- Email: [email protected]
Technical Tips for Carotid Angioplasty and Stenting
Technical Tips for Carotid Angioplasty and Stenting W. Todd Bohannon, MD Angioplasty and stenting of the carotid artery has become an accepted procedure in properly selected patients with carotid artery stenosis. The potential for devastating neurologic complications and significant hemodynamic changes separates endovascular treatment of the carotid artery from other percutaneous peripheral vascular procedures. In this article, the technique for carotid artery angioplasty and stenting is described and the strategies for management of the hemodynamic changes occuring with carotid stenting are reviewed. Semin Vasc Surg 21:3-7 © 2008 Elsevier Inc. All rights reserved.
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HE BASIC PRINCIPLES of angioplasty and stenting apply to the percutaneous treatment of cervical carotid occlusive lesion. However, the potential for devastating neurologic complications and significant hemodynamic changes separates endovascular treatment of the carotid artery from other vascular beds commonly treated by peripheral vascular specialists.1-7 Carotid angioplasty and stenting (CAS) requires careful patient selection, counseling, and procedural planning. This article will discuss the important technical points of carotid stenting and the perioperative management of patients undergoing carotid stent placement, including strategies for anticoagulation and treatment of procedural hemodynamic changes (Table 1).
Before the Procedure A preoperative imaging study is preferable for the assessment and planning for carotid stent placement.8 An arch aortogram and selective carotid arteriogram or a good quality magnetic resonance angiography with arch, cervical, and intracranial images may be used for evaluation of a patient’s arch and carotid anatomy and CAS planning. This allows for proper selection of access catheters, sheaths, cerebral protection devices, and stents. A thorough and documented neurological exam is essential, especially if a neurologic event occurs in the perioperative period.
Division of Vascular Surgery, Scott & White Hospital and Clinic, Texas A&M University Health Science Center, Temple, TX. Address reprint requests to W. Todd Bohannon, Division of Vascular Surgery, Scott & White Hospital and Clinic, 2401 South 31st Street, Temple, TX 76502. E-mail: [email protected]
0895-7967/08/$-see front matter © 2008 Elsevier Inc. All rights reserved. doi:10.1053/j.semvascsurg.2007.11.003
Antiplatelet Agents Antiplatelet therapy is an essential component of the carotid stenting procedure. Clopidogrel (Plavix), 75 mg daily, is given for 5 days before the stenting procedure and then continued for at least 1 month after carotid stent placement.9 If patients were not treated with clopidogrel for several days prior to the procedure, 300 mg can be given in a single dose before the procedure. Ticlopidine (Ticlid) is an alternative for those who are unable to take clopidogrel.
Periprocedure Anticoagulation Heparin is administered prior to catheterizing the common carotid artery, usually after access is obtained. The usual dose is 100 U/kg. The activated coagulation time (ACT) is used to guide heparin administration with a goal ACT of 250 to 300 seconds achieved prior to intervention. The dosage of heparin should be reduced when glycoprotein IIb/IIIa receptor inhibitors are used. Heparin doses are repeated through the procedure as necessary, however, the procedure is usually completed before the anticoagulant effect of the heparin dose has diminished. Heparin is usually not continued after the procedure. Bivalirudin (Angiomax) is a direct thrombin inhibitor that is preferred by some because of the short half-life of 25 minutes. It is a good alternative in patients that cannot tolerate heparin. Bivalirudin is monitored with the ACT. A bolus of 1 mg/kg is given intravenously followed by an infusion of 0.2 mg/kg per hour. The effects of bivalirudin are prolonged with renal failure. The dosage should be adjusted in dialysis patients and those with moderate to severe renal insufficiency.9 The binding of fibrinogen to the platelet glycoprotein integrin IIb/IIIa mediates platelet aggregation, and inhibitors of the platelet glycoprotein IIb/IIIa receptor have been success3
W.T. Bohannon
4 Table 1 Steps Involved in the Carotid Angioplasty and Stent Procedure Retrograde CFA puncture with placement of 6Fr or 7Fr sheath Anticoagulation Intravenous heparin Target ACT >250 seconds Consider IIB/IIIA inhibitor in high embolic risk patients Cannulate aortic arch branch vessels Guide wire and angled glide catheter placed in external carotid artery Exchange length Amplatz guide wire placed in external carotid artery Guide sheath in common carotid artery Carotid angiogram through guide sheath to delineate stenosis Crossing of target lesion with guide wire or CPD Predilation PTA with 4-mm balloon Consider Atropine 0.5 to 1.0 mg IV before PTA Carotid angiogram to access PTA results Stent placement Postⴚstent dilatation as indicated CPD removal Completion angiograms Abbreviations: ACT, activated clotting time; CFA, common femoral artery; CPD, cerebral protection device; Fr, French; IV, intravenous; PTA, percutaneous transluminal angioplasty.
