Outcomes of video-assisted thoracoscopic surgery for transvenous lead extraction.

INTRODUCTION: To evaluate the outcomes of video-assisted thoracoscopic surgery (VATS) during transvenous lead extractions (TLEs). METHODS AND RESULTS: Ninety-one high-risk patients who underwent TLE in the operating room from January 1, 2015, to March 31, 2017, were included in the study. Of these, 9 patients underwent VATS during TLE. Their clinical characteristics, indications for lead extraction, and complications associated with TLE in the 9 patients who had VATS were compared with those for the 82 patients who did not have VATS. The mean (SD) age of the study patients was 61 (17) years (64.8% were male). The lead dwell time, number of leads extracted, and clinical comorbidities were similar between the 2 groups. Superior vena cava (SVC) tear occurred in 2 of the 9 patients in VATS group and in 1 of the 82 in the non-VATS group (22.2% vs. 1.2%, P = 0.03). Of the 2 patients in the VATS group who had SVC tears, in 1 the tear was visualized immediately and there was no hemodynamic compromise. In the other patient, the SVC tear was within the pericardium; the blood pressure recovered quickly after sternotomy and repair. Both patients had complete lead extraction and survived hospitalization. The patient in the non-VATS group who had an SVC tear had a successful repair but died of postoperative complications. CONCLUSIONS: Utilization of VATS to facilitate TLE is beneficial for early recognition of SVC tear and timely surgical repair in select high-risk patients.

Femoral approach to lead extraction.

Laser and radiofrequency energy-assisted lead extraction has greatly facilitated this complex procedure. Although success rates are high, in some instances alternate methods of extraction are required. In this review, we discuss techniques for femoral extraction of implanted leads and retained fragments. The major tools available, including commonly used snares and delivery tools, are discussed. We briefly describe combined internal jugular and femoral venous extraction approaches, as well as complimentary utilization of more than one technique via the femoral vein. Animated and procedural sequences are included to help the reader visualize the key components of these techniques.

High-affinity IgG antibodies develop naturally in Ig-knockout rats carrying germline human IgH/Igκ/Igλ loci bearing the rat CH region.

Mice transgenic for human Ig loci are an invaluable resource for the production of human Abs. However, such mice often do not yield human mAbs as effectively as conventional mice yield mouse mAbs. Suboptimal efficacy in delivery of human Abs might reflect imperfect interaction between the human membrane IgH chains and the mouse cellular signaling machinery. To obviate this problem, in this study we generated a humanized rat strain (OmniRat) carrying a chimeric human/rat IgH locus (comprising 22 human V(H)s, all human D and J(H) segments in natural configuration linked to the rat C(H) locus) together with fully human IgL loci (12 Vκs linked to Jκ-Cκ and 16 Vλs linked to Jλ-Cλ). The endogenous Ig loci were silenced using designer zinc finger nucleases. Breeding to homozygosity resulted in a novel transgenic rat line exclusively producing chimeric Abs with human idiotypes. B cell recovery was indistinguishable from wild-type animals, and human V(D)J transcripts were highly diverse. Following immunization, the OmniRat strain performed as efficiently as did normal rats in yielding high-affinity serum IgG. mAbs, comprising fully human variable regions with subnanomolar Ag affinity and carrying extensive somatic mutations, are readily obtainable, similarly to conventional mAbs from normal rats.

Outcomes and Complications of Lead Removal: Can We Establish a Risk Stratification Schema for a Collaborative and Effective Approach?

