Double-counting of intracardiac electrogram during biatrial pacing.

BACKGROUND: Biatrial pacing has a significant problem with memory function that misinterprets normal sinus rhythm as atrial tachyarrhythmias and in addition estimation of the atrial pacing thresholds (biatrial and uniatrial pacing thresholds) is sometimes difficult because of small P waves. METHODS AND RESULTS: The intracardiac electrograms recorded by a pacemaker in 10 patients (age, 66.7+/-10.7 (SD) years) with implanted biatrial pacemakers were analyzed. Atrial sensing within the atrial refractory period after atrial pacing was counted in 6 of the 10 patients (timing of the double counting was 143+/-64 ms) when pacing failed in the left or right atrium. Atrial sensing within the atrial refractory period after atrial pacing disappeared when biatrial pacing was successfully performed. Atrial double-counts depend on interatrial conduction delay. The memory function of implanted pacemaker devices misinterpreted normal sinus rhythm as atrial tachyarrhythmias because of atrial double-counts. On the other hand, the biatrial pacing threshold was easily recognized using this phenomenon. CONCLUSIONS: The memory function of pacemaker devices is unreliable because of atrial double-counting during sinus rhythm in patients with biatrial pacing. However, the biatrial pacing threshold is easily checked using this phenomenon.     

Effectiveness of Ibutilide in Cardioversion of Persistent Atrial Fibrillation in Patients with Dual Chamber Stimulation

Aim of the study: To evaluate the effectiveness of Ibutilide in cardioversion of persistent atrial fibrillation in patients with sinus node disease wearing a dual chamber pacemaker and to assess the potential role of overdrive ventricular pacing in prevention of drug related proarrhythmia. Methods and Results: Fifty-three sinus node disease patients (35 males; mean age 75 ± 9.5 years), implanted with a dual chamber pacing system, with persistent atrial fibrillation, lasting for 328 ± 416 days, received 1–2 mg of intravenous Ibutilide. Pacing mode was programmed in VVI at 90 ppm, in order to suppress spontaneous ventricular activity. All patients were monitored for 4 hours. Late occurrence of ventricular arrhythmias was evaluated using the pacemaker memory. Ventricular pacing threshold, spontaneous electrogram amplitude and pacing impedance were measured before and after Ibutilide infusion. Cardioversion to sinus rhythm occurred in twenty-two patients (41.5%). Treatment success was significantly related to shorter atrial fibrillation duration. Paced QT interval duration increased from 412 ± 36 ms to 481 ± 40 ms (p < 0.0001), without differences between responders and non responders; QRS width did not change significantly (from 152 ± 25 ms to 161 ± 25 ms; p = n.s.). No early or late episodes of sustained or non sustained polymorphic ventricular tachycardia were observed. Pacing and sensing threshold did not show any significant variation. Conclusions: Ibutilide showed a good effectiveness in treating persistent atrial fibrillation in paced patients. Overdrive ventricular pacing may have played a role in preventing drug induced ventricular proarrhythmia. No adverse effect on pacing threshold was observed.     

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.     

A novel method of multisite atrial pacing, incorporating Bachmann's bundle area and coronary sinus ostium, for electrical atrial resynchronization in patients with recurrent atrial fibrillation.

AIMS: The aim of the study was to assess efficacy and safety of a novel method of multisite atrial pacing, incorporating Bachmann's bundle (BB) and coronary sinus (CS) ostium pacing, which was implemented for the first time in atrial fibrillation (AF) patients with intra-atrial conduction delay. METHODS AND RESULTS: This follow-up study included 97 patients with drug refractory symptomatic AF, sinus node dysfunction, sinus P-wave > or = 120 ms, and normal atrioventricular conduction. Pacing efficacy was assessed on the basis of two main endpoints: successful rhythm control and the absence of documented or symptomatic AF. During the mean 2.3 +/- 0.7 years of follow-up, the survival rate was 99%, pacing maintenance rate 97%, and the need for re-operation 5%. Rhythm control efficacy was 90%, and 14 patients had no evidence of recurrent AF. After implantation, the mean number of anti-arrhythmic drugs used (P < 0.0001), the need for cardioversion (P < 0.01), and the incidence (P < 0.0001) and duration (P < 0.001) of AF-related hospitalizations decreased. P-wave duration with multisite atrial pacing was shorter than during sinus rhythm, BB, and CS pacing (P < 0.0001). CONCLUSION: A novel method of multisite atrial pacing is safe, provides effective long-term rhythm control, and decreases the necessity for adjunctive therapies in patients with refractory AF and intra-atrial conduction delay.     

