Popliteal Artery Occlusive Disease Treatment & Management

The advent and subsequent FDA approval of cilostazol was a significant advance in the pharmacologic therapy for patients with intermittent claudication. Cilostazol is phosphodiesterase III inhibitor with several mechanisms of action. The most important of these are inhibition of platelet aggregation (via inhibition of ADP pathway) and vasodilatation. Clinical data, based on several randomized studies, have emerged demonstrating a significant improvement in overall walking distances and quality of life in patients taking cilostazol.

The main adverse effects include headache, diarrhea, and palpitations. Approximately 15% of patients can not continue with this therapy due to side effects. Starting with low doses and then gradually increasing to the recommended dose (100 mg twice a day) may alleviate some of these side effects. Cilostazol is absolutely contraindicated in patients with chronic heart failure of any severity.

Atherosclerosis

Atherosclerotic popliteal thrombosis in which the limb is not imminently threatened is best treated medically. Cardiovascular disease is the major cause of death in patients with PAD. Thus, the treatment should be directed not only at improving walking distance and alleviating presenting symptoms, but also at reducing cardiovascular risk factors. Conservative treatment can begin with simple modification of life style and risk factors such as smoking, hyperlipidemia, diabetes mellitus, hypertension and obesity. Institution of various exercise programs has also been proven to be beneficial. Among traditional risk factors for atherosclerosis, cigarette smoking is most strongly correlated with PAD.

Popliteal artery aneurysm

Because of the high rate of complications from aneurysms, medical therapies such as clot lysis are not routinely initiated except to identify an artery for distal anastomosis or when the patient is critically ill and cannot withstand an operation.

Emboli

Treatment with lysis, such as with urokinase and TPA, can be efficacious. However, emboli are likely to recur if definitive therapy is not undertaken for the underlying problem.

Popliteal entrapment syndrome

Aside from surgical intervention, rest is the only other treatment shown to decrease symptoms.

Cystic adventitial disease

No effective medical treatments are available for cystic adventitial disease.

Popliteal artery occlusion

Surgical therapy for popliteal artery occlusion is bypass of the occlusion, which can be achieved with grafts, including great saphenous vein (GSV) or prosthetic (eg, polytetrafluoroethylene [PTFE]) grafts. GSV bypass can be used in a reversed, nonreversed or in situ orientation. The reverse vein bypass graft, first described by Kunlin in 1949, has become the favored operation for bypass of an occluded popliteal artery. The ipsilateral GSV is the conduit of first choice. If that is unavailable, alternative autogenous conduit options that can be used include the contralateral GSV, arm veins (basilic and cephalic), the small saphenous vein, the superficial femoral vein, the popliteal vein, or cryopreserved veins.

The popliteal artery is accessible from medial thigh and calf incisions. The anastomosis can be performed either end-to-end or side-to-side. If the latter is chosen in the case of an aneurysm, the aneurysm must be excluded from the circulation by ligature.

Percutaneous transluminal angioplasty (PTA) is a less invasive intervention in the treatment of popliteal artery occlusive disease. PTA is indicated for short (< 2 cm) lesions in patients who have claudication and good runoff. Initial enthusiasm that stents could increase long term results of PTA has not been supported by subsequent studies. The primary patency rate at 1 year is 65%. However, PTA may be a reasonable alternative to open surgery for limb salvage indications in patients with prohibitive surgical risks.

The relative lack of long-term success rates with PTA and stenting led to the development of other endovascular procedures such as atherectomy, laser angioplasty, cutting balloon angioplasty, cryoplasty, and brachytherapy. Although initial results using directional atherectomy were disappointing,^[8] developmental and technical modifications of new-generation atherectomy systems, over the last decade, have lead to promising mid- and long-term patency rates.^[9]

Initial data on directional atherectomy from one of the largest, multicenter, nonrandomized, observational studies (Treating Peripherals With SilverHawk: Outcomes Collection; TALON), which involved 19 medical centers in the United States, demonstrated excellent procedural success rates of 97.6% and less than 50% residual stenosis achieved in 94.7% of treated lesions.^[10] Of 1258 symptomatic atherosclerotic lower extremity lesions in 601 patients enrolled in the TALON registry, 182 (14.5%) affected the popliteal artery. In the same study, the overall 6- and 12-month freedom-of-target-lesion revascularization rates were 90% and 80%, respectively.

