Chronic total occlusions : a guide to recanalization

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Summary

"Chronic total occlusions (CTO) are defined by an occlusion age of 3 months or greater, with angiographic thrombolysis in myocardial infarction (TIMI) flow grade 0 or 11. Our current understanding ...

"Chronic total occlusions (CTO) are defined by an occlusion age of 3 months or greater, with angiographic thrombolysis in myocardial infarction (TIMI) flow grade 0 or 11. Our current understanding of CTO development is based on a limited number of autopsy specimens, imaging studies and animal CTO models. CTO constitute the most challenging lesions in interventional challenge due to the complexity of the composition and the geometric issues, such as CTO entry/exit and the overall occlusion length. In recent years, additional unique features in specific types of CTO, such as occluded native arteries in patients with bypass surgery and stent CTO have been identified. The challenges of CTO PCI have been the impetus for developing unique interventional equipment and strategies, and innovative biologic manipulations2, 3. Human Coronary CTO Studies: Our current understanding of human coronary CTO pathology is based on a small number of autopsy studies. Srivastra et al4, 5 classified angiographic CTOs in 61 patients according to the age of the occlusions (<1 year vs >1 year). The main points were: (1) Angiographic occlusion did not necessarily mean histologic occlusion, with 25% of cases demonstrating antegrade continuity and subtotal occlusion (90-95% obstructed). Severe, but not completely obstructive narrowing, may limit contrast reagent penetration into lesions and thereby overestimate the difficulty of a successful guidewire crossing. This was particularly shown in peripheral arterial "chronic occlusions" in the lower legs6, (2) Hard fibrocalcific plaques are a common feature in all CTOs regardless of age, but there is a definite increase in harder plaques in older CTOs, while softer (mainly lipid and loose fibrous tissue) plaques are more likely to be present in CTOs <1 year old, and (3) Recanalization of the CTO intimal plaques by neovascular channels was commonly observed at all time periods, particularly around prominent collections of inflammatory cells (lymphocytes and macrophages)7 (Figures 1A,B; Figures 2A, 2B)"--Provided by publisher.

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