Schrittmachertherapie bei Patienten mit Vorhofflimmern

Pacemaker therapy in patients with atrial fibrillation means the best current pacemaker therapy for patients with bradycardias with the aim to avoid the onset of atrial fibrillation and to establish DDD pacing despite of a history of atrial tachyarrhythmias. The newer application of pacing is the suppression of atrial arrhythmias in patients with medical refractory atrial tachyarrhythmias. Patients with slow ventricular rates and permanent atrial fibrillation should receive a VVI-pacemaker, if the bradycardias causes syncope, dizziness or a decrease of their exercise tolerance. In case of chronotropic incompetence the pacemaker should provide rate responsive pacing. Patients with sick sinus syndrome should receive an atrial (AAI) or dual-chamber (DDD) pacemaker, because patients with these in contrast to VVI-pacemakers develop less often atrial fibrillation and subsequent complications such as atrial thromboembolism. A dual-chamber or VDD-pacemaker—the latter connected to a VDD-single-lead—is indicated in patients with advanced AV-block. Atrial fibrillation occurs in 3 to 6% of the patients with no history of arrythmia and is, if pacemakers have no automatic mode switch, an often reason to program the devices to the VVI-pacing mode. Nowadays, most DDD(R)-pacemakers provide an automatic mode switch: During an atrial tachycardia the pacemaker switches to a VVI/VVIR mode and restores the initial DDD(R)-pacing mode with termination of the arrhythmia. In respect to the newer applications, one approach to prevent atrial tachyarrhythmias is permanent atrial pacing. As lower pacing rates of 80 to 90 ppm are usually needed and many patients hardly tolerate these pacing rates, new algorithms are under clinical investigation. Another approach is the simultaneous depolarization of the right and left atrium. Biatrial pacing is performed with one lead in the high right atrium and another lead in the coronary sinus. Another solution is bifocal atrial pacing with leads placed in the high right atrium and in the coronary sinus ostium. One effect of the new pacing techniques is to shorten interatrial conduction times. Therefore, biatrial pacing has become a therapy to prevent atrial arrhythmias deriving from delayed interatrial conduction times. As atrial reentry circuits seem to be important in atrial fibrillation, multisite atrial pacing is also performed in patients with medical refractory paroxysmal atrial fibrillation. Preliminary results suggest a more effective prevention of atrial fibrillation; nevertheless, these techniques should be still restricted to patients enrolled in clinical studies.     

Blind atrial pacing for patients with sinus node disease who develop atrial fibrillation during permanent pacemaker implantation

During a 6-year period, six of 110 patients implanted with AAI pacemakers for sick sinus syndrome developed atrial fibrillation at the time of pacemaker implantation (5.5%). In all cases a passive fixation lead was sited in the right atrial appendage, its stability being ensured by rotation of the lead and phrenic nerve stimulation excluded by pacing at 10 V. One patient remained in chronic atrial fibrillation. In the other five, who subsequently reverted to sinus rhythm, atrial P-wave sensing and lead threshold values were satisfactory, allowing programming of the pacemaker output down to 2.5 V to conserve the battery. One out of these five patients continued to have intermittent atrial fibrillation. We conclude that in sick sinus syndrome, atrial fibrillation complicates AAI pacemaker implantation procedure in 5.5% of cases. As an alternative to an unplanned general anaesthetic to cardiovert the patient, it is reasonable to implant an atrial lead in the right atrial appendage in the expectation of a spontaneous reversion to sinus rhythm with a good lead threshold and P-wave sensing. In contrast to inappropriate pacing of the right ventricle in VVI mode, this strategy avoids pacemaker syndrome and reduces the risk of subsequent attacks of atrial fibrillation.     

