This report is the first description of the “DIOL” fashion with hydraulic pressure through a microcatheter to expand and modify CTO lesions to facilitate guidewire crossing. This technique applies hydraulic pressure of tip injection with a contrast media through a microcatheter or an over-the-wire balloon within CTOs. The purposes of this technique are 1) to visualize the “vessel road” of the occlusion by expanding microchannels, and/or subintimal, intramedial, periadventitial space with contrast agent and 2) to modify and prepare plaques within CTO by hydraulic pressure to advance CTO devices safely and easily. The effectiveness of hydraulic pressure to crack calcifications, named the “Fracking” technique, have already been reported (Haraguchi T. 2021). The DIOL is a procedure which can be performed from antegrade and/or retrograde approach and feature with creating dissections by hydraulic pressure. Contrast-guided subintimal tracking and re-entry (STAR), microchannel technique, and Carlino technique have already been developed as the contrast modulation techniques for difficult-to-cross CTOs in the coronary field (Azzalini. 2018). However, the vascular pathology and lesion characteristics in patients with coronary artery disease are different from that in PAD patients. Therefore, we should develop the appropriate approaches for PVI. Antegrade-DIOL may create dissections which extend to and compress it, especially in BKA. Hence, a gentle tip injection with smaller contrast volume (1-2 ml) should be used to confirm the tip positions which is inside or outside a vessel. On the other hand, retrograde-DIOL is used with forceful tip injection with the moderate contrast volume in up to 5-ml to visualize the vessel track and modify the plaque to facilitate CTO devices crossing. In any case, we should start a gentle injection and gradually increase the pressure while confirming the response of the lesion to the injection. We should determine the way of tip injection according to the purposes of DIOL.
The hydraulic pressure effect by DIOL varies among the four positions of a microcatheter tip: intima, subintima, intramedia, and periadventitia (Fig. 1). An injection in intimal plane shows microchannel routes which is tiny and relatively straight without persisting contrast stain (Fig. 1a). A “tubular” dissection results from an injection in subintimal space with a contrast stain (Fig. 1a, b). A vasa vasorum, a venous vasa vasorum, and veins which are connected among them are occasionally seen by a forceful injection in subintima (Fig 1b). An injection in intramedial plane reveals a “river” dissection (Fig. 1c). A “cloudy” contrast stain as extravasation is caused by an injection in periadventitial plane (Fig 1d).
Here are two cases treated by the DIOL fashion. Case-1 involved a 66-year-old male with severe claudication due to right superficial femoral artery (SFA) occlusion (Fig. 2a). Several antegrade guidewires from a 6-Fr crossover sheath only reached to the proximal CTO. A retrograde guidewire with a microcatheter inserted from distal SFA was advanced into the middle aspect of CTO, but not further. Therefore, we performed the retrograde-DIOL with a forceful tip injection from the retrograde microcatheter, and a tubular dissection with a vessel road became visible (Fig. 2b). The retrograde guidewire was successfully advanced further. We attempted reverse controlled antegrade and retrograde tracking and dissection (CART), but re-entry failed. Retrograde-DIOL was reperformed to expand the subintimal lumen and penetrate into the proximal lumen. We confirmed the connection between the lumens created by reverse-CART and retrograde-DIOL (Fig. 2c). The retrograde guidewire successfully passed the route and was advanced into the guiding sheath to achieve guidewire externalization. After two drug-eluting stents deployment, a satisfactory result was obtained without complications (Fig. 2d). Restenosis, reintervention, and amputation have not occurred two years after the treatment.
Case-2 involved an 83-year-old male with refractory multiple ulcers in his left heel due to BKA occlusions (Fig. 3a). Antegrade wiring for posterior tibial artery (PTA) occlusion reached distal aspect of CTO, but the crossing failed. Trans-collateral approach as retrograde approach from dorsalis pedis artery through medial lateral artery to PTA was achieved (Fig 3b, c). The distal CTO prevented retrograde guidewire advancement. Therefore, retrograde-DIOL was used to reveal the position of retrograde microcatheter, visualize a vessel road, and modify the CTO plaque (Fig. 3d). Then, a retrograde wire successfully crossed and was advanced into the sheath to achieve guidewire externalization. After balloon angioplasty, the direct blood flow to the wounds was obtained (Fig. 3e). The wounds heeled four months after the procedure without reintervention.
Here are the limitations. First, the DIOL will not be applied if a tip of microcatheter or over-the-wire balloon following the guidewire cannot be inserted into CTO. Second, the residual contrast media around the lesion makes the angiographical image difficult to see. We should consider it as an additional treatment option when conventional procedure failed.