Scope of emission tomography for assessment of myocardial viability in patients with coronary artery disease

This thesis deals with the clinical and difficult problem of identifying viable myocardium in patients with coronary artery disease and chronic wall motion abnormalities that may improve after coronary revascularization. Assuming that viable myocardium is chronically hypoperfused, "hibernating myocardium", and with reduced wall motion properties, we attempted to investigate the predictive power of pre-revascularization status of flow and glucose metabolism using positron emission tomography techniques in myocardium at risk that would be able to improve after restoration of the coronary circulation. This thesis aims to further assess the pathophysiology of hibernating myocardium using emission tomography. For this purpose, absolute measurements of regional myocardial blood flow in ml/min/g and metabolic rate of glucose utilization in μ/min/g during hyperinsulinaemic euglycaemic clamp, using positron emission tomography was performed. One hundred patients with hibernating myocardium were studied. All patients underwent radionuclide ventriculography before surgery and thirty before and after surgery. These thirty patients with follow-up scans will be the object of the present study. Control values for myocardial blood flow and metabolic rate of glucose utilization were obtained respectively in twenty five and nine age matched normal volunteers. This thesis is composed of eight chapters. The first four chapters review the available literature dealing with similar problem, myocardial viability definition, regulatory mechanism of coronary blood flow and methodology available to study hibernating myocardium, particularly positron emission tomography in chapter five the materials, subjects and methodology, as well as protocols employed in this thesis are described. Chapter six describes all the results pointing to the predictive accuracy of positron emission tomography measurements of flow and metabolism in determining viable myocardium pre-myocardium. Chapter seven discusses these results in the light of available literature and state the main conclusions. Finally, some thoughts for further research in the subject are exposed