epicardial pacing in children 12 years
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12-Year Experience of Bipolar Steroid-Elutingpicardial Pacing Leads in Childrenaren Tomaske, MD, Bart Gerritse, PhD, Leo Kretzers, MS, Rene Pretre, MD,li Dodge-Khatami, MD, PhD, Mariette Rahn, MD, and Urs Bauersfeld, MD
ivision of Pediatric Cardiology, University Children’s Hospital and Division of Congenital Cardiovascular Surgery, University
hildren’s Hospital, Zurich, Switzerland; and Medtronic Bakken Research Center, Maastricht, the Netherlandsl2ffr
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Background. Cardiovascular abnormalities and smallascular size may preclude transvenous pacing and ne-essitate epicardial lead implantation. This study evalu-tes the performance of steroid-eluting, bipolar epicar-ial pacing leads.Methods. We prospectively enrolled 114 children with
39 atrial and ventricular bipolar epicardial leadsMedtronic CapSure 10366 or 4968, Minneapolis, MN),ollowed up to 12.2 years (median, 3.2). Lead data werebtained at implant and at semi-annual visits. Analysisas done for left or right atrial and ventricular leads.Results. Median atrial and ventricular pacing thresh-
lds remained below 1.2 V at 0.5 ms. Thresholds did notiffer between pacing sites: left atrial, 0.82V at 0.5 ms;ight atrial, 0.74 V at 0.5 ms (p � 0.85); and left ventricu-ar, 0.96V at 0.5 ms; right ventricular, 0.94 V at 0.5 ms (p �.65). Sensing demonstrated no difference for atrial leads,t left atrial, 3.4 mV; and right atrial, 2.9 mV (p � 0.12),
ut there was superiority of left over right ventricularhf
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2008 by The Society of Thoracic Surgeonsublished by Elsevier Inc
eads (11.2 vs 7.7 mV, p � 0.002). During follow-up, the39 atrial and ventricular leads experienced 19 (8%) leadailures. Lead survival at 2 and 5 years was 99% and 94%or atrial leads and 96% and 85% for ventricular leads,espectively.
Conclusions. Bipolar steroid-eluting epicardial leadsemonstrate excellent sensing characteristics and persis-
ent low median pacing thresholds below 1.2 V at 0.5 msn children during up to 12 years follow-up. Consideringrowing and active patients with most having congenitaleart disease, the lead survival of 85% to 94% at 5 years
s favorable. Subanalysis shows superior sensing for leftentricular leads. Bipolar steroid-eluting leads providen alternative approach for permanent pacing and maylso be considered for left atrial and ventricular pacing,esynchronization, or defibrillator therapy.
(Ann Thorac Surg 2008;85:1704–11)
© 2008 by The Society of Thoracic Surgeonsdvances in lead and device technology allow pace-maker system implantation in infants and even in
eonates [1, 2]. Besides bradycardia pacing for sinusode disease or heart block, resynchronization therapynd implantation of cardioverter defibrillators (ICD)re progressively more often required in pediatricatients and adults with congenital heart disease
CHD) [3].Specific problems in children or adults with complex
HD can complicate pacemaker therapy. Small vesselize, cardiovascular abnormalities, or the intention toreserve the venous access often preclude a transvenouspproach and require epicardial pacing [4, 5]. Moreover,hysical activity and somatic growth may affect lead
ongevity in young patients [5–7].Studies in the pediatric population have indicated
uperior longevity of transvenous over unipolar screw-inpicardial leads, mainly due to high thresholds, exitlocks, and fractures of epicardial leads [8]. Initial expe-iences with bipolar steroid-eluting epicardial leads
ccepted for publication Feb 6, 2008.
ddress correspondence to Dr Tomaske, Division of Pediatric Cardiology,
ave shown low pacing thresholds up to 18 months ofollow-up [9].
