Author + information
- Received July 21, 2015
- Revision received September 9, 2015
- Accepted September 24, 2015
- Published online February 1, 2016.
- Tom F. Brouwer, MDa,∗ (, )
- Antoine H.G. Driessen, MDb,
- Louise R.A. Olde Nordkamp, MD, PhDa,
- Kirsten M. Kooiman, CCDSa,
- Joris R. de Groot, MD, PhDa,
- Arthur A.M. Wilde, MD, PhDa and
- Reinoud E. Knops, MDa
- aDepartment of Clinical and Experimental Cardiology, Heart Center, Amsterdam Medical Center, University of Amsterdam, Amsterdam, the Netherlands
- bDepartment of Cardiothoracic Surgery, Heart Center, Amsterdam Medical Center, University of Amsterdam, Amsterdam, the Netherlands
- ↵∗Reprint requests and correspondence:
Dr. Tom F. Brouwer, Department of Cardiology, Academic Medical Center, P.O. Box 22700, 1100 DE Amsterdam, the Netherlands.
Objectives This study assessed outcomes in patients in whom subcutaneous implantable cardioverter-defibrillator (S-ICD) therapy was continued after implantation-related complications, in order to avoid conversion to transvenous ICD therapy.
Background Patients at risk for sudden cardiac death benefit from ICD therapy, despite a significant risk for complications. S-ICD has a similar complication rate as transvenous ICD therapy, but the absence of transvenous leads may hold long-term benefits, especially in young ICD patients.
Methods In the largest single-center cohort available to date, S-ICD patients implanted between 2009 and 2015 were included.
Results There were 123 patients at a median age of 40 years. During a median follow-up of 2 years, 10 patients (9.4%) suffered implant-related complications. There were 5 infections, 3 erosions, and 2 implant failures for which 21 surgical procedures were needed. In 9 of 10 patients, S-ICD therapy could be continued after intervention. In 6 patients, the period between extraction and reimplantation of the S-ICD system was bridged with a wearable cardioverter-defibrillator (WCD). The pulse generator was reimplanted at the original site in 5 patients and in 3 underneath the serratus anterior muscle. One patient was not reimplanted following extraction due to recurrent infections. Conversion to a transvenous ICD was not needed in any patient.
Conclusions In most patients with a complication, S-ICD therapy could be continued after intervention, avoiding the need to convert to a transvenous system. Bridging to recovery with a WCD and submuscular implantation of the pulse generator are effective treatment strategies to manage S-ICD complications.
Patients at high risk of sudden cardiac death benefit from implantable cardioverter-defibrillator (ICD) therapy. Conventional transvenous ICDs have been demonstrated to increase survival, despite the fact that approximately 10% to 15% of patients experience implant-related or long-term complications (1–5). A proportion of these complications are related to the use of transvenous leads, causing significant morbidity such as thrombotic events, cardiac perforation, and lead endocarditis. Failure of transvenous leads, reported to be between 37% and 40% at 8 to 10 years' follow-up, results in inappropriate shocks, lead-extraction-related complications, and failure to effectively detect and convert ventricular arrhythmias (2,6,7). These are important limitations of transvenous ICD therapy and are particularly relevant in young ICD patients with a life expectancy of many decades.
The subcutaneous implantable cardioverter-defibrillator (S-ICD), characterized by the extrathoracic position of the lead, was introduced to reduce harm associated with transvenous leads (8). Young patients are overrepresented in S-ICD cohorts because of this presumed benefit, but randomized long-term follow-up data are lacking. Drawbacks of the subcutaneous position are the larger size of the device, which is needed to deliver sufficient energy to meet the defibrillation requirements; the absence of pacing therapy at low energy levels; and the need for 1 or 2 additional incisions depending on the technique used for lead insertion, which might increase the infection risk.
When device-related complications, such as pocket infection or erosion, occur, the treatment options for transvenous and S-ICDs are different. Transvenous ICDs can be implanted on the contralateral side, which by design is not possible with the S-ICD. Patients with a complication of the S-ICD are often explanted and converted to transvenous ICD therapy, which introduces risk of complications associated with transvenous leads (9). Outcomes of patients who have been reimplanted with an S-ICD after a complication have not been reported.
We analyzed implant-related complications in patients with an S-ICD in the largest single-center cohort available to date and report the outcome of strategies focused on continuation of S-ICD therapy after a complication.
