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Concept: Artificial pacemaker

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BACKGROUND: The purpose of this study was to evaluate the feasibility of the magnetic resonance (MR) conditional pacemaker (PM) system (Evia SR-T and DR-T with Safio S leads) under MR conditions. METHODS: Patients with standard PM indications and Evia PM were eligible for enrollment in this single center prospective non-randomized pilot study. Patients underwent MR of the brain and lower lumbar spine at 1.5 Tesla. Atrial (RA) und ventricular (RV) lead parameters (sensing, pacing threshold [PTH], pacing impedance) were assessed immediately before (baseline follow-up [FU]) and immediately after MRI (1st FU), after 1 month (2nd FU) and 3 months (3rd FU). The effect of MR on serious adverse device effect (SADE) free-rate, on atrial and ventricular sensing (AS/VS; mV) and atrial (RA) and ventricular (RV) pacing thresholds (PTH; V/0.4 ms) were investigated between baseline and 2nd FU. Continuous variables are expressed as mean +/- SD and were compared using paired Student’s t-test. A p < 0.05 was considered significant. RESULTS: Thirty-one patients were enrolled. One patient had to be excluded because of an enrollment violation. Therefore, data of 30 patients (female 12 [40%], age 73 +/- 12 years, dual chamber PM 15 [50%]) were included in this analysis. No MR related SADE occurred. Lead measurements were not statistically different between the baseline FU and the 2nd FU (AS/VS at baseline 3.2 +/- 2.1/15.0 +/- 6.0, at 2nd FU 3.2 +/- 2.1/14.9 +/- 6.5; p = ns. RA-PTH/RV-PTH at baseline 0.68 +/- 0.18/0.78 +/- 0.22, at 2nd FU 0.71 +/- 0.24/0.78 +/- 0.22; p = ns). The presence of the permanent pacemakers led to MR imaging artifacts on diffusion weighted sequences of the brain, but did not affect other sequences (e.g. FLAIR and T2 weighted spin-echo images). CONCLUSION: The use of the MR conditional Evia PM in a MR environment under predefined conditions is feasible. No MR related SADEs nor clinically relevant changes in device functions occurred.

Concepts: Brain, Statistics, Lumbar vertebrae, Nuclear magnetic resonance, Magnetic resonance imaging, Student's t-test, Artificial pacemaker, Transcutaneous pacing

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Spontaneous contractile activity, such as gut peristalsis, is ubiquitous in animals and is driven by pacemaker cells. In humans, disruption of the contraction pattern leads to gastrointestinal conditions, which are also associated with gut microbiota dysbiosis. Spontaneous contractile activity is also present in animals lacking gastrointestinal tract. Here we show that spontaneous body contractions in Hydra are modulated by symbiotic bacteria. Germ-free animals display strongly reduced and less regular contraction frequencies. These effects are partially restored by reconstituting the natural microbiota. Moreover, soluble molecule(s) produced by symbiotic bacteria may be involved in contraction frequency modulation. As the absence of bacteria does not impair the contractile ability itself, a microbial effect on the pacemakers seems plausible. Our findings indicate that the influence of bacteria on spontaneous contractile activity is present in the early-branching cnidarian hydra as well as in Bilateria, and thus suggest an evolutionary ancient origin of interaction between bacteria and metazoans, opening a window into investigating the roots of human motility disorders.

Concepts: Photosynthesis, Archaea, Bacteria, Microbiology, Animal, Modulation, Cnidaria, Artificial pacemaker

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BACKGROUND: Fractures of pace-sense (P/S) conductors in implantable cardioverter defibrillator (ICD) leads have been studied extensively, but little is known about fractures of high-voltage (HV) conductors. OBJECTIVE: The purpose of this study is to characterize the presentation of isolated HV conductor fractures, define the optimal impedance threshold for identifying them, and compare it to the existing nominal impedance threshold (200 Ω) for patient and remote-monitoring alerts. METHODS: This retrospective study analyzed HV fractures in explanted, dual-coil, model 6949 Sprint FidelisTM (Medtronic, Minneapolis, MN) leads. The study group consisted of 25 leads with structurally and electrically confirmed HV conductor fractures; 41 leads that were structurally and electrically intact served as controls. We analyzed long-term HV impedance trends from stored ICD data files of both groups to determine the optimal impedance threshold that would discriminate fractures from normal leads. RESULTS: In the study group, 14 leads (56%) had fractures of the cable to the RV coil, 9 (36 %) leads had fractures of the cable to the SVC coil, 2 (8%) had both. We found that an impedance threshold of > 100 Ω and/or an abrupt 75% increase in chronic HV impedance were diagnostic of HV conductor fractures with 100% sensitivity and specificity. HV fractures proximal to the SVC coil were more likely to be associated with concomitant P/S fractures. Abrupt large (200 Ω-infinity) increases in impedance were more common when fractures occurred proximal to the RV coil but distal to the SVC coil. CONCLUSIONS: HV conductor fractures can be diagnosed when HV impedance exceeds 100 Ω or abruptly increases by 75% from baseline.

