Eligibility for subcutaneous implantable cardiac defibrillator utilising artificial intelligence and deep learning methods for prolonged screening: where is the cut-off?

Funding Acknowledgements

Type of funding sources: Private grant(s) and/or Sponsorship. Main funding source(s): Main author is receiving an unrestricted grant by Boston Scientific

Background

S-ICD eligibility is determined by a single surface ECG analysis in which the suitability of an individual’s ECG vector morphology is assessed. A major predictor of eligibility is the T:R ratio. Current screening tools proposes T: R of 1:3 as a cut-off for eligibility. Inappropriate shocks due to T-wave oversensing (TWO) remains an issue despite screening. EFFORTLESS and PRAETORIAN trials reported inappropriate shock rates of 11.4% and 9.7% respectively, most frequently caused by cardiac oversensing.

Purpose

The cut-off T: R of 1:3 currently used incorporates a safety margin to accommodate for ECG signal amplitudes fluctuations without affecting S-ICD sensing. Prolonged screening using our tool accurately measures the T: R fluctuations. However, utilising a T: R of 1:3 for prolonged screening can unnecessarily exclude appropriate S-ICD candidates. The purpose of our study is to provide groundwork for future trials to find the optimal ratio that identifies patients at risk of TWO and inappropriate shocks while not excluding true S-ICD candidates after prolonged screening.

Methods

Patients were fitted with 24-hour Holter monitors with leads placed to correspond to the vectors of an S-ICD. We used our tool to assess T: R over the recordings utilising Phase Space Reconstruction matrices - to convert the ECG signal into compressed pixel images. A Convolutional Neural Network (CNN) model was trained to accurately predict the T: R from these images resulting in a T: R variation plot for each vector. We then applied multiple T:R ratio cut-offs on the recordings to identify patients at risk of inappropriate shocks due to TWO at each proposed value. A vector with a T: R above the cut-off for 20 consecutive seconds was deemed to have failed screening, the time determined by the current detection, charge, and redetection time of the current S-ICD system. A patient has to have at least one suitable vector to pass the screening at the selected threshold.

Results

37 patients (mean age 54.5 years,64.8% male) were included. 14 had Heart failure, 7 Hypertrophic cardiomyopathy, 7 normal hearts, 6 Adult congenital heart disease and 3 patients who received inappropriate S-ICD shocks due to TWO. Overall, 20 (54%) of patients passed prolonged screening using a 1:3 ratio. All of the patients passed screening with a T: R of 1:1. The only subgroup to wholly pass the screening for all the proposed ratios are the normal hearts group.

Conclusion

We propose adopting prolonged screening to select S-ICD eligible patients with low probability of TWO and inappropriate shocks. However, utilising T: R of 1:3 can unnecessarily exclude otherwise S-ICD eligible patients. The appropriate ratio likely lies between 1:3 - 1:1. Further studies are needed to identify the optimal screening thresholds, particularly in patients that have had inappropriate shocks due to TWO.

The use of artificial intelligence and deep learning methods in subcutaneous implantable cardioverter defibrillator screening to optimise selection in special patient populations

Funding Acknowledgements

Type of funding sources: Private company. Main funding source(s): Dr.Mohamed ElRefai is receiving an unrestricted grant from Boston Scientific.

Introduction

Adult congenital heart disease (ACHD) and hypertrophic cardiomyopathy (HCM) patients who require defibrillator therapy are often relatively young and may require several generator replacements in their lifetime. The increased risk of complications associated with transvenous ICDs make the subcutaneous (S-ICD) a valuable alternative. However, higher S-ICD ineligibility rates (20-40% in ACHD and 7-38% in HCM) and higher inappropriate shock rates (10.5% in ACHD and 12.5% in HCM) are observed in these populations. Unfavourable T:R ratios and dynamic changes in the R and T wave amplitudes are the primarily factors behind ineligibility and inappropriate shocks, which are most commonly caused by T wave over-sensing.

Purpose

We report a novel application of deep learning methods used to autonomously screen patients for S-ICD eligibility over a longer period than conventional screening. We hypothesise that this screening approach might achieve better patient selection and optimise S-ICD vector selection in challenging patient cohorts.