房间隔起搏对房性早搏和房性心动过速的一年疗效

目的探讨房间隔起搏(ASP)对房性早搏(简称房早)和房性心动过速(简称房速)的一年疗效。方法对46例有起搏器植入适应证的患者采用ASP和室间隔起搏方式植入DDD45例和AAI1例。植入前检查24h动态心电图(DCG)和12导联体表心电图,植入后1周复查ASP时12导联体表心电图,植入后1周、3个月和12个月复查DCG,用以测量起搏前窦性心律时和ASP时的最大P波时限,以及观察起搏前和起搏后一年内房早和房速的发作情况。结果①与起搏前窦性心律心电图比较:ASP时的最大P波时限明显缩短(76.00±14.59msvs98.00±14.07ms,P0.01)。②与起搏器植入前相比:起搏器植入后1周、3个月和12个月时,DCG检出的房早发作次数和房速发作阵数均明显减少(P均0.05),术后3个月时DCG检出的房速发作例数也有减少(P0.05)。结论 ASP能缩短房间传导时间,减少术后房早和房速的发作。     

Interatrial septum pacing guided by three-dimensional intracardiac echocardiography

OBJECTIVES: Currently, the interatrial septum (IAS) pacing site is indirectly selected by fluoroscopy and P-wave analysis. The aim of the present study was to develop a novel approach for IAS pacing using intracardiac echocardiography (ICE). BACKGROUND: Interatrial septum pacing may be beneficial for the prevention of paroxysmal atrial fibrillation. METHODS: Cross-sectional images are acquired during a pull-back of the ICE transducer from the superior vena cava into the inferior vena cava by an electrocardiogram- and respiration-gated technique. Both atria are then reconstructed using three-dimensional (3D) imaging. Using an "en face" view of the IAS, the desired pacing site is selected. Following lead placement and electrical testing, another 3D reconstruction is performed to verify the final lead position. RESULTS: Twelve patients were included in this study. The IAS pacing was achieved in all patients including six suprafossal (SF) and six infrafossal (IF) lead locations all confirmed by 3D imaging. The mean duration times of atrial lead implantation and fluoroscopy were 70 +/- 48.9 min and 23.7 +/- 20.6 min, respectively. The IAS pacing resulted in a significant reduction of the P-wave duration as compared to sinus rhythm (98.9 +/- 19.3 ms vs. 141.3 +/- 8.6 ms; p < 0.002). The SF pacing showed a greater reduction of the P-wave duration than IF pacing (59.4 +/- 6.6 ms vs. 30.2 +/- 13.6 ms; p < 0.004). CONCLUSIONS: Three-dimensional ICE is a feasible tool for guiding IAS pacing.     

Prevention of Short Term Reversible Chronic Atrial Fibrillation by Permanent Pacing at the Triangle of Koch

Objectives: The purpose of this study was to investigate if single lead interatrial septum pacing could be effective in maintaining sinus rhythm in patients in whom restoration of sinus rhythm was only possible for a period of 2–24 hours after one or more previous electrical cardioversions, and in whom a sinus bradycardia was documented before arrhythmia restarted. The two hours limit was chosen because it was considered a sufficient time to implant a dual chamber pacemaker. Background: Alternative atrial pacing techniques have been demonstrated to be successful in preventing recurrences of atrial fibrillation (AF) in patients with sinus bradycardia. Excluding the AF occurring after only a few sinus beats, at 24 hours from electrical cardioversion an early restart of chronic AF has been reported in 12[emsp4 ]% to 17[emsp4 ]% of the patients. Methods: After sinus rhythm was restored by internal electrical cardioversion, 17 patients, 7 ablated at the AV junction, underwent a dual chamber rate response (DDDR) pacemaker implantation with a screw-in atrial lead placed in the interatrial septum. Results: After a follow-up period of 17±5 months (range 12 to 27 months) persistence of sinus rhythm was observed in 11 patients (65[emsp4 ]%). Six patients (35[emsp4 ]%) had recurrences of paroxysmal attacks, while five (30[emsp4 ]%) were totally free of AF. Recurrence of chronic AF was observed in six cases (35[emsp4 ]%) after 2 days–12 months from implantation. No dislodgements of the atrial lead and no complications were observed at implantation and during follow-up. Conclusions: Interatrial septum pacing is a safe and feasible technique with a satisfying success rate (65[emsp4 ]%) in long-term maintaining sinus rhythm in previously unsuccessfully cardioverted patients.     

