Deep learning methods for screening patients' S-ICD implantation eligibility.

Acknowledgments The work of Anthony J. Dunn is jointly funded by Decision Analysis Services Ltd. and EPSRC through the Studentship with Reference EP/R513325/1. The work of Alain B. Zemkoho is supported by the EPSRC grant EP/V049038/1 and the Alan Turing Institute under the EPSRC grant EP/N510129/1. The feedback provided by Sion Cave (DAS Ltd) on the initial draft of the paper is gratefully acknowledged.Peer reviewedPublisher PD

Electrocardiographic changes during haemodialysis and the potential impact on subcutaneous implantable cardioverter defibrillator eligibility

Acknowledgments The authors would like to acknowledge the kindness and support that they received from all of the patients and staff at the Chandler's Ford Dialysis Unit. Funding This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.Peer reviewedPublisher PD

Deep learning methods for screening patients' S-ICD implantation eligibility

Subcutaneous Implantable Cardioverter-Defibrillators (S-ICDs) are used for prevention of sudden cardiac death triggered by ventricular arrhythmias. T Wave Over Sensing (TWOS) is an inherent risk with S-ICDs which can lead to inappropriate shocks. A major predictor of TWOS is a high T:R ratio (the ratio between the amplitudes of the T and R waves). Currently patients' Electrocardiograms (ECGs) are screened over 10 seconds to measure the T:R ratio, determining the patients' eligibility for S-ICD implantation. Due to temporal variations in the T:R ratio, 10 seconds is not long enough to reliably determine the normal values of a patient's T:R ratio. In this paper, we develop a convolutional neural network (CNN) based model utilising phase space reconstruction matrices to predict T:R ratios from 10-second ECG segments without explicitly locating the R or T waves, thus avoiding the issue of TWOS. This tool can be used to automatically screen patients over a much longer period and provide an in-depth description of the behaviour of the T:R ratio over that period. The tool can also enable much more reliable and descriptive screenings to better assess patients' eligibility for S-ICD implantation

Correlation analysis of deep learning methods in S-ICD screening

© 2023 The Authors. Annals of Noninvasive Electrocardiology published by Wiley Periodicals LLC.Peer reviewedPublisher PD

Contemporary Management of Complex Ventricular Arrhythmias

Percutaneous catheter ablation is an effective and safe therapy that can eliminate ventricular tachycardia, reducing the risks of both recurrent arrhythmia and shock therapies from a defibrillator. Successful ablation requires accurate identification of arrhythmic substrate and the effective delivery of energy to the targeted tissue. A thorough pre-procedural assessment is needed before considered 3D electroanatomical mapping can be performed. In contemporary practice, this must combine traditional electrophysiological techniques, such as activation and entrainment mapping, with more novel physiological mapping techniques for which there is an ever-increasing evidence base. Novel techniques to maximise energy delivery to the tissue must also be considered and balanced against their associated risks of complication. This review provides a comprehensive appraisal of contemporary practice and the evidence base that supports recent developments in mapping and ablation, while also considering potential future developments in the field

The Genome of C57BL/6J Eve , the Mother of the Laboratory Mouse Genome Reference Strain.

Isogenic laboratory mouse strains enhance reproducibility because individual animals are genetically identical. For the most widely used isogenic strain, C57BL/6, there exists a wealth of genetic, phenotypic, and genomic data, including a high-quality reference genome (GRCm38.p6). Now 20 years after the first release of the mouse reference genome, C57BL/6J mice are at least 26 inbreeding generations removed from GRCm38 and the strain is now maintained with periodic reintroduction of cryorecovered mice derived from a single breeder pair, aptly named Adam and Eve. To provide an update to the mouse reference genome that more accurately represents the genome of today\u27s C57BL/6J mice, we took advantage of long read, short read, and optical mapping technologies to generate a de novo assembly of the C57BL/6J Eve genome (B6Eve). Using these data, we have addressed recurring variants observed in previous mouse genomic studies. We have also identified structural variations, closed gaps in the mouse reference assembly, and revealed previously unannotated coding sequences. This B6Eve assembly explains discrepant observations that have been associated with GRCm38-based analyses, and will inform a reference genome that is more representative of the C57BL/6J mice that are in use today

Lichenometric dating (lichenometry) and the biology of the lichen genus rhizocarpon:challenges and future directions

