The peripheral vessels

Interventional procedures in peripheral vessels

 

Percutaneous revascularisation of arteries
The basic and most popular percutaneous revascularisation technique of the distal aorta, the pelvic and peripheral arteries is percutaneous transluminal balloon angioplasty (PTA) where balloon catheters are guided past the stenosis and through occlusions with the help of a guidewire. In addition numerous other mechanical devices for recanalisation such as rotating or pulsating wires and catheters, atherectomy devices and aspiration catheters have been developed. Furthermore, thrombolysis with Urokinase and less frequently rtPA is used to dissolve and recanalise thrombo-embolic occlusions. All of these methods are generally used in combination with balloon angioplasty. Other new developments are Laser angioplasty to remove plaque material or endovascular stents for the treatment of recurrent or residual stenosis and complications after PTA or surgery. Adjunctive therapy to prevent acute or delayed thrombotic occlusion and/or restenosis consists of inhibition of platelet aggregation by plateled inhibitors such as salicylic acid (SSA), Heparin to avoid acute thrombosis and vasa dilators to avoid mechanically induced spasm. As a general principle 5,000 units of Heparin are given intraarteriarly during the procedure. To prevent arterial spasm oral calcium antagonists or intraarterial nitroglycerine or lidocaine may be given. After successful revascularisation plateled aggregation inhibitors (SSA) are given in uncomplicated cases. Heparinisation for three days followed by oral warfarin is advocated after recanalisation of complete occlusions or in patients with increased risk of peripheral embolisation. Oral anti coagulation is also indicated after stent procedures in patients with insufficient run-off. Other regimens for the prophylaxis of thrombosis and recurrence pre- and post-treatment consist of a combination of SSA and Dipyridamole.

Percutaneous transluminal ballon-angioplasty
Balloon dilation is based on Grüntzig's original concept using a non compliant balloon mounted on a double lumen catheter. One lumen allows

Figure 37. Balloon catheters of 4, 8 and 6 mm diameter.

the balloon catheter to be advanced over a guidewire and permits injection of contrast material while the second lumen serves to inflate the balloon to a predetermined diameter. The pathomorphologic mechanism by which PTA works maybe described as a "controlled traumatic injury" consisting mainly of rupture of the intimal and medial layers as well as stretching of the arterial wall leading to a more or less free arterial lumen followed by a healing process which results in a smooth inner surface.

Modem balloon catheters are usually made from Polyethylene or Polyethylene-Teraphthalate or Polyurethane and Nylon compounds which allow inflation pressures of approximately 5 to 20 atmospheres, according to material and balloon diameter. Various shapes and profiles allow safe dilation of large diameters such as occur in the aorta down to the very small calibres which occur in the tibiofibular arteries (Fig. 37). There is a wide variation in the preferred timing of balloon inflation lasting anywhere from around 20 seconds to several minutes. Usually 20 to 60 second inflations applied to overlapping segments are used. In very resistant lesions prolonged inflation of the balloon over several minutes may be of benefit but can be applied only if sufficient collateral flow distal to the occluding balloon is present. For this reason continuous monitoring of the peripheral blood flow using oscillometry of the toes is very useful.

According to the site of the lesion an ante- or retrograde arterial puncture in the groin is selected. We always use a hemostatic sheath for easy catheter exchange, protection of the arterial wall from insufficient balloon deflation and for control injections with contrast material. After an initial control angiogram the obstruction is traversed with a guidewire under fluoroscopy followed by the balloon catheter. The balloon size is selected according to the estimated original lumen size. Balloon dilation

a b

Figure 38. Various guidewires (A) (from left to right standard 0.035 J-wire floppy Benson cerebral-wire, Terumo-wire and .021 steerable wire with flexible gold tip) and angiographic catheters (B) (from left to right Cobra, headhunter, sidewinder, Pigtail).

is always monitored under fluoroscopy and the results checked with an angiogram after deflation of the balloon. To pass irregular stenoses or occlusions various guidewires with different shapes and steering qualities are available. A steerable 0.035 torque control wire which protrudes beyond a soft tipped 4 or 5F angiocatheter with a slight curve at the distal end is best suited for traversing a total occlusion. Lately hydrophilic wires have become very popular (Fig. 38). If a lesion cannot be passed with a guidewire other mechanical devices such as rotating wires, drills or rotablators may be tried. Finally local or regional thrombolysis and/or percutaneous aspiration thromboembolectomy (P A T) is increasingly used to recanalise acute and subacute occlusions (see below).

