Neointimal fibrotic lead encapsulation - Clinical challenges and demands for implantable cardiac electronic devices

Clinical effectiveness and safety of transvenous lead extraction of very old leads

BACKGROUND

Transvenous lead extraction (TLE) success and safety are heavily influenced by lead dwell time.

OBJECTIVE

In this study, we aim to compare the clinical effectiveness and safety of TLE between young and old leads.

METHODS

We retrospectively identified all TLE procedures at Emory Healthcare from 2007 to 2023. Baseline patients' characteristics and procedural details were collected. The cohort was categorized based on the oldest lead dwell time in each procedure. The very long dwell time (VLDT) group included all procedures with the oldest lead dwell time, ≥15 years, whereas the control group included all procedures with the oldest lead dwell time <15 years. TLE outcomes were compared between the 2 groups.

RESULTS

Of the 1717 TLE procedures, 114 procedures (6.6%) included leads with dwell times ≥15 years. Patients in the VLDT group were older and had a higher number of targeted leads; 57% of TLE in the VLDT group were for infectious indications. Lead extraction procedural and clinical success were significantly lower in the VLDT group compared with the control group (75% vs 95%, 83% vs 97%, P < .001, respectively). There was a trend toward a higher major complications rate in the VLDT group compared with the control group (3.5% vs 1.3%, P = .058).

CONCLUSION

TLE of VLDT leads has a lower procedural and clinical success and a higher complication rate than TLE of leads with a shorter dwell time. These results will allow electrophysiologists to quantify risks and benefits of abandoning leads at the time of lead revisions or upgrades.

Normalization of increasing shocking coil impedance with full output synchronized shock

INTRODUCTION

Impedance is a crucial parameter in cardiovascular implantable electronic devices (CIEDs). Clinically, most CIEDs measure impedance using low voltage sub-threshold measurement (LVSM). Although the LVSM of shock impedance (LVSM-SI) is generally comparable with high voltage shock impedance (HVSI), LVSM-SI might be inaccurate if peri-lead tissue degeneration occurs.

METHODS AND RESULTS

We present a case of elevated LVSM-SI occurring 8 years post-lead implantation, possibly attributed to encapsulation of the right ventricular lead coil. After 0.1 J shock was delivered, a full output synchronized shock was administered to measure HVSI, revealing a normal value. Furthermore, LVSM-SI was normalized and maintained within the normal range during long-term follow-up.

CONCLUSION

Our findings suggest conducting a full-output synchronized shock test to assess HVSI when abnormal LVSM-SI is detected in the remote phase post-ICD implantation, which may be considered to help normalize LVSM shock impedance.

Soft Bioelectronics for Heart Monitoring

Cardiovascular diseases (CVDs) are a predominant global health concern, accounting for over 17.9 million deaths in 2019, representing approximately 32% of all global fatalities. In North America and Europe, over a million adults undergo cardiac surgeries annually. Despite the benefits, such surgeries pose risks and require precise postsurgery monitoring. However, during the postdischarge period, where monitoring infrastructures are limited, continuous monitoring of vital signals is hindered. In this area, the introduction of implantable electronics is altering medical practices by enabling real-time and out-of-hospital monitoring of physiological signals and biological information postsurgery. The multimodal implantable bioelectronic platforms have the capability of continuous heart sensing and stimulation, in both postsurgery and out-of-hospital settings. Furthermore, with the emergence of machine learning algorithms into healthcare devices, next-generation implantables will benefit artificial intelligence (AI) and connectivity with skin-interfaced electronics to provide more precise and user-specific results. This Review outlines recent advancements in implantable bioelectronics and their utilization in cardiovascular health monitoring, highlighting their transformative deployment in sensing and stimulation to the heart toward reaching truly personalized healthcare platforms compatible with the Sustainable Development Goal 3.4 of the WHO 2030 observatory roadmap. This Review also discusses the challenges and future prospects of these devices.

Impact of Immunosuppressive Therapy on Lead Dislodgement After Cardiac Implantable Electronic Device Implantation

BACKGROUNDS

Lead dislodgement is a severe complication in cardiac implantable electronic device (CIED) implantation. Inflammation after CIED implantation results in the development of adhesions between lead and tissues, resulting in the lead becoming fixed in the body. In patients with immunosuppressive therapy, however, adhesion is inhibited by anti-inflammatory effects. However, the association between lead dislodgement and immunosuppressive therapy has not been clarified. The purpose of this study was to investigate the association between lead dislodgement and immunosuppressive therapy.

HYPOTHESIS

We hypothesized that lead dislodgement more frequently occur in patients with immunosuppressive therapy than those without.

