Europace Advance Access originally published online on April 29, 2008
Europace 2008 10(7):844-847; doi:10.1093/europace/eun109
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Pacing
Patient- and lead-related factors affecting lead fracture in children with transvenous permanent pacemaker
1 Division of Pediatric Cardiology, Department of Pediatrics, Ataturk University, Erzurum, Turkey; 2 Division of Pediatric Cardiology, Department of Pediatrics, Hacettepe University, Ihsan Dogramaci Children Hospital, Sihhiye, Ankara, Turkey
Manuscript submitted 11 January 2008. Accepted after revision 7 April 2008.
* Corresponding author. Tel: +90 312 3051157; fax: +90 312 3090220.E-mail address: alpayceliker{at}gmail.com; aceliker{at}hacettepe.edu.tr
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Abstract |
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Aims: Fracture in transvenous pacing leads is one of the most common reasons for lead abandonment. Although the factors affecting lead failure rates have been investigated, there is no study evaluating the clinical parameters that affect lead fracture in children. We report our experience with lead fracture in children with transvenous pacemakers.
Methods and results: The follow-up results of 264 leads from 184 patients were evaluated using pacemaker follow-up data. Underlying conditions, implant data, and lead features were evaluated for the analysis of lead fracture. During a mean follow-up of 72.8 ± 39.7 months (range 3.2–160.6, median 70), lead fracture developed in 19 leads (7.2%) from 18 patients. The mean duration between implantation and lead fracture was 57.3 ± 35 months (range 6.8–130, median 51). All fractures occurred in the leads implanted by the infraclavicular subclavian approach. Cumulative survival at the end of 5 years was 92.7% in terms of lead fracture. None of the patient-related risk factors correlated with lead fracture. Multivariate analyses of lead-related risk factors revealed a significant correlation only between lead fracture and fixation mechanism (P < 0.05).
Conclusion: Our results indicated that none of the patient-related risk factors was correlated with lead fracture. Among lead-related risk factors, only the fixation mechanism was found to be correlated with lead fracture; thus, it seems that passive fixation mechanism is safer in terms of lead fracture. Although all fractures occurred in the leads implanted by the intrathoracic subclavian approach, statistical analysis revealed no significance for this parameter. The effect of the extrathoracic approach should be investigated in a large group of patients.
Key Words: Children, Endocardial, Lead fracture, Pacemaker, Transvenous
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Introduction |
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Transvenous-endocardial pacing has become standard practice for children who require pacemaker therapy. Pacing leads are usually inserted through the subclavian vein down to the right atrium or ventricle. During follow-up, lead malfunction necessitating lead replacement may develop. Lead malfunction may be caused by lead fracture, adapter malfunction, infection, or lead migration.1
Lead fracture occurs infrequently in children. In a patient who is pacemaker-dependent, lead fracture may result in pacing and sensing problems and can rarely have fatal consequences.2 To the best of our knowledge, there is no study in the available literature that evaluates the clinical parameters that affect lead fracture in children. In this study, our experience with lead fracture in a relatively large group of children with transvenous pacemakers is reported. The study also aimed at investigating the patient, technique, and lead-related risk factors that correlate with lead fracture. |
Methods |
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We retrospectively reviewed the records of the paediatric patients who underwent endocardial lead implantation between February 1994 and December 2005. The data of these patients were collected by reviewing the patients' medical records and computerized departmental pacemaker databases. The patients whose initial device and/or lead implants were inserted in another centre were also included. The variables were: (i) patient-related information including diagnosis, surgical history, and follow-up duration; (ii) implant procedure characteristics; (iii) lead hardware factors; and (iv) lead fracture information including symptoms, mode of detection, and complications.
