Gradual rise in lead impedance - A "rocky" course.
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ABSTRACT:
SUBMITTER: Pothineni NVK
PROVIDER: S-EPMC8695284 | biostudies-literature |
REPOSITORIES: biostudies-literature
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Project description:BackgroundPace-sense conductors comprise a pacing coil to the tip electrode and cable to the ring-electrode. Implantable cardioverter-defibrillator (ICD) lead-monitoring diagnostics include pacing impedance (direct current resistance [DCR]) and measures of oversensing. How they change as fractures progress is unknown.ObjectivesTo characterize the relationship between oversensing, impedance, and structural changes in ICD leads developing pace-sense conductor fractures.MethodsWe performed bending tests on 39 leads connected to ICD generators in an electrolyte bath with simulated electrograms. DCR was recorded every 3 minutes; electrograms were telemetered continuously. Twenty-two leads were tested to develop partial or complete fracture criteria confirmed by imaging, using DCR or DCR variability measured by standard deviation (σDCR). Results are reported for 17 other test leads.ResultsInitial oversensing occurred with partial pacing coil fracture vs complete ring cable fracture and correlated with bending-induced DCR peaks. These peaks were too small to be detected by clinical impedance measurements and were characterized by small increases in σDCR (≥0.5 Ω). Impedance threshold alerts occurred at complete pacing coil fracture but only later for ring cable fractures. The oversensing alert triggered before device-detected ventricular fibrillation more frequently than impedance alerts (94% vs 17%; P = .00002).ConclusionsIn conductor fracture, early oversensing corresponds to partial pacing coil fracture or complete ring cable fracture and correlates with transient bending-induced impedance increases, which are detected by impedance variability but too small to trigger clinical impedance alerts. This explains why clinical oversensing alerts provide more warning for device-detected ventricular fibrillation than impedance alerts and suggests how to improve impedance diagnostics based on short-term variability.
| S-EPMC9795312 | biostudies-literature
Project description:The impacts of sea-level rise (SLR) are likely to be the greatest for ecosystems that exist at the land-sea interface, where small changes in sea-level could result in drastic changes in habitat availability. Rocky intertidal ecosystems possess a number of characteristics which make them highly vulnerable to changes in sea-level, yet our understanding of potential community-scale responses to future SLR scenarios is limited. Combining remote-sensing with in-situ large-area imaging, we quantified habitat extent and characterized the biological community at two rocky intertidal study locations in California, USA. We then used a model-based approach to estimate how a range of SLR scenarios would affect total habitat area, areal extent of dominant benthic space occupiers, and numerical abundance of invertebrates. Our results suggest that SLR will reduce total available rocky intertidal habitat area at our study locations, leading to an overall decrease in areal extent of dominant benthic space occupiers, and a reduction in invertebrate abundances. As large-scale environmental changes, such as SLR, accelerate in the next century, more extensive spatially explicit monitoring at ecologically relevant scales will be needed to visualize and quantify their impacts to biological systems.
| S-EPMC7263295 | biostudies-literature
Project description:The complex and still poorly understood nature of thermoregulation in various fish species complicates the determination of the physiological status on the basis of diagnostic marker genes and indicative molecular pathways. The present study aimed to compare the physiological impacts of both gradual and acute temperature rise from 18 to 24°C on maraena whitefish in aquaculture. Microarray-based transcriptome profiles in the liver, spleen and kidney of heat-stressed maraena whitefish revealed the modulation of a significantly higher number of genes in those groups exposed to gradually rising temperatures compared with the acutely stressed groups, which might reflect early adaptation mechanisms. Moreover, we suggest a common set of 11 differentially expressed genes that indicate thermal stress induced by gradual or acute temperature rise in the three selected tissues. Besides the two pathways regulated in both data sets unfolded protein response and aldosterone signaling in epithelial cells, we identified unique tissue- and stress type-specific pathways reflecting the crossroads between signal transduction, metabolic and immunologic pathways to cope with thermal stress. In addition, comparing lists of differentially regulated genes with meta-analyzed published data sets revealed that "acute temperature rise"-responding genes that encode members of the HSP70, HSP90, and HSP40 families; their functional homologs; co-chaperones and stress-signal transducers are well-conserved across different species, tissues and/or cell types and experimental approaches.
| S-EPMC6060367 | biostudies-literature
Project description: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??). 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??/month vs. 0.0008?±?0.005??/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.
| S-EPMC6939807 | biostudies-literature
Project description:This communication reports the synthesis of bis(diisobutyldithiophosphinato)lead(II) complex and its subsequent application as a single source precursor for the nanostructured deposition of lead sulphide semiconductors and its impedance to explore its scope in the field of electronics. Synthesized complex was characterized by microelemental analysis, nuclear magnetic resonance spectroscopy, infrared spectroscopy and thermogravimetric analysis. This complex was decomposed using the aerosol-assisted chemical vapour deposition technique at different temperatures to grow PbS nanostructures on glass substrates. These nanostructures were analyzed by XRD, SEM, TEM and EDX methods. Impedance spectroscopic measurements were performed for PbS in the frequency range of 40 to 6 MHz at room temperature. In a complex impedance plane plot, two relaxation processes were exhibited due to grains and grain boundaries contribution. A high value of dielectric constant was observed at low frequencies, which was explained on the basis of Koops phenomenological model and Maxwell-Wagner type polarization. Frequency-dependent AC conductivity results were compliant with Jonscher power law, while capacitance-voltage loop had a butterfly shape. These impedance spectroscopic results have corroborated the ferroelectric nature of the resultant PbS nanodeposition.
