Branch vessel cannulation

In the above representative example, the goal of the procedure is to select the small branch renal artery to embolize it to occlude flow to the injured portion of the kidney.

The wire being used is a microwire, only 0.014” in diameter and is only slightly smaller than the branch vessel in question. Selecting this under 2d planar fluoroscopy, our current approach, proved extremely tedious and technically challenging, as the branch is projected in 2d below the larger main branch and required multiple fluoroscopic runs to adequately separate the two enough to get a clear view of the target artery.

Selecting this under xray then consists of repeatedly turning the wire end until it ‘drops’ into the target artery, often this requires trial and error using multiple shaped catheters to deflect the wire end toward the origin of the artery enough to allow the tip to find the opening.

This process consumes a large amount of procedural time, especially in cases of multiple targets for embolization, in addition to using large x-ray doses to both patient and staff.

By using the SFE alongside the wire, we were able to select the branch by steering a shaped wire end under continuous vision without the use of any catheter as we could see where the wire end was actually pointing relative to the branch in 3d. No additional fluoroscopic runs were required to solve the projection issue that proved problematic when using fluoroscopy alone.

Dissection identification/selection/treatment

In the above example, an 0.014” microwire (green) is being navigated through tortuous extracranial carotid circulation.

The wire end has unintentionally entered a subintimal dissection plane due to the forces on the wire around multiple curves from femoral access. This can be identified on fluoroscopy by a change in the shape of the leading wire end and tactile feedback on the wire to the operator. Once the wire is withdrawn back into the true lumen, it can be difficult to avoid re-entering the same dissection plane due to the natural path of the wire through the curved segments.

This is the same mechanism that often leads to abandoning intentional dissection to cross occlusive lesions in the peripheral circulation due to an inability to re-enter the true lumen.

The second figure demonstrates how the dissection can extend rapidly circumferentially and make it very challenging to select the true lumen despite multiple x-ray projections.

By using the SFE alongside the preshaped wire, we were able to identify when the wire was on the cusp of the dissection and direct it around the opening to stay in the true lumen. This edge is completely invisible on fluoroscopy and so the same maneuver relies on trial/error alone presently.  

This angioscopic view also allows for selective stenting of the entry tear (e.g. Tack endovascular stent – Philips), because of the small size of the SFE  we are able to introduce both the stent and SFE alongside each other in the same access, allowing for real-time guidance rather than current fluoroscopic runs which require the system to be removed, a run performed, then the stent re-introduced and placed assuming the anatomy has not changed since the run, an assumption that is likely not valid in mobile segments such as the renal arteries.

Endovascular thrombectomy

In the above example, the distal artery is completely occluded by fresh red clot (A). A microcatheter and stent retriever were used to remove the main plug, with a good xray fluoroscopic result.

Angiography with the SFE showed, however, that there was residual thrombus adherent to the wall (C) so additional directed passes were performed to remove a large amount of residual clot not visible on x-ray imaging due to projection.