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Developments in vascular and interventional radiology and innovative methods of treating vascular lesions are discussed
José Urbano MD PhD EBIR
Head of Vascular and Interventional Radiology,
Jiménez Díaz Foundation University Hospital,
Vascular radiologists are little-known specialists in the medical community It is a specialty that was born from diagnostic angiography in the 1950s, and which later evolved into many techniques and therapies that these specialists now apply. Therefore, today it is known as vascular and interventional radiology (VIR). This specialty has several peculiarities. First, VIR employs techniques and therapies that are guided exclusively by high quality images and requires a deep knowledge of radiological anatomy.
The vascular radiologist is a ‘surgeon’ working without looking at the patient or at their own hands; their eyes characteristically look at a television screen while they work. Second, interventional treatments are performed by percutaneous puncture or through a natural orifice without requiring surgical dissection, and so VIR also is known as minimally invasive surgery. The immediate consequence of this has been a lower morbidity and mortality, faster patient recovery and a decrease in overall healthcare costs. Third, vascular radiologists are typically dynamic specialists, constantly evolving to adapt to the technological innovations. They have been great innovators in developing numerous techniques, some of which have revolutionised medicine.
Some of the procedures that today seem routine, but were once considered medical breakthroughs, were invented or described by VIR. Something as routine as the Seldinger technique was first described in 1953 by RVI.1 This technique is a medical procedure to obtain safe access to blood vessels and other hollow organs. It is used for venous or arterial catheterisation, insertion of chest or abdominal drains, nephrostomies and central venous catheters, insertion of PEG tubes, pacemaker or implantable cardioverter-defibrillator and numerous other interventional medical procedures. Many different medical specialists use it regularly without knowing its origin.
On January 1964, at Oregon Health and Science University, Dr Dotter, a well know vascular radiologist, performed the first transluminal percutaneous angioplasty (PTA). He dilated a tight, localised stenosis of the superficial femoral artery in an 82-year-old woman with painful leg ischaemia and gangrene who refused leg amputation.2 In 1975 Gianturco and Amplaz, two of the most productive interventionists in history, described two new materials which went on to be the origin and further development of current techniques of embolisation.3,4 In the early 1980s, Japanese doctors described the first cases of transarterial chemoembolisation of hepatocelular carcinomas (TACE) and thus was born one of the most innovative branches of vascular radiology: interventional oncology.5
In the 1990s, vascular radiology was a pioneer in the endovascular treatment of both abdominal and thoracic aortic aneurysms. In 1991, Parodi and Palmaz report the first abdominal aortic aneurysms successfully treated without major cut down by transfemoral intraluminal graft implantation.6 Michael Dake did the same three years later with thoracic aortic aneurysms.7 As had happened before with many other interventional treatments, the aortic stent-grafting, initially considered an experimental or compassionate treatment, became the first indication ahead of traditional surgery.8 Once an interventional treatment achieves success, demonstrates effectiveness and is established as standard practice, other specialties gradually claim the treatment as their own. Eventually the treatment initially developed and carried out by VIR is used by other specialties.
Coronary angioplasty, nephrostomy, bile and digestive stents are examples of this. This is because VIR is usually integrated within the radiology services and the vascular radiologist does not have direct responsibility for the indication and monitoring of the patients that are treated.
Both European and American Societies of vascular and interventional radiology (CIRSE and SIR) are aware of this problem, so in recent years they have tried to redefine VIR being perceived as a specialty clinic, ward or therapies and giving up the old idea of VIR as doctors that only perform procedures that others tell them to do. If VIR is to survive as a specialty in the future, it must take responsibility for the patient both before and after the technique or intervention. Thus, in the US and Canada, VIR has already been defined as an independent specialty of radiology.
However, this is not so easy in all countries because there are many outside interests, often within its own radiology services, that hinder this development. CIRSE is a powerful Society that gathers together all European interventionists; thus CIRSE is trying to define and unify the specialty throughout Europe. To begin with, it has created the EBIR, an independent and comprehensive examination that certifies European vascular radiologists under a unified and homogeneous clinical and therapeutic knowledge.
Regardless of the changes and threats to this specialty, vascular radiology is now taking advantage of technological innovations that companies and engineers offer and certainly will still be offering in the future. As mentioned above, in the last decades of the 20th century, treatments and interventional techniques developed gradually. The difference today is that the technological revolution and globalisation of information has led to an explosion of new products and tools. Not a year goes by without new and interesting devices that allow the improvement of the results of previous treatments, or which allow the number of patients eligible for such treatment to increase. This requires us to be alert to new and constant innovations: CIRSE and LINC meetings have become benchmarks for the launch of these new products.