ful in reducing ischemic complications in coronary artery angioplasty and stenting.9-13 In the past, some have recommended routine use of glycoprotein IIb/IIIa inhibitors to reduce ischemic complications associated with carotid angioplasty and stenting.14,15 Other reports have found either no benefit or higher complication rates associated with IIb/IIIa use.16-19 Therefore, routine use of glycoprotein IIb/IIIa inhibitors in carotid stenting is not necessary due to the increased risk of cerebral hemorrhage or access-site complications. However, IIb/IIIa inhibitors may be a useful adjunct in selected patients. Perioperative intravenous administration of glycoprotein IIb/IIIa inhibitors should be considered in patients who did not have an appropriate preoperative loading of clopidogrel, patients with severe intracranial occlusive disease, and patients with highly ulcerated carotid bifurcation lesions. If a IIb/IIIa inhibitor is used, the dose of heparin should be decreased. Intraoperative glycoprotein IIb/IIIa inhibitors have also been administered intraarterially in situations where thrombus formation has developed within the stent or the patient has a distal embolus.20,21
Carotid Stent Procedure Patient Preparation/Positioning Diagnostic and therapeutic cerebral vascular procedures are done in the angiography suite. Generally, a formal diagnostic carotid and cerebral angiogram has been previously performed. Satisfactory baseline images in multiple plains of the extracranial and intracranial cerebral circulation are impor-
tant prior to intervention. The intracerebral images are necessary as a reference for comparison to the cerebral runoff after CAS. Following successful femoral sheath insertion, the patient is systemically anticoagulated with intravenous heparin as described here previously. A neurologic assessment should be performed after sheath access and throughout the procedure. A noise-making device, such as a horn, is placed in the contralateral hand. It is squeezed throughout the procedure to assess the patient’s motor function and ability to follow verbal instructions. Also, the patient’s speech and cognitive abilities are followed throughout the procedure with a standard series of questions.8
Sheath Access of the Common Carotid Artery The image intensifier is positioned so the aortic arch can be viewed in an oblique projection at approximately 25 to 30 degrees. If the proximal branch artery anatomy is relatively straightforward on the prior angiogram, a new arch aortogram is not necessary. Angiography is performed with isoosmolar contrast. An angled glide catheter (4Fr or 5Fr) is the initial catheter of choice and can be used in conjunction with a 0.035-inch Glidewire to cannulate the innominate artery and right common carotid arteries, as well as the left common carotid artery. If an angle glide catheter is not successful, other catheters with different shaped tips, such as a Simmons catheter can be used. The position of the Glidewire must be monitored closely, and the carotid lesion should not be inadvertently crossed. The angled glide catheter is positioned in the proximal common carotid artery and the initial carotid and intracranial angiograms are obtained in both AP and lateral projections. Next, the image intensifier of the C-arm is positioned so that the carotid bifurcation can best be demonstrated with maximal separation of the internal and external carotid arteries. The glide catheter, over the angled Glidewire, is positioned as far into the external carotid artery as possible. This Glidewire is then exchanged for a stiff wire, such as an Amplatz exchange length guide wire. Over the Amplatz wire, a 90-cm, 6Fr or 7Fr shuttle sheath is positioned in the common carotid artery. The tip of the shuttle sheath should be securely placed within the common carotid artery without advancing the leading introducer tip of the sheath too far into the carotid bifurcation. The introducer tips in many sheaths are not well-visualized, and emboli could occur from the introducer as it encounters an unstable plaque near the bifurcation. Open cervical access to the common carotid artery is a good option for some patients with difficult anatomy or situations where sheath traversal in the arch is not advisable, such as mobile athroma.22
Cerebral Protection Device Placement Once the sheath is securely positioned in the common carotid artery, the optimal angle of the image intensifier is established to best visualize the carotid bifurcation and the entire internal carotid artery. The internal carotid artery anatomy must be appropriate for the cerebral protection device (CPD). There must be adequate length for placement with
Technical tips for carotid angioplasty and stenting minimal tortuosity and sufficient distance away from the carotid lesion. The commercially available carotid stent systems have various types of microporous filters accompanied with a small caliber guide wire. Please review the anatomic criteria and the particular device specifications for the planned CPD prior to the CAS procedure. The preprocedure imaging should help in device planning. Generally, the CPD is advanced across the internal carotid stenosis with the soft and floppy tip of the wire placed within the distal internal carotid artery. Once the CPD is deployed, care must be taken to avoid movement and repositioning of the CPD, as this could cause spasm or injury to the carotid artery. For difficult lesions, the tip of the wire may need to be shaped to allow some directionality with manipulating the wire. If a catheter is needed, an angled 4Fr 120-cm glide catheter is used, rather than the standard 100-cm catheter, because once the guiding sheath is placed, the added length of the glide catheter is necessary for any additional catheter manipulations or wire exchanges. Angiography is performed to verify proper positioning of the CPD and imaging of the carotid lesion before proceeding to angioplasty.