双房同步起搏技术的临床应用

双房同步起搏是恢复双房电活动同步化的一种新的起搏技术,可防治快速房性心律紊乱。笔者对１７例房内、房间传导阻滞并快速房性心律失常患者进行双房同步起搏治疗,１４例行三腔起搏（ＤＤＤ）、３例行双房起搏（ＡＡＩ）,冠状静脉窦电极均经左锁骨下静脉途径放置。起搏器及电极导线均顺利植入,未发现脱位、穿孔等并发症。冠状静脉窦电极导线顶端电极测定的Ｐ波振幅为５．６９±２．６３（２．４～９．６）ｍＶ、起搏阻抗６５５±１９４．１１（５２０～９６０）Ω、单极起搏阈值０．９２±０．６８（０．４～２．２）Ｖ。冠状静脉窦电极位置较深,则测得起搏阈值较低。随访８．６（３～１５）个月,１例猝死、１６例健在;其预防心房扑动、颤动的显效率达６２．５％、有效率达８１．２５％。结论：双房同步起搏技术是房间传导阻滞合并房性心动过速,心房扑动、颤动的有效治疗和预防方法。     

Beneficial effects of biatrial pacing on cardiac function in patients with bradycardia -- tachycardia syndrome.

BACKGROUND: Biatrial (BiA) pacing prevents atrial fibrillation. By an unknown mechanism. The purpose of this study was to use Doppler echocardiography to evaluate the hemodynamic effects during BiA pacing. METHODS AND RESULTS: The subjects were 7 patients with bradycardia - tachycardia syndrome with an implanted pacemaker. Atrial pacing sites were the right atrial appendage (RAA) and coronary sinus. P wave duration during BiA pacing (123 +/-16 ms) was significantly shorter than during either RAA pacing (167+/-19 ms, p<0.05) or sinus rhythm (148+/-12 ms, p<0.05). Doppler echocardiography revealed a greater cardiac output during BiA pacing than during RAA pacing (4.1+/-1.1 vs 3.5+/-0.7 L/min, p=0.042). The Doppler waveform of transmitral flow indicated that the left ventricular contraction interrupted the atrial filling wave during RAA pacing. The interval between the end of the atrial filling wave of transmitral flow and the mitral valvular closing sound was significantly increased by BiA pacing compared with RAA pacing (56+/-65 vs 40+/-57 ms, p=0.047). CONCLUSION: Cardiac hemodynamics were improved by BiA pacing and reduction of left atrial load may be one of the mechanisms.     

Long-term clinical performance of AAI pacing in patients with sick sinus syndrome: a comparison with dual-chamber pacing.

AIMS: In this clinical study, we compared two groups of age-matched patients, AAI and DDD, to evaluate the clinical benefits of AAI pacing in patients with sick sinus syndrome (SSS) and normal atrioventricular (AV) conduction. METHODS AND RESULTS: Ninety-five patients with SSS implanted with AAI pacemakers were compared with 101 SSS patients implanted with DDD pacemakers. Mortality, chronic atrial fibrillation, lead survival rates, and reoperation rates were compared by Kaplan-Meier analysis. Eight AAI devices were switched to DDD due to high-degree (grade 2-3) AV block. The incidence of high-degree AV block was 1.104%/year, with a freedom rate of 88.6% at 10 years. There were no significant differences between the two groups in survival rates (87.8% in AAI vs. 93.4% in DDD at 10 years), freedom from atrial fibrillation (93.6% vs. 90.6%), or freedom from reoperation (71.3% vs. 76.3%). On the other hand, lead failure was twice as frequent in the DDD group than in the AAI group (relative risk=2.045, P=0.0382). CONCLUSION: AAI pacing, a simple system using a single lead and single-chamber pacemaker, can achieve a clinical outcome similar to that of the DDD mode in patients with SSS and normal AV conduction.     

不同起搏方式对心房电机械延迟影响的对比研究

了解双腔起搏 (DDD)患者右心耳起搏 (RAA)方式对心房电机械延迟 (AEMD)的影响。对 2 1例置入DDD的患者 ,用M型超声心动图结合同步心电图分别测量DDD方式及心房感知心室起搏 (VDD)方式下的AEMD。结果 :RAA起搏与窦性节律比较 ,AEMD明显增加 ,其中P波起始至中央纤维体 (CFB)运动发生的时间增加 2 8± 4ms、至CFB最大收缩振幅出现的时间增加 42± 3ms、至左房侧壁 (LLA)运动发生的时间增加 35± 5ms、至LLA最大收缩振幅出现的时间增加 34± 4ms (所有P <0 .0 0 1)。结论 :DDD患者右心耳起搏能明显增加AEMD     

