CTO PCI begins with a careful reading and analysis of the coronary angiographic images, which in most cases require bilateral imaging. Then the operation plan should be developed based on the image characteristics of coronary angiography, and a certain degree of flexibility of randomization should be maintained once the initially selected passage strategy fails. At present, there are three main strategies for opening CTO lesions: 1, anterior guidewire escalation method; 2, anterior to the false lumen/return to the true lumen method; 3, via the reverse pathway opening method. 1, Forward guidewire escalation method The forward guidewire escalation method is the most commonly used CTO opening strategy. The microcatheter is first delivered to the proximal end of the occluded lesion, and then various guidewires with different characteristics are tried. Currently, the most commonly used initial guidewire is a softer polymer-coated wound guidewire (e.g., Fielder XT ), and after failure, a stiffer polymer-coated guidewire (e.g., Pilot 200) or a stiffer wound guidewire (e.g., Confianza Pro 12, Asahi Intecc) is used. More recently, stiff guidewires with composite cores (Gaia first, second, and third, Asahi Intecc) have been introduced into clinical use, which have increased the rate of vessel opening due to better maneuverability, but with a slightly different maneuvering technique that involves a slow rotation in order to transfer good torque from the proximal end to the distal end of the guidewire. Accurate judgment of the position of the tip of the guidewire is the key to increasing the success rate and reducing complications, and the position of the guidewire can usually be judged by bilateral coronary angiography. If the two perpendicular positions confirm that the guidewire has entered the true lumen of the distal vessel, the microcatheter can be sent forward through the occluded segment to exchange the common working guidewire, and then the balloon dilatation stent implantation can be accomplished in a single step. If the guidewire is found to be outside the vessel, it must be retracted and then the direction of advancement must be adjusted. If the guidewire passes through the occluded segment and then enters the subendothelium, it can be returned to the true lumen of the vessel by using the “parallel guidewire” technique or by applying the return-to-true-lumen system (Stingray balloon and guidewire, Boston Scientific), which is more commonly used in North America today. Anterior vascular entrapment and reentry into the true lumen Anterior vascular entrapment and reentry into the true lumen refers to the intentional use of a subendothelial false lumen to open chronic occlusive lesions in the coronary arteries. This technique was first introduced to clinical practice by Antonio Colombo, MD, FACC, initially by advancing a curved-knee guidewire under the intima until it reentered the true lumen of the distal vessel (subendothelial tracing and re-entry of true lumen [STAR] technique). Various modifications of the STAR technique have been developed, but the biggest problem is the high rate of restenosis and reocclusion. Therefore, this technique is currently used only as a last resort after other techniques have failed. Restricted reentry strategies appear to have relatively better immediate and long-term outcomes.The CrossBoss catheter is an OTW catheter with a rigid blunt metal head rounded to allow the distal head to rotate at high speeds (“fast spin” technique) by torque provided by the proximal device to penetrate an occluded coronary lesion.The CrossBoss catheter can be used in one-third of cases to penetrate occluded coronary lesions. In one-third of cases, the occluded segment can be passed into the distal true lumen, and in the remaining two-thirds of cases, a restrictive sandwich can be created to provide a maneuverable platform for reentry into the true lumen. Reentry into the true lumen can be accomplished with the Stingray system (Boston Scientific), a slightly flattened 1-mm balloon with a common central lumen and three outlets, the distal outlet for anterior delivery of the balloon to its destination, and two outlets that are angled at exactly 180 degrees in opposite directions, with different distal and proximal locations. Due to the shape of the balloon, one outlet faces the true lumen and the other outlet faces the tunica albuginea as the balloon fills the vessel’s lumen.The Stingray guidewire is a rigid, pre-shaped guidewire, 0.0035 inch in diameter, that is threaded into the true lumen of the vessel through the true lumen-facing outlets.The reintroduction of the Stingray guidewire into the true lumen is usually followed by replacement with a more maneuverable guidewire (“stick andswap” technique).The Stingray guidewire has a common central lumen and three outlets. After reentry of the Stingray guidewire into the true lumen, it is often necessary to replace the guidewire with one that is easier to maneuver (“stick andswap” technique) (e.g. Pilot 200, Abbott Vascular). The reverse route, in which the guidewire is delivered to the distal portion of the occluded vessel through a bridge vessel or collateral vessel and then passes proximally through the occluded lesion in the direction of the original blood flow, has significantly increased the success rate of vascularization of CTO lesions (especially in difficult and challenging cases). The distal fibrous cap is relatively soft compared with the proximal end of the occlusion, and its morphology tends to be tapered. Clinical preference is given to bridging vessels or septal branch collateral vessels because of their ease of passage and their lower risk of pericardial tamponade once the vessel has been penetrated, with epicardial vessels as a second choice. By choosing specially designed microcatheters (e.g., Corsair, Asahi Intecc, and Turnpike, Vascular Solutions) and guidewires, such as composite core guidewires (Sion, Asahi Intecc) and soft hydrophilic polymer-coated guidewires (Fielder FC, Asahi Intecc. Pilot 50, Abbott Vascular). Once the guidewire’s entry into the true lumen of the distal vessel has been confirmed by imaging, the guidewire can be threaded into the CTO lesion using a sequential climb and reentry method, which antefeeds the microcatheter into the distal cap and subsequently through the CTO lesion. Currently, the technique for reentry into the true lumen is the positive opposite of the forward one, i.e., the forward-controlled reverse guidewire subendothelial pathfinding technique (reverse CART), which is operated by delivering a suitable balloon along the anterior guidewire to the subendothelium and dilating it so as to enlarge the subendothelial false lumen, and then anteriorly delivering the reverse guidewire to enter the true lumen of the proximal segment of the vessel through the false lumen created by the anteriorly oriented balloon. The retrograde guidewire and microcatheter are then delivered into an orthogonal guiding catheter and subsequently retrogradely delivered outside the body, a process that has recently become more successful with the advent of the RG3 guidewire on the market. The retrograde delivery of the guidewire to the outside of the body can result in deep insertion of the guiding catheter and lead to complications, so care should be taken to keep the guiding catheter moderately away from the coronary orifice.