A main disadvantage of transvenous leads is attribut-ble to right ventricular (RV) pacing leading to impairedeft ventricular (LV) systolic function over time [10]. Thedvantage of epicardial leads facilitating LV pacing andensing has promoted further epicardial lead implanta-ion for single-site LV pacing, resynchronization therapy,CD therapy, or patients with a diseased RV [3]. The aimf this study was to evaluate pacing and sensing charac-eristics, and survival of bipolar steroid-eluting epicardialacing leads in pediatric patients.
atients and Methods
tudy Patients and Leadsll children who received permanent pacing systems
onsisting of bipolar steroid-eluting epicardial leadsMedtronic CapSure Epi 10366 or 4968, Medtronic, Inc,
Dr Bauersfeld, Dr Gerritse, and Mr Kretzers disclosethat they have a financial relationship with Medtronic
Inc.0003-4975/08/$34.00doi:10.1016/j.athoracsur.2008.02.016
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1705Ann Thorac Surg TOMASKE ET AL2008;85:1704–11 BIPOLAR EPICARDIAL LEADS IN CHILDREN
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inneapolis, MN) between 1994 and 2006 were prospec-ively enrolled into the study. The study populationomprised 114 patients with a maximum follow-up of2.2 years. A total of 107 atrial and 132 ventricular pacingeads were implanted, including lead replacements oriventricular pacing in some patients. The choice forpicardial pacing systems was determined by patientize, cardiovascular abnormality, indication for pacing,nd patient preference. Leads were connected to variousingle- and dual-chamber devices, biventricular devices,r ICDs. The study excluded 5 children: 3 died in-hospitalue to a non-pacing-related cause and 2 children with
eads not connected to a device.The bipolar steroid-eluting epicardial leads have
latinized, porous electrode surfaces with a surfacerea of 14 mm2 (anode) and 6 mm2 (cathode). Theyontain 1.0 mg or less of dexamethasone sodium phos-hate. This study protocol was performed with institu-
ional Ethical Committee approval and written informed
able 1. Baseline Characteristics of 114 Children at Firstpicardial Lead Implant
haracteristicsNo (%) or Median
(range)
emographicsatients, No. 114exMale 70Female 44ge, years 6.2 (0.0–18.5)eight, kg 18.0 (1.0–88.0)edian follow-up, years 3.2 (0.1–12.2)ardiac anatomyStructurally normal heart 36 (32)AVSD 10 (9)VSD 14 (12)D-transposition great arteries and VSD 7 (6)L-transposition of great arteries 4 (4)Complex single ventricle 25 (22)Other 18 (16)
rior/concomitant cardiac operation 74 (65)ndication for pacing
Post-op AV block 39 (34)Congenital AV block 22 (19)Acquired AV block 9 (8)Post-op sinus node disease 6 (5)Congenital sinus node disease 24 (21)Resynchronization therapy 6 (5)ICD therapy 8 (7)
urgical access, n(%)Left lateral thoracotomy 65 (57)Right lateral thoracotomy 1 (1)Midline sternotomy 37 (32)Subxiphoid 11 (10)
V � atrioventricular; AVSD � atrioventricular septal defect; ICD �mplantable cardioverter device; VSD � ventricular septal defect.
onsent.
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1706 TOMASKE ET AL Ann Thorac SurgBIPOLAR EPICARDIAL LEADS IN CHILDREN 2008;85:1704–11
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mplant Data, Pacemaker Telemetry Data, and Leadailuresor all leads, impedances, P- or R-wave amplitudes, asell as pacing voltage and energy thresholds were ob-
ained at implant, at discharge, and regular follow-upisits. The first follow-up after discharge was within 4 to 6eeks. Further follow-up was scheduled 3 months after
mplant and every 6 months thereafter. Pacing voltage andnergy of lead thresholds were calculated for a standardalue of 0.5-ms pulse duration (V at 0.5 ms and �J at 0.5 ms)o allow for comparison by using the energy formulaublished previously [11]. In those patients in whom im-edance measurements were unipolar, the difference be-
ween unipolar and bipolar measurements was noted oncend added to the unipolar measurements during follow-up.
