Neurological Research A Journal of Progress in Neurosurgery, Neurology and Neurosciences
ISSN: 0161-6412 (Print) 1743-1328 (Online) Journal homepage: http://www.tandfonline.com/loi/yner20
Balloon angioplasty for cerebrovascular disease Martin M. Brown To cite this article: Martin M. Brown (1992) Balloon angioplasty for cerebrovascular disease, Neurological Research, 14:2, 159-162, DOI: 10.1080/01616412.1992.11740040 To link to this article: http://dx.doi.org/10.1080/01616412.1992.11740040
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Date: 11 August 2017, At: 03:18
Balloon angioplasty for cerebrovascular disease Martin M. Brown
Downloaded by [Australian Catholic University] at 03:18 11 August 2017
St George's Hospital Medical School, University of London, London SW17 ORE, UK
Percutaneous transluminal angioplasty (PTA) has become an established treatment for peripheral, renal and coronary vascular disease, where the success rate approaches 90% with complications occurring in less than 5% of patients. There has been a reluctance to recommend PTA of the internal carotid artery (ICA) because of concern about the risks of cerebral embolism. However, there are now a number of reports of technically successful PTA for ICA stenosis, as well as stenosis of other brachiocephalic arteries, demonstrating an improvement in vessel diameter and contour. Complications to date include transient neurological symptoms, asymptomatic carotid dissection and arterial spasm, but the risk of permanent stroke seems to be relatively low. The risks of embolization may be reduced by anticoagulation and avoiding arteries with obvious thrombus or ulceration. Current technical difficulties are likely to be surmounted by improvements in catheter design. PTA is most suitable for smooth ICA stenosis causing haemodynamic symptoms, fibromuscular dysplasia, surgically inaccessible stenosis, and patients with medical risk factors increasing the risks of carotid endarterectomy, such as ischaemic heart disease. Only brief admission is required, avoiding the surgical and anaesthetic risks of carotid endarterectomy. The preliminary results are encouraging enough to set up a randomized trial to determine the risks and benefits. It remains to be seen whether alterations in the calibre or contour of the vessel wall will reduce subsequent stroke. Whether cerebrovascular PTA will enter general use will depend on the balance of the risk-benefit equation. Keywords:Balloon angioplasty; carotid stenosis
INTRODUCTION The history of invasive radiology goes back to the 1920s when cardiac catheterization was first introduced. The idea of introducing a catheter through the skin and passing it along blood vessels was greeted with horror and concern that the procedure was highly dangerous, but cardiac catheterization is now an accepted part of the every day management of patients with cardiac disease. Similar anxiety is frequently expressed today about carotid angioplasty. However, there is considerable evidence to suggest that balloon angioplasty has an acceptable risk rate and may be an appropriate treatment for carotid and vertebral artery stenosis. Dotter and Judkins first described the use of co-axial Teflon catheters to dilate peripheral vascular disease in 19641 . Four years later, Staple 2 introduced a tapering catheter which was less traumatic, but the real advance was in 1974 when Gruntzig and Hopff described the use of inflatable balloon dilation catheters 3 . In 1977 the first coronary PTA was performed 4 and the technique rapidly became an accepted part of the management of patients with ischaemic heart disease, so that by 1986 approximately 150,000 angioplasties were being performed in the USA alone. Over the same period, there was a rapid improvement in the primary success rate of coronary percutaneous transluminal angioplasty (PTA), approaching 90% 5 . The risk of embolization in this large series of coronary PTA was reassuringly low with a rate of non-fatal myocardial infarction of 4%, Correspondence to: Dr Martin M. Brown, MD, Division of Clinical Neuroscience, St George's Hospit al Medical School, Atkinson Morley's Hospital, Copse Hill, Wimbledon, London SW20 ONE, UK. Accepted for publication February 1992.
