Atrial pacing and sensing characteristics in heart failure patients undergoing cardiac resynchronization therapy.

Patients with heart failure and sinus rhythm undergoing cardiac resynchronization therapy (CRT) require the proper detection of atrial signals and reliable atrial pacing for AV-synchronous ventricular pacing. The study aim was to compare atrial pacing and sensing characteristics in patients with transvenous CRT and patients with standard pacing indications. METHODS: The study group consisted of 31 heart failure patients with depressed left ventricular function and bundle branch block, and the control group of 124 patients with dual-chamber pacemakers because of standard pacing indications. The bipolar steroid-eluting atrial screw-in lead Tendril DX 1388 T (St. Jude Medical) was implanted and connected to pulse generators that provide similar diagnostic features. The unipolar pacing threshold at 0.4 ms duration, bipolar sensing threshold, and unipolar pacing impedance were determined at implantation and after 1, 3, and 6 months. RESULTS: At implantation, the atrial pacing threshold was significantly higher in the CRT group than in the control group, 1.07+/-0.99 V versus 0.74+/-0.36 V (P<0.01). Similar pacing thresholds were recorded after 1 month. The pacing threshold in the CRT group was significantly higher at 1.46+/-0.92 V after 3 and 1.50+/-0.94 V after 6 months (control group: 0.96+/-0.25 V at month 3; 0.98+/-0.32 V at month 6; P<0.05). Sensing threshold was similar at implantation with 2.36+/-1.87 mV in the CRT and 2.54+/-0.78 mV in the control group. The sensing threshold in the CRT group decreased to 1.64+/-0.8 6mV after 3 and to 1.71+/-0.71 mV after 6 months and was significantly lower compared with the control group (2.16+/-0.57 mV at month 3; 2.27+/-0.9 8mV at month 6; P<0.05). At implant, the atrial pacing impedance was not different between the two groups with 443+/-156 ohms in the CRT and 416+/-116 ohms in the control group. During follow-up, the impedance became significantly lower in the CRT group compared with the control group (404+/-84 ohms versus 452+/-101 ohms at month 3; P<0.05). CONCLUSIONS: Compared with patients with standard pacing indications, CRT recipients have less good electrical characteristics in the atrium. Atrial pacing and sensing function should be closely monitored in CRT patients.     

Placement of atrial pacing leads during atrial fibrillation. Feasibility and subsequent lead performance.

AIMS: To assess the feasibility of placing permanent atrial pacing leads during atrial fibrillation (AF) and whether such leads function satisfactorily. METHODS AND RESULTS: Prospective study of 17 consecutive patients in whom permanent atrial leads were positioned during an episode of paroxysmal AF. Fluoroscopic position ('figure of 8' or side-to-side movement and anterior position in RAO projection), lead impedance (> 300 but < 1000 ohms) and intracardiac electrogram (average peak to peak amplitude > 1 mV) were used to define an acceptable lead position. At 8 weeks post implant we measured: pulse duration pacing threshold at 5 V; lead impedance at 5 V and 0.5 ms; intracardiac electrogram (EGM) signal amplitude. At the end of the study we reviewed patients to establish whether AF had become permanent. In all patients, follow-up demonstrated satisfactory lead function. All leads had impedances between 300 and 1000 ohms. Pacing thresholds were all < 0.1 ms at 5 V. Mean atrial EGM amplitude seen in sinus rhythm was 3.3 mV (range 1.2-8.4); in patients where all follow-up was in AF in was 2.1 mV (range 1.5-2.5). Nine patients (53%) developed permanent AF. CONCLUSION: Placing atrial leads during AF is feasible using the technique described. However, some patients progress to chronic AF, eliminating the benefits of atrial pacing.     

Steroid-eluting epicardial pacing leads in pediatric patients: encouraging early results.

