Minimal Access Therapy for Vascular Disease

Minimal Access Therapy for Vascular Disease reviews the necessary training for surgeons and describes the legal aspects involved in endovascular techniques.
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• Peripheral Vascular Disease
• Minimal Access Therapy for Vascular Disease
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Endovascular techniques for treating patients with arterial and venous disorders have revolutionized modern medicine by significantly reducing procedure-related morbidity and hospital costs and delivering outcomes better than or, at least in part, equal to those of open surgical procedures. In the past few years, endovascular therapy has expanded from simple dilatation of atherosclerotic lesions to encompass treatment of aneurysmal arterial disease, acute ischemia, arteriovenous malformations, and venous disorders. Such significant advances in endovascular treatment have given physicians and their patients minimally invasive alternatives to major surgical procedures that carry significant morbidity and mortality.

This chapter reviews current advances and explores the benefits and limitations in minimally invasive therapies for the treatment of patients with occlusive and aneurysmal disease of the aorta and peripheral vessels. Endovascular treatment of peripheral vascular disease PVD with balloon catheters was first reported by Fogarty and coworkers 1 in Since then, dramatic advances in balloon and guidewire technology have made it possible to cross difficult lesions and chronic occlusions.

Better-designed stents have revolutionized endovascular interventions, providing an attractive and reliable alternative to vascular surgery to the point that endovascular stents are now the standard of care in peripheral vascular interventions.

Marked improvement in immediate- and long-term results with stent grafts now permit minimally invasive treatment of aneurysmal disease of the aorta as well as other major vascular territories. Improvements in pharmacologic agents and in catheter-based thrombectomy devices have made endovascular interventions the first-line therapy in patients who have acute limb ischemia ALI caused by thromboembolic disease.

Upper extremity ischemic disease is uncommon, and the majority of cases are secondary to vasospastic disorders, such as Raynaud syndrome and small vessel occlusive disease. In the vast majority of patients who present with chronic symptoms of proximal upper extremity ischemia, atherosclerosis is the underlying cause. Most of these patients are treated medically, with few being candidates for surgical or endovascular therapy.

Although occlusive disease of the subclavian artery is most often asymptomatic because of the rich supply of brachiocephalic collaterals, when it is symptomatic, patients may present with subclavian steal syndrome vertebrobasilar symptoms that worsen with exercise or work of the ipsilateral upper extremity ; ipsilateral upper extremity claudication; or in patients who have an internal mammary artery bypass graft, coronary-subclavian steal syndrome, in which flow to the graft left internal mammary artery becomes compromised, leading to angina or myocardial infarction MI. The first subclavian artery angioplasty was reported by Bachman and Kim in , 5 and although initial Use this site remotely Bookmark your favorite content Track your self-assessment progress and more!

Otherwise it is hidden from view. There is always the risk of progression of disease, but the important factor is symptomatology.

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A lesion should not be treated unless the interventionalist can prove it to be symptomatic. Lesions that are focal and shorter in length do well with angioplasty. There is a group of lesions, including long segments of disease or occlusions, for which angioplasty, although feasible, should not be the first line of therapy 7. Some of the contraindications to angioplasty are shown in Table 2. Most questions remain unanswered; however, certain trends do emerge from the confusion of data. First, PTA patency rates tend to be lower than but parallel to those for surgery 8 , 9.

Second, patency rates for both techniques fall off as the periphery of the vascular tree is approached Third, the same factors that affect PTA results impaired runoff, rest pain, distal gangrene, continued smoking, diabetes, female gender also affect the outcome of surgery. The immediate success and long-term benefits of PTA are significantly diminished by the problems of acute closure and postangioplasty stenosis most of the former and some of the latter are related to extensive, flow-limiting dissections.

The most important cause of restenosis is intimal hyperplasia and elastic recoil—though the process of restenosis and its relationship to the recurrence of symptoms are more complex and beyond the scope of this article.