Methods

Adult patients with ACHD or HCM and a control group of normal subjects were fitted with a 24-hour ambulatory ECG with the leads placed to record their S-ICD vectors. T: R ratio throughout the recordings was analysed utilising phase space reconstruction matrices to convert the ECG signal into compressed pixel images. Whilst a convolutional neural network model was trained to provide an in-depth description of the T: R variation plot for each vector T: R variation was compared statistically using a one-way ANOVA test.

Results

20 patients (age 44.1 ±11.68, 60% male, 7 HCM, 6 ACHD and 7 control subjects) were enrolled. A significant difference was observed in the mean and median T: R values between the three groups (p<0.001). There was no difference observed in the standard deviation of T: R between the control subjects and HCM group. However, there was a statistically significant difference in the standard deviation of T: R between the control subjects and the ACHD group (p= 0.01). [see Figure].

Conclusions

T:R ratio, a main determinant for S-ICD eligibility, is significantly higher in ACHD and HCM when compared to normal hearts and it also has more tendency to fluctuate in ACHD patients when compared to HCM and normal hearts populations. We hypothesise that our novel model could be used to select S-ICD eligible patients by better characterisation of T:R ratio reducing the risk of T wave oversensing and inappropriate shocks particularly in the ACHD patients’ cohort.

Blood immune transcriptome analysis of artificially fed dairy calves and naturally suckled beef calves from birth to 7 days of age

Neonatal calves possess a very immature and naïve immune system and are reliant on the intake of maternal colostrum for passive transfer of immunoglobulins. Variation in colostrum management of beef and dairy calves is thought to affect early immune development. Therefore, the objective of this study was to examine changes in gene expression and investigate molecular pathways involved in the immune-competence development of neonatal Holstein dairy calves and naturally suckled beef calves using next generation RNA-sequencing during the first week of life. Jugular whole blood samples were collected from Holstein (H) dairy calves (n = 8) artificially fed 5% B.W. colostrum, and from beef calves which were the progenies of Charolais-Limousin (CL; n = 7) and Limousin-Friesian beef suckler cows (LF; n = 7), for subsequent RNA isolation. In dairy calves, there was a surge in pro-inflammatory cytokine gene expression possibly due to the stress of separation from the dam. LF calves exhibited early signs of humoral immune development with observed increases in the expression genes coding for Ig receptors, which was not evident in the other breeds by 7 days of age. Immune and health related DEGs identified as upregulated in beef calves are prospective contender genes for the classification of biomarkers for immune-competence development, and will contribute towards a greater understanding of the development of an immune response in neonatal calves.

Assigning a structural motif using spontaneous molecular dipole orientation in thin films

Guided by the spontelectric behaviour of thin films of cis-methyl formate, infrared observations and computational investigations reveal the dimer structural motif of the crystalline solid.

Thoughtflow: Standards and Tools for Provenance Capture and Workflow Definition to Support Model-Informed Drug Discovery and Development

Pharmacometric analyses are complex and multifactorial. It is essential to check, track, and document the vast amounts of data and metadata that are generated during these analyses (and the relationships between them) in order to comply with regulations, support quality control, auditing, and reporting. It is, however, challenging, tedious, error-prone, and time-consuming, and diverts pharmacometricians from the more useful business of doing science. Automating this process would save time, reduce transcriptional errors, support the retention and transfer of knowledge, encourage good practice, and help ensure that pharmacometric analyses appropriately impact decisions. The ability to document, communicate, and reconstruct a complete pharmacometric analysis using an open standard would have considerable benefits. In this article, the Innovative Medicines Initiative (IMI) Drug Disease Model Resources (DDMoRe) consortium proposes a set of standards to facilitate the capture, storage, and reporting of knowledge (including assumptions and decisions) in the context of model-informed drug discovery and development (MID3), as well as to support reproducibility: "Thoughtflow." A prototype software implementation is provided.