Lead events were grouped in two categories:
. lead failure, which was defined as lead fracture,insulation defect, replacement due to unacceptablyhigh thresholds or sensing abnormalities, loss of cap-ture, lead dislodgement, or primary infection; and
. secondary lead replacement, which was defined asevents of secondary infection if leads were exposedto pocket infection, accidental lead damage at car-diopulmonary bypass surgery, or elective lead re-placement at the time of device exchange.
Lead lifetime was defined as time elapsed from leadmplant to the event of lead failure. From the date ofxchange, new leads were enrolled as new implants withead measurements starting at implant.
Performances of left (LA) and right atrial (RA) and LVnd RV pacing leads, as well as the effect of prior cardiacperation, were also analyzed and compared.
urgical Techniqueccess for lead implantation was either by a subxiphoid
ncision to reach the RV apex or by a left lateral thoracot-my to reach the LV free wall and corresponding atria, asescribed previously [12]. In those children with concomi-
ant cardiac procedures, the epicardial leads were im-lanted through a midline sternotomy at the time of cardiacperation, with preference of an LV implant site.Standard surgical implant techniques were used with
onabsorbable sutures. For the distal and proximal suturef the triangular electrode, a single-knot technique was
able 3. Spearman Correlation for Individual Regressionlopes of Measured Telemetry Data and Lead Age
Pairs, No. Correlation (�) p Value
-wave 46 �0.049 0.75a
trial threshold 49 �0.001 0.99a
trial impedance 49 �0.141 0.34a
-wave 63 �0.088 0.49a
entricular threshold 70 �0.184 0.1a
entricular impedance 70 �0.096 0.43a
Not significant.
sed. Sutures were placed perpendicularly to the epicar- T
ium to avoid tissue trauma near the electrode. The deviceas implanted in the abdominal rectus sheath in 46 pa-
ients, in a left thoracic muscular pocket in 66, or subpec-orally in 2.
tatistical Analysisfollow-up period of 8 years was statistically analyzed.
ata are presented as median and interquartile (IQR)
ig 1. Subanalysis of 25 ventricular pacing leads with a lead agelder than 5 years. Box and whisker plots of individual regressionlopes demonstrated a slight incline of ventricular pacing voltagehresholds (A) for measurements beyond 5 years (median, �0.017 vs.052, p � 0.131). Measurements of ventricular impedances (B) sig-ificantly declined beyond 5 years (median, 5.53 vs �11.20, p �.003). The asterisk (*) denotes significance. The horizontal line inhe middle of each box indicates the median; the top and bottomorders of the box mark the 75th and 25th interquartile, respectively.
he whiskers mark is 97.5th and 2.5th percentile.
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1707Ann Thorac Surg TOMASKE ET AL2008;85:1704–11 BIPOLAR EPICARDIAL LEADS IN CHILDREN
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ange. A value of p � 0.05 was considered statisticallyignificant.
Survival is reported with Kaplan-Meier estimates and5% confidence intervals (CI) and compared with aog-rank test. Electrical measurements were comparedsing linear regression models, with parameter estima-
ion, corrected for multiple observations per patient,sing generalized estimating equations. To determine
ndividual change, regression slope coefficients over in-ividual repeated measurements were calculated forach patient’s course. Changes per year were calculatedor each electrical parameter. To focus on the long-termhanges, data collection for calculating regression slopeoefficients was started 6 months after implant, with ainimum of 5 contributing measurements.
Correlations between variables were measured by thepearman correlation. Mann-Whitney U tests were used fornalyzing differences in continuous variables between in-ependent groups. The Wilcoxon signed rank test was used
or within-group changes of continuous variables betweenifferent time periods. The �2 test provided a comparison of
he pacing site as well as the effect of cardiac operation. Alltatistical analyses were performed using SAS 9.1 softwareSAS Institute Inc, Cary, NC).
esults
atient Dataemographic and surgical data as well as clinical char-
cteristics at implantation are reported in Table 1. In 65%f the children, pacemaker system implantation was
Fig 2. (A) Atrial and (B) ventricular pacingvoltage thresholds at 0.5-ms pulse durationover time. No differences were found for me-dian pacing voltages for (A) the right atrial(RA, diamonds) or left atrial (LA, squares)leads (LA, 0.82 V at 0.5 ms vs RA, 0.74 V at0.5 ms; p � 0.85, or for the (B) right ventric-ular (RV, diamonds) or left ventricular (LV,squares) leads (LV, 0.96 V at 0.5 ms vs RV,0.94 V at 0.5 ms; p � 0.65).
