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Principles of endoluminal therapy
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Principles of endoluminal therapy
metallic implants cannot be scanned. The weaknesses of MRA are that it has a lower spatial resolution than CTA and calcified plaque is not clearly defined. An advantage is detecting low flow in distal lower limb arteries which can be easily missed on CTA. CT angiography is commonly used as first-line vascular imaging. It requires up to 150 ml of iodinated radiographic contrast.2 CTA is quick to perform and accessible out of hours in the emergency setting. Disadvantages include the nephrotoxic contrast load, radiation exposure and heavy vascular calcification that compromises accuracy of stenosis evaluation. New techniques are overcoming some of the difficulties with calcification. Examples of current CT arterial image quality are shown in Figures 4a and 6a.
Marcus Brooks John Hardman
Abstract This article provides an overview of the diagnostic and therapeutic roles of endoluminal therapy in vascular disease. The emphasis is on techniques for safely achieving arterial access, navigation through vessels and arterial closure. Non-invasive arterial imaging is the key to successful planning of endovascular procedures. Therapeutic endovascular procedures including angioplasty, stenting, embolization, thrombolysis, endovenous therapies and endovascular aortic aneurysm repair will be described. New technologies include drugcoated balloons and stents (DCBs/DESs) and intravascular ultrasound (IVUS). The changing role of endovascular aneurysm sealing (EvAS) is discussed.
Consent As with any invasive procedure the patient must be fully informed about the procedure. The potential benefit and the risks must be explained. All patients must be provided with sufficient written and verbal information, in a format that they can understand, to be able to weigh up risks and benefits.3,4 A history of previous allergic reaction (particularly to iodinated contrast) should be sought and renal function, full blood count and clotting checked. For local anaesthetic, the patient must be able to lie flat during and after the procedure.
Keywords Angiogram; angioplasty; embolization; EVAR; stent; thrombolysis
Imaging Access
Endoluminal procedures require careful advance planning. This is particularly important for endovascular abdominal aortic aneurysm repair (EVAR) where anatomical suitability is key to achieving durable aneurysm exclusion.1 The three imaging modalities used are duplex ultrasound (US), magnetic resonance angiography (MRA) and computed tomographic angiography (CTA). Duplex US is the least invasive investigation. It provides both anatomical (i.e. the visual grading of a stenosis) and physiological (i.e. velocity or flow) information. The weaknesses of duplex US are that it is highly operator dependent, and bowel gas or arterial wall calcification may prevent vessel visualization. Intravascular ultrasound, contrast agents and 3D ultrasound have improved the diagnostic ability of duplex US. Ultrasound machines are becoming smaller and more powerful. Many vascular surgeons perform their own venous duplex scans. MRA usually requires injection of 15e20 ml of gadolinium contrast via a peripheral vein. Time-of-flight sequences are available that do not require contrast. Scans can be reformatted into multiple planes making imaging review easier for multidisciplinary team review (Figure 1a). As with all MR scans, patients with pacemakers, metallic foreign bodies or recently placed
Standard arterial access is at the groin into the common femoral artery (CFA). It is recommended that ultrasound is used to ensure the puncture position is correct. Ultrasound is especially important when a closure device is planned. Ultrasound reduces complications by 50% in cardiology femoral access studies, and may reduce pain as local anaesthetic can be injected under ultrasound guidance around the CFA.5,6 Femoral access may be either antegrade (‘down the leg’) or retrograde (‘towards the abdomen’). Retrograde puncture is safer and allows access to the ipsilateral iliac arteries, the aorta, its branches and the contralateral leg. Antegrade puncture can be technically challenging, particularly in patients with high body mass index, but is preferred in superficial femoral artery or popliteal occlusion and when treating crural disease as it allows access down to the foot vessels. Retrograde puncture, with the diseased artery in the contralateral leg accessed by an ‘up and over’ approach across the aortic bifurcation, is shown in Figures 1d and 2a. The superficial femoral, axillary, brachial, radial and popliteal arteries are other sites for percutaneous arterial access. Arterial grafts or fistulas may be punctured and with the introduction of ‘hybrid’ operating theatres combined surgical and radiological procedures are becoming more common (with the artery surgically exposed). Venous procedures are performed via the common femoral, femoral, popliteal, calf, internal jugular or saphenous veins. In all cases a radiological wire (e.g. J guidewire) is advanced through a needle into the vessel lumen using the standard Seldinger technique. Once the wire is in position the needle is removed and gentle pressure maintained on the arterial puncture site for haemostasis. If it is anticipated that a number of different
Marcus Brooks MA MD FRCS is a Consultant Vascular Surgeon at North Bristol NHS Trust, Bristol, UK. Conflicts of interest: None declared. John Hardman MBBS MRCP FRCR is a Consultant Interventional Radiologist at Royal United Hospitals Bath NHS Foundation Trust and North Bristol NHS Trust, Bristol, UK. Conflicts of interest: None declared.
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Figure 1 Iliac angioplasty. (a) Reformatted MRA demonstrates a right iliac occlusion and left common iliac stenosis (b) Angioplasty was attempted, but resulted in dissection of the vessel. (c) Contralateral left iliac retrograde approach undertaken to angioplasty common iliac stenosis (d) Right common iliac was cannulated over the bifurcation and angioplastied (e) The wire was then snared from the right and (f) brought out through the right sheath (g). This enabled guidewires from both sides to be positioned into the aorta with placement of bilateral bare-metal iliac stents.
catheters or wires will be used during the course of the procedure, a vascular sheath is placed.
Diagnostic angiography Diagnostic angiography has largely been replaced by duplex US, MRA and CTA. It still has a role in patients with calcified vessels, typically diabetic patients and patients with end stage renal failure. It can also be helpful in patients in whom a hip or knee replacement causes artifact on MRA and CTA. The contrast load is often lower than that for a CT angiogram. Angiography can be performed via an access sheath or via a 4 or 5 French flush catheter. In most peripheral cases, digital subtraction angiogram (DSA) is performed. In patients with contrast allergy or severe renal failure carbon dioxide (CO2) may be used as an alternative contrast agent. CO2 must not be used above the diaphragm.
Navigation Once vessel access has been achieved the target vessel for therapy is reached using a combination of wire and catheter advancement. Intermittent fluoroscopic screening (arterial or deep venous procedures) or duplex ultrasound (superficial venous procedures) must be used whenever a wire is advanced in a vessel. Brief injections of contrast or intravascular ultrasound (IVUS) can also be helpful to confirm the vessel anatomy. In place of a standard guidewire it may be necessary to use a hydrophilic wire. Hydrophilic wires pass more freely up the arteries, especially when diseased. Different shaped catheters are used to navigate tortuous anatomy or directed into side branches; common examples of guide catheters are listed in Table 1. Longer curved sheaths are also available that are designed to cross the aortic bifurcation when the contralateral limb has been cannulated by an ‘up and over’ technique (see Figures 1d and 2a, Table 1). Long access sheaths are also used to deliver stent grafts into the visceral and renal arteries during complex endovascular aneurysm repair.
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Angioplasty Angioplasty describes the technique of balloon dilatation of a stenosed (‘narrowed’) or occluded (‘blocked’) arterial segment. Angioplasty is highly effective for treating atherosclerotic lesions (see Figures 1d and 2c). In patients with critical limb ischaemia, angioplasty has been compared to bypass surgery in just a single randomized control trial (BASIL 1). The peri-procedural complication rate and mortality were both lower for
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Figure 2 Superficial femoral artery (SFA) angioplasty. (a) Contralateral retrograde angiography of long right proximal SFA occlusion with a SFA stump that was recanalised (subintimal) and stented (b). Check angiography (c) revealed distal embolic ‘trashing’ of the popliteal artery with thrombus, which was successfully thrombolysed (d).
Figure 3 Venoplasty. (a) Initial imaging showing scarred femoral vein, occluded external iliac vein and large obturator vein acting as collateral venous drainage. (b) During venoplasty and stenting of occluded segment and (c) excellent result with flow through left iliac veins into inferior vena cava.
