起搏术后心房颤动的影响因素及心房颤动与心钠素的关系

目的观察心脏起搏术后发生心房颤动(简称房颤)的影响因素及房颤与血心钠素(ANP)的关系。方法选择安装心脏起搏器的患者103例进行随访,分析房颤与年龄、起搏方式、心律失常类型、左房内径(LAD)、左室射血分数(LVEF)和血ANP的关系。结果①65岁以下患者房颤发生率低于65岁以上组(P<0.05)。②VVI组房颤发生率高于DDD组(P<0.05)。③慢快综合征组房颤发生率较缓慢型病窦综合征和房室传导阻滞组高(P<0.05)。④VVI房颤组术后LAD增大、LVEF下降(P<0.05),VVI房颤组术后与DDD组比较有差异(P<0.05)。⑤VVI房颤组和VVI窦性心律组ANP浓度较DDD组高(P<0.05);各组不同心功能级别(NYHA)之间ANP浓度随着心功能级别的加重而升高。结论长期心脏起搏术后房颤的发生可能与年龄大、VVI起搏、病窦综合征(慢快型)、LAD增大、LVEF降低及ANP浓度升高相关。     

VVI mode cardiac pacing: cause or risk factor of cerebral embolism?]

Epidemiological studies suggest that VVI pacing is associated with a higher risk of embolic complications than atrial or dual chamber pacing. However, no studies have been performed on pacemaker patients admitted to a neurological department with a cerebral embolism. The authors report the cases of 8 patients (6 men and 2 women) with an average age of 74 years and having the following characteristics: 1) a cerebral embolism, 2) a permanent cardiac pacemaker (7 VVI and 1 DDD mode). The average delay between implantation of the pacemaker and the neurological complication was 31 months. Cardiological investigations at the time of admission showed: a clinically evident cause of cardiac embolism in 3 cases (2 with VVI and 1 with DDD pacing); paroxysmal or permanent atrial fibrillation in 4 cases with VVI pacing at the time of the embolic event (in only one case at the time of implantation); various echocardiographic abnormalities in 6 of the 7 patients who underwent this examination, mainly left atrial dilatation (6/7), septal wall motion abnormalities in all related to ventricular pacing and unexplained left ventricular dilatation in 2 patients with VVI pacemakers. These results suggest that although the etiology of cerebral embolism was probably multifactorial in some patients, VVI packing probably a predisposing role, though not the only cause, and could be considered to be an embolic risk factor as suggested by previous epidemiological studies. These preliminary retrospective data should be interpreted cautiously taking into account the small population size. Prospective studies on pacemaker patients with cerebral embolism are required.     

Incidence and risk indicators of thromboembolism during the acute phase of single chamber ventricular pacing

BACKGROUND: The incidence of thromboembolism may be higher in single chamber ventricular pacing than in physiological pacing. However, the incidence of thromboembolism during the acute phase of single chamber ventricular pacing (within 14 days) is not known. OBJECTIVES: The incidence and the risk indicators of thromboembolism were investigated during the acute phase of single chamber ventricular pacing. METHODS: Fifty-five consecutive patients (22 males, 33 females, mean age 67 +/- 9 years) who required VVI pacemakers due to brady-tachy sick sinus syndrome (42 patients) or brady atrial fibrillation (13 patients) in the period from April 1975 to December 2000 were retrospectively reviewed. The patients were divided into groups with thromboembolism and without thromboembolism, and the risk indicators for thromboembolism were analyzed. RESULTS: Seven patients (13%) suffered systemic thromboembolism. Three patients had thromboembolic events during temporary ventricular pacing, and four patients had thromboembolic events just after permanent VVI pacemaker implantation. The following risk indicators were identified in the patients with thromboembolism: hyperlipidemia, hypertension, organic heart disease (p < 0.05, respectively), and diabetes mellitus (p < 0.0005). CONCLUSIONS: Patients with brady-tachy sick sinus syndrome and brady atrial fibrillation have a significant risk of thromboembolism during the acute phase of single chamber ventricular pacing. Effective anticoagulation is needed in these patients.     