OBJECTIVES. This study evaluated the pacing and sensing characteristics of a new porous-tipped steroid-eluting epicardial lead in a group of pediatric patients. BACKGROUND. Pacing in children may be complicated by small patient size, patient growth and the prevalence of structural congenital heart disease in children requiring pacing. Epicardial pacing has been associated with a high incidence of problems with sensing and capture, prompting the use of transvenous endocardial pacing when possible. In some children, epicardial pacing may still be desirable because of small patient size, potential for caval obstruction, previous cardiac surgery limiting transvenous access to the heart, or the need to repair congenital heart disease at the time of pacemaker insertion. METHODS. Twelve patients aged 3 weeks to 18 years underwent placement of 23 epicardial pacing leads (8 atrial, 15 ventricular). Pulse width thresholds, sensing thresholds and lead impedance were measured weekly for 6 weeks, then at 3, 6, 12 and 18 months after pacemaker implantation. The median duration of follow-up was 12 months. RESULTS. Ventricular pulse width thresholds did not change over time, whereas atrial pulse width thresholds improved significantly. At 6 months, the mean pulse width threshold at 2.5 V for the atrial and ventricular leads was 0.10 +/- 0.03 and 0.19 +/- 0.09 ms, respectively. The thresholds were slightly lower at 12 and 18 months. At the most recent follow-up, all atrial leads sensed appropriately at 2.5 mV and all ventricular leads at 5 mV. CONCLUSIONS. These encouraging early results suggest that steroid-eluting epicardial pacing leads may be an attractive option for children needing epicardial pacing. Their excellent pacing and sensing characteristics may allow reliable dual-chamber pacing in infants who are too small for transvenous pacing.     

Acute and chronic stability of atrial screw-in leads

The purpose of this study was to evaluate the acute and chronic stability of the atrial screw-in lead. In this study, we used CPI model 4165, 4166, and 4266 porous tip screw-in leads in 32 patients (12 for AAI pacing and 20 for DDD pacing). All of these leads were fixed to the free wall of the right atrium and used as the unipolar type. Acute voltage and current thresholds, lead impedance, P-wave amplitude, and chronic threshold were measured. Early and late complications were also investigated. The average acute stimulation thresholds at 0.6 msec pulse width were 0.82 +/- 0.43 V and 1.1 +/- 0.6 mA. Mean lead impedance was 627.2 +/- 83.1 ohms, and mean P wave amplitude was 3.1 +/- 1.1 mV. After an average follow-up period of 32 months (range: 2-72 months), we found the results of the chronic threshold study to be satisfactory. The thresholds were usually below 0.1 msec pulse width with the nominally programmed pacemaker output. Only one patient required a higher output due to an increased threshold. With regard to complications, neither lead dislodgment nor cardiac perforation was observed. In conclusion, acute and chronic thresholds were satisfactory and no serious complications occurred. Therefore the atrial screw-in lead has long-term reliability and stability.     

植入起搏电极参数的测定和随访

为了解起搏阈值、起搏阻抗和感知阈值的变化，对４２根心房电极和４９根心室电极进行了随访。结果显示：心房电极慢性期起搏阈值为１．１７±０．３５Ｖ／０．５ｍｓ，出现波动者６例（２７．３％），心室电极为１．２７±０．３８Ｖ／０．５ｍｓ，出现波动者７例（３０．４％）；１９根电极的起搏阻抗在急性期均有波动，慢性期为５８５．６±１５０Ω，慢性期出现波动者２例（１０．５％）；１１根心房电极慢性期感知阈值（Ｐ波振幅）与植入时相一致。     

A comparison between passive and active fixation leads in the coronary sinus for biatrial pacing: initial experience.

AIMS: It has been reported that biatrial pacing can prevent the recurrence of atrial fibrillation. This technique requires a stable coronary sinus (CS) lead position for left atrial pacing. We report our experience of CS pacing with a specifically designed lead [Medtronic 2188 (n= 19)] and active fixation leads [Pacesetter Tendril (n=3), Medtronic Capsurefix (n=6)] in 21 patients with paroxysmal atrial fibrillation and a normal mean left atrial size of 39 mm (range 33-54 mm). METHODS AND RESULTS: Using the Medtronic 2188 lead, successful initial CS canulation and lead positioning was achieved in all 19 patients. One patient developed subclavian vein thrombosis 3 months after initial implant. Eight patients (42%) experienced subsequent lead displacement (12 displacements in total). Of these, seven had their lead replaced with active fixation leads. In addition, two patients underwent active fixation lead implantation at first implant. CS canulation and lead positioning was successful in all nine patients. No patient suffered displacement of an active fixation lead. There were no complications in this group. Twelve of the 19 (66%) Medtronic 2188 leads were functioning at long-term follow-up (11 +/- 4 months) with a biatrial pacing threshold of 2.4 +/- 1 V. Eight of the nine (89%) active fixation leads were functioning at long-term follow-up (6 +/- 3 months) with a biatrial pacing threshold of 2.9 +/- 1.1 V. Using a combined approach 95% of patients had a functioning CS lead at long-term follow-up. CONCLUSION: Active fixation leads can safely be used for left atrial pacing via the CS with good long-term pacing thresholds and stability.     

