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Title: Limitations to Exercise in Congestive Heart Failure: Insights from Peripheral and Transcranial Magnetic stimulation
Author: Dayer, Mark
ISNI:       0000 0001 3419 7583
Awarding Body: Imperial College London
Current Institution: Imperial College London
Date of Award: 2008
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The aims of the experiments in this thesis were to describe and further understand changes that occur in patients with heart failure after exercise. The first chapter outlines the pathophysiology of heart failure and why the motor system, from the central nervous system to the muscles, may be important in the generation of symptoms and possibly the generation of the syndrome. It also lays qut the hypotheses that guided the work in this thesis. Chapter two explains the methodologies used. Chapters three and four describe the impact of exhaustive cycle exercise on respiratory muscle and quadriceps muscle function of patients with congestive heart failure (CHF). In chapter three, 12 patients and 13 control subjects were studied. Diaphragm contractility as determined by the twitch transdiaphragmatic pressure did not fall significantly. There was no evidence of low frequency diaphragm fatigue. In chapter four, 10 patients and 10 control subjects were studied. There was significant evidence of low frequency quadriceps fatigue after exercise, which was slightly, but not significantly, more marked in the normal subjects. Having studied the principal muscles of breathing and cycling, I went on to consider the impact of heart failure on the central nervous system. Transcranial magnetic stimulation (TMS) is a technique that is well established for studying cortical excitability and a small number of studies have documented changes in motor cortical excitability after exercise. Two��?���· studies on healthy volunteers are described in chapter five which not only confirmed that we could successfully induce these changes at lower workloads (more comparable to the workloads that subjects with CHF might be expected to attain), but also suggested that the changes induced were more related to total body work done, rather than the work of an individual muscle group. Building on these��?���· studies I went on to study the impact of exhaustive cycle exercise on patients with 9HF. 10 patients and 10 healthy age-matched control subjects were studied. The data suggested that, by some measures, central fatigue was not induced and that changes in cortical excitability, although present, were less marked in those with CHF compared to control Subjects. Pot~ntial reasons for this are explored. The final chapter brings together the' findings and suggests. future avenues for research. A number of appendices are attached; inclUding the' custom-written software to analyse exercise tolerance tests and the work of breathing, the two papers published so far from this work and an abstract presented at the European Society of Cardiology in 2005.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available