长期心房与心室起搏对心房颤动发生率的影响

目的 为比较长期心房与心室起博心房颤动(Af)发生率的影响.方法 选择国内较大的三家医院1992年至1994年期间内安装人工心脏起搏器的病人,随访观察心房起搏(安装了AAI、AAIR、DDD及DDDR起博器)和心室起搏(植入了VVI或VVIR起搏器)Af的发生情况.结果 发现心室搏Af发生有逐年增加的趋势,Af4年发生率为33%,5年为41%,6年为52%.单纯心房起搏或房室顺序起搏Af发生率3%,而单纯心室起搏的病人中约40%出现Af,明显高于心房起搏组,P<0.01.结论 研究证明心房起搏可以减少Af的发生,为起搏方式的选择提供了一个客观根据,提示在临床实践中应该尽量选择AAI和DDD等生理性起搏方式.     

VVI与DDD起搏对病窦综合征患者远期疗效的比较

比较VVI与DDD起搏方式对病窦综合征患者的临床疗效。研究病窦综合征患者212例,按不同起搏方式分为两组:VVI组105例、DDD组107例。研究终点:①在每次预定的随访中,以标准12导联ECG、Holter及心电监护诊断心房颤动(简称房颤);②卒中:当患者有大于24h脑缺血事件而产生神经系统症状或24h内死于脑血管事件,可确诊为卒中;③死亡:心血管事件死亡。患者出院后1,3,6个月定期随访,以后每隔半年随访一次。随访时,记录标准12导联ECG存档。每例患者至少有一份ECG,部分患者做Holter,了解有无阵发性房颤及术后发生持续性房颤的时间,患者的症状及体征。结果:①与VVI组比较,DDD组房颤发生率明显降低(10.3%vs24.8%,P<0.05);②VVI组患者6例出现脑卒中(5.7%),而DDD组无1人发生脑卒中,两组差异有显著性(P<0.05);③VVI组共有3例在术后3,4年发生慢性充血性心力衰竭,最后死于恶性心律失常,而DDD组患者均无因心力衰竭住院,随访至今无死亡。DDD组11例房颤均在2年内发生,其中第1年7例,而VVI组有26例房颤发生的时间较为弥散,2年内发生8例(30.8%),其余在3~8年内陆续发生。结论:病窦综合征患者安装双腔起搏器治疗发生房颤和脑卒中的机率明显减少。     

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。     

瓣膜置换术后窦性心动过缓VVI与DDD起搏的随访观察

目的探讨VVI与DDD起搏对瓣膜置换术后窦性心动过缓患者疗效的差异。方法瓣膜置换术后窦性心动过缓患者29例,按不同起搏方式分为:DDD组(n=17例),VVI组(n=12例),观察左室射血分数,短轴缩短率,心房心室变化,永久性心房颤动(简称房颤),卒中,心力衰竭(简称心衰)住院,死亡的发生。结果两组患者均未发生起搏器安置术并发症,在平均随访28个月,未发生卒中、死亡。与VVI组比较,DDD组心衰住院率(10.5%vs 16.6%,P<0.05),永久性房颤发生率降低(11.7%vs 16.6%,P<0.05),左室射血分数增加(0.63±0.10 vs 0.57±0.08,P<0.05)。VVI组起搏后左房内径,左房容积增大,而DDD组不变。两组心功能均提高且无差异。结论对于瓣膜置换术后窦性心动过缓患者,DDD起搏较VVI起搏降低永久性房颤发生率,心衰住院率,改善心脏结构和心功能。     

Regional differences in the recovery course of tachycardia-induced changes of atrial electrophysiological properties

BACKGROUND: Regional differences in recovery of tachycardia-induced changes of atrial electrophysiological properties have not been well studied. METHODS AND RESULTS: In the control group (5 dogs), atrial effective refractory period (AERP) and inducibility of atrial fibrillation (AF) were assessed before and every 4 hours for 48 hours after complete atrioventricular junction (AVJ) ablation with 8-week VVI pacing. In experimental group 1 (15 dogs), AERP and inducibility of AF were assessed before and after complete AVJ ablation with 8-week rapid right atrial (RA) pacing (780 bpm) and VVI pacing. In experimental group 2 (7 dogs), AERP and inducibility of AF were assessed before and after 8-week rapid left atrial (LA) pacing and VVI pacing. AERP and inducibility and duration of AF were obtained from 7 epicardial sites. In the control group, atrial electrophysiological properties obtained immediately and during 48-hour measurements after pacing did not show any change. In the 2 experimental groups, recovery of atrial electrophysiological properties included a progressive recovery of AERP shortening, recovery of AERP maladaptation, and decrease of duration and episodes of reinduced AF. However, recovery of shortening and maladaptation of AERP and inducibility of AF was slower at the LA than at the RA and Bachmann's bundle. CONCLUSIONS: The LA had a slower recovery of tachycardia-induced changes of atrial electrophysiological properties, and this might play a critical role in initiation of AF.     