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The choice of the type manufacturer of balloon to use for angioplasty is usually dictated by physician preference, familiarity with the product, and contract negotiations with the respective company. In general, an appropriately sized balloon diameter should be used for the selected vessel in order to minimize the risk of complications. PTA usage has been reported in many series from the carotid arteries to the tibial arteries with varying results and follow-up patency rates 10— The ultimate goal of PTA is an open vessel with a normal caliber.

The idea of a vascular scaffold that would oppose elastic recoil, provide internal support, and preserve luminal patency and dimensions was pioneered many years ago. The myriad of early prototypes has led to two types of stents characterized by their expansion mechanism: Significant advances have been made in the last few years, and several prototypes have reached clinical trials and FDA approval No ideal stent is yet available.

In assessing the various devices, the principles of deliverability, versatility, and biocompatibility are important considerations. Stents, available in a variety of lengths and diameters, are placed in vessels following angioplasty to help maintain vascular patency in an area of stenosis Figure 3. Increased neointimal formation, localized inflammation, and even erosion through the vascular wall can occur following placement, making future surgical treatment extremely challenging and potentially increasing its morbidity The balloon-expandable stents are some of the earlier designs and are typically preloaded on a balloon.

Its hoop strength and high expansion ratio make it a durable stent; however, the lack of longitudinal flexibility makes it susceptible to permanent deformation in a tortuous vessel and difficult to deliver over the aortic bifurcation for a contralateral lesion. Its knitted design provides high radiopacity, good flexibility, and minimal shortening. Additionally, the tantalum fiber does not interfere with magnetic resonance angiography techniques 11 , 15 , Self-expanding stents do not require a balloon and expand by resuming a preset configuration triggered by thermal memory at body temperature, or by a spring mechanism triggered when the device is unloaded from a constraining delivery catheter.

The Wallstent Figure 6 ; Schneider Stent, Plymouth, MN is made of 16—20 stainless steel monofilaments mounted on a delivery catheter with an outer covering sheath; the stent automatically deploys and expands into position once the sheath is withdrawn. It has good strength and flexibility but can shorten once deployed making precise positioning difficult.

Paul, MN uses the thermal shape memory of nitinol to reform its shape once it reaches body temperature. This stent, restrained on a delivery catheter, reportedly offers good flexibility and is easy to use. Another nitinol stent, the Memotherm Bard stent Bard, Covington, GA has a special diamond shape construction, but moderate hoop strength and little to no foreshortening upon deployment. Made of a single strand of nitinol configured to form a tubular implant of hexagonal cell patterns, this stent exhibits very little foreshortening upon deployment In some anatomical areas such as the aorto-iliac segment, stents have had their greatest impact on improving the immediate hemodynamic results of PTA and effectively managing recoil and dissection while also providing higher patency rates than PTA alone.

In addition, lesions that were untreatable by PTA alone, such as iliac occlusions, can now be treated in combination with stenting. The benefit of primary stenting in the leg below the iliac arteries has not been proven. Lesions that are troublesome for percutaneous intervention, such as eccentric plaques, long-segment occlusions, long-segment stenosis, obstructive intimal flaps after PTA, and stenosis at graft anastomosis, occur more frequently in the femoropopliteal distribution, and, not surprisingly, stents have been applied as a potential solution.

Although the immediate and early results have generally been good, and many angioplasty failures have been converted to successes with stents, long-term studies have shown less than promising results due to intimal hyperplasia and occlusion 15 , Therefore, at present it is wise to limit the application of these expensive devices to large or medium size arteries obstructed by post-PTA dissections or to elastic or eccentric lesions producing unsatisfactory results.

As public enthusiasm continues to increase with regards to minimally invasive vascular techniques, interest in percutaneously delivered stents with synthetic graft coverings has also increased. Stent-grafts are being investigated for the treatment of both aneurysmal and peripheral occlusive arterial disease.

