Europace Advance Access originally published online on March 3, 2008
Europace 2008 10(7):838-843; doi:10.1093/europace/eun038
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Pacing
The efficacy of ventricular pacing with device automaticity in paediatric patients
1 Division of Paediatric Cardiology, University Children’s Hospital, Steinwiesstrasse 75, 8032 Zurich, Switzerland; 2 Biostatistic Unit, University Zurich, Zurich, Switzerland
Manuscript submitted 12 October 2007. Accepted after revision 3 February 2008.
* Corresponding author. Tel: +41 44 2667519; fax: +41 44 2667981. E-mail address: maren.tomaske{at}kispi.uzh.ch
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Abstract |
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Aims: To compare pacemaker reprogramming and re-intervention rates in children with AutoCapture® (AC) and conventionally (Conv) programmed devices, and to assess reliability of device automaticity.
Methods and results: Data of children with AC (group AC, n = 49) and conventionally programmed devices (group Conv, n = 41) were analysed. A total of 1106 outpatient visits and 147 Holter recordings were screened for device reprogramming and invasive re-intervention. At 2 and 5 years, freedom from reprogramming differed significantly between groups (AC: 63/35% vs. Conv: 13/4%; P < 0.0001), whereas freedom from re-intervention was not different (AC: 95/90% vs. Conv: 95/85%; P = 0.26). Mean yearly rate of reprogramming was lower in group AC (AC: 0.67 ± 0.55 vs. Conv: 1.13 ± 0.82; P = 0.005). Follow-up duration correlated with a decreasing number of reprogramming per year in group Conv (
= –0.73, P < 0.001). No ventricular output reprogramming was required in group AC. Holter recordings required 0.07 ± 0.13 reprogramming per year in group Conv, none in group AC (P < 0.001). Holter-detected lead dysfunction prompted re-intervention in one patient of each group.
Conclusion: Estimated freedom from as well as total yearly rate of device reprogramming was favourable for AC-programmed devices. No difference was seen for the incidence of invasive re-interventions. AC ventricular output control was effective. Structured device follow-up and Holter recordings in specific patient groups remain mandatory for all devices in paediatric patients.
Key Words: Pacing system, Device automaticity, Paediatric patients, Follow-up, Holter recordings
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Introduction |
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Antibradycardia pacing is the most frequent indication for pacing in paediatric patients.1
Conditions with evidence for permanent pacing in the paediatric population are congenital, acquired or post-operative complete atrioventricular block, sinus node dysfunction, and resynchronization therapy.1,2 National guidelines for device follow-up have been provided for the adult population,3–5 recommending a short-term follow-up of 4–6 weeks after pacing system implantation, and a 6–12 monthly follow-up interval thereafter. Objectives of device follow-up are to check achievement of therapeutic aims, technical functions such as sensing and pacing characteristics, lead condition as well as battery status, optimization of device settings, and to exclude complications.6–10 New device generations offer a variety of diagnostic features and automaticity like automatic output adjustment11–14 to monitor and ensure appropriate technical function. However, information is scarce about the reliability, efficacy, and the impact of device automaticity features on follow-up management in children carrying devices with conventional output programming when compared with automatic output adjustment. The purpose of this study was to evaluate device reprogramming and invasive re-intervention of the pacing system in children with either AutoCapture® (AC) or conventionally programmed devices and to assess reliability of device automaticity.
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Methods |
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Study patients and devices
We retrospectively analysed data of 90 children who underwent outpatient follow-up after device implant in our institution between 1996 and 2006. AC-programmed devices were followed in 49 children (group AC), and conventionally programmed devices in 41 children (group Conv). Devices were either connected to steroid-eluting epicardial leads (group AC, n = 46; group Conv, n = 34) or steroid-eluting transvenous leads (group AC, n = 3; group Conv, n = 7). Implanted devices and device positions are depicted in Table 1.