The guidewire may traverse an occluded arterial segment relatively easily or may require a ‘subintimal’ passage.8 Chronic, calcified occlusions, as often seen in patients with diabetes, are the most difficult to treat (see Figure 2a). Innovative use of
angioplasty, but during follow-up, angioplasty is more likely to need re-intervention.7 Angioplasty, particularly in patients with diabetes, can extend right down into the foot (pedal-plantar arch connecting anterior and posterior tibial arteries).
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Figure 4 Embolization. CT of pelvis of patient involved in a traffic accident, showing comminuted right pelvic fracture (a) with a large pelvic haematoma (b) (arrow). A diagnostic angiogram (c) demonstrates the bleeding vessel and this was selectively catheterized (d). The vessel was embolized with coils (e) and the bleeding controlled.
snares or re-entry devices can be used to facilitate arterial recanalization (see Figure 1e). There is ongoing development of atherectomy devices to de-bulk atheromatous plaque. To date, atherectomy devices remain experimental, with a high risk of vessel perforation. The Achilles heel of angioplasty is restenosis, due to a combination of myointimal hyperplasia (arterial wall smooth muscle proliferation) and atheroma progression. In the coronary arteries, drug-eluting stents (DES) have been shown to maintain better patency. In the peripheral circulation, the emphasis is on the benefit of using drug-coated balloons (DCBs). This is because early stent studies in the superficial femoral arteries had a high failure rate due to stent strut fracture. Several companies now market CE-marked and FDA-approved DCBs for the treatment of femoropopliteal arterial disease. Current evidence is that DCBs
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reduce vessel thrombosis and re-stenosis, but with a significantly higher initial cost than ‘plain old’ balloon angioplasty (‘POBA’).9 There is no good quality evidence that DCBs improve clinical endpoints.10
Venoplasty Recently there has been a resurgence of interest in the use of venoplasty to treat stenosed or occluded iliac veins in patients with severe symptoms from post thrombotic syndrome (Figure 3). In the acute setting of proximal deep vein thrombosis, venoplasty and stenting for a May-Thurner syndrome, compression of the left iliac vein as it passes under the common iliac artery, may be performed once the fresh thrombus has been cleared by thrombolysis, aspiration or mechanical device
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Figure 5 Embolization. (a) Three-centimeter diameter right internal iliac artery aneurysm (arrow) treated using an Amplatzer plug to occlude the artery distally and placement of a stent graft from the common to the external iliac arteries to occlude the inflow (b).
Figure 6 Endoleak. (a) Proximal (type 1a) endoleak shown on CTA. (b) Type III endoleak secondary to dislocation of graft limb (Aneuryx stent graft) and (c) rupture with stent graft in situ and massive type 1a endoleak secondary to stent graft migration distally.
following venoplasty, vessel recoil is seen, and this requires the placement of a stent. There are three types of peripheral stent: Balloon-mounted: typically stainless steel and mounted onto a balloon catheter, inflation of the balloon expands the stent. These stents have excellent radial force. Self-expanding: the stent is constructed of the ‘memory’ metal Nitinol and inserted constrained within a delivery sheath. As the sheath is pulled back the stent deploys. These stents are usually flexible.
(i.e. AngioJet, Boston Scientific). The recently reported ATTRACT trial, however, has questioned the overall benefit of thrombolysis plus anticoagulation over management with anticoagulation alone.11
Stent placement Complex superficial femoral artery lesions, those that are long or heavily calcified, have a poor long-term outcome due to restenosis. In addition, following angioplasty, and inevitably
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Percutaneous catheter-directed intra-arterial thrombolysis may also have a role in treating acute and sub-acute lower limb ischaemia.13
Commonly used catheters and sheaths for vascular interventions Catheter type
Shape and purpose
Cobra (Terumo)
Versatile catheter with ‘cobra-shaped’ end useful for navigation and vessel cannulation (i.e. SMA) Selective catheterization of major vessels arising from the aortic arch Short catheter (60 cm) with angled end useful for directing wires Stiff straight catheter with tapered end, useful for crossing tight stenosis or occlusion ‘Sheppard’s hook’ shaped catheter useful for cannulation of contralateral iliac artery or internal iliac artery Long catheter with hooked end and good torqueability.
Embolization
Sidewinder (Cordis) Van Schie (Cook) Van Andel (Cook Medical) SOS Omni (Angiodynamics) Vertebral Long sheath type
Embolization of a bleeding vessel or organ may be life-saving in major trauma (Figure 4) and acute gastrointestinal, pelvic, obstetric, or urinary tract haemorrhage. Other uses of intra-arterial embolization include localized administration of chemotherapy (trans-arterial chemoembolization; TACE), palliation of malignancy prior to surgical tumour resection, treatment of benign vascular tumour (e.g. uterine fibroid), treatment of some arteriovenous malformations, and occlusion of the internal iliac arteries as part of endovascular aortic repair (EVAR). There are a wide range of potential embolization materials including metallic coils, polyvinyl alcohol (PVA), gelfoam and synthetic particles. More recently, vascular plugs have become available (AmplatzerTM, St Jude Medical) that can embolize larger caliber vessels at their origin (Figure 5). The injection or placement of the embolic material or coil usually requires selective or super-selective catheter placement; accordingly, micro-catheters may be used to track into smaller branches through the standard ‘guide’ catheter.
Shape and purpose
Balkin (Cook) Long sheaths that can cross the bifurcation to Destination (Terumo) secure access to the contralateral limb or be placed in renal or visceral arteries.
Endovascular aortic aneurysm repair (EVAR)
Table 1
This technique is now the first choice for the treatment of abdominal aortic aneurysms in all but the youngest and fittest patients. Suitable cases are discussed at a multidisciplinary team meeting to ensure the procedure is technically/anatomically feasible and that the risk of aneurysm rupture exceeds the risk of the intervention. Standard EVAR requires adequate sealing zones for the stent graft in the immediate infra-renal aorta and the iliac arteries. Patients with neck angulation up to 90 degrees can be treated. As delivery systems have reduced in profile, most procedures can now be performed with ultrasound-guided percutaneous access and a closure device. Most patients are then discharged home the next day. If there is persistent flow seen into the aneurysm sac this is termed an endoleak (Table 2).14 Life-long follow-up by combination of duplex US and/or CT to detect stent graft migration, new endoleak or sac expansion (Figure 6) is recommended for all
Stent graft: these are balloon mounted or self-expandable stents covered in PTFE to make them impermeable. Stents are commonly used when a long occlusion has been treated as there is a high failure rate with angioplasty alone. Deep veins are stented when venography or ultrasound (IVUS) shows residual stenosis following venoplasty. Stenting of the iliac arteries (above the inguinal ligament) is common (see Figure 1g) but stents may also be placed within the aorta, superior vena cava (SVC) in cases of SVC obstruction, and in superficial femoral artery (SF) and popliteal arteries (see Figure 2b). If there is a significant risk of vessel perforation or embolization, then use of a covered stent (stent graft) is preferred. Covered stents are also used for aneurysm exclusion and when there has been a vessel injury. SFA stents for moderate length occlusions have been shown to be more effective than angioplasty alone at maintaining vessel patency at 12 months (RESILIENT trial, mean lesion length 7 cm).12 For long occlusions, limb salvage rates of around 80% are achieved. However, longer-term patency has not been fully established, and duplex US follow-up is suggested as in-stent restenosis can otherwise lead to stent thrombosis. Anti-platelet management is also important in maintaining patency. Stenting across hip joint or knee joint is usually best avoided since excessive movement may cause damage to the stent. Several drug-coated stents are in development with the most clinical experience reported for the ZilverÒ PTXÒ (Cook Medical). Recent data with up to 5 years follow-up shows improved patency compared to bare stents. Cost has limited the widespread adoption of this new technology.