双腔起搏器自动模式转换功能的临床应用

为观察双腔起搏器自动模式转换功能在房性心律失常治疗中的应用效果 ,对置入具自动模式转换功能起搏器的 31例患者分别于术后第 4天、1个月及每隔 3个月进行一次跟踪随访 ,观察房性心律失常的发生情况和起搏器自动模式转换情况及临床症状。全部病例随访 1～ 18个月 ,出现阵发性心房颤动、心房扑动及房性心动过速 76阵次 ,起搏器由DDD(R)自动转换成DDI(R)模式 72阵次 ,患者自觉心悸 8阵次。结论 :自动模式转换功能可使起搏器在患者发作房性心动过速时发挥对心室的保护作用 ,有效避免由于起搏器跟踪快速心房率而造成心室率过快引起的血流动力学改变 ,并能明显减轻心悸等临床症状 ,提高病人的舒适性和安全性。     

The effect of VVI pacing on P-wave dispersion in patients with dual-chamber pacemakers

The incidence of atrial fibrillation is higher in patients with VVI pacing mode than DDD pacing mode, but the likely mechanism is not clearly understood. We aimed to evaluate whether short-term VVI pacing increases inhomogeneous atrial conduction by using P-wave dispersion. Forty-seven patients (32 men, 15 women, mean age 54 ± 13 years) with DDD pacemakers were enrolled in this study. Twelve-lead surface ECGs were obtained in all patients during VDD pacing after an observation period of 1 week. The mode was then changed to VVI and 12 lead surface ECGs were obtained after another 1-week observation period. P-wave durations were calculated in all 12 leads in both VDD and VVI pacing modes. The difference between the maximum and the minimum P-wave duration was defined as the P-wave dispersion (PWD = P_max − P_min). P-wave maximum duration (P_max) calculated in VVI pacing mode was significantly longer than in VDD pacing mode (128 ± 19 vs 113 ± 16 ms, P < 0.001). There was no significant difference in the P-wave minimum durations (80 ± 13 ms vs 79 ± 12 ms, P = 0.7) between VVI pacing and VDD pacing. The P-wave dispersion value was higher in the VVI pacing mode than in the VDD pacing mode (48 ± 8 ms vs 34 ± 7 ms, P < 0.001). Short-term VVI pacing induces prolongation of P_max and results in increased P-wave dispersion, which might be responsible for the development of atrial fibrillation more frequently in these patients than in those with the VDD pacing mode.     

Randomized pilot study of a new atrial-based minimal ventricular pacing mode in dual-chamber implantable cardioverter-defibrillators

OBJECTIVE: We hypothesized that a new minimal ventricular pacing mode (MVP) that provides AAI/R pacing with ventricular monitoring and back-up DDD/R pacing as needed during AV block (AVB) would significantly reduce cumulative percent ventricular pacing compared to DDD/R. BACKGROUND: Conventional DDD/R mode often results in high cumulative percent ventricular pacing that may adversely affect ventricular function and increase risk of heart failure and atrial fibrillation. METHODS: MVP was made operational in 30 patients with DDD/R implantable cardioverter-defibrillators (ICDs) and no history of AVB. Patients were randomized to one week each in DDD/R and MVP. Holter monitor recordings (ECG, intracardiac electrograms, and event markers) and device diagnostics were analyzed for cumulative % atrial paced (Cum%AP), cumulative percent ventricular pacing, and frequency and duration of DDD/R pacing back-up. Diaries were used to report symptoms. RESULTS: Age of the study population was 61 years +/- 12 years and 83% were male. Baseline PR interval was 204 ms +/- 32 ms and programmed AV intervals (DDD/R) were 200 ms +/- 50 ms (paced)/167 ms +/- 54 ms (sensed). Cum%AP was similar between MVP and DDD/R (47.9 +/- 37 vs 46.3 +/- 36). Cumulative percent ventricular pacing was significantly lower in MVP vs DDD/R (3.79 +/- 16.3 vs 80.6 +/- 33.8, P < .0001). Back-up DDD/R pacing during MVP operation due to transient AVB occurred in 10% of patients (9.3 +/- 7.4 [range 1-15] episodes/patient-day, duration 39.7 minutes +/- 156 minutes). Fifteen percent of AV intervals during MVP operation exceeded 300 ms. No significant symptoms were reported during MVP operation. CONCLUSIONS: MVP dramatically reduced cumulative percent ventricular pacing compared to DDD/R while maintaining AV synchrony and providing sensor-modulated atrial pacing support. Intermittent oscillations between MVP and DDD/R during transient AV block appeared safe and well tolerated.     