METHODS

In total, 651 consecutive patients who underwent CIED implantation or lead addition (age, 76 ± 11 years; and males, 374 [58%], high voltage device, 121 [19%], lead addition 23 [4%]) were retrospectively enrolled. Immunosuppressive therapy was with regular steroids or immunosuppressants. Lead placement was guided by fluoroscopy, and active fixation leads were used. Restraint of the upper limb by chest tape was performed for 1 week after the procedure. Lead dislodgement was defined as a change in lead position and/or lead failure requiring reoperation.

RESULTS

Twenty (3.1%) patients received immunosuppressive therapy. Among these, 15 (2.3%) patients regularly took steroids and 8 (1.2%) took immunosuppressants. Lead dislodgement occurred in 10 (1.5%) patients. Lead dislodgement was more frequent in patients with immunosuppressive therapy than in those without (3 [15%] vs. 7 [1%], p = 0.003).

CONCLUSION

In patients with CIED implantation or lead addition, lead dislodgement is more frequent in patients with immunosuppressive therapy than in those without.

Next-Generation Cardiac Interfacing Technologies Using Nanomaterial-Based Soft Bioelectronics

Cardiac interfacing devices are essential components for the management of cardiovascular diseases, particularly in terms of electrophysiological monitoring and implementation of therapies. However, conventional cardiac devices are typically composed of rigid and bulky materials and thus pose significant challenges for effective long-term interfacing with the curvilinear surface of a dynamically beating heart. In this regard, the recent development of intrinsically soft bioelectronic devices using nanocomposites, which are fabricated by blending conductive nanofillers in polymeric and elastomeric matrices, has shown great promise. The intrinsically soft bioelectronics not only endure the dynamic beating motion of the heart and maintain stable performance but also enable conformal, reliable, and large-area interfacing with the target cardiac tissue, allowing for high-quality electrophysiological mapping, feedback electrical stimulations, and even mechanical assistance. Here, we explore next-generation cardiac interfacing strategies based on soft bioelectronic devices that utilize elastic conductive nanocomposites. We first discuss the conventional cardiac devices used to manage cardiovascular diseases and explain their undesired limitations. Then, we introduce intrinsically soft polymeric materials and mechanical restraint devices utilizing soft polymeric materials. After the discussion of the fabrication and functionalization of conductive nanomaterials, the introduction of intrinsically soft bioelectronics using nanocomposites and their application to cardiac monitoring and feedback therapy follow. Finally, comments on the future prospects of soft bioelectronics for cardiac interfacing technologies are discussed.

Associated factors and outcomes of crossover from a laser sheath to a bidirectional rotational mechanical sheath during transvenous lead extraction

Background

During transvenous lead extraction (TLE), a GlideLight laser sheath (Philips) cannot always be advanced over the lead, and crossover to the Evolution system (i.e., an Evolution RL sheath or Evolution Shortie RL sheath [Cook Medical]) is required. We aimed to determine the associated factors and outcomes of such device crossover.

Methods

This observational study included 112 patients who underwent TLE. The patients were divided into crossover and non-crossover groups. Outcomes and associated factors of crossover were evaluated.

Results

Overall, 57 (50.9%) patients required crossover to the Evolution system (crossover group), whereas 55 (49.1%) patients did not require crossover (non-crossover group). Clinical success rate was similar between the two groups (98.3% vs. 100%; p = 1.00). No major intraprocedural complications related to powered sheaths occurred. Multivariate logistic regression analysis results showed that dwell time of the oldest extracted lead (per year) (odds ratio [OR]: 1.18, 95% confidence interval [CI]: 1.02-1.36; p = .026), number of leads extracted per procedure (OR: 7.23, 95% CI: 1.74-29.99; p = .007), and use of a femoral approach (OR: 21.09, 95% CI: 2.33-190.67; p = .007) were associated factors of crossover. The cutoff for crossover was 7.7 years from the implant (sensitivity 90.5%, specificity 64.9%, area under the curve 0.80).

Conclusions

Both groups showed a high rate of clinical success. Switching to the Evolution system may facilitate a safe and effective TLE when a laser sheath does not advance despite laser activation.

Procedural outcome & risk prediction in young patients undergoing transvenous lead extraction-a GALLERY subgroup analysis

Background

The prevalence of young patients with cardiac implantable electronic devices (CIED) is steadily increasing, accompanied by a rise in the occurrence of complications related to CIEDs. Consequently, transvenous lead extraction (TLE) has become a crucial treatment approach for such individuals.

Objective

The purpose of this study was to examine the characteristics and procedural outcomes of young patients who undergo TLE, with a specific focus on identifying independent risk factors associated with adverse events.

