Peripheral Vascular Stenting



Peripheral Vascular Stenting


Albert W. Chan

Stephen R. Ramee



Atherosclerosis is a systemic inflammatory disease that involves both the cardiac and the peripheral arterial circulations. The multisystem manifestation of atherosclerosis is highly prevalent in our society (1), and the number is increasing because of the aging population (Fig. 20.1). The risk factor management for coronary artery disease (CAD), such as smoking cessation, guided exercise, statin therapy, and blood pressure and diabetes control, is largely similar to those for peripheral arterial disease (PAD) and stroke. The majority of PAD patients may eventually die from cardiac causes. Furthermore, the presence of PAD is one of the most powerful predictors for mortality and morbidity in patients suffering from CAD (2). Therefore, management of PAD may enhance the rehabilitation and clinical outcomes of CAD. As such, the Prevention of Atherothrombotic Network has published a “call-for-action” statement to increase the awareness of PAD by increased screening and primary prevention (3). When encountered in CAD patients, cardiologists have a window of opportunity to provide screening and early detection of PAD. For example, the treatment of obstructive renal artery disease may improve blood pressure control and renal function, an important prognostic marker in CAD. Moreover, endovascular treatment for lifestyle-limiting claudication can improve the exercise tolerance and rehabilitation potential in cardiac patients.

Thus, it is logical and beneficial to the patient to have one physician (e.g., cardiovascular specialist) to provide panvascular disease management. More important, the techniques and the volume of cardiac interventional procedures used provide the interventional cardiologist with a solid foundation for performing percutaneous revascularization of peripheral arteries. Indeed, cardiologists already have played a major role in the introduction and refinement of new peripheral interventional procedures, such as carotid artery stenting, which is performed mostly by interventional cardiologists (4). It is imperative for the interventional cardiologist who wants to provide vascular medicine care to have a fund of knowledge on the natural history of PAD, treatment options, angiographic techniques and interpretation, patient and lesion selection for interventional procedures and, last but not least, device selection and usage.


REGIONAL CONSIDERATIONS


Carotid and Vertebral Arterial Disease


Carotid Artery

In the United States, about 750,000 strokes occur each year, and 88% of these are due to ischemia (5). Stroke is the third leading cause of death in Western society, and one-third of stroke patients remain institutionalized at 3 months after stroke. One-third of the cerebral ischemic events are associated with a significant obstructive disease in the extracranial carotid artery—a nidus for plaque formation and rupture that may cause recurrent symptoms of cerebroembolism.

Since the publication of the North American Symptomatic Carotid Endarterectomy Trial (NASCET) (6), European Carotid Surgery Trial (7), and the Endarterectomy for Asymptomatic Carotid Atherosclerosis Study (ACAS) (8), carotid artery endarterectomy (CEA) has been established as the gold standard for the revascularization of symptomatic and asymptomatic carotid artery disease. However, the patients enrolled in these clinical trials were highly selected, and the trial results did not reflect real-world practice (9,10). Many patients who require carotid revascularization are
considered high-risk for surgical revascularization and would have been excluded from the original trials. Indeed, by analyzing the Medicare data from the years when these trials were performed (1992-1993), those treated in the trial hospitals outside of the research protocol and those treated in non-trial hospitals had much higher mortality rates than those treated within the clinical trial protocol (9).






Figure 20.1. High prevalence of multisystemic atherosclerosis identified among 1,802 patients participating in an academic hospital-based geriatric practice. (Reprinted with permission from Ness J, Aronow WS. Prevalence of coexistence of coronary artery disease, ischemic stroke, and peripheral arterial disease in older persons, mean age 80 years, in an academic hospital-based geriatrics practice. J Am Geriatr Soc 1999;47:1255-1256.)

