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.     

Progressive improvement of atrial and ventricular capture thresholds,sensing, and impedances in epicardial pacing leads in young adults undergoing Fontan conversion

Objectives:Patients with univentricular hearts who require permanent pacing systems typically require placement of epicardial leads. It is frequently difficult to find a position with good thresholds due to epimyocardial fibrosis or fat. The goal of the study is to assess the progression of capture thresholds (CT), sensing parameters (P waves and R waves), and impedances (imp) of steroid eluting epicardial pacing leads in young adults who underwent Fontan conversion and a pacemaker implant.Methods:All patients undergoing Fontan conversion in two institutions were retrospectively identified. Demographic data, congenital heart defects, pacing leads used, and pacing parameters were analyzed at implant, at 6 weeks and 12 months after implant.Results:Twenty patients were identified (twelve males); mean age at conversion was 24.9 ± 5.4 years (range 18-35). Epicardial bipolar steroid eluting leads were used. The site of implant both in the atria and the ventricles varied depending on the parameters. At implant, mean atrial and ventricular impedances were 617 ± 171 W and 1061 ± 771 W, respectively, mean P wave amplitude was 2 ± 0.7 mV, and mean R wave amplitude was 12.5 ± 7.7 mV. Mean CT was 1.7 ± 0.8 V at 0.5 ms for the atrium and 2.2 ± 1.2 V at 0.5 ms for the ventricle. Ventricular CT and impedance showed an improvement within the first 12 months after implant, with four patients having a decrease in threshold of more than 2 V.Conclusion:In patients undergoing Fontan conversion, implant ventricular CT and impedances are frequently higher than expected but typically improve during follow-up. Acceptance of higher initial threshold values may be a potential strategy in this patient population.Key words: Fontan conversion, Pacing, Parameters, Progression     

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.     

Clinical surveillance of a thin bipolar pacing lead

A total number of 415 co-radial, bipolar pacing leads (189 atrial leads; 226 ventricular leads) were implanted in 228 patients between November 1994 and July 1999. Mean pacing thresholds at the implantation were normal at 0.6 V in the atrium and at 0.4 V in the ventricle with a pulse duration of 0.4-0.5 ms. Lead impedance was relatively low (337-447 ohms for atrial leads; 369-459 ohms for ventricular leads) at the implantation and during the follow-up periods. No definite failure in lead materials was observed in either atrial or ventricular leads (mean follow-up of 19.7 and 19.2 months, respectively: up to 52.9 months for both leads). Predicted clinical surveillance up to 10 years calculated statistically showed that the upper 95% confidence limit was a constant of 100%. The lower 95% confidence limits at 5, 7, and 10 years were estimated to be 98.0%, 97.2%, and 96.0%, respectively. From the present study, the ThinLine lead is reliable for both sensing and pacing thresholds, and has excellent predicted lead longevity. Nevertheless, further observation is required regarding cost performance, such as early replacement of the pacemaker generator, because of the lower pacing lead impedance.     

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.     

动脉硬化疾病患者右室流出道起搏的探讨

目的探讨动脉硬化疾病患者适宜的起搏部位。方法7例(冠心病3例、高血压4例)置入翼状电极至右室心尖部后起搏及感知功能障碍的患者,重置螺旋电极至右室流出道,观察其前后的起搏及感知功能。结果7例右室流出道起搏的起搏阈值较右室心尖部起搏显著降低,感知阈值较右室心尖部显著升高(0.5±0.2Vvs8.7±1.6V,10.6±3.6mVvs2.7±0.8mV,P<0.01),阻抗无明显差异。随访16±6个月,无电极脱位,起搏感知功能良好。结论右室流出道可作为有动脉硬化病史患者的起搏部位。     

Long-term performance of single-pass physiological pacing.

BACKGROUND: Single-pass physiological pacing has several advantages over dual-lead physiological pacing. The present study evaluated the long-term performance of single-pass pacing using the overlapping biphasic impulse stimulation technique. METHODS AND RESULTS: A total of 30 patients with single-pass VDD pacing and 8 patients with single-pass DDDC pacing were followed up for 1 year by basal and magnet electrocardiograms and real-time telemetry. All the patients showed satisfactory atrial sensing and pacing capture threshold. The atrial sensing thresholds at implant and at 1 month, 3 months, 6 months and 12 months of follow-up were 2.5+/-0.67 mV, 1.6+/-0.6 mV, 1.1+/-0.5 mV, 1.0+/-0.5 mV and 1.0+/-0.04 mV, respectively. The corresponding values for atrial pacing threshold at a pulse wave of 0.5 ms were 2.5+/-1.0 V, 4.4+/-0.9 V, 3.8+/-1.2 V, 3.6+/-1.4 V and 3.8+/-1.4 V. Of the patients with DDDC pacing, 88% showed stable pacing capture in the supine position, 75% in the upright position and 62% in both positions. Diaphragmatic contraction was seen in 25% of cases with DDDC pacing. No such event was seen in patients with VDD pacing. CONCLUSIONS: Single-pass pacing is safe, technically easy and cheap as compared to dual-lead systems. However, it would be prudent to recommend DDDC pacing in patients who require predominantly VDD pacing and only occasionally atrial pacing, as the latter showed a low percentage of stable atrial pacing capture in both upright and supine positions as well as a significant percentage of diaphragmatic contraction.     