Carotid Angioplasty and Stent Placement Because it is not uncommon for patients to have bradycardia and hypotension with carotid angioplasty, hemodynamic assessments are made continuously throughout the procedure. In order to limit the bradycardia associated with angioplasty of native arterial lesions, the patient is given 0.5 to 1 mg of intravenous atropine. Percutaneous transluminal angioplasty of the carotid stenosis is carefully performed with a 3-mm or 4-mm angioplasty balloon. Monorail or “rapid exchange”⫺type balloon catheters are preferred to the more cumbersome coaxial over-the-wire balloons. Results of the percutaneous transluminal angioplasty are assessed with an angiogram performed through the guide sheath. A saved image of the expanded balloon is useful for device selection. Size and length of the balloon is compared to the native artery and the carotid lesion and used to select an appropriate stent and postdilation balloon. Both the internal carotid artery and the common carotid artery diameters are important considerations when selecting the stent. A self-expanding stent is used following angioplasty of the carotid stenosis. With regard to cell design, open versus closed, most carotid lesions can be treated with either type. However, some lesions may be better suited for treatment with a specific cell design. Because the open cell design is more conformable, this type of stent is often used when tortuous anatomy is encountered. The closed cell design can provide more radial force and may have less plaque protrusion. Thus, a closed cell design is used in carotid stenoses that have a higher embolic potential or significant calcification. Once the stent is deployed, an angiogram is performed to access the stent placement. Following deployment, one must decide whether to postdilate the stent. Generally, we postdilate with an approximately 5-mm balloon with expedient balloon inflation to profile and rapid deflation. It is wise to accept a mild residual carotid artery
5 stenosis and avoid potential complications of emboli or rupture with repeated angioplasty or overdilitation.
Removal of CPD and Completion Images An angiogram is performed following stent deployment and before CPD removal to verify patency of the ICA and flow through the CPD. If there is no flow in the ICA, one must consider a large burden of thrombus or atherosclerotic debris within the filter. Various techniques can be employed to clear the filter, such as aspirating with another catheter positioned in the filter. Associated vasospasm can be treated with nitroglycerine. The CPD is removed per the device-specific instructions, and completion angiogram images obtained. This should include an AP and lateral view of the cervical region. Formal completion intracranial images may be considered. If there is a neurologic deficit on examination, AP and lateral views of the intracranial anatomy should be obtained and compared to the preprocedure images. However, if the patient is neurologically intact and unchanged from baseline, one may consider not performing completion intracranial images and limiting further flushes of contrast into the carotid and ipsilateral brain. If there are no neurologic or technical issues, the catheters and guide wires are then removed. The sheath is then exchanged for a standard 6Fr or 7Fr short sheath, and then this sheath is removed with the assistance of a closure device or once the ACT is ⬍150 seconds.
Treatment of Hemodynamic Changes Abrupt hemodynamic changes are common with the CAS procedure.23 Thus, an awareness of the potential for serious fluctuations in blood pressure and heart rate is important, as these patients often have underlying cardiovascular disease and a poor tolerance for hemodynamic instability. We, therefore, use an arterial line for all cases and have anesthesiology support to assist in the monitoring of our CAS patients.
Bradycardia Bradycardia, due to stimulation of the carotid bulb, is the most common and sudden hemodynamic change seen with the CAS procedure. Hypotension may occur as a result of the bradycardia. A less-common finding, due to stimulation of the carotid bifurcation and a resultant long sinus pause, is asystole. Pacemaker capability should be immediately available, either transvenous or external, but pacemaker insertion is rarely needed if the bradycardia is promptly treated pharmacologically. In patients with atherosclerotic carotid stenosis without a history of prior carotid surgery, atropine is administered (0.5 to 1 mg) prior to balloon dilatation to prevent or reduce severity of the bradycardia. This avoids significant tachycardia, which may have its own potential for complications. The atropine is given approximately 1 minute before balloon inflation. Patients with a baseline bradycardia usually receive the larger initial dose of atropine (1 mg). It is uncommon for patients who have had prior carotid surgery
W.T. Bohannon
6 to have a significant bradycardic response; therefore, they do not usually receive atropine before balloon dilation.
Hypotension Hypotension is commonly associated with the bradycardia, and usually responds to atropine and the resultant increase in heart rate. Occasionally, the hypotensive response to carotid angioplasty and stenting can be severe and more than can be attributed to bradycardia alone. In this instance, a fluid bolus and vasopressors should be considered. Neosynephrine is often used to maintain a systolic pressure of 100 mm Hg or higher. A symptomatic patient with poor cerebral or myocardial perfusion may require a higher target blood pressure. The vasopressor is usually only needed for a few hours, and rarely required longer than 24 hours. Some of the patient’s antihypertensive medications may need to be held or the dosage reduced in the periprocedure period.
