Evidence - Femoropopliteal bypass on the right with PTFE prosthesis (PIII)

Critical limb ischaemia

Limb ischaemia can be classified into an acute and a chronic form. The diagnostic work-up of acute ischaemia must be performed promptly, and immediate revascularisation is necessary in most cases. Chronic critical limb ischaemia is the most severe form of peripheral arterial occlusive disease (PAOD). It is characterised by rest pain or necrosis or gangrene.

Acute limb ischaemia ("acute limb ischemia", ALI) represents an acutely occurring hypoperfusion of the limb that is no older than 2 weeks. The cause is usually embolisation or local thrombosis on the basis of a pre-existing pathology such as PAOD.

Chronic limb ischaemia ("chronical limb ischemia", CLI) refers to rest pain or ischaemic skin lesions such as ulcers or gangrene (Fontaine stages III and IV or Rutherford categories 4–6). It is strongly associated with cerebrovascular and cardiovascular events. Chronicity is defined as symptoms persisting for more than 2 weeks.

TASC II criteria

The TASC II (Transatlantic Inter-Society Consensus for the Management of Peripheral Arterial Disease) consensus document addresses aspects of revascularisation in PAD [1]. According to the TASC criteria, therapeutic treatment options can be derived depending on the length of the local occlusion/stenosis. The length of the stenosis and its regional location determine the treatment: endovascular or open vascular surgery.

TASC criteria for aortoiliac occlusive lesions:

TASC criteria for femoropopliteal occlusive lesions:

There are no recommendations for the morphological characterisation of the infrapopliteal segments.

Guidelines

The S3 guideline of the German Society of Angiology/Society of Vascular Medicine on the diagnosis, treatment, and follow-up of PAD includes the following remarks on CLI, among others [2]:

• The paramount goal in CLI is rapid and adequate revascularisation, regardless of the treatment techniques employed.
• In multilevel lesions, elimination of run-in obstructions takes priority over the treatment of downstream lesions.
• In CLI, run-in and subsequent run-off lesions should be treated by intervention whenever possible.
• A combination of open surgical procedures and intraoperative endovascular treatment is useful in the presence of simultaneous high-grade stenoses or occlusions of the common femoral artery, the deep femoral artery, and lesions in the aortoiliac inflow tract and/or the femoropopliteal run-off (hybrid procedure).
• Preference should be given to endovascular treatment if the angiomorphological findings suggest that a technical outcome comparable to that of open surgery can be achieved.
• If the comparable surgical procedure poses an increased surgical risk due to comorbidity, preference should be given to endovascular intervention.
• Endovascular procedures should be performed as the primary technique in the treatment of femoropopliteal lesions. In a TASC D situation with no increased surgical risk, no significantly limited life expectancy, and an available autologous vein, bypass procedures should be preferred.
• Popliteal artery lesions should primarily undergo balloon angioplasty.
• In patients with critical ischaemia, infrapopliteal vascular lesions should primarily be treated by endovascular means. Vascular surgical procedures may be considered if the surgical risk is acceptable and an autologous vein is available.

For patients with CI and CLI, the recommendations of the European Society of Cardiology (ESC) in collaboration with the European Society for Vascular Surgery (ESVS) include, among others [3]:

1. Revascularisation of aortoiliac occlusive lesions

• In short lesions <5 cm, an endovascular-first strategy is recommended.
• In aortoiliac occlusions, aorto-(bi)-femoral bypass should be considered provided that the patients are fit for surgery.
• In patients with severe comorbidity, an endovascular strategy should be considered in extended and/or bilateral occlusions.
• In aortoiliac lesions, endovascular intervention may be performed as the initial measure where appropriate expertise is available, provided that a subsequent surgical option is not compromised.
• In an aortic occlusion extending to the renal arteries, open intervention should be considered if the patient is fit.
• A hybrid procedure – iliac stenting combined with femoral endarterectomy or bypass – may be considered in iliofemoral occlusions.
• In the absence of alternatives for revascularisation, an extraanatomic bypass may be considered.
• Primary stent implantation should be considered rather than provisional stenting.

2. Revascularisation of femoropopliteal occlusive lesions

• An endovascular-first strategy is recommended for short occlusive lesions (<25 cm).
• Primary stenting as well as drug-eluting balloons may be considered in short lesions (<25 cm).
• Drug-eluting balloons may be considered for the treatment of in-stent restenosis.
• Bypass surgery is indicated in long (≥ 25 cm) lesions of the superficial femoral artery, provided that patients are not at high risk for surgery, autologous vein is available, and life expectancy is greater than 2 years. For patients not fit enough for surgery, endovascular treatment may be an option.
• Autologous saphenous vein is the bypass material of choice in femoropopliteal bypass.

