Summary
Background
The reported failure rate of the Sprint Fidelis defibrillator lead (SFDL) has increased more than initially expected, with emerging evidence of accelerating fracture rates. Current consensus guidelines continue to discourage prophylactic lead extraction, citing major complication rates of 1.4–7.3%. Therefore, data relating to the risks of systematic SFDL extraction are lacking, with no methodical extraction protocol reported to date. Moreover, few statistical analyses have identified predictors of SFDL failure.
Objectives
The aims of this single-centre study were: to examine the safety and feasibility of systematic SFDL extraction at the time of pulse generator replacement or in case of lead failure; and to identify predictors of SFDL failure.
Methods
Between January 2005 and October 2007, 218 consecutive patients underwent transvenous SFDL implantation in our centre.
Results
During a mean follow-up of 43 ± 15 months, SFDL extraction was performed in 49 patients (22.5%) for the following reasons: inappropriate shocks ( n = 21; 9.6%), systematic extraction at time of pulse generator extraction ( n = 23; 10.5%), high impedance ( n = 3; 1.4%), high SFDL threshold ( n = 1; 0.4%) and cardiac device-related infection ( n = 1; 0.4%). No severe complications occurred, although two minor complications were reported (lead dislodgments). SFDL fracture was observed in 25 patients (11.5%; 3.2%/year incidence). The only predictor associated with SFDL fracture was the number of leads ( P = 0.01).
Conclusion
In our series, SFDL extraction at the time of pulse generator extraction or in case of evidence of lead failure was feasible and safe. Number of leads was identified as a new predictive factor for SFDL fracture.
Résumé
Introduction
Le nombre de ruptures des sondes de défibrillation Sprint Fidelis (SDSF) a augmenté très significativement au cours du temps. Les recommandations actuelles sont contre l’extraction systématique de ces sondes en raison d’un pourcentage de complications estimé entre 1,4 et 7,3 %. Cependant les travaux concernant les extractions de SDSF sont peu nombreux, rétrospectifs et sans protocole préalable.
Objectifs
Les objectifs de cette étude sont de deux ordres : premièrement, évaluer la faisabilité et la sécurité de l’extraction des SDSF lors du changement de boîtier ou lors d’une rupture de sonde ; deuxièmement, identifier les facteurs prédictifs de rupture de sondes.
Méthode et résultats
Entre janvier 2005 et octobre 2007, 218 patients ont bénéficié de la mise en place d’une SDSF dans notre centre. Au cours d’un suivi moyen de 43 ± 15 mois, une extraction de SDSF a été réalisée chez 49 patients (22,5 %) pour les raisons suivantes : chocs inappropriés chez 21 patients (9,6 %), une extraction systématique au cours d’un changement de boîtier chez 23 patients (10,5 %), une impédance élevée chez trois patients (1,4 %), un seuil élevé pour un patient (0,4 %) et une infection de dispositif chez un patient (0,4 %). Aucune complication majeure n’a été constatée et deux déplacements de sondes ont été observés. Une rupture de SDSF a été observée chez 25 patients (11,5 % ; 3,2 % rupture par an), et le seul facteur prédictif de rupture a été le nombre de sondes ( p = 0,01).
Conclusion
Dans notre série, l’extraction de sondes SDSF au moment du changement de boîtier ou lors d’une rupture de sondes est faisable avec des risques limités. Le seul facteur prédictif de rupture était le nombre de sondes implantées.
Background
The Sprint Fidelis defibrillator lead (SFDL) (models 6930, 6931, 6948 and 6949; Medtronic Inc., Minneapolis, Minnesota) is a 6.6-F bipolar high-voltage implantable cardioverter-defibrillator (ICD) lead . The lead was approved by the United States Food and Drug Administration in September 2004 and approximately 268,000 leads have been implanted worldwide . However, concerns about the early fracture rate of the lead were first reported in April 2007 and on 15 October 2007 the manufacturer suspended distribution of the SFDL . The reported SFDL failures have increased to a greater extent than initially expected, with failure rates estimated at 3.75% per year compared with the reported 1.7% per year in Medtronic’s February 2010 update registry . Current consensus guidelines discourage prophylactic lead extraction, citing major complication rates of between 1.4 and 7.3% . Thus, recommendations regarding management include routine monitoring every 3 months after adjusting impedance alarm thresholds or SFDL extraction in patients with pacemakers or with confirmed or suspected SFDL fractures . Two major multicentre surveys recently highlighted the risks associated with SFDL extraction in this clinical setting. Despite the large number of patients included in both multicentre studies, conclusions remain debatable due to several methodological shortcomings, such as retrospective evaluation, the absence of a systematic approach between centres and no long-term follow-up . Moreover, only a few studies have sought to identify predictors of SFDL fracture . Accordingly, the aim of this single-centre study was two-fold: to examine the safety and feasibility of systematic SFDL extraction at the time of pulse generator replacement or in case of evidence of lead failure; and to identify predictors of SFDL fracture.