Concepts: Electricity, Positive predictive value, Type I and type II errors, Sensitivity and specificity, Implantable cardioverter-defibrillator, High voltage, Artificial pacemaker

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Different methods for venous access are used for permanent pacemaker or implantable cardioverter defibrillator (ICD), of which subclavian vein puncture technique is the most widely practised. Although this approach is relatively easy to learn, quick and offers high success rates, it may be associated with potential serious acute complications including pneumothorax, emopneumothorax, brachial plexus injury and longer-term complications such as lead fracture, loss of lead insulation and subclavian crush syndrome especially in young patients with ICD leads. Axillary vein approach seems to be a favourable technique not only for the prevention of acute complications but also to reduce lead failure including lead insulation and lead fracture prevention with a consequently better long-term lead survival compared with the classical subclavian approach. Although randomized studies are lacking, recent reports not only evaluated the safety and effectiveness of new fluoroscopic axillary venous puncture technique, but also compared it with the conventional intrathoracic subclavian venous puncture technique for the implantation of leads in permanent pacing. Various techniques of axillary vein puncture have been proposed ranging from a blind percutaneous puncture to the use of different tools such as contrast venography and ultrasound. In this article, we report a case of subclavian crush syndrome, the use of a modified Bellot’s technique of axillary vein puncture that we currently use and the potential benefits of axillary vein puncture for pacemaker and ICD leads implantation compared with subclavian approach to avoid acute and long-term lead complications.

Concepts: Implantable cardioverter-defibrillator, Magnetic resonance imaging, Subclavian vein, Artificial pacemaker, Brachial plexus, Subclavian artery, Axillary artery, Axillary vein

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The subcutaneous implantable cardioverter-defibrillator (S-ICD) and leadless pacemaker (LP) are evolving technologies that do not require intracardiac leads. However, interactions between these two devices are unexplored. We investigated the feasibility, safety, and performance of combined LP and S-ICD therapy, considering (i) simultaneous device-programmer communication, (ii) S-ICD rhythm discrimination during LP communication and pacing, and (iii) post-shock LP performance.

Concepts: Implantable cardioverter-defibrillator, Cardiac electrophysiology, Artificial pacemaker

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Temporary pacemakers are used in a variety of critical care settings. These life-saving devices are reviewed in 2 major categories in this review: first, the insertion and management of epicardial pacemakers after and during cardiac surgery; and second, the insertion of transvenous temporary pacemakers for the emergent treatment of bradyarrhythmias. Temporary epicardial pacemakers are used routinely in patients recovering from cardiac surgery. Borrowing from advances in cardiac resynchronization therapy there are many theoretical and untested benefits to pacing the postoperative cardiac surgery patient. Temporary transvenous pacing is traditionally an emergency procedure to stabilize patients suffering from hemodynamically unstable bradyarrhythmia. We review the traditional and expanding use of transvenous pacemakers inside and outside the operating room.

Concepts: Patient, Hospital, Physician, Review, Tradition, Artificial pacemaker, Transcutaneous pacing, Bradycardia

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The Sprint Fidelis defibrillator lead (Medtronic) was recalled in 2007 due to an increased risk of failure. The generator exchange (GE) procedure has been associated with the development of Fidelis lead dysfunction. The aim of this study was to compare the rate of dysfunction between Sprint Fidelis and other defibrillator leads during the first year after GE.

Concepts: Artificial pacemaker, Sprint Nextel, Medtronic

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Somatic reprogramming by reexpression of the embryonic transcription factor T-box 18 (TBX18) converts cardiomyocytes into pacemaker cells. We hypothesized that this could be a viable therapeutic avenue for pacemaker-dependent patients afflicted with device-related complications, and therefore tested whether adenoviral TBX18 gene transfer could create biological pacemaker activity in vivo in a large-animal model of complete heart block. Biological pacemaker activity, originating from the intramyocardial injection site, was evident in TBX18-transduced animals starting at day 2 and persisted for the duration of the study (14 days) with minimal backup electronic pacemaker use. Relative to controls transduced with a reporter gene, TBX18-transduced animals exhibited enhanced autonomic responses and physiologically superior chronotropic support of physical activity. Induced sinoatrial node cells could be identified by their distinctive morphology at the site of injection in TBX18-transduced animals, but not in controls. No local or systemic safety concerns arose. Thus, minimally invasive TBX18 gene transfer creates physiologically relevant pacemaker activity in complete heart block, providing evidence for therapeutic somatic reprogramming in a clinically relevant disease model.

Concepts: DNA, Gene, Genetics, Heart, Cardiac electrophysiology, Cardiac pacemaker, Sinoatrial node, Artificial pacemaker

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Transvenous implantable cardioverter-defibrillators (TV-ICDs) improve survival in patients at risk for sudden cardiac death, but complications remain an important drawback. The subcutaneous ICD (S-ICD) was developed to overcome lead-related complications. Comparison of clinical outcomes of both device types in previous studies was hampered by dissimilar patient characteristics.

Concepts: Patient, Implantable cardioverter-defibrillator, Cardiac arrest, Ventricular fibrillation, Sudden cardiac death, Artificial pacemaker

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Three patients with chronic HCV infection had bradyarrhythmias requiring pacemaker implantation during sofosbuvir treatment. The manufacturer of sofosbuvir notes that the cases were reported to authorities and concludes that recommendations seem premature.

Concepts: Hepatitis C, Artificial pacemaker