Lichenometric dating (lichenometry) involves the use of lichen measurements to estimate the age of exposure of various substrata. Because of low radial growth rates and considerable longevity, species of the crustose lichen genus Rhizocarpon have been the most useful in lichenometry. The primary assumption of lichenometry is that colonization, growth and mortality of Rhizocarpon are similar on surfaces of known and unknown age so that the largest thalli present on the respective faces are of comparable age. This review describes the current state of knowledge regarding the biology of Rhizocarpon and considers two main questions: (1) to what extent does existing knowledge support this assumption; and (2) what further biological observations would be useful both to test its validity and to improve the accuracy of lichenometric dates? A review of the Rhizocarpon literature identified gaps in knowledge regarding early development, the growth rate/size curve, mortality, regeneration, competitive effects, colonization, and succession on rock surfaces. The data suggest that these processes may not be comparable on different rock surfaces, especially in regions where growth rates and thallus turnover are high. In addition, several variables could differ between rock surfaces and influence maximum thallus size, including rate and timing of colonization, radial growth rates, environmental differences, thallus fusion, allelopathy, thallus mortality, colonization and competition. Comparative measurements of these variables on surfaces of known and unknown age may help to determine whether the basic assumptions of lichenometry are valid. Ultimately, it may be possible to take these differences into account when interpreting estimated dates

Personalising device therapy by redefining the sensing mechanism of the subcutaneous implantable cardioverter defibrillator

Ventricular tachyarrhythmias (VTA) are rapid abnormal heart rhythms which can result in haemodynamic compromise, collapse and sudden cardiac death (SCD). The annual global mortality burden attributed to VTA is approximately 6 million. Fortunately, in populations at high risk of arrhythmic death, the implantable cardioverter defibrillator (ICD) significantly reduces mortality and is superior to medical therapy in both the primary and secondary prevention of SCD. The subcutaneous ICD (S‐ICD) represents a new approach in defibrillator therapy. Utilising an entirely avascular location, the S‐ICD can diagnose and treat VTA, whilst avoiding the significant complications that have traditionally been associated with transvenous defibrillator leads. Accurate rhythm detection remains vital and increasingly sophisticated diagnostic algorithms are utilised. Life‐saving therapy must never be incorrectly withheld, but inappropriate shocks, which are themselves associated with increased mortality and psychological morbidity, must also be minimised. The S‐ICD senses electrocardiogram (ECG) signals from a standardised subcutaneous location at which effective defibrillation has been consistently demonstrated. Three different sensing vectors are available of which one is selected for clinical use. Rhythm detection requires certain morphological ECG characteristics to be present in the selected vector and pre‐implant ECG screening is therefore a mandatory requirement. The commonest cause for vector screening failure is the presence of a low R:T ratio, as this prevents the S‐ICD from easily distinguishing R wave signal (ventricular depolarisation) from T wave signal (ventricular repolarisation). The overall axes of ventricular depolarisation and repolarisation are unique to an individual. R and T wave amplitudes are therefore determined, in part, by the angle from which they are observed. Mathematical vector rotation is a novel strategy which can manipulate the angle of observation of an individual’s ECG, using data recorded from the current S‐ICD location.This can produce personalised vectors; unique individualised vectors with a recipient’s maximal R:T ratio. In this thesis, I will describe how personalised vector generation can be achieved, before applying the technique to a cohort of S‐ICD ineligible patients. Significant improvements in R:T ratio and device eligibility will be demonstrated. I will then explore the broader impact of vector rotation on the current rhythm discrimination properties of the S‐ICD system. I will demonstrate that both ventricular fibrillation detection and supraventriculartachycardia discrimination are not impaired by vector rotation. These are key principles of S‐ICD sensing which must be maintained by any future sensing strategy. Finally, I shall consider the phenomena of T wave over‐sensing (TWOS), which despite the current screening process, remains the commonest cause of inappropriate shock therapy in the S‐ICD population. I will describe a new concept, ‘eligible vector time’, and demonstrate experimentally that patients experience chronological fluctuations in their device eligibility. This preliminary work will redefine our current understanding of device eligibility and justify future research into the role of vector rotation in reducing inappropriate shock therapies. In summary, I believe that clinicians and patients should not be restricted by the inherent limitations of standardised vector selection. Personalised vector generation can be achieved from the current S‐ICD location, whilst maintaining the excellent rhythm detection qualities of the S‐ICD system. Increased S‐ICD eligibility can be achieved and the potential to reduce TWOS in the future cannot be ignored