Subintimal Angioplasty

Chapter 38


Subintimal Angioplasty


Amman Bolia and Robert S.M. Davies



Clinical Relevance


Subintimal angioplasty (SIA) was first introduced in 1987 as a minimally invasive percutaneous technique for the treatment of femoropopliteal occlusive disease in patients with intermittent claudication (IC).1 Early positive results led to use of the technique for the popliteal artery and trifurcation vessels as well, where it has proved to be invaluable as an alternative to surgical bypass for treating critical limb ischemia (CLI).


Recent results indicate that SIA treatment of femoropopliteal occlusive disease for IC is durable,2-20 and in chronic CLI it has proved so useful that it has become the first-line treatment in many patients with this condition.2135 The treatment has application in long superficial femoral artery (SFA), popliteal, and tibial occlusions and has the ability to reconstitute bifurcations and trifurcations36 that would otherwise not be possible. Long tibial occlusions extending down to the ankle and below have been treated in cases in which surgery would not be applicable. The technique has made its biggest impact in the treatment of CLI, where reported limb salvage rates are between 80% and 90%.25,28,29 In patients with IC, secondary patency rates of up to 64% at 5 years have been reported, close to those achieved by surgical bypass.2



Indications




1. Chronic femoropopliteal and tibial occlusions that have become hard, possibly calcified, thus making it impossible for the guidewire to be negotiated through an “intraluminal” approach. A subintimal dissection plane is relatively easy to create in these situations.


2. Long occlusions of the femoropopliteal and tibial arteries can be recanalized through a subintimal channel in cases where it would be difficult to maintain an intraluminal position of the guidewire.


3. An occlusion in an underlying diffusely diseased vessel would make it difficult for the guidewire to traverse the occlusion intraluminally, and hence is an indication for SIA.


4. Previously failed intraluminal attempts at angioplasty may be suitable for a subintimal approach.


5. Flush SFA occlusions in which there may be a very small stump or none at all. An intraluminal approach in these situations is difficult if not impossible.


6. Moderately calcified vessels, which are often difficult to treat by conventional angioplasty but are relatively easily managed with SIA because the wire follows the path of least resistance along the subintimal plane.


7. The presence of a large collateral vessel proximal to an occlusion that lacks a stump, which is necessary to engage the guidewire for transluminal angioplasty. This situation can be dealt with by creating a subintimal dissection above the collateral, thus avoiding persistent wire entry into the collateral.


8. When an arterial perforation occurs during attempted intraluminal crossing of an occlusion, subintimal dissection helps avoid the site of the perforation by negotiating the plane of dissection away from the site of the perforation.37,38


9. A common femoral occlusion that extends into the profunda and SFA. Recanalization of both these vessels may be achieved by the subintimal approach, thus reconstituting the bifurcation.


10. A popliteal occlusion that extends into the trifurcation vessels can be treated with SIA whereby the recanalization can be extended into all three runoff vessels, achieving a three-vessel runoff.


11. SIA has a role in recanalization of native SFA occlusions in patients who have undergone femoropopliteal bypass grafting that has subsequently occluded.39,40 Similarly, tibial occlusions can be recanalized after failure of a femorodistal bypass graft.41



Contraindications


When an occlusion is fresh (<3 months old), subintimal and intraluminal angioplasties are unlikely to be successful because of the softness of the thrombus, which fails to be displaced when the lumen is being reestablished with a balloon. In fact, attempting angioplasty for such lesions increases the risk for embolism because a fresh thrombus is more likely to be disrupted and released downstream.


It is important to elicit a careful history from the patient; any evidence of sudden worsening of symptoms should alert one to the possibility of a fresh thrombus. In these situations, a duplex scan may confirm the presence of a fresh thrombus with the demonstration of echolucency of the occluding material. It should be emphasized that other imaging modalities (e.g., computed tomographic angiography [CTA]) may not demonstrate that the thrombus is not well organized, but it may show well-developed collaterals. During attempted recanalization, a positive “guidewire test,” which implies easy passage of the guidewire through the occluding material, should provide a hint to the presence of a soft thrombus and therefore unfavorable occlusion for recanalization.


Although heavy calcification is not a contraindication, it is sometimes difficult to pass through a heavily calcified length of SFA because of failure of forward progression of the catheter or the occurrence of perforation. The presence of fine cylindrical calcification, as seen in renal failure patients, can make SIA a difficult undertaking. It is usually not difficult to initiate a dissection, but this form of calcification can make it very difficult to reenter the true lumen distally. Even when reentry has been achieved, chances of recoil due to the calcification are fairly high, and this may result in an unfavorable outcome.