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Endoleak classification Type
Description
Type 1
Leak between proximal graft and aneurysm wall. Further subdivided into 1a proximal and 1b distal Leak due to retrograde flow back into sac, e.g. via lumbar/inferior mesenteric arteries Leak between parts of the graft, e.g. between body and iliac limb Leak from porosity in stent graft Expanding aneurysm sac but with no contrast leak identified
Type 2 Type 3 Type 4 Type 5
Table 2
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cerebro-spinal fluid drainage appear to reduce the risk of paraplegia.
patients. Without follow-up and re-interventions, reported as necessary in up to 10% of patients, there is a risk of late aneurysm rupture despite initially successful endovascular repair.1 The EVAR 1 trial 15-year results report significant early survival advantage of EVAR, offset by later deaths, mostly due to aneurysm sac rupture (7% EVAR versus 1% Open).15 Contrastenhanced ultrasound can be beneficial in determining endoleak type, and localizing the inflow and outflow. The IMPROVE trial, a randomized trial comparing EVAR to open repair in 613 patients with ruptured abdominal aortic aneurysm, 3-year results support the use of EVAR for aneurysm rupture. Early benefits of rEVAR were greater probability of discharge home, shorter average hospital stay at 1 year, and lower cost. By 3 years’ the overall mortality has reduced (48% EVAR versus 56% Open). IMPROVE also suggests that local anaesthetic may be safer than general anaesthetic in patients with AAA rupture.
Complex endovascular aortic aneurysm repair (FEVAR/ BEVAR/ChEVAR) Up to one-third of patients have aneurysm anatomy that is unsuitable for treatment with standard (‘off-the-shelf’) stent grafts, usually due to lack of an adequate sealing zone. There are three endovascular technologies used in this setting. Fenestrated: custom-made stent grafts with holes positioned in the stent graft material to maintain access using bridging stents to the visceral and renal arteries. Branched: custommade or off-the-shelf stent grafts with branches to access visceral and/or renal and/or internal iliac arteries using bridging stents. Chimney: a standard stent graft is used with stents placed between the stent graft and the aortic wall to maintain flow to visceral and/or renal arteries. Using complex endovascular techniques, it is now possible to treat the most extensive thoraco-abdominal aortic aneurysms, including aneurysmal chronic type B aortic dissection, with a totally endovascular approach. Figure 8c shows a fenestrated cuff being placed within a standard EVAR to treat a proximal endoleak due to progressive neck expansion.
Endovascular aneurysm sealing (EVAS) This was developed as alternative to EVAR. The aneurysm sac is filled with two polymer filled bags with two stents lying between the bags maintaining blood flow to the legs (NellixTM, Endologix). The theoretical benefit of EVaS was that endoleak would be eliminated. Follow-up since 2013 has shown higher-thanexpected rates of leaks around the implant (Figure 7), stent migration and aneurysm enlargement. The use of this stent graft is now restricted to patients with favourable anatomy.
Antithrombotic medication All patients with peripheral arterial disease should be on an antiplatelet agent. Current NICE first-line recommendation is for Clopidogrel. Angioplasty is a low-risk procedure for haemorrhage; patients on a single antiplatelet medication for secondary cardiovascular prevention should continue this. Anticoagulation with warfarin or a direct oral anticoagulant (DOAC) should ideally be stopped. A safe INR for angioplasty is <1.5. Procedural anticoagulant therapy with intra-arterial unfractionated heparin is generally used when any intervention is performed. Dual antiplatelet therapy (aspirin and clopidogrel) is given for between 6 weeks and 6 months following SFA stent insertion (there are no studies of the optimal dose and duration of dual antiplatelet therapy in this setting).
Thoracic endovascular aortic aneurysm repair (TEVAR) Endovascular aortic stent grafts are also used to treat thoracic aneurysm, thoracic dissection and traumatic transection, (Figure 8 a and b).16 The risk of TEVAR appears lower than that of open thoracic aortic surgery, but the risk of stroke and paraplegia remains. Both the use of staged endovascular repair and
Closure After an endovascular procedure is completed, the wire/catheter(s) and finally the sheath are removed. For sheath sizes 4e7 French, arterial haemostasis is easily achieved by direct pressure. Closure devices, which plug the hole in the femoral artery, are widely used following coronary angiography and allow earlier mobilization. Their use is mandatory with larger arterial sheath sizes (i.e. percutaneous EVAR). Caution should be used with any closure device in the context of the patient with a high BMI or with small or heavily calcified vessels. In the absence of a randomized controlled trial, meta-analysis has shown no significant difference between closure devices or manual compression.17
Endovenous treatments Figure 7 Endoleak. CT scan showing endovascular aneurysm sealing (EVaS) with a type 1a endoleak anteriorly between polymer bags and aneurysm sac wall due to loss of seal in the aortic neck.
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The management of superficial venous disease has been revolutionized by the advent of percutaneous endovenous
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Figure 8 TEVAR and complex. (a) Volume-rendered CTA demonstrating a complex aneurysm of the thoracic aorta for TEVAR planning and (b) successful placement of an endovascular covered stent graft in the thoracic aorta. (c) Fenestrated aortic cuff to treat Type I endoleak due to progressive neck dilatation following standard EVAR.
Figure 9 Endovenous. (a) Tip of radiofrequency catheter positioned 2 cm from sapheno-femoral junction, Common femoral vein labelled, and (b) Infiltration of tumescent analgesia around vein prior to thermal ablation. Tip indicated by arrow in both transverse and longitudinal view.
Mechanochemical ablation uses a combination of a powered rotating wire and sclerosant agent to cause permanent damage to the intima for the vein. This can be a good choice of treatment for veins close to the skin. Cyanoacrylate glue uses tissue glue to occlude the vein. This product is currently expensive and this has limited its use.
techniques. These are ultrasound guided and can all be performed under local or no anaesthesia (Figure 9). The risk of complications is lower than open venous surgery and they are recommended by NICE as first-line treatment. Endothermal ablation: laser or radiofrequency thermal injury to permanently seal a truncal vein. As heat is used, a tumescent local anaesthetic solution must also be infiltrated along the vein to prevent pain or burns to adjacent structures (i.e. nerves or skin). Foam sclerotherapy: modification of Fegan’s sclerotherapy technique where by a sclerosant agent is mixed with air (or CO2) and injected into both truncal and tributary veins under ultrasound guidance. Foam sclerotherapy technique is simpler than endothermal ablation, but is also less durable, and carries the risks of foam embolization (visual disturbance or even rare stroke risk) and skin staining.
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Complications Complications with endovascular therapies are less frequent than for open arterial or venous surgery. Some bruising and discomfort at the access site is to be expected. For arterial procedures recognized complications including haematoma, dissection, pseudoaneurysm, distal embolization or occlusion. The need for an unplanned procedure or emergency surgery for limb salvage are quoted at around 1%.18
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The greatest risk is that of haemorrhage from either the access site or perforation of a vessel (Figure 10). Interventional radiology suites should have a ‘bail-out’ kit to manage major haemorrhage using occlusion balloons and covered stent grafts and an agreement with a surgical team for assistance should this be required (Figure 11). Groin puncture above the inguinal ligament significantly increases the risk of a life-threatening retroperitoneal bleed. Cardiologists now often use a radial artery approach, considered safer, especially in patients taking antithrombotic medication. In treating peripheral arterial disease there is risk of distal/ downstream embolization. The risk is greatest when treating acute disease when there can be superimposed thrombus. If embolization occurs, clot aspiration or intra-arterial catheterdirected thrombolysis can re-perfuse the limb without need for distal embolectomy or bypass (see Figure 2 c and d). Antegrade CFA puncture carries increased risk of SFA dissection due to needle and wire advancement being in the direction of blood flow. Dissection can be treated with either prolonged balloon inflation or an arterial stent. Pseudoaneurysm formation (persistent blood flow outside the vessel lumen) is a recognized late complication of arterial
puncture. It usually develops because of inadequate initial haemostasis (i.e. too short a period of compression or failed closure device). NICE supports ultrasound-guided thrombin injection over simple ultrasound-guided compression in uncomplicated cases, due to better technical success, shorter procedure time, lower cost, and better patient toleration.19 Surgery is on occasion still necessary. Less frequent procedural complications are nerve injury, infection, acute kidney injury, arteriovenous fistula and contrast reaction.
