Virtual histology and optical coherence tomography: from research to a broad clinical application

Invasive coronary imaging techniques have improved our understanding of atherosclerosis and helped us to evaluate the effectiveness of new drugs and new intravascular devices. We have adopted and integrated them rapidly into our clinical decision making process in the catheterisation laboratory. So far, only significant lesions in the coronary angiogram have been treated either by percutaneous coronary intervention (PCI) or coronary bypass artery grafting (CABG), while normal looking coronary segments in angiography have been regarded as “disease-free”, and mild/moderate stenoses as “non-treatable” by PCI or CABG; from these non-significantly diseased areas, acute coronary events may potentially arise. In response to this, many imaging coronary techniques have been developed to study these areas in order to understand better the pathophysiology of atherosclerotic disease and to assess the performance of medical interventions that may ultimately have an important impact on the prevention of acute myocardial infarction and death. Grey scale intravascular ultrasound (IVUS) has been so far the most useful invasive imaging technique. Using grey scale IVUS, some lipid lowering drugs have been shown to decrease plaque size, and as a result these drugs have been widely included as part of standard of care.w1 w2 Moreover, IVUS guided stenting, following strict criteria of implantation, has been proven to decrease the restenosis ratew3 and more recently it has been published that this approach apparently decreases stent thrombosis.w4 The recent introduction of tissue characterisation by means of radiofrequency data analysis (virtual histology, VH) has offered a more detailed evaluation of the atherosclerotic plaque. This technique brings the possibility of going beyond plaque size evaluation to a more sophisticated approach which is to assess changes in tissue types. In the IBIS 2 study,1 after 12 months and despite high adherence to standard-of-care treatment, the necrotic core continued to expand among patients …