The leads were implanted under ketamine anaesthesia via percutaneous puncture of the vein. After appropriate measurements were made, the batteries were implanted subcutaneously or subpectorally. Lead function was determined by measuring impedance, pacing threshold, and sensed electrogram amplitude. Follow-up testing was performed at the time of discharge and in the 1st, 3rd, and 6th month and every 6 months thereafter. The evaluation included routine clinical examination, electrocardiogram, chest X-ray, and a full analysis of the pacing system using the specific analysers provided by the manufacturers. The systems were additionally interrogated when the patients complained of any problem that might have been related to pacemaker or lead malfunction.
Lead data were evaluated for the following outcomes: elective lead change, patient death, pacing system abandonment or removal for reasons other than lead fracture, and patient lost to follow-up or termination of the study period. Five patients who never visited our clinic after implantation were excluded from the study. The patients and leads were compared with identify variables correlating with lead fracture. Patient- and lead-related risk factors were identified using the Cox proportional hazard analysis. Multivariate analyses were performed using Cox proportional hazards with entry criteria of univariate P < 0.2. Estimated lead survivals were plotted using the Kaplan–Meier analysis. P-value of less than 0.05 was considered statistically significant.
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Results |
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Between 1994 and 2005, 271 transvenous endocardial pacemaker leads were implanted in 189 patients in our centre. Seven leads (five patients) were excluded from the study because patients were lost to follow-up after implantation. Thus, the results of 264 leads from 184 patients were included in the evaluation. For all leads, the mean patient age at implantation was 10.4 ± 5.6 years (range 0.5–25, median 10) and the mean follow-up was 72.8 ± 39.7 months (range 3.2–160.6, median 70).
Lead fracture developed during follow-up in 19 leads (7.2%) from 18 patients (1 patient developed 2 lead fractures) (Table 1). The indications for pacemaker implantation were post-operative surgical heart block (n = 13), congenital advanced heart block (n = 3), and sinus node dysfunction (n = 2). Thirteen patients with fractured leads (72%) had congenital heart disease, tetralogy of Fallot (n = 4), ventricular septal defect (n = 4), transposition of great arteries (n = 2), congenital corrected transposition of great arteries (n = 1), atrioventricular septal defect (n = 1, two leads fractured), and subaortic discrete membrane (n = 1). Seventeen of the fractured leads (89.5%) were ventricular and two (10.5%) were atrial. The fracture was in the subclavian vein in 18 and in the right ventricle (at two points) in one electrode. Sixteen of the fractured leads (84.2%) were introduced via the right subclavian vein and three (15.8%) via the left subclavian vein. The batteries were implanted subpectorally in 16 patients and subcutaneously in 3 patients. The mean duration between implantation and lead fracture was 57.3 ± 35 months (range 6.8–130, median 51) (Table 2). Lead fracture was determined during routine follow-up in the case of 9 leads (47%) or due to the complaints of the patients suggesting lead or pacemaker failure in 10 leads (53%). Lead fracture presented with symptoms in 10 (53%) leads, and the patient had severe symptoms such as syncope or dizziness in 9 leads. Seven patients were pacemaker-dependent.
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None of the patient-related risk factors correlated with lead fracture. In the univariate level, only the fixation mechanism was significantly related to lead fracture (P < 0.05). Multivariate analyses of the lead-related risk factors, which had a P-value of less than 0.2 on univariate level, revealed a significant correlation only between lead fracture and fixation mechanism (Table 1). Active-fixation leads were more frequent in Group 2 (with fractured leads).