Hypertension If hypertension occurs early in the procedure, it is not aggressively treated, as hypotension and bradycardia will often follow after angioplasty and stenting. Hypertension usually improves with mild sedation. If hypertension needs to be addressed, short-acting vasodilators are preferable to -blockers. Patients with severely elevated baseline blood pressure prior to the procedure are at higher risk for a perioperative neurological event. Sustained hypertension is uncommon. If this occurs, it should be aggressively treated to decrease the potential for intracranial hemorrhage in the postoperative period. A systolic blood pressure ⬍150 mm Hg is desirable.
After the Procedure The patient is monitored after the procedure, usually until the following day, for hemodynamic and neurologic changes. A long hospital stay is uncommon due to hypotension and vasopressor requirement. Frequently, the preoperative antihypertensive medications must be decreased before discharge and the blood pressure closely monitored at home. Clopidogrel (75 mg/ day) is continued for 4 to 6 weeks after CAS. Carotid duplex ultrasonography is usually performed within 1 month of the CAS procedure, then at 6 months and 1 year.
Carotid Stenting: Important Technical Points Perform an arteriogram, or other imaging study, with good quality cerebral runoff images prior to carotid stent placement. Always obtain a thorough baseline neurologic exam. Both are important for comparison following angioplasty and stenting if any neurologic changes occur. Clopidogrel should be taken before the procedure for 5 days if possible and it should be given for at least 4 weeks following stent placement. Aspirin should be taken for life. A high-dose load should be considered in patients before CAS who have not been taking clopidogrel. IIb/IIIa inhibitors
should be used in those patients who cannot or have not taken clopidogrel. Heparin should be administered to achieve an ACT of ⬎250 seconds. Bivalirudin (Angiomax) may be used as an alternative. Place an Amplatz or similar stiff guide wire as far as possible in the external carotid artery, but be careful with the position of the guide-wire tip during advancement of the sheath to avoid inadvertent arterial perforation. To help prevent severe bradycardia, atropine should be given prior to angioplasty of carotid stenoses. However, atropine is usually not necessary in patients with history of prior surgery in the region of the carotid bifurcation. In order to limit plaque disruption and emboli, predilate with a smaller-sized balloon. The saved image of the contrastfilled balloon is used to estimate the size of the internal and common carotid arteries. A mild residual stenosis is acceptable. If postdilation is required, avoid repeated angioplasty and overdilation to reduce the risk of emboli and carotid artery rupture. If hypertension occurs during the procedure and requires treatment, short-acting vasodilators are preferred rather than -blockers. With hypotensive patients, treat the bradycardia first. If a vasopressor is needed, consider Neosynephrine and keep the systolic blood pressure ⬎100 mm Hg.
Conclusion Carotid stenting is separated from interventions in other vascular beds by the potential for stroke and significant hemodynamic changes. Hopefully, with a good understanding of the procedure and the management options for perioperative anticoagulation and hemodynamic changes, carotid stenting can be performed safely with minimal complications.
References 1. Criado FJ, Lingelbach JM, Ledesma DF, Lucas PR: Carotid artery stenting in a vascular surgery practice. J Vasc Surg 35:430-434, 2002 2. Diethrich EB, Ndiaye M, Reid DB: Stenting in the carotid artery: initial experience in 110 patients. J Endovasc Surg 3:42-62, 1996 3. Mathur A, Roubin GS, Iyer SS, et al: Predictors of stroke complicating carotid artery stenting. Circulation 97:1239-1245, 1998 4. Qureshi AI, Luft AR, Janardhan V, et al: Identification of patients at risk for periprocedural neurological deficits associated with carotid angioplasty and stenting. Stroke 31:376-382, 2000 5. Roubin GS, New G, Iyer SS, et al: Immediate and late clinical outcomes of carotid artery stenting in patients with symptomatic and asymptomatic carotid artery stenosis: a 5-year prospective analysis. Circulation 103:532-537, 2001 6. Shawl F, Kadro W, Domanski MJ, et al: Safety and efficacy of elective carotid artery stenting in high-risk patients. J Am Coll Cardiol 35:17211728, 2000 7. Morrish W, Grahovac S, Douen A, et al: Intracranial hemorrhage after stenting and angioplasty of extracranial carotid stenosis. Am J Neuroradiol 21:1911-1916, 2000 8. Bohannon WT, Silva MB: Technique of carotid bifurcation angioplasty and stent placement: how we do it, in Schneider PA, Bohannon WT, Silva MB (eds): Carotid Interventions. New York, NY, Marcel Dekker, 2004, pp 131-139
