The role of positron emission tomography

Abstract

The link between myocardial ischemia and obstructive atherosclerosis of the epicardial coronary arteries is well established, and coronary angiography has demonstrated a relationship between the severity and extent of coronary artery disease (CAD) and survival. In the past 20 years technological advances in positron emission tomography (PET) have enabled the noninvasive measurement of absolute (ml/min/g) myocardial blood flow (MBF) and flow reserve. In the absence of detectable CAD, a reduced maximum MBF and CFR can be ascribed to coronary microvascular dysfunction. PET MBF studies have contributed significantly to the understanding of the pathophysiology of chest pain in patients with angiographically normal coronary arteries. These studies have highlighted the role of coronary microvascular dysfunction as a potential mechanism of myocardial ischemia in many conditions, from patients with risk factors for CAD to those with myocardial diseases. Quantification of absolute MBF with PET can be used clinically to demonstrate coronary microvascular dysfunction and how treatment can improve the function of the small coronary vessels. Therefore, the use of the term cardiac syndrome X to describe patients with chest pain and normal coronary angiograms is probably inappropriate in most cases and should be confined to those cases where no obvious risk factors for coronary microvascular dysfunction can be demonstrated.