冠状窦电极的临床应用研究

目的　评价 sp2 188电极及普通心室电极经冠状窦行左心房起搏的可行性和安全性。方法　 16例患者 ,其中 9例选用 sp2 188电极 ,7例选用普通心室电极。所有患者均行左锁骨下静脉穿刺 ,X线采用正位或左前斜位植入冠状窦电极 ,寻找最佳的起搏和感知部位 ,同时高能量也不致心室夺获。结果　 15例患者成功植入于冠状窦中、远端 ,术中起搏参数如下 (单极 ,脉宽 0 .5 4 m s) ,sp2 188电极组 :电压 ( 1.4 5± 1.4 5 ) V,感知 ( 4 .2 6± 0 .77) m V,阻抗 ( 5 0 5 .6±10 8.1) Ω;普通心室电极组 :电压 ( 1.4 3± 0 .91) V,感知 ( 3.93± 1.4 4 ) m V,阻抗 ( 4 6 8.3± 14 5 .1) Ω。两组起搏电压、感知、阻抗差异无显著性 ( P值均 >0 .0 5 )。随访 2～ 32 (平均 15 .0 )月 ,无一例死亡。其中 2例 sp2 188电极者发生脱位及微脱位 ,各有 1例 sp2 188电极者及普通心室电极发生起搏器介导性心动过速。最后一次随访结束 ,两组患者冠状窦电极起搏和感知功能均良好。结论　普通心室电极经冠状窦中、远端行左心房起搏可行、安全 ,且价格便宜 ,适合临床应用。     

Acute changes in pacing threshold and R- or P-wave amplitude during permanent pacemaker implantation

This study examines the changes in pacing threshold and R- or P-wave amplitude during the first 30 minutes after implantation of tined and screw-in leads. The leads examined were those of 1 manufacturer (Medtronic) and consisted of 3 ventricular pacing leads (model numbers 6957 unipolar screw-in [11 patients], 6961 unipolar tined [12 patients] and 6962 bipolar tined [7 patients]) and 1 atrial lead (model number 6957J unipolar screw-in [10 patients]). After optimal lead position was obtained fluoroscopically in the right ventricular apex or right atrium, the pacing threshold and R- or P-wave amplitudes were measured at 5-minute intervals for 30 minutes. The acute ventricular pacing threshold with the screw-in lead was significantly higher than with the tined lead (0.84 +/- 0.17 vs 0.58 +/- 0.15 volts; p less than 0.001). There was a significant (p less than 0.001) acute decrease in the ventricular pacing threshold with both lead types, with the maximum decrease occurring 5 minutes after lead implantation. There was a significant acute increase in R-wave size with the ventricular screw-in lead that peaked 20 minutes after lead implantation (11.9 +/- 3.0 to 14.7 +/- 4.1 mV; p less than 0.001). The atrial screw-in lead behaved in a manner identical to its counterpart in the ventricle. In conclusion, there are acute changes in the pacing threshold and R- or P-wave amplitude obtained with tined and screw-in pacing leads.(ABSTRACT TRUNCATED AT 250 WORDS)     

三种永久起搏电极慢性阈值的比较

为比较激素电极、靶头电极和螺旋电极的慢性阈值,并探讨其优缺点,对激素电极(26条)、靶头电极(14条)和螺旋电极(20条)的慢性阈值进行了观察。60条电极与单腔或双腔起搏器均系同一公司生产。为提高可比性,仅有5.0 V 电压输出的起搏器不作观察对象。激素电极、非激素电极分别随访18(3～60)和64(3～122)月。结果显示2.5 V 时激素电极的慢性脉宽阈值(0.07±0.03 ms)低于靶头电极(0.11±0.05 ms),后者又低于螺旋电极(0.25±0.13 ms),P 均<0.01。全部病例心房和心室感知均良好。电压输出均采用2.5 V,激素电极、靶头电极和螺旋电极起搏分别置脉宽输出于0.2,0.4和0.8 ms,则80%以上(分别为85%、86%及80%)的病例可达到能量阈值的3倍以上的安全范围。激素电极中有19条可置于1.6 V 和0.3 ms 起搏,其耗能仅为5.0V和0.5 ms(25μJ)的6.1%。即每个脉冲可节能93.9%,从而可延长起搏器的工作寿命。     

