Subcutaneous Implantable Cardioverter Defibrillator: A Contemporary Overview

The difference between subcutaneous implantable cardioverter defibrillators (S-ICDs) and transvenous ICDs (TV-ICDs) concerns a whole extra thoracic implantation, including a defibrillator coil and pulse generator, without endovascular components. The improved safety profile has allowed the S-ICD to be rapidly taken up, especially among younger patients. Reports of its role in different cardiac diseases at high risk of SCD such as hypertrophic and arrhythmic cardiomyopathies, as well as channelopathies, is increasing. S-ICDs show comparable efficacy, reliability, and safety outcomes compared to TV-ICD. However, some technical issues (i.e., the inability to perform anti-bradycardia pacing) strongly limit the employment of S-ICDs. Therefore, it still remains only an alternative to the traditional ICD thus far. This review aims to provide a contemporary overview of the role of S-ICDs compared to TV-ICDs in clinical practice, including technical aspects regarding device manufacture and implantation techniques. Newer outlooks and future perspectives of S-ICDs are also brought up to date.

Axillary vein access for antiarrhythmic cardiac device implantation: a literature review

The current narrative review provides an update of available knowledge on venous access techniques for cardiac implantable electronic device implantation, with a focus on axillary vein puncture. Lower procedure-related and lead-related complications have been reported with extrathoracic vein puncture techniques compared with intrathoracic accesses. In particular, extrathoracic lead access through the axillary vein seems to be associated with lower complication incidence than subclavian vein puncture and higher success rate than cephalic vein cutdown. In literature, many techniques have been described for axillary vein access. The use of contrast venography-guided puncture has facilitated the diffusion of the axillary vein approach for device implantation. Venography may be particularly useful in specific demographic and clinical device implantation contexts. Ultrasound-guided or microwire-guided vascular access for lead positioning can be considered a valid alternative to venography, although current applications for axillary vein puncture need further evaluations.

Lead age as a predictor for failure in pediatrics and congenital heart disease

BACKGROUND

Pediatric and congenital heart disease (CHD) patients have a high rate of transvenous (TV) lead failure.

OBJECTIVE

To determine whether TV lead age can aid risk assessment for lead failure to guide the decision of whether a lead should be replaced or reused at the time of a generator change.

METHODS

Retrospective cohort study of patients <21 years old undergoing TV device implant from 2000 to 2014 at our institution. Patient, device, and lead variables were collected. Leads were compared in groups based on how many generator changes were completed.

RESULTS

A total of 393 leads in 257 patients met inclusion criteria, 60 leads failed (15%). Failed leads were more likely to have not yet undergone generator change (p = .048). CHD (p = .045), Tendril lead type (p = .02) and silicone insulation (p = .02) were associated with failure. In multivariate analysis, younger leads (p = .022), number of generator changes (p = .003), CHD (p = .005) and silicone insulation (p = .004) remained significant while Tendril lead type did not (p = .052). Survival curves show an early decline around 4 years.

CONCLUSIONS

Lead failure rate in pediatric and CHD patients is high. Leads that have not yet undergone a generator change were more likely to fail in this cohort. The strategy of serial replacement based on lead age needs further research to justify in this population.

Successful implantation of leadless pacemakers in children: a case series

Background

A leadless pacemaker is a new concept in which a miniaturized pacing device is self-contained within the heart. Recently published data show that leadless pacemakers are associated with a decreased risk of major complications when compared with transvenous cardiac pacemakers. This seems to be of particular importance in children and young adults in whom various complications may occur during their lifetime.

Case summary

Herein, we report the successful implantation of Micra™ Transcatheter Pacing System in two children: 12-year-old boy and 13-year-old girl, along with a long-term follow-up. The children had indications for pacemaker implantation, however, with an expected low percentage of pacing due to paroxysmal nature of the third-degree atrioventricular block. The implantation procedures were performed in general anaesthesia. There were no complications. During the 2-year follow-up, there were no adverse events and the electrical parameters of the device remained stable. Pacing percentage was below 0.1%.