Evaluation of factors associated with immunoglobulin G, fat, protein, and lactose concentrations in bovine colostrum and colostrum management practices in grassland-based dairy systems in Northern Ireland

The objectives of this study were to investigate colostrum feeding practices and colostrum quality on commercial grassland-based dairy farms, and to identify factors associated with colostrum quality that could help inform the development of colostrum management protocols. Over 1 yr, background information associated with dairy calvings and colostrum management practices were recorded on 21 commercial dairy farms. Colostrum samples (n = 1,239) were analyzed for fat, protein, lactose, and IgG concentration. A subset was analyzed for somatic cell count and total viable bacteria count. Factors associated with nutritional and IgG concentrations were determined using both univariate and multivariate models. This study found that 51% of calves were administered their first feed of colostrum via esophageal tube, and the majority of calves (80%) were fed >2 L of colostrum at their first feed (mean = 2.9 L, SD = 0.79), at a mean time of 3.2 h (SD 4.36) after birth, but this ranged across farms. The mean colostral fat, protein, and lactose percentages and IgG concentrations were 6.4%, 14%, 2.7%, and 55 mg/mL, respectively. The mean somatic cell count and total viable count were 6.3 log₁₀ and 6.1 log₁₀, respectively. Overall, 44% of colostrum samples contained <50 mg/mL IgG, and almost 81% were in excess of industry guidelines (<100,000 cfu/mL) for bacterial contamination. In the multivariate model, IgG concentration was associated with parity and time from parturition to colostrum collection. The nutritional properties of colostrum were associated with parity, prepartum vaccination, season of calving, and dry cow nutrition. The large variation in colostrum quality found in the current study highlights the importance of routine colostrum testing, and now that factors associated with lower-quality colostrum on grassland-based dairy farms have been identified, producers and advisers are better informed and able to develop risk-based colostrum management protocols.

Survey of external cephalic version for breech presentation and neuraxial blockade use

STUDY OBJECTIVE

Neuraxial blockade may increase external cephalic version (ECV) success rates. This survey aimed to assess the frequency and characteristics of neuraxial blockade used to facilitate ECV.

SETTING AND DESIGN

We surveyed Society for Obstetric Anesthesia and Perinatology members regarding ECV practice using a 15-item survey developed by 3 obstetric anesthesiologists and tested for face validity. The survey was e-mailed in January 2015 and again in February 2015 to the 1056 Society of Obstetric Anesthesiology and Perinatology members. We present descriptive statistics of responses.

PARTICIPANTS

Our survey response rate was 322 of 1056 (30.5%).

MAIN RESULT

Neuraxial blockade was used for ECV always by 18 (5.6%), often by 52 (16.1%), sometimes by 98 (30.4%), rarely by 78 (24.2%), and never by 46 (14.3%) of respondents. An anesthetic sensory block target was selected by 141 (43.8%) respondents, and analgesic by 102 (31.7%) respondents. Epidural drug doses ranged widely, including sufentanil 5-25 μg; lidocaine 1% or 2% 10-20 mL, bupivacaine 0.0625% to 0.5% 6-15 mL, and ropivacaine 0.2% 20 mL. Intrathecal bupivacaine was used by 182 (56.5%) respondents; the most frequent doses were 2.5 mg used by 24 (7.5%), 7.5 mg used by 35 (10.9%), and 12 mg used by 30 (9.3%).

CONCLUSIONS

Neuraxial blockade is not universally offered to facilitate ECV, and there is wide variability in neuraxial blockade techniques, in drugs and doses administered, and in the sensory blockade (anesthetic or analgesic) targeted. Future studies need to evaluate and remove barriers to allow for more widespread use of neuraxial blockade for pain relief and to optimize ECV success rates.

Modulation of platelet membrane function via exogenous lipid moiety exposure alters platelet responsiveness to shear

Shear-induced platelet activation may cause life-threatening thrombosis, particularly in patients with mechanical support devices or coronary atherosclerosis. The majority of present anti-platelet agents target or interfere with biochemical, rather than physical mechanisms of platelet activation. Less data and understanding exists with regard to pharmacologic modulation of shear-mediated platelet activation. In this work, we hypothesized that modulating cell membrane properties, via alteration of membrane composition through addition of exogenous lipid moieties, would alter platelet responsiveness to shear. Here we tested fatty acids, lecithin and cholesterol as additive lipid compounds. We demonstrated that incorporation of fatty acids (DHA/EPA) or lecithin into the platelet membrane triggered enhanced sensitivity of platelets to shear-mediated activation. On the other hand, cholesterol incorporation provides significant protection, limiting the effect of shear on platelet activation. These findings provide valuable insight for the development of therapeutic strategies that can modulate shear-mediated platelet activation.