Methods

All patients in the GALLERY (GermAn Laser Lead Extraction RegistrY) were categorized into two groups based on their age at the time of enrollment: 45 years or younger, and over 45 years. A subgroup analysis was conducted specifically for the younger population. In this analysis, predictor variables for all-cause mortality, procedural complications, and procedural failure were evaluated using multivariable analyses.

Results

We identified 160 patients aged 45 years or younger with a mean age of 35.3 ± 7.6 years and 42.5% (n = 68) female patients. Leading extraction indication was lead dysfunction in 51.3% of cases, followed by local infections in 20.6% and systemic infections in 16.9%. The most common device to be extracted were implantable cardioverter-defibrillators (ICD) with 52.5%. Mean number of leads per patient was 2.2 ± 1.0. Median age of the oldest indwelling lead was 91.5 [54.75-137.5] months. Overall complication rate was 3.8% with 1.9% minor and 1.9% major complications. Complete procedural success was achieved in 90.6% of cases. Clinical procedural success rate was 98.1%. Procedure-related mortality was 0.0%. The all-cause in-hospital mortality rate was 2.5%, with septic shock identified as the primary cause of mortality. Multivariable analysis revealed CKD (OR: 19.0; 95% CI: 1.84-194.9; p = 0.018) and systemic infection (OR: 12.7; 95% CI: 1.14-142.8; p = 0.039) as independent predictor for all-cause mortality. Lead age ≥ 10 years (OR: 14.58, 95% CI: 1.36-156.2; p = 0.027) was identified as sole independent risk factor for procedural complication.

Conclusion

TLE in young patients is safe and effective with a procedure-related mortality rate of 0.0%. CKD and systemic infection are predictors for all-cause mortality, whereas lead age ≥ 10 years was identified as independent risk factor for procedural complications in young patients undergoing TLE.

Exploring the Overlooked Roles and Mechanisms of Fibroblasts in the Foreign Body Response

Significance: Foreign body response (FBR), wherein a fibrotic capsule forms around an implanted structure, is a common surgical complication that often leads to pain, discomfort, and eventual revision surgeries. Although believed to have some mechanistic overlap with normal wound healing, much remains to be discovered about the specific mechanism by which this occurs. Recent Advances: Current understanding of FBR has focused on the roles of the immune system and the biomaterial, both major contributors to FBR. However, another key player, the fibroblast, is often overlooked. This review summarizes key contributors of FBR, focusing on the roles of fibroblasts. As much remains to be discovered about fibroblasts' specific roles in FBR, we draw on current knowledge of fibroblast subpopulations and functions during wound healing. We also provide an overview on candidate biomaterials and signaling pathways involved in FBR. Critical Issues and Future Directions: While the global implantable medical devices market is considerable and continues to appreciate in value, FBR remains one of the most common surgical implant complications. In parallel with the continued development of candidate biomaterials, further exploration of potential fibroblast subpopulations at a transcriptional level would provide key insights into further understanding the underlying mechanisms by which fibrous encapsulation occurs, and unveil novel directions for antifibrotic and regenerative therapies in the future.

Reduced fibrous capsule elastic fibers from biologic ECM-enveloped CIEDs in minipigs, supported with a novel compression mechanics model

BACKGROUND

Fibrous capsules (Fb) in response to cardiovascular implantable electronic devices (CIEDs), including a pacemaker (P) system, can produce patient discomfort and difficulties in revision surgery due partially to their increased compressive strength, previously linked to elevated tissue fibers.

OBJECTIVE

A preliminary study to quantify structural proteins, determine if biologic extracellular matrix-enveloped CIEDs (PECM) caused differential Fb properties, and to implement a realistic mechanical model.

METHODS

Retrieved Fb (-P and -PECM) from minipigs were subjected to biomechanical (shear oscillation and uniaxial compression) and histological (collagen I and elastin) analyses.

RESULTS

Fb-PECM showed significant decreases compared to Fb-P in: low strain-loss modulus (390 vs. 541 Pa) across angular frequencies, high strain-compressive elastic modulus (1043 vs. 2042 kPa), and elastic fiber content (1.92 vs. 3.15 μg/mg tissue). Decreases in elastin were particularly noted closer to the implant's surface (Fb-PECM = 71% vs. Fb-P = 143% relative to dermal elastin at mid-tangential sections) and verified with a solid mechanics hyperelasticity with direction-dependent fiber viscoelasticity compression simulation (r2 ≥ 98.9%).

CONCLUSIONS

The biologic envelope composed of decellularized porcine small intestine submucosa ECM for CIEDs promoted fibrous tissues with less elastic fibers. Novel compression modeling analyses directly correlated this singular reduction to more desirable subcutaneous tissue mechanics.

