Editing Infra-inguinal bypass (section)

== Planning: ==

* Confirm no significant inflow disease present
** Treat anything significant either in advance or on the day
** Iliac lesions of haemodynamic significance should be addressed in nearly all claudicants before proceeding with infra-inguinal bypass. Iliac lesions in patients with CLTI would be acceptable if there is a resting gradient of <10mm Hg and pulse and Doppler waveform at the selected inflow site are normal.
** Easy to miss iliac disease, especially with posterior wall plaque that wasn't picked up on anterior views.
* Choose proximal anastomotic site
** Does not need to be CFA. Shorter bypasses from PFA/SFA/POP are just as good in the right patient.
** Short bypasses are especially useful in diabetics with isolated infra-popliteal disease as well as in patients with previous failed bypasses and limited available conduit.
** Note that you need to have backup plans.
* Define the target artery
** There is almost always a good option, except in those with multiple failed bypasses
** Bypass all haemodynamically significant disease and insert the bypass into the most proximal limb artery that has at least one continuous runoff artery to the foot. However, isolated popliteal targets with only geniculate branches and no continuity with tibial/peroneal arteries can function surprisingly well if no better conduit is available (but suboptimal in those with frank necrosis/tissue loss in the foot, who probably need pulsatile flow).
** For the above reason, generally prefer to use a tibial target than a peroneal one, because it connects with the foot.
* Choose conduit
** Vein mapping. '''Autogenous is obviously best'''. Aim for at least 3mm, soft and compressible. Soft and compressible veins 2-3mm are worthy of exploration, but if they do not distend appropriately, find something else.
** For a long bypass, the best options are ipsilateral GSV, contralateral GSV and spliced autogenous vein, in that order.
** For a short bypass, use GSV, arm vein, then SSV.
** If vein is truly unavailable, use Dacron or PTFE for above knee insertion (no difference) and PTFE with distal vein cuff for below-knee insertion.
** Ipsilateral GSV
*** Most readily-available and durable
*** Can be used reversed, non-reversed, and in situ
**** In-situ - better size match between artery and vein, not biologically superior (equivalent results for in situ and reversed)
**** Reversed are more user-friendly and more adaptable
** Contralateral GSV
*** Only 25% of patients will go on to need it on that side, unless the contralateral limb is already ischaemic
** SSV (ipsilateral or contralateral)
*** Suitable for a short bypass
*** Can work for CFA to AK-pop or PFA to BK-pop, if the whole ankle to knee  segment is harvested
** Arm veins (cephalic/basilic)
*** Possible to harvest them in one long segment
** Femoro-popliteal deep vein
*** Awkward due to its large size
*** Difficult to harvest
** Prosthetic: 
*** Dacron
*** Heparin-bonded Dacron
*** Human umbilical vein
**** Risks of aneurysmal degeneration
**** Thick and cumbersome to handle
*** PTFE
**** Most commonly-used prosthetic conduit for infra-inguinal bypass
**** Not superior to Dacron above-knee
**** 42% 3-year patency rate in a recent randomised trial
**** Can get heparin-bonded PTFE, which is biologically active for 12 weeks, and appears to prevent early graft thrombosis
*** Vein cuffs
**** Confer a significant patency advantage  with prosthetic grafts (52% vs 29% at two years)
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