Secreted HoxA3 Promotes Epidermal Proliferation and Angiogenesis in Genetically Modified Three-Dimensional Composite Skin Constructs

Objective: Homeobox (HOX) transcription factors coordinate gene expression in wound repair and angiogenesis. Previous studies have shown that gene transfer of HoxA3 to wounds of diabetic mice accelerates wound healing, increasing angiogenesis and keratinocyte migration. In this study, we examined whether HoxA3 can also improve angiogenesis, epidermal integrity, and viability of composite skin grafts. Approach: To determine the effects of HoxA3 on composite skin grafts, we constructed bilayered composite grafts incorporating fibroblasts engineered to constitutively secrete HoxA3. We then transplanted these composite grafts in vivo. Results: The composite grafts produced a stratified epidermal layer after seventeen days in culture and following transplantation in vivo, these grafts exhibit normal epidermal differentiation and reduced contraction compared to controls. In addition, HoxA3 grafts showed increased angiogenesis. Quantitative polymerase chain reaction (PCR) analyses of HoxA3 graft tissue reveal an increase in the downstream HoxA3 target genes MMP-14 and uPAR expression, as well as a reduction in CCL-2 and CxCl-12. Innovation: Expression of secreted HoxA3 in composite grafts represents a comprehensive approach that targets both keratinocytes and endothelial cells to promote epidermal proliferation and angiogenesis. Conclusion: Secreted HoxA3 improves angiogenesis, reduces expression of inflammatory mediators, and prolongs composite skin graft integrity.

Bilateral skin fold rotation-advancement flaps for the closure of large lumbosacral wounds in three dogs

Three dogs were presented for the management of disease processes resulting in large skin defects over the dorsal lumbosacral region. One had severe dog bite wounds, one had a large burn sustained from a heating pad and one had a large myxosarcoma in the region. In each case, the extent and location of the resulting skin defect were assessed as factors likely to prevent reconstruction using simple tension-relieving techniques alone or in combination with established reconstructive techniques, such as axial pattern flaps or skin stretching devices. Bilateral skin fold rotation-advancement flaps (SFRAFs) based on the flank folds were mobilised dorsally and allowed complete wound closure in two dogs and subtotal closure in the other dog. All wounds healed without major complications and an acceptable cosmetic outcome was achieved in each case. Minor flap debridement was required in two dogs. The use of bilateral SFRAFs is a useful technique alone or in combination with other reconstructive techniques for the closure of large dorsal lumbosacral skin defects when existing techniques are not sufficient. Small flank folds, such as those of obese dogs, may yield unexpectedly large SFRAFs.

The use of the cemented Exeter Universal femoral stem in a District General Hospital

We describe the survivorship of the Exeter femoral component in a District General Hospital. Between 1994 and 1996, 230 Exeter Universal cemented femoral components were implanted in 215 patients who were reviewed at a mean of 11.2 years (10 to 13). We used one acetabular implant, the Elite Ogee component, in 218 of the 230 hips.

During the period of this study 76 patients (79 hips) died. Of the remaining 139 patients (151 hips), 121 were able to attend for radiological analysis at a minimum of ten years. One patient was lost to follow-up.

No femoral component was revised for aseptic loosening. Three hips were revised for deep infection and six acetabular components required revision, four for loosening and two for recurrent dislocation. Taking the ‘worst-case scenario’ including the one patient lost to follow-up, the overall survival rate was 94.4% at 13 years.

Our results confirm excellent medium-term results for the Exeter Universal femoral component, implanted in a general setting. The excellent survival of this femoral component, when used in combination with the Ogee acetabular component, suggests that this is a successful pairing.