We conducted a retrospective single-center cohort study between February 2009 and February 2015. All consecutive patients who received implantation with an S-ICD in our hospital were included, except for patients participating in the ongoing PRAETORIAN trial (A PRospective, rAndomizEd Comparison of subcutaneous and tRansvenous ImplANtable Cardioverter Defibrillator Therapy) (NCT01296022) (10). The need for informed consent was waived by the institutional review board. Implantation of the S-ICD was performed under a combination of local anesthesia, using lidocaine, and conscious sedation in the catheterization laboratory or operating room by 1 implanter (R.K.). From October 2010, S-ICD implantations were performed using the 2-incision technique (11). All patients were routinely evaluated prior to discharge, 2 weeks and 2 months post-implant, and thereafter semi annually in the ICD clinic. Unscheduled visits were documented and used for evaluation.
Complications in this study are defined as complications related to implantation of the S-ICD system such as infection, hematoma, or skin erosion, requiring surgical intervention such as reposition or device extraction and were retrospectively identified from patient’s medical records. Complications that were adequately and definitively managed without surgical intervention are not reported. The time to complication was defined as interval between implant of the S-ICD and the moment of surgical intervention for the complication. Follow-up data were collected to the last follow-up visit.
Continuous data were tested for normality and reported as mean ± SD or medians with corresponding interquartile ranges (IQR) (25% to 75%). For discrete variables, percentages are calculated. Kaplan-Meier estimates for complications were calculated and presented with corresponding 95% confidence intervals (CIs). All statistical analyses were performed using SPSS version 21 software (IBM, Armonk, New York).
A total of 123 patients (56.9% male) who received an S-ICD were included in the current analysis. Table 1 presents the baseline characteristics. The median age at implant was 40 years old (IQR: 26 to 51 years), and 80 (65%) patients had a primary prevention indication. The underlying diagnosis was ischemic cardiomyopathy in 16% and nonischemic cardiomyopathy in 19%, genetic arrhythmia syndromes in 58%, congenital heart disease in 4%, and a family history of sudden cardiac death and nonsustained ventricular tachycardia in another 3%. Of the 123 patients, 92 (75%) received implants using the 2-incision technique. The median follow-up was 27 months (IQR: 9 to 48 months).
The absolute number of patients that encountered a complication related to the implantation of the S-ICD that required surgical intervention was 10. Kaplan-Meier estimates for complication-free survival at 1 and 2 years were 91.8% (95% CI: 86.5% to 97.0%) and 90.6% (95% CI: 84.6% to 96.3%), respectively (Figure 1).
There were a total of 8 infectious complications that required surgical intervention: 5 cases of device infection 4.6% (95% CI: 0.6% to 8.5%) and 3 cases of pocket erosion 3.6% (95% CI: 0.0% to 7.6%). All cases had positive biomarkers for infection (elevated C-reactive protein or white cell count). Additionally there were 6 patients with presumed infections. Five patients had signs of superficial infection, and 1 had a swollen pocket with elevated infection biomarkers. All 6 patients were successfully managed with conservative antibiotic treatment only.
There were 2 acute noninfectious complications requiring intervention: 1 case with defibrillation threshold test (DF-test) failure due to malposition of the device 0.9% (95% CI: 0.0% to 2.7%) and 1 case of lead displacement 0.9% (95% CI: 0.0% to 2.7%). Of the first 31 patients receiving implants with the standard implantation technique, 4 patients (12.9%) suffered a complication versus 6 of the last 92 (6.5%) who received implants using the 2-incision technique, indicating a learning curve with respect to complications. The median duration between implant and diagnosis of the complication was 24 days (IQR: 9 to 185 days) and between implant and surgical intervention 71 days (IQR: 46 to 274 days), as conservative treatment was attempted in most patients first. Table 2 displays the characteristics of patients with a complication. Complications not related to the implant procedure that were excluded from the analysis consisted of 1 pulse generator malfunction, 1 case of oversensing, and 1 fatal case of lead endocarditis of a concomitant pacemaker in a patient with congenital heart disease, who was deemed inoperable. When these complications were included, the rate at 2-year follow-up was 11.8% (95% CI: 5.2% to 18.0%).
Management of infection-related complications
All 5 infected S-ICD systems conferred a local infection and were extracted. The period between extraction and reimplantation of the S-ICD at the same site was bridged for between 6 weeks and 3 months with a wearable cardioverter defibrillator (WCD) (LifeVest, Zoll Medical, Chelmsford, Massachusetts). Patient #5 (Table 2) had a history of endocarditis in the presence of a transvenous device and recurrent skin infections due to eczema and chronic Staphylococcus aureus colonization–associated furunculosis. This patient suffered a local infection of the subcutaneous device approximately 2 months post–implant. The S-ICD was permanently extracted, and the patient was put on a novel drug regimen to prevent arrhythmias, as the consensus was that recurrent infections imposed a greater risk to this patient than interruption of ICD therapy.