BACKGROUND: Removal of an entire cardiovascular implantable electronic device is associated with morbidity and mortality. We sought to establish a risk classification scheme according to the outcomes of transvenous lead removal in a single center, with the goal of using that scheme to guide electrophysiology lab versus operating room extraction. METHODS: Consecutive patients undergoing transvenous lead removal from January 2001 to October 2012 at Mayo Clinic were retrospectively reviewed. RESULTS: A total of 1,378 leads were removed from 652 (age 64 ± 17 years, M 68%) patients undergoing 702 procedures. Mean (standard deviation) lead age was 57.6 (58.8) months. Forty-four percent of leads required laser-assisted extraction. Lead duration (P < 0.001) and an implantable cardioverter defibrillator (ICD) lead (P < 0.001) were associated with the need for laser extraction and procedure failure (P < 0.0001 and P = 0.02). The major complication rate was 1.9% and was significantly associated with longer lead duration (odds ratio: 1.2, 95% confidence interval: 1.1-1.3; P < 0.001). High-risk patients (with a >10-year-old pacing or a >5-year-old ICD lead) had significantly higher major events than moderate-risk (with pacing lead 1-10 years old or ICD lead 1-5 years old) and low-risk (any lead ≤1-year-old) patients (5.3%, 1.2%, and 0%, respectively; P < 0.001). CONCLUSIONS: Transvenous lead removal is highly successful, with few serious procedural complications. We propose a risk stratification scheme that may categorize patients as low, moderate, and high risk for lead extraction. Such a strategy may guide which extractions are best performed in the operating room.

Outcomes of lead revision for myocardial perforation after cardiac implantable electronic device placement.

INTRODUCTION: Cardiac perforation is an infrequent but potentially life-threatening complication associated with placement of a cardiac implantable electronic device (CIED). The objective of this study was to determine the outcomes of percutaneous lead revision in patients who had lead perforation of the myocardium after CIED placement. METHODS AND RESULTS: We reviewed records of 1,458 patients who underwent CIED lead extraction or repositioning. Of these, 31 (2.1%) had the procedure performed for lead perforation as a complication of CIED placement. Demographic, clinical, and follow-up characteristics of the patients were analyzed. Mean (SD) patient age was 65 (23) years. Cardiac perforation was detected within 24 hours after implantation in 9 patients, within 1 month in 17, and greater than 1 month in 5. Pericardiocentesis was performed with a pigtail drainage catheter in place before the lead revision in 17 patients (55%) who had pericardial effusion, with or without hemodynamic compromise. All culprit leads were successfully managed with percutaneous lead removal (n = 3 [10%]), new lead placement (n = 12 [38%]), or lead repositioning (n = 16 [52%]). Of the 17 patients with pericardiocentesis before the reoperation, none had tamponade develop; in contrast, 3 of the remaining 14 patients had tamponade develop and required urgent pericardiocentesis. All patients survived without requiring open chest surgery. CONCLUSION: Percutaneous removal or repositioning of the perforating lead is feasible and appears effective. Placement of a prophylactic pericardial drain catheter may reduce the incidence of urgent pericardiocentesis during or after a procedure.

Outcome and management of pacemaker-induced superior vena cava syndrome.

BACKGROUND: We aimed to determine the long-term outcomes of percutaneous lead extraction and stent placement in patients with pacemaker-induced superior vena cava (SVC) syndrome. METHODS: The study retrospectively screened patients who underwent lead extraction followed by central vein stent implantation at Mayo Clinic (Rochester, MN, USA), from January 2005 to December 2012, to identify the patients with pacemaker-induced SVC syndrome. Demographic, clinical, and follow-up characteristics of those patients were collected from electronic medical records. RESULTS: Six cases were identified. The mean (standard deviation) age was 56 (15) years (male, 67%). All patients had permanent dual-chamber pacemakers, with a mean 11-year history of pacemaker placement. The entire device system was explanted in five patients; one patient had a 21-year-old pacemaker lead that could not be removed. Eight stents were implanted in six patients: five patients had one stent, one patient had three. A new pacemaker system was reimplanted through the stented vein in five patients. Technical success was achieved in all patients, without any complication. Symptoms rapidly resolved in all patients after stent deployment. The mean follow-up duration was 48 months (range, 10-100 months). Three patients remained symptom free. Reintervention with percutaneous balloon venoplasty was successful in three patients with symptom recurrence. CONCLUSION: Percutaneous stent implantation after lead removal followed by reimplantation of leads is a feasible alternative therapy for pacemaker-induced SVC syndrome, although some cases may require repeat intervention.

B-cell receptors and heavy chain diseases: guilty by association?