A subgroup of PAD patients with calcified popliteal stenotic lesions represents a special therapeutic challenge. Stenting of calcified lesions is frequently complicated with stent underexpansion, which is associated with increased risk of in-stent restenosis, and thrombosis.^{[11, 12]}

Data from a recent European study that included 38 patients with calcified lesions, treated with directional atherectomy, demonstrated the primary and the assisted primary (defined as freedom of restenosis after repeated intervention) patency rates of 68% and 79%, respectively, in the cohort of patients (n = 29) with a lesion located in the proximal or distal 3 cm of the superficial femoral artery or in the popliteal artery.^[13] In the same cohort of patients, the anke ABI increased from 0.7 ± 0.4 to 1.1 ± 0.4 at 6 months and to 1.0 ± 0.3 at 12 months after the atherectomy. Additionally, the mean Rutherford score decreased from 4.3 ± 1.0 to 1.1 ± 1.3 and to 0.9 to ± 1.3 at 6 and 12 months, respectively.

Although results from clinical trials that evaluate above-mentioned evolving endovascular treatment modalities are promising, efficacy and safety of endovascular modalities have not been extensively investigated and their role remains controversial owing to the lack of abundant randomized data supporting any improved long-term patency rates compared with a surgical approach.

Popliteal artery aneurysm

Elective surgical repair is indicated in all patients with PAA regardless of size. Even a small PAA can produce limb-threatening ischemia secondary to thrombus or distal embolization. Elective repair assures that procedure is not performed in the setting of limb-threatening ischemia. Elective repair is associated with little risk to the patient, better overall results and lower incidence of amputation. Surgical PAA repair consists of either resecting the aneurysm sac and interposing a bypass graft or proximal and distal ligation of the popliteal artery combined with bypass grafting.

More recently, endovascular repair with a percutaneously delivered covered stents (stent-grafts) has become an alternative to open repair, but long-term results are unknown.

Emboli

Emboli may be evacuated from distal vessels by either the use of a balloon catheter or intraoperative thrombolysis.

Popliteal entrapment syndrome

Surgical treatment is advised in all types of popliteal entrapment syndrome. Recognition of progressive fibrosis with subsequent thrombosis in untreated entrapped artery supports early surgical intervention. Individual anatomic considerations play an important role in determining the best surgical approach. Although the posterior approach has been most commonly advised because it most clearly delineates the anatomy of the lesion, the medial calf approach is more appropriate when the occlusion extends distally to the popliteal artery bifurcation. Myotomy of the compressing muscle or transection of fascial band leads to decompression of the artery and prevention of secondary fibrotic changes. If the artery is not occluded and fibrotic change has not occurred, no further intervention is necessary.

Recent evidence emerged that suggests that when a popliteal artery has undergone fibrotic changes and occlusion, resection and vein graft (preferably GSV) interposition are required to ensure optimal long term patency in these often young, physically active individuals.

Cystic adventitial disease

Cystic adventitial disease has been treated in numerous ways. Evacuation with removal of the cyst wall has had a 94% initial success rate in 68 operations performed. Evacuation with a vein patch has had a 66% initial success rate in 9 operations performed. Evacuation with a synthetic patch has had a 75% initial success rate in 4 operations performed.

Aspiration has had a 66% initial success rate in 3 operations performed. Simple aspiration of the cyst under US or CT guidance may decompress the cyst initially and improve arterial caliber but is associated with higher rate of recurrence, presumably because of ongoing secretion by the cyst lining. Resection with a vein graft has had a 95% initial success rate in 54 operations performed. Resection with synthetic graft placement has had a 90% initial success rate in 10 operations performed. Resection with end-to-end anastomosis of primary vessel has had a 100% initial success rate in 3 operations performed. Resection with homograft placement has a 100% initial success rate in 2 operations performed. Three cases resolved spontaneously. Angioplasty has not been successful.

