Goal: The aim of this review was to analyze and review the state of the art devices for the endovascular treatment of chronic and acute total occlusions in the different vascular beds (coronary, peripheral, carotid, and intracranial arteries) based on the forces exerted on the occlusion during treatment. Methods: The literature search was executed in the databases of Scopus and Espacenet. Overall, 120 patents and 49 articles have been reviewed and categorized. Results: The identified treatment tools were divided into three treatment modalities: compression, resection, and conversion. A further subdivision was made based on the force direction, i.e., axial, radial, tangential, or energy conversion process (dissolving or state change). Conclusion: The working principles of the identified treatment tools relate strongly to the (biomechanical) properties of the occlusion and environment. In order to increase procedural success, especially in chronic occlusions, the applied force should be increased by applying buckling prevention methods, the penetration force decreased by smart tip design or dynamic loading, and the energy dissipation to the environment minimized. Significance: Insight in the working principles of the treatment tools and their effect on the environment can in future aid designers to overcome current challenges and develop new, innovative treatment tools.@en

Chronic total occlusions (CTOs) represent the “last frontier” of percutaneous interventions. The main technical challenges lies in crossing the guidewire into the distal true lumen, which is primarily due to three problems: device buckling during initial puncture, inadequate visualization, and the inability to actively navigate through the CTO. To improve the success rate and to identify future research pathways, this study systematically reviews the state-of-the-art of all existing and invented devices for crossing occlusions. The literature search was executed in the databases of Scopus and Espacenet using medical and instrument-related keyword combinations. The search yielded over 840 patents and 69 articles. After scanning for relevancy, 45 patents and 16 articles were included. The identified crossing devices were subdivided based on the determinant for the crossing path through the occlusion, which is either the device (straight and angled crossing), the environment (least resistance, tissue selective, centerline, and subintimal crossing) or the user (directly steered and sensor enhanced crossing). It was found that each crossing path is characterized by specific advantages and disadvantages. For a future crossing device, a combination of crossing paths is suggested were the interventionist is able to exert high forces on the CTO (as seen in the device approach) and actively steer through the CTO (user: directly steered crossing) aided by intravascular imaging (user: sensor enhanced crossing) or an intrinsically safe device following the centerline or path of least resistance (environment: centerline crossing or least resistance crossing) to reach the distal true lumen. @en