Discussion

Transvenous cardiac pacemakers improve quality of life and reduce mortality but may be associated with various short- and long-term complications, mainly related to the presence of transvenous leads and the pulse generator. Compared with adult patients, the implantation of conventional pacemakers in children is still a challenge, not only because of their smaller size but also due to continuing growth, as well as a higher rate of lead and device-related complications. We demonstrate that the implantation of leadless pacemakers in children is feasible and could be worth considering in certain clinical scenarios, especially when ventricular pacing is required rarely.

Congenital heart block: Pace earlier (Childhood) than later (Adulthood)

Congenital complete heart block (CCHB) occurs in 2-5% of pregnancies with positive anti-Ro/SSA and/or anti-La/SSB antibodies, and has a recurrence rate of 12-25% in a subsequent pregnancy. After trans-placental passage, these autoantibodies attack and destroy the atrioventricular (AV) node in susceptible fetuses with the highest-risk period observed between 16 and 28 weeks' gestational age. Many mothers are asymptomatic carriers, while <1/3 have a preexisting diagnosis of a rheumatic disease. The mortality of CCHB is predominant in utero and in the first months of life, reaching 15-30%. The diagnosis of CCHB can be confirmed by fetal echocardiography before birth and by electrocardiography after birth. Whether early in-utero detection and treatment might prevent or reverse this condition remains controversial. In addition to autoantibody-associated CCHB, there is also an isolated (absent structural heart disease) nonimmune early- or late-onset heart block detected later in childhood that may be associated with specific genetic markers or other pathogenic mechanisms. In isolated immune or non-immune CCHB, cardiac pacemakers are implanted in symptomatic patients, however, data on the natural history of CCHB in the adult life indicate that all patients, even if asymptomatic, should receive a pacemaker when first diagnosed. However, important issues have emerged in these patients wherein life-long conventional right ventricular apical pacing may produce left ventricular dysfunction (pacing-induced cardiomyopathy) necessitating a priori alternate site pacing or subsequent upgrading to biventricular pacing. All these issues are herein reviewed and two algorithms are proposed for diagnosis and management of CCHB in the fetus and in the older individual.

Comparison of the Medtronic SelectSecure and conventional pacing leads: Long-term follow-up in a multicenter pediatric and congenital cohort

INTRODUCTION

The Medtronic SelectSecure™ (Minneapolis, MN, USA) pacing lead (SS) has theoretical advantages compared to conventional (C) transvenous pacing leads (PLs). The study purpose was to determine whether differences in electrical function and lead survival exist between these PLs in a large data set of pediatric and congenital patients.

METHODS

A multicenter historical longitudinal cohort study was performed comparing SS and CPL performance over a 72-month follow-up (FU). Ten centers provided data for both SS and CPL, matched for age, implanted pacing chamber, time period of implantation, and presence of heart disease.

RESULTS

The cohort consisted of 141 subjects in each group. No statistical differences were observed in age, gender, presence of heart disease, or pacing indication. Atrial and ventricular capture thresholds were stable throughout FU and higher in the SS group (atrial: 0.75 ± 0.02 vs 0.5 ± 0.04 V, ventricular: 1.0 ± 0.04 vs 0.75 ± 0.04 V), P < 0.001. Group PL sensing thresholds did not differ. The SS group required greater energy to pace (atrial: 0.57 ± 0.05 vs 0.32 ± 0.02 mJ, ventricular: 0.83 ± 0.05 vs 0.56 ± 0.06 mJ), P = 0.001. Early lead dislodgement and phrenic nerve stimulation were greater in the SS group (P = 0.03). Long-term lead survival was high and similar between the two groups, P = 0.35.