Single-lead VDD-pacing system incorporating high impedance stimulation: a multicentre study.

AIM: The purpose of this study was to evaluate the performance of a new VDD pacing system incorporating a high impedance, single-pass VDD lead. The new lead is a bipolar, steroid-eluting, high impedance lead with a full-ring atrial dipole. METHODS AND RESULTS: The system was implanted in 46 patients with high degree atrioventricular (AV) block. Patients were followed at pre-discharge, 6 weeks, and 3 months. The mean measured P-wave amplitude was stable, with values between 1.18 and 1.43 mV. Atrial sensing was reliable during short-term evaluation at rest and in the sitting position, with AV-synchronous stimulation between 98.79 +/- 6.90% and 99.73 +/- 1.47%. Holter recordings after 6 weeks demonstrated AV-synchronous stimulation in 99.57 1.03% of all P-waves. Lead impedance was stable during follow-up, with mean values between 1000 and 1167 Q. Mean ventricular pacing thresholds (at 0.5 ms) were 0.47 V at implant, 0.49 V at pre-discharge, 0.74 V at 6 weeks, and 0.72 V at 3 months. R-wave amplitude remained stable between 14.9 and 16.7 mV during follow-up. CONCLUSION: This new single-pass VDD lead system provided reliable atrial sensing and stable high impedance stimulation during a 3-month follow-up period.     

First worldwide clinical experience with a new dual chamber implantable cardioverter defibrillator. Advantages and complications. The Ventak AV II DR investigators.

AIMS: The need for physiological pacing and for improving the ability to discriminate atrial from ventricular tachyarrhythmias has prompted the development of dual chamber implantable cardioverter/defibrillators (ICDs). METHODS: Fifty-two patients were implanted with a newly developed dual-chamber ICD providing rate-responsive physiological pacing (Ventak AV II DR). The device possesses two new arrhythmia detection algorithms ('atrial fibrillation rate threshold' and 'ventricular to atrial rate relationship') in addition to commonly used features such as 'onset' and 'stability'. During implantation, the atrial and ventricular lead impedances and pacing thresholds were determined together with the defibrillation threshold. Prior to discharge, attempts were made to induce both atrial and ventricular tachyarrhythmias in order to test those new detection criteria. All patients were followed for at least 3 months. RESULTS: The device was successfully implanted in all 52 patients. Placement of the atrial lead was successful in 50/52 patients (96%; P-wave 3.2 +/- 1.4 mV; impedance 576 +/- 123 omega; atrial pacing threshold 1.2 +/- 0.9 V). Prior to discharge, 32 episodes of atrial fibrillation (AF) alone, 38 episodes of AF with ventricular fibrillation and 10 episodes of AF with monomorphic ventricular tachycardia were induced in 33/50 patients (66%) and all were appropriately classified by the detection algorithm. During the 3 months follow-up, 12 patients (23%) had appropriate and successful therapies for ventricular arrhythmias, while four patients (8%) experienced inappropriate ICD therapies. Although all these episodes were detected correctly as supraventricular arrhythmias by the device, therapy was delivered because of incorrect or incomplete programming. In all cases reprogramming of the device resolved the problem. CONCLUSION: Implantation of dual chamber ICDs is feasible and appears to improve discrimination of supraventricular from ventricular tachyarrhythmias. In addition, patients with tachyarrhythmias and concomitant bradyarrhythmias may benefit from simultaneous physiological pacing. However, implantation and follow-up of such patients should be performed at experienced centres since both surgical handling and programming of these devices is more difficult and complex than conventional ICDs.     

