Infrainguinal Disease

The guidelines made the following recommendations when surgery is performed for

infrainguinal occlusive disease with a clear preference for the use of autogenous vein for the bypass graft (Figure 8) (3):

 Bypass to the above knee or below knee popliteal artery should use autogenous vein if possible.

 A distal bypass should originate at the most distal artery with continuous flow from above and without a greater than 20% stenosis. The tibial or pedal artery that can provide continuous and uncompromised flow to the foot should be the site of distal anastomosis.

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 Femorotibial bypasses should use autogenous vein, such as the ipsilateral greater saphenous vein or, if this is not available, other autogenous sources from the leg or arm.

 When no other form of bypass with an autogenous vein is possible, both a composite sequential femoropopliteal-tibial bypass and bypass to an isolated popliteal artery segment with collateral outflow to the foot can be considered.

 When no autogenous vein is truly unavailable and amputation is imminent, a prosthetic femorotibial bypass and possibly an adjunctive procedure, such as arteriovenous fistula or vein interposition or cuff, should be used.

 When no autogenous vein is available, it is reasonable (a weaker recommendation) to use prosthetic material for bypasses to the below knee popliteal artery.

3.2.2.1 Femoropopliteal bypass — Femoropopliteal bypass is indicated when arteriography reveals that the superficial femoral artery or proximal popliteal artery is occluded and that the patent popliteal artery has luminal continuity with any of its three terminal branches. Femoropopliteal bypass grafts are categorized as either above knee or below knee as determined by the location of the distal graft to artery anastomosis.

The use of ePTFE is less risky in the above knee position, and some consider it to be the technique of choice in this setting, citing studies demonstrating early patency rates similar to autologous vein grafting (126). The use of ePTFE has the additional theoretical advantage of preserving the saphenous veins for future coronary bypass or more distal peripheral revision.

These findings have led to the recommendation that a saphenous vein graft is preferred for above knee grafts. If a prosthetic bypass graft is used, the human umbilical vein should be considered before ePTFE. The argument to preserve saphenous veins for possible coronary artery grafting does not appear justified, and many vascular surgeons prefer the use of autologous vein graft in any position.

Despite the good outcome from autologous vein grafts, late occlusion due to progressive disease of arteries on either side of the bypass or deterioration of the graft itself is still a concern.

Aspirin, with or without dipyridamole or anticoagulation has not been shown to improve limb salvage rates and have an increased the risk for hemorrage (ie, intracerebral, gastrointestinal) (127-129).

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Figure 8: Infra-inguinal surgical options [modified according to the TASC II Guidelines (2)]:

- Femoropopliteal by-pass (above or below the knee; black bypass);

- Femoro-tibial by-pass (tibial or peroneal; green bypass);

- Popliteo-popliteal by-pass (dotted black bypass)

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The TASC II Guidelines recommend including all operated patients, indipentently if they have received a venous or a prosthetic bypass, in a surveillance program. This surveillance program should be aimed to detect as early as possible a bypass degenerence (e.g., stenosis), which may finally lead to an early reintervention, especially in those patients presenting with an impending bypass occlusion.

This program should include: - an interval history (i.e., new symptoms), a vascular examination (i.e., pulses palpation), an ABI measurement at rest, as well as a complete duplex scanning of the entire bypass, with special attention the the proximal and the distal anastomosis sites -. This follow up examinations should be performed immidiately after the intervention and at regular intervals (e.g., every six months) for at least two years (2, 3)

3.2.2.2 Infrapopliteal bypass — An infrapopliteal bypass should be performed only in situations of lower extremity ischemia in which femoropopliteal bypass is not feasible or does not allow graft flow into patent runoff vessels.

The most important factor in choosing an outflow vessel for the distal anastomosis of an infrapopliteal bypass is the overall quality of the vessel. If two vessels of excellent quality are

available, the preference probably should go to the vessel with the greatest degree of direct continuity with the foot. If no other factors are involved, the generally accepted order of preference for the infrapopliteal anastomosis is the posterior tibial artery, the anterior tibial artery, and the peroneal artery. The peroneal artery may be less desirable because it is deeper and more difficult to expose and because it is not directly continuous with the pedal arteries, and therefore thought by some to produce an inferior result in the setting of foot gangrene (130).

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Table 3 summarizes the different bypass procedures with their associated operative mortality and 5 years patency rates.

TYPE AND LOCALIZATION OF THE BYPASS Peri-operative Mortality Rates Expected Patency Rates

Femoro-popliteal (AK) vein BP Up to 6% 66% at 5 years

Femoro-popliteal (AK) prosthetic BP Up to 6% 50% at 5 years

Femoro-popliteal (BK) vein BP Up to 6% 66% at 5 years

Femoro-popliteal (BK) prosthetic BP Up to 6% 33% at 5 years

Femoro-tibial vein BP Up to 6% 75% at 5 years

Femoro-tibial prosthetic BP Up to 6% 25% at 5 years

Table 3 : Vascular surgical procedures and their respective outcomes: AK = above the knee;

BK = below the knee [modified according to the TASC II and ACC/AHA Guidelines (2, 3)]

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