RESUMO
Lower extremity chronic total occlusion (CTO) is the most severe manifestation of peripheral artery disease (PAD), with high amputation and mortality rates. As a minimal invasive reconstruction therapy, endovascular therapy (EVT) plays an important role in limb salvage for CTO in current clinical practice. The complexity of CTO lesions leads to a high risk for complications and a low success rate of EVT. Therefore, establishing a grading or scoring system to predict the success rate of revascularization strategy will be helpful in developing appropriate treatment strategies and assessing benefits and risks. This paper summarizes the most popular CTO scoring systems, such as PACSS grading, PARC grading, TAC grading, CTOP classification, Infrapop-CTO scoring, and J-BTK CTO scoring. PACSS grading and PARC grading are suitable for evaluating the severity of vascular calcification including iliofemoral segment, femoral-popliteal segment, and below-the-knee artery segment. TAC grading is suitable for grading calcification below the knee lesions; with low intervention success rate in a high calcification grading. CTOP classification was developed by analyzing the effect of morphological characteristics of proximal and distal fibrous caps of lower extremity CTO lesions on the outcome of EVT. The success rate of antegrade intervention is lower in type IV. The Infrapop-CTO score and J-BTK CTO score can predict successful anterograde crossing of infrapopliteal CTO lesions, with low intervention success rate in high score. Both scoring systems use three variables, namely, shape of proximal stump, calcification, and occlusion length.