Acute Limb Ischemia: Surgical and Endovascular Treatment

Therapeutic Algorithm

The acuity of symptom onset and clinical manifestation of limb ischemia guides treatment strategies. Reporting standards for ALI exist to guide timing and choice of intervention (see Table 103.1). The reported success of open and endovascular therapies for each level of acute ischemia also allows for creation of a therapeutic algorithm (see Chapter Algorithm , below for guidance).

Class I ischemia is a viable limb, wherein the arterial occlusion has not compromised sensorimotor function and distal perfusion is maintained via collateral pathways. As the limb is not immediately threatened a window of time does exist to allow for completion of diagnostic studies, medical optimization of comorbidities and appropriate risk stratification. If revascularization is elected, patient and anatomic candidacy for an endovascular-first approach should be assessed. Viable tissue beds are more likely to tolerate the delayed time to reperfusion inherent to endovascular therapies in this minimally ischemic class.

The category of class II ischemia represents threatened limbs, mandating timely revascularization for limb salvage. The class is subdivided into marginally (IIa) and immediately (IIb) threatened limbs based on severity of ischemic neurologic deficits, with prompt and accurate characterization key to guiding revascularization. In the marginally threatened limb (IIa), a less severe ischemic insult allows for greater consideration of an endovascular-first approach. Etiology of arterial occlusion, patient comorbidities, presence of an arterial bypass graft or intraluminal stent, physician competency with endovascular therapies, and emergent availability of operative suites and vascular surgeons for failed endovascular intervention should all be considered in decision making. With progression in extent of sensory and motor neurologic deficits, ALI is classified as immediately threatened (IIb) and requires emergent revascularization. At this level of ischemia salvage of neurologically intact viable tissue is time-sensitive, favoring traditional open revascularization. An endovascular approach with more rapid means of revascularization, including aspiration or pharmacomechanical thrombectomy devices, may be considered for the skilled operator. An endovascular-first attempt for class IIb ALI is best suited for a vascular surgeon with proficiency in open and endovascular techniques, performed in an operative hybrid suite where advanced diagnostic imaging and ability to immediately transition to an open revascularization increases technical success of the limb-salvage intervention.

In the most severe class of ALI (III), primary limb amputation should be elected as definitive therapy. The profound extent or duration of limb ischemia results in irreversible damage to nerve sensory and motor function, and muscle rigor with limb paralysis. Revascularization in this class is most often unsuccessful in salvaging a neurologically functional limb, with the risks of systemic insults and morbidity after attempted revascularization far exceeding potential benefits.

Operative Techniques

Surgical revascularization for limb ischemia may include one or more of the following: (1) catheter embolectomy or thrombectomy; (2) arterial bypass procedures; (3) arterial thromboendarterectomy; (4) hybrid vascular procedures with open and endovascular components.

Catheter Embolectomy or Thrombectomy

First reported nearly six decades ago, the Fogarty embolectomy catheter (Edwards Lifesciences; Irvine, CA) has been the de facto gold standard for surgical extraction of acute and chronic thromboembolic disease. ^, Fogarty catheters are available in a variety of usable lengths, catheter French (F) size, inflated balloon diameters, with options designed for over-the-wire, arterial, venous, and bypass graft thrombectomy use. Vascular arterial exposure and basics of surgical technique are covered in previous chapters. The site of surgical cutdown for arterial exposure is dependent on the anatomic location of obstruction. An iliac or femoral arterial obstruction may be best approached via exposure at the common femoral level, while patients with distal bypass graft or concomitant popliteal–tibial level thrombosis may also require exposure at the most distal extent of arterial blockage. Following arterial exposure with control of inflow and outflow branches, therapeutic anticoagulation is confirmed, and vascular occlusion performed. An arteriotomy is made either transverse just proximal to branch points, or longitudinal if needed for endarterectomy or bypass graft anastomotic revision. Balloon thrombectomy catheters are sequentially passed proximally and then into distal branches with standard technique until no visible thrombus is removed, and both pulsatile inflow and distal back-bleeding are restored. On-table angiogram should be performed to confirm patency of treated vessels. Figure 104.1 shows the completion angiogram in a patient treated with catheter thrombectomy for acute limb ischemia. The patient had undergone emergent bedside percutaneous placement of cannula for extra-corporeal membrane oxygenation (ECMO) one day prior to operative exploration and had developed clinical signs of ALI within 24-hours post-procedure. Operative exploration revealed cannulation at the proximal superficial femoral artery (SFA) with focal dissection of calcific plaque at the level of the femoral bifurcation, and extensive acute thrombotic occlusion of SFA and above-knee popliteal artery. Revascularization required femoral exploration, femoral–popliteal antegrade balloon thrombectomy, focal femoral bifurcation endarterectomy with bovine pericardial patch angioplasty. Repair resulted in restoration of in-line arterial flow and palpable pedal level pulses, with angiogram confirming patency of vessels without residual thrombus.