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The idea behind stent-graft placement was to create an endovascular bypass that could more closely approximate patency after surgical bypass and at the same time would be superior to PTA for long lesions. Technical success has been better with larger vessels aortic, iliac than with smaller more distal vessels femoral, superficial femoral arteries 19 , The stent-grafts can be divided into three types based on their construction: Numerous types of aortic endograft systems are already under investigation for the treatment of infrarenal abdominal aortic aneurysms.

Two stent-grafts are currently approved by the FDA, each representative of a particular design philosophy. The prosthesis consists of self-expanding Z-stents covered with a tube graft of Dacron, a thin, woven polyester fabric. It is introduced into the aorta by unilateral femoral cutdown, with one limb the contralateral manipulated into position by guide wires using conventional interventional techniques.

Delivery of the components requires two small groin incisions to expose the femoral arteries We have used both of these devices at Ochsner.

Minimal Access Therapy for Vascular Disease

Some of the limitations are dictated by the infrarenal aortic neck from the renal arteries to the beginning of the aneurysm , which factors into landing the proximal portion of the graft. Overall, the modular endograft systems seem to provide more options to tailor the graft to each patient's anatomy and appear to be easier to use.

Experience with covered stents for the treatment of peripheral vascular disease or peripheral aneurysms is limited. For occlusive disease, it is postulated that an endoluminal stent-graft may limit the ingrowth of intimal hyperplasia along the length of the treated segment, thereby improving patency compared with other conventional treatments. For aneurysmal disease, the stent-graft may be used to bridge the aneurysmal segment and therefore occlude the aneurysm from the native circulation.

Other stent-grafts have been reported in the iliac and femoral systems with varied success 19 , The Passager Stent-Graft is a self-expanding nitinol device covered with Dacron that comes compressed on a loading cartridge. The Hemobahn graft has a self-expanding nitinol exoskeleton supporting an ultrathin-walled PTFE endoskeleton with good flexibility, kink resistance, and radial stiffness.

These devices are still early in their development and remain controversial compared with surgical techniques due to lack of long-term follow-up. Along with the advancement in medical technology has come improvement in gene therapy techniques applicable to all fields of medicine. The two major areas of research in gene therapy that will likely have the greatest impact on peripheral vascular disease are gene therapy affecting vascular restenosis and neointimal proliferation, and gene therapy impacting angiogenesis and neovascularization.



Research is being centered around affecting receptor expression such as the integrins ICAM-1 and VCAM-1 as well as growth factors, particularly platelet defined growth factor PDGF and fibroblast growth factor 2 FGF-2 to augment restenosis and intimal thickening 23 , Other researchers have been working on the amplification of the angiogenic response by affecting vascular endothelial growth factor VEGF and its receptors. Trials using plasmid-mediated delivery of VEGF are ongoing and may offer some hope for the future of patients with end stage inoperable peripheral vascular disease Endovascular techniques are being combined experimentally with brachytherapy.

Some clinical studies have suggested a substantial reduction in the restenosis rate with intraluminal irradiation of coronary and peripheral arteries applied in conjunction with angioplasty and stent placement 26 , After angioplasty and stent placement are completed, iridium loaded on a wire is placed over the region for a short period of time.

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Some clinicians feel this acts as prophylaxis against future restenosis for patients who are at high risk The technologic advances over the past decade have had a major impact on the treatment of vascular disease and created a new and exciting work environment for vascular surgeons. There are now many options to consider when treating the patient suffering from peripheral vascular disease, and the devices that are available to perform endovascular techniques continue to improve—though significant controversy exists and will continue as to the efficacy and validity of various treatment modalities.



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As the average age of the population continues to increase, so will the incidence of peripheral vascular disease. Although minimally invasive techniques have become an integral part of the treatment of these patients, it remains incumbent upon the treating physician to offer the best treatment to the patient. This will not necessarily be the least invasive.

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