| S-EPMC7466212 | biostudies-literature
Project description: Not available
| S-EPMC5418612 | biostudies-literature
Project description:Scholars within the medical sciences recently have called on undergraduate educators to incorporate the social sciences in order to teach pre-health students structural competencies - or the ability to articulate how social structures produce racial, ethnic, gender, class, and other disparities - in order to better serve these populations medically. Authors used a semester-long course to assess how experiential learning focused on the topic of structural inequities improves structural competency. In Fall 2018, 27 students completed a hands-on, experiential, course focused on structural factors and health disparities. The authors conducted a mixed-methods, pre-/post-test design to solicit data on students' views on the reasons for high rates of obesity, gender pay disparities, and racial/ethnic housing segregation. Using systematic qualitative data analysis and statistical analysis of coded answers, the authors were able to detect pre-/post-test differences in the number of times students identified structural reasons for the disparities. Statistical analysis showed that students were able to identify an average of 4.63 structural reasons at pre-test, and that increased to 5.93 reasons at post-test (statically significant (p = 0.007)), indicating an increase in structural awareness after participation in the course. Qualitative analysis, using systematic methods of coding and a modified constant comparison method, demonstrated that students' ability to articulate structural reasons for inequality greatly improved. This experiential learning course, while relatively short, was found to increase students' ability to identify structural factors and articulate them with deeper understandings. Future curriculum development should consider incorporating experiential learning to promote structural competency, rather than a more traditional passive, content-delivery method of training.
| S-EPMC8368733 | biostudies-literature
Project description:Sirtuin 1 (SIRT1), the NAD-dependent histone deacetylase, has been extensively investigated due to its cognitive protective effect. Studies suggest microRNAs (miRNAs) and histone modifications are key epigenetic regulators of gene expression and play important role in brain development. We previously showed that cognitive impairment by lead (Pb) was associated with downregulation of SIRT1, but the epigenetic role of this is unclear. Thus, we exposed 4-week-old male mice to 0.2% lead acetate solution for three months, and subsequently extracted brain homogenate from mice cortex and hippocampus at the age of 1, 4, and 16 months, respectively. In this study, we found that the protein level of SIRT1 was inhibited in the hippocampus and cortex of 16-month-old aged mice exposed to Pb. Moreover, changes in the levels of miR-138-5p and miR-141-3p, which were considered to the mechanistic target of SIRT1 by bioinformatic analysis, were negative correlations SIRT1 protein expression. We also found miR-34c-3p expression was increased in the cortex of mice at the age of 16 months. Collectively, our results showed the expression of neural SIRT1 and three selected microRNAs at different age nodes of mice for the first time of following Pb exposure. Our results suggest that additional efforts should focus on the consequences of early Pb exposure from an epigenetic perspective.
| S-EPMC8403607 | biostudies-literature
Project description:ObjectiveAt first hospitalization, a long duration of untreated psychosis (DUP) predicts illness severity and worse treatment outcomes. The mechanism of this association, however, remains unclear. It has been hypothesized that lengthy untreated psychosis is toxic or that it reflects a more severe form of schizophrenia. Alternatively, the association may be an artifact of lead-time bias. These hypotheses are tested in a longitudinal study of schizophrenia with 2,137 observations spanning from childhood to 20 years after first admission.MethodsData were from the Suffolk County Mental Health Project. The cohort included 287 individuals with schizophrenia or schizoaffective disorder. DUP was defined as days from first psychotic symptom to first psychiatric hospitalization. Psychosocial function was assessed using the Premorbid Adjustment Scale and the Global Assessment of Functioning Scale. Psychosocial function trajectories were estimated using multilevel spline regression models adjusted for gender, occupational status, race, and antipsychotic medication.ResultsBoth long- and short-DUP patients experienced similar declines in psychosocial function, but declines occurred at different times relative to first admission. Long-DUP patients experienced most of these declines prior to first admission, while short-DUP patients experienced declines after first admission. When psychosocial function was analyzed relative to psychosis onset, DUP did not predict illness course.ConclusionsThe association between DUP and psychosocial function may be an artifact of early detection, creating the illusion that early intervention is associated with improved outcomes. In other words, DUP may be better understood as an indicator of illness stage than a predictor of course.
| S-EPMC10754034 | biostudies-literature
Project description:We investigated 2 fatal cases of Rocky Mountain spotted fever that occurred in 2003 and 2004 near the same locality in Colombia where the disease was first reported in the 1930s. A retrospective serosurvey of febrile patients showed that > 21% of the serum samples had antibodies aaainst spotted fever group rickettsiae.
| S-EPMC2878212 | biostudies-literature