Conclusions Endoluminal therapies play an increasing role across medical specialties. Just as the treatment of coronary artery disease has been transformed by the advent of percutaneous coronary intervention, so modern vascular surgery is rapidly changing. Diagnostic angiography has been almost entirely replaced by non-invasive imaging modalities: duplex US, CTA and MRA. First-line therapies for patients with peripheral arterial disease, aortic disease or superficial venous disease, who warrant
Figure 10 Complications. (a) Puncture of external iliac artery above the inguinal ligament during coronary angiogram resulting in retroperitoneal haemorrhage displacing right kidney. (b) Volume-rendered 3D CT showing CFA pseudoaneurysm.
Figure 11 Complications. (a) Angioplasty of occluded left common iliac artery. (b) Vessel rupture with contrast extravasation. (c) Successful treatment with covered stent graft.
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intervention, are now likely to be endoluminal procedures, not open surgery. This is of especial benefit when so many vascular patients are elderly, frail and have multiple co-morbidities. This change has resulted in less procedural morbidity and mortality, with consequent reduction in length of hospital stay. There is, however, increased need for post-procedure surveillance and re-intervention than following open surgery. The vascular specialist needs to be able to work with multi-planar reconstructed images, have mastered endoluminal techniques and be trained in vascular ultrasound (duplex). Interventions are increasingly complex and can only be safely delivered by skilled multidisciplinary teams including trained operators, imaging specialists, vascular scientists, radiographers and specialist nurses. The basic principles of safe access, safe navigation to the vessel of interest and safe closure of the access vessel, remain key to success. A
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Glossary of terms
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DSA
Arterial sheath Hydrophilic wire Inflation device Flush catheter
French (Fr) size Micro catheter Low-profile system
Subintimal approach
2
3
4 5
Digital subtraction angiography; an initial image subtracted from an image acquired after contrast has been injected; thus leaving only arterial supply and removing bone, soft tissue etc. Sheath, with a haemostatic valve and side-branch to flush, placed to allow easy catheter and wire exchanges The name means ‘water loving’. Once wet, the coating is extremely slippery. (Terumo e Terumo, ZipWire e Boston Scientific) Means of inflating balloon to higher pressure than might be achieved by hand/syringe alone Catheter with side holes to allow the faster ejection of contrast for angiography. Two commonly used types are the coiled end ‘Pig tail’ and straight ‘Flush’ catheters External catheter circumference in mm. Commonly, 4 e7Fr Catheters in region of 0.021e0.02800 inch, passed through standard catheter to gain closer access to region of interest Balloon angioplasty performed via a 4F sheath and a small calibre 0.018 wire. The smaller sheath reduces post-procedure immobility and allows a greater proportion of day cases In long chronic occlusions, a hydrophilic wire can be passed between the intima and media creating a dissecting channel that is then angioplastied and/or stented to create a new flow channel
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9
10
11
12
13
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REFERENCES 1 EVAR trial participants. Endovascular aneurysm repair versus open repair in patients with abdominal aortic aneurysm (EVAR
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trial 1): randomised controlled trial. Lancet 2005; 365: 2179e86. Fotiadis N, Kyriakides C, Bent C, et al. 64-section CT angiography in patients with critical limb ischaemia and severe claudication: comparison with digital subtractive angiography. Clin Radiol 2011; 66: 945e52. The Royal College of Radiologists Standards for patient consent particular to radiology. London: The Royal College of Radiologists, 2005. http://www.nrls.npsa.nhs.uk/resources/?entryid45¼73612. Accessed 12th February, 2015. Seto AH, Abu-Fadel MS, Sparling JM, et al. Real-time ultrasound guidance facilitates femoral arterial access and reduces vascular complications: FAUST (Femoral Arterial Access With Ultrasound Trial). JACC Cardiovasc Interv 2010; 3: 751e8. Spiliopoulos S, Katsanos K, Diamantopoulos A, et al. Does ultrasound guided lidocaine injection improve local anesthesia before femoral artery catheterization? Clin Radiol 2011; 66: 449e55. Bradbury AW, Adam DJ, Bell J, et al. Bypass versus Angioplasty in Severe Ischaemia of the Leg (BASIL) trial: an intention-to-treat analysis of amputation-free and overall survival in patients randomized to a bypass surgery-first or a balloon angioplasty-first revascularization strategy. J Vasc Surg, 2010; 5Se17. Bolia A, Miles KA, Brennan J, Bell PRF. Percutaneous transluminal angioplasty of occlusions of the SFA by subintimal dissection. Cardiovasc Interven Radiol 1990; 13: 357e63. Tepe G, Laird J, Schneider P, et al. Drug-coated balloon versus standard percutaneous transluminal angioplasty for the treatment of superficial femoral and/or popliteal peripheral artery disease: 12-month results from the IN.PACT SFA randomized trial. Circulation 2015; 131: 495e502. Kayssi A, Al-Atassi T, Oreopoulos G, Roche-Nagle G, Tan K, Rajan DK. Uncoated balloon angioplasty versus drug-eluting balloon angioplasty for peripheral arterial disease of the lower limbs. Cochrane Database Syst Rev, 2016; CD011319 https://doi. org/10.1002/14651858.CD011319.pub2. Vendantham S, Goldhaber SZ, Julian JA, et al. Pharmacomechanical catheter-directed thrombolysis for deep vein thrombosis. N Engl J Med 2017; 377: 2240e52. Laird John R, Katzen Barry T, Scheinert Dierk, et al. Nitinol stent implantation versus balloon angioplasty for lesions in the superficial femoral artery and proximal popliteal artery twelve-month results from the RESILIENT randomized trial. Circ e Cardiovasc Interventions 2010; 3: 267e76. Karnabatidis D, Spiliopoulos S, Tsetis D, et al. Quality improvement guidelines for percutaneous catheter-directed intra-arterial thrombolysis and mechanical thrombectomy for acute lower-limb ischemia. Cardiovasc Interven Radiol 2011; 34: 1123e36. White GH, Yu W, May J, et al. Endoleak as a complication of endoluminal grafting of abdominal aortic aneurysms: classification, incidence, diagnosis, and management. J Endovasc Surg 1997; 4: 152e68. Patel R, Sweeting M, Powell J, et al. Endovascular versus open repair of abdominal aortic aneurysm in 15-years’ follow-up of the
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UK endovascular aneurysm repair trial 1 (EVAR trial 1): a randomised controlled trial. Lancet 2016; 388: 2366e74. 16 Fattori R, Russo V, Lovato L. Endovascular management of thoracic aortic aneurysms. Cardiovasc Interven Radiol 2011; 34: 1137e42. 17 Das R, Ahmed K, Athanasiou T, et al. Arterial closure devices versus manual compression for femoral haemostasis in interventional radiological procedures: a systematic review and meta-analysis. Cardiovasc Interven Radiol 2011; 34: 723e38. 18 The British Society of Interventional Radiology. Third BIAS report 2008. Oxfordshire: Dendrite Clinical Systems, 2008.
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19 Ahmad F, Turner S, Torrie P, et al. Iatrogenic femoral artery pseudo-aneurysms a review of current methods of diagnosis and treatment. Clin Radiol 2008; 63: 1310e6.
Acknowledgement With acknowledgement to Katherine Augustine, Nathan Manghat and Hashem Baraket co-authors of a previous version of this article. KA and NM supplied most the illustrations. UK Endovascular Trainees (UKETS) are credited for the principles of safe access, navigation and closure.