Practical Approaches to Transvenous Lead Extraction Procedures-Clinical Case Series

Transvenous lead extraction (TLE) is regarded as the first-line strategy for the management of complications associated with cardiac implantable electronic devices (CIEDs), when lead removal is mandatory. The decision to perform a lead extraction should take into consideration not only the strength of the clinical indication for the procedure but also many other factors such as risks versus benefits, extractor and team experience, and even patient preference. TLE is a procedure with a possible high risk of complications. In this paper, we present three clinical cases of patients who presented different indications of TLE and explain how the procedures were successfully performed. In the first clinical case, TLE was necessary because of device extravasation and suspicion of CIED pocket infection. In the second clinical case, TLE was necessary because occlusion of the left subclavian vein was found when an upgrade to cardiac resynchronization therapy was performed. In the last clinical case, TLE was necessary in order to remove magnetic resonance (MR) non-conditional leads, so the patient could undergo an MRI examination for the management of a brain tumor.

Advanced strategies to thwart foreign body response to implantable devices

Mitigating the foreign body response (FBR) to implantable medical devices (IMDs) is critical for successful long-term clinical deployment. The FBR is an inevitable immunological reaction to IMDs, resulting in inflammation and subsequent fibrotic encapsulation. Excessive fibrosis may impair IMDs function, eventually necessitating retrieval or replacement for continued therapy. Therefore, understanding the implant design parameters and their degree of influence on FBR is pivotal to effective and long lasting IMDs. This review gives an overview of FBR as well as anti-FBR strategies. Furthermore, we highlight recent advances in biomimetic approaches to resist FBR, focusing on their characteristics and potential biomedical applications.

Embolized fibrin sheath material presenting as intraluminal calcifications within the pulmonary arteries on CT

Fibrin sheath formation is a well-described sequela of an indwelling central venous catheter. Fibrin sheaths may also develop around other foreign bodies within the venous system. We describe a case of fibrin sheath formation within the left brachiocephalic vein secondary to automatic implantable cardioverter-defibrillator (AICD) leads with subsequent embolization of sheath material presenting as calcifications within the pulmonary vasculature on computed tomography (CT). Most of the relevant literature focuses on catheter-related sheath formation and associated complications while reports on fibrin sheaths from other foreign bodies are sparse. We advise that radiologists who encounter intraluminal calcifications within the pulmonary arteries on CT should consider the possibility of a fibrin sheath as the source and search for its remnants in the central venous system for confirmation.

Successful avoidance of superior vena cava injury during transvenous lead extraction using a tandem femoral-superior approach

BACKGROUND

Transvenous pacemaker and defibrillator lead extraction is a higher risk procedure with variation in preferred technique. A frequently fatal complication of this procedure is perforation of the superior vena cava. We have developed a tandem femoral-superior technique that incorporates snaring of targeted leads from a femoral approach combined with use of a rotational cutting sheath advanced over the lead from the subclavian vein.

OBJECTIVE

We sought to evaluate the safety and efficacy of a tandem femoral-superior approach to lead extraction.

METHODS

Consecutive patients undergoing transvenous extraction of at least 1 pacemaker or defibrillator lead with implant duration ≥1 year in which a tandem femoral-superior technique was used as the initial extraction strategy were included. The registry spanned 2010-2018 and consisted of procedures performed by a single primary operator.

RESULTS

A total of 131 patients were included. A total of 267 leads with a mean implant duration of 9.8 years, including 90 defibrillator leads (33.7%), were targeted for extraction. No superior vena cava perforation or other vascular damage occurred. Clinical procedural success was achieved in 96.2% of cases. There were 5 major complications (3.8% of patients), with 3 being pericardial effusion requiring intervention. There were no deaths.

CONCLUSION

A tandem femoral-superior approach to lead extraction effectively eliminated superior vena cava injury. This is a safe and effective technique for transvenous lead extraction.

Prevalence and Predisposing Factors of Non-infectious Cardiac Implantable Electronic Device Lead Masses as Incidental Finding During Transoesophageal Echocardiography: A Retrospective Cohort Study

Objectives

In this study, we assessed the prevalence and predisposing factors of non-infectious CIED lead masses as incidental finding during transoesophageal echocardiography (TOE).

Methods

In a retrospective single centre study, we analysed TOE examinations performed for indications other than infectious endocarditis in 141 patients with CIED. Patients with non-suspicious leads and those with incidental non-infectious lead masses were compared with respect to clinical characteristics, anticoagulation, indication for TOE, and CIED lead characteristics. The odds ratios for non-infectious CIED lead masses were calculated.

