The entire coronary arterial system rather than just the culprit lesion should be evaluated in patients with acute coronary syndrome.

he extent of coronary artery narrowing has been considered a primary and readily available determinant of survival in patients with coronary artery disease. Despite continuous refinement in antithrombotic therapy and intracoronary stents, the extent and complexity of coronary artery disease remain major determinants of shortand longterm prognosis in patients undergoing percutaneous coronary intervention (PCI).1 The American College of Cardiology/ The American Heart Association (ACC/AHA) lesion classification scheme is still the most commonly employed lesion classification system worldwide.2 In addition, the development of computer-based quantitative coronary angiographic analysis could provide more precise information of lesion profiles, especially for decision making in PCI.3 Although angiographic assessments focus on individual lesions (mainly the target lesion), a number of patients free from target-lesion revascularization develop major adverse cardiovascular event (MACE), and their prognosis depends on the non-target lesions as well as the target lesions. Therefore, we should evaluate the atherosclerotic burden of the entire coronary arterial system. Based on coronary angiography, several methods have been proposed to score the extent and severity of stenotic lesions of the entire coronary arterial system. These scoring systems have been used not only as a tool for risk stratification but also to evaluate biomarkers for atherosclerosis or to predict cardiovascular events. 4–6