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Principles of endoluminal therapy
metallic implants cannot be scanned. The weaknesses of MRA are that it has a lower spatial resolution than CTA and calcified plaque is not clearly defined. An advantage is detecting low flow in distal lower limb arteries which can be easily missed on CTA. CT angiography is commonly used as first-line vascular imaging. It requires up to 150 ml of iodinated radiographic contrast.2 CTA is quick to perform and accessible out of hours in the emergency setting. Disadvantages include the nephrotoxic contrast load, radiation exposure and heavy vascular calcification that compromises accuracy of stenosis evaluation. New techniques are overcoming some of the difficulties with calcification. Examples of current CT arterial image quality are shown in Figures 4a and 6a.
Marcus Brooks John Hardman
Abstract This article provides an overview of the diagnostic and therapeutic roles of endoluminal therapy in vascular disease. The emphasis is on techniques for safely achieving arterial access, navigation through vessels and arterial closure. Non-invasive arterial imaging is the key to successful planning of endovascular procedures. Therapeutic endovascular procedures including angioplasty, stenting, embolization, thrombolysis, endovenous therapies and endovascular aortic aneurysm repair will be described. New technologies include drugcoated balloons and stents (DCBs/DESs) and intravascular ultrasound (IVUS). The changing role of endovascular aneurysm sealing (EvAS) is discussed.
Consent As with any invasive procedure the patient must be fully informed about the procedure. The potential benefit and the risks must be explained. All patients must be provided with sufficient written and verbal information, in a format that they can understand, to be able to weigh up risks and benefits.3,4 A history of previous allergic reaction (particularly to iodinated contrast) should be sought and renal function, full blood count and clotting checked. For local anaesthetic, the patient must be able to lie flat during and after the procedure.
Keywords Angiogram; angioplasty; embolization; EVAR; stent; thrombolysis
Imaging Access
Endoluminal procedures require careful advance planning. This is particularly important for endovascular abdominal aortic aneurysm repair (EVAR) where anatomical suitability is key to achieving durable aneurysm exclusion.1 The three imaging modalities used are duplex ultrasound (US), magnetic resonance angiography (MRA) and computed tomographic angiography (CTA). Duplex US is the least invasive investigation. It provides both anatomical (i.e. the visual grading of a stenosis) and physiological (i.e. velocity or flow) information. The weaknesses of duplex US are that it is highly operator dependent, and bowel gas or arterial wall calcification may prevent vessel visualization. Intravascular ultrasound, contrast agents and 3D ultrasound have improved the diagnostic ability of duplex US. Ultrasound machines are becoming smaller and more powerful. Many vascular surgeons perform their own venous duplex scans. MRA usually requires injection of 15e20 ml of gadolinium contrast via a peripheral vein. Time-of-flight sequences are available that do not require contrast. Scans can be reformatted into multiple planes making imaging review easier for multidisciplinary team review (Figure 1a). As with all MR scans, patients with pacemakers, metallic foreign bodies or recently placed
Standard arterial access is at the groin into the common femoral artery (CFA). It is recommended that ultrasound is used to ensure the puncture position is correct. Ultrasound is especially important when a closure device is planned. Ultrasound reduces complications by 50% in cardiology femoral access studies, and may reduce pain as local anaesthetic can be injected under ultrasound guidance around the CFA.5,6 Femoral access may be either antegrade (‘down the leg’) or retrograde (‘towards the abdomen’). Retrograde puncture is safer and allows access to the ipsilateral iliac arteries, the aorta, its branches and the contralateral leg. Antegrade puncture can be technically challenging, particularly in patients with high body mass index, but is preferred in superficial femoral artery or popliteal occlusion and when treating crural disease as it allows access down to the foot vessels. Retrograde puncture, with the diseased artery in the contralateral leg accessed by an ‘up and over’ approach across the aortic bifurcation, is shown in Figures 1d and 2a. The superficial femoral, axillary, brachial, radial and popliteal arteries are other sites for percutaneous arterial access. Arterial grafts or fistulas may be punctured and with the introduction of ‘hybrid’ operating theatres combined surgical and radiological procedures are becoming more common (with the artery surgically exposed). Venous procedures are performed via the common femoral, femoral, popliteal, calf, internal jugular or saphenous veins. In all cases a radiological wire (e.g. J guidewire) is advanced through a needle into the vessel lumen using the standard Seldinger technique. Once the wire is in position the needle is removed and gentle pressure maintained on the arterial puncture site for haemostasis. If it is anticipated that a number of different
Marcus Brooks MA MD FRCS is a Consultant Vascular Surgeon at North Bristol NHS Trust, Bristol, UK. Conflicts of interest: None declared. John Hardman MBBS MRCP FRCR is a Consultant Interventional Radiologist at Royal United Hospitals Bath NHS Foundation Trust and North Bristol NHS Trust, Bristol, UK. Conflicts of interest: None declared.
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Figure 1 Iliac angioplasty. (a) Reformatted MRA demonstrates a right iliac occlusion and left common iliac stenosis (b) Angioplasty was attempted, but resulted in dissection of the vessel. (c) Contralateral left iliac retrograde approach undertaken to angioplasty common iliac stenosis (d) Right common iliac was cannulated over the bifurcation and angioplastied (e) The wire was then snared from the right and (f) brought out through the right sheath (g). This enabled guidewires from both sides to be positioned into the aorta with placement of bilateral bare-metal iliac stents.
catheters or wires will be used during the course of the procedure, a vascular sheath is placed.
Diagnostic angiography Diagnostic angiography has largely been replaced by duplex US, MRA and CTA. It still has a role in patients with calcified vessels, typically diabetic patients and patients with end stage renal failure. It can also be helpful in patients in whom a hip or knee replacement causes artifact on MRA and CTA. The contrast load is often lower than that for a CT angiogram. Angiography can be performed via an access sheath or via a 4 or 5 French flush catheter. In most peripheral cases, digital subtraction angiogram (DSA) is performed. In patients with contrast allergy or severe renal failure carbon dioxide (CO2) may be used as an alternative contrast agent. CO2 must not be used above the diaphragm.
Navigation Once vessel access has been achieved the target vessel for therapy is reached using a combination of wire and catheter advancement. Intermittent fluoroscopic screening (arterial or deep venous procedures) or duplex ultrasound (superficial venous procedures) must be used whenever a wire is advanced in a vessel. Brief injections of contrast or intravascular ultrasound (IVUS) can also be helpful to confirm the vessel anatomy. In place of a standard guidewire it may be necessary to use a hydrophilic wire. Hydrophilic wires pass more freely up the arteries, especially when diseased. Different shaped catheters are used to navigate tortuous anatomy or directed into side branches; common examples of guide catheters are listed in Table 1. Longer curved sheaths are also available that are designed to cross the aortic bifurcation when the contralateral limb has been cannulated by an ‘up and over’ technique (see Figures 1d and 2a, Table 1). Long access sheaths are also used to deliver stent grafts into the visceral and renal arteries during complex endovascular aneurysm repair.
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Angioplasty Angioplasty describes the technique of balloon dilatation of a stenosed (‘narrowed’) or occluded (‘blocked’) arterial segment. Angioplasty is highly effective for treating atherosclerotic lesions (see Figures 1d and 2c). In patients with critical limb ischaemia, angioplasty has been compared to bypass surgery in just a single randomized control trial (BASIL 1). The peri-procedural complication rate and mortality were both lower for
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Figure 2 Superficial femoral artery (SFA) angioplasty. (a) Contralateral retrograde angiography of long right proximal SFA occlusion with a SFA stump that was recanalised (subintimal) and stented (b). Check angiography (c) revealed distal embolic ‘trashing’ of the popliteal artery with thrombus, which was successfully thrombolysed (d).
Figure 3 Venoplasty. (a) Initial imaging showing scarred femoral vein, occluded external iliac vein and large obturator vein acting as collateral venous drainage. (b) During venoplasty and stenting of occluded segment and (c) excellent result with flow through left iliac veins into inferior vena cava.