CONCLUSIONS

Long-term survival of both PL was high with a low fracture rate. The SS had excellent electrical function but did show higher capture thresholds and increased energy to pace; these differences are offset by other advantages of the SS PL.

Long-term reliability of the defibrillator lead inserted by the extrathoracic subclavian puncture

BACKGROUND

As the transvenous defibrillator lead is fragile and its failure may cause a life-threatening event, reliable insertion techniques are required. While the extrathoracic puncture has been introduced to avoid subclavian crush syndrome, the reports on the long-term defibrillator lead survival using this approach, especially the comparison with the cephalic cutdown (CD), remain scarce. We aimed to evaluate the long-term survival of the transvenous defibrillator lead inserted by the extrathoracic subclavian puncture (ESCP) compared with CD.

METHODS

Between 1998 and 2011, 324 consecutive patients who underwent an implantable cardioverter-defibrillator (ICD) implantation in Hokkaido University Hospital were included. ICD leads were inserted by CD from 1998 to 2003 and by contrast venography-guided ESCP thereafter. Lead failure was defined as a nonphysiologic high-rate oversensing with abnormal lead impedance or highly elevated sensing and pacing threshold.

RESULTS

Of 324 patients, CD was used in 37 (11%) and ESCP in 287 patients (89%). During the median follow-up of 6.2 years (IQR:3.2-8.3), 7 leads (2 in CD and 5 leads in ESCP group) failed. All patients with lead failure in ESCP group were implanted with either SJM Riata (n = 1) or Medtronic Fidelis lead (n = 4). Five-year lead survival was 93.8% (CI95%:77.3-98.4%) in CD compared with 99.1% (CI95%:96.6-99.8%) in ESCP group (P = 0.903). Univariate Cox regression analysis showed that the use of Fidelis or Riata lead was the strong predictor of the ICD lead failure (HR 13.8, CI95%:2.9-96.5; P = 0.001).

CONCLUSIONS

Contrast venography-guided extrathoracic puncture ensures the reliable long-term survival in the transvenous defibrillator leads.

Multiple pacemaker lead breakages due to clavicle dislocation following clavicle fracture

A 58-year-old man undergoing cardiac resynchronization therapy with a defibrillator in his right subcostal area fell from his bed, leading to fracture of the right clavicle. Serial radiographs showed dislocation of the distal clavicle 2 months after the initial fracture. Lead parameters dramatically changed after dislocation of the distal clavicle. Radiography indicated that the device leads seemed to be compressed by the distal clavicle in certain positions of the right upper limb. It was likely that various movements of the right upper limb during his daily life insidiously damaged the device leads, leading to the lead breakages.

Low incidence of complications after cephalic vein cutdown for pacemaker lead implantation in children weighing less than 10 kilograms: A single-center experience with long-term follow-up

BACKGROUND

Only a few studies on the cephalic vein cutdown technique for pacemaker lead implantation in children weighing ≤10 kg have been reported even though the procedure is widely accepted in adults.

OBJECTIVE

The purpose of this study was to prove that cephalic vein cutdown for pacemaker lead implantation is a reliable technique with a low incidence of complications in children weighing ≤10 kg.

METHODS

The study included 44 children weighing ≤10 kg with an endocardial pacemaker. Cephalic, subclavian, and axillary vein diameters were measured by ultrasound before implantation. The measured diameters were used to select either an endocardial or epicardial surgical technique. Regular 6-month follow-up visits included pacemaker interrogation and clinical and ultrasound examinations.

RESULTS

Two dual-chamber and 42 single-chamber pacemakers were implanted. Mean weight at implantation was 6.24 kg (range 2.25-10.40 kg), and mean age was 11.4 months (range 1 day-47 months). In 40 children (90.1%), the ventricular leads were implanted using the cephalic vein cutdown technique, and implantation was accomplished via the prepared right external jugular vein in 4 of the children (9.9%). The atrial leads were implanted using axillary vein puncture and external jugular vein preparations. Mean follow-up was 8.9 years (range 0-20.9 years). Only 1 pacemaker-related complication was detected (a lead fracture near the connector that was successfully resolved using a lead repair kit).