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The main difference between AC and conventional devices is the ongoing automated adjustment of the ventricular stimulation output to the prevailing threshold in the AC devices, whereas atrial output remains programmed with two- to three-fold safety margin. To monitor ventricular capture, two parameters measured during AC device interrogation are crucial for a safe function of the algorithm: a sufficient evoked response signal and a low lead polarization signal. AC devices were implanted when available and if no particular device feature such as ECG storage capabilities, atrial overdrive pacing, or resynchronization were required. AC-controlled pacing was activated after device implant if the evoked response signal and lead polarization signal were sufficient. Conventional programming included atrial and ventricular output adjustment with two- to three-fold safety margin after the acute phase following pacing system implantation.
Patients with <1 year follow-up were excluded from the study. In the presence of an elective device exchange, follow-up was continued. Follow-up was discontinued in those children, in whom devices were reprogrammed from AC to conventional settings (n = 4) or vice versa (n = 3). The study protocol was approved by the Hospital Ethical Committee and written informed consent was obtained.
Data collection
A total of 1106 (group AC, n = 544; group Conv, n = 562) follow-up visits were reviewed from a comprehensive electronic device and Holter database. Impedances, sensing and pacing thresholds, evoked response and lead polarization signals, and detailed device settings were obtained at every outpatient visit. Outpatient follow-up visits were performed after 1, 3, and every 6 months thereafter.
Device reprogramming and invasive re-intervention
All outpatient visits were screened for events necessitating either device reprogramming or invasive re-intervention. Actions were classified into three categories: (i) reprogramming of the atrial or ventricular sensitivity, stimulation output, as well as pacing mode; (ii) reprogramming of AC-specific features such as the evoked response sensitivity and the AC setting; (iii) any event requiring invasive re-intervention of the pacing system. Re-interventions because of scheduled device replacement owing to battery depletion were excluded.
Holter recordings
Holter recordings were routinely performed before discharge and demonstrated an adequate device function in all 90 patients. In addition, Holter recordings were performed during outpatient follow-up as indicated by the underlying heart disease, suspected arrhythmias, or pacing system dysfunction. In those patients with complex congenital heart disease at risk for the development of arrhythmias, Holter recordings were performed at least once every year. During follow-up, a total of 147 (group AC, n = 43; group Conv, n = 104) Holter recordings were performed. Holter recordings were particularly screened for lead over- and undersensing, loss of capture or sustained atrial tachycardia despite antitachycardia devices. Required device reprogramming or invasive re-intervention of the pacing system was classified into the three categories as described above.
Statistical analyses
A follow-up period of 8 years was statistically analysed. Data are presented as mean ± SD, unless specified otherwise. A P-value <0.05 was considered statistically significant.
Estimated freedom from device reprogramming or invasive re-intervention of the pacing system was plotted with Kaplan–Meier analysis, confidence intervals (CI) are presented as 95% CI. Estimated freedom from device reprogramming or invasive re-intervention was compared for statistical significance between independent groups using log rank test. Mann–Whitney U tests were used for analysing differences in continuous parameters between independent groups. Correlations between parameters were measured by Spearman’s correlation. All statistical analyses were performed using the Statistical Package for Social Sciences (SPSS for Windows, Version 14.0.1, Inc., Chicago, IL, USA).
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Results |
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Patients’ demographic data and clinical characteristics at device implant
Demographic data, clinical characteristics, as well as indications for permanent pacing are given in Table 2. Total follow-up did not differ between both groups (P = 0.26), with a maximum follow-up of 11.7 years. There was no mortality attributable to the pacing system. A total of eight patients (group Conv, n = 7; group AC, n = 1) were lost to follow-up because of crossover to an adult cardiologist at a median time interval of 5.4 years.