The guidewire may traverse an occluded arterial segment relatively easily or may require a ‘subintimal’ passage.8 Chronic, calcified occlusions, as often seen in patients with diabetes, are the most difficult to treat (see Figure 2a). Innovative use of
angioplasty, but during follow-up, angioplasty is more likely to need re-intervention.7 Angioplasty, particularly in patients with diabetes, can extend right down into the foot (pedal-plantar arch connecting anterior and posterior tibial arteries).
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Figure 4 Embolization. CT of pelvis of patient involved in a traffic accident, showing comminuted right pelvic fracture (a) with a large pelvic haematoma (b) (arrow). A diagnostic angiogram (c) demonstrates the bleeding vessel and this was selectively catheterized (d). The vessel was embolized with coils (e) and the bleeding controlled.
snares or re-entry devices can be used to facilitate arterial recanalization (see Figure 1e). There is ongoing development of atherectomy devices to de-bulk atheromatous plaque. To date, atherectomy devices remain experimental, with a high risk of vessel perforation. The Achilles heel of angioplasty is restenosis, due to a combination of myointimal hyperplasia (arterial wall smooth muscle proliferation) and atheroma progression. In the coronary arteries, drug-eluting stents (DES) have been shown to maintain better patency. In the peripheral circulation, the emphasis is on the benefit of using drug-coated balloons (DCBs). This is because early stent studies in the superficial femoral arteries had a high failure rate due to stent strut fracture. Several companies now market CE-marked and FDA-approved DCBs for the treatment of femoropopliteal arterial disease. Current evidence is that DCBs
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reduce vessel thrombosis and re-stenosis, but with a significantly higher initial cost than ‘plain old’ balloon angioplasty (‘POBA’).9 There is no good quality evidence that DCBs improve clinical endpoints.10
Venoplasty Recently there has been a resurgence of interest in the use of venoplasty to treat stenosed or occluded iliac veins in patients with severe symptoms from post thrombotic syndrome (Figure 3). In the acute setting of proximal deep vein thrombosis, venoplasty and stenting for a May-Thurner syndrome, compression of the left iliac vein as it passes under the common iliac artery, may be performed once the fresh thrombus has been cleared by thrombolysis, aspiration or mechanical device
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Figure 5 Embolization. (a) Three-centimeter diameter right internal iliac artery aneurysm (arrow) treated using an Amplatzer plug to occlude the artery distally and placement of a stent graft from the common to the external iliac arteries to occlude the inflow (b).
Figure 6 Endoleak. (a) Proximal (type 1a) endoleak shown on CTA. (b) Type III endoleak secondary to dislocation of graft limb (Aneuryx stent graft) and (c) rupture with stent graft in situ and massive type 1a endoleak secondary to stent graft migration distally.
following venoplasty, vessel recoil is seen, and this requires the placement of a stent. There are three types of peripheral stent: Balloon-mounted: typically stainless steel and mounted onto a balloon catheter, inflation of the balloon expands the stent. These stents have excellent radial force. Self-expanding: the stent is constructed of the ‘memory’ metal Nitinol and inserted constrained within a delivery sheath. As the sheath is pulled back the stent deploys. These stents are usually flexible.
(i.e. AngioJet, Boston Scientific). The recently reported ATTRACT trial, however, has questioned the overall benefit of thrombolysis plus anticoagulation over management with anticoagulation alone.11
Stent placement Complex superficial femoral artery lesions, those that are long or heavily calcified, have a poor long-term outcome due to restenosis. In addition, following angioplasty, and inevitably
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Percutaneous catheter-directed intra-arterial thrombolysis may also have a role in treating acute and sub-acute lower limb ischaemia.13
Commonly used catheters and sheaths for vascular interventions Catheter type
Shape and purpose
Cobra (Terumo)
Versatile catheter with ‘cobra-shaped’ end useful for navigation and vessel cannulation (i.e. SMA) Selective catheterization of major vessels arising from the aortic arch Short catheter (60 cm) with angled end useful for directing wires Stiff straight catheter with tapered end, useful for crossing tight stenosis or occlusion ‘Sheppard’s hook’ shaped catheter useful for cannulation of contralateral iliac artery or internal iliac artery Long catheter with hooked end and good torqueability.
Embolization
Sidewinder (Cordis) Van Schie (Cook) Van Andel (Cook Medical) SOS Omni (Angiodynamics) Vertebral Long sheath type
Embolization of a bleeding vessel or organ may be life-saving in major trauma (Figure 4) and acute gastrointestinal, pelvic, obstetric, or urinary tract haemorrhage. Other uses of intra-arterial embolization include localized administration of chemotherapy (trans-arterial chemoembolization; TACE), palliation of malignancy prior to surgical tumour resection, treatment of benign vascular tumour (e.g. uterine fibroid), treatment of some arteriovenous malformations, and occlusion of the internal iliac arteries as part of endovascular aortic repair (EVAR). There are a wide range of potential embolization materials including metallic coils, polyvinyl alcohol (PVA), gelfoam and synthetic particles. More recently, vascular plugs have become available (AmplatzerTM, St Jude Medical) that can embolize larger caliber vessels at their origin (Figure 5). The injection or placement of the embolic material or coil usually requires selective or super-selective catheter placement; accordingly, micro-catheters may be used to track into smaller branches through the standard ‘guide’ catheter.
Shape and purpose
Balkin (Cook) Long sheaths that can cross the bifurcation to Destination (Terumo) secure access to the contralateral limb or be placed in renal or visceral arteries.
Endovascular aortic aneurysm repair (EVAR)
Table 1
This technique is now the first choice for the treatment of abdominal aortic aneurysms in all but the youngest and fittest patients. Suitable cases are discussed at a multidisciplinary team meeting to ensure the procedure is technically/anatomically feasible and that the risk of aneurysm rupture exceeds the risk of the intervention. Standard EVAR requires adequate sealing zones for the stent graft in the immediate infra-renal aorta and the iliac arteries. Patients with neck angulation up to 90 degrees can be treated. As delivery systems have reduced in profile, most procedures can now be performed with ultrasound-guided percutaneous access and a closure device. Most patients are then discharged home the next day. If there is persistent flow seen into the aneurysm sac this is termed an endoleak (Table 2).14 Life-long follow-up by combination of duplex US and/or CT to detect stent graft migration, new endoleak or sac expansion (Figure 6) is recommended for all
Stent graft: these are balloon mounted or self-expandable stents covered in PTFE to make them impermeable. Stents are commonly used when a long occlusion has been treated as there is a high failure rate with angioplasty alone. Deep veins are stented when venography or ultrasound (IVUS) shows residual stenosis following venoplasty. Stenting of the iliac arteries (above the inguinal ligament) is common (see Figure 1g) but stents may also be placed within the aorta, superior vena cava (SVC) in cases of SVC obstruction, and in superficial femoral artery (SF) and popliteal arteries (see Figure 2b). If there is a significant risk of vessel perforation or embolization, then use of a covered stent (stent graft) is preferred. Covered stents are also used for aneurysm exclusion and when there has been a vessel injury. SFA stents for moderate length occlusions have been shown to be more effective than angioplasty alone at maintaining vessel patency at 12 months (RESILIENT trial, mean lesion length 7 cm).12 For long occlusions, limb salvage rates of around 80% are achieved. However, longer-term patency has not been fully established, and duplex US follow-up is suggested as in-stent restenosis can otherwise lead to stent thrombosis. Anti-platelet management is also important in maintaining patency. Stenting across hip joint or knee joint is usually best avoided since excessive movement may cause damage to the stent. Several drug-coated stents are in development with the most clinical experience reported for the ZilverÒ PTXÒ (Cook Medical). Recent data with up to 5 years follow-up shows improved patency compared to bare stents. Cost has limited the widespread adoption of this new technology.