The indications for PT A of aortoiliac and femoral angioplasty range from claudication to rest pain and gangrene. The ideal lesion is a short concentric stenosis whereas long eccentric lesions are less ideal. Iliac occlusions and femoral occlusions longer than 10 cm are no longer felt to be contra-indications. Distal popliteal and tibioperoneal lesions have also become treatable lesions with modem low-profile balloon catheters especially for limb salvage (Figs. 39 + 40). The success rates in aortoiliac disease as well as in the femoro-popliteal territory are high at 95 and 87%, respectively. The patency rates are between 80 and 90% and 60 to 70% after 5 years. The complication rate is approximately 5% but with only 1% requiring surgery. Hematomas and peripheral embolisation are the most frequent complications, of which the latter may by treated with P A T or fibrinolysis during the intervention. Stenosis of the subclavian artery can also be dilated with a success rate of over 90%. Increasingly lesions of the carotid and vertebral arteries are treated with PTA.

Figure 39.Patient with Fontaine IIB claudication. A, B) Angiogram before (A) and after (B) recanalization with a J-guidewire and balloon dilation showing a good result.

Figure 40. Patient with stage IV disease and threatened limb. A) Angiogram shows total occlusion at trifurcation. B) After recanalisation of fibular artery with Terumo-guidewire and 2.5 mm PTA balloon there is good patency of fibular artery.

Laser angioplasty
Laser angioplasty uses laser energy to remove atheromatous material mainly by evaporation secondary to high local temperature. The most common laser systems are the Argon-Laser, the Neodynium Yag-Laser and the Xenonehloride-Exeimer-Laser. Various systems to deliver the laser energy to the target site such as bare fibre optics, metal caps (hot tip), sapphire tips and balloons (hot balloon) have been used. The main problem with the laser technique lies in the steering of the probes (perforation), the limited diameter of the recanalised lumen and the high costs of the laser systems and probes. Since most occlusions can be recanalised with cheaper systems and long-term results are no better than those of balloon angioplasty, this technique is of limited value as of yet.

Figure 41. Removal of postsurgical intimal flap. A) Simpson atherectomy catheter. The inflated balloon (B) presses the atheroma (A) into the window of the housing with the rotating knife (K). B,C) Angiograms of popliteal artery showing obstructing intimal flap (arrow) before treatment (B) and after removal by the atherectomy catheter (c) with a smooth lumen.

DrilIs and atherectomy catheters
For chronic, hard and calcified lesions which cannot be managed with conventional guiedwires, various rotating devices have been developed. Of the various systems so far only the Rotacs system and the Simpsonatherectomy-catheter have been used successfully in large numbers. The Rotacs system consists of an electrically driven rotating catheter (outer diameter 2,2 mm) made from steel coiled-wires with an inner lumen that allows the introduction of exchange wires and the injection of contrast agents. It is covered with a highly flexible Teflon-shrinking tube and has an olive shaped blunt tip. The motor unit, offering a continously variable speed range up to 500 rpm is battery operated. The overall success rate of the Rotacs-system is about 78% with a 66% success rate after pre viously failed conventional techniques.
The Simpson atherectomy catheter can be used only for stenosis, intimal flaps or after an occlusion has be en passed with a wire because the rotating atherectomy knife is contained within a cylindrical housing with a longitudinal window. A balloon opposite this window serves to press the latter snuggly against the atheromatous plaque so that the advancing rotating blade may cut the atheroma protruding into the window (Fig. 41 A). The results of the Simpson-catheterunfortunately are not significantly superior to conventional balloon angioplasty. It can be a very helpful tool when used to treat eccentric stenoses or intimal flaps (Fig. 41 B, C).

Figure 42.Patient with acute embolus in trifurcation treated with percutaneous aspiration embolectomy. A) Thin walled 8F endhole catheter and 60cc syringe to supply suction. B, C) Angiograms be-fore and after removal of embolic occlusion involving the trifurcation with three passes of catheter aspiration.

 Percutaneous aspiration thromb-embolectomy (PAT)
PAT is an effective and relatively simple technique for removing fresh and older clot as well as embolic material. Depending on the size of the blocked arterial lumen a thin walled, non-tapered catheter of 4 to 9F is advanced through a hemostatic sheath. The catheter is applied to the thromboembolic occlusion and a negative suction is generated with a large (60 cc) syringe. The catheter is withdrawn keeping the suction constant. In fresh embolic occlusions PAT alone may restore the entire lumen with only a few passes (Fig. 42). In thrombotic and subacute occlusions PAT may be combined with local thrombolysis and PTA is performed where additional stenotic lesions are found. We also use PAT regularly to extract distal emboli during PTA or fibrinolysis. The combination of local thrombolysis and PAT considerably reduces the amount of fibrinolytic drugs required and speeds up the procedure.

