Interventional radiology Recanalization procedures for arterial stenosis and occlusions
The first percutaneous transluminal treatment of peripheral atherosclerotic disease was performed by Charles Dotter on January 16th, 1964 with the aid of coaxial Teflon-catheters. Only after Andreas Grüntzig designed the non-compliant balloon catheter in 1973 did percutaneous transluminal angioplasty (PT A) become widespread. Today balloon dilation of iliac stenosis as well as stenosis and short occlusions of the femoro-popliteal arteries is a standard procedure, particularly for patients presenting in Fontain' stage two who are generally non-surgical candidates.
The 5 year patency rates for iliac artery PTA are in the range of 90 to 95 % and 60 to 70% for the femoro-popliteal area. These results are comparable to the traditional surgical methods but usually with a lower
morbidity. Furthermore in most cases angioplasty can be easily repeated if recurrent stenosis occurs (Fig. 1)
In order to remove rather than displace, remodel or crack atheromatous material and for the purpose of recanalization of occluded arteries, laser angioplasty and atherectomy catheters have been introduced. Laser technology is still a long way away from routine clinical use as it has rather disappointing long-term results. Atherectomy devices such as the Simpson catheter may be useful in certain indications, such as the treatment of localised or eccentric stenosis and for removing intimal flaps after PTA. The Simpson atherectomy device has not been accepted as an alternative to simple balloon angioplasty as it does not improve long-term results.
Mechanical recanalization and aspiration thrombembolectomy
Various mechanical recanalization devices have been developed to help recanalization in those cases where conventional guidewire techniques including hydrophilic wires have failed. Particularly in patients with a limb at risk it may be important to recanalize long segment occlusions of more than 10 cm.
Power driven rotating or pulsating devices are used to create a channel through an area of occlusion which then accepts the guidewire over which an angioplasty balloon can be introduced to finish the dilation procedure.
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Figure 2.
Patient with atrial fibrillation experienced acute ischemia with rest-pain in right foot.
A) Right femoral arteriogram shows embolic occlusion of popliteal artery involving also the tibio-fibular arteries.
B) After percutaneous aspiration embolectomy with an 8- and 5F aspiration catheter complete restoration of the arterial lumen of the popliteal and tibiofibular arteries is re-established without using any thrombolytic drugs.
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For fresh and subacute occlusions of an embolic and/or thrombotic nature in the femoro-popliteal region aspiration catheters with a non-tapered tip made from thin-walled material with a large inner diameter and an outer diameter of 5 to 9F are used to aspirate the occluding clot. The main advantage of this technique is twofold: first the reduction of the dosage or even the complete avoidance of fibrinolytic drugs and second a considerable shorter procedure time (Fig. 2).
Thrombolysis
Thromboembolic occlusions may also be treated by fibrinolytic agents. Local fibrinolysis using Urokinase or rt-PA today is the preferred method. The lytic agents are infused directly into the clot via a selectively placed catheter. Even older clots may be lysed after weeks and months as long as the clot organisation has not been completed. Therefore local fibrinolysis is often used in combination with PTA and/or clot aspiration (Fig. 3).
Stents
Vascular stents have been designed to improve patency rates of PTA especially after recanalization of long occlusions or insufficient PTA, recoiling lesions and dissections. These stents are made from stainless steel, Tantalum or Nitinol wire filaments or tubing and are introduced with a percutaneous introducing system of 7 to 9F. There are self-expandable and balloon expandable stents in use (Fig. 4).
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Figure 3.
Patient with subacute severe right lower leg ischemia.
A) Right femoral arteriogram shows occlusion of the popliteal artery involving all 3 tibio-fibular arteries. Collaterals fill the fibular and posterior tibial artery in the mid-calf.
B) After clot aspiration from the popliteal artery, local thrombolysis with 280,000 units of urokinase and additional PTA of the tibio-fibular arteries, complete recanalization of all 3 calf arteries has been achieved.
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Figure 5.
76-year old male patient with IIb claudication in left leg.
A) Pelvic arteriogram shows chronic occlusion of left external iliac artery with collateral filling of common femoral artery.
B) After recanalization using conventional guidewire technique and placement of a 12 mm Wallstent good patency of the left external iliac artery is re-established.
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While excellent results have been achieved in the iliac arteries (Fig, 5) no significant improvement has been gained in the femoro-popliteal region because of reobstruction by intimal hyperplasia developing within the stents. So called covered stents are currently being tested as internal grafts hoping to decrease the rate of or even completely avoid intimal hyperplasia.
Christoph Zollikofer