Finally, calcified common femoral artery (CFA) occlusions are difficult to cross because such occlusions have to be approached from the contralateral side. The contralateral approach does not allow sufficient push to cross the occlusion, and in any case, the bulk of the calcification present does not permit a satisfactory and durable channel to be created.



Equipment


Angiography equipment with high-quality digital subtraction and roadmap facilities using a 40-cm image intensifier is desirable.


The technique requires minimal materials. A standard Teflon-coated 0.035-inch, 180-cm long guidewire is used for entry into the artery through the needle. Once entry has been achieved and a catheter introduced, the wire is substituted for a hydrophilic wire (Terumo) in either standard or stiff format, depending on the nature of the lesion. Once again, these wires are 0.035 inch in diameter and 180 cm long, with a curved tip and a 3-cm floppy end.


The most widely used catheter, particularly for flush occlusions where there is no available stump or only a small stump, is the 4F short-angled catheter (Bolia Mini-cath [Terumo Medical Corp., Tokyo, Japan]), which comes in a 20-cm length with a 30- or 60-degree curved tip. Similar shaped catheters (e.g., Bernstein [Boston Scientific, Natick, Mass.]), vertebral, or even a cobra-shaped Glidecath (Terumo Medical Corp., Somerset, N.J.) may be used for this purpose. However, the advantage of the Bolia Mini-cath is twofold: (1) being 4F and short in length, it facilitates entry into the CFA when there is only a short length of wire engaged within the vessel; (2) it is easier to handle and manipulate than longer catheters, particularly important when entering the origin of the SFA or initiating a dissection at this level through an ipsilateral antegrade CFA puncture.


The two most useful balloon catheters for use in the infrainguinal segment are 5 mm × 4 cm with a length of 80 cm for the femoropopliteal segment, and 3 mm × 2 cm with a length of 120 cm for infrapopliteal disease. Both these balloon catheters are used in a 5F format, necessary to overcome resistance offered by long length occlusions in the infrainguinal and infrapopliteal segments. A simple inflation device consisting of a 10-mL high-pressure syringe with a flow switch is used for quick inflations and deflations.


Most patients who undergo these procedures are pretreated with aspirin, 75 to 150 mg/day. Heparin, 3000 to 5000 units, is used during the procedure. The vasodilator tolazoline (a nonselective competitive α-adrenergic receptor antagonist) is given intraarterially in a dose of 5 mg before crossing a lesion, and usually 5 mg at the conclusion of the procedure to prevent vasospasm. When vasospasm does occur, glyceryl trinitrate (GTN) is used in 100 µg increments up to a total dose of 500 µg. A GTN patch is also applied to the treated leg to deliver 5 mg of GTN over a 24-hour period to sustain vasodilation in the immediate postprocedure situation, particularly when the subintimal procedure involves infrapopliteal vessels. A closure device is most useful in patients in whom a high puncture has been made. The authors currently prefer Angioseal (St. Jude Medical, Minneapolis, Minn.) unless contraindicated.



Technique


Anatomy and Approach


SIA has its main application in the femoropopliteal and tibial arteries. Therefore, the approach to these vessels is via an ipsilateral antegrade puncture unless there is a specific reason to the contrary. If a groin site puncture is not possible because of scarring from previous surgery, infection, a high CFA bifurcation, or because of severe obesity in which an antegrade puncture may be difficult, a crossover or popliteal approach is more appropriate.


For all lesions in which the SFA is of a reasonable length (≥5 cm) before the diseased segment, the puncture is usually directed at the mid- to lower part of the common femoral artery or even the proximal SFA. With palpation, one can usually work out the length of common femoral artery that is available for puncture (the part of the artery that is overlying the superior pubic ramus, against which it will have to be compressed at the conclusion of the procedure). As a general guide, the midportion of the common femoral artery is approximately at the level of the midportion of the femoral head. For flush occlusions or when there is only a small stump of the SFA, a high common femoral puncture is recommended. The site of puncture is determined by the level of the upper brim of the superior pubic ramus at which pulsations of the artery can be felt. The artery superior to this level will be the external iliac artery and must not be punctured, or the chance of retroperitoneal bleeding will be increased. The high puncture will therefore have to be directed about 1 cm or so below the palpable brim of the superior pubic ramus. A puncture at this level will mean that there is at least 1.5 to 2 cm of the common femoral artery before it bifurcates, thus allowing the Bolia Mini-cath to be positioned for manipulation into the SFA origin occlusion. A correctly sited puncture is critical; one can check the position of the puncture relative to the femoral bifurcation and superior pubic ramus by injecting contrast through the puncture needle prior to introduction of a guidewire.



