Ruptured plaque

Although the value of coronary angiography remains unquestioned, investigations have revealed many deficiencies inherent in this approach. Intravascular ultrasound (IVUS) has several important advantages over contrast angiography. The tomographic orientation of ultrasound enables visualization of the entire circumference of the vessel wall. Intravascular ultrasound can interrogate tissues beneath the luminal border and provides the cardiologists with a true look “inside the artery” to clarify plaque subtypes, vessel size (not only lumen), dissection, and various other entities. Coronary artery aneurysms are detected with increasing frequency (4.9%) because of the routine use of coronary angiography in the diagnosis and management of coronary artery disease [1], with the prognosis depending on the morphology of the aneurysm or the presence of coexisting obstructive disease [2]. Using intravascular ultrasound in this clinical situation allows detailed characterization of coronary aneurysms. Although ruptured plaque was initially found in patients with acute coronary syndrome, IVUS studies have shown that plaque rupture also occurred in patients with stable angina or no symptoms. Several IVUS studies have demonstrated that ruptured plaque consists of a certain percentage of cases believed to be aneurysms on angiography. In 3 (21%) of 14 patients with angiographic signs of coronary aneurysm, these signs were found to be ruptured plaque with an emptied plaque cavity on IVUS [3]. Another IVUS study has shown that 16% of 77 native coronary aneurysmal lesions were classified as complex plaques (ruptured plaque or spontaneous or unhealed dissection) in patients with coronary artery disease [4]. On the contrary, 15 lesions (7%) of 225 of lesions with ruptured plaque were categorized as aneurysm on angiography [5]. Processes involved in their pathogenesis overlap [6]. Proteolysis is involved in both processes, although elastolysis seems more important in aneurysm formation, whereas collagenolysis is more important in plaque rupture. However, differentiating ruptured plaque from aneurysms is still of clinical importance, because thrombotic complications that arise from ruptured plaque may be clinically silent yet contribute to the natural history of plaque progression and, ultimately, luminal stenosis [7]. Despite the emergence of noninvasive technology (computed tomography and magnetic resonance imaging), IVUS is still the only clinical tool to differentiate ruptured plaque from aneurysms. In the present issue of Catheterization and Cardiovascular Interventions, Li et al. confirmed the utility of IVUS in the most important differentiation. Another important aspect in this context is pan-coronary vulnerability [8]. Several investigators have noted the presence of more than one vulnerable plaque in patients at risk of cardiovascular events. Multiple ruptured plaques were observed using IVUS [9,10]. In this context, IVUS detection of ruptured plaque may offer the opportunity to identify patients in whom disruption of a vulnerable plaque is likely to occur and result in a clinical event. Widespread inflammation [11] and multiple sites of plaque disruption highlight the importance of systemic therapy as the ideal form of prevention. However, systemic lipid-lowering and anti-thrombotic therapy falls short in preventing events. Although optimal treatment is still unknown, drug-eluting stents have the potential to stabilize vulnerable plaque by reducing lipid accumulation and increasing fibrous cap thickness, leading to prevention. Interventionists benefit from the additional information acquired from inside the artery, together with the road map of the angiogram, to optimize individual treatment for coronary artery disease. In the era of drugeluting stents, intravascular ultrasound may have an increasingly important role in clarifying the nature of atherosclerosis and provide new therapeutic insights for coronary disease.