Use this URL to cite or link to this record in EThOS:
Title: An investigation into the assessment and optimisation of cardiac dyssynchrony at rest and stress
Author: Beynon, Rhys
ISNI:       0000 0004 2685 0548
Awarding Body: The University of Manchester
Current Institution: University of Manchester
Date of Award: 2009
Availability of Full Text:
Access from EThOS:
Heart failure remains a significant cause of morbidity and mortality despite the introduction of new medication. Over the last 10 years attention has focused on improving the mechanical action of the heart using biventricular pacemakers to retime hearts that are thought to be dyssynchronous. Cardiac resynchronisation therapy (CRT) has now been shown to improve morbidity and mortality in a selected population although up to 30% of patients fail to respond. Attention is now focused on improving outcomes in the 'non responders', optimising patient selection and potentially extending the number of patients who might benefit from CRT. Echocardiography may improve patient selection but results have been variable. This thesis attempts to assess the reproducibility of echocardiographic measures of dyssynchrony to see if current tools are fit for purpose. The dual chamber pacemaker population are potentially a group that may benefit from CRT. This thesis will assess the prevalence of dyssynchrony in the normal and dual chamber paced population both at rest and during increased heart rate to ascertain if dyssynchrony is a significant underlying problem. CRT attempts to retime the heart using up to 3 pacemaker leads. It is possible to alter timing of individual lead depolarisation so as to optimise the heart. This thesis compares three tools used for optimisation; echocardiography, thoracic impedance and beat to beat blood pressure (BP), focussing on their reproducibility during optimisation. The thesis examines whether optimisation in the BIV population changes from rest to stress as this may explain the failure of response to CRT in some patients. The thesis concludes that current echocardiographic measures of dyssynchrony, including tissue Doppler imaging, are poorly reproducible and they should not be used for CRT selection. Thoracic impedance appears to be a reliable tool that could be used for CRT optimisation and its simplicity may allow optimisation to be extended to a larger group of individuals. Echocardiography using continuous wave Doppler remains a useful tool for optimisation but pulsed wave Doppler should not be used. Optimisation appears to change significantly from rest to exercise within individuals and further work is needed to discover if this can improve patient outcomes.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (M.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available