Technical tips for carotid angioplasty and stenting 9. Bohannon WT, Schneider PA: Periprocedural management of patients undergoing carotid intervention, in Schneider PA, Bohannon WT, Silva MB (eds): Carotid Interventions. New York, NY, Marcel Dekker, 2004, pp 119-129 10. Platelet glycoprotein IIb/IIIa receptor blockade and low-dose heparin during percutaneous coronary revascularization: The EPILOG Investigators. N Engl J Med 336:1689-1696, 1997 11. Randomized placebo-controlled trial of abciximab before and during coronary intervention in refractory unstable angina: the CAPTURE Study: Lancet 349:1429-1435, 1997 12. Randomized placebo-controlled and balloon-angioplasty-controlled trial to assess safety of coronary stenting with use of platelet glycoprotein-IIb/IIIa blockade: the EPISTENT Investigators. Evaluation of Platelet IIb/IIIa Inhibitor for Stenting. Lancet 352:87-92, 1998 13. O’Shea JC, Tcheng JE: Eptifibatide in percutaneous coronary intervention: the ESPRIT Trial results: Curr Interv Cardiol Rep 3:62-68, 2001 14. Kapadia SR, Bajzer CT, Ziada KM, et al: Initial experience of platelet glycoprotein IIb/IIIa inhibition with abciximab during carotid stenting: a safe and effective adjunctive therapy. Stroke 32:2328-2332, 2001 15. Qureshi AI, Ali Z, Suri MF, et al: Open-label phase I clinical study to assess the safety of intravenous eptifibatide in patients undergoing internal carotid artery angioplasty and stent placement. Neurosurgery 48:998-1004, 2001
7 16. Schneiderman J, Morag B, Gerniak A, et al: Abciximab in carotid stenting for postsurgical carotid restenosis: intermediate results. J Endovasc Ther 7:263-272, 2000 17. Hofmann R, Kerschner K, Steinwender C, et al: Bolus injection does not reduce cerebral ischemic complications of elective carotid artery stenting: a randomized study. Stroke 33:725-727, 2002 18. Qureshi AI, Suri MF, Ali Z, et al: Carotid angioplasty and stent placement: a prospective analysis of perioperative complications and impact of intravenously administered abciximab. Neurosurgery 50:466-473, 2002 19. Wholey MH, Wholey MH, Eles G, et al: Evaluation of glycoprotein IIb/IIIa inhibitors in carotid angioplasty and stenting. J Endovasc Ther 10:33-41, 2003 20. Ho DS, Wang Y, Chui M, et al: Intracarotid abciximab injection to abort impending ischemic stroke during carotid angioplasty. Cerebrovasc Dis 11:300-304, 2001 21. Lee KY, Heo JH, Lee SI, et al: Rescue treatment with abciximab in acute ischemic stroke. Neurology 56:1585-1587, 2001 22. Feldtman RW, Buckley CJ, Bohannon WT: How I do it: cervical access for carotid artery stenting. Am J Surg 192:779-781, 2006 23. Qureshi AI, Luft AR, Sharma M, et al: Frequency and determinants of postprocedural hemodynamic instability after carotid angioplasty and stenting. Stroke 30:2086-2093, 1999
T
HE BASIC PRINCIPLES of angioplasty and stenting apply to the percutaneous treatment of cervical carotid occlusive lesion. However, the potential for devastating neurologic complications and significant hemodynamic changes separates endovascular treatment of the carotid artery from other vascular beds commonly treated by peripheral vascular specialists.1-7 Carotid angioplasty and stenting (CAS) requires careful patient selection, counseling, and procedural planning. This article will discuss the important technical points of carotid stenting and the perioperative management of patients undergoing carotid stent placement, including strategies for anticoagulation and treatment of procedural hemodynamic changes (Table 1).
Before the Procedure A preoperative imaging study is preferable for the assessment and planning for carotid stent placement.8 An arch aortogram and selective carotid arteriogram or a good quality magnetic resonance angiography with arch, cervical, and intracranial images may be used for evaluation of a patient’s arch and carotid anatomy and CAS planning. This allows for proper selection of access catheters, sheaths, cerebral protection devices, and stents. A thorough and documented neurological exam is essential, especially if a neurologic event occurs in the perioperative period.
Division of Vascular Surgery, Scott & White Hospital and Clinic, Texas A&M University Health Science Center, Temple, TX. Address reprint requests to W. Todd Bohannon, Division of Vascular Surgery, Scott & White Hospital and Clinic, 2401 South 31st Street, Temple, TX 76502. E-mail: [email protected]
0895-7967/08/$-see front matter © 2008 Elsevier Inc. All rights reserved. doi:10.1053/j.semvascsurg.2007.11.003
Antiplatelet Agents Antiplatelet therapy is an essential component of the carotid stenting procedure. Clopidogrel (Plavix), 75 mg daily, is given for 5 days before the stenting procedure and then continued for at least 1 month after carotid stent placement.9 If patients were not treated with clopidogrel for several days prior to the procedure, 300 mg can be given in a single dose before the procedure. Ticlopidine (Ticlid) is an alternative for those who are unable to take clopidogrel.