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.     

Patient, procedural, and hardware factors associated with pacemaker lead failures in pediatrics and congenital heart disease

OBJECTIVES: To examine outcomes of children with pacemakers over a 22-year period and identify risk factors for lead failure. BACKGROUND: Small patient size, structural cardiac abnormalities, and growth may complicate pediatric pacemaker management. Better knowledge of risk factors for lead failure in these patients may help improve future outcomes. METHODS: All pacemaker patients followed at one pediatric center 1980-2002 were included. Lead failures were identified retrospectively as leads repaired, replaced, or abandoned due to fracture, insulation break, dislodgement, or abnormalities in pacing or sensing. Risk factors were identified using logistic regression and Cox analyses. RESULTS: A total of 1007 leads were implanted in 497 patients during the study period (5175 lead-years). Median age at implant was 9 years (0-55); 64% of patients had structural congenital heart disease. Median follow-up time was 6.2 years (0-22). Lead failure occurred in 155 leads (15%), and 115 patients (23%), with 28% of patients experiencing multiple failures. Significant independent correlates of lead failure included age <12 years at implant, history of structural congenital heart defects, and epicardial lead placement. Younger patients (<12 years) experienced significantly more lead fractures than older children (P = .005), while patients with congenital heart defects experienced more exit block. Epicardial leads were more likely to fail due to fracture or exit block, while transvenous leads failed more due to insulation breaks or dislodgements. CONCLUSIONS: Pediatric pacing patients have a high incidence lead failures. These occur most commonly in younger patients, structural congenital heart disease, and those with epicardial lead systems. Approaches to pacing system implantation and follow-up in these patients need to be individualized, with special attention to minimizing risk of lead failures. Our findings suggest that expanded utilization of transvenous systems in smaller patients seems justified when anatomy permits.     

Long term management of atrial arrhythmias in young patients with sick sinus syndrome undergoing early operation to correct congenital heart disease.

AIMS: The objective of our study was to evaluate the clinical outcome of patients with operated congenital heart disease (CHD), post-operative sinus node dysfunction and atrial tachyarrhythmias (AT) who had a new generation of DDDRP pacemakers (Model AT501, Medtronic Inc., MN, USA) able to deliver preventive atrial pacing and antitachycardia pacing (ATP) therapies. METHODS AND RESULTS: Fifteen CHD patients (mean age 17+/-9 years, eight after Mustard operation, five after extracardiac Fontan operation and two after atrial septum repair) received a dual-chamber pacemaker with transvenous (eight patients) or epicardial leads (seven patients). In the year before implantation, all patients had symptomatic AT (palpitations), eight patients required hospitalization and five required electrical cardioversion. Pacing prevention algorithms were enabled in all patients, and ATP therapies in six patients. During a mean follow-up of 30 months (range 24-44), three patients (two Fontan, one Mustard) died of CHF, whereas AT required hospitalization in three patients (two Fontan, one atrial septum repair). Only seven patients had symptomatic AT. One hundred and twenty-five AT episodes were treated by ATP in three patients, with an overall termination efficacy of 43.2%. In one patient, atrial lead noise induced inappropriate AT detection that resulted in ATP delivery. Several AT episodes were not treated owing to their very short duration, atrial undersensing, or 1:1 atrioventricular conduction. CONCLUSIONS: Our experience with antitachycardia pacemakers in CHD patients with post-operative sick sinus syndrome after biventricular correction or palliation shows that these devices are safe and that atrial pacing may play a role in AT prevention and treatment.     

