Treating Limb Ischemia Secondary to Thrombosed Popliteal Artery Aneurysms

Editor's Corner

Submitted on Fri, 10/19/2018 - 09:50

Craig WalkerHello, and welcome to the October edition of Vascular Disease Management. There are multiple interesting submissions, including an editorial on renal denervation utilizing a completely different interventional route than previously described, but I have chosen to comment on Dr. Halim Yammine and colleagues’ case report in which a thrombosed popliteal artery aneurysm was treated via interventional means in an elderly patient who had previously failed surgical therapy secondary to graft infection.

This case illustrates the complexity of interventional treatment of limb ischemia secondary to thrombosed popliteal artery aneurysms and it showcases some of the essential devices required to achieve a successful outcome.

The authors of this case submission cite the incidence of popliteal artery aneurysm in the general population. This abnormality is far more prevalent in males (approximately 20:1 preponderance). Popliteal artery aneurysms typically become symptomatic secondary to thrombosis and embolization rather than rupture.

Essential to the interventional treatment of occluded popliteal artery aneurysms is the ability to cross the occlusion, to remove thrombus, to establish arterial outflow to the foot, and finally to place appropriately sized self-expanding stent-grafts.

Crossing occluded popliteal artery aneurysms (particularly those that are large and angulated) is the initial challenge in interventional treatment. Optimal angiographic imaging is essential and occasionally external duplex ultrasound may assist in guiding the guidewires to cross the occlusion to facilitate delivery of treatment devices. Crossing requires skill and persistence.

Once the occluded aneurysm segment has been crossed, clot removal from the aneurysm and the outflow vessels is essential. The interventional treatment of thrombus can roughly be divided into three groups: (1) direct mechanical removal; (2) thrombolytic infusion; and (3) a combination of both mechanical removal and lytic drug. Mechanical removal of thrombus can remove thrombus quickly with low risk of bleeding complications, but doesn’t always remove the entire thrombus burden and may result in embolization.

Lytic infusions are highly effective in effecting dissolution of thrombus, but are associated with the risk of major bleeding (particularly in elderly and hypertensive patients), the need for intensive care observation, and a delay in the time to reperfusion.

Combining lytic with mechanical devices may lessen the time to perfusion, lessen bleeding risk, and avoid the need for prolonged intensive care observation. In the reported case, a single bolus of 5 mg tissue plasminogen activator (tPA) was administered into the distal vasculature following crossing of the aneurysm. Following this, vacuum-assisted clot removal utilizing several different-sized Penumbra devices was successful in removing thrombus and establishing flow.

The family of Penumbra clot removal devices couple large-lumen catheters to which constant negative pressure is applied and a movable distal macerator device to break clot into smaller sizes, allowing steady clot aspiration which would otherwise be obstructed by large particles. This allows more effective thrombus removal and decreases the risk of distal embolization. The Penumbra devices are available in several sizes, with the larger iterations designed to be utilized in larger vessels.

Once clot removal has been achieved from the popliteal artery, then arterial outflow must be established. This may require additional clot removal from the infrapopliteal arteries or it may require angioplasty or stenting to open the occluded arteries. Often, both treatments are required. Outflow is crucial not only to perfuse the foot, but to ensure patency of the subsequent stent-graft, as low-flow may result in stent-graft thrombosis.

The final step in treatment is the placement of a self-expanding stent-graft that is large enough to exclude the aneurysmal segment and achieve an adequate seal, but not more than 20% larger than the size of the normal reference vessel, as over-sizing results in higher rates of edge restenosis and subsequent graft occlusion. The graft should always be carefully postdilated to ensure creation of an optimal lumen while avoiding edge dissection. Some interventionists will perform final angiography with the knee bent to ensure there is no evidence of graft kinking.

As with any surgical or endovascular graft, careful ultrasound surveillance with repeat intervention if there is evidence of edge restenosis should be utilized. It is important to note that stent-grafts do not have formal FDA approval for the treatment of popliteal artery aneurysms, but have been utilized in unique situations such as this reported case where other options are limited.

The treatment of occluded popliteal artery aneurysms is profoundly challenging. Open surgical and endovascular therapies are challenging. Recent advances in clot removal and endovascular grafts have made interventional therapy a possibility, but we are far from having an ideal solution to this complex problem.