Periprocedure Anticoagulation Heparin is administered prior to catheterizing the common carotid artery, usually after access is obtained. The usual dose is 100 U/kg. The activated coagulation time (ACT) is used to guide heparin administration with a goal ACT of 250 to 300 seconds achieved prior to intervention. The dosage of heparin should be reduced when glycoprotein IIb/IIIa receptor inhibitors are used. Heparin doses are repeated through the procedure as necessary, however, the procedure is usually completed before the anticoagulant effect of the heparin dose has diminished. Heparin is usually not continued after the procedure. Bivalirudin (Angiomax) is a direct thrombin inhibitor that is preferred by some because of the short half-life of 25 minutes. It is a good alternative in patients that cannot tolerate heparin. Bivalirudin is monitored with the ACT. A bolus of 1 mg/kg is given intravenously followed by an infusion of 0.2 mg/kg per hour. The effects of bivalirudin are prolonged with renal failure. The dosage should be adjusted in dialysis patients and those with moderate to severe renal insufficiency.9 The binding of fibrinogen to the platelet glycoprotein integrin IIb/IIIa mediates platelet aggregation, and inhibitors of the platelet glycoprotein IIb/IIIa receptor have been success3
W.T. Bohannon
4 Table 1 Steps Involved in the Carotid Angioplasty and Stent Procedure Retrograde CFA puncture with placement of 6Fr or 7Fr sheath Anticoagulation Intravenous heparin Target ACT >250 seconds Consider IIB/IIIA inhibitor in high embolic risk patients Cannulate aortic arch branch vessels Guide wire and angled glide catheter placed in external carotid artery Exchange length Amplatz guide wire placed in external carotid artery Guide sheath in common carotid artery Carotid angiogram through guide sheath to delineate stenosis Crossing of target lesion with guide wire or CPD Predilation PTA with 4-mm balloon Consider Atropine 0.5 to 1.0 mg IV before PTA Carotid angiogram to access PTA results Stent placement Postⴚstent dilatation as indicated CPD removal Completion angiograms Abbreviations: ACT, activated clotting time; CFA, common femoral artery; CPD, cerebral protection device; Fr, French; IV, intravenous; PTA, percutaneous transluminal angioplasty.
ful in reducing ischemic complications in coronary artery angioplasty and stenting.9-13 In the past, some have recommended routine use of glycoprotein IIb/IIIa inhibitors to reduce ischemic complications associated with carotid angioplasty and stenting.14,15 Other reports have found either no benefit or higher complication rates associated with IIb/IIIa use.16-19 Therefore, routine use of glycoprotein IIb/IIIa inhibitors in carotid stenting is not necessary due to the increased risk of cerebral hemorrhage or access-site complications. However, IIb/IIIa inhibitors may be a useful adjunct in selected patients. Perioperative intravenous administration of glycoprotein IIb/IIIa inhibitors should be considered in patients who did not have an appropriate preoperative loading of clopidogrel, patients with severe intracranial occlusive disease, and patients with highly ulcerated carotid bifurcation lesions. If a IIb/IIIa inhibitor is used, the dose of heparin should be decreased. Intraoperative glycoprotein IIb/IIIa inhibitors have also been administered intraarterially in situations where thrombus formation has developed within the stent or the patient has a distal embolus.20,21
Carotid Stent Procedure Patient Preparation/Positioning Diagnostic and therapeutic cerebral vascular procedures are done in the angiography suite. Generally, a formal diagnostic carotid and cerebral angiogram has been previously performed. Satisfactory baseline images in multiple plains of the extracranial and intracranial cerebral circulation are impor-
tant prior to intervention. The intracerebral images are necessary as a reference for comparison to the cerebral runoff after CAS. Following successful femoral sheath insertion, the patient is systemically anticoagulated with intravenous heparin as described here previously. A neurologic assessment should be performed after sheath access and throughout the procedure. A noise-making device, such as a horn, is placed in the contralateral hand. It is squeezed throughout the procedure to assess the patient’s motor function and ability to follow verbal instructions. Also, the patient’s speech and cognitive abilities are followed throughout the procedure with a standard series of questions.8
Sheath Access of the Common Carotid Artery The image intensifier is positioned so the aortic arch can be viewed in an oblique projection at approximately 25 to 30 degrees. If the proximal branch artery anatomy is relatively straightforward on the prior angiogram, a new arch aortogram is not necessary. Angiography is performed with isoosmolar contrast. An angled glide catheter (4Fr or 5Fr) is the initial catheter of choice and can be used in conjunction with a 0.035-inch Glidewire to cannulate the innominate artery and right common carotid arteries, as well as the left common carotid artery. If an angle glide catheter is not successful, other catheters with different shaped tips, such as a Simmons catheter can be used. The position of the Glidewire must be monitored closely, and the carotid lesion should not be inadvertently crossed. The angled glide catheter is positioned in the proximal common carotid artery and the initial carotid and intracranial angiograms are obtained in both AP and lateral projections. Next, the image intensifier of the C-arm is positioned so that the carotid bifurcation can best be demonstrated with maximal separation of the internal and external carotid arteries. The glide catheter, over the angled Glidewire, is positioned as far into the external carotid artery as possible. This Glidewire is then exchanged for a stiff wire, such as an Amplatz exchange length guide wire. Over the Amplatz wire, a 90-cm, 6Fr or 7Fr shuttle sheath is positioned in the common carotid artery. The tip of the shuttle sheath should be securely placed within the common carotid artery without advancing the leading introducer tip of the sheath too far into the carotid bifurcation. The introducer tips in many sheaths are not well-visualized, and emboli could occur from the introducer as it encounters an unstable plaque near the bifurcation. Open cervical access to the common carotid artery is a good option for some patients with difficult anatomy or situations where sheath traversal in the arch is not advisable, such as mobile athroma.22