CONCLUSION

The cephalic vein cutdown technique is feasible and reliable in children weighing ≤10 kg, which justifies the application of additional surgical effort in the treatment of these small patients.

Clinical Predictors of Fidelis Lead Failure

Background—

Approximately 268 000 Fidelis leads were implanted worldwide until distribution was suspended because of a high rate of early failure. Careful analyses of predictors of increased lead failure hazard are required to help direct future lead design and also to inform decision making on lead replacement. We sought to perform a comprehensive analysis of all potential predictors in a multicenter study.

Methods and Results—

A total of 3169 Sprint Fidelis leads were implanted in 11 centers with a total of 251 failures. Lead failure rates at 3, 4, and 5 years were 5.3%, 10.6%, and 16.8%, respectively. The rate of lead failure continues to accelerate ( P <0.001). There were 4 independent predictors of failure: center, sex, access vein, and previous lead failure. Women had a higher hazard of failure (hazard ratio 1.51; 95% confidence interval, 1.14–2.04; P =0.005). Both axillary and subclavian access increased the hazard of failure ( P =0.007); hazard ratio for axillary was 1.94, (95% confidence interval, 1.23–3.04) and for subclavian 1.63 (95% confidence interval, 1.08–2.46). Previous lead failure increased the hazard of a subsequent Fidelis failure with a hazard ratio of 3.12 (95% confidence interval, 1.80–5.41; P <0.001).

Conclusions—

The rate of Fidelis failure continues to increase over time, with failures approaching 17% at 5 years. Women, patients with leads inserted via the subclavian or axillary vein, and those with a previous lead fracture were at greatest risk of Fidelis failure. Our data suggest that Fidelis replacement should be strongly considered at the time of generator replacement.

Long-term outcome of transvenous bipolar atrial leads implanted in children and young adults with congenital heart disease

AIMS

Atrial leads are often implanted in paediatric patients needing a pacemaker (PM). The aim of this study is the evaluation of their outcome in young patients.

METHODS AND RESULTS

We evaluated transvenous atrial leads outcome in children and young adults from a single centre, with a retrospective analysis. A P< 0.05 was considered significant. Between 1992 and 2008, 110 patients, 75 with congenital heart defects (d-transposition of great arteries status/post, s/p, Mustard 41%, atrioventricular septal defect 11%, tetralogy 9%, ventricular septal defect 8%), aged 13.3 ± 5.3 years, underwent PM implantation with bipolar atrial transvenous leads for sinus node dysfunction (50%), atrioventricular block (38%), cardiomyopathies, and primary ventricular arrhythmias (12%). Leads are steroid-eluting (98%), tined (59%), screw-in (41%), polyurethane-insulated (72%), silicone-insulated (28%), and have been positioned by transcutaneous puncture of subclavian vein into right atrial appendage/remnant (RAA, 50%), right atrial free wall/septum (25%), left atrium (s/p Mustard, 25%). Follow-up duration is 6.4 ± 4.8 (range 0.1-18) years. At multivariate analysis, younger age at implant was a risk factor for lead failure (4 leads, 3.5%) (P= 0.03); 16 leads (14%) dislodged post-implantation and 12 were successfully repositioned, the others extracted or abandoned. Dislocation occurred more frequently with screw-in leads (P= 0.03) positioned outside RAA (P= 0.02). Atrial threshold showed a small but significant increase, 0.002 V/month (P< 0.001), impedance showed a decrease (0.6 Ω/month, P< 0.001), P-wave showed no significant difference.

CONCLUSIONS

Transvenous bipolar atrial leads have good long-term results in young patients, with a very low rate of lead failure. Older age at implant can further reduce this rate. Lead dislodgement is frequent in the post-operative period.