Methods
Patient selection and implantation techniques
Between January 2005 and October 2007, 218 consecutive patients underwent transvenous SFDL implantation. Leads were inserted via left-sided or right-sided venous access by cephalic cutdown or via subclavian vein access using standard techniques. Leads were positioned in the right ventricular (RV) apex. Defibrillation safety margins as well as pacing and sensing thresholds were determined according to usual practices in order to ensure adequate detection and termination of ventricular tachyarrhythmias, while providing rate support in the event of bradycardia. Atrial and left ventricular leads were added in patients requiring multichamber pacing and sensing. All ICD implantations conducted at our centre were recorded, while patient follow-up was carried out in our outpatient clinic. The SFDL model most frequently implanted was the dual-coil active-fixation lead (model 6949), followed by the single-coil active-fixation lead (model 6931). All patients with SFDL were identified, with details on any lead fractures being recorded in line with the recommendations of the Agence française de sécurité sanitaire des produits de santé (Afssaps).
Monitoring
In accordance with the manufacturers’ recommendations, we reprogrammed devices and activated alarms in order to provide patients with a warning system in the event of impedance changes suggesting a lead fracture.
Endpoints
Lead failure was defined as non-physiological high-rate sensing with high pacing impedance suggesting a fracture, sudden change in sensing or pacing impedance, or rise in high-voltage impedance suggestive of coil fracture, resulting in the decision to perform lead replacement. Inappropriate shocks due to sensing of electrical noise artefacts from make-break potentials were also defined as SFDL fractures. At the time of pulse generator replacement, SFDL extraction was systematically performed in all patients except for those aged 80 years or more.
Data retrieval
Clinical and device interrogation data were retrieved from the ICD database. Additional data were obtained from local clinical records and from the ‘save to disk’ files of patients with Sprint Fidelis model 6949 lead fractures. Between January 2008 and May 2011, each patient device was interrogated every 3 months in the outpatient clinic in line with the Afssaps recommendations. If available, telemonitoring was activated and data were analysed. The following variables were examined as potential predictors of lead fracture: age, risk factors, sex, vein of access (cephalic or non-cephalic), cardiomyopathy aetiology, number of electrodes implanted, device type (single chamber, double chamber or resynchronization), weight and most recent left ventricular ejection fraction (LVEF).
Extraction
Surgical reintervention was defined as a surgical procedure required for non-infectious or infectious implant complications. The extraction was performed using either simple traction or traction devices. Simple traction involved manipulating the lead so that it left the vasculature via the implant vein by using tools typically supplied for lead implants, with the addition of traction. These tools included items such as standard stylets (non-locking) and fixation screw retraction clips. Traction devices involved locking stylets, snares and sutures as well as grasping or other devices used to engage, entrap and remove the lead or lead fragments. Locking stylets are a special type of traction device designed to grasp the inside of the conductor coil along its length or near the distal stimulating electrode, thus improving tensile properties and preventing elongation of the lead body during traction . If traction alone did not result in successful lead extraction, a laser-powered sheath system (Spectranetics Inc., Colorado Springs, CO, USA) was used. Major complications were defined as the following events: death; cardiac or vascular avulsion or tear requiring thoracotomy, pericardiocentesis, chest tube or surgical repair; pulmonary embolism requiring surgical intervention; respiratory arrest or anaesthesia complications leading to prolongation of hospitalization; stroke; and pacing system-related infection of a previously non-infected site. Minor complications were defined as: pericardial effusion not requiring pericardiocentesis or surgical intervention; haemothorax not requiring a chest tube; haematoma at the surgical site requiring reoperation for drainage; arm swelling or thrombosis of implant veins necessitating medical intervention; haemodynamically significant air embolism; migrated lead fragment without sequelae; blood transfusion related to blood loss during surgery; pneumothorax requiring a chest tube; and pulmonary embolism not requiring surgical intervention. Patients were followed up in hospital, with 30-day procedure-related outcomes being reported.
Follow-up
In line with the Afssaps recommendations, the collected prospective data included: patient demographic and clinical characteristics; echocardiographic measurements; type of implanted device and number of leads; defibrillator interrogation; and occurrence of complications requiring reintervention. Patients were followed up by four experienced cardiologists. Electrocardiograms and device controls were performed the day after the procedure and immediately before patient discharge. Patients were examined in the outpatient clinic every 3 months, with a physical examination and device interrogation being carried out at these visits, in addition to weekly telemonitoring.
Statistical analysis
All clinical variables were assessed at the time of device implantation, with continuous variables expressed as mean ± standard deviation. Comparisons of continuous variables between the patient groups were conducted using the unpaired Student’s t test or the Mann-Whitney test as appropriate. Categorical variables were compared using the chi-square test or Fisher’s exact test as appropriate. The cumulative risk of SFDL fracture was interpreted using Kaplan-Meier curves and analysed by means of the log-rank test. Univariate analysis was fitted in order to investigate the relationship between each covariate and the risk of SFDL fracture. Backward elimination was also used, removing the least significant variables at each step to elaborate multivariable models if necessary. A probability value of P < 0.05 was considered statistically significant. All analyses were performed using StatView ® 5.0 (StatView IV; Abacus Concept, Berkeley, CA, USA).
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