Technical Aspects



Femoropopliteal Artery Occlusions


After a correct high puncture, a standard Teflon-coated guidewire is advanced into the profunda artery into which the angled 4F short catheter (Bolia Mini-cath) is positioned. An introducer sheath is not recommended for flush occlusions. A diagnostic angiogram is carried out through this catheter position to outline the full length of the occlusion and all the vessels down to the foot. It is important to obtain a detailed diagnostic study so that should a complication occur, such as embolism, one has an exact idea of which vessels were patent preintervention and which vessels have occluded postintervention. Heparin, 3000 to 5000 units, is injected IA as soon as the decision for angioplasty of the artery is made. At the same time, 5 mg of tolazoline is injected to prevent spasm in the distal vessels.


With an appropriate oblique projection (right anterior oblique for a right SFA occlusion) and small puffs of contrast material, the catheter tip is slowly withdrawn from the profunda artery into the CFA. The tip of the catheter is directed away from the profunda to the occluded SFA origin. Then, with the use of a roadmap facility, a curved hydrophilic guidewire is advanced into the origin of the SFA when a small stump is available. If no stump is available, one will usually have an idea of where the origin of the SFA should be, at the level where the profunda artery dips downward away from the line of the CFA as seen on the appropriate oblique projection. A curved hydrophilic guidewire is then run along the junction of the common femoral and profunda arteries. Usually the wire will be seen to engage at the origin of the SFA. Once engagement is achieved, the wire is advanced into the occlusion, and if necessary, the Mini-cath is positioned at the entry point of the SFA to provide support so that the wire can enter the occlusion rather than being pushed away from it. After the wire has entered the occlusion, the Mini-cath is advanced into the occlusion, and the wire is then manipulated into a loop. The loop is advanced 5 to 10 cm further, and when this position is achieved, the purpose of the Mini-cath is over, and it is replaced by a balloon catheter that is usually 5 mm in diameter × 4 cm in length on an 80-cm shaft. The loop is then advanced further, with the balloon catheter following immediately behind it. When the loop stops advancing, the balloon catheter is advanced toward the leading edge of the loop for support, which will allow the loop to be advanced further. The length of the loop is shortened every so often, and when the end of the occlusion is reached, the length of the loop must be 5 cm or less. A little twisting and forward action allows reentry to be achieved in the distal part of the artery, and in most cases this takes place without effort. Should the loop fail to reenter the artery, it is usually due to diffuse disease beyond the end of the occlusion. In such situations, the dissection can be extended further until the disease-free part of the artery is reached, where the loop has its most favorable situation for reentry. There is a natural tendency for the loop to reenter at the junction between the diseased and nondiseased segment of the artery (the line of “demarcation”). It is important at the time of the baseline angiogram to mentally mark the level beyond which one does not want a subintimal channel to extend. For femoropopliteal occlusion, extension of the subintimal tract into the below-knee popliteal artery puts runoff vessel patency at risk unless they are also occluded, and should be avoided. The authors recommend withdrawing the guidewire and reattempting to reenter the true lumen proximally should this occur. Failure to reenter using standard techniques may result in a reentry device being employed (see later discussion).


Once the entire length of the occlusion has been crossed, the balloon is inflated from the distal part to the proximal part of the occlusion. High-pressure (10-12 atm) but short inflations are carried out throughout the length of the occlusion. The balloon is usually inflated twice, once from the distal to proximal part of the occlusion, and then from proximal to distal. The balloon catheter is then positioned beyond the occlusion before the guidewire is taken out. Injection of contrast material through the catheter will confirm rapid flow in the distal vessels beyond the recanalized segment, which is a measure of a successful outcome. The catheter is gradually withdrawn to a level proximal to the recanalized segment, and during withdrawal, small puffs of contrast material are used to ensure the channel is open and flowing. A final angiogram of the newly recanalized segment is carried out. Although the recanalized segment almost invariably appears smooth and disease free, the measure of a successful outcome is usually determined by the speed of flow rather than cosmetic appearances. A completion angiogram of the distal vessels ensures that if any emboli have been released, they will be detected and dealt with appropriately.


At the conclusion of the procedure, a further dose of tolazoline (5 mg) is given to facilitate peripheral vasodilation and reduce peripheral resistance, helping enhance flow through the recanalized segment. Aspirin, if not contraindicated, is prescribed for patients who have undergone successful recanalization, the usual dose being 150 mg daily for 3 months tailored to 75 mg/day thereafter indefinitely. Some authors opt for dual antiplatelet therapy with the addition of clopidogrel (75 mg/day) or ticlopidine (500 mg/day) for 1 month post procedure. This regimen may be of benefit, particularly in those patients with known aspirin resistance.