Fibrinolysis/thrombolysis
Percutaneous intraarterial thrombolysis is used to recanalise thrombotic occlusions. The lytic drug may by infused over a catheter or aperfusion wire placed proximal to the occlusion (regional fibrinolysis). Today however, it is often preferred to infuse the fibrinolytic drug directly into the thrombotic occlusion thereby reducing the amount of fibrinolytics necessary for recanalisation because of the prolonged contact of the activated plasmin with the thrombus (local thrombolysis). The agent most widely used today is Urokinase. For regional fibrinolysis a typical dose is 50,000 to 100,000 units of urokinase per hour (Fig. 43). In local fibrinolysis

Figure 43.Patient with threatened limb from acute occlusion of superficial femoral artery and poor distal run-off. A, B) Angiogram showing occlusion of SFA with poor runoff. C, D) Follow-up angiogram 12 hours after infusion of a total of 1.2 million units of urokinase shows restoration of patency including tibiofibular artery.

the usual dosages are about 5,000 to 20,000 units per cm of occlusion, depending on the age and degree of organization of the thrombus. The other (much more expensive) agent currently used is rt-PA, however, no definite advantages of its use in peripheral occlusive disease have yet been proven. In local tibrinolysis a 5F angiocatheter is usually introduced 3 to 4 cm into the clot and increments of 5,000 to 10,000 units of Urokinase are infused. Under fluoroscopic control the catheter is slowly advanced distally into the occlusion. The thrombus should not be traversed before most of the proximal clot has been lysed to prevent distal embolization. Combining this method with PAT may significantly speed up the procedure and reduce the dose of Urokinase.

Recently the so-called pulse-spray method has been advocated. This technique uses a catheter with multiple tiny side-holes to disperse small volumes of highly concentrated fibrinolytic drug into a 5 to 10 cm long occluded segment. A further development is the microporous balloon catheter where the balloon is perforated by numerous holes of microscopic size. With a mixture of fibrinolytic drug and saline the balloon is inflated with a comparatively low pressure of one to two atmospheres leaking the drug by multiple small jets of highly concentrated Urokinase or rt-PA into the clot. The clot is infiltrated and compressed against the arterial wall at the same time (Fig. 44). In our experience this method speeds up the lytic process and has been especially useful in older clots and/or chronic occlusion with soft non-organised thrombus. Again this method may be successfully combined with PAT and conventional PTA.

 

Figure 44.Patient with subacute ischemia of left leg due to occlusion of a superficial femoral artery. A) 25 cm occlusion of SFA from origin to the adductor canal. Distal SFA filled via collateral (arrow) from deep femoral artery (DF A). B) After recanalization with guidewire a micropore-balloon is progressively advanced distally infusing 5,000 to 10,000 units of urokinase every l to 3 minutes. The balloon (arrows) is placed just above the distal stenosis in the adductor canal region and partial lysis is noted proximal to the balloon. C) After infusion of 300,000 units of urokinase within 60 minutes the lumen has recanalised, however, there are still some filling defects. D, E) After additional PTA with a conventional 6 mm balloon there is a widely patent femoropopliteal artery with only minimal wall irregularitie

Figure 45.Endovascular stents used in the arterial system. A, B) Balloon-expandable Palmaz and Strecker stent. C) Self-expandable Wallstent.

Standard local fibrinolysis has a success rate of over 80% in the femoro-popliteal territory. Best results are achieved if the thrombus is less than 3 months of age and easily passable with a guidewire. The complications in regional fibrinolysis are about 10 to 15 % whereas for local fibrinolysis they are reduced to about 6%. The main complications consist of hematoma formation and distal embolisation for the latter method. Hemorrhage is rarely seen in local fibrinolysis if dosages of 400,000 to 500,000 units of urokinase are not exceeded. Local fibrinolysis has also been successfully used for recanalisation of iliac occlusions and in thrombosis of hemodialysis shunts.

lntraarterial stents
To overcome the problem of insufficient PTA due to elastic recoil, intimal flaps, persistent flow obstructing plaques and restenosis following PTA, endovascular stents have been developed. Most widely used in the arterial system are the two balloon expandable stents designed by Palmaz and Strecker and the self-expandable Wallstent (Fig. 45). These stents consist of a fine mesh of metal filaments or of thin-walled stainlesss steel tubing with staggered rectangular slots in the case of the Palmaz-stent. Mounted on a balloon catheter or a special introducing instrument, the stents can be released at the desired site via a percutaneous inguinal approach. The expanded metal stents are strong enough to withstand the recoiling forces of the arterial wall and to keep the lumen well open. The results in the iliac arteries have been excellent with patency rates of over 90% after 5 years. The stents are especially valuable in the management of complex iliac lesions and iliac occlusions (Fig. 46 A, B). In the femoropopliteal axis intimal hyperplasia is a yet unsolved problem and leads to reobstruction in 40 to 60% (Fig. 46 C, D). The more distal the stents are placed respectively the smaller the vessel diameter, the more likely is the development of intimal hyperplasia. This process is even more likely if there is an insufficient distal outflow. Therefore, great care should be taken when considering patients for femoro-popliteal stenting and other means such as repeated balloon dilation and percutaneous atherectomy should be tried first.