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1708 TOMASKE ET AL Ann Thorac SurgBIPOLAR EPICARDIAL LEADS IN CHILDREN 2008;85:1704–11
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elated to CHD with prior or concomitant cardiac oper-tion. Six children were lost to follow-up at a median of.5 years. No deaths related to the pacemaker systemccurred. Kaplan-Meier estimates of patient survival at 2,, and 10 years after enrolment were 98% (95% CI, 95% to00%), 95% (95% CI, 90% to 100%), and 95% (95% CI, 83%o 100%), respectively.
ead Follow-Up and Performanceollow-up consisted of 1251 visits contributing to atrialeasurements and 1677 to ventricular lead measure-ents. Median follow-up time was 2.6 years (range, 0.1 to
1.7 years) for atrial leads and 2.8 years (range, 0.1 to 12.2ears) for ventricular leads. Lead characteristics are givenn detail up to 10 years (Table 2). Median pacing voltagehresholds for atrial and ventricular leads remained be-ow 1.2 V at 0.5 ms during the entire observation period.
edian individual regression slopes indicated stablerends during follow-up for sensing (atrial, 0.000 [p �.88]; ventricular, 0.000 [p � 0.22]), pacing thresholdsatrial, 0.000 [p � 0.98], ventricular, 0.022 [p � 0.98]), andmpedances (atrial, 8.135 [p � 0.39]; ventricular, 0.625p � 0.13]). Neither of the individual regression slopes for
easured electrical parameters correlated with lead aget study closure (Table 3).A separate analysis of individual regression slopes was
one for 13 atrial leads and 25 ventricular leads with aead age older than 5 years (median, 9.4 years; range, 6.1o 12.2 years). Comparison of individual regression slopesefore and after a lead age of 5 years revealed no significantifferences for atrial leads. For ventricular leads, a signifi-ant decline of impedances as well as a slight but notignificant incline of pacing voltage thresholds was ob-erved for measurements beyond 5 years (Fig 1).
Analysis of lead performances between right or left
able 4. Lead Failures and Secondary Lead Replacements Du
utcome Tota
ollow-up, median (range) yearsead positionAtrial leads 107Ventricular leads 132trial lead failure, No. (%) 5 (5)High thresholdLead fractureInsulation defect
entricular lead failure, No. (%) 14 (11High thresholdLoss of captureLead fractureInsulation defectLead dislodgement
econdary lead replacement, No. (%) 5 (4)Secondary infectionAccidental lead damageRoutine lead replacement
trial and ventricular implant sites demonstrated no s
ifference between pacing voltage thresholds over timeFig 2A, B). Moreover, no difference was seen in median-wave amplitudes (LA, 3.4 mV vs RA, 2.9 mV; p � 0.12).owever, a significantly superior course of ventricular
ensing was seen for LV compared with RV leads (LV,1.2 mV vs RV, 7.7 mV; p � 0.002).
Analysis of the effect of prior or no cardiac operationevealed no difference for atrial (0.87 vs 0.67 V at 0.5 ms; p �.56) or ventricular pacing thresholds (1.01 vs 0.83 V at 0.5s; p � 0.21). No difference of prior or no cardiac operationas observed for P-wave (3.0 vs 3.3 mV; p � 0.31) or R-wave
mplitudes (10.7 vs 9.0 mV; p � 0.57), respectively. More-ver, no significant differences for lead impedances oracing energy thresholds were observed for the pacing sitesnd children with prior or no cardiac operation.