起搏器心房自动阈值管理功能的临床研究

目的:通过对植入起搏器患者的随访,了解心房自动阈值管理功能的可靠性和安全性。方法:选择植入Medtronic Enpulse双腔起搏器的患者43例,于植入起搏器后的1、3、6个月分别程控随访,用人工测定法和自动测定法测定起搏器的心房输出阈值、感知和导线阻抗。结果:植入起搏器1、3、6个月后,随访时人工测定和自动测定的心房输出阈值分别为(0.60±0.26)V与(0.60±0.23)V、(0.55±0.19)V与(0.56±0.18)V、(0.58±0.20)V与(0.59±0.21)V,差异无统计学意义;且心房感知度和导线阻抗的人工测定与自动测定间无差异。在心房自动起搏阈值测定过程中未诱发任何心律失常。结论:起搏器的心房自动阈值管理功能的临床应用是可靠和安全的。     

埋藏式心脏起搏器置入术后电极阻抗的动态变化及其临床意义

目的　观察埋藏式心脏起搏器置入术后起搏电极阻抗的动态变化规律 ,并探讨其机制及临床意义。方法　对 2 0 0 3年 4月至 2 0 0 3年 10月期间在我院接受埋藏式心脏起搏治疗的 33例患者分别于术中、术后 1w、2w、1个月、2个月、3个月和 6个月测定电极阻抗 ,同时随访起搏器功能状态。结果　 19条MedtronicCAPTURE SP(MCSP)系列心房激素电极阻抗术后均较术中明显降低 ,且差异具有显著性(P <0 0 1) ,术后 1w至 6个月无明显变化 ;2 4条MCSP系列心室激素电极阻抗亦表现出同样的变化趋势。 9条BIOTRONIKSYNOXSX(BSSX)系列高阻抗非激素心室电极阻抗术后亦均较术中明显降低 (P <0 0 1) ,术后 2w最低 ,其与术后 1、2和 3个月比较具有显著性差异 (P <0 0 5 )。所有患者起搏器起搏、感知功能均正常。结论　埋藏式心脏起搏器置入术后电极阻抗于 1w时开始明显降低 ,此后 6个月激素电极阻抗保持稳定 ,而非激素电极在正常范围内出现较大波动 ,但并不影响起搏器正常工作。     

Autocapture compatibility in patients with the MembraneEX lead and Affinity pulse generators.

The first Autocapture generation worked well with all recommended leads. The newer Autocapture generation provides a more sensitive resolution for evoked response testing and its implementation in a dual-chamber device. The purpose of the study was to evaluate the performance of the Affinity SR/DR pacemaker with the new Autocapture algorithm in combination with the small surface area pacing lead MembraneEX in 129 patients. Autocapture ventricular threshold, sensing threshold, lead impedance, evoked response (ER) and polarization signals were determined at implantation and discharge, as well as after 1 and 3 months. Autocapture recommendation rate was based on the ER sensitivity test. The median pacing threshold was 0.38, 0.50, 0.75, 0.75 V at implant, discharge, 1 and 3 months post-implant, respectively. The respective data for median lead impedance were 744, 605, 649 and 691 ohms; median sensing threshold was 12.5 mV at all visits. The median ER amplitude was 9.0, 10.1, 9.9 and 10.1 mV and the median polarization signal 0.39 mV at all visits. The frequency of recommended Autocapture activation was 98.3%, 99.2%, 98.3% and 96.2% of all patients at implant, at discharge, 1 and 3 months post-implant respectively. In conclusion, the studied pulse generator enabled, in combination with this pacing lead, in >95% of all patients activation of Autocapture.     

Single-centre experience with coronary sinus lead stability and long-term pacing parameters.

AIMS: To compare both short- and long-term stability and pacing parameters of CS leads. Long-term maintenance of coronary sinus (CS) pacing lead position has not yet been assessed by serial X-ray digital imaging. METHODS AND RESULTS: Using X-ray digital imaging in anteroposterior and left lateral views, we performed analysis of the CS lead position at the end of the implantation procedure, 48 h following implantation and after 12 months in 93 consecutive patients. Attain OTW leads, QuickSite leads and EasyTrak leads were implanted in 44, 12 and 37 cases, respectively. X-ray detectable late CS lead dislodgement was observed in 8 cases (8.6%) during 12-months follow-up. Dislodgment was once accompanied by loss of capture and need for repositioning. Another two major dislodgements occurred without any threshold change. Five (5.4%) minor dislocations occurred with either a decrease or an increase in pacing threshold. Left ventricular (LV) pacing threshold was changed by >or= 1 V after 12 months in 14 patients (15%) when compared to values 48 h after implantation. All but one case of >or= 1 V threshold change (either positive or negative) occurred without any radiological evidence of lead displacement. LV pacing threshold was significantly higher than RV pacing threshold at both baseline and during follow-up. Leads from all three manufacturers had comparable pacing thresholds 12 months following implantation. CONCLUSION: The position of CS leads may change during 1-year follow-up. However, it rarely required reoperation in the selected group of patients. Long-term pacing parameters between different manufacturers are comparable. Increase in pacing threshold is not a reliable marker of CS lead dislodgement.     