Embolization procedures

Embolization procedures are an important alternative to surgical treatment for arterial bleeding, aneurysms, arteriovenous fistulas and malformations (angiodysplasias), as well as tumors of the peripheral vasculature. The main indications are:
- Treatment of iatrogenic and traumatic bleeding including AV-fistulas and aneurysms especially in the pelvis and in the extremities.
- Congenital AV-malformations and fistulas,
- to stop bleeding of tumors especially in the urogenital tract and for chemo-embolisation of bone tumors (Osteosarcoma) and primary or secondary tumors of the liver

 

Figure 46. Stenting for iliac and femoral occlusions. A, B) Occlusion of external iliac artery (A) recanalizsed with guidewire and stented with two overlapping 7 mm Wallstents (B). C, D) Patient two years after femoropopliteal stenting showing a second recurrence of intimal hyperplasia within the stented segment. Patient had been dilated one year before. Angiogram shows marked irregularities of the lumen and stenosis due to initimal hyperplasia (C). After PTA there is a good result (D).

Technique and embolisation material
A high quality (super selective) angiogram is aprerequisite for any type of arterial embolisation. The catheters through which the embolic material will be administered, should be guided as close as possible to the lesion in order to spare non involved arteries and tissue. Torque control catheters of 4 and 5F with an inner lumen of .035 or .038 inches (0,9, 1,0 mm) are used together with special steerable wires. Guidewires with hydrophilic coating have greatly improved the trackability of peripheral arteries. For access to small and tortuos vessels catheters of2.7 to 3F size

Figure 47. Embolization materials. l) Gianturco coils. 2) Polyvinyl alcohol (Ivalon) - particles of various sizes. 3) Gelfoam particles.

 

Figure 48. Patient with intermittent bleeding causing swelling of thigh and drop of hemoglobin after total hip-prosthesis. A) Antegrade arteriogram shows false aneurysm fed by a deep femoral artery branch. B) After filling the aneurysm with 7 coils and gelfoam plus blocking the feeding artery with two additional coils the bleeding has stopped. Note the coils filling the aneurysm (arrow) and the additional coils (arrowhead) occluding the feeding artery.

accepting ,016 to ,018 guidewires may be used coaxially through conventional 4 and SF angiographic catheters,

There is a great number of embolization materials (Fig, 47), the most important being: mechanical devices such as stainless steel coils and detachable balloons; reabsorbable material such as gelatin sponge (Gelfoam) and occlusion gel (Ethibloc); non resorbable materials such as polyvinyl alcohol (Ivalon), silicon spheres; liquid material such as tissue glues (Bucrylate), sclerosing agents, absolute ethanol; autologous material such as blood clot, muscle, fat etc, and finally chemo-embolic agents, No single embolization material can be used optimally for all clinical conditions. For any clinical situation several embolization materials may be required. For larger vessels, aneurysms and large AV-connections, coils and detachable balloons are the agents of first choice (Fig. 48), For medium-sized arteries Gelfoam and tissue adhesives (Bucrylate) are often used. Hemorrhage of small arteries and AV -malformations as

Figure 49.Embolization of AVM in the vastus medialis muscle of the right thigh (same patient as in fig. 27). A,+B) Superselective catheterisation of arterial branch feeding the AVM (B) shows the extent of the malformation with tortuous arterioles and cirsoid early draining veins to a much better degree than the nonselective arteriogram (A). C) Arteriogram after superselective embolisation with Ethibloc shows the AVM and main filling artery blocked. A small branch barely visible before is now seen to be feeding a small non-occluded part of the AVM.

 well as tumors are treated with particulate matters such as Ivalon, Gelfoam, Ethibloc, Bucrylate, ethanol or minicoils (Fig. 49).
Complications of embolization procedures in the peripheral arterial system usually result from ischemia and infarction of the target organ. Reflux of embolization material or passage through to the venous side with unintended occlusion of non-target vessels (Le. peripheral ischemia, lung embolism) are other sources of complications. With a meticulous technique the complication rate should stay below 5%. However, pain, soft tissue swelling and fever, which constitute postembolisation syndrome may last for 2 to 10 days and are seen quite commonly.

 

Christoph L. Zollikofer and Frode Laerum