Clinical efficacy of permanent cardiac pacing in patients with bradysystolic forms of disturbances of cardiac rhythm and conduction

From 1996 to 2002 primary implantations of pacing systems because of bradysystolic disturbances of cardiac rhythm and conduction had been carried out in 311 patients. Indications were disturbances of atrioventricular conduction in 168 and sick sinus syndrome in 143 patients. According to type of permanent pacing patients were divided into 3 groups: with single-chamber ventricular on demand pacing (VVI, n=215), with single-chamber atrial pacing (AAI, n=39), and with dual-chamber pacing (DDD, n=57). As characteristics illustrating long term clinical results of permanent pacing we used development of the pacemaker syndrome; development of permanent atrial fibrillation; risk of thromboembolic complications and strokes; progression of heart failure; total, cardiovascular mortality and their structure; 7 year survival.     

The effect of atrial preference pacing on atrial fibrillation electrophysiological substrate in Myotonic Dystrophy type 1 population

P-wave dispersion is a non invasive indicator of intra-atrial conduction heterogeneity producing substrate for reentry, which is a pathophysiological mechanism of atrial fibrillation. The relationship between P-wave dispersion (PD) and atrial fibrillation (AF) in Myotonic dystrophy type 1 (DM1) patients is still unclear. Atrial Preference Pacing (APP) is an efficient algorithm to prevent paroxysmal AF in patients implanted with dual-chamber pacemaker. Aim of our study was to evaluate the possible correlation between atrial preference pacing algorithm, P-wave dispersion and AF burden in DM1 patients with normal cardiac function underwent permanent dual-chamber pacemaker implantation.We enrolled 50 patients with DM1 (age 50.3 ± 7.3; 11 F) underwent dual-chamber pacemaker implantation for various degree of atrioventricula block. The study population was randomized following 1 months stabilization period to APP algorithm features programmed OFF or ON. Patients were assessed every 3 months for the first year, and every 6 months thereafter up to 3 years. At each follow-up visit, we counted: the number of premature atrial beats, the number and the mean duration of AF episodes, AF burden and the percentage of atrial and ventricular pacing.APP ON Group showed lower number of AF episodes (117 ± 25 vs. 143 ± 37; p = 0.03) and AF burden (3059 ± 275 vs. 9010 ± 630 min; p < 0.04) than APP OFF Group. Atrial premature beats count (44903 ± 30689 vs. 13720 ± 7717 beats; p = 0.005) and Pwave dispersion values (42,1 ± 11 ms vs. 29,1 ± 4,2 ms, p = 0,003) were decreased in APP ON Group. We found a significant positive correlation between PD and AF burden (R = 0,8, p = 0.007).Atrial preference pacing algorithm, decreasing the number of atrial premature beats and the P-wave dispersion, reduces the onset and perpetuator factors of AF episodes and decreases the AF burden in DM1 patients underwent dual chamber pacemaker implantation for various degree of atrioventricular blocks and documented atrial fibrillation.Key words: atrial fibrillation, Myotonic Dystrophy, atrial preference pacing     

Influence of Cardiac Pacing Mode on Left Atrial Appendage Flow Velocity: Implication to Systemic Embolism During VVI Pacing

Previous studies have shown that the incidence of thromboembolism is higher in patients with single-chamber ventricular demand (VVI) pacemakers than in patients with dual-chamber (DDD) pacemakers. However, data on left atrial appendage flow velocity in pacing patients are limited. To investigate the influence of the pacing mode on the left atrial appendage flow velocity, we studied 19 patients with permanent DDD pacemakers and measured the left atrial appendage flow velocity by transesophageal echocardiography at baseline (during DDD pacing) and after switching to VVI pacing. The indications for pacemaker implantation were second- and third-degree atrioventricular block (AVB group, n = 11) and sick sinus syndrome (SSS group, n = 8). Compared with the DDD pacing mode, there was a significant decrease in the left atrial appendage flow velocity during VVI pacing in both the SSS group (43 ± 14 vs 23 ± 7 cm / sec, P < 0.05) and the AVB group (59 ± 18 vs 41 ± 18 cm / sec, P < 0.05). In eight patients with persistent retrograde ventriculoatrial conduction during VVI pacing, the left atrial appendage flow velocity was markedly decreased (from 43 ± 16 to 25 ± 9 cm / sec, P < 0.05). In five (63%) of the eight patients, left atrial appendage flow velocity was less than 25 cm/sec. A reduction in left atrial appendage flow velocity when switching from DDD to VVI pacing may account for an increased risk of thrombus formation in the left atrial appendage (an increased thromboembolic risk in patients in sinus rhythm with VVI pacemakers).     