植入型心律转复除颤器导线故障分析

目的总结分析我院植入型心律转复除颤器（ICD）起搏除颤导线故障病例特点。方法对2005年10月至2009年12月62例在我院新植入ICD导线患者进行随访分析,所有导线植入均以锁骨下静脉作为入路。随访中出现以下1项或多项异常考虑导线故障：（1）起搏阻抗永久性或间歇性〉2000n或〈250Q;（2）除颤高压阻抗〉200n;（3）心内电图证实除颤导线感知非生理性高频噪声导致误放电。结果中位数随访时间28（10～46）个月,4例患者（6．5％）诊断ICD导线故障,导线寿命18～38个月;临床均以ICD误放电至医院就诊,同时程控发现ICD导线起搏阻抗异常。其中1例患者放电前闻及ICD导线阻抗报警,4例患者均重新植入新的起搏感知导线。结论ICD导线故障是一个值得重视的临床问题。ICD导线阻抗报警功能可能有助于早期发现导线故障。如程控发现仅仅除颤导线起搏阻抗异常,植入新的起搏感知导线可以作为首选的故障处理方法。     

Robotically assisted left ventricular epicardial lead implantation for biventricular pacing

OBJECTIVES: Ventricular resynchronization might be achieved in a minimally invasive fashion using a robotically assisted, direct left ventricular (LV) epicardial approach. BACKGROUND: Approximately 10% of patients undergoing biventricular pacemaker insertion have a failure of coronary sinus (CS) cannulation. Rescue therapy for these patients currently is limited to standard open surgical techniques. METHODS: Ten patients with congestive heart failure (New York Heart Association class 3.4 +/- 0.5) and a widened QRS complex (184 +/- 31 ms) underwent robotic LV lead placement after failed CS cannulation. Mean patient age was 71 +/- 12 years, LV ejection fraction (EF) was 12 +/- 6%, and LV end-diastolic diameter was 7.1 +/- 1.3 cm. Three patients had previous cardiac surgery, and five patients had a prior device implanted. RESULTS: Nineteen epicardial leads were successfully placed on the posterobasal surface of the LV. Intraoperative lead threshold was 1.0 +/- 0.5 V at 0.5 ms, R-wave was 18.6 +/- 8.6 mV, and impedance was 1,143 +/- 261 ohms at 0.5 V. Complications included an intraoperative LV injury and a postoperative pneumonia. Improvements in exercise tolerance (8 of 10 patients), EF (19 +/- 13%, p = 0.04), and QRS duration (152 +/- 21 ms, p = 0.006) have been noted at three to six months follow-up. Lead thresholds have remained unchanged (2.1 +/- 1.4 V at 0.5 ms, p = NS), and a significant drop in impedance (310 +/- 59 ohms, p < 0.001) has been measured. CONCLUSIONS: Robotic LV lead placement is an effective and novel technique which can be used for ventricular resynchronization therapy in patients with no other minimally invasive options for biventricular pacing.     