The antibiotic regimen consisted of oral flucloxacillin for a median duration of 10 days after extraction of the device, according to local hospital protocol and culture results. Clinical signs of infections and wound healing determined the exact duration of antibiotic treatment. The median duration between termination of antibiotic treatment and reimplantation was 64 days (IQR: 56 to 76 days). There were 3 patients with pocket erosion that required surgical intervention. In all 3 patients, the first step in the management was repositioning of the can in a deeper subcutaneous position under the fibrotic layer of the original pocket. This management proved successful in 1 patient. In the other 2 patients, signs of pocket erosion recurred at 245 and 270 days after repositioning. In both patients, the system was extracted to allow full recovery, and they were fitted with a WCD for a period of 3 months. After this period, both patients underwent successful reimplantation, one in the same subcutaneous position and the other in a deeper sub-serratus anterior muscle (SAM) position. All 3 patients were free from complications up to the last follow-up visit more than 1 year after reimplantation.
Predictors of infection in transvenous systems were assessed with univariate logistic regression models, but age, diabetes, concomitant transvenous device, infection of previous transvenous device, and anticoagulation were found not to be significantly associated with S-ICD infection in this small cohort (data not shown).
Management of acute noninfectious complications
Patient #9 suffered an inappropriate shock approximately 2 months post-implant due to oversensing of myopotentials. Chest radiography revealed migration of the tip of the lead in the caudal direction and the proximal part of the coil toward the pulse generator. The lead was implanted using the 3-incision technique, which requires a distal incision and suturing of the tip of the lead to the fascia. The sleeve to fixate the lead to the xiphoid, which is currently recommended by the manufacturer, had not yet been introduced. The lead was repositioned, which resolved the oversensing.
Patient #10 failed both the periprocedural DF-test and a second DF-test the day after implant at 65 joules in standard and reversed polarity. The failed DF-test was likely due to an inadequate shock vector as both the pulse generator and lead were positioned too anteriorly and not close enough to the chest wall fascia (Figure 2A). Both the lead and the pulse generator were repositioned directly on the fascia, and the pulse generator was moved in the posterior direction. The more posterior position can result in the pulse generator being partly placed in the natural space between the latissimus dorsi and the SAMs, which we do not consider a true submuscular implant of the pulse generator (Figure 2B). After repositioning, 2 DF-tests were successful at 65 J.
Entirely submuscular implantation of the pulse generator
In 3 patients who did not tolerate the subcutaneous position, the pulse generator was reimplanted directly under the SAM. The submuscular implant technique of the pulse generator was successful in all 3 patients. Implants underneath the SAM should be performed in the operating room in the presence a cardiothoracic surgeon because integrity of the long thoracic nerve is critical for shoulder function and damaging it can cause a winged scapula. In this implantation technique, the pulse generator is positioned underneath the sixth and seventh muscle slip (Figures 3A and 3B), and the muscle slips are sutured from lateral to medial (Figures 3C and 3D). Figure 4 presents an anatomic illustration of the implant position.
Our study provides several insights regarding complications of S-ICD therapy. In 9 of the 10 patients with a complication, S-ICD therapy could be continued after intervention. In these 9 patients, conversion to transvenous ICD therapy was an option but not decided. The main reasons to continue S-ICD therapy were patients’ and physicians’ preferences and prior transvenous ICD–related complications such as endocarditis, lead failure, and pocket erosion. In the 10th patient, continuation of ICD therapy was deemed less favorable then a medication-only strategy.
Although the sample size of this cohort was too small to provide a precise estimate of the complications rate, it was similar to the large S-ICD cohort published study by Burke et al. (12), which reported 9.6% complications at 2-year follow-up. No cases of blood-borne infection or endocarditis were observed. Comparison of complication rates to transvenous cohorts are impeded by varying patient characteristics, follow-up durations, and complication definitions. The Danish Pacemaker and ICD registry reported a major complication rate of 5.8% (95% CI: 5.1% to 6.5%) for new implants at 180 days compared with 7.3% (95% CI: 1.7% to 10.8%) in this analysis when all complications requiring intervention were considered (13). The Swedish pacemaker and ICD registry reported 10.1% complications at 1 year compared with 9.4% (95% CI: 3.0% to 13.5%) in this cohort and for infections 3.0% versus 4.6% (95% CI: 0.6% to 8.5%), respectively (14).