Tibial Occlusions


Tibial occlusions can also be treated by SIA. Short occlusions are usually easily crossed intraluminally, but SIA is applicable for longer occlusions (>3 cm). The technique for crossing a tibial occlusion is similar to that used in the femoropopliteal segment. Unlike the treatment of tibial stenotic disease, in which a small wire and balloon system is used (0.018 inch and 3.5F), in the case of tibial occlusive disease it is important to use a 0.035-inch guidewire and a balloon catheter with a 5F shaft. The larger guidewire and catheter are needed because when a long tibial occlusion must be crossed (e.g., 30 cm), resistance to the wire-catheter combination is quite substantial; a larger device ensures enough strength in the system to allow progression of the catheter-wire combination throughout the length of the occlusion. The system can be further strengthened with the use of a stiff hydrophilic guidewire if necessary. The most popular catheter for this procedure is one with a 3-mm diameter, 2-cm long balloon on a 120-cm-long 5F shaft.


Once again, the aim is to form a loop in the hydrophilic guidewire that allows one to cross the entire length of the lesion with minimal risk of perforation. This loop is desirable for achieving dissection throughout the length of the tibial artery as well as reentry into the true lumen distally. Because the intima becomes thinner as the distal arterial tree is approached, it is usually not difficult to reenter the true lumen in the distal tibial artery. However, it is important to keep the length of the loop short so that the softer part (floppy tip) of the guidewire forms the leading edge of the loop and therefore reduces the chance of perforation in these small, delicate vessels. Having crossed the lesion, balloon dilation is performed in a similar manner as for the femoropopliteal segment.


In the case of a long femoropopliteal occlusion with concomitant trifurcation disease and a single vessel runoff, it is of vital importance for true-lumen reentry to occur in the patent crural vessel. This does not necessarily occur using the standard aforementioned technique, since the guidewire will have a natural tendency to take the path of least resistance—which does not always equate to the least-diseased crural vessel. In an attempt to address this potential complication, Spinosa et al. described subintimal arterial flossing with antegrade-retrograde intervention (SAFARI).42 This technique is described in depth elsewhere in the book.



Reentry Devices


Percutaneous subintimal revascularization of chronically occluded femoropopliteal or crural vessels is associated with a reported failure rate of 10% to 20% (Table 38-1). The primary limitation is the failure to reenter the distal true lumen after crossing the occlusion subintimally. Furthermore, true-lumen reentry may be significantly remote from the level of patency, thereby unnecessarily extending the length of subintimal dissection beyond that of the occluded segment. Inadvertent lengthening of the lesion may itself cause complications including loss of patent branches and collaterals distal to the treated occlusion.



TABLE 38-1


Summary Data for All Studies with Over 100 Limbs Treated with Subintimal Angioplasty























































































































































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Dec 23, 2015 | Posted by in INTERVENTIONAL RADIOLOGY | Comments Off on Subintimal Angioplasty
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Study Study Type No. of Patients No. of SIAs Disease Severity Lesion Location Technical Success Stents Used Primary Patency (Months) Primary Assisted Patency (Months) Secondary Patency (Months) Limb Salvage (Months) Survival (Months)
Bausback et al.12 Case note review 113 118 Claudication & CLI Femoropopliteal 107 (91%) Y 57% (12) 83% (12) 89% (12) NA NA
Siablis et al.11 Cohort 98 105 Claudication & CLI Femoropopliteal 96 (91%) Y 42% (24) NA NA 89% (36) 84% (36)
Sidhu et al.14 Case note review 120 128 Claudication & CLI Femoropopliteal 117 (91%) Y NA 73% (12) 85% (12) 98% (12) NA
Setacci et al.34 Cohort 145 145 CLI Femoropopliteal 121 (83%) Y 70% (12), 34% (36) NA 77% (12), 43% (36) 88% (12), 49% (36) NA
Sultan et al.35 Cohort 190 206 CLI Infrainguinal NA Y 73% (60) NA NA 73% (60) amputation-free survival 79% (60)
Köcher et al.54 Case note review 123 133 Claudication & CLI Femoropopliteal 115 (86%) Y 58% (12), 50% (24) NA NA 81% (12) for CLI NA
Marks et al.55 Cohort 108 116 NA Femoropopliteal 99 (85%) Y 59% (12) for technically successful procedures NA NA NA NA
Scott et al.15 Case note review 472 506 Claudication & CLI Infrainguinal 439 (87%) Y 45% (12) NA 76% (12) 75% (36) for CLI 55% (36) for CLI; 84% (36) for claudication
Akesson et al.33 Case note review 181 193 >95% CLI Infrainguinal 148 (77%) Y 45% (12) NA NA NA 62% patients died at a median of 17 (IQR 3-31) months after SIA
Scott et al.16 Case note review 104 105 Claudication & CLI