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Treating arterial occlusive disease
Angioplasty and stenting are cornerstone techniques in interventional radiology and have widespread non-vascular and vascular applications. The key skills and equipment choices remain largely the same, regardless of the site. This chapter assumes that you have already mastered the theory and techniques for getting to and crossing the lesion.
Basic principles
Refer back to the sections on equipment and the basic principles for further guidance on how to plan your case and choose the right gear ( Table 46.1 ).
Table 46.1
Rough guide to balloon and stent diameters
| Diameter (mm) | |
|---|---|
| Aorta | 10–15 |
| Common iliac | 8 |
| External iliac | 7 |
| CFA, proximal SFA | 6 |
| Distal SFA | 5 |
| Popliteal | 4 |
| Crural | 2–3 |
Indications
Indications for treatment vary according to the site of the disease. In most instances, the aim is to increase flow through the artery but in the carotid artery, the aim is almost always to prevent stroke rather than increase cerebral perfusion. A stenosis has to narrow the lumen by 50% before it becomes haemodynamically significant; a 50% diameter reduction results in a 75% reduction in the luminal cross-sectional area.
Remember that atherosclerotic plaque is incompressible and angioplasty works by tearing plaque and stretching the vessel wall.
The key determinants of success of angioplasty are:
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Arterial inflow and outflow
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Lesion morphology: stenosis or occlusion, length, calcification, plaque distribution
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Net lumen gain: a balance between vessel diameter and elastic recoil.
In simple terms, you can expect a good outcome for a focal stenosis in a large vessel with good inflow and run-off and a poor result in a long occlusion of a small, blind-ending vessel.
Consent
The risks of the procedure vary considerably from site to site. Consent always includes:
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Treatment options: alternative medical, surgical and interventional radiology options including combined strategies.
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Outcomes: probability of technical success, likelihood of the desired clinical result, e.g. relief of symptoms, likelihood of recurrence and subsequent management options. The latter is particularly important if one treatment precludes another option at a later date.
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Complications:
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The 3Bs of arterial access: bruising, bleeding and blockage, at the puncture site. Puncture site haematoma: 2–3%; commoner with larger sheaths, obesity and hypertension
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Generic angioplasty-related: vessel occlusion ≈1%, rupture or dissection, usually fixed by stent or stent graft, distal embolization 1–4%, often of no clinical importance
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Site-specific: obviously, emboli to the brain or the kidney are going to be much more important
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Remember that you must mention complications that the patient is likely to find significant even if they are uncommon, e.g. need for reconstructive vascular surgery, amputation and death. About 1% of patients will require emergency surgery as a result of your efforts. The consequences of complications or technical failure are likely to be greater in patients with critical ischaemia and more challenging, distal lesions.
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Specific complications will be considered on a site-by-site basis.
Procedure planning
Plan the procedure before starting, try to think through the likely steps and potential problems. Use the preintervention imaging to determine:
Access:
This relates to the optimal route to the lesion. The fewer curves the angioplasty balloon has to negotiate the better, so the shortest, straightest route is usually best. However, there may be reasons to choose an alternative approach or to have a back-up plan such as:
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When there is a local problem at the optimal access site
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When there are lesions above and below the common femoral artery (CFA) that require treatment, e.g. combined iliac and superficial femoral artery (SFA) disease.
Fortunately, improvements in equipment make angioplasty and stenting across the iliac bifurcation straightforward and thus facilitate treatment of bilateral lesions via a single puncture. The contralateral approach reduces your ability to ‘push’ through a very tight lesion. If necessary, simply make an antegrade puncture.
Equipment:
This will vary according to the site, indication for and nature of the intended treatment but it helps to consider the following in terms applicable to any case:
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Access: needles, wires and sheaths
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Angiography: catheters, wires and contrast
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Catheterization: catheters and wires needed to navigate to the target, cross the lesion and provide stable platform for treatment
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Treatment: angioplasty, balloons and stents- use the non-invasive imaging to estimate sizes
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Drugs: heparin, analgesia, etc.