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Endoleak classification Type
Description
Type 1
Leak between proximal graft and aneurysm wall. Further subdivided into 1a proximal and 1b distal Leak due to retrograde flow back into sac, e.g. via lumbar/inferior mesenteric arteries Leak between parts of the graft, e.g. between body and iliac limb Leak from porosity in stent graft Expanding aneurysm sac but with no contrast leak identified
Type 2 Type 3 Type 4 Type 5
Table 2
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cerebro-spinal fluid drainage appear to reduce the risk of paraplegia.
patients. Without follow-up and re-interventions, reported as necessary in up to 10% of patients, there is a risk of late aneurysm rupture despite initially successful endovascular repair.1 The EVAR 1 trial 15-year results report significant early survival advantage of EVAR, offset by later deaths, mostly due to aneurysm sac rupture (7% EVAR versus 1% Open).15 Contrastenhanced ultrasound can be beneficial in determining endoleak type, and localizing the inflow and outflow. The IMPROVE trial, a randomized trial comparing EVAR to open repair in 613 patients with ruptured abdominal aortic aneurysm, 3-year results support the use of EVAR for aneurysm rupture. Early benefits of rEVAR were greater probability of discharge home, shorter average hospital stay at 1 year, and lower cost. By 3 years’ the overall mortality has reduced (48% EVAR versus 56% Open). IMPROVE also suggests that local anaesthetic may be safer than general anaesthetic in patients with AAA rupture.
Complex endovascular aortic aneurysm repair (FEVAR/ BEVAR/ChEVAR) Up to one-third of patients have aneurysm anatomy that is unsuitable for treatment with standard (‘off-the-shelf’) stent grafts, usually due to lack of an adequate sealing zone. There are three endovascular technologies used in this setting. Fenestrated: custom-made stent grafts with holes positioned in the stent graft material to maintain access using bridging stents to the visceral and renal arteries. Branched: custommade or off-the-shelf stent grafts with branches to access visceral and/or renal and/or internal iliac arteries using bridging stents. Chimney: a standard stent graft is used with stents placed between the stent graft and the aortic wall to maintain flow to visceral and/or renal arteries. Using complex endovascular techniques, it is now possible to treat the most extensive thoraco-abdominal aortic aneurysms, including aneurysmal chronic type B aortic dissection, with a totally endovascular approach. Figure 8c shows a fenestrated cuff being placed within a standard EVAR to treat a proximal endoleak due to progressive neck expansion.
Endovascular aneurysm sealing (EVAS) This was developed as alternative to EVAR. The aneurysm sac is filled with two polymer filled bags with two stents lying between the bags maintaining blood flow to the legs (NellixTM, Endologix). The theoretical benefit of EVaS was that endoleak would be eliminated. Follow-up since 2013 has shown higher-thanexpected rates of leaks around the implant (Figure 7), stent migration and aneurysm enlargement. The use of this stent graft is now restricted to patients with favourable anatomy.
Antithrombotic medication All patients with peripheral arterial disease should be on an antiplatelet agent. Current NICE first-line recommendation is for Clopidogrel. Angioplasty is a low-risk procedure for haemorrhage; patients on a single antiplatelet medication for secondary cardiovascular prevention should continue this. Anticoagulation with warfarin or a direct oral anticoagulant (DOAC) should ideally be stopped. A safe INR for angioplasty is <1.5. Procedural anticoagulant therapy with intra-arterial unfractionated heparin is generally used when any intervention is performed. Dual antiplatelet therapy (aspirin and clopidogrel) is given for between 6 weeks and 6 months following SFA stent insertion (there are no studies of the optimal dose and duration of dual antiplatelet therapy in this setting).
Thoracic endovascular aortic aneurysm repair (TEVAR) Endovascular aortic stent grafts are also used to treat thoracic aneurysm, thoracic dissection and traumatic transection, (Figure 8 a and b).16 The risk of TEVAR appears lower than that of open thoracic aortic surgery, but the risk of stroke and paraplegia remains. Both the use of staged endovascular repair and
Closure After an endovascular procedure is completed, the wire/catheter(s) and finally the sheath are removed. For sheath sizes 4e7 French, arterial haemostasis is easily achieved by direct pressure. Closure devices, which plug the hole in the femoral artery, are widely used following coronary angiography and allow earlier mobilization. Their use is mandatory with larger arterial sheath sizes (i.e. percutaneous EVAR). Caution should be used with any closure device in the context of the patient with a high BMI or with small or heavily calcified vessels. In the absence of a randomized controlled trial, meta-analysis has shown no significant difference between closure devices or manual compression.17
Endovenous treatments Figure 7 Endoleak. CT scan showing endovascular aneurysm sealing (EVaS) with a type 1a endoleak anteriorly between polymer bags and aneurysm sac wall due to loss of seal in the aortic neck.
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The management of superficial venous disease has been revolutionized by the advent of percutaneous endovenous
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Figure 8 TEVAR and complex. (a) Volume-rendered CTA demonstrating a complex aneurysm of the thoracic aorta for TEVAR planning and (b) successful placement of an endovascular covered stent graft in the thoracic aorta. (c) Fenestrated aortic cuff to treat Type I endoleak due to progressive neck dilatation following standard EVAR.
Figure 9 Endovenous. (a) Tip of radiofrequency catheter positioned 2 cm from sapheno-femoral junction, Common femoral vein labelled, and (b) Infiltration of tumescent analgesia around vein prior to thermal ablation. Tip indicated by arrow in both transverse and longitudinal view.
Mechanochemical ablation uses a combination of a powered rotating wire and sclerosant agent to cause permanent damage to the intima for the vein. This can be a good choice of treatment for veins close to the skin. Cyanoacrylate glue uses tissue glue to occlude the vein. This product is currently expensive and this has limited its use.
techniques. These are ultrasound guided and can all be performed under local or no anaesthesia (Figure 9). The risk of complications is lower than open venous surgery and they are recommended by NICE as first-line treatment. Endothermal ablation: laser or radiofrequency thermal injury to permanently seal a truncal vein. As heat is used, a tumescent local anaesthetic solution must also be infiltrated along the vein to prevent pain or burns to adjacent structures (i.e. nerves or skin). Foam sclerotherapy: modification of Fegan’s sclerotherapy technique where by a sclerosant agent is mixed with air (or CO2) and injected into both truncal and tributary veins under ultrasound guidance. Foam sclerotherapy technique is simpler than endothermal ablation, but is also less durable, and carries the risks of foam embolization (visual disturbance or even rare stroke risk) and skin staining.
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Complications Complications with endovascular therapies are less frequent than for open arterial or venous surgery. Some bruising and discomfort at the access site is to be expected. For arterial procedures recognized complications including haematoma, dissection, pseudoaneurysm, distal embolization or occlusion. The need for an unplanned procedure or emergency surgery for limb salvage are quoted at around 1%.18
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The greatest risk is that of haemorrhage from either the access site or perforation of a vessel (Figure 10). Interventional radiology suites should have a ‘bail-out’ kit to manage major haemorrhage using occlusion balloons and covered stent grafts and an agreement with a surgical team for assistance should this be required (Figure 11). Groin puncture above the inguinal ligament significantly increases the risk of a life-threatening retroperitoneal bleed. Cardiologists now often use a radial artery approach, considered safer, especially in patients taking antithrombotic medication. In treating peripheral arterial disease there is risk of distal/ downstream embolization. The risk is greatest when treating acute disease when there can be superimposed thrombus. If embolization occurs, clot aspiration or intra-arterial catheterdirected thrombolysis can re-perfuse the limb without need for distal embolectomy or bypass (see Figure 2 c and d). Antegrade CFA puncture carries increased risk of SFA dissection due to needle and wire advancement being in the direction of blood flow. Dissection can be treated with either prolonged balloon inflation or an arterial stent. Pseudoaneurysm formation (persistent blood flow outside the vessel lumen) is a recognized late complication of arterial
puncture. It usually develops because of inadequate initial haemostasis (i.e. too short a period of compression or failed closure device). NICE supports ultrasound-guided thrombin injection over simple ultrasound-guided compression in uncomplicated cases, due to better technical success, shorter procedure time, lower cost, and better patient toleration.19 Surgery is on occasion still necessary. Less frequent procedural complications are nerve injury, infection, acute kidney injury, arteriovenous fistula and contrast reaction.