Percutaneous carotid artery revascularization provides a less invasive alternative to CEA. Endovascular treatment obviates the need for general anesthesia, eliminates the risk of cranial nerve injury or neck hematoma, and allows quicker recovery when compared with CEA. In the Carotid and Vertebral Artery Transluminal Angioplasty Study (CAVATAS) (11), the clinical outcomes of endovascular revascularization (76% angioplasty alone, 26% with adjunctive stent placement) were similar to those of CEA, whereas the incidences of cranial nerve injury (0% versus 9%) and hematoma requiring surgical exploration (1% versus 7%) were significantly higher in the surgical group. The Stenting and Angioplasty with Protection in Patients at High Risk for Endarterectomy (SAPPHIRE) study randomized patients with high surgical risk (Table 20.1) to undergo either CEA or carotid stenting using PRECISE (Cordis, Miami) with an adjunctive Angioguard (Cordis, Miami) emboli protection device (EPD) (12). In this study, carotid stenting was associated with a significantly less composite endpoint of death, nonfatal stroke, and myocardial infarction (MI) at 30 days (5.8% versus 12.6%, p = 0.047) and at 1 year (11.9% versus 19.9%, p = 0.048) when compared with CEA (12,13). The analysis of the SAPPHIRE stent registry, which included those patients turned down by surgeons, suggested that the 1-year outcomes of these patients treated with carotid stents were similar to those who were randomized in the study (7.8% at 30 days and 15.8% at 1 year). Subsequent to the SAPPHIRE study, a number of high-surgical risk registries have been established involving various combinations of self-expanding stents and EPDs, and they concluded similar outcomes as those reported in the SAPPHIRE study. While ongoing clinical trials comparing the two strategies are still taking place (e.g., CAVATAS II, CARESS, SPACE, etc.), carotid stenting with EPD should be adopted as the treatment of choice for carotid artery revascularization for symptomatic and asymptomatic surgical high-risk patients.

The Carotid Revascularization Endarterectomy versus Stenting Trial (CREST) is a randomized clinical trial funded by the National Institutes of Health and the National Institute of Neurological Disorders and Stroke. CREST is designed to compare carotid stenting with CEA among symptomatic surgical low-risk patients (14). The trial is currently in progress and is anticipated to be completed within the next 5 years at the time of this writing.


Importance of Emboli Protection Device

Distal embolization has been the Achilles’ heel of carotid stenting. The dislodgement of atherosclerotic debris during
plaque rupture by balloon, platelet activation, thrombus formation, and spasm of distal arterioles may lead to stroke during carotid intervention (15). Using transcranial Doppler technique during percutaneous carotid intervention, microembolism is detectable throughout the procedure, beginning from catheter placement, but balloon dilatation and stent deployment are responsible for most of the signals detected (16,17). Over the past several years, a number of EPDs have become available in clinical practice or within the context of clinical investigations (Fig. 20.2). Current EPDs can be classified according to three fundamental designs:








TABLE 20.1. HIGH-SURGICAL RISK CRITERIA FOR EXTRACRANIAL CAROTID ARTERY REVASCULARIZATION


















































Clinical


Elderly (e.g., >80 years)



Cardiovascular comorbidities



Unstable angina



Recent MI



Multivessel coronary artery disease with evidence of myocardial ischemia



Anticipated coronary artery bypass surgery or abdominal aortic aneurysm repair within the next 2 months



Moderate to severe left ventricular systolic dysfunction (e.g., LVEF <30%)



New York Heart Association class III-IV heart failure


Chronic obstructive pulmonary disease (forced vital capacity <30% of expected)


Dialysis-dependent


Anatomical


Bilateral carotid artery disease in which both require revascularization


Contralateral occlusive carotid artery disease


Lesion below clavicle or above C2


Post endarterectomy stenosis


Prior neck radiation or radical resection on the ipsilateral side


Tandem lesions


Spinal immobility due to cervical arthritis or other disorders


Presence of laryngeal palsy, laryngectomy, or tracheostomy







Figure 20.2. Examples of various filter emboli protection devices: (A) Angioguard, (B) EPI FilterWire, (C) Accunet.



  • Flow-through filter (Angioguard [Cordis, Warren, New Jersey], Accunet [Guidant, Santa Clara, California], FilterWire EX [Boston Scientific, Santa Clara, California], and NeuroShield [MedNova, Redwood City, California])


  • Balloon occlusion GuardWire (Medtronic, Minneapolis)


  • Flow reversal with proximal balloon occlusion (Parodi Anti-Embolism System [ArteriA Medical Science Inc., San Francisco])

The efficacies of using distal balloon occlusion and filters in preventing distal embolization have been proven in the percutaneous revascularization of saphenous vein grafts (18,19). Thus, by extrapolation of these data, it is assumed that EPDs enhance the safety of carotid stent procedures, and they have become a standard adjunctive device during carotid stenting in our clinical practice (Table 20.2).








