Utility of Monophasic Action Potentials in the Diagnosis and Treatment of Cardiac Arrhythmias

University of Minnesota Ph.D. dissertation. 2018. Major: Biomedical Engineering. Advisor: Paul Iaizzo. 1 computer file (PDF); 165 pages.The object of this thesis was to investigate applications for monophasic action potential (MAP) recordings in the diagnosis and treatment of cardiac arrhythmias. To meet this objective, MAPs were measured in situ and in vitro, during sinus rhythm and cardiac arrhythmias. MAPs were analyzed for potential clinical applications and in novel cardiac mapping and ablation catheter concepts. MAPs are focal action potential recordings which are directly proportional to the electrical activities of cells adjacent to a contacting electrode. When sufficient force is applied between a contacting electrode and the myocardium, the cells directly beneath become mechanically depolarized; i.e. electrically inactive. As a transmembrane action potential passes through this region, a change in boundary currents between the active and inactive cells, via gap junctions, results in a waveform that is proportional to the original action potential. The Visible Heart® Apparatus provides us with the ability to study large mammalian hearts, including human, in an in vitro setting; allowing the testing of prototype catheter concepts prior to in situ or in vivo work. To validate MAPs from an in vitro working heart model a comparison study was conducted. Over the course of 2 hours in situ and 2 hours in vitro MAPs were recorded from the right atrium, left atrium, and right ventricle (endocardially and epicardially). Overall, there were no significant differences between recorded signals when compared to in situ baseline recordings. Based on these findings, systems like the Visible Heart® Apparatus can be used as a platform on which cardiac action potentials can be studied. The clinical application of MAP recordings, as they pertain to radiofrequency (RF) ablations, was also evaluated. To ensure proper lesion formation, RF ablation requires a catheter contact force (CF) of between 10-20 grams to be maintained throughout energy delivery. It was determined that MAP waveforms could only be recorded when at least 10-15 grams of CF was applied to the myocardium. In other words, the presence of MAP waveforms would indicate that sufficient CF has been applied prior to the delivery of RF energy. Additionally, MAP waveforms were found to correlate with RF lesion size. MAP amplitudes at baseline (pre-ablation) were significantly larger than amplitudes from lesions which matured to greater than 1 mm deep. MAPs were also able to distinguish between lesions between 1-2mm deep, and those deeper than 2mm. Moving forward, MAPs may be used in evaluating cardiac viability, both through recording from induced lesions, as well as in regions of scarred or ischemic myocardium

Stabilization and Resuscitation of Newborns

The majority of newborns do not need medical interventions to manage the neonatal transition after birth. However, every year millions of newborns worldwide require respiratory support immediately after birth, and another considerable number of newborns additionally require extensive resuscitation including chest compressions and drug administration. Despite a significant increase in knowledge and development of enhanced therapy strategies over the past few years, morbidity and mortality caused by failures in neonatal transition remain an important health issue. The purpose of this reprint is to support or introduce novel concepts and add information in the area of the “Stabilization and Resuscitation of Newborns”, aiming to improve neonatal care and, as the major objective, to enhance neuro-developmental outcomes

Project Retrosight. Understanding the returns from cardiovascular and stroke research: Case Studies

Copyright @ 2011 RAND Europe. All rights reserved. The full text article is available via the link below.This project explores the impacts arising from cardiovascular and stroke research funded 15-20 years ago and attempts to draw out aspects of the research, researcher or environment that are associated with high or low impact. The project is a case study-based review of 29 cardiovascular and stroke research grants, funded in Australia, Canada and UK between 1989 and 1993. The case studies focused on the individual grants but considered the development of the investigators and ideas involved in the research projects from initiation to the present day. Grants were selected through a stratified random selection approach that aimed to include both high- and low-impact grants. The key messages are as follows: 1) The cases reveal that a large and diverse range of impacts arose from the 29 grants studied. 2) There are variations between the impacts derived from basic biomedical and clinical research. 3) There is no correlation between knowledge production and wider impacts 4) The majority of economic impacts identified come from a minority of projects. 5) We identified factors that appear to be associated with high and low impact. This report presents the key observations of the study and an overview of the methods involved. It has been written for funders of biomedical and health research and health services, health researchers, and policy makers in those fields. It will also be of interest to those involved in research and impact evaluation.This study was initiated with internal funding from RAND Europe and HERG, with continuing funding from the UK National Institute for Health Research, the Canadian Institutes of Health Research, the Heart and Stroke Foundation of Canada and the National Heart Foundation of Australia. The UK Stroke Association and the British Heart Foundation provided support in kind through access to their archives

Acute lung injury in paediatric intensive care: course and outcome

Introduction: Acute lung injury (ALI) and acute respiratory distress syndrome (ARDS) carry a high morbidity and mortality (10-90%). ALI is characterised by non-cardiogenic pulmonary oedema and refractory hypoxaemia of multifactorial aetiology [1]. There is limited data about outcome particularly in children. Methods This retrospective cohort study of 85 randomly selected patients with respiratory failure recruited from a prospectively collected database represents 7.1% of 1187 admissions. They include those treated with High Frequency Oscillation Ventilation (HFOV). The patients were admitted between 1 November 1998 and 31 October 2000. Results: Of the 85, 49 developed acute lung injury and 47 had ARDS. There were 26 males and 23 females with a median age and weight of 7.7 months (range 1 day-12.8 years) and 8 kg (range 0.8-40 kg). There were 7 deaths giving a crude mortality of 14.3%, all of which fulfilled the Consensus I [1] criteria for ARDS. Pulmonary occlusion pressures were not routinely measured. The A-a gradient and PaO2/FiO2 ratio (median + [95% CI]) were 37.46 [31.82-43.1] kPa and 19.12 [15.26-22.98] kPa respectively. The non-survivors had a significantly lower PaO2/FiO2 ratio (13 [6.07-19.93] kPa) compared to survivors (23.85 [19.57-28.13] kPa) (P = 0.03) and had a higher A-a gradient (51.05 [35.68-66.42] kPa) compared to survivors (36.07 [30.2-41.94]) kPa though not significant (P = 0.06). Twenty-nine patients (59.2%) were oscillated (Sensormedics 3100A) including all 7 non-survivors. There was no difference in ventilation requirements for CMV prior to oscillation. Seventeen of the 49 (34.7%) were treated with Nitric Oxide including 5 out of 7 non-survivors (71.4%). The median (95% CI) number of failed organs was 3 (1.96-4.04) for non-survivors compared to 1 (0.62-1.62) for survivors (P = 0.03). There were 27 patients with isolated respiratory failure all of whom survived. Six (85.7%) of the non-survivors also required cardiovascular support.Conclusion: A crude mortality of 14.3% compares favourably to published data. The A-a gradient and PaO2/FiO2 ratio may be of help in morbidity scoring in paediatric ARDS. Use of Nitric Oxide and HFOV is associated with increased mortality, which probably relates to the severity of disease. Multiple organ failure particularly respiratory and cardiac disease is associated with increased mortality. ARDS with isolated respiratory failure carries a good prognosis in children

The Application of Computer Techniques to ECG Interpretation

This book presents some of the latest available information on automated ECG analysis written by many of the leading researchers in the field. It contains a historical introduction, an outline of the latest international standards for signal processing and communications and then an exciting variety of studies on electrophysiological modelling, ECG Imaging, artificial intelligence applied to resting and ambulatory ECGs, body surface mapping, big data in ECG based prediction, enhanced reliability of patient monitoring, and atrial abnormalities on the ECG. It provides an extremely valuable contribution to the field