Intravascular ultrasound (IVUS) is a relatively new method of imaging coronary arteries
which has several advantages over contrast angiography in the accurate quantification of
coronary lumen and vessel dimensions and assessment of atherosclerotic plaque.
Experimentally, IVUS has so far provided detailed insights into the distribution and
composition of atheroma in the coronary circulation and its behaviour when subjected,
particularly, to balloon dilatation. The technique is now regarded as a useful adjunct to
angiography in the routine assessment of patients with atherosclerotic coronary disease as
well as in the guidance of percutaneous coronary interventional techniques such as balloon
angioplasty and intracoronary stent implantation. Additionally, the concept of three-dimensional reconstruction of IVUS images has recently been realized providing the
opportunity for longitudinal as well as tomographic analysisDespite the wealth of information so far provided by IVUS most in vitro studies require
cautious interpretation due to well-recognised limitations of studying animal models of
atherosclerosis or human coronary disease in circumstances that do not accurately reflect the
clinical setting. This thesis is based upon the development of a pulsatile flow system which is
capable of accurately reproducing some of the important physiological properties of in-vivo
flow in normal and diseased coronary arteries. Some characteristics of in-vivo coronary
blood flow cannot be met, such as the effect of blood viscosity and extrinsic compression of
the vessel by the beating heart. However, the system is designed to enable the study of
human coronary atherosclerotic disease by IVUS in conditions which closely resemble those
seen in the clinical setting. The initial chapters provide an overview of IVUS, including
methods and rationale for three-dimensional reconstruction, and describe the development
and validation of the flow system. Chapters 3 and 4 assess the qualitative accuracy of IVUS
in the assessment of the composition of atherosclerotic plaque and also the reproducibility of
IVUS assessments of vessel and lumen dimensions in diseased coronary arteries. There
follows a study of coronary balloon angioplasty designed to assess the influence of
procedural factors, such as balloon calibre and inflation pressure selection, and IVUS
guidance on the initial success of the procedure. In the remaining chapters two studies
examine three-dimensional reconstruction of IVUS images and the influence of technical
factors, which are inherent in IVUS imaging, on the accuracy of atherosclerotic plaque
volume measurement and its use in assessing vascular injury following coronary balloon
angioplasty. It should be emphasized that all patient donors died from causes other than
cardiovascular disease such that the histopathological studies involved the use of coronary
artery specimens which were not required for diagnostic purposes. The studies adhered to
strict ethical standards of the day. Harvesting of specimens received ethical approval as part
of the overall IVUS research programme being undertaken at the time. All specimens were
retained by the Department of Pathology during the study period and disposed of
appropriately following the final analysesTaken together these studies have helped to provide further insights into the quantitative and
qualitative accuracy of IVUS in the assessment of coronary atherosclerosis and the technical
factors which may confound these analyses. Furthermore, the value of IVUS in guiding, and
assessing the outcome of, coronary balloon angioplasty is clearly demonstrated. Given the
close correlation of the studies to the clinical setting the findings should be expected to
influence our approach to clinical IVUS studies and utilize the technique more frequently in
the guidance of percutaneous coronary intervention
