[Insights provided by new invasive imaging techniques into the biopathology of unstable angina]

Coronary angiography only portrays a silhouette of the vessel lumen. Intravascular ultrasound allows a detailed study of the atherosclerotic plaque on the vessel wall. Intravascular ultrasound is able to determine total vessel area and, therefore, constitutes the technique of choice to analyze coronary remodelling. Alternatively, coronary angioscopy provides direct visualization of the internal coronary surface. Moreover, coronary angioscopy has the unique ability to accurately recognize coronary thrombi. Accordingly, each one of these techniques provide unique and complementary information on the anatomic substrate of patients with unstable angina. In these patients, intravascular ultrasound allows the study of plaque morphology and echogenicity, providing unique insights on its histologic composition. With current technology however, the correlation between plaque characteristics, as determined by intravascular ultrasound, and the presenting clinical syndrome is still weak. Nevertheless, in many cases intravascular ultrasound is able to recognize data suggestive of lipid pools within the plaque, ruptured plaques or findings highly suggestive of coronary thrombi. Again, the diagnosis of thrombus with intravascular ultrasound is still rather limited. On the other hand, in most patients with unstable angina coronary angioscopy is able to visualize irregular yellow plaques with associated red thrombus. Conversely, such findings are uncommon in patients with stable angina. Notably, all this information is not available using angiography and pathologic specimens (atherectomy or necropsy) from patients with unstable angina tend to keep a better correlation with intravascular ultrasound and coronary angioscopy findings than with angiographic data. From the academic point of view, both intravascular ultrasound and coronary angioscopy have revolutionized our understanding of the pathophysiology of acute coronary syndromes and have questioned old paradigms. With this in mind, the information provided by angiography has been revisited and updated. However, from a pragmatic perspective, the major challenge of these new techniques still relies on the demonstration that they may be used to assist in the decision making process involved in the management of patients with unstable angina resulting, eventually, in an improved clinical outcome.