Cerebral Protection Device Placement Once the sheath is securely positioned in the common carotid artery, the optimal angle of the image intensifier is established to best visualize the carotid bifurcation and the entire internal carotid artery. The internal carotid artery anatomy must be appropriate for the cerebral protection device (CPD). There must be adequate length for placement with
Technical tips for carotid angioplasty and stenting minimal tortuosity and sufficient distance away from the carotid lesion. The commercially available carotid stent systems have various types of microporous filters accompanied with a small caliber guide wire. Please review the anatomic criteria and the particular device specifications for the planned CPD prior to the CAS procedure. The preprocedure imaging should help in device planning. Generally, the CPD is advanced across the internal carotid stenosis with the soft and floppy tip of the wire placed within the distal internal carotid artery. Once the CPD is deployed, care must be taken to avoid movement and repositioning of the CPD, as this could cause spasm or injury to the carotid artery. For difficult lesions, the tip of the wire may need to be shaped to allow some directionality with manipulating the wire. If a catheter is needed, an angled 4Fr 120-cm glide catheter is used, rather than the standard 100-cm catheter, because once the guiding sheath is placed, the added length of the glide catheter is necessary for any additional catheter manipulations or wire exchanges. Angiography is performed to verify proper positioning of the CPD and imaging of the carotid lesion before proceeding to angioplasty.
Carotid Angioplasty and Stent Placement Because it is not uncommon for patients to have bradycardia and hypotension with carotid angioplasty, hemodynamic assessments are made continuously throughout the procedure. In order to limit the bradycardia associated with angioplasty of native arterial lesions, the patient is given 0.5 to 1 mg of intravenous atropine. Percutaneous transluminal angioplasty of the carotid stenosis is carefully performed with a 3-mm or 4-mm angioplasty balloon. Monorail or “rapid exchange”⫺type balloon catheters are preferred to the more cumbersome coaxial over-the-wire balloons. Results of the percutaneous transluminal angioplasty are assessed with an angiogram performed through the guide sheath. A saved image of the expanded balloon is useful for device selection. Size and length of the balloon is compared to the native artery and the carotid lesion and used to select an appropriate stent and postdilation balloon. Both the internal carotid artery and the common carotid artery diameters are important considerations when selecting the stent. A self-expanding stent is used following angioplasty of the carotid stenosis. With regard to cell design, open versus closed, most carotid lesions can be treated with either type. However, some lesions may be better suited for treatment with a specific cell design. Because the open cell design is more conformable, this type of stent is often used when tortuous anatomy is encountered. The closed cell design can provide more radial force and may have less plaque protrusion. Thus, a closed cell design is used in carotid stenoses that have a higher embolic potential or significant calcification. Once the stent is deployed, an angiogram is performed to access the stent placement. Following deployment, one must decide whether to postdilate the stent. Generally, we postdilate with an approximately 5-mm balloon with expedient balloon inflation to profile and rapid deflation. It is wise to accept a mild residual carotid artery
5 stenosis and avoid potential complications of emboli or rupture with repeated angioplasty or overdilitation.
Removal of CPD and Completion Images An angiogram is performed following stent deployment and before CPD removal to verify patency of the ICA and flow through the CPD. If there is no flow in the ICA, one must consider a large burden of thrombus or atherosclerotic debris within the filter. Various techniques can be employed to clear the filter, such as aspirating with another catheter positioned in the filter. Associated vasospasm can be treated with nitroglycerine. The CPD is removed per the device-specific instructions, and completion angiogram images obtained. This should include an AP and lateral view of the cervical region. Formal completion intracranial images may be considered. If there is a neurologic deficit on examination, AP and lateral views of the intracranial anatomy should be obtained and compared to the preprocedure images. However, if the patient is neurologically intact and unchanged from baseline, one may consider not performing completion intracranial images and limiting further flushes of contrast into the carotid and ipsilateral brain. If there are no neurologic or technical issues, the catheters and guide wires are then removed. The sheath is then exchanged for a standard 6Fr or 7Fr short sheath, and then this sheath is removed with the assistance of a closure device or once the ACT is ⬍150 seconds.
