Tip detection (TD) IVUS-guided wiring is a highly safe method that enables the successful treatment of difficult CTOs—which would traditionally have required a retrograde approach—using an antegrade approach. It is therefore considered a technique that young physicians entering the field of CTO treatment should certainly master. However, when attempting TD IVUS-guided wiring in practice, one soon realises that success is not easily achieved.
To date, our hospital (Sapporo Cardio Vascular Clinic, Japan) has performed 132 cases of TD IVUS-guided wiring, with a success rate of 85.6% and an average wiring time (the time from insertion of the IVUS into the false lumen until successful wire passage or abandonment of the procedure) of 35.6 minutes. The causes of difficulty or failure vary widely, ranging from anatomical factors such as calcification, lesion tortuosity, and the presence of distal cap bifurcation, to IVUS-related factors such as reduced target visibility due to air or the acoustic shadow of the IVUS-carrying guidewire, and unfavorable guidewire bias. Whilst there are cases where repeated attempts over a long period at the same site fail to yield success, there are also instances where success is easily achieved by successively changing the stick site until an appropriate location is selected. The proficiency of the operator and assistant seems to be the factor that most significantly influences the success rate of TD IVUS-guided wiring.
For this reason, TD IVUS-guided wiring must be performed under the best possible conditions. Coregistration with fluoroscopic images using the ‘Be-the-wire’ technique is a method that reliably enhances the efficiency of TD IVUS-guided wiring. However, IVUS-angiographic co-registration is not straightforward, even when using the ‘Be-the-wire’ technique. I recommend practising two things.
Firstly, during routine PCI procedures, pay close attention to the relative positions of the IVUS transducer and the IVUS-carrying wire on a fluoroscopic image. Look at the fluoroscopic image during IVUS in an actual case and note, for example, that ‘the transducer is on the left and the wire is on the right on the fluoroscopic image’. They are so small and not easy to distinguish. Next, identify which clock-face position on the IVUS screen corresponds to the direction you have been looking at on the fluoroscopic image.
By coregistrating the positional relationship between IVUS and fluoroscopy using the ‘Be-the-wire’ technique, it is possible to identify the location of the true lumen (or plaque) on a fluoroscopic image. For example, if it is known that the target true lumen lies to the left on the fluoroscopic image, even if visibility on the IVUS screen is poor due to calcification or other factors, the wire tip can be directed to the left on the fluoroscopic image, allowing the operator to perform the precision 3D wiring, thereby leading to successful wire crossing.