ead Failuresuring follow-up, 239 atrial and ventricular leads expe-
ienced 19 lead failures (8%). Characteristics of observedead failures and secondary lead replacements are re-orted in Table 4.At 2 and 5 years after implantation, the estimated
reedom from lead failure was 99% (95% CI, 97% to 100%)nd 94% (95% CI, 85% to 100%) for atrial leads, respec-ively; and was 96% (95% CI, 92% to 100%) and 85% (95%I, 76% to 94%), respectively, for ventricular leads. Fur-
hermore, estimated lead survival was compared by sites,nd no statistical significance was found between left andight implant sites (Fig 3A, B).
omment
ead Performance and Survivalecent advances in pacing lead technology, such as thin
Follow-up, Categorized for Lead Position
Right-sided Left-sided
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1709Ann Thorac Surg TOMASKE ET AL2008;85:1704–11 BIPOLAR EPICARDIAL LEADS IN CHILDREN
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ven in neonates and infants, thus maintaining the con-roversy about the use of transvenous or epicardial pac-ng leads [13].
The main concerns for transvenous RV pacing leads inhildren are venous obstructions [13], lead failures due toomatic growth [5], lead infections [14], and the risk ofaradoxic embolism in the presence of residual intracar-iac defects [15]. Major drawbacks of older epicardialacing leads have been the occurrence of lead fractures
16], increasing pacing thresholds over time [8, 16], andigh pacing thresholds in children with prior cardiacperation [17]. The invention of steroid-eluting electrodeurfaces combined with suture-on electrode tip designs
as improved the epicardial lead performance [18, 19]. fowever, the potential advantage of the epicardial pac-ng system has yet to be demonstrated by prolongedxperiences.The present study enrolled 114 children after implan-
ation of 107 atrial and 132 ventricular bipolar steroid-luting epicardial pacing leads. Stable chronic atrial andentricular sensing as well as pacing thresholds werechieved over a maximum follow-up of 12.2 years. Per-istent low thresholds of steroid-eluting leads have beenemonstrated for up to 6 years for unipolar epicardial
eads [19, 20] and up to 7 years for transvenous leads [5,]. Similar to previous results of unipolar epicardial leads19, 20], low median pacing thresholds of 1.2 V at 0.5 ms
Fig 3. Kaplan-Meier estimates for lead sur-vival of (A) 107 atrial and (B) 132 ventricularleads. (A) No difference was found betweenatrial pacing sites (p � 0.37). At 2 and 5years, lead survival for right atrial (RA,dashed line) leads was 97% (95% confidence[CI], 90% to 100%) and 91% (95% CI, 75%to 100%), respectively; for left atrial (LA,solid line) leads it was 100% (95% CI, 100%to 100%) and 94% (95% CI, 83% to 100%),respectively. (B) No difference was found be-tween ventricular pacing sites (p � 0.92). At 2and 5 years, lead survival for right ventricle(RV, dotted line) leads was 100% (95% CI,100% to 100%) and 84% (95% CI, 66% to99%), respectively; for left ventricle (LV, solidline) leads it was 93% (95% CI, 85% to100%) and 86% (95% CI, 75% to 97%),respectively.
or atrial as well as ventricular leads were observed
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1710 TOMASKE ET AL Ann Thorac SurgBIPOLAR EPICARDIAL LEADS IN CHILDREN 2008;85:1704–11
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uring follow-up in our study cohort, independently ofhe implant site. Recently, long-term pacing thresholdsf transvenous leads in children have been reported toe slightly superior, ranging from 0.6 to 0.9 V at 0.5 ms
7, 8]. However, the number of children with priorardiac operation and thereby higher risk for a dis-ased myocardium was smaller compared with ourtudy cohort.