Heavy chain diseases (HCDs) are B-cell proliferative disorders characterized by the production of monoclonal, incomplete, immunoglobulin (Ig) heavy chains (HCs) without associated light chains (LCs). These abnormal HCs are produced as a consequence of HC gene alterations in the neoplastic B cells. HC gene alterations will also impact on surface HC, which is part of the B-cell receptor (BCR), a crucial player in lymphocyte activation by antigen. The selective advantage conferred to mutant cells by abnormal BCR without an antigen-binding domain may be explained by activation of ligand-independent signaling, in analogy to what has been shown for mutated oncogenic growth factor receptors. Here we review data obtained from mouse models showing abnormal, constitutive activity of HCD-BCR, and we discuss the possible mechanism involved, namely, aberrant spontaneous self-aggregation. This self-aggregation might occur as a consequence of escape from the chaperone immunoglobulin binding protein (BiP) and from the anti-aggregation effect of LC association. The concept of misfolding-induced signaling elaborated here may extend to other pathologies termed conformational diseases.

Pacemaker lead perforation causing hemopericardium eight years after implantation.

The number of patients with intracardiac devices, including permanent pacemakers and implantable cardioverter-defibrillators is increasing. Lead perforation is a recognized complication which most often occurs during or shortly following pacemaker implantation. Late lead perforation occurring over 30 days after device insertion is a rare, potentially life-threatening complication. We present a case of late lead perforation unmasked greater than eight years after pacemaker implantation by initiation of anticoagulation.

Immunoglobulin aggregation leading to Russell body formation is prevented by the antibody light chain.

Russell bodies (RBs) are intracellular inclusions filled with protein aggregates. In diverse lymphoid disorders these occur as immunoglobulin (Ig) deposits, accumulating in abnormal plasma or Mott cells. In heavy-chain deposition disease truncated antibody heavy-chains (HCs) are found, which bear a resemblance to diverse polypeptides produced in Ig light-chain (LC)-deficient (L(-/-)) mice. In L(-/-) animals, the known functions of LC, providing part of the antigen-binding site of an antibody and securing progression of B-cell development, may not be required. Here, we show a novel function of LC in preventing antibody aggregation. L(-/-) mice produce truncated HC naturally, constant region (C)gamma and Calpha lack C(H)1, and Cmicro is without C(H)1 or C(H)1 and C(H)2. Most plasma cells found in these mice are CD138(+) Mott cells, filled with RBs, formed by aggregation of HCs of different isotypes. The importance of LC in preventing HC aggregation is evident in knock-in mice, expressing Cmicro without C(H)1 and C(H)2, which only develop an abundance of RBs when LC is absent. These results reveal that preventing antibody aggregation is a major function of LC, important for understanding the physiology of heavy-chain deposition disease, and in general recognizing the mechanisms, which initiate protein conformational diseases.

Light chain-deficient mice produce novel multimeric heavy-chain-only IgA by faulty class switching.

Recently, we identified that diverse heavy chain (H-chain)-only IgG is spontaneously produced in light chain (L-chain)-deficient mice (L(-/-) with silenced kappa and lambda loci) despite a block in B cell development. In murine H-chain IgG, the first Cgamma exon, C(H)1, is removed after DNA rearrangement and secreted polypeptides are comparable with camelid-type H-chain IgG. Here we show that L(-/-) mice generate a novel class of H-chain Ig with covalently linked alpha chains, not identified in any other healthy mammal. Surprisingly, diverse H-chain-only IgA can be released from B cells at levels similar to conventional IgA and is found in serum and sometimes in milk and saliva. Surface IgA without L-chain is expressed in B220(+) spleen cells, which exhibited a novel B cell receptor, suggesting that associated conventional differentiation events occur. To facilitate the cellular transport and release of H-chain-only IgA, chaperoning via BiP association seems to be prevented as only alpha chains lacking C(H)1 are released from the cell. This appears to be accomplished by imprecise class-switch recombination (CSR) from Smu into the alpha constant region, which removes all or part of the Calpha1 exon at the genomic level.

