ENDOVASCULAR REVASCULARISATION Wound healing usually requires uninterrupted pulsatile arterial blood flow into the foot.
There- fore, proximal revascularisation alone, in the presence of distal disease, is insufficient and has to be combined with treatment of the distal arteries.
Thus, in addition to any proximal stenotic or occlusive lesions in the aorto-iliac or femoro-popliteal segment, dilatation of stenoses or recanalisation of occlusions of one or more tibial arteries is required to provide adequate flow to the foot.
The aim is to always provide a good haemodynamic result with sufficient pulsatile foot perfusion, and only under these circumstances will healing of the foot ulcers or healing of any wounds following surgery be accomplished.
PTA is usually applicable in stenotic lesions of the arteries whereby a guidewire is used to cross the lesion and the lesion dilated using a balloon catheter.
Femoral artery is the usual access route for interventions in most of the arterial tree.
Seldinger technique involves introduction of a guidewire through a needle puncture, and once the wire is safely into the arterial lumen, the needle is substituted with a catheter, which is fed over the wire.
A formal femoral arteriogram is done using contrast injection through a pigtail catheter for outlining the whole of the peripheral arterial tree.
Any aorto-iliac lesions can be treated with a retrograde puncture (where the wire through the needle advances in the caphalad direction) of the femoral artery.
When contrast injection outlines the lesion, under roadmap facility, a guidewire is passed inside the catheter lumen and is negotiated through any stenotic or occlusive lesion.
An appropriate-sized balloon is placed and dilated to the desired pressure, in order to squeeze the offending atherosclerotic lesion into the wall of the artery.
Dilatation results in cracking and squeezing of the atheroma into the wall as well as permanent stretching of the media, resulting in an adequate channel.
A repeat inflation of balloon may be carried out if the dilata- tion is unsatisfactory (>30% residual stenosis).
Such dilatation may require higher inflation pressure, more prolonged than before, to achieve an adequate result.
Despite this, if the flow is impaired for any reason, the lesion may be stented.
Various stent types and designs are available.
The two broad categories of stents are bal- loon expandable or self-expanding stents.
Depending on the length, location and tortuosity of the lesion and whether there is calcification present, one or the other type of stent may be appropriate.
Stents have the widest application in the aorto-iliac segment, and particularly for occlusive disease of the artery.
Their use in the infrainguinal segment is limited.
An antegrade femoral puncture (wire heading in the caudad direction) is usually necessary to treat femoro-popliteal and/or tibial artery disease.
Whilst there may be proximal disease in the aorto-iliac or femoro-popliteal segment in diabetic patients, particularly when the cause of the PVD is multifactorial, the predominant disease is present in the tibial arteries.
One of the greatest advantages of PTA over surgery is that treatment can be directed at all levels at the same time, thus having maximum possibility of achieving a good pulstile flow down to the foot (Figure 20.2).
Because of the predominance of distal arterial disease in diabetic patients, any treatment capable of improving the distal arterial tree will make a substantial impact.
Whilst the conven- tional PTA is able to treat simple stenoses or short occlusions in the tibial vessels with the help
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242 INTERVENTIONAL RADIOLOGY IN THE DIABETIC FOOT
Figure 20.2 This diabetic patient has critical limb ischaemia, manifesting as foot ulceration. A short popliteal occlusion and both the anterior and posterior tibial artery occlusions were recanalised with subintimal angioplasty
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RESULTS 243
of fine wires and catheter available these days, subintimal angioplasty is capable of treating a large number of cases because of the ability of the technique to treat long tibial occlusions and multiple vessels as well as to reconstitute the trifurcation.
Since the first description of subintimal angioplasty in 1989/1990,17, 18 a number of centres have published their experience particularly in patients with critical limb ischaemia, of which diabetic patients form a large proportion.
Subintimal angioplasty has been shown to make a substantial impact on the treatment of critical limb ischaemia mainly due to the fact that long superficial femoral artery (Figure 20.3) and tibial occlusions (Figure 20.2) can be tackled with this technique.
The technique has been widely described elsewhere.19, 23 Briefly, it involves traversing the occlusion not through the lumen but through the subintimal space, thus making use of the disease-free dissection space that becomes available as a conduit for blood flow.
The technique utilises a deliberate but controlled arterial dissection to cross an arterial occlusion or even a segment of diffuse disease.
The subintimal plane is the path of least resistance and is therefore relatively easy to cross, using a loop in a hydrophilic guidewire.
After balloon dilatation, the resultant lumen is eccentric, wide and cosmetically appealing because it is disease free.
Since this newly created channel is free of atheroma, good long-term patency can be expected (Figure 20.4).
RESULTS Conventional PTA has an application in tibial arteries where there is stenotic or short occlu- sive disease, but the outcomes achieved at 1 year are variable and generally poor in diabetic compared to non-diabetic patients.24, 28 There have been a number of reports from the beginning of this century that have shown that subintimal angioplasty holds promise in the treatment of critical limb ischaemia.
Table 20.1 shows treatment of the femoro-popliteal segment predominantly, but also in conjunction with tibial arterial disease.
Apart from the article by Florenes (diabetes incidence 9%), the inci- dence of diabetes in these patients with critical limb ischaemia ranges from 33 to 59%, thus constituting a substantial proportion of the patients with critical limb ischaemia.29, 34 Despite small numbers in individual series, some important conclusions can be drawn.
Firstly, subintimal angioplasty in the femoro-popliteal segment is primarily a successful
Table 20.1 This table shows the published series of subintimal angioplasty of the femoro-popliteal segments in patients with critical limb ischaemia. (Florenes showed an excellent assisted patency rates of 64% at 5 years). (Lazaris showed a limb salvage rate of 88% at 3 years)
Diabetics Primary success 1-year patency 1-year salvage Study Limbs/PTS (%) (%) (%) (%)
London et al.29 54 49 91 78 89 Tisi et al.30 129 33 85 33 88 Lipsitz et al.31 39 59 87 74 90 Molloy et al.32 133 39 79 , 88 Florenes et al.33 116 9 87 64 (5 years) , Lazaris et al.34 112 33 89 , 88 (3 years)
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244 INTERVENTIONAL RADIOLOGY IN THE DIABETIC FOOT
Figure 20.3 There is a flush occlusion of the superficial femoral artery extending to the mid-popliteal artery. Subintimal angioplasty achieved a successful outcome
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RESULTS 245
Figure 20.4 A long flush superficial femoral artery occlusion was recanalised successfully. A follow-up angiogram 7 years later shows some diffuse disease, but the artery is still patent (note the dates on the angiogram)
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246 INTERVENTIONAL RADIOLOGY IN THE DIABETIC FOOT
Table 20.2 This table shows the limb salvage rates in patients who have had subintimal angioplasty in tibial arteries only. (Ingle showed a limb salvage rate of 94% at 3 years)
Diabetics Primary success 1-year patency 1-year salvage Study Limbs/PTS (%) (%) (%) (%)
Nydahl et al.35 28 33 80 56 85 Vraux et al.36 40 72 78 56 81 Ingle et al.37 70 46 86 , 94 (3 years)