Epicardial lead failures occurred in 8% of the leads,ith lead fractures and high thresholds being the most
ommon complication. These findings are in line withesults of recent studies reporting predominantly su-ured-on epicardial leads [7, 19]. Comparably, the inci-ence of lead failures of modern transvenous leads inhildren is reported to be about 7% [7, 8]. The estimated-year lead survival seen in our cohort was 94% for atrialnd 85% for ventricular pacing leads, independently ofhe implant site. These encouraging results of improvedead longevity confirm previous published data reportingf an estimated 5-year survival of 71% to 85% for epicar-ial leads [6, 7, 18]. Moreover, they are comparable with
he survival of transvenous leads, with a reported esti-ated 5-year survival rate of 84% to 89% [6, 7].Our favorable results of consistently low sensing and
acing thresholds, and improved lead longevity, werebserved in a study designed with uniform use of a singleechnology and single manufacturer of epicardial pacingeads, followed up in a relatively large population of 114hildren. Studies in children with permanent pacingsually have a small sample size. Previous reports of
ong-term experiences with epicardial lead thresholdsnd performance in large pediatric cohorts bear theimitation of showing performances of a variety of man-facturers, models, and technologies [5–8, 16]. The cur-ent study indicates improved long-term lead perfor-
ance of bipolar steroid-eluting epicardial leads.specially when connected to threshold tracking devices,
ow pacing thresholds will allow low energy pacing,esulting in a marked battery service life extension [21].
teroid Elutionteroid elution helps to diminish the initial inflammationfter lead implant; however, a secondary intention is itsffect on reducing stimulation thresholds over time. Theuestion of how long steroid-eluting electrodes are capa-le of maintaining their steroid-eluting effect to prevent
nflammation and fibrosis at the electrode-tissue inter-ace is not satisfactorily answered. An experimental study22] analyzed the remaining steroid in 25 transvenousxplanted leads and demonstrated that 20% of the steroidas still present at 10 years. Remarkably, individual
egression slopes indicated stable trends for telemetryata during the whole observation period and did notorrelate with lead age. A separate analysis of those leadslder than 5 years revealed stable lead performances fortrial leads and a slight incline for ventricular pacingoltages for measurements beyond a lead age of 5 years.evertheless, there was a significant decline of ventric-lar impedances measured beyond 5 years. A fast con-
ucting interface between the electrode and epicardial rurface due to a decrease of the steroid-eluting potencyf the electrode, such as local edema or a deterioration ofhe lead insulation, could be a possible cause for thebserved lower ventricular impedances over time. How-ver, the restricted number of patients with a lead agelder than 5 years limits the statistical validity of aonclusive statement.
ead Implant Sitelinical trials with permanent RV apex pacing haveemonstrated asynchronous ventricular activation, lead-
ng to LV dysfunction over time [10]. Alternate pacingites have been intensively studied, indicating a superiorV systolic function in children paced from the LV apex
23, 24]. The potential prevention of myocardial deterio-ation has led to a favored LV approach for lead place-ent in our study cohort. An important finding was a
uperior performance of ventricular sensing was seen forV leads in our study cohort, whereas atrial sensing asell as atrial and ventricular pacing thresholds were
ndependent of the implant site. Moreover, sensing andacing characteristics of the epicardial leads were inde-endent of prior cardiac operation.
otential Clinical Implicationshe LV systolic function is less adversely affected fromV pacing. Because epicardial pacing of the LV seems
easible and safe, it could be the preferred approach forentricular pacing lead insertions. Furthermore, resyn-hronization therapy could be achieved by means ofpicardial LV instead of transvenous pacing by way ofhe coronary sinus [25] in grown-ups with CHD. Inddition to the favored LV position of the ventricularead, a LA lead may be preferable after extensive RAurgery such as after Mustard, Fontan, or Ebstein anom-ly surgery. Even though epicardial pacing lead place-ent inevitably involves a thoracotomy, LV pacing can
asily be achieved by a minithoracotomy. A muscle-paring minileft axillary approach is used in our insti-ution, as published recently [12]. This technique wasssociated with a low complication rate and providesxcellent cosmetic and functional results. Moreover,ith the superior course for LV sensing, epicardial
eads can safely be used in patients with ICD systemsonnected to epicardial sensing and pacing leads, andsubpleural defibrillation electrode [26].
tudy Limitationsmain limitation of this study is the use of different
evices. In the clinical setting, we observed slightlyifferent threshold measurements between the devices.n addition, the variable of R-wave measurementshanged over time. The new generations of devices doot offer the possibility to accurately determine R-waveensing above 12.5 mV. This circumstance could, poten-ially, even have led to an underestimation of the supe-
iority of R-wave sensing of LV leads.
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