10.8％,主要并发症为电极脱位和感知障碍。结论:生理性起搏是治疗SSS较理想的起搏方式,但目前应用的比例仍偏低。