We encountered a case of severe critical limb ischemia involving a long occlusive vessel from the ostium of the CIA to the distal part of the SFA. The vascular lumen around the CFA was partially patent and the DFA supplied very low-level blood flow distally to the collateral vasculature. In the first session of EVT, we were able to pass a guidewire antegradely, as far as the CFA and deployed self-expandable stents in the iliac artery. Although we tried to further advance the guidewire into the occluded SFA, the maneuverability of the guidewire with a left brachial approach was restricted due to strong friction of the long vascular route, and we finally failed to penetrate the occluded SFA. We initially expected the blood flow distally from the DFA, which supplied the collateral vasculature, to be sufficient to improve blood flow in the recanalized iliac artery. However, contrary to our expectation, we achieved an insufficient blood stream with flow delay in the iliac artery due to the poor vascular bed distal to the CFA. At the second session of EVT two days after the first one, the iliac artery exhibited in-stent occlusion with fresh massive thrombi. This time, the guidewire could pass through the occluded SFA as far as the popliteal artery due to good guidewire maneuverability via a left femoral approach.
However, we had to overcome the critical issue of how to treat the massive thrombi that were subacutely generated in the stents that had been deployed in the iliac artery just two days previously. Distal thromboembolism during EVT is a major concern due to potential serious ischemic consequences. In-stent and complex native lesions are considered as higher risks for distal thromboembolism during EVT for lower extremities (
1). However, this phenomenon is typically reversible with EVT procedures and has been reported to have no significant effect on patency rates or limb salvage. Embolic protection devices can be categorized to three different systems based on their mechanism of action during EVT on various lesions and scenes: flow preservation devices ( 2), distal balloon occlusion devices ( 3), and proximal protection devices ( 4). There are pitfalls and advantages inherent to each protection device system ( 5).
In our case, we wanted to establish a system to protect against thromboembolism. There have been several reports about the usefulness of the Optimo
® balloon-tipped occlusion catheter (Tokai medical products, Inc., Aichi, Japan) for preventing distal thromboembolism during EVT ( 3). However, this catheter was not available at our institute at that time of the procedure, and so we decided to establish a system similar to the Optimo ® catheter. Because the lumen diameter of the distal EIA was about 6 mm from the IVUS findings, we delivered a 4.0-mm balloon catheter from the left groin to obstruct the vascular lumen in the right EIA by trapping side by side with an 8 Fr-sheath inserted from the right groin for the purpose of aspirating the thrombi. When simultaneously deflating and retrieving a balloon catheter with a 6.0-mm diameter from the 8Fr-sheath, we strongly aspirated from the sheath port. This technique effectively resulted in prevention of distal thromboembolism and avoidance of additional stent deployment to seal the mural thrombi in the iliac artery.
In this report we demonstrate a schema of the embolic protection system developed in this case (
Figure 4A). Unlike the Optimo ® catheter, which has a specification that the sheath and occlusion balloon share the same axis, those two components run along side by side in the artery in our method ( Figure 4B, C). Because of this characteristic, this system cannot completely occlude the vascular lumen. However, we could confirm the stasis of blood flow, and no clinical problematic thromboembolism occurred after the procedure. When using distal balloon occlusion devices, vessel mismatch is one of the most important problems. The target artery is occasionally too large for the distal occlusion balloon to be occlusive. Particularly with our method, determining the size and inflation pressure of the occlusion balloon was relatively difficult. A larger sized balloon or a higher pressure of balloon inflation can more effectively occlude the target artery, yet this involves the risk of causing deformity of the aspiration sheath ( Figure 4D, E). We found that to inflate an optimal sized balloon catheter with a lower pressure is the most useful for this technique ( Figure 4B, C), because the minimum inflation of the occlusion balloon is thought to be sufficient to exert a sufficient space-occupying effect in the artery and also cause minimal deformation of the aspiration sheath.
Figure 4. Panel A, a schema of the embolic protection system devised for this case; panel B - E, a replication test was performed to examine the relationship between the occlusion balloon catheter and aspiration sheath in the vessel model. The occlusion balloon with a 4.0-mm diameter was inflated with different pressures (B, C: 4 atmospheres; D, E: 12 atmospheres) side by side with an 8Fr-sheath inside the vessel model with a 6-mm inner lumen size. The short axis view (B, D). The long axis view (C, E).
One of the shortcomings of this system was considered to be that delivering the occlusion balloon catheter involves risk of distally scattering of thrombi while antegradely passing through the thrombosed lesions. However, we think that the risk is not very critical because the iliac artery has a large vessel diameter. Moreover, arterial dissection and vasospasm are the most common complications seen using distal balloon occlusion devices. In this regard, an optimal sized balloon catheter with a lower pressure is recommended.
Here, we demonstrated a very simple but possibly very useful distal protection system when treating massive thrombotic lesions in the iliac artery. Although various EVT devices and techniques have since been developed, little tips and tricks during EVT procedures are sometimes markedly useful. Because many devices are often required for the completion of complex EVT procedures, it is important to minimize the total number of EVT devices used in order to reduce medical costs in practical settings.