Removal of the BiP-retention domain in Cmicro permits surface deposition and developmental progression without L-chain.

Nascent, full length, immunoglobulin (Ig) heavy (H)-chains are post-translationally associated with H-chain-binding protein (BiP or GRP78) in the endoplasmic reticulum (ER). The first constant (C) domain, CH1 of a C gene (Cmu, Cgamma, Calpha), is important for this interaction. The contact is released upon BiP replacement by conventional Ig light (L)-chain (kappa or lambda). Incomplete or mutated H-chains with removed variable (VH) and/or C(H)1 domain, as found in H-chain disease (HCD), can preclude stable BiP interaction. Progression in development after the preB cell stage is dependent on surface expression of IgM when association of a micro H-chain with a L-chain overcomes the retention by BiP. We show that IgM lacking the BiP-binding domain is displayed on the cell surface and elicits a signal that allows developmental progression even without the presence of L-chain. The results are reminiscent of single chain Ig secretion in camelids where developmental processes leading to the generation of fully functional H-chain-only antibodies are not understood. Furthermore, in the mouse the largest secondary lymphoid organ, the spleen, is not required for H-chain-only Ig expression and the CD5 survival signal may be obsolete for cells expressing truncated IgM.

Stroke in patients with cardiovascular implantable electronic device infection undergoing transvenous lead removal.

BACKGROUND: Stroke can be a devastating complication in patients with cardiovascular implantable electronic device (CIED) infection. Paradoxical septic embolism can occur in the presence of device leads and patent foramen ovale (PFO) via embolic dislodgment during transvenous lead removal (TLR). OBJECTIVE: The purpose of this study was to examine stroke and its associated factors in patients undergoing TLR for CIED infection. METHODS: We performed a retrospective analysis of all patients undergoing TLR for CIED infection from January 1, 2000, to July 30, 2017, from all 3 tertiary referral centers at the Mayo Clinic (Rochester, Phoenix, and Jacksonville). The primary outcome was stroke and was further categorized into preprocedural and postprocedural stroke. Associated risk factors were analyzed. RESULTS: A total of 774 patients (mean age 67.6 ± 14.9 years) underwent TLR for CIED infection. The stroke rate in this cohort was 1.9% (95% confidence interval [CI] 1.1%-3.2%). The preprocedural and postprocedural stroke rate was 0.9% (95% CI 0.4%-1.9%) and 1.0% (95% CI 0.4%-2.0%), respectively. PFOs were identified in 46.7% of patients with stroke and in 12.9% of patients without stroke, and were independently associated with stroke (P = .0002). This was especially in patients with right-sided vegetations with right-to-left shunting (odds ratio 6.4; 95% CI 1.3-31.0; P = .022). CONCLUSION: In patients with CIED infection undergoing TLR, the presence of PFO, especially with right-sided vegetation with right-to-left shunting, was associated with an increased risk of stroke. This finding suggests that PFO screening before TLR warrants meticulous attention.

Multispecific Antibody Development Platform Based on Human Heavy Chain Antibodies.

Heavy chain-only antibodies (HCAbs) do not associate with light chains and their VH regions are functional as single domains, forming the smallest active antibody fragment. These VH regions are ideal building blocks for a variety of antibody-based biologics because they tolerate fusion to other molecules and may also be attached in series to construct multispecific antibodies without the need for protein engineering to ensure proper heavy and light chain pairing. Production of human HCAbs has been impeded by the fact that natural human VH regions require light chain association and display poor biophysical characteristics when expressed in the absence of light chains. Here, we present an innovative platform for the rapid development of diverse sets of human HCAbs that have been selected in vivo. Our unique approach combines antibody repertoire analysis with immunization of transgenic rats, called UniRats, that produce chimeric HCAbs with fully human VH domains in response to an antigen challenge. UniRats express HCAbs from large transgenic loci representing the entire productive human heavy chain V(D)J repertoire, mount robust immune responses to a wide array of antigens, exhibit diverse V gene usage and generate large panels of stable, high affinity, antigen-specific molecules.