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Closure: manual haemostasis or closure device
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Bail-out intervention: balloons, stents, stent grafts, thrombolysis and thrombosuction.
Treating arterial occlusive disease at specific sites
This section outlines the clinical and technical steps for successful angioplasty/stenting for the most common indications.
Aorta
Indications for treatment
Symptomatic aortic stenosis and coarctation:
Occasionally to allow passage/deployment of a device such as a stent graft or prosthetic aortic valve.
Consent issues
Focal aortic stenoses and coarctation are ideal for angioplasty and have a technical success rate exceeding 95%, with excellent 5-year patency rates. Stents can be reserved for cases of elastic recoil, flow-limiting dissection and recurrent stenoses.
Aortoiliac occlusions can be treated successfully but it should be borne in mind that these are much harder to treat and aortobifemoral grafting and aortic endarterectomy have excellent long-term patency.
Alarm
Retrograde recanalization of aortoiliac occlusion can lead to passage of the wire deep into the aortic wall, increasing the risk of dissection of important branch vessels and rupture.
Specific equipment
Either a single balloon, if the stenosis is clear of the bifurcation, or kissing balloons when the stenosis involves or is very close to the bifurcation. Remember that it is relatively easy to rupture the aorta (Laplace's law) and a 10–12 mm balloon will often be all that is needed.
There is a predilection for distal stenoses and occlusions to be very close to the origin of the inferior mesenteric artery (IMA).
Procedure
Unless you have ultrasound evidence of haemodynamically significant disease, pressure measurements are essential in the initial assessment of these lesions. Apparently severe stenoses on angiography frequently do not produce a significant pressure drop. As a generalization, if the catheter and wire pass through without a struggle, there is no significant pressure drop.
Tip
Measure the pressure gradient before placing a very large sheath.
Approach
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Unilateral femoral access will usually suffice for uncomplicated aortic stenosis.
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Bilateral femoral access is needed for lesions that involve:
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The aortic bifurcation, which should be treated with bilateral simultaneous common iliac balloons extending into the aortic bifurcation ( Fig. 46.1 )
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The IMA if a protection wire or balloon is needed; in these circumstances it is sometimes necessary to have brachial access.
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Brachial access is sometimes helpful to perform angiography to delineate an aortic stenosis and may be the best approach for traversing the lesion. In this case a rendezvous procedure is performed with angioplasty/stenting via a larger sheath from the femoral artery.
Tip
If there is a complete aortic occlusion, it sometimes helps to perform a run from the aortic arch to allow collateral perfusion of the distal circulation. Alternatively, inject contrast from both a femoral and a brachial catheter.
Equipment
If a lesion is in the distal infrarenal aorta, either use a balloon with a short taper or use kissing balloons. The taper on some 15–18-mm balloons extends 1–2 cm beyond the balloon marker and will wreak havoc in an iliac artery!
Catheterization
These lesions always look easy to cross but, in practice, it can be quite tricky to negotiate a 1–2-mm channel in a 12-mm artery. Safety first: once you have traversed the stenosis with a hydrophilic guidewire, this should be exchanged for a stiffer wire, e.g. an Amplatz super-stiff, prior to balloon insertion.
Runs
AP may be all that is required to traverse the lesion but consider additional oblique and lateral projections if you need to assess the aorta or identify the visceral vessels. If the IMA is the dominant intestinal vessel, occlusion must be avoided. In this case, use a protection wire or balloon in the IMA from the contralateral femoral artery or the brachial route.
Complications
The principal risk is distal embolization secondary to treatment of a large atherosclerotic plaque. Iliac trauma from the balloon is an avoidable risk with good angiographic technique.