Selecting the Appropriate Pacing Mode for Patients with Sick Sinus Syndrome: Evidence from Randomized Clinical Trials

Several observational studies have indicated that selection of pacing mode may be important for the clinical outcome in patients with symptomatic bradycardia, affecting the development of atrial fibrillation (AF), thromboembolism, congestive heart failure, mortality and quality of life. In this paper we present and discuss the most recent data from six randomized trials on mode selection in patients with sick sinus syndrome (SSS). In pacing mode selection, VVI(R) pacing is the least attractive solution, increasing the incidence of AF and-as compared with AAI(R) pacing, also the incidence of heart failure, thromboembolism and death. VVI(R) pacing should not be used as the primary pacing mode in patients with SSS, who haven't chronic AF. AAIR pacing is superior to DDDR pacing, reducing AF and preserving left ventricular function. Single site right ventricular pacing-VVI(R) or DDD(R) mode-causes an abnormal ventricular activation and contraction (called ventricular desynchronization), which results in a reduced left ventricular function. Despite the risk of AV block, we consider AAIR pacing to be the optimal pacing mode for isolated SSS today and an algorithm to select patients for AAIR pacing is suggested. Trials on new pacemaker algorithms minimizing right ventricular pacing as well as trials testing alternative pacing sites and multisite pacing to reduce ventricular desynchronization can be expected within the next years.     

Effectiveness of Rapid Atrial Pacing for Termination of Drug Refractory Atrial Fibrillation: Results of a Dual Chamber Implantable Cardioverter Defibrillator Trial

There is increasing interest in the use of an implantable cardioverter defibrillator (ICD) to manage atrial tachyarrhythmias. Although device-based shock therapy is highly effective in terminating persistent atrial tachyarrhythmias, atrial overdrive pacing may also be useful, particularly when this therapy is applied early after the onset of an arrhythmia. A dual-chamber ICD (Medtronic 7250 Jewel AF(R)) has been studied in 267 patients with drug-refractory symptomatic AF. The patients were enrolled as part of multicenter clinical trial to evaluate the safety and efficacy of the device to manage atrial tachyarrhythmias in the absence of a standard ventricular ICD indication. The device discriminates atrial tachycardia (AT) from atrial fibrillation (AF) based on cycle length and regularity, and employs multiple methods of atrial overdrive pacing as well as shocks to terminate tachyarrhythmia episodes. Patients were followed for an average of 15.8 +/- 9.3 months. A majority (63%) of patients presented with a history of persistent AF and 34% presented with a history of paroxysmal AF. The pacing therapies terminated 54% of AT episodes and 27% of AF episodes. In patients with persistent AF, 75% of the AT/AF episodes that were successfully terminated by pacing lasted 相似文献   

老年心房颤动不同方式的经导管射频消融治疗

目的研究不同方式经导管射频消融治疗对老年房颤的治疗效果。方法53例房颤患者，男性38例，女性15例，年龄60-83岁。按接受不同的经导管消融方法将上述患者分为3组：消融隔离肺静脉治疗阵发性房颤组20例、消融典型房扑治疗房颤合并房扑组26例、消融房室传导加植入永久性起搏器治疗持续性房颤伴药物难以控制的快速心室率和（或）心力衰竭组7例。结果消融隔离肺静脉组中15例采用环状标测电极导管引导电隔离3～4根肺静脉成功，术后无房颤发作8例（53％），房颤发作明显减少4例（27％）；采用电解剖系统引导下环双侧肺静脉线性消融隔离肺静脉5例，无房颤发作4例（80％）。消融房扑组26例典型房扑均消融成功，随访中15例（58％）无房颤发作，8例（31％）房颤发作较前减少。经导管消融房室传导组7例全部成功，4例行右心室、3例行双心室VVI模式起搏，随访中生活质量和（或）心力衰竭症状明显改善。结论针对不同类型的老年房颤患者采用不同的经导管消融方法可以取得较好的临床效果。     