A Novel Mechanism of Failure to Detect Atrial Arrhythmias by Pacemakers and Implantable Cardioverter Defibrillators

Failed Atrial Arrhythmia Detection by Pacemakers and ICDs. A 64‐year‐old man with complete heart block, status post‐Medtronic dual chamber pacemaker insertion, failed ablation for atrial tachycardia at an outside institution. Despite persistent palpitations and known unsuccessful ablation, pacemaker interrogation revealed no evidence of atrial arrhythmias. At electrophysiology study, burst pacing from the high right atrium and distal coronary sinus at 370 ms revealed bidirectional 2:1 interatrial conduction block. Left atrial burst pacing at 260 ms induced an atrial tachycardia (cycle length 340 ms) with 2:1 left to right atrial block and right atrial activation at 680 ms. The tachycardia was localized to the lateral left atrial roof. A series of ablation lesions from left to right superior pulmonary vein terminated the tachycardia. Left to right interatrial conduction block is a mechanism for underdetection of atrial arrhythmias with implantable devices not previously described. As the extent of atrial ablation increases, the incidence of this mechanism of underdetection may increase. Though devices are often considered ideal for atrial arrhythmia detection and are used in multiple trials, detection failures can occur despite appropriate device function. This case underscores the need for electrocardiographic monitoring in addition to device‐based electrogram monitoring. (J Cardiovasc Electrophysiol, Vol. 21, pp. 325–328, March 2010)     

The electromechanical effects of pacing at different sites within the right atrium.

AIMS: To compare high right atrium (HRA) with right atrial appendage (RAA) pacing with respect to atrial electromechanical function. METHODS: Eleven patients undergoing elective electrophysiological studies were studied in order directly to compare atrial conduction acutely associated with HRA and RAA pacing. Twenty-five patients with chronically implanted, active fixation leads in the HRA were compared with an age and sex matched group of 25 patients with chronically implanted, passive fixation leads in the RAA. For both studies recordings were taken in sinus rhythm then repeated when paced. Measured time intervals were intra- and interatrial activation times. P wave duration and time to onset of atrial systolic blood flow. RESULTS: Right atrial pacing, when compared with sinus rhythm, significantly prolongs the interatrial activation time, the P wave duration and the time to onset of right and left atrial blood flow irrespective of site paced. Comparing the RAA group with the HRA group, there were no statistical differences for any of the measured parameters. CONCLUSION: High right atrial free wall or the right atrial appendage pacing, when compared with sinus rhythm, is significantly detrimental to atrial electromechanical function. There is, however, no demonstrable difference between the two sites.     

Antiarrhythmic benefits of dual chamber stimulation with rate-response in patients with paroxysmal atrial fibrillation and chronotropic incompetence: a prospective, multicentre study.

BACKGROUND: While the haemodynamic benefits of DDDR pacing compared with DDD pacing in patients with brady-tachy syndrome and chronotropic incompetence (CI) are well demonstrated, the antiarrhythmic advantage is controversial and so far not clearly demonstrated. AIM: We have performed a prospective, randomized, multicentre study to evaluate the efficacy of DDDR and DDD pacing modes in preventing paroxysmal atrial fibrillation (PAF) episodes in patients with brady-tachy syndrome and CI. METHODS AND RESULTS: Seventy-eight patients were included in the study. All patients had a dual chamber pacemaker implanted and were randomly programmed to DDD or DDDR with a cross over (DDD --> DDDR or vice versa) at 3 months. The final evaluation was performed at 6 months by means of two self-administered symptom questionnaires to evaluate activity. Symptoms of palpitations were analysed and scored. The patients were less symptomatic with the DDDR mode. The number of mode-switch activations compared with symptomatic episodes of PAF confirmed the high rate of asymptomatic PAF episodes in patients with brady-tachy syndrome. We conclude that in a small but well defined population of patients affected by sick sinus syndrome with CI and severely symptomatic PAF, DDDR pacing compared with DDD pacing may offer an additional antiarrhythmic benefit and should be considered the primary mode of pacing.     

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