Results

Non-infectious CIED lead masses were detected in 39 (27.6%) of the 141 patients. They were more often identified on ICD and CRT-D leads compared to pacemaker and CRT-P leads [OR 2.77 (95% CI 1.29–5.95), p = 0.008]. The lifespan of the CIEDs from the first implantation to the index TOE did not differ between both groups. Incidental CIED lead masses were more prevalent in patients who received their device for primary prevention of sudden cardiac death (43.2%) and for resynchronisation (63.6%) but were less prevalent in patients with oral anticoagulation [OR.33 (95% CI.003–1.003), p = 0.048].

Conclusion

Incidental non-infectious CIED lead masses were frequently found in TOE, with highest prevalence in ICD and CRT-D devices implanted for patients with dilated cardiomyopathy. Patients with therapeutic anticoagulation had significantly lower prevalence of CIED lead masses than those without.

Effect of Microgroove Structure in PDMS-Based Silicone Implants on Biocompatibility

Capsule and capsule contracture around implants are important concerns in a clinic. The physical topology of the material surface regulates the formation of the capsule, but the specific regulatory mechanism is unclear. In this study, four types of silicone implant materials with different microgroove structures (groove depths of 10 and 50 μm and widths of 50 and 200 μm) were constructed using lithography to form different gradient surface topologies. Mass spectrometry, Cell Counting Kit-8, 5-ethynyl-2′-deoxycytidine (EdU), enzyme-linked immunosorbent assay, western blot, immunofluorescence, and immunohistochemistry were used to explore the changes in protein adsorption, cell adhesion, cell proliferation, and collagen deposition on the surface of the materials. At the same time, RNA-seq was used to detect transcriptome differences caused by different structures. Furthermore, collagen deposition and capsule formation were observed in the rats. The groove structure was observed to significantly increase the surface roughness of the material. The deeper groove and the narrower width of the polydimethylsiloxane would increase the surface roughness of the material and the surface water contact angle but reduce the total amount of adsorbed protein in the first two hours. In vitro cell experiments revealed that microtopology affected cell proliferation and adhesion and regulated collagen secretion. Further analysis indicated the deeper and narrower groove (group 50–50) on the surface of the material caused more evident collagen deposition around the material, forming a thicker envelope. Surface roughness of the material was thus related to collagen deposition and envelope thickness. The thickness of the envelope tissue around smooth materials does not exceed that of the materials with surface roughness. In conclusion, the narrower and deeper grooves in the micron range exhibited poor histocompatibility and led to formation of thicker envelopes around the materials. The appropriate grooves can reduce envelope thickness.

Tissues attached to retrieved leadless pacemakers: Histopathological evaluation of tissue composition in relation to implantation time and complications

BACKGROUND

Leadless pacemakers (LPs) have proven safe and effective, but device revisions remain necessary. Either replacing the LP or implanting a new adjacent LP is feasible. Replacement seems more appealing, but encapsulation and tissue adhesions may hamper the safety and efficacy of LP retrieval.

OBJECTIVE

We determined the incidence and cellular characteristics of tissue adherent to retrieved LPs and the potential implications for end-of-life strategy.

METHODS

All 15 consecutive successful Nanostim LP retrievals in a tertiary center were included. We assessed the histopathology of adherent tissue and obtained clinical characteristics.

RESULTS

Adherent tissue was present in 14 of 15 retrievals (93%; median implantation duration 36 months; range 0-96 months). The tissue consisted of fibrosis (n = 2), fibrosis and thrombus (n = 9), or thrombus only (n = 3). In short-term retrievals (<1 year), mostly fresh thrombi without fibrosis were seen. In later retrievals, the tissue consisted of fibrosis often with organizing or lytic thrombi. Fibrosis showed different stages of organization, notably early fibrocellular and later fibrosclerotic tissue. Inflammatory cells were seen (n = 4) without signs of infection. Tricuspid valve material was retrieved in 1 patient after 36 months, resulting in increased tricuspid regurgitation.

CONCLUSION

Our results suggest that fibrosis and thrombus adherent to LPs are common and encapsulate the LP as seen in transvenous pacemakers. LPs may adhere to the tricuspid valve or subvalvular apparatus affecting retrieval safety. The end-of-life strategy should be optimized by incorporating risk stratification for excessive fibrotic encapsulation and adhesions.