In aortic pathology, major current developments are low profile stent-grafts that can be placed 100% percutaneously, as in the case of TriVascular’s Ovation Prime® or Cordis’s Incraft®. The low profile allows placement in patients with narrow or tortuous iliac arteries where previously the only option was open surgery. The aortic neck abdominal aortic aneurysm (AAA) remains the Achilles heel for endovascular aortic repair (EVAR).
Another recent development is the design of dedicated stent-grafts with a specific design to fix into severe angulated and hostile aneurysm necks, such as Lombard’s Aorfix® or Vascutek’s Anaconda® stent-grafts. Regarding short or taper necks, which is another big problem of EVAR, compared to standard fixation systems based on self-expanding stents with more or less radial force, Ovation Prime® has an anchoring system which uses an O-ring for seal that performs the combined function of fixation and sealing in the aortic neck while protecting the arterial wall against the constant radial force that other endo-grafts cause along the aneurysm neck. A novelty in the field of EVAR is Endologix’s Nellix® stent-graft that completely changes previous philosophy and incorporates the idea of a polymer filling the aneurysm sac excluding and sealing it.
Tailor-made, branched and fenestrated aortic stent-grafts used in thoracoabdominal aneurysms were until now the monopoly of Cook, but Vascutek and Jote have launched two new devices with promising results and providing certain advantages over the Cook system.
In peripheral arterial vascular disease, there are many novelties. The recent CORAL study9 confirms that stenting of atheromatous renal artery stenosis should be indicated more restrictively than previously. It is expected that the volume of these interventions to decrease in the coming years. However, in the superficial femoral artery (SFA) and below the knee, as has happened in aortic aneurysms, endovascular treatment has been imposed over surgical bypass.
In the SFA there is growing evidence that nitinol self-expanding standard stents are useful for the treatment of short and intermediate occlusions but do not work properly in long recanalisations. ABBOTT Vascular has launched a novel interwoven-wire, self-expanding nitinol stent. The Supera® stent has different design and technology from what was available up until now. It has the advantage of adapting to all the forces experienced by the SFA and yet is so flexible that it can be placed in the popliteal artery. It was discouraged for the use of standard stents (Figure 1).
The SFA dedicated drug-eluting stent, Cook’s Zilver®, continues to demonstrate good permeability results (now with five years follow-up) when compared with the permeability of the bare nitinol stents. Long-term results will have the same problems of clogging and breakage than bare stents. Drug-coated balloons are another innovation in the treatment of SFA occlusive disease. They have already proved to be useful to improve the permeability of the SFA versus PTA with plain balloons.10 They provide a great advantage over stents as they can recanalise the SFA without leaving any metal device under the arterial wall.
Embolisation is another field with big innovations for the treatment vascular diseases. When we talk about embolisation we talk of closing blood vessels, which is the opposite of what we do when performing PTA and stenting. Embolisation of postpartum haemorrhages, pelvic traumas, fibroids or visceral aneurysms is a treatment that is already established with enough evidence that the embolisation has replaced surgery. Benign prostatic adenoma embolisation or lower gastrointestinal bleeding is a less invasive emerging treatment.11,12
Onyx®, from Covidien, is a release-controlled, biocompatible liquid embolic agent for vascualr occlusions, the mechanism of action of which does not depend on the patient’s coagulation status. It was used only in neuroradiology but recently the strengths of this product are being applied to large numbers of peripheral arterial vascular treatments. Endoleak and arteriovenous malformations are its best-known indications but it has great potential in many others.
In venous vascular disease, developments include pharmacomechanical thrombolysis devices, of which both Covidien’s Trellis® peripheral infusion system (Figure 2) and BTG’s EKOS® Endowave Infusion Catheter System have shown promising results.13 Post-thrombotic syndrome is a common sequela of proximal deep vein thrombosis (DVT). With these two systems we can remove venous fresh thrombi safely and effectively without subjecting the patient to high doses fibrinolytics. Some ongoing research studies, such as the ATTRACT trial sponsored by the NIH, will soon provide information about the benefits of early recanalisation of the iliac veins with acute DVT using pharmacomechanical thrombolysis.
Interventional oncology is also a field in constant development. Transcatheter intra-arterial infusion of drugs and tumouricidal isotopes are standard treatments for hepatocellular carcinoma. However, the future aim is much more ambitious in trying to target any tumour tissues through microcatheters. The widespread use of preloaded drug-eluting beads with specific drugs for each tumour, which are deposited selectively through a microcatheter within a tumour, will allow larger doses to be given without systemic effects. Currently it is only possible to load the drug-eluting beads with doxorubicin or irinotecan, but there is ongoing research to obtain microspheres that act as carriers of any antitumoural agent.
Radiopaque and biodegradable microspheres will soon be available.
Finally, we should not forget that in addition to the new devices and treatments, there has also been a great technological improvement with angiographic equipment. Navigation systems, image fusion, integrated CT angiography, greatly facilitate the use of these endovascular treatments and thereby reduce operator dependence and the dose of radiation received by patients and physicians.