Potential of gallium-based leads for cardiac rhythm management devices

We propose the use of gallium (Ga), a metal that is liquid at physiological temperatures, or one of its alloys, for use as the conducting material in the leads of implantable pacemakers or cardioverter defibrillators. It is proposed that a liquid conductor will make these leads more pliable and thus less susceptible to fracture in situ. As an initial step towards utilizing liquid gallium in leads, the biocompatibility of Ga was investigated via cytotoxicity, hemocompatibility, and intracutaneous injection testing. Unipolar pacing Ga prototypes were fabricated by adapting existing pacemaker leads. The electrical impedance and pulse transmission ability of these leads were examined. Ga was well tolerated both in vitro and in vivo. Additionally, the Ga prototypes conductors behaved as low magnitude resistances that did not distort pulses as generated by conventional pacemakers. These results indicate that Ga is an appropriate material for implantable cardiac stimulators and will be a focus of our liquid metal prototypes.

A single institution experience with pacemaker implantation in a pediatric population over 25 years

BACKGROUND

With the development of new technical devices and software more appropriate for pediatric patients, pacemaker implantations in children and young adults have increased over time. It is necessary to monitor the mid- and long-term consequences. The decision for the implantation of a cardiovertor defibrillator (ICD) in children remains challenging despite technical improvements.

OBJECTIVE

To assess the safety of pacemaker implantation in children, to review old and new indications, and to point out changes of management over time.

PATIENTS AND METHODS

Between 1984 and 2009, 181 patients required the implantation of a pacemaker or an ICD device at the Heart and Diabetes Centre in Bad Oeynhausen, Germany. Their charts have been reviewed pro- and retrospectively for indications, complications, longevity of the device, and the natural course.

RESULTS

Indications have been high-degree atrioventricular block in 65% (postoperative 55%) and sinus node dysfunction in 24% (postoperative 90%), including three patients with vasovagally mediated significant bradycardia. Eleven percent required the implantation of an ICD device secondary to significant ventricular arrhythmias. The indication was class II in one-third of all patients. Complications requiring revision occurred in six patients (3.3%); one of them required removal of the device due to an infection. Ten patients died, but none related to pacemaker implantation.

CONCLUSION

Pacemaker implantation even in young pediatric patients is generally safe. No complication led to the death of a patient. The number of class II indications has been increasing. The future aim is to improve pediatric algorithms and to prevent unnecessary pacing.

Axillary versus infraclavicular placement for endocardial heart rhythm devices in patients with pediatric and congenital heart disease

Our objective was to evaluate the implant and mid-term outcomes of transvenous pacemaker or internal cardioverter-defibrillator placement by alternative axillary approaches compared to the infraclavicular approach in a pediatric and congenital heart disease population. We conducted a retrospective review of all patients with new endocardial heart rhythm devices placed at 4 pediatric arrhythmia centers. A total of 317 patients were included, 63 had undergone a 2-incision axillary approach, 51 a retropectoral axillary approach, and 203 an infraclavicular approach. Congenital heart disease was present in 62% of the patients. The patients with the 2-incision axillary approach were younger and smaller. The patients with the retropectoral axillary approach were less likely to have undergone previous cardiac surgery and were more likely to have had an internal cardioverter-defibrillator placed. The duration of follow-up was 2.4 ± 1.9 years for the 2-incision axillary, 2.6 ± 2.6 years for retropectoral axillary, and 3.5 ± 1.4 years for the infraclavicular technique (p = 0.01). No differences were seen in implant characteristics, lead longevity, implant complications, lead fractures or dislodgements, inappropriate internal cardioverter-defibrillator discharges, or device infections among the 3 groups. In conclusion, our data support that the outcomes of axillary approaches are comparable to the infraclavicular approach for endocardial heart rhythm device placement and that axillary approaches should be considered a viable option in patients with pediatric and congenital heart disease.