The Role of the Kidney in Blood Volume Regulation: The Kidney as a Regulator of the Hematocrit

The kidney plays a pivotal role in the regulation of blood volume by controlling the plasma volume and red blood cell (RBC) mass. Further, it is proposed that the kidney coordinates the relative volumes of these 2 blood components and in so doing regulates the hematocrit. This novel function as proposed is a functional concept whereby the kidney does not simply produce erythropoietin, but that the kidney regulates the hematocrit is termed the critmeter function. The kidney is unique in that it can indirectly report on blood volume as a tissue oxygen signal. It is proposed that the kidneys detect small changes in tissue oxygen tension for erythropoietin production at the critmeter, a functional unit of marginal oxygen tension within the kidneys. As the production of erythropoietin is modulated by angiotensin II, the renin-angiotensin system entrains the production of erythropoietin as part of the effector signals of the feedback loop of blood volume regulation. Collectively, the consideration of these points generates a paradigm shift in our understanding of blood volume regulation in that the role of the kidney may be expanded from simply "producing" erythropoietin to regulating the hematocrit. Further, this concept broadens the scope of the traditionally identified effector mechanisms of plasma volume regulation to include the modulation of erythropoietin production and hence RBC mass. The inclusion of both plasma volume and RBC mass as factors targeted by the effector signals recapitulates that whole blood volume is sensed and reported in the afferent signals. In summary, distinct sensing and effector mechanisms for regulating the volume of the two components of whole blood (plasma and red cell mass) are recognized. The coupling of the regulation of these 2 components of blood volume is highlighted.

Prevention and treatment of musculoskeletal disease in the haemophilia population: role of prophylaxis and synovectomy

Prophylaxis is defined as primary (started before the onset of joint damage) or secondary (started after the onset of joint damage). The aim of primary prophylaxis is to prevent recurrent bleeding into joints and the development of chronic arthropathy in later life. When started early, and at most after two joint bleeds, the result is predictably excellent if there is compliance with the primary prophylaxis regimen. In order to decrease the need for central venous access devices to assure reliable venous access, a number of centres start primary prophylaxis with once weekly infusions with dose-escalation based on frequency of joint bleeding. A major unanswered question is whether primary prophylaxis can be safely discontinued in adolescents/young adults and if so, when. A promising predictor for the milder bleeding phenotype in persons with severe haemophilia is a later onset of joint bleeding. Once joint damage has occurred as a result of recurrent bleeding, secondary prophylaxis can only retard, but not prevent, ongoing joint damage. Other strategies to decrease recurrent bleeding from target joints include surgical synovectomy (ideally performed using an arthroscopic technique), radionuclide synovectomy and chemical synovectomy. These interventions have very good outcomes when performed by an experienced team. Given the very high cost of factor concentrates required for programmes of prophylaxis prospective studies that document benefits to the child and family, e.g. quality of life are to be encouraged.

Cytokine-mediated deployment of SDF-1 induces revascularization through recruitment of CXCR4+ hemangiocytes

The mechanisms through which hematopoietic cytokines accelerate revascularization are unknown. Here, we show that the magnitude of cytokine-mediated release of SDF-1 from platelets and the recruitment of nonendothelial CXCR4+ VEGFR1+ hematopoietic progenitors, 'hemangiocytes,' constitute the major determinant of revascularization. Soluble Kit-ligand (sKitL), thrombopoietin (TPO, encoded by Thpo) and, to a lesser extent, erythropoietin (EPO) and granulocyte-macrophage colony-stimulating factor (GM-CSF) induced the release of SDF-1 from platelets, enhancing neovascularization through mobilization of CXCR4+ VEGFR1+ hemangiocytes. Although revascularization of ischemic hindlimbs was partially diminished in mice deficient in both GM-CSF and G-CSF (Csf2-/- Csf3-/-), profound impairment in neovascularization was detected in sKitL-deficient Mmp9-/- as well as thrombocytopenic Thpo-/- and TPO receptor-deficient (Mpl-/-) mice. SDF-1-mediated mobilization and incorporation of hemangiocytes into ischemic limbs were impaired in Thpo-/-, Mpl-/- and Mmp9-/- mice. Transplantation of CXCR4+ VEGFR1+ hemangiocytes into Mmp9-/- mice restored revascularization, whereas inhibition of CXCR4 abrogated cytokine- and VEGF-A-mediated mobilization of CXCR4+ VEGFR1+ cells and suppressed angiogenesis. In conclusion, hematopoietic cytokines, through graded deployment of SDF-1 from platelets, support mobilization and recruitment of CXCR4+ VEGFR1+ hemangiocytes, whereas VEGFR1 is essential for their angiogenic competency for augmenting revascularization. Delivery of SDF-1 may be effective in restoring angiogenesis in individuals with vasculopathies.

