Sliding and drilling is usually the initial CTO crossing strategy attempted. Pathologic examination of CTO’s reveal that there are often 160–230 μm vessel channels permeating through the proximal cap that connect the soft less fibrous core of the CTO to the patent proximal vessel lumen [3]. The sliding and drilling technique is an effort to explore the cap for these angiographically invisible microchannels. A polymer-jacketed 0.09 mm tapered tip wire (Fielder XT) with a low tip load (0.8 g) is advanced against the cap with gentle tip rotation in a probing fashion to explore the surface of the cap. Torqueing can be performed with or without a torqueing device, realizing that the wire will rotate much faster when the wire is manipulated directly on its shaft rather than through rotation of torqueing device with a larger radius. If the wire visually progresses through the cap via a microchannel, continued forward wire advancement through the mid portion of the occlusion with the same wire and technique is pursued, with efforts not to push the wire too much to avoid forming a knuckle wire or penetrating the sub-intimal plane. The lack of tactile feedback from the wire tip, especially with tapered-tip low-gram wire such as with the Fielder XT family mandates that the operator utilize the expected course of the vessel in multiple angles of view and observe the appearance of the wire to determine whether successful intraluminal progress is being made. In other words, the wire should be guided with fluoroscopic feedback, not tactile feedback. Once the wire is perceived to be across the CTO and in the true lumen, a sliding without rotation technique can be employed, where the wire is simply pushed with the tip away from the wall. The absence of resistance confirms true lumen positioning.

If sliding is initially ineffective or progression halts once entering the fibrous cap, controlled drilling is typically the next wire handling technique employed. Drilling is accomplished by controlled relatively quick 90° clockwise and counterclockwise rotations of the tip of a stiffer guidewire. Sometimes, operators will prefer to rotate the wire in the same direction. Speed of the rotation will vary upon the use or not of a torqueing device. In the interest of maintaining a simplified wire escalation algorithm, as exposed in Chap. 5, a Pilot 200 with a moderately stiff tip load (4.1 g) is initially utilized. When drilling, the guidewire is typically not pushed hard into the resistant occlusion, but instead, steady engaged contact is maintained between the fibrous cap and the wire tip. The burrowing quality created by the quick clockwise and counterclockwise quarter turns of the wire allows one to search for a soft zone on the surface of the resistant fibrous cap in order to lift a tissue channel to travel through distally. If progress is not made, rather than pushing harder, a stiffer tip load guidewire (12 g) such as a Confianza Pro 12 should be selected with the same technique. Drilling with a Pilot 200 may result in entering the subintimal space between the media and adventitia, but will rarely result in wire exiting the vessel architecture (wire perforation). In contrast, the stiff tip of the Confianza Pro 12 can penetrate the rubbery barrier of adventitia without difficulty and will often freely pass out of the vessel architecture into the pericardial space. Such wire exits are not uncommon and are most of the time of no clinical consequence, as long as antegrade injection or microcatheter advancement is not performed. Indeed, it is mandatory that the operator accurately identify the wire’s distal location, most commonly with contralateral injections, prior to tracking a microcatheter or other equipment over the wire. Failure to accurately do this will convert the usually clinically inconsequential small wire exit perforation into a larger hole that is likely to bleed and result in tamponade.

Not uncommonly, a blunt or heavily resistant calcified cap is encountered and drilling with even the stiffest load tip wires is ineffective at breaching the barrier. In this situation, the operator must transition to a penetration wire handling technique (Fig. 4.2, Video 4.1, 4.2, 4.3, 4.4, 4.5 and 4.6). Penetration is accomplished with a Confianza Pro 12, which is the stiffest, highest tip load guidewire (12 g) currently available for coronary intervention. This technique consists of pointing the wire in the desired direction, and advancing it forward without rotation, but instead using the guidewire in a needle-like fashion. The tapered (0.09 mm) stiff tip combined with a hydrophilic coating gives the operator the maximum penetration when attempting to puncture the proximal cap. If the wire stops making progress, gentle drilling will help to track a different tissue plane and a penetration wiring technique can be resumed. In general, most wires will make faster progression with a combination of push and rotation. Keeping the microcatheter close to the tip of the wire when attempting a penetrating strategy can increase the tip load of Confianza Pro 12 to up to 60 g. This maximizes the penetrating power to the occlusion cap, but also increases the likelihood of perforating the vessel sidewall. Multiple angiographic views in order to confirm wire position, or exploring the wire path created by the Confianza Pro 12 with a wire less likely to leave the vessel architecture such as a Pilot 200 (wire ‘de-escalation’) are necessary prior to safely tracking equipment over the wire.