老年心房颤动患者左心房内径及其电活动变化的临床研究

目的探讨老年心房颤动(房颤)患者左心房内径、电活动变化及其意义。方法142例老年非瓣膜性房颤患者(房颤组)进行彩色多普勒超声心动图仪及三导心电图仪检查,测定左心房内径(LAD)、左心室舒张期末内径、左心室后壁厚度、室间隔厚度、左心室射血分数(LVEF)及房颤的检出。采用食管调搏的方法测定左心房电生理特性,以400ms起搏周长(PCL)对左心房进行S1S2扫描,测定基础状态左心房有效不应期(LAERP);以3种不同起搏周长(400、500、600ms)对左心房进行S1S2扫描,观察LAERP频率适应性。150例健康体检者为正常对照组。结果房颤组患者LAD较正常对照组显著增加,其中左心房扩大(LAD>32mm)者占95.07%,且持续性房颤患者LAD较阵发性房颤患者显著增加。左心室肥厚患者LAD较无左心室肥厚患者显著扩大,左心房扩大与心功能降低有关,其中左心房显著扩大者(LAD≥40mm)其LVEF、每搏输出量下降最明显。房颤组患者LAERP较正常对照组显著缩短,LAERP频率适应性较正常对照组减退。结论LAD扩大及其电重构与房颤发生密切相关,LAD扩大与左心室肥厚及心功能减退有关。     

Cost-Effectiveness of antiarrhythmic drugs for prevention of thromboembolism in patients with paroxysmal atrial fibrillation

To determine whether treatment with antiarrhythmic drugs could be cost-effective in preventing thromboembolic events in patients with paroxysmal atrial fibrillation (AF), 4 groups of patients without prior thromboembolism were studied. Group A: 193 patients with paroxysmal AF receiving antiarrhythmic drugs, but not antiplatelets or warfarin; Group B: 228 patients with paroxysmal AF not receiving antiarrhythmics, antiplatelets or warfarin; Group C: 284 patients with chronic AF receiving warfarin; Group D: 394 patients with chronic AF not receiving antiplatelets or warfarin. Direct costs for treatment of AF were determined. During a follow-up period of 4.6 years, the prevalence of thromboembolic episodes was lower by 70% in Group A and by 47% in Group C than in each control group. To prevent one thromboembolic event annually with antiarrhythmic drugs in patients with paroxysmal AF, an extra cost of 6.16 million yen was required. This less favorable cost-effectiveness was mainly because of physician's preference for new antiarrhythmic drugs. In contrast, treatment with warfarin required an extra cost of 1.09 million yen to prevent one thromboembolic event annually in patients with chronic AF. Antiarrhythmic drugs are less cost-effective in preventing thromboembolic events in patients with paroxysmal AF when new, expensive drugs are preferentially selected.     

Deleterious effects of long-term single-chamber ventricular pacing in patients with sick sinus syndrome: the hidden benefits of dual-chamber pacing.

Nine hundred fifty patients who received three modes of primary pacemaker systems (581 dual-chamber universal [DDD], 84 atrioventricular-sequential ventricular-inhibited [DVI] and 285 ventricular-inhibited [VVI]) over 12 years were studied retrospectively to determine the effect of pacing mode on patient longevity and the subsequent development of chronic atrial fibrillation or flutter. All patients were followed up continuously for 7 to 8 years. Patients were classified according to indication for permanent pacing (sick sinus syndrome or other indication), age at pacemaker implantation (less than or equal to 70 or greater than 70 years) and history of atrial tachyarrhythmia. Fourteen percent of patients developed atrial fibrillation at some time during the study period. Of those, 4% had a DDD pacemaker, 8% had a DVI pacemaker and 19% had a VVI pacemaker. At 7 years, atrial fibrillation was significantly more frequent in the VVI group than in the DDD and DVI groups. In patients with sick sinus syndrome, the incidence rate was even higher in the VVI group but approximately the same in the DDD and DVI groups. Patients in the VVI and DVI groups who had had previous atrial tachyarrhythmia had a significantly higher incidence of atrial fibrillation at 7 years than did those in the DDD group. During the entire period there were 130 deaths in the study group, including 22% of patients with a DDD pacemaker, 38% of those with a DVI pacemaker and 50% of those with a VVI pacemaker. Patient survival at 7 years was lower in the VVI group than in the DDD or DVI groups.(ABSTRACT TRUNCATED AT 250 WORDS)     

Achieving regular slow rhythm during atrial fibrillation without atrioventricular nodal ablation: selective vagal stimulation plus ventricular pacing.