心脏起搏器主动与被动固定电极置入后参数的变化

目的比较主动固定电极(螺旋电极)与被动固定电极术后各参数的变化。方法对18例接受被动固定电极及15例螺旋电极置入的患者,分别于术中;术后1,2周;1,2,3,6个月在平静状态下测定起搏阈值,A、V波振幅及阻抗。结果15例放置螺旋电极者,术后心房、心室阈值较术中下降(P<0.05);18例放置被动固定电极者,心房及心室电极术后起搏阈值无明显变化;全部33例术中;术后A、V波振幅测定值均无显著性差异(P>0.05);所有患者术后阻抗较术中明显降低(P>0.05),术后1周至6个月电极阻抗稳定,未出现显著性变化。结论安置螺旋电极者起搏阈值较术中下降,安置被动固定电极组起搏阈值无明显变化;而电极阻抗均较术中明显下降,长期随访稳定。     

Long-term follow-up of pacemakers with an Autocapture pacing system

The aim of this study was to evaluate the safety and performance of the Autocapture pacing system during a 5-year follow-up period. The study was conducted retrospectively between May 1996 and May 2001. Sixty consecutive patients who had undergone VVI pacemaker implantation using an Autocapture program with leads 1402T (n: 31) and 1452T (n: 29) were included in the study. Intraoperative measurements including a ventricular stimulation threshold test, sensing of intrinsic R wave (mV), and lead impedance (W) were done by a standard pacing system analyzer. Evoked responses (ER, mV) and polarization signals (PS, mV) were measured after the pocket was closed. Pacing thresholds by Autocapture (AC thrd, V) and Vario (Vario thrd, V), battery current (mA), and battery impedance (kW) were also repeated during predischarge and 1, 6, 12, 18, 24, 30, 40, 50, and 60 months after discharge. According to the ER and PS values an Autocapture algorithm could be activated in 49 patients (88%). The Autocapture algorithm remained active during the follow-up in all of these patients. In patients with inappropriate ER and PS values (11 patients, 12%), pacemakers were programmed to a VVIR pacing mode and Autocapture algorithm was inactivated. ER and PS values did not reach appropriate values to activate the Autocapture algorithm in any of these patients in consecutive follow-ups. Twenty-four-hour Holter monitoring could be conducted in 32 patients (53%). In all recordings, when the loss of capture occurred, it was confirmed that back-up pacing continued. When the first measurements recorded during implantation were compared to approximately the 5th year measurements; ER (9.2 mV vs 9.6 mV), PS signal (1.13 +/- 0.30 mV vs 1.15 +/- 0.72 mV), AC thrd (0.4 V vs 1.2 V), Vario thrd (0.7 V vs 1.3 V), and lead impedance (502 ohm vs 620 ohm) were not changed significantly. Battery impedance increased 1 kOhm between 30-40 months of the implantation. Seven deaths occurred during follow-up. Three patients had fatal myocardial infarction, one died due to a non-cardiac event, and the remaining three died due to progressive heart failure. Conclusion: ER, R wave amplitude, and PS, which are the main parameters for the continuation of Autocapture function, did not change significantly during long-term follow-up. High output back up pacing provided additional safety for sudden rises in threshold. The Autocapture pacing algorithm was found to be effective and reliable during long-term follow-up.     

Acute performance of steroid-eluting screw-in leads for atrial free wall pacing.

The aim of this study was to clarify the acute performance of steroid-eluting screw-in leads in comparison with that of nonsteroid screw-in leads for atrial free wall pacing. In 114 cases (68 males, 46 females, average age 70 years) with atrial free wall pacing by screw-in leads, pacing thresholds and P-wave amplitudes were compared at the time of implantation and 1 week later between 68 cases of nonsteroid and 46 cases of steroid-eluting screw-in leads. No significant differences were seen between the 2 groups at implantation in either voltage or current thresholds measured at pulse widths of 0.1, 0.3, 0.6, 1.0, 2.0 ms, or P-wave amplitudes. Pulse width thresholds at outputs of 2.5 V and 5.0 V were significantly lower for steroid leads 1 week after implantation (2.5 V: 0.34+/-0.27 ms nonsteroid vs. 0.12+/-0.08 ms steroid, p<0.001; 5.0 V: 0.12+/-0.08 ms nonsteroid vs. 0.06+/-0.02 ms steroid, p<0.01). P-wave amplitudes after 1 week were significantly higher for steroid leads (2.6+/-0.7 mV nonsteroid vs 3.0+/-1.2 mV steroid, p<0.001). Threshold rise, including pacing failure, was observed in 15 (22%) of the non-steroid leads, but in only 1 (2%) of the steroid leads. In conclusion, steroid-eluting screw-in leads suppress the acute rise of pacing thresholds in the right atrial free wall and their acute performance is better than that of non-steroid leads. These results suggest that appropriate low-output atrial pacing is feasible immediately after implantation.     