Complete genome sequence of Vibrio fischeri: a symbiotic bacterium with pathogenic congeners

Vibrio fischeri belongs to the Vibrionaceae, a large family of marine gamma-proteobacteria that includes several dozen species known to engage in a diversity of beneficial or pathogenic interactions with animal tissue. Among the small number of pathogenic Vibrio species that cause human diseases are Vibrio cholerae, Vibrio parahaemolyticus, and Vibrio vulnificus, the only members of the Vibrionaceae that have had their genome sequences reported. Nonpathogenic members of the genus Vibrio, including a number of beneficial symbionts, make up the majority of the Vibrionaceae, but none of these species has been similarly examined. Here we report the genome sequence of V. fischeri ES114, which enters into a mutualistic symbiosis in the light organ of the bobtail squid, Euprymna scolopes. Analysis of this sequence has revealed surprising parallels with V. cholerae and other pathogens.

Threshold effects of glucose transporter-4 (GLUT4) deficiency on cardiac glucose uptake and development of hypertrophy

The aim of this study was to investigate the metabolic and structural consequences of a decrease in glucose transporter-4 (GLUT4) levels on the heart. The CreLoxP system was utilised to delete GLUT4 in muscle tIssue including heart. The presence of the PGK-neoR cassette in the GLUT4-Lox mice resulted in reduced expression in all tIssues to levels 15-30% of wild-type control mice. In mice expressing Cre recombinase, there was a further reduction of GLUT4 in cardiac tIssue to almost undetectable levels. Cardiac glucose uptake was measured basally and during a euglycaemic/hyperinsulinaemic clamp using 2-deoxy-[1-(14)C]glucose. Insulin-stimulated glucose uptake was normal in hearts expressing 15% of normal GLUT4 levels but markedly reduced in mice with more profound reduction in GLUT4. Cardiac enlargement occurred only when GLUT4 levels were less than 5% of normal values. In heart there is a threshold level of GLUT4 above which insulin-stimulated glucose uptake is maintained. As little as 5% of normal GLUT4 levels expressed in heart is sufficient to prevent the development of cardiac hypertrophy.

G-CSF: function and modes of action (Review)

Since the observations in the 1960s that granulocyte-colony stimulating factor (G-CSF) stimulated the proliferation of granulocytic cells in semisolid cultures of bone marrow cells, G-CSF has established itself as a useful clinical agent for increasing levels of neutrophilic granulocytes. However, these early findings did not firmly establish whether G-CSF is a genuine regulator of granulocyte formation under normal physiological conditions or rather acts as an emergency regulator, playing an important role only under stress conditions. The advent of <gene-knockout technology> has allowed us to evaluate these questions in a physiological setting through analysis of mice with a targeted mutation of G-CSF or its receptor, while the development of relevant cell models has enabled us to dissect the molecular basis of G-CSF action. This review discusses our current state of knowledge regarding the role of G-CSF in granulopoiesis.

Three dimensional Monte Carlo code for photon migration through complex heterogeneous media including the adult human head

We describe a novel Monte Carlo code for photon migration through 3D media with spatially varying optical properties. The code is validated against analytic solutions of the photon diffusion equation for semi-infinite homogeneous media. The code is also cross-validated for photon migration through a slab with an absorbing heterogeneity. A demonstration of the utility of the code is provided by showing time-resolved photon migration through a human head. This code, known as 'tMCimg', is available on the web and can serve as a resource for solving the forward problem for complex 3D structural data obtained by MRI or CT.

Clinical trials update: Highlights of the Scientific Sessions of Heart Failure 2001, a meeting of the Working Group on Heart Failure of the European Society of Cardiology. CONTAK-CD, CHRISTMAS, OPTIME-CHF

This article continues a series of reports summarising recent research developments pertinent to the topic of heart failure. This is a summary of presentations made at Scientific Sessions of Heart Failure 2001, a meeting of the Working Group on Heart Failure of the European Society of Cardiology. Clinical studies of particular interest to people caring for patients with heart failure include CONTAK-CD, CHRISTMAS and further updates on OPTIME-CHF. A brief review of the current status of cardiac resynchronisation therapy is included.