Heavy-chain-only antibody expression and B-cell development in the mouse.

Antibodies expressed in mice, humans, and most mammals consist of paired heavy (H) and light (L) chains. Cellular release of single H-chains without L-chains is prevented by chaperone association and retention in the endoplasmic reticulum. Consequently, H-chain-only antibodies are absent, except in pathological conditions known as Heavy Chain Disease, where they occur in mutated form. An exception to this is found in the serum of Camelidae. Homodimeric H-chain antibodies in camelids lack the first constant region domain (CH1) of the H-chain but retain an otherwise intact H-chain polypeptide, thus maintaining antigen specificity and effector functions. In this review, we summarize how H-chain antibodies can be expressed in mice, and whether normal developmental processes leading to antibody expression without L-chain are retained.

Strategies to Obtain Diverse and Specific Human Monoclonal Antibodies From Transgenic Animals.

Techniques to obtain large quantities of antigen-specific monoclonal antibodies (mAbs) were first established in the 1970s when Georges Köhler and César Milstein immortalized antibody-producing mouse B-lymphocytes by fusion with myeloma cells (http://www.whatisbiotechnology.org/exhibitions/milstein). Combined with the expression of human antibodies in transgenic animals, this technique allowed upon immunization the generation of highly specific fully human mAbs for therapeutic applications. Apart from being extremely beneficial, mAbs are a huge success commercially. However, despite cell fusion generating many useful mAbs questions have been asked about which types of cells are prone to fuse and whether other methods may identify a wider range of binders. The discovery that expression libraries, using Escherichia coli or yeast, produced different specificities was intriguing and more recently Next-Generation Sequencing has identified wide-ranging usage with highly diverse and unique repertoires. Another strategy is the combination of flow cytometry sorting of antigen-binding B lymphocytes and single-cell reverse transcription polymerase chain reaction followed by reexpression, which has identified many high-affinity mAbs.

Human antibody production in transgenic animals.

Fully human antibodies from transgenic animals account for an increasing number of new therapeutics. After immunization, diverse human monoclonal antibodies of high affinity can be obtained from transgenic rodents, while large animals, such as transchromosomic cattle, have produced respectable amounts of specific human immunoglobulin (Ig) in serum. Several strategies to derive animals expressing human antibody repertoires have been successful. In rodents, gene loci on bacterial artificial chromosomes or yeast artificial chromosomes were integrated by oocyte microinjection or transfection of embryonic stem (ES) cells, while ruminants were derived from manipulated fibroblasts with integrated human chromosome fragments or human artificial chromosomes. In all strains, the endogenous Ig loci have been silenced by gene targeting, either in ES or fibroblast cells, or by zinc finger technology via DNA microinjection; this was essential for optimal production. However, comparisons showed that fully human antibodies were not as efficiently produced as wild-type Ig. This suboptimal performance, with respect to immune response and antibody yield, was attributed to imperfect interaction of the human constant region with endogenous signaling components such as the Igα/ß in mouse, rat or cattle. Significant improvements were obtained when the human V-region genes were linked to the endogenous CH-region, either on large constructs or, separately, by site-specific integration, which could also silence the endogenous Ig locus by gene replacement or inversion. In animals with knocked-out endogenous Ig loci and integrated large IgH loci, containing many human Vs, all D and all J segments linked to endogenous C genes, highly diverse human antibody production similar to normal animals was obtained.

Extraction of superfluous device leads: A comparison with removal of infected leads.