TABLE 20.2. PROS AND CONS OF THE USE OF EMBOLI PROTECTION DEVICE DURING CAROTID INTERVENTIONS


















Pros


Cons


Safer procedure and prevents complications of emboli


Less flexible and higher profile than 0.014″ guidewires


Easy to use


Cumbersome to use for some designs and associated with a learning curve


High efficacy in capturing particles


May cause spasm or dissection



Adds cost, time, and complexity to procedure


By its design, each of the EPDs has logistical issues. The GuardWire is associated with prolonged cerebral ischemia during balloon occlusion, and the patient may not tolerate the procedure, especially in the presence of contralateral carotid occlusion. In addition, angiographic recording is not possible during intervention with this device. Furthermore, the “suction shadow,” occurring underneath the occlusive balloon and inaccessible to the aspiration catheter, may allow embolization of the trapped particles to the distal arterial bed upon balloon deflation. The pore size of current filters varies from 80 to 100 μm (Angioguard) to 120 μm (NeuroShield). The size of the atherosclerotic debris collected ranges from 120 to 3,000 μm (medium 580 μm) (20,21). Although particles <100 mm in size may pass through a filter, their clinical importance is unknown. When a filter is overwhelmed by large particles, flow in the carotid artery slows and filtration ceases. As with occlusion balloons, aspiration must be performed to remove the stagnant column of blood and debris before retrieving the filter.







Figure 20.3. Various types of aortic arches and their relationships with the great vessels leading to various levels of challenges for carotid stenting procedure. Selective carotid angiogram on (A) and (B) can be performed with a right Judkins or Bernstein catheter, whereas (C) usually requires reversed curve Newton, Vitek, or Simmons catheters.


Interventional Techniques

Diagnostic cerebral angiography includes aortic arch angiography and four-vessel selective angiography using digital subtraction technique. The aortic arch angiogram provides important information, including the location of the origins of the great vessels, unexpected anatomic variants, and previously unidentified proximal lesions in the great vessels (Fig. 20.3). A 4 Fr Bernstein catheter, a 5 Fr right Judkins, Vitek, or Simmons catheter (Cordis, Miami), together with a 190 cm 0.035-inch stiff-angled glidewire is recommended to perform selective angiography. Meticulous technique is needed during diagnostic cerebral angiography, because it is associated with a significant (up to 1%) stroke risk (22).






Figure 20.4. A 70-year-old woman suffered from right hemispheric stroke 1 month ago but had full neurological recovery. Magnetic resonance imaging showed a water-shed infarct zone in the corresponding hemisphere, suggestive of high risk for future event. (A) Angiogram confirmed the ultrasound diagnosis of a severe focal stenosis in the right internal carotid artery (arrow). (B) A FilterWire (arrow) was used to cross the lesion. (C) Balloon predilatation. (D) Angiogram after balloon dilatation. (E) Final angiogram after stent placement (Wallstent 7 × 30 mm, arrow).

To perform an interventional procedure in an extracranial carotid artery, the patient should be well hydrated and antihypertensive medications should be held on the day of the procedure (Fig. 20.4). Aspirin 81 to 325 mg and clopidogrel 300 mg should be given at least 24 hours before the procedure. A 6 Fr Shuttle sheath (Cook, Bloomington, Indiana) is typically exchanged for the diagnostic catheter over a 300 cm stiff Amplatz wire. Alternatively, a 5 Fr diagnostic catheter can be placed within a Shuttle sheath or an 8 Fr guide catheter (e.g., Headhunter-1) and, in a coaxial manner, this catheter acts as an introducer for the guide catheter to advance atraumatically over a glidewire into the arterial segment proximal to the target lesion. The diagnostic catheter and the glidewire then can be removed.
Anticoagulation using unfractionated heparin (activated clotting time 250 to 300 seconds) or bivalirudin is then provided. An EPD (e.g., FilterWire, Angioguard, GuardWire) then is advanced across the lesion and should be deployed within the straight segment of the precavernous portion of the distal extracranial internal carotid artery. Balloon predilatation can be performed using a 4.0 mm balloon catheter. If an EPD cannot cross a lesion initially, a 0.014-inch floppy guidewire can be used, and the lesion can be inflated with a small (2.0 mm) coronary balloon catheter before a repeat attempt to advance the EPD across the lesion. Atropine 0.5 to 1.0 mg is administered prophylactically to minimize the incidence of transient severe bradycardia during stretching of the carotid body if the resting heart rate is <60 beats/min. Using the guidance of bony landmarks or an angiographic roadmap, a self-expanding stent then is positioned and carefully deployed across the lesion. Postdilatation using a balloon catheter that matches the reference diameter of the internal carotid artery then is performed. For a carotid bifurcation lesion, the diameter of the self-expanding stent should match the diameter of the common carotid artery, and the length of the stent should be chosen to fully cover the lesion. The EPD then is retrieved, and angiography is performed for the target lesion as well as the intracerebral arteries supplied by the vessel in order to detect any distal embolization. When slow flow is noted on the angiogram before filter retrieval, this usually represents the filter being overwhelmed by the embolized material, or fibrin; a 125 cm-long diagnostic catheter or an aspiration catheter can be advanced over the EPD to aspirate the stagnant blood column before retrieving the filter. Access closure is usually recommended. The operator should then perform a brief neurologic examination before transferring the patient to the recovery area.