Conclusions Endoluminal therapies play an increasing role across medical specialties. Just as the treatment of coronary artery disease has been transformed by the advent of percutaneous coronary intervention, so modern vascular surgery is rapidly changing. Diagnostic angiography has been almost entirely replaced by non-invasive imaging modalities: duplex US, CTA and MRA. First-line therapies for patients with peripheral arterial disease, aortic disease or superficial venous disease, who warrant
Figure 10 Complications. (a) Puncture of external iliac artery above the inguinal ligament during coronary angiogram resulting in retroperitoneal haemorrhage displacing right kidney. (b) Volume-rendered 3D CT showing CFA pseudoaneurysm.
Figure 11 Complications. (a) Angioplasty of occluded left common iliac artery. (b) Vessel rupture with contrast extravasation. (c) Successful treatment with covered stent graft.
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intervention, are now likely to be endoluminal procedures, not open surgery. This is of especial benefit when so many vascular patients are elderly, frail and have multiple co-morbidities. This change has resulted in less procedural morbidity and mortality, with consequent reduction in length of hospital stay. There is, however, increased need for post-procedure surveillance and re-intervention than following open surgery. The vascular specialist needs to be able to work with multi-planar reconstructed images, have mastered endoluminal techniques and be trained in vascular ultrasound (duplex). Interventions are increasingly complex and can only be safely delivered by skilled multidisciplinary teams including trained operators, imaging specialists, vascular scientists, radiographers and specialist nurses. The basic principles of safe access, safe navigation to the vessel of interest and safe closure of the access vessel, remain key to success. A
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Glossary of terms
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DSA
Arterial sheath Hydrophilic wire Inflation device Flush catheter
French (Fr) size Micro catheter Low-profile system
Subintimal approach
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Digital subtraction angiography; an initial image subtracted from an image acquired after contrast has been injected; thus leaving only arterial supply and removing bone, soft tissue etc. Sheath, with a haemostatic valve and side-branch to flush, placed to allow easy catheter and wire exchanges The name means ‘water loving’. Once wet, the coating is extremely slippery. (Terumo e Terumo, ZipWire e Boston Scientific) Means of inflating balloon to higher pressure than might be achieved by hand/syringe alone Catheter with side holes to allow the faster ejection of contrast for angiography. Two commonly used types are the coiled end ‘Pig tail’ and straight ‘Flush’ catheters External catheter circumference in mm. Commonly, 4 e7Fr Catheters in region of 0.021e0.02800 inch, passed through standard catheter to gain closer access to region of interest Balloon angioplasty performed via a 4F sheath and a small calibre 0.018 wire. The smaller sheath reduces post-procedure immobility and allows a greater proportion of day cases In long chronic occlusions, a hydrophilic wire can be passed between the intima and media creating a dissecting channel that is then angioplastied and/or stented to create a new flow channel
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REFERENCES 1 EVAR trial participants. Endovascular aneurysm repair versus open repair in patients with abdominal aortic aneurysm (EVAR
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trial 1): randomised controlled trial. Lancet 2005; 365: 2179e86. Fotiadis N, Kyriakides C, Bent C, et al. 64-section CT angiography in patients with critical limb ischaemia and severe claudication: comparison with digital subtractive angiography. Clin Radiol 2011; 66: 945e52. The Royal College of Radiologists Standards for patient consent particular to radiology. London: The Royal College of Radiologists, 2005. http://www.nrls.npsa.nhs.uk/resources/?entryid45¼73612. Accessed 12th February, 2015. Seto AH, Abu-Fadel MS, Sparling JM, et al. Real-time ultrasound guidance facilitates femoral arterial access and reduces vascular complications: FAUST (Femoral Arterial Access With Ultrasound Trial). JACC Cardiovasc Interv 2010; 3: 751e8. Spiliopoulos S, Katsanos K, Diamantopoulos A, et al. Does ultrasound guided lidocaine injection improve local anesthesia before femoral artery catheterization? Clin Radiol 2011; 66: 449e55. Bradbury AW, Adam DJ, Bell J, et al. Bypass versus Angioplasty in Severe Ischaemia of the Leg (BASIL) trial: an intention-to-treat analysis of amputation-free and overall survival in patients randomized to a bypass surgery-first or a balloon angioplasty-first revascularization strategy. J Vasc Surg, 2010; 5Se17. Bolia A, Miles KA, Brennan J, Bell PRF. Percutaneous transluminal angioplasty of occlusions of the SFA by subintimal dissection. Cardiovasc Interven Radiol 1990; 13: 357e63. Tepe G, Laird J, Schneider P, et al. Drug-coated balloon versus standard percutaneous transluminal angioplasty for the treatment of superficial femoral and/or popliteal peripheral artery disease: 12-month results from the IN.PACT SFA randomized trial. Circulation 2015; 131: 495e502. Kayssi A, Al-Atassi T, Oreopoulos G, Roche-Nagle G, Tan K, Rajan DK. Uncoated balloon angioplasty versus drug-eluting balloon angioplasty for peripheral arterial disease of the lower limbs. Cochrane Database Syst Rev, 2016; CD011319 https://doi. org/10.1002/14651858.CD011319.pub2. Vendantham S, Goldhaber SZ, Julian JA, et al. Pharmacomechanical catheter-directed thrombolysis for deep vein thrombosis. N Engl J Med 2017; 377: 2240e52. Laird John R, Katzen Barry T, Scheinert Dierk, et al. Nitinol stent implantation versus balloon angioplasty for lesions in the superficial femoral artery and proximal popliteal artery twelve-month results from the RESILIENT randomized trial. Circ e Cardiovasc Interventions 2010; 3: 267e76. Karnabatidis D, Spiliopoulos S, Tsetis D, et al. Quality improvement guidelines for percutaneous catheter-directed intra-arterial thrombolysis and mechanical thrombectomy for acute lower-limb ischemia. Cardiovasc Interven Radiol 2011; 34: 1123e36. White GH, Yu W, May J, et al. Endoleak as a complication of endoluminal grafting of abdominal aortic aneurysms: classification, incidence, diagnosis, and management. J Endovasc Surg 1997; 4: 152e68. Patel R, Sweeting M, Powell J, et al. Endovascular versus open repair of abdominal aortic aneurysm in 15-years’ follow-up of the
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Please cite this article in press as: Brooks M, Hardman J, Principles of endoluminal therapy, Surgery (2018), https://doi.org/10.1016/ j.mpsur.2018.03.006
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UK endovascular aneurysm repair trial 1 (EVAR trial 1): a randomised controlled trial. Lancet 2016; 388: 2366e74. 16 Fattori R, Russo V, Lovato L. Endovascular management of thoracic aortic aneurysms. Cardiovasc Interven Radiol 2011; 34: 1137e42. 17 Das R, Ahmed K, Athanasiou T, et al. Arterial closure devices versus manual compression for femoral haemostasis in interventional radiological procedures: a systematic review and meta-analysis. Cardiovasc Interven Radiol 2011; 34: 723e38. 18 The British Society of Interventional Radiology. Third BIAS report 2008. Oxfordshire: Dendrite Clinical Systems, 2008.
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Acknowledgement With acknowledgement to Katherine Augustine, Nathan Manghat and Hashem Baraket co-authors of a previous version of this article. KA and NM supplied most the illustrations. UK Endovascular Trainees (UKETS) are credited for the principles of safe access, navigation and closure.
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Ó 2018 Published by Elsevier Ltd.
Please cite this article in press as: Brooks M, Hardman J, Principles of endoluminal therapy, Surgery (2018), https://doi.org/10.1016/ j.mpsur.2018.03.006