Most patients with occlusion of the popliteal artery have some component of CAD or another comorbid condition. Therefore, patients' current functional status must be taken into consideration. Preoperative ECG, chest radiography, and coagulation studies are recommended. In nonemergent cases, performing lower extremity angiography is important for identifying the site of occlusion, any collateral circulation, possible target vessels for bypass and for visualization of runoff vessels. If the use of a vein is anticipated, Duplex studies should be performed to assess the caliber and patency of the veins.

Those patients with gangrene of the affected leg require a course of antibiotics and wound care prior to the bypass operation. Although not an absolute contraindication, leg infections increase the incidence of graft infections and subsequent failure.

Careful cardiac monitoring must be used in the operative intervention of popliteal artery thrombosis. These patients usually have significant comorbid conditions (eg, CAD, chronic obstructive pulmonary disease) that increase the risk of stroke, myocardial infarction, or bleeding episodes. Upon completion of the bypass, some form of confirmation of technical competency must be performed (eg, completion angiography, intraoperative duplex US, continuous-wave Doppler US).

On the first postoperative day, patients should begin aspirin therapy and, if indicated, beta-blockers. Postoperative ABI should be obtained before the patient is discharged from the hospital. These serve as a baseline to which subsequent ABISs can be compared in the event of restenosis. Postoperative visits for duplex scanning of the graft are undertaken every 3 months for a year and every 6 months thereafter.

Follow-up should be performed at regular intervals to assess for restenosis, which usually results from technical failures, intimal hyperplasia, or disease progression at other sites, at 1 month, 18 months, and 2 years or more, respectively.

• Intraoperative bleeding
• Perioperative myocardial ischemia or infarct
• Stroke
• Death
• Limb loss
• Graft infection
• Graft thrombosis
• Wound infection
• Reocclusion
• Numbness at operative site or vein harvest site
• Arteriovenous fistula (in situ GSV graft)

In patients with native conduits intimal hyperplasia, leading to the narrowing of the vein graft and valvular hyperplasia are the 2 leading causes of graft failure. The most recent studies suggest that geometric remodeling of the vein graft and decreased vein graft adaptation to the arterial environment are caused by mediators of inflammation. Diminished graft blood flow can be detected before graft thrombosis occurs. If the lesion is not corrected, graft thrombosis occurs in most cases. As a result of graft thrombosis acute ischemic events in the lower extremity can lead to limb loss.

Thus, establishing continued US surveillance after bypass procedure and vein graft revision is important. In the event of vein graft stenosis, open surgical and endovascular vein graft revision are options to maintain patency prior to occlusion. Most of the lesions underlying graft failure can be corrected by PTA, although in certain cases vein patch angioplasty or short bypass of a graft lesion is needed. PTA should be restricted to short lesions (less than 2 cm). Prosthetic (PTFE) graft failure is attributed to the thrombogenicity of the graft material and kinking of the graft from crossing knee joint, as well as anastomotic intimal hyperplasia and progression of atherosclerotic disease proximal or distal to the graft.

Vein bypasses are relatively effective, with 4-year patency rates ranging from 68-80% and limb salvage rates ranging from 75-85%. Bypasses performed with PTFE grafts yield comparable patency and salvage rates above the knee but are significantly less successful below the knee. Therefore, PTFE or other synthetic grafts should not be used below the knee unless no vein is available and the procedure is for limb salvage. Infrainguinal surgical bypass has significant morbidity and 30-day mortality (5.2%). Approximately 50% of patients require at least one secondary procedure within 3 months and 50% require hospital readmission within 6 months.

The use of endovascular therapies in the treatment of peripheral vascular disease has opened a new realm of minimally invasive possibilities. Over the last decade, with the advent of new technologies, an increasing number of percutaneous endovascular procedures are being used to treat PAD. Bare-metal, drug-eluting, biodegradable and covered stents (stent-grafts) are intended to provide enhanced treatment with a reduced risk of perioperative complications associated with open surgical treatment. Endovascular management is a reasonable alternative to open surgery in patients for whom standard surgery poses a considerable risk because of coexisting medical conditions.

Although still preliminary, short-term results for infrainguinal percutaneous interventions are favorable and have been associated with lower rates of periprocedural morbidity and lower 30-day mortality rates. However, favorable results associated with endovascular treatment options come at a cost of diminished durability and potentially increased need for reintervention.