激素释放电极双心腔起搏长期阈值观察

目的：观察激素释放电极对心房和心室起搏阈值长期的影响，检验激素释放电极能否用来长期低能量安全的进行双心腔起搏。方法：８１例患者，男４５例，女３６例，平均年龄６７岁。所有患者应用双心腔频率反应起搏器（ＤＤＤＲ）。心房和心室电极分别采用ＭＥＤＴＲＯＮＩＣ５５２４Ｍ及５０２４Ｍ激素释放电极。心房和心室电极植入后即刻及术后１个月、３个月、６个月、１２个月、１８个月及２４个月分别测试双极心房和心室起搏阈值。结果：心房和心室激素释放电极在随访２４个月期间所有测试的心房和心室起搏阈值保持低水平，呈稳定的平台型，无以往非激素释放电极植入早期的起搏阈值明显升高现象。另外，应用激素释放电极的患者中有９８％的心房起搏阈值及９４％的心室起搏阈值≤１．３Ｖ，因此可安全地以２．５Ｖ的电压进行双心腔起搏。结论：被动固定激素释放电极可保持心房和心室的长期的低起搏阈值状态。使绝大多数应用激素释放电极的患者可长期安全地以２．５Ｖ电压进行双心腔起搏，从而有效地延长双心腔起搏器的使用寿命。     

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.     

主动固定电极在右室流出道间隔部起搏中的应用研究

目的评价主动固定电极在右室流出道间隔部起搏应用中的可行性和稳定性。方法160例起搏适应证患者随机分为两组,每组80例,一组采用主动固定电极行右室流出道间隔部起搏(简称主动固定电极组),另一组应用被动固定电极行右室心尖起搏(简称被动固定电极组),观察电极置入时间和心电图QRS波宽度,电极置入后随访观察起搏阈值、感知、阻抗,电极脱位及相关并发症。结果主动固定电极组的置入时间和X线曝光时间均长于被动固定电极(26.34±6.54minvs20.86±4.32min,16.78±5.38minvs8.67±4.52min;P均<0.01)。主动固定电极组电极置入15min时较置入即刻的起搏阈值明显下降(0.76±0.21mVvs1.12±0.25mV,P<0.01)。主动固定电极组起搏的QRS波时限较被动固定电极组短(0.14±0.04msvs0.16±0.03ms,P<0.01)。术后随访1,3,6个月,两组的起搏阈值、感知、阻抗均无差异,未见电极脱位等并发症。结论主动固定电极在右室流出道间隔部起搏中的应用是可行和稳定的。     

双心室起搏埋藏式心脏转复除颤器的安置

评价一次性置入双心室起搏埋藏式心律转复除颤器 (双腔ICD)的安全性和有效性。5例冠心病冠状动脉搭桥术后的患者 ,伴有严重的慢性充血性心力衰竭和恶性室性心律失常 ,置入双腔ICD。结果 :5例左室电极导管和双腔ICD均一次成功置入 ,左室电极放入冠状静脉的侧后枝 ,急性起搏阈值 0 .8± 0 .6V ,电阻 72 2± 12 8Ω ,R波振幅18.6± 5 .3mV ,电流 1.6± 0 .5mA ,而双心室起搏时其起搏电极参数均优于左室电极 ,除颤阈值≤ 14J。结论 :对伴严重慢性充血性心力衰竭和恶性室性心律失常的患者 ,置入双腔ICD是安全、易行的。     

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。     

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。     

Latest generation of unipolar and bipolar steroid eluting leads: long-term comparison of electrical performance in atrium and ventricles.

One hundred and seventy-three patients, mean age 74 years permanently paced with 123 atrial (53 unipolar, 70 bipolar) and 143 ventricular (73 unipolar, 70 bipolar) pacing leads were included in this study. The pacing leads were recent generation low surface area steroid eluting leads from one manufacturer: leads with silicone and polyurethane insulation were studied, and they were combined with generations of one pacemaker family from the same manufacturer permitting identical measurements to be made over a follow-up of 2 years. Pacing threshold was measured using pulse duration at a fixed voltage of 1.5 V: peak to peak P and R wave amplitude and pacing impedance at 2.5 V and 0.5 ms were all measured using the manufacturer's standard programmer. Although many significant differences, in the parameters measures, existed between atrium and ventricle and unipolar and bipolar configurations, none was felt to be of clinical significance. These data permit the physician to choose the lead type with regard to sensing performance and long-term lead integrity.     