An alternate technique to pacing in complex congenital heart disease: assessment of the left thoracotomy approach

BACKGROUND: Pacing in children with congenital heart disease often requires alternate approaches to standard transvenous pacing. The surgical approach used to implant the pacemaker leads has been shown to impact lead survival. There is a paucity of pediatric literature describing the experience using a left thoracotomy approach. OBJECTIVES: To report on short- and mid-term experiences with pacemaker implant via the left thoracotomy approach in children with complex congenital heart disease. METHODS and RESULTS: Data were abstracted retrospectively from patients' hospital charts. To date, the left thoracotomy technique has been used in 11 patients with complex heart disease, with a median of three prior cardiac operations. The median patient age was five years (range of two months to 23 years of age). The pacing indications were acquired postoperative atrioventricular block (n=5), sinus node dysfunction (n=5) and long QT syndrome (n=1). There were no intraoperative complications or long-term complications from this approach. The pacing thresholds at implant and follow-up were acceptable in all patients. One patient died in follow-up for reasons unrelated to the pacemaker or arrhythmia. CONCLUSIONS: The placement of epicardial pacemaker leads via the left thoracotomy approach is a safe and effective alternative to transvenous pacing in pediatric patients with complex congenital heart disease.     

Optimal lead positioning for postoperative atrial pacing.

Temporary atrial pacing leads have uncontested utility for diagnosis and treatment of postoperative supraventricular arrhythmias. Sensing and capture thresholds may be inconsistent, however. We evaluated intraoperative atrial sensing amplitude and capture thresholds in 25 patients after coronary bypass using six bipolar and four unipolar lead combinations based on four lead positions: A, atrial appendage; B, 1 cm above the presumed sinoatrial node at the atrial-superior-vena caval junction; C, interatrial groove at the right superior pulmonary vein; and D, caudal inferolateral free wall. Unipolar lead B and bipolar lead B-D had the best voltage pacing threshold and system resistance (p less than 0.05). The lowest current was also observed with unipolar lead B and bipolar lead B-D, but the difference was not significant (p greater than 0.05). P-wave amplitude was not significantly different for any lead combination. Location C, in unipolar or bipolar combinations, frequently paced the phrenic nerve. These data provide new guidelines for establishment of postoperative temporary atrial pacing leads.     

Automatic measurement of atrial pacing thresholds in dual-chamber pacemakers: Clinical experience with atrial capture management

BACKGROUND: The Medtronic EnPulse pacemaker incorporates the new atrial capture management (ACM) algorithm to automatically measure atrial capture thresholds and subsequently manage atrial pacing outputs. OBJECTIVES: The purpose of this study was to evaluate the clinical performance of ACM. METHODS: Two hundred patients with an indication for a dual-chamber pacemaker underwent implantation. ACM thresholds and manually measured atrial pacing thresholds were assessed at follow-up visits. Clinical equivalence was defined as the ACM-measured threshold being within -0.25 V to +0.5 V of the manually measured threshold. The clinician analyzed all ACM measurements performed in-office for evidence of proarrhythmia. RESULTS: All 200 implanted patients had a 1-month visit, and validated manual and in-office ACM threshold data were available for 123 patients. The ACM threshold was 0.595 +/- 0.252 V, and the manual threshold was 0.584 +/- 0.233 V. The mean difference was 0.010 V with a 95% confidence interval of (-0.001, 0.021). The mean difference over all visits was 0.011 V. For all patients, the individual threshold differences were within the range of clinical equivalence at all visits. No atrial arrhythmias were observed during 892 ACM tests in 193 patients. CONCLUSION: This study demonstrated that the ACM algorithm is safe, accurate, and reliable over time. ACM was demonstrated to be clinically equivalent to the manual atrial threshold test in all patients at 1 month and over the entire follow-up period of up to 6 months. ACM ensures atrial capture, may save time during follow-up, and can be used to manage atrial pacing outputs.     

起搏器植入晚期可逆性阈值升高原因分析及对策

目的 分析起搏器植入患者中,出现晚期可逆性阈值升高的原因,探求解决方法。方法 回顾性分析在2003 -2012年本院植入起搏器的1 143例患者,对出现晚期可逆性阈值升高的7例患者的疾病特点进行总结 。结果 7例患者中,4例出现黑矇或短暂意识丧失,心电图存在失夺获表现;1例心房起搏失夺获,但心室起搏功能良好,无临床症状;2例因安装有具有阈值自动管理功能起搏器,无临床症状。7例的心房基线阈值为0.5 - 0.75 V,心室基线阈值为0. 5 -0.75 V,并发急性病情时,6例心室阈值均超过2.5 V,1例心房阈值超过2.5V。7例患者都有不同的急症,包括大面积烧伤、慢性肾功能不全急性加重、心功能衰竭并呼吸衰竭,导致了酸中毒、高钾血症、心肌缺血缺氧。在急症缓解后,7例心房、心室阈值出现下降,心房阈值降为0. 5 -1. 0 V,心室阈值降为0. 5 - 1. 5 V,起搏器在原有参数设置下工作恢复了正常。 结论 心功能不全、呼吸衰竭、肾功能不全等疾病可引起心肌外环境异常,导致晚期起搏阈值突然升高,具有阈值自动管理功能的起搏器可适时调节起搏阈值。     