Stabilization of the coronary sinus lead position with permanent stylet to prevent and treat dislocation.

AIMS: Coronary sinus (CS) leads used for cardiac resynchronization have undergone development in the last years. However, dislocation rate remained high. We explain a simple method to stabilize the CS lead position. METHODS AND RESULTS: Thirty-five patients (11 females, aged 60 +/- 9.2 years) were treated with this method. An over-the-wire left ventricular (LV) pacing lead system was introduced and lodged in the vessel. Then, a stiff stylet was inserted and kept into the CS lead and end of the stylet was cut by a scissor (permanent stylet technique). Pacing and sensing properties of all leads were checked and the guiding sheath was removed. Control echocardiography did not show pericardial effusion. The mean LVpacing threshold was 1.2 +/- 0.8 V and the mean impedance was 625 +/- 143 Omega at the implantation. During follow-up (12.5 +/- 2.5 months), there were no statistically significant changes in pacing threshold and impedance when compared with the implantation measurements. At the last patient visit, the mean LV pacing threshold was 1.1 +/- 0.8 V and the mean impedance was 620 +/- 140 Omega. Impedance measurements did not suggest lead insulation failure. No LV lead dislocations were detected in our 35 cases during the follow-up. CONCLUSION: Permanent stylet technique seems to be a safe and effective procedure to stabilize CS lead position as demonstrated by our 1-year long follow-up results.     

Short and long-term single-centre experience with an S-shaped unipolar lead for left ventricular pacing.

Left ventricular-based pacing is an established method for treatment of congestive heart failure in patients with ventricular dyssynchrony. The transvenous epicardial approach is the method of choice to pace the left ventricle. AIMS: To evaluate short and long-term stability and pacing and sensing performance of an S-shaped non-steroid unipolar lead. METHODS: Forty-eight procedures were performed in 43 consecutive patients (mean age: 70+/-8 years, 32 males) with severe congestive heart failure. The left ventricular lead was placed into a coronary sinus tributary. Pacing and sensing thresholds and pacing impedance were measured at implant, 1 and 6 months. RESULTS: The mean procedure time was 90.0+/-35.5 min. Pacing thresholds at implant, 1 and 6 months were 1.1+/-0.8 V, 1.9+/-1.3 V and 1.9+/-1.5 V respectively. In 7 patients, lead implantation was unsuccessful. One of them had a successful second attempt. Lead revision was performed in 5 patients for loss of capture. CONCLUSION: The S-shaped unipolar lead evaluated in this study provides stable long-term position and pacing thresholds. Recent improvement of this S-shaped lead model will hopefully reduce the rate of implantation failures and acute dislodgements.     

Comparison of Atrial Leads: Importance of Polarity and Fixation Mechanism

To compare the influence of polarity and fixation mechanism on atrial leads, we evaluated acute implantation and 12-month follow-up results in 211 patients, 138 male and 73 female, aged 63 ± 14 years, implanted with DDD (210) and AAI (1) pacemakers. Eighty patients had bipolar (B) active fixation (AF) leads (CPI-4266), 71 had unipolar (U) AF (Medtronic-6957J), 36 had B passive fixation (PF) (Medtronic-4512), and 26 had U PF (Medtronic-4511) leads. Acutely, capture thresholds were higher in the AF than the PF group (BAF: 1.0 ± 0.5 V; UAF: 0.9 ± 0.4 V; BPF: 0.6 ± 0.2 V; UPF: 0.5 ± 0.1V - P < 0.001). The BPF lead acute sensing threshold was superior to the AF leads (P wave sensing for BPF: 3.2 ± 1.5 mV; BAF: 2.2 ± 1.2 mV; UAF: 2.2 ± 1.1 mV - P < 0.003). In both AF and PF groups, lead polarity did not affect pacing and sensing thresholds. The difference in acute capture thresholds between AF and PF leads was abolished prior to discharge, and at subsequent follow-up over 12 months, no difference in chronic thresholds was observed. During the follow-up period, the chronic sensing thresholds of BAF leads were superior to the others. There was no significant difference in the complication rates of the four leads. Thus, all four leads proved satisfactory in clinical practice. No major impact of polarity and fixation mechanism was detected.