Fractally Coated Myocardial Pacemaker Leads in Children

We report our single centre experience with a new fractally coated myocardial unipolar lead (ELC35UP; Biotronik) in 96 pediatric patients (59% male, 41% female). Congenital heart disease (CHD) was associated in 89%. The age at implantation ranged between 2 days and 19 years, median for children with CHD 7.8 years, without CHD 4.7 years. Twenty percent of the children were younger than one year at implantation. Mean follow-up was 30 months (1–57 months). We compared our findings with a steroid eluting epicardial lead (CapSure EPI 4968; Medtronic) in 46 children with comparable age and sex-distribution. We found a lead survival of 87% after 57 months in the ELC35UP group (steroid lead: 87% after 129 months). Pacing energy thresholds were equal after 12 months (median 3.0 microjoules), but the sensing characteristics of the fractally coated lead was significantly superior to the steroid eluting lead with median R waves of 7.0 mV (steroid lead: 3.5 mV) after 12 months. Children with myocardial scar tissue requiring pacemaker therapy after surgery of CHD showed no differences in sensing and pacing thresholds in comparison to children with congenital rhythm disorders. The fractally coated screw-in lead offers technical advantages concerning the subxiphoidal implantation procedure. Conclusion: Fractally coated ventricular screw-in leads represent a feasible alternative to the common steroid eluting leads– especially in children requiring pacemaker therapy after surgery for CHD.     

双房单室三腔起搏器治疗病窦综合征并快速房性心律失常

观察双心房、单心室三腔起搏器治疗病窦综合征合并阵发性房性快速心律失常患者的疗效。三根电极导线分别置入冠状静脉窦内、右心耳和右室心尖部行三腔起搏。冠状窦电极导线与右心房电极导线通过一个Y型转接器构成心房部分。结果 :10例患者 ,9例经左锁骨下静脉径路置入导线 ,1例因存在残存左上腔静脉 ,从右锁骨下静脉置入。 10例中 9例冠状窦电极导线置于冠状静脉窦中部、1例置于冠状静脉窦远端。冠状窦起搏阈值为 1.0 6±0 .2 0V、起搏阻抗 6 11± 115 .8Ω、P波振幅为 4.0 7± 0 .88mV ;右室电极起搏阈值为 0 .5 3± 0 .12V、起搏阻抗 6 70 .3±191.7Ω、R波振幅为 9.6 6± 1.87mV。随访 5～ 2 4个月有 9例起搏器呈DDD工作方式 ,1例呈AAT工作方式。起搏和感知功能良好。 10例中 8例快速性房性心律失常完全控制 ,2例发作次数减少 ,持续时间明显缩短。无一例出现并发症。结论 :三腔起搏器技术安全、可靠。适合于缓慢型心律失常合并阵发性房性快速性心律失常     

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.     

心房按需起搏的临床应用

AAI起搏是治疗房室传导正常的病态窦房结综合征(SSS)的理想方法,它可保持正常的房室收缩顺序及防止VVI起搏时心房压力上升,对预防心房纤颤(Af)有一定作用。本组17例AAI起搏主要用于房室传导正常的SSS,其中4例合并间断发作的Af,1例合并阵发性室上性心动过速(PSVT)。在随诊观察1～15个月之间,Af未再发作,PSVT也得到控制。本组17例全都采用螺旋形主动电极。我们体会其优点为电极可固定在心房之任何部位,操作简单,不易移位,采用可程控多参数的SSI型起搏器,便于定期进行心房调搏,观察房室传导功能的变化及处理可能发生的感知障碍及输出阻滞。     

起搏器植入术中双极导线单、双极模式参数的比较

目的比较起搏器植入术中双极导线单、双极模式的参数。方法共入选117例患者,术中共植入78根心房双极导线和117根心室双极导线,以Medtronic 5318起搏分析仪测试起搏参数,固定脉宽为0.42 ms。结果术中双极导线单极模式与双极模式的起搏阈值无差异(P均>0.05);双极模式的P/R波振幅高于单极模式(P均<0.01);心房、心室双极模式的阻抗均大于单极模式(P均<0.05)。术后随访无1例有阈值异常增高,导线脱位或断裂发生。结论双极导线单、双极模式的起搏阈值无差异;双极模式的感知优于单极模式,而阻抗较单极模式高。     

Determining the Safety of Radiofrequency Ablation in Cardiovascular Implantable Electronic Devices