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Device reprogramming and invasive re-intervention
Freedom from device reprogramming was superior for group AC at 2 and 5 years after device implant (P < 0.001), indicating that in 35% of group AC no reprogramming was required during 5 years of follow-up (Figure 1A). In contrast, freedom from invasive re-intervention of the pacing system at 2 and 5 years after device implant did not differ between both groups (P = 0.26) (Figure 1B).
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AC-specific reprogramming had to be performed in 57 of 544 (10%) visits in group AC, whereas adjustment of ventricular stimulation output was required in 108 of 562 visits in group Conv. Device reprogramming and events leading to invasive re-interventions are depicted in detail in Table 3. The total yearly rate of device reprogramming was lower in group AC than in group Conv (0.67 ± 0.55 vs. 1.13 ± 0.82 per year; P = 0.005) (Figure 2). However, a total of 0.30 ± 0.37 AC-specific reprogramming per year was observed in group AC which was mainly evoked response sensitivity adjustments. Length of follow-up correlated with a decreasing number of yearly device reprogramming in group Conv (P < 0.001), but not in group AC (P = 0.18) (Figure 3A and B). Moreover, length of follow-up correlated with a decreasing number of yearly ventricular output adaptation in group Conv (
= –0.336, P = 0.032).
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No difference was seen for the incidence of invasive re-interventions per year between both groups (group AC, 0.02 ± 0.07; group Conv, 0.07 ± 0.14; P = 0.12). The risk for invasive re-intervention of the pacing system was 1% in group AC and 2% in group Conv, respectively.
Holter recordings
Holter recordings required 0.07 ± 0.13 device reprogramming per year in group Conv, but none in group AC (P < 0.001). Events requiring reprogramming were intermittent P-wave undersensing (n = 3), R-wave oversensing (n = 5), R-wave undersensing (n = 1), ventricular loss of capture (n = 2), and sustained atrial flutter (n = 1). A lead dysfunction detected by Holter recording prompted invasive re-intervention in one patient of each group.
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Discussion |
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Recent developments in device and lead technology have provided features for optimized permanent pacing performance. Hence, quality and reliability of pacing systems have improved.15
An essential aspect of device therapy in the young patient is an adequate and thorough follow-up without affecting the quality of life by a tight schedule. However, guidelines for structured pacemaker follow-up in the paediatric population are missing. Even though some of the general guidelines for permanent pacing could be adapted from the adult population,3–5 there are several particular problems emerging in young patients or those with complex congenital heart disease, especially due to lead fracture or sudden threshold rise. While in the adult population a 6–12 monthly interval is an established long-term follow-up management, follow-up in the paediatric population is scheduled at least every 6 months in the subsequent years after pacing system implantation. An AC device with an automated adjustment to the actual ventricular threshold may be beneficial in the paediatric population. Lead stretch due to somatic growth, a high level of physical activity, and growth-related distortion can result in micro-dislodgement with high threshold fluctuations.16 Moreover, in those patients with congenital heart disease, potential risks for an abnormal ventricular pacing threshold rise are scars and adhesions resulting from prior cardiac surgery,17 a diseased myocardium, cyanosis or even elevated pressure/volume overload of the ventricle. At present, the impact of device automaticity on reliability and follow-up is unknown. Moreover, data about the frequency of annual reprogramming or invasive re-intervention in the young patient are lacking to determine an adequate device follow-up interval with either conventionally or AC-programmed devices.
In this study, we enrolled a total of 90 children with either AC-controlled pacing (n = 49) or conventionally programmed devices (n = 41) with a maximum follow-up of 11.7 years. The main findings are that freedom from device reprogramming at 2 and 5 years was superior in patients with AC-programmed devices primarily because of the absence of ventricular output adjustments and the low rate of necessary evoked response sensitivity reprogramming. The mean yearly rate of device reprogramming was 0.7 vs. 1.1 in children with AC vs. conventionally programmed devices. Interestingly, the length of follow-up correlated with a decreasing number of device reprogramming in children with conventionally but not in those with AC-programmed devices. This reflects the necessary conventional output adjustments in the acute phase after pacing system implantation. Moreover, it might result from the older population represented in the group with conventionally programmed devices, potentially leading to stabilized sensing and pacing thresholds during less somatic growth, or stabilized haemodynamics of the underlying congenital heart disease.