Treatment of Hemodynamic Changes Abrupt hemodynamic changes are common with the CAS procedure.23 Thus, an awareness of the potential for serious fluctuations in blood pressure and heart rate is important, as these patients often have underlying cardiovascular disease and a poor tolerance for hemodynamic instability. We, therefore, use an arterial line for all cases and have anesthesiology support to assist in the monitoring of our CAS patients.
Bradycardia Bradycardia, due to stimulation of the carotid bulb, is the most common and sudden hemodynamic change seen with the CAS procedure. Hypotension may occur as a result of the bradycardia. A less-common finding, due to stimulation of the carotid bifurcation and a resultant long sinus pause, is asystole. Pacemaker capability should be immediately available, either transvenous or external, but pacemaker insertion is rarely needed if the bradycardia is promptly treated pharmacologically. In patients with atherosclerotic carotid stenosis without a history of prior carotid surgery, atropine is administered (0.5 to 1 mg) prior to balloon dilatation to prevent or reduce severity of the bradycardia. This avoids significant tachycardia, which may have its own potential for complications. The atropine is given approximately 1 minute before balloon inflation. Patients with a baseline bradycardia usually receive the larger initial dose of atropine (1 mg). It is uncommon for patients who have had prior carotid surgery
W.T. Bohannon
6 to have a significant bradycardic response; therefore, they do not usually receive atropine before balloon dilation.
Hypotension Hypotension is commonly associated with the bradycardia, and usually responds to atropine and the resultant increase in heart rate. Occasionally, the hypotensive response to carotid angioplasty and stenting can be severe and more than can be attributed to bradycardia alone. In this instance, a fluid bolus and vasopressors should be considered. Neosynephrine is often used to maintain a systolic pressure of 100 mm Hg or higher. A symptomatic patient with poor cerebral or myocardial perfusion may require a higher target blood pressure. The vasopressor is usually only needed for a few hours, and rarely required longer than 24 hours. Some of the patient’s antihypertensive medications may need to be held or the dosage reduced in the periprocedure period.
Hypertension If hypertension occurs early in the procedure, it is not aggressively treated, as hypotension and bradycardia will often follow after angioplasty and stenting. Hypertension usually improves with mild sedation. If hypertension needs to be addressed, short-acting vasodilators are preferable to -blockers. Patients with severely elevated baseline blood pressure prior to the procedure are at higher risk for a perioperative neurological event. Sustained hypertension is uncommon. If this occurs, it should be aggressively treated to decrease the potential for intracranial hemorrhage in the postoperative period. A systolic blood pressure ⬍150 mm Hg is desirable.
After the Procedure The patient is monitored after the procedure, usually until the following day, for hemodynamic and neurologic changes. A long hospital stay is uncommon due to hypotension and vasopressor requirement. Frequently, the preoperative antihypertensive medications must be decreased before discharge and the blood pressure closely monitored at home. Clopidogrel (75 mg/ day) is continued for 4 to 6 weeks after CAS. Carotid duplex ultrasonography is usually performed within 1 month of the CAS procedure, then at 6 months and 1 year.
Carotid Stenting: Important Technical Points Perform an arteriogram, or other imaging study, with good quality cerebral runoff images prior to carotid stent placement. Always obtain a thorough baseline neurologic exam. Both are important for comparison following angioplasty and stenting if any neurologic changes occur. Clopidogrel should be taken before the procedure for 5 days if possible and it should be given for at least 4 weeks following stent placement. Aspirin should be taken for life. A high-dose load should be considered in patients before CAS who have not been taking clopidogrel. IIb/IIIa inhibitors
should be used in those patients who cannot or have not taken clopidogrel. Heparin should be administered to achieve an ACT of ⬎250 seconds. Bivalirudin (Angiomax) may be used as an alternative. Place an Amplatz or similar stiff guide wire as far as possible in the external carotid artery, but be careful with the position of the guide-wire tip during advancement of the sheath to avoid inadvertent arterial perforation. To help prevent severe bradycardia, atropine should be given prior to angioplasty of carotid stenoses. However, atropine is usually not necessary in patients with history of prior surgery in the region of the carotid bifurcation. In order to limit plaque disruption and emboli, predilate with a smaller-sized balloon. The saved image of the contrastfilled balloon is used to estimate the size of the internal and common carotid arteries. A mild residual stenosis is acceptable. If postdilation is required, avoid repeated angioplasty and overdilation to reduce the risk of emboli and carotid artery rupture. If hypertension occurs during the procedure and requires treatment, short-acting vasodilators are preferred rather than -blockers. With hypotensive patients, treat the bradycardia first. If a vasopressor is needed, consider Neosynephrine and keep the systolic blood pressure ⬎100 mm Hg.
Conclusion Carotid stenting is separated from interventions in other vascular beds by the potential for stroke and significant hemodynamic changes. Hopefully, with a good understanding of the procedure and the management options for perioperative anticoagulation and hemodynamic changes, carotid stenting can be performed safely with minimal complications.
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