Postprocedure Care

Carotid body stimulation results in transient bradycardia and sustained hypotension. Aggressive hydration with normal saline should be provided; oral supplement (pseudoephedrine) or Neo-Synephrine can be provided to maintain the target blood pressure. Blood pressure is typically normalized within 12 to 24 hours, but occasionally it may take longer. Hyperperfusion syndrome occurs as a result of chronic maximal intracerebral vasodilatation and blunting of the autoregulatory response, and this occurs more frequently in the presence of a contralateral carotid artery occlusion. The patient may complain of headache in the presence of high systolic blood pressure (>140 mm Hg), in the absence of focal neurologic deficit. Therefore, intravenous nitroglycerin or nitroprusside should be titrated to maintain the blood pressure between 90 to 120 mm Hg. Within 24 hours of the procedure, independent neurologic assessment should be carried out by a stroke neurologist, and baseline carotid ultrasound and Doppler should be performed. Typically, a patient can be discharged within 24 hours postprocedure on lifelong aspirin and 30 days to 6 months of clopidogrel. Scheduled follow-up at 1, 6, and 12 months includes carotid ultrasound at 6- to12-month intervals.

Restenosis after carotid artery stenting has been reported in 2% to 3% of all patients in a large series (4). The treatment of carotid in-stent restenosis includes repeat balloon angioplasty (BA) or stenting, although their efficacies have not been studied. Brachytherapy recently has been reported as a safe and feasible therapeutic option, and its effectiveness require a more systematic assessment in larger series (23).


Vertebral Artery

The outcome data of endovascular interventions are limited by (a) the lack of awareness of posterior circulation ischemia during routine assessment in patients with stroke symptoms, (b) significant comorbidity and poor prognosis in this patient group, (c) a presumed lack of treatment options for these patients, and (d) publication of small case series, together with a lack of independent neurologic adjudication. Currently, the endovascular treatment of vertebral artery obstructive disease should include only patients with symptomatic vertebrobasilar insufficiency (e.g., dizziness, syncope, diplopia, tinnitus, headache, gait disturbances). Occasionally, even in the presence of bilateral vertebral artery stenosis, the correction of the obstructive carotid artery disease may improve both the anterior as well as the posterior circulation due to collaterals contributed by the Circle of Willis.

Vertebral artery interventions can be performed using coronary interventional devices (Fig. 20.5). A 6 Fr guide catheter (e.g., right Judkins, Envoy, or multipurpose) and a 0.014-inch steerable guidewire can be used. For an ostial or proximal vertebral artery lesion (V-1 segment), in general we adopt a routine stent strategy using a balloon-expandable stent in order to provide adequate radial force to achieve optimal angiographic result. For more distal or intracranial segments, angioplasty with a provisional stenting strategy should be used, because patients usually have dramatic symptom relief even following a reduction of the stenosis diameter to <50%; >95% of the patients were reported to be symptom-free at 1 year (24). Stent-related plaque shift causing occlusion of a side-branch in the vertebrobasilar artery could be fatal. When a stent is required, a balloon-expandable stent may offer the advantages of easier delivery and greater precision for stent placement, as compared to a self-expanding stent.


Intracranial Cerebral Intervention for Stroke Treatment and Prevention

Intracranial stenosis is not uncommon in patients with stroke or recurrent transient ischemic attacks (TIAs). BA is indicated in patients who have recurrent neurologic
symptoms despite appropriate medical therapy. The procedure is high-risk and technically challenging, and it requires a fund of knowledge of the intracranial arterial anatomy and physiology, and a high level of technical expertise. A multidisciplinary team consisting of a clinical neurologist, a neuroradiologist, and an interventionalist who is familiar with small vessel angioplasty and stenting is recommended to provide optimal care and clinical outcomes. To provide primary endovascular therapy for acute stroke, we adopt a model similar to acute MI treatment in the Ochsner Clinic, with both the on-call neurologist and interventionalist available round-the-clock to make appropriate patient selection and treatment.






Figure 20.5. (A) A 52-year-old man had symptom of vertebrobasilar insufficiency associated with a severe focal stenosis at the junction of the vertebral and basilar arteries (arrow). (B) The stenosis was relieved after revascularization with a balloon-expandable stent (arrow). (C) Two years later, he presented with intermittent headache, diplopia, and nausea. Selective angiography revealed occlusion in the V4 segment (arrow). (D) The occlusion was recanalized with a Choice PT extra-support guidewire, and satisfactory angiographic result was achieved after stent placement (Express 3.5 × 12 mm, 3.0 × 12 mm, and two 3.0 × 8 mm stents) (arrow).

