Bypasses
These are most applicable for atherosclerotic lesions in the lower limbs, due to the prevalence of extensive lesions. The aim is to provide pulsatile flow to the foot, so the recipient vessel must have uninterrupted communication with the plantar arches.
Currently, the best results come from using the in situ saphenous vein, although some authors dispute this. They argue that ex vivo veins yield similar outcomes.
Prosthetic Grafts
The use of prosthetic grafts is limited to the suprapatellar femoropopliteal territory, with a good distal bed, and in cases where autologous grafts are unavailable. PTFE grafts are more commonly used, with some cases employing collagen-coated Dacron.
Some authors advocate for prosthetic use as the primary choice when the recipient artery is the suprapatellar popliteal, reserving the saphenous vein for potential future use. However, studies contradict this approach, showing that only a small percentage of patients require further revascularization or use of the saphenous vein for other areas in the long term.
Advantages:
– Consistent quality
– Shorter operating time
– Easy thrombectomy
– Fewer incisional complications
– Safenous preservation for future use
Disadvantages:
– Reduced long-term patency
– Increased risk of infection
– Cost
In cases requiring infrapopliteal surgical treatment for limb salvage without available autologous veins, prosthetic grafts can be used. In these cases, it is recommended to always use a venous ring, boot, or Taylor pacth at the distal anastomosis.
The grafts should be implanted deeply, sub-sartorially, to reduce infection risk. When infrapopliteal, the graft should have external support (ringed). To prevent kinking, they should be implanted in a medial subcutaneous tunnel, crossing the joint between the patella and medial condyle.
The use of associated arteriovenous fistulas to increase patency is controversial. The author lacks positive experiences with this approach.
When sequential grafts are used, prosthetic-vein anastomosis should be avoided, utilizing an artery segment between the two grafts instead.
Saphenous Vein In Situ
The advantages of using the in situ saphenous vein include:
– Living internal lining, non-thrombogenic conduit
– Caliber adaptation to donor and recipient arteries
– Gradual conduit tapering
– High utilization rate, even with varicose veins
– Utilization along its entire length
– No need for bench preparation
The vein should be devalved, except in cases where varicose veins are insufficient. Devalving should occur alongside the injection of physiological saline mixed with papaverine into the vein’s proximal portion. In cases of excessive traction, the site should be carefully evaluated, as the instrument is often caught at the ostium of a tributary of the saphenous vein.
Almost all arteries can be used as donor sources, but the use of the superficial femoral and proximal popliteal arteries is avoided due to their high atherosclerotic progression rates.
When the donor artery is the distal popliteal, the lesser saphenous vein can be used.
After devalving, tributary ligatures should precede the distal anastomosis. The last tributary should remain patent to allow blood flow in the graft while the anastomosis is being performed. Once completed, the final vessel is ligated.
Doppler use helps locate larger tributaries that have not yet been ligated. An arteriogram at the end of the procedure ensures no remaining tributaries and assesses the distal anastomosis and outflow. In case of thrombosis in any segment, an embolectomy catheter can be passed through one of the ligated branches, avoiding an incision on the graft.
Ex Vivo Veins
This involves removing the vein from its bed and reimplanting it invertedly. The author prefers in situ vein use, resorting to this technique when in situ is not possible or in distal bypasses where the donor artery is the distal popliteal artery – using the thigh saphenous vein, avoiding leg incisions, which are more challenging to heal.
Devalving the graft retains some in situ advantages, such as caliber adaptation and gradual conduit tapering.
The trajectory can follow the vein’s natural path or deeper routes, less prone to infection. Tunneling the graft after the proximal anastomosis is preferred to prevent unseen twists.
Arteriography is recommended but not mandatory, unlike in the in situ vein use.
Alternative Veins
All autologous veins other than the internal saphenous vein are considered alternatives.
The most commonly used is the external saphenous vein. However, it may lack adequate caliber at times, requiring long posterior incisions – usually, patient positioning is unnecessary for its access. In popliteofibular and popliteotibial bypass cases, a single posterior incision may suffice.
The cephalic vein is most used in the upper limb due to its length and minimal needle and catheter interference. It is harvested through longitudinal incisions along the vascular route, respecting the elbow fold. There’s a technique involving harvesting the cephalic vein to its entry into the axillary vein, along with the basilic vein to its junction with the brachial vein, resulting in a long graft requiring one devalved branch.
Two alternative conduits should be mentioned: the saphenous cross, when it has been used for cardiac revascularization – cardiac surgeons typically spare this short segment, usable as a Miller ring. Another conduit is the endarterectomized superficial femoral artery, an excellent graft for infected areas.
Studies exist on the use of deep veins, both in situ and ex vivo. In these cases, reports indicate low venous stasis-related changes, but the author lacks experience with the technique.
Ultra distal Bypasses
These are defined as revascularizations where the distal anastomosis is in the forefoot or inframaleolar territory.
They are indicated only in critical ischemia situations and should always use autologous conduits, preferably the in situ saphenous vein.
This patient subgroup has a high incidence of diabetes – about 80%. In patients with arteritis, ultra distal bypasses yield poor outcomes.
The use of optical magnification is mandatory in these cases. The postoperative use of prostaglandins appears to show promising results. There are reports of associated arteriovenous fistulas, double bypasses, and/or sympathectomy, but all are controversial cases that the author does not engage in.
One of the biggest issues is incision healing – problems arise in 20% of cases, with risk factors including diabetes, age over 70, and rest pain as a surgical indication (virtually all candidates for ultra distal bypasses). To prevent this, tension-free sutures are recommended, with occasional cutaneous relaxation incisions.
The most common recipient artery is the pedal (50%), followed by the plantar (26%), retromalleolar posterior tibial (20%), lateral tarsal (1.8%), and arcuate (1.2%) arteries.
There is a debate between ultra distal bypasses and fibular bypasses, typically free from atherosclerosis. The author believes that when there are trophic lesions at the foot level, the bypass should extend there. In cases where this is not feasible due to other factors – lack of long enough grafts and/or adjacent infection – anastomosis to the fibular artery can be used as a salvage solution.
Complex Bypasses
These are performed when two or more techniques are necessary for graft success. They occur in cases where improvement of blood supply with aortoiliac artery angioplasty is necessary, or when different grafts are used in one or more procedures.