Radiofrequency catheter ablation (RFCA) is an effective treatment for arrhythmias. The effects of RFCA on cardiovascular implantable electronic devices (CIED) function have varied. We aim to study the effect of RFCA on device parameters and clinical outcomes in patients with CIED. We conducted a single-center retrospective cohort study between 2011 and 2018. Generator and lead parameters were compared pre- and post-ablation using paired sample t-test. The median follow-up interval for documentation of procedure-related complications and clinical outcomes was 8 weeks. We identified 119 eligible patients; whose mean age was 64.5 ± 11.91 years and 22 (18.4%) were females. Types of CIED include single-chamber implantable cardioverter defibrillators (8.93%), dual-chamber implantable cardioverter defibrillators (41.96%), and either dual-chamber or biventricular pacemakers (44.54%). Arrhythmias for which patients underwent RFCA include atrial fibrillation/atrial tachycardia (15.22%), atrial flutter (38.14%), atrioventricular node reentrant tachycardia (13.56%), and premature ventricular complex or ventricular tachycardia (20.34%). No statistically significant difference was observed in pre- and post-ablation: (1) atrial sensing thresholds, pacing thresholds, lead impedance; (2) right ventricle sensing and pacing thresholds; and (3) left ventricle pacing threshold and impedance. A decrease in right ventricle impedance after ablation (549.77 ± 173 ohm vs 507.40 ± 129.0 ohm, P-value <0.004) was observed. Zero complications or deaths were observed. In this single-center study, RFCA did not significantly impact CIED function and was not associated with short-term complications. However longer follow-up is required to confirm these findings.     

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.     

Recording of Pacing Stimulus Artifacts by Endovascular Defibrillation Lead Systems: Comparison of True and Integrated Bipolar Circuits

Background: The occurrence ICD undersensing of ventricular fibrillation due to the presence of a pacing stimulus artifact (PSA) is in part related to the amplitude of the artifact recorded on the ICD rate sensing circuit. There is little comparative data regarding PSA amplitude recorded by commercial ICD rate-sensing circuits.Purpose: To compare PSA amplitude recorded by commercial endovascular defibrillation leads utilizing integrated or true bipolar sensing circuits.Methods: Nineteen large (60–120 kg) pigs were utilized. Two different commercial endovascular defibrillation leads were evaluated, each with its distal tip located at the right ventricular apex: (1) Medtronic Transvene; and (2) CPI Endotak. Three different rate-sensing circuits were evaluated: (1) Transvene true bipolar (tip-ring); (2) Transvene integrated bipolar (tip-coil); and (3) Endotak integrated bipolar (tip-coil). Using a separate pacing lead located at the left ventricular apex (n = 19 animals) or right ventricular outflow tract (n = 10 animals), pacing was performed at a pulse width of 0.5 milliseconds at outputs of 1.5, 5 and 10 volts. PSA amplitude was recorded at each output by each circuit.Results: During pacing from the left ventricular apex, at each pacing output voltage the PSA amplitude recorded by the true bipolar circuit (0.6 ± 0.1 mV at 1.5 volts, 2.0 ± 0.5 mV at 5 volts, 3.7 ± 0.8 mV at 10 volts) was significantly smaller than recorded by the Transvene integrated circuit (1.4 ± 0.3 mV at 1.5 volts, 3.8 ± 0.7 mV at 5 volts, 4.1 ± 0.8 mV at 10 volts) or the Endotak integrated circuit (1.8 ± 0.4 mV at 1.5 volts, 4.2 ± 1.0 mV at 5 volts, 6.3 ± 1.8 mV at 10 volts). During pacing from the right ventricular outflow tract, at each pacing output voltage the PSA amplitude recorded by the true bipolar circuit (0.7 ± 0.1 mV at 1.5 volts, 1.7 ± 0.4 mV at 5 volts, 4.0 ± 0.7 mV at 10 volts) was significantly smaller than recorded by the Transvene integrated circuit (1.1 ± 0.4 mV at 1.5 volts, 3.9 ± 1.2 mV at 5 volts, 7.5 ± 1.8 mV at 10 volts) or the Endotak integrated circuit (1.6 ± 0.7 mV at 1.5 volts, 4.3 ± 1.7 mV at 5 volts, 7.5 ± 2.6 mV at 10 volts). For both pacing sites, the PSA amplitude recorded by the two integrated circuits was not significantly different.Conclusions: For a given pacing output voltage, PSA amplitude recorded by commercial endovascular rate sensing/defibrillation leads is greater when the sensing circuit is integrated than when it is true bipolar. These data may be helpful in planning ICD implantation in patients with previously implanted permanent pacemakers.     

主动固定螺旋电极植入术中的阈值变化

目的观察主动固定螺旋电极的起搏阈值在起搏器植入术中的变化规律。方法72例共植入74根螺旋电极。电极到位后,分别测试螺旋旋出前后的起搏阈值。结果螺旋旋出前的起搏阈值为0.56±0.30 V,旋出后即刻为0.97±0.49 V,旋出后5,10 min分别为0.46±0.29 V和0.36±0.20 V。与旋出前相比,旋出后即刻的阈值明显增高(P<0.01)。随后阈值逐渐下降,在旋出后5 min可基本恢复至旋出前水平。同时右室不同部位的起搏参数无明显差异。结论主动固定螺旋电极在螺旋旋出前后阈值变化明显,5~10 min后达稳定状态。     

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