Coronary interventional devices are suitable for intracranial endovascular therapy. Access is generally established via common femoral artery. A 6 Fr guide catheter (e.g., right Judkins or multipurpose for internal carotid artery; right Judkins or Envoy catheters for vertebral artery) is placed in the target vessel. A small coronary balloon catheter may be advanced over a 0.014-inch steerable, soft coronary guidewire. In general, short, low-pressure (4 to 6 atm) balloon inflations are employed to minimize cerebral ischemia and the risk of dissection. In contrast to coronary angioplasty, our experience suggests that residual stenosis in the absence of flow-limiting dissection may not necessarily be associated with adverse neurologic outcomes. Except for flow-limiting dissection, stents are typically avoided, because they may cause plaque shift and side-branch occlusion, which may be associated with catastrophic outcome.

In acute stroke management, BA can be performed to recanalize an occlusion within the internal carotid artery or cerebral arteries proximal to, or within, the secondorder branches (A2 or M2), but not distal to these branches. This usually is adequate to achieve a significant recovery of the neurologic deficit. An over-the-wire coronary balloon catheter is usually chosen to facilitate local drug delivery (e.g., tPA, urokinase), which may be required to achieve reperfusion in the third- or fourth-order cerebral arteries. Using this strategy, our center has reported a 100% procedural success with 1-year neurologic event-free survival at 93% among patients undergoing intracranial angioplasty with provisional stenting (25).


MESENTERIC ARTERIAL DISEASE


Renal Artery


Indications

Atherosclerosis and fibromuscular dysplasia are the most common etiologies of renal artery obstruction. Renal artery revascularization is indicated in patients with refractory hypertension (severe hypertension despite ≥3 antihypertensive medications, of which one is a diuretic), renal tissue salvage, or unstable cardiac syndrome in the absence of significant CAD. Stenting also should be considered for critical renal artery stenosis (RAS) (≥90%), because the risk of arterial closure is about 16% a year without revascularization, followed by loss of renal tissue (26). A resistive index (1-[diastolic velocity/systolic velocity]) of >0.80 obtained during Doppler ultrasonography has been proposed to detect distal renal arteriolar disease and thus act as a marker to predict poor response (27), although the utility has been refuted by other investigators (28).

Surgical bypass largely has become obsolete due to the high morbidity associated with the procedure and the availability of the less invasive endovascular technology. In a randomized controlled study, van de Ven et al. showed that balloon-expandable stenting is more likely to provide an angiographic success (88% versus 57%) and lower restenosis rate (14% versus 48%) than BA alone in renal artery revascularization (29). Fibromuscular dysplasia often responds to BA alone (30), and stenting is usually reserved for patients whose blood pressure does not respond to angioplasty.


Techniques

Femoral access is used most commonly, although brachial or radial arteries may be reserved if the renal artery has a steep caudal takeoff or if severe tortuosity of the aortoiliac artery is present. An appropriately shaped guide catheter (e.g., Renal double curve, Hockey Stick, IMA) can be used to
selectively engage the ostium of the target vessel. Guide catheter manipulation should be kept at a minimum because of the atheromatous disease burden in the aorta commonly found in patients with renal atherosclerosis. A 4 to 5 Fr diagnostic catheter (IMA, Bernstein, SOS, Simmons, or Cobra) may be useful to assist the selective engagement of the guide catheter. A soft-tipped 0.014-inch steerable coronary guidewire and an undersized balloon may be used for predilatation when stent placement is intended. A 1:1 balloon-to-artery ratio should be used to treat fibromuscular dysplasia. Patients should be monitored for the presence of back pain during balloon inflation, because it may signify overstretching of the adventitia and that the use of a larger balloon should be avoided.


Outcomes

Pooling the results of clinical reports that totalled >800 patients (31, 32, 33, 34, 35, 36, 37, 38, 39), blood pressure improvement is observed in 74% of the patients undergoing renal stenting for refractory hypertension, and 20% to 40% of patients with progressive renal insufficiency may achieve stabilization or improvement in renal function. Patients whose blood pressures does not improve following renal artery revascularization may have coexisting essential hypertension. Early reports suggest that baseline serum brain natriuretic peptide may be useful to predict blood pressure response in patients undergoing renal artery stenting (40).

Only gold members can continue reading. Log In or Register to continue

Stay updated, free articles. Join our Telegram channel

Sep 23, 2016 | Posted by in CARDIOLOGY | Comments Off on Peripheral Vascular Stenting

Full access? Get Clinical Tree

Get Clinical Tree app for offline access