Implant Fibrosis and the Underappreciated Role of Myofibroblasts in the Foreign Body Reaction

Body implants and implantable medical devices have dramatically improved and prolonged the life of countless patients. However, our body repair mechanisms have evolved to isolate, reject, or destroy any object that is recognized as foreign to the organism and inevitably mounts a foreign body reaction (FBR). Depending on its severity and chronicity, the FBR can impair implant performance or create severe clinical complications that will require surgical removal and/or replacement of the faulty device. The number of review articles discussing the FBR seems to be proportional to the number of different implant materials and clinical applications and one wonders, what else is there to tell? We will here take the position of a fibrosis researcher (which, coincidentally, we are) to elaborate similarities and differences between the FBR, normal wound healing, and chronic healing conditions that result in the development of peri-implant fibrosis. After giving credit to macrophages in the inflammatory phase of the FBR, we will mainly focus on the activation of fibroblastic cells into matrix-producing and highly contractile myofibroblasts. While fibrosis has been discussed to be a consequence of the disturbed and chronic inflammatory milieu in the FBR, direct activation of myofibroblasts at the implant surface is less commonly considered. Thus, we will provide a perspective how physical properties of the implant surface control myofibroblast actions and accumulation of stiff scar tissue. Because formation of scar tissue at the surface and around implant materials is a major reason for device failure and extraction surgeries, providing implant surfaces with myofibroblast-suppressing features is a first step to enhance implant acceptance and functional lifetime. Alternative therapeutic targets are elements of the myofibroblast mechanotransduction and contractile machinery and we will end with a brief overview on such targets that are considered for the treatment of other organ fibroses.

A rare cause of platypnea-orthodeoxia syndrome in a young female due to persistent left superior vena cava

Platypnea-Orthodeoxia syndrome (POS) is a rare clinical syndrome characterized by shortness of breath in the upright position that is relieved with supine positioning. We present a rare case of persistent left superior vena cava (PLSVC) draining into the left atrium causing a right-to-left shunt and subsequent POS. A 30-year-old female with a past medical history of hypertrophic cardiomyopathy, congenital Long QT syndrome and a left-sided dual chamber implantable cardioverter-defibrillator (ICD) presented with dyspnea and lightheadedness. Prior to presentation, the patient underwent a left-sided ICD extraction due to ICD lead infection and re-implantation from the right side through the cephalic vein. After further investigation, it was concluded that the PLSVC resulted in a physiological right-to-left shunting causing POS, with resolution of her symptoms after surgical ligation. To our knowledge, this is the first case report of PLSVC presenting with POS without anatomical intracardiac shunts following iatrogenic right superior vena cava (RSVC) obstruction.

Polymer-free corticosteroid dimer implants for controlled and sustained drug delivery

Polymeric drug carriers are widely used for providing temporal and/or spatial control of drug delivery, with corticosteroids being one class of drugs that have benefitted from their use for the treatment of inflammatory-mediated conditions. However, these polymer-based systems often have limited drug-loading capacity, suboptimal release kinetics, and/or promote adverse inflammatory responses. This manuscript investigates and describes a strategy for achieving controlled delivery of corticosteroids, based on a discovery that low molecular weight corticosteroid dimers can be processed into drug delivery implant materials using a broad range of established fabrication methods, without the use of polymers or excipients. These implants undergo surface erosion, achieving tightly controlled and reproducible drug release kinetics in vitro. As an example, when used as ocular implants in rats, a dexamethasone dimer implant is shown to effectively inhibit inflammation induced by lipopolysaccharide. In a rabbit model, dexamethasone dimer intravitreal implants demonstrate predictable pharmacokinetics and significantly extend drug release duration and efficacy (>6 months) compared to a leading commercial polymeric dexamethasone-releasing implant.

Long-term evaluation of sensing variability of a floating atrial dipole in a single‑lead defibrillator: The mechanistic basis of long-term stability of amplified atrial electrogram

BACKGROUND

A single‑lead implantable cardioverter-defibrillator (ICD) with a floating atrial dipole has been developed to enhance the diagnostic capability of atrial arrhythmias and to facilitate adjudication of arrhythmic events without the additional effort required for atrial lead insertion. However, there have been concerns about the long-term reliability of atrial sensing.

METHODS

We enrolled patients with the single-chamber ICD with atrial-sensing electrodes from 4 tertiary university hospitals in Korea. Minimal, maximal, and mean P wave amplitudes were collected at 3-6 months, 6-12 months, and 12-24 months after implantation. The difference between the minimal and maximal sensing amplitudes was calculated as an indicator of the variability of atrial sensing, while the atrial sensing stability was assessed using the mean amplitude.

RESULTS

A total of 86 patients were included for analysis. The variability of atrial sensing amplitudes significantly decreased at 12-24 months compared to 3-6 months (p = 0.01), while mean atrial amplitudes were stable throughout the mean follow-up duration of 17.4 months. Nine patients (10.5%) experienced inappropriate ICD therapy mostly due to misclassification of supraventricular tachycardia.

CONCLUSIONS

Under the hypothesis that sensing stability can be guaranteed as the variability decreases with time, we suggest that the concern about long-term sensing stability of a floating dipole can be abated with an ICD that has been implanted for over 2 years.