Implantable cardioverter defibrillator lead complications and laser extraction in children and young adults with congenital heart disease: implications for implantation and management

INTRODUCTION: Implantable cardioverter defibrillators (ICDs) are being implanted for primary and secondary prevention of sudden death in children and young adults with congenital heart disease. Over time, ICD leads adhere to venous endothelium and endocardium. Lead removal, when necessary, often requires disruption of this fibrous tissue. METHODS AND RESULTS: We retrospectively reviewed and analyzed our experience with ICD lead extraction in children and young adults with congenital heart disease. From April 1999 through January 2002, 14 patients underwent 15 lead extraction procedures to remove 21 leads (17 ICD leads and 4 pacing or sensing leads). Seven patients had surgically corrected structural heart disease (5 transposition of the great arteries with atrial switch repair and 2 corrected tetralogy of Fallot). Mean patient age at extraction was 17.9 +/- 5.7 years (range 9-32), and mean duration of lead implantation was 42.0 +/- 18.9 months (range 15-75). Fourteen of 15 procedures were performed for lead fracture or failure. A laser sheath was used for 20 of 21 lead extractions. Twenty of 21 leads (95%) were completely extracted. There were three instances of blood loss requiring transfusion. There were no major complications or deaths. CONCLUSION: Young congenital heart disease patients with an ICD are at risk for growth-related lead distortion. The use of a laser sheath is safe and effective for ICD lead extraction in congenital heart disease patients, despite coil adherence and altered anatomy. It may be advisable to avoid dual-coil leads in patients with the potential for future growth.     

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.     

激素释放心房电极的临床应用评价

对１１９例应用激素释放电极及９６例应用非激素释放电极患者在心房电极植入后即刻及术后１，３，６，１２，１８个月分别测试心房起搏阈值，并进行比较。发现激素释放心房电极的心房起搏阈值均显著低于非激素释放电极，且无非激素释放电极的早期阈值升高现象。植入激素释放心房电极９５％的患者在术后第３个月心房起搏阈值≤１．３Ｖ；植入非激素释放电极的患者心房起搏阈值≤１．３Ｖ者仅占１５％。表明激素释放心房电极明显优于非激素释放电极，即使进行长期低能量起搏前者亦非常安全，故能降低起搏器电池消耗和延长其寿命。     

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。     

Feasibility of dual-chamber (DDD) pacing via a single-pass (VDD) pacing lead employing a floating atrial ring (dipole): case series, future considerations, and refinements

The objective of this study was to assess the feasibility of DDD pacing from a standard single-pass VDD pacemaker system. Over the past 2 decades significant advances have been made in the development of single-pass VDD pacing systems. These have been shown in long-term prospective studies to effectively preserve atrioventricular (AV)synchrony in patients with AV block and normal sinus node function. What remains problematic is the development of a single-pass pacing system capable of DDD pacing. Such a lead configuration would be useful in those patients with peripheral venous anomalies and in younger patients with congenital anomalies, which may require lead revisions in the future. In addition, with the increased use of resynchronization (biventricular pacing) therapy, the availability of a reliable single-pass lead will minimize operative time, enhance patient safety, and minimize the amount of hardware within the heart. The feasibility of DDD pacing via a Medtronic Capsure VDD-2 (Model #5038) pacing lead was evaluated. Twenty patients who presented with AV block and normal sinus node function were recruited for this study. Atrial pacing thresholds and sensitivities were assessed intraoperatively in the supine position with various respiratory maneuvers. Five patients who agreed to participate in long-term follow-up received a dual-chamber generator and were evaluated periodically over a 12-month period. Mean atrial sensitivity was 2.35 +/- 0.83 mV at the time of implantation. Effective atrial stimulation was possible in all patients at the time of implantation (mean stimulation threshold 3.08 +/- 1.04 V at 0.5 ms [bipolar], 3.34 +/- 0.95 V at 0.5 ms [unipolar]). Five of the 20 patients received a Kappa KDR701 generator, and atrial electrical properties were followed up over a 1-year period. There was no significant change in atrial pacing threshold or incidence of phrenic nerve stimulation over the 1-year follow-up. A standard single-pass VDD pacing lead system was capable of DDD pacing intraoperatively and during long-term follow-up. Despite higher than usual thresholds via the atrial dipole, pacemaker telemetry revealed < 10% use of atrial pacing dipole over a 12-month period, which would minimally deplete the pacemaker's battery. In addition, the telemetry confirmed appropriate sensing and pacing of the atrial dipole throughout the study period. At this time such systems can serve as back-up DDD pacing systems with further refinements required to optimize atrial thresholds in all patients.