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Discussion |
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Since the development of transvenous pacemaker systems, new complications related to intravascular leads have appeared. Problems with intravascular pacemaker leads are dislodgement from the endomyocardial site, conductor fracture, insulation failure, and infection and thrombus formation.3
–5 The first three complications result in lead failure.3 Lead failure may cause arrhythmias, under or oversensing and failure to capture, and exposes the patient to a vital risk, thus justifying the replacement of the lead.6,7 Although some studies have investigated the factors affecting lead failure in children, no studies have been performed to date to investigate lead fracture alone.1,3,4,8–11 Total verified lead failure rate is reported as 1.3% by Helguera et al.12 in adults. In children, overall 5-year survival rate of endocardial leads is reported to be between 76 and 89%.1,3,4,11 Overall, 5-year survival rates of endocardial leads in children are significantly lower than those reported for adults.12 It has been speculated that the significantly more active lifestyle of children presumably contributes to the observed higher lead failure rate when compared with adults.5 The results of the present study have the same implications. The most commonly reported reasons for lead failure are dislodgement, exit block, and lead fracture.1,3 Approximately 22.9% of the transvenous lead failures in children result from lead fracture, as was mentioned in a pioneer study.1 Previous studies have evaluated the effects of different factors on transvenous lead survival.3,11,13 Fortescue et al.11 reported younger age at implant and history of congenital heart defects as being significantly correlated with earlier lead failure. In our study, the cumulative survival of the leads at the end of 5 years was 92.7%, in terms of lead fracture (Figure 1). Although the fracture rate was higher than seen in previously reported series (Table 3), the mean follow-up of the present study was nearly twice as long as that of earlier studies. Two-thirds of the fractures occurred after the 5th year of implantation. Thus, lead fracture rate may increase with longer follow-up duration.
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Physiological features of the paediatric heart differ from those of the adult heart. Structural cardiac problems and indications for permanent pacing in children are thus very different, and this may affect the lead fracture ratio in children. The frequency of previous cardiac surgery is higher among children, which was also apparent in our study. However, to date, the effects of these factors on lead fracture ratio in children have not been investigated. In our study, none of the patient-related risk factors, such as age at implantation, indications for implantation, or the presence of any type of congenital heart disease or previous heart surgery, was significantly related to lead fracture (Table 1). This result suggests that patient-related factors previously reported to affect lead failure may not, in fact, have an impact on lead fracture.
Although intrathoracic access, subpectoral implants, right-sided implantation, and active-fixation leads were more frequent in the lead fracture group, statistical analysis revealed a correlation only between fixation mechanism and lead fracture. Lead placement in the cephalic vein, axillary vein, or extrathoracic portion of the subclavian vein has been advocated to avoid entrapment of lead in the subclavius muscle, which is implicated in the subclavian crush syndrome.5,14–19 In the present study, 37 leads were implanted by puncture of axillary vein or extrathoracic portion of the subclavian vein, and none of them fractured during a mid-term follow-up period of nearly 4 years. Although none of the extrathoracically implanted leads was fractured, statistical analysis revealed no significant difference when compared with the outcome with the intrathoracic approach. This may be explained by the low number of leads implanted extrathoracically and the shorter follow-up duration. Despite the lack of statistical significance, the absence of fracture in patients with extrathoracically implanted leads is thought to be an encouraging finding, which may be useful for implant methodology.
The only parameter that was found to be correlated with lead fracture was the fixation mechanism, with fracture more frequent among the leads with an active-fixation mechanism. In active-fixation leads, the inner coil is used to turn to screw the distal end into the myocardium or to retract the screw back into the lead. It can be speculated that the repeated screwing–retraction action during implantation of the lead in an effort to find the most suitable location in the heart may have a deleterious effect on the inner coil and may result in weakness in the lead body. This postulated mechanism may be a cause of lead fracture, which was determined to be more frequent in active-fixation leads.
In conclusion, lead fracture is an important problem in children with transvenous pacemakers. Our results have indicated that none of the patient-related risk factors was correlated with lead fracture. Among lead-related risk factors, only the fixation mechanism was found to be correlated with lead fracture, which may be postulated as screw mechanism-related inner coil damage during implantation. Although all fractures occurred in leads implanted by the intrathoracic subclavian approach, it was not correlated with fracture. Hence, the effect of the extrathoracic approach should be investigated in a large group of patients with a longer follow-up.
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Acknowledgements |
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We express our gratitude to Prof. Ömer Akbulut for his help with statistical analysis of our data. The study was performed at Hacettepe University, Faculty of Medicine, Division of Pediatric Cardiology, Ankara, Turkey.
Conflict of interest: none declared.
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References |
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