Morphometric Characterization of Human Coronary Veins and Subvenous Epicardial Adipose Tissue-Implications for Cardiac Resynchronization Therapy Leads

Subvenous epicardial fat tissue (SEAT), which acts as an electrical insulation, and the venous diameter (VD) both constitute histomorphological challenges for optimal application and lead design in cardiac synchronization therapy (CRT). In this study, we characterized the morphology of human coronary veins to improve the technical design of future CRT systems and to optimize the application of CRT leads. We retrospectively analyzed data from cardiac computed tomography (CT) of 53 patients and did studies of 14 human hearts using the postmortem freeze section technique and micro CT. Morphometric parameters (tributary distances, offspring angles, luminal VD, and SEAT thickness) were assessed. The left posterior ventricular vein (VVSP) had a mean proximal VD of 4.0 ± 1.4 mm, the left marginal vein (VMS) of 3.2 ± 1.5 mm and the anterior interventricular vein (VIA) of 3.9 ± 1.3 mm. More distally (5 cm), VDs decreased to 2.4 ± 0.6 mm, 2.3 ± 0.7 mm, and 2.4 ± 0.6 mm, respectively. In their proximal portions (15 mm), veins possessed mean SEAT thicknesses of 3.2 ± 2.4 (VVSP), 3.4 ± 2.4 mm (VMS), and 4.2 ± 2.8 mm (VIA), respectively. More distally (20-70 mm), mean SEAT thicknesses decreased to alternating low levels of 1.3 ± 1.1 mm (VVSP), 1.7 ± 1.1 mm (VMS), and 4.3 ± 2.6 mm (VIA), respectively. In contrast to the VD, SEAT thicknesses alternated along the further distal vein course and did not display a continuous decrease. Besides the CRT responsiveness of different areas of the LV myocardium, SEAT is a relevant electrophysiological factor in CRT, potentially interfering with sensing and pacing. A sufficient VD is crucial for successful CRT lead placement. Measurements revealed a trend toward greater SEAT thickness for the VIA compared to VVSP and VMS, suggesting a superior signal-to-noise-ratio in VVSP and VMS.

A Rare Entity-Percutaneous Lead Extraction in a Very Late Onset Pacemaker Endocarditis: Case Report and Review of Literature

The number of infections related to cardiac implantable electronic devices (CIEDs) has increased as the number of devices implanted around the world has grown exponentially in recent years. CIED complications can sometimes be difficult to diagnose and manage, as in the case of lead-related infective endocarditis. We present the case of a 48-year-old male diagnosed with Staphylococcus aureus device-related infective endocarditis, 12 years after the implant of a single chamber pacemaker. A recent history of the patient includes two urinary catheterizations due to obstructive uropathy in the context of a prostatic adenoma, 2 months previously, both without antibiotic prophylaxis; no other possible entry sites were found and no history of other invasive procedures. After initiation of antibiotic therapy according to antibiotic susceptibility testing, we decided to remove the right ventricular passive fixation lead along with the vegetation and pacemaker generator; because of severe lead adhesions in the costoclavicular region, and especially in the right ventricle, we needed mechanical sheaths to remove the abundant fibrous tissue that encompassed the lead. After a difficult, but successful, lead extraction along with a large vegetation and 6 weeks' antibiotic therapy, the clinical and biological evolution was favorable, without reappearance of symptoms. While very late lead endocarditis is a rarity, late lead-related infective endocarditis (more than 12 months elapsed since implant) is not an exception; this is why we find that endocarditis prophylaxis should be reconsidered in certain patient categories, our patient being proof that procedures with neglectable endocarditis risk according to the guidelines can lead to bacterial endocarditis.

Quantitative and Qualitative Assessment of Adhesive Thrombo-Fibrotic Lead Encapsulations (TFLE) of Pacemaker and ICD Leads in Arrhythmia Patients-A Post Mortem Study

The demand for cardiac implantable electronic devices for arrhythmia therapy is still unabated and rising. Despite onward optimizations, lead-related problems such as infections or fractures often necessitate lead extraction. Due to adhesive thrombo-fibrotic lead encapsulations (TFLE) transvenous lead extraction is challenging and risky. However, knowledge on TFLEs and possible correlations with technical lead parameters and dwelling time (DT) were hitherto insufficiently studied. Therefore, we analyzed TFLEs of 62 lead from 35 body donor corpses to gain information for a potential lead design optimization. We examined both TFLE topography on the basis on anatomical landmarks and histo-morphological TFLE characteristics by means of histological paraffin sections and scanning electron microscopy of decellularized samples. The macroscopic analysis revealed that all leads were affected by TFLEs, mainly in the lead bearing veins. Half (47.2%) of the right-ventricular leads possessed adhesions to the tricuspid valve. On average, 49.9 ± 21.8% of the intravascular lead length was covered by TFLE of which 82.8 ± 16.2% were adhesive wall bindings (WB). The discrete TFLEs with at least one WB portion had a mean length of 95.0 ± 64.3 mm and a maximum of 200 mm. Neither sex, DT nor certain technical lead parameters showed distinct tendencies to promote or prevent TFLE. TFLE formation seems to start early in the first 1-2 weeks after implantation. The degree of fibrotization of the TFLE, starting with a thrombus, was reflected by the amount of compacted collagenous fibers and likewise largely independent from DT. TFLE thickness often reached several hundred micrometers. Calcifications were occasionally seen and appeared irregularly along the TFLE sheath. Leadless pacemaker systems have the advantage to overcome the problem with TFLEs but hold their own specific risks and limitations which are not fully known yet.