S-ICD patients, in general and in this cohort, are younger than the traditional ICD population, with a median age of between 40 and 50 years old and with few comorbidities (15–17). Their presumed more active lifestyle may have caused early post-procedural complications. Previous transvenous ICD studies with younger patients between 29 and 48 years of age reported complication rates ranging between 17% and 27% during follow-up of 2.5 to 5.0 years, which is higher than that in older populations such as SCD-HeFT (14% complications during 3.8 years follow-up) (5,18–21). Many of these complications were related to the transvenous lead failure and dislodgement.
A proportion of this cohort consists of patients who participated in the first-in-human study of the S-ICD. In the first 31 patients, the complication rate was twice that of the next 92 patients. Therefore the complication rate is this cohort may be overestimated because of a learning curve effect and this should be taken into account when it is compared with transvenous cohorts with presumably experienced implanters.
The use of a WCD for a period of 6 weeks to 3 months allows sufficient time for complete recovery of the skin and subcutaneous tissue in cases of erosion or infection. More important, after this bridging period, reimplantation at the original site of implantation was successful in 5 of 6 patients. This demonstrates that conversion to transvenous ICD therapy in case of an S-ICD complication is not necessary, and transvenous leads can be avoided. In a nationwide cohort, we reported preiously that in S-ICD patients with a device infection, 4 of 7 patients were reimplanted with a transvenous ICD (9). Although no arrhythmia episodes were treated by the WCD, we advocate this management for safety and to avoid prolonged hospitalization.
All 3 cases of pocket erosion were initially managed by repositioning the pulse generator in a deeper subcutaneous layer without a bridging period with a WCD, but this strategy proved to be effective in only 1 case. As skin erosion often occurs in the presence of low-grade infection, extraction of the S-ICD system followed by a bridging period with a WCD appears appropriate in these cases.
Failure of DT-testing in a patient (no. 10) with inappropriate positioning of the S-ICD, underlines the importance of positioning the pulse generator directly on the fascia of the chest wall centered in the mid-axillary line. Depending on the size and the exact position of the latissimus dorsi muscle, the pulse generator may also be partly placed underneath this muscle to allow a low defibrillation threshold and enough tissue to protect the skin from the mechanical stress imposed by the pulse generator. In patients who do not tolerate the subcutaneous position of the pulse generator, submuscular implantation can be a successful implantation technique. However, the submuscular implantation is more invasive and painful, it might therefore not be suitable as the default implant technique for de novo implants.
First, it is a retrospective cohort study of 123 patients without (randomized) controls. Patients in this cohort do not represent the typical ICD population as they are younger and have less comorbidity. Patients included in the actively recruiting PREATORIAN trial were excluded but are not likely to introduce significant bias because all patients with an ICD indication without need for brady- or antitachycardia pacing indication are eligible for the trial.
In most patients with a complication, subcutaneous ICD therapy could be continued after intervention, avoiding the need to convert to a transvenous system. The complication rate in this cohort is similar to what has been reported for transvenous ICDs, albeit that the complication rate in this cohort may be overestimated because of a learning curve. Bridging time with a wearable cardioverter-defibrillator allowed re-implantation at the original site of implantation. In patients who do not tolerate subcutaneous placement of the pulse generator, implantation of the pulse generator underneath the SAM can be a viable treatment option.
COMPETENCY IN MEDICAL KNOWLEDGE: The complication rate of S-ICDs is similar to that of transvenous ICD therapy. S-ICD therapy can be continued after a complication such as infection or pocket erosion, avoiding the need to convert to transvenous ICD therapy.
TRANSLATIONAL OUTLOOK: Additional research is needed to evaluate the potential long-term benefits of subcutaneous ICD therapy compared with transvenous ICD therapy.
Dr. Knops has received an institutional research grant and honoraria from Boston Scientific Inc. Dr. de Groot has received grants from St. Jude Medical, Atricure, Medtronic, and ZonMW/NWO. All other authors have reported that they have no relationships relevant to the contents of this paper to disclose.
- Abbreviations and Acronyms
- dilated cardiomyopathy
- defibrillation threshold test
- dipeptidyl aminopeptidase-like protein-6 mutation
- implantable cardioverter-defibrillator
- ischemic cardiomyopathy
- idiopathic ventricular fibrillation
- interquartile range
- long QT-syndrome
- serratus anterior muscle
- subcutaneous implantable cardioverter-defibrillator
- wearable cardioverter-defibrillator
- Received July 21, 2015.
- Revision received September 9, 2015.
- Accepted September 24, 2015.
- American College of Cardiology Foundation
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