Iliac arteries
Indications for treatment
Angioplasty and stenting are effective treatments for iliac atherosclerotic disease and have largely replaced aortofemoral bypass grafting. Indications include:
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symptomatic iliac stenosis and occlusion
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occasionally to improve inflow for a renal transplant or more distal bypass graft
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occasionally to allow passage/deployment of a device such as a stent graft or prosthetic aortic valve.
Consent issues
Initial technical success rates of 90–95% with 80% 5-year patency rates are achievable for stenoses <5 cm in length. Patency rates are lower for occlusions, heavily calcified lesions and stenotic disease that exceeds 10 cm in length, and primary stenting should be considered in these circumstances.
The most feared complications of iliac intervention are:
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Iliac rupture <1% managed using balloon occlusion to control bleeding and then stent grafting to repair the hole
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Symptomatic or potentially important distal embolization 1–2% managed by thrombus aspiration, stenting or surgical embolectomy/bypass.
Equipment
Iliac diameters are usually between 6 mm and 8 mm; however, take particular care in the external iliac artery (EIA) in females, which can be small and is prone to dissection, spasm and rupture. Remember to measure the size of the target vessel before dilation. Following angioplasty, if the EIA is narrowed throughout its length, it may well be secondary to vasospasm ( Fig. 46.2 ). Inject 100 mg of glyceryl trinitrate via the sheath and repeat the angiogram after a few minutes.
Approach
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Ipsilateral retrograde femoral access is the norm for straightforward stenosis/occlusion.
Tip
If the common femoral pulse cannot be felt, use an ultrasound-guided puncture to gain access. If the CFA is severely diseased, consider the contralateral approach with CFA angioplasty or a combined procedure with CFA endarterectomy – this way you do not even need to obtain haemostasis.
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Contralateral retrograde femoral access: Used in the presence of:
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tandem iliac and femoral disease
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iliac occlusion when the lumen cannot be re-entered retrogradely
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bilateral lesions if kissing balloons are not required and you do not want to make two punctures.
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Tip
You can use your favourite catheter to cross the aortic bifurcation but will need robust support to enter/cross a contralateral iliac occlusion; a braided Sidewinder 2 is a good starting point.
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Bilateral femoral access used for:
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Bilateral disease . This is essential for lesions involving the distal aorta and impinging on the origin of the common iliac artery ( Fig. 46.3 ). In this situation, simultaneous inflation of a balloon in each common iliac artery (CIA) origin (‘kissing balloons’) is needed.
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Protection of the internal iliac artery . The internal iliac artery may be occluded if angioplasty or stenting is performed across its origin. In a male patient with contralateral internal iliac artery (IIA) occlusion, this may cause impotence and you will not have done his buttock claudication any favours! Protect the internal iliac artery by inserting a guidewire into it from the contralateral side. If the internal iliac artery origin is diseased, then angioplasty it as well ( Fig. 46.3 ) – a male patient may be very grateful.
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Alarm
If the internal iliac is at risk of occlusion, discuss the risk of erectile dysfunction/ buttock claudication in male patients.
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Brachial access: seldom required but may be helpful for angiography.
Procedure
Pressure measurements ( Ch. 33 ) are invaluable for assessing the significance of iliac lesions before and after treatment. Pullback pressure measurements are particularly useful in multifocal disease, remember to keep an 0.018-inch wire across the lesion.
Catheterization
If you cannot negotiate a lesion from the retrograde approach use a Sidewinder or SOS catheter to manipulate over the bifurcation and try to cross the lesion from above (see Fig. 31.5 ). If successful, the wire can either be snared or manipulated through the sheath (see Fig. 36.4 ) or permit ipsilateral passage of balloons.
Runs:
When treating iliac occlusions perform a run with simultaneous injections from both the aorta and the ipsilateral sheath. Always perform obliques and use the run that shows the lesion in profile during attempted catheterization. When it comes to stent deployment use the projection which best delineates the anatomy, e.g. common iliac and IIA origins.
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