Histological properties of oscillating intracardiac masses associated with cardiac implantable electric devices

Background

There have been a few cases of echogenic cardiac implantable electric device (CIED) lead‐associated oscillating intracardiac masses (ICMs) in leads imaged by echocardiography. The histological properties of ICMs could help clarify the etiological diagnosis. Although there is extensive literature on mass size, the histological properties of such masses have not been characterized. The aim of this research was to clarify the histological features of oscillating ICMs in CIED patients.

Methods

Preoperative echocardiography was performed in all candidates for CIED removal. In the patients with ICMs, specimens were obtained by 3 methods: direct tissue collection during open‐heart surgery; tissue collection together with the CIED lead during transvenous extraction; and tissue collection by catheter vacuum during transvenous CIED removal. A standard histopathological examination of ICM tissue was performed.

Results

A total of 106 patients underwent lead removal in our institute (April 2009‐March 2018); 14 patients had an ICM (13.2%), and 7 specimens were obtained in patients with CIED lead‐related ICM. Following histological examination, 2 types of ICM were identified: one mainly composed of thickened endocardium (EN type; 3 patients), and the other mainly an aggregate of inflammatory cells as a neutrophil cell (NC type; 4 patients).

Conclusions

Two histological types of intracardiac masses, including a thickened endocardium type and a neutrophil cell type, were identified. These classifications might help make an accurate histological diagnosis of lead‐associated intracardiac masses.

High-voltage impedance rise; mechanism and management in patients with transvenous implantable cardioverter-defibrillators: a case series

Background

We describe a case series of patients for a gradual rise in daily, low-voltage sub-threshold measurement (LVSM) of shock (high-voltage, HV) impedance in a group of patients with Boston Scientific implantable cardioverter-defibrillators (ICDs) and investigate the cause of the abnormality.

Case summary

Six patients presented with a gradual rise in HV impedance above normal range (132.5 ± 20.8 Ω). Patients were young with a mean age of 29 ± 11 years, four patients had hypertrophic cardiomyopathy, one left ventricular non-compaction, and one long QT. All lead designs were silicon body with GORE polytetrafluoroethylene (ePTFE) coated coils, and a lower true shock impedance (TSI) was seen in all cases with full output synchronized shock. We compared the rate of HV impedance rise with our historical cohort of Boston ICDs using an unpaired t-test. The change in impedance per month was significantly higher amongst our six patients when compared with our cohort of Boston Scientific ICDs (3.2 ± 1.9 Ω/month vs. 0.0008 ± 0.005 Ω/month, P < 0.001). Patients were individually investigated and management discussed in a dedicated device multi-disciplinary team meeting (MDT).

Discussion

There are distinct differences between TSI and LVSM. The TSI is derived from a full output shock, whilst LVSM is calculated from a small current output. These cases highlight the inaccuracies of the LVSM measurement. The gradual rise in LVSM is significantly higher than the value for TSI in these patients we propose the most likely mechanism is encapsulation fibrosis surrounding the right ventricular shock coil. Management for these patients requires vigorous testing to rule out electrical failure, and replacement maybe necessary.

Tackling the Concept of Symbiotic Implantable Medical Devices with Nanobiotechnologies

This review takes an approach to implanted medical devices that considers whether the intention of the implanted device is to have any communication of energy or materials with the body. The first part describes some specific examples of three different classes of implants, analyzed with regards to the type of signal sent to cells. Through several examples, the authors describe that a one way signaling to the body leads to encapsulation or degradation. In most cases, those phenomena do not lead to major problems. However, encapsulation or degradation are critical for new kinds of medical devices capable of duplex communication, which are defined in this review as symbiotic devices. The concept the authors propose is that implanted medical devices that need to be symbiotic with the body also need to be designed with an intended duplex communication of energy and materials with the body. This extends the definition of a biocompatible system to one that requires stable exchange of materials between the implanted device and the body. Having this novel concept in mind will guide research in a new field between medical implant and regenerative medicine to create actual symbiotic devices.