Below are some of the recommendations issued by the American College of Cardiology (ACC) and the American Heart Association/AHA) for CLI patients [4]:

• In patients with CLI, revascularization should be performed whenever possible to minimize tissue loss.
• An assessment of revascularization options should be performed by an interdisciplinary care team before amputation.

1. Endovascular revascularization

• Endovascular interventions are recommended to restore perfusion to the foot in patients with nonhealing wounds or gangrene. A staged approach to endovascular procedures is recommended in ischaemic rest pain.
• Angiosome-guided endovascular treatment may be considered in patients with CLI and nonhealing wounds or gangrene.

2. Surgical revascularization

• A planned bypass to the popliteal or infrapopliteal arteries should be performed with an autologous vein.
• Surgical procedures are recommended to restore perfusion to the foot in patients with nonhealing wounds or gangrene.
• If endovascular treatment fails and no suitable autologous vein is available, a synthetic graft may be employed instead.
• A staged approach to surgical interventions is recommended in patients with ischaemic rest pain.

Results

1. Percutaneous intervention vs bypass surgery in CLI

The largest meta-analysis to date on this topic includes over 45 studies totalling nearly 21,000 patients and dates from 2018 [5]. Comparison of percutaneous vascular intervention (ER) with open bypass surgery (OR) revealed:

• ER reduced the risk of 30-day mortality, major adverse cardio- and cerebrovascular events, and wound infections, but increased the risk of long-term mortality and failure of primary patency.
• Compared with autologous bypass, ER also performed worse in secondary patency and was more likely in the long run to result in amputations.

The authors of this meta-analysis concluded that OR was the better choice for patients in good general health and with a relatively long life expectancy, in particular when autologous bypass material was available.

A 2017 Cochrane Review investigated the efficacy of bypass surgery in chronic ischaemia compared with other interventions (PTA; endarterectomy; thromboendarterectomy; thrombolysis; exercise training; and spinal cord stimulation) [6]:

• The bypass vs PTA comparison revealed that bypasses suffered more frequently from early, nonthrombotic complications, but were associated with higher technical success rates.
• One year post-intervention, primary patency was higher in the bypass group than after PTA; four years later, no difference was seen.
• The bypass and PTA groups did not differ in terms of mortality, clinical improvement, amputation rate, or reintervention rate.

The authors concluded that only limited high-quality evidence exists regarding the efficacy of bypass surgery compared with other treatment modalities.

2. Sex-specific differences in outcomes following lower limb revascularization

A systematic review with meta-analysis investigated the impact of sex on the outcomes of lower limb revascularization [7]. Forty studies were included; 15 studies reported outcomes following OR, 19 following ER, and the remainder included mixed procedures:

• Compared with men, women had a significantly higher 30-day mortality, amputation rate, early graft thrombosis, embolization rate, access site complications, as well as more general complications (cardiopulmonary, cerebral).
• No differences were found with respect to reinterventions and renal complications.
• On analysing the outcomes for OR and ER, the increased risk of postoperative mortality and complications in women persisted. However, no significant differences were found between men and women in long-term outcomes.

Among the reasons for the less favourable outcomes in women, the authors cite, among others, patient age (women were older than men at the time of intervention) and, compared with men, an undertreatment of women with antiplatelet agents, statins, and cardiovascular medication.

3. Angiosome-guided revascularization in CLI

Angiosomes are areas of skin and tissue supplied by so-called source arteries. In the human foot there are 6 such arteries (medial plantar artery, lateral plantar artery, calcaneal branch of the posterior tibial artery, lateral and medial branches of the fibular artery, dorsal artery of the foot). The wound healing rate is thought to be improved by direct revascularization, i.e., by placing a bypass onto a segment that directly supplies the angiosome.

There is a systematic review with meta-analysis on angiosome-guided revascularization in CLI from 2017 that includes nearly 4000 patients [8]. Compared with indirect revascularization (IR), direct revascularization (DR) significantly improved wound healing, major amputation rate, and amputation-free survival. However, in a sensitivity analysis, the significance for the major amputation rate in bypass surgery was lost, and no differences were found between IR and DR with respect to overall survival.

The authors concluded that their analysis supported the angiosome concept, at least for endovascular treatment. Once collateral vessels are present, the outcomes of ER versus IR are similar, suggesting that patients without collaterals are most likely to benefit from DR, thus making the angiosome concept less useful for bypass surgery.