Document Type

Theses, Ph.D

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This item is available under a Creative Commons License for non-commercial use only

Publication Details

Successfully submitted for the award of Doctor of Philosophy (Ph.D) to the Dublin Institute of Technology 2005.

Abstract

Following an initial pilot study to explore the usefulness of Doppler tissue imaging (DTI) for the assessment of regional systolic dysfunction in the ischaemic heart, new techniques for the diagnosis of diastolic dysfunction have been developed

In the refinement of the techniques further evidence to support the existence of the early diastolic mechanism was obtained prior to assessing its clinical utility. For this the relationship between peak early diastolic mitral ring tissue velocity (EA) as a surrogate for recoil, and the acceleration of early transmitral flow (ventricular filling) was investigated in patients with diastolic dysfunction and in normal subjects. This study supported the existence of recoil as the release mechanism for restoring forces (the early diastolic mechanism) in the normal and its delay or absence in patients with diastolic dysfunction

To confirm the presence, absence or reversal of this early diastolic mechanism to echocardiographic waveforms need to be analysed on the same heart beat. The technique examines the diagnostic utility of the time to peak diastolic tissue velocity (EA) of the mitral ring measured by DTI compared with the time to peak mitral opening measured by M-mode, for the assessment of left ventricular relaxation in subjects with pathological and physiological athletic hypertrophy, and distinguishing these from normals. We postulate that a slack myocardial state occurs within a period between the peak myocardial tissue velocity measured at the mitral valve ring and the peak of the E-wave (M-mode velocity) through the mitral valve. This slack myocardial state constitutes the early diastolic mechanism and allows for proper filling. This mechanism is absent in stiffer hearts.

As well as the early diastolic mechanism a further novel index of left ventricular performance based on the pressure volume relationship, (E/Ea)/LVIDd, was shown to be a promising index for distinguishing the three groups.

Using two ultrasound systems and optimum operating conditions the characteristics of the technique were examined. Finally, further developments of the technique are discussed with possible future clinical applications, particularly to understanding and preventing sudden death in the young athlete

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