OBJECTIVES: The aim of this study was to achieve regular slow ventricular rhythm during atrial fibrillation (AF) without destroying the AV node (AVN). BACKGROUND: Recent experimental and clinical studies have demonstrated that selective AVN vagal stimulation (AVN-VS) can be used to slow ventricular rate during AF; however, an irregular rhythm remains. Alternatively, ventricular on-demand (VVI) pacing achieves rate regularization but at rates faster than the already fast intrinsic rate during AF. We hypothesized that AVN-VS combined with VVI pacing would achieve slow, regular rhythm during AF without requiring AVN ablation. METHODS: AF was induced in eight dogs. AVN-VS was applied to the epicardial fat pad that projects vagal nerve fibers to the AVN. A computer-controlled algorithm adjusted AVN-VS intensity to achieve three levels of mean ventricular RR interval: 75%, 100%, or 125% of the spontaneous sinus cycle length. At each of the three levels, concomitant VVI pacing was delivered at a constant cycle length equal to the corresponding target. Hemodynamic measurements were performed during the study to elucidate the advantages of the proposed method. RESULTS: AF resulted in rapid, irregular ventricular rates (RR = 287 +/- 36 ms, or 56% of sinus cycle length). AVN-VS achieved average ventricular rate slowing to the three target levels in all dogs (RR increased to 381 +/- 41, 508 +/- 54, and 632 +/- 68 ms, respectively). At each of the three target rate levels, AVN-VS combined with VVI pacing fully eliminated rate irregularities. The regular slow ventricular rhythms during AF were associated with significant hemodynamic improvement. CONCLUSIONS: A novel approach combining AVN-VS with VVI pacing results in a regular, slow ventricular rhythm during AF that does not necessitate AVN ablation. Rate regularization achieved by this approach was associated with pronounced hemodynamic benefits during AF.     

P wave changes and atrial fibrillation after implantation of VVI type pacemaker]

The P waves of patients with VVI pacemakers were compared with those of DDD pacemakers at implantation and then regularly for 5 years. A certain number of cardiac pathologies are known to cause P wave changes. The incidence of atrial fibrillation (AF) was much higher in VVI than in DDD patients. In the VVI group, the incidence was much greater in patients paced for sinus node disease than in patients paced for AVB. Analysis of sinus P wave characteristics in 320 patients with VVI pacemakers shows progressive abnormalities of atrial function with time. The expression of this atrial dysfunction is a statistically significant prolongation of the P wave in V1 and dII and of the terminal part of the P wave in V1. The factors responsible for this abnormality and which favours the occurrence of AF are quasi-permanent pacing, the presence of retrograde conduction and an abnormality of atrial activation at the time of implantation.     

"Subclinical" pacemaker syndrome: a randomised study of symptom free patients with ventricular demand (VVI) pacemakers upgraded to dual chamber devices.

OBJECTIVE--To determine whether symptom free patients with single chamber pacemakers benefit from dual chamber pacing. DESIGN--A randomised double blind crossover comparison of ventricular demand (VVI), dual chamber demand (DDI), and dual chamber universal (DDD) modes after upgrading from a VVI device. SETTING--Cardiology outpatient department. PATIENTS--Sixteen patients aged 41-84 years who were symptom free during VVI mode pacing for three or more years. INTERVENTION--Pacemaker upgrade during routine generator change. MAIN OUTCOME MEASURES--Change in subjective (general health perception, symptoms) and objective (clinical assessment, treadmill exercise, and radiological and echocardiographic indices) results between pacing modes before and after upgrading. RESULTS--75% preferred DDD, 68% found VVI least acceptable with 12% expressing no preference. Perceived general well-being and exercise capacity (p less than 0.01) and treadmill times (p less than 0.05) were improved in DDD mode but VVI and DDI modes were similar. Clinical, echocardiographic, radiological, and electrophysiological indices confirmed the absence of overt pacemaker syndrome, although mitral and tricuspid regurgitation was greatest in VVI mode (p less than 0.01). CONCLUSIONS--Most patients who were satisfied with long term pacing in VVI mode benefited from upgrading to DDD mode pacing suggesting the existence of "subclinical" pacemaker syndrome in up to 75% of such patients. The DDI mode offered little subjective or objective benefit over VVI mode in this population and should be reserved for patients with paroxysmal atrial arrhythmias. VVI mode pacing should be used only for patients with very intermittent symptomatic bradycardia or atrial fibrillation with a good chronotropic response during exercise.