The risk for invasive re-intervention during outpatient visits was up to 2%. Of importance, our results cannot be compared with previous studies6,16 reporting an overall risk for re-intervention up to 8%. Because of the study design with a main focus on outpatient visits, re-interventions for scheduled device exchange owing to battery depletion were excluded from the analysis. Including re-interventions for end of life battery could have caused bias in favour for AC devices, which have proven longer battery service life.18
Probably, because of the improved technical performance of AC devices with incorporated storage of events, routine Holter recordings in children with AC-controlled pacing did not offer additional information. Importantly, AC devices proved to provide safe and reliable pacing in our AC cohort. In contrast, conventionally programmed devices of 12 patients had to be reprogrammed because of interpretation of the Holter recordings. Holter-detected lead dysfunction revealing repeated ventricular loss of capture prompted invasive re-intervention in one patient of each group. Interestingly, both children exhibited only slight symptoms of intermittent dizziness. Thus, besides routine Holter recordings for patients with congenital heart disease and conventionally programmed devices,8 Holter recordings are valuable in those presenting with any change of symptoms or suspected dysfunction of the pacing system.
To enhance the interval of outpatient visits, remote transtelephonic device interrogation is increasingly utilized in the management of adults.19 Even though technology may have improved, in-office device follow-up has been shown to be significantly more effective for the detection of device complications when compared with a transtelephonic interrogation.20 Interestingly, the vast majority of the events leading to reprogramming and re-interventions during follow-up in our cohort were neither detected by the patients themselves nor their parents. Besides, transtelephonic interrogation would not have revealed evoked response sensitivity changes or fluctuating thresholds in conventionally programmed devices. In young patients, a comprehensive and individual follow-up should be the preferred approach with remote follow-up only in selected patients. As the majority of young patients with permanent pacing systems suffer from congenital heart disease, a follow-up visit must include a cardiovascular assessment. In addition, the psychological impact of a device therapy should not be underestimated.21,22 Pacemaker dependencies in young or adolescent patients can have consequences for education and profession. Thus, it is important to offer an appropriate support, as well as counselling for the patients and their parents.
Clinical implications
A mean rate of device reprogramming of 0.7–1.1 per year has been demonstrated for patients with AC and conventionally programmed devices. Especially, the growing patient and those with potential risks for sudden ventricular threshold rise because of the underlying heart disease, a device with an automated adjustment to the actual ventricular threshold may be beneficial. AC-controlled pacing can be activated at device implant and provides reliable pacing.
Study limitations
This is a retrospective study reflecting contemporaneous pacing in paediatric patients with non-randomized patient groups for AC-controlled and conventional pacing. The conventionally paced group included more patients with complex congenital heart disease. Thus, a more diseased myocardium may have been present in the group Conv. In contrast, the great number of dual-chamber devices in the group AC could theoretically have resulted in a higher rate of reprogramming of atrial pacemaker settings when compared with group Conv.
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Conclusion |
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Ventricular device automaticity incorporated in the AC devices is a reliable feature with a favourable estimated freedom from device reprogramming as well as total yearly rate of device reprogramming. No difference was seen for the incidence of invasive re-interventions of the pacing systems between AC and conventionally programmed devices. A 6-monthly follow-up in young patients seems to be adequate to optimize device function and battery longevity as well as to ensure patient safety. Intermittent Holter recordings in patients with conventional as well as AC-programmed devices are suggested, especially in the presence of any change of symptoms or suspected dysfunction of the pacing system. Whether a further increase of device automaticity with possible limitation of programmability is beneficial has to be evaluated in further studies.
Conflict of interest: none declared.
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References |
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