BACKGROUND: Although increasingly more lead extraction was performed for superfluous leads, the extraction of such leads remains controversial. OBJECTIVE: The objective of this study was to determine the outcomes and complications of transvenous extraction of superfluous leads in a single center in the era of laser technology. METHODS: Four hundred eighty transvenous lead extraction procedures performed from January 2001 through October 2012 at Mayo Clinic (Rochester, Minnesota) were retrospectively reviewed. Of these, 123 procedures were performed for superfluous functional or nonfunctional leads. Data were collected from electronic medical records and an institutional database of cardiovascular implantable electronic devices. RESULTS: A total of 167 superfluous leads (mean [SD] lead duration 53 [53] months; median 34 months) were removed during the 123 procedures. Forty-one percent of procedures were for lead malfunction. The procedural complete-success rate was 96.7%. Major complications occurred in 1 patient (0.8%), who had a superior vena cava tear that required thoracotomy. Superfluous leads had been implanted for a shorter period of time than infected leads (mean [SD] 53 [53] vs 81 [59] months; P < .001). The procedural complete-success rate was higher for the removal of superfluous leads than for leads associated with infection (97% vs 92%; P = .05). CONCLUSION: Transvenous extraction of superfluous leads is highly successful, with few procedural complications. Extraction of superfluous leads at the time of device upgrade or lead revision is considered reasonable to avoid the increasing risk of extraction complications with lead aging.

Human antibody expression in transgenic rats: comparison of chimeric IgH loci with human VH, D and JH but bearing different rat C-gene regions.

Expression of human antibody repertoires in transgenic animals has been accomplished by introducing large human Ig loci into mice and, more recently, a chimeric IgH locus into rats. With human VH, D and JH genes linked to the rat C-region antibody expression was significantly increased, similar to wild-type levels not found with fully human constructs. Here we compare four rat-lines containing the same human VH-region (comprising 22 VHs, all Ds and all JHs in natural configuration) but linked to different rat CH-genes and regulatory sequences. The endogenous IgH locus was silenced by zinc-finger nucleases. After breeding, all lines produced exclusively chimeric human H-chain with near normal IgM levels. However, in two lines poor IgG expression and inefficient immune responses were observed, implying that high expression, class-switching and hypermutation are linked to optimal enhancer function provided by the large regulatory region at the 3' end of the IgH locus. Furthermore, exclusion of Cδ and its downstream interval region may assist recombination. Highly diverse IgG and immune responses similar to normal rats were identified in two strains carrying diverse and differently spaced C-genes.

Outcomes and predictors of difficulty with coronary sinus lead removal.

With increasing coronary sinus (CS) pacemaker leads for cardiac resynchronization therapy, the need to remove these leads has risen. The purpose of this study is to describe a single center's experience with CS lead removal and to attempt to identify predictors of difficulty with lead removal and complications. We reviewed all percutaneous endocardial CS lead removals performed at our institution through February 2010. Successful removal with traction alone was considered simple while complex extractions required traction devices and/or laser sheaths. Between December 1996 and February 2010, 125 CS leads were percutaneously removed ≥1 week post-implantation from 115 patients. One attempt at CS lead extraction was unsuccessful. The average duration since implantation for the CS leads was 1.54 years (± .75 years, range 8 days to 8.24 years). The majority of the leads were removed by simple traction (n = 114, 91.2 %). The remainder were removed by femoral approach with snare (n = 3, 2.4 %), locking stylet (n = 2, 1.6 %), or locking stylet and laser sheath (n = 6, 4.8 %). Half of CS leads in place greater than 4 years required complex extraction (n = 7/14, 50 %). CS complications (n = 11 patients, 8.8 %) included CS or tributary thrombosis (n = 7/102, 6.9 %) and CS dissection (n = 4/102, 3.9 %). Major non-CS complications (n = 2 patients, 1.6 %) included a cardiac tear requiring pericardiocentesis and thoracotomy (n = 1, 0.8 %) and subclavian vein tear requiring surgical repair (n = 1, 0.8 %). Minor non-CS complications (n = 9 patients, 7.2 %) included a pneumothorax (n = 1, 0.8 %), hematoma (n = 2, 1.6 %), subclavian vein thrombosis (n = 3, x%), and blood transfusion (n = 5, 4.0 %). A longer duration since implantation and larger lead diameter were associated with complex versus simple removal (p < .0001 and p = .0009 respectively). Percutaneous CS lead removal is successful by simple traction alone in the vast majority of cases. CS leads in place greater than 4 years, however, often require complex extraction. Specific extraction techniques can be implemented when simple traction is unsuccessful without an appreciable increase in complications.