© 1992 Forefront ~ublishing Group 0161 -6412/ 92/ 020159-05
and mortality rates of 0.2% for single vessel disease, 1% for double vessel disease and 2.8% for triple vessel disease5 . Similar success rates of 90% and distal embolization rates of 5% have been reported for PTA in peripheral vascular disease6 . The concern about the risks of cerebral embolism has understandably led to considerable reluctance to recommend PTA for cerebrovascular disease. However, if the rate of embolization during carotid PTA were no more than at other sites, the risks would be similar to carotid endarterectomy. RISKS OF CAROTID ENDARTERECTOMY The risks of a major stroke or death following carotid endarterectomy in the worst early published series was 21% 7 . Fortunately, this represented an unlucky surgeon, because later series with improved techniques reported risks as low as 4% in an Academic Centre8, or even 2% in the best hands9 . We now have very accurate average figures from the recent European Carotid Surgery Trial (ECST), which reported a surgical risk of stroke or death of 7.5% when European surgeons were operating on severe carotid stenosis, and from the North American Symptomatic Carotid Endarterectomy Trial (NASCET), wbich showed that the average North American surgeon did slightly better with a surgical risk of 5% 10·1 -t: Apart from the cerebrovascular complications of carotid endarterectomy, there is also the anaesthetic risk of myocardial infarction, which is increased in patients with ischaemic heart disease or severe hypertension12 . Other anaesthetic risks accompanying carotid endarterectomy include pneumonia, deep vein thrombosis and mortality from pulmonary embolism 9 . In addition, there may be morbidity from cranial
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Balloon angioplasty for cerebrovascular disease: M.M. Brown
nerve in jury, particularly hypoglossal nerve palsy and occasionally facial palsy. There are also minor disadvantages, which the patient tends to complain of more than the surgeon, such as wound haematoma, infection and cutaneous nerve injury.
ADVANTAGES OF PTA
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Carotid PTA has several potential advantages in comparison with carotid endarterectomy. The procedure is performed under local anaesthetic and avoids an incision in the neck. Admission to hospital can be brief with financial as well as social advantages. Perhaps the major advantage is that the procedure can be considered in patients in whom carotid endarterectom y is contraindicated or has an increased risk, such as ischaemic heart disease. PTA may also be particularly useful in patients with surgical inaccessible lesions, such as high internal carotid stenosis, and for nonatheromatous causes of stenosis such as fibromuscular dysplasia or re-stenosis after endarterectom y.
EXPERIENCE OF CAROTID PTA Despite the anxiety about the risk of embolism, a number of case reports describing angioplasty for cerebrovascular disease appeared in the early 1980s. Initially these were reports of successful dilation of common carotid stenosis through an arteriotomy and then by PTA13•14 . Fibromuscular dysplasia of the internal carotid artery and other bracheocephal ic arteries were also successfully treated by PTA14- 18. With increasing experience, several case reports of PTA for atherosclerotic stenosis of the internal carotid artery appeared, suggesting that the ~rocedure might be safer than previously suggested 1 - 25 . We concluded from these reports that there was -· sufficient evidence to justify a feasibility study of percutaneous transluminal angioplasty in patients with internal carotid stenosis 26 . In our study to date of 12 patients (mean age 56, range 46-66 years), we mostly chose patients with medical or surgical contraindications to endarterectom y, including severe ischaemic heart disease (5 patients), poorly controlled hypertension (1 patient), severe arthritis preventing flexion of the neck (2 patients), arid high cervical fibromuscular dysplasia inaccessible to surgery (1 patient). There are two possible aims of treating carotid stenosis: the first is t0 remove a stenotic source for thrombo-embo lic st:r6'ke, and the second is to improve perfusion pressure to protect against haemodynamic stroke. We initially considered that the latter was more likely to be achieved by angioplasty and therefore one of our main selection criteria was that the patients had to have features suggestive of haemodynamic cerebral ischaemia, such as transient ischaemic attacks occurring during orthostasis, severe bilateral carotid stenosis or diminished cerebrovascular reserve. Our preliminary results confirmed that PTA was a feasible treatment for carotid artery stenosis. Ten arteries were successfully dilated in 8 of the patients. In two patients cannulation of the ICA proved impossible, and in one case the ICA was found to be occluded. In two patients the procedure was abandoned because of transient symptoms lasting less than 10 minutes during cannulation. Four patients also developed transient neurological deficits during balloon inflation, but only one of these lasted more than a few minutes
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Neurological Research, 1992, Volume 14, Suppl
and the longest had recovered within two hours. No permanent complications occurred. Our results correspond with other case reports in the literature19- 28 . By far the lar~est series comes from Dr Porta' s group in Bergarmo 2 . Using single balloon dilation catheters with a diameter of 6-8 mm and 3 or 4 balloon inflations up to a pressure level not exceeding 8 atmospheres they achieve excellent anatomical and clinical results (Figure 1). To date, at least 123 patients with atheromatous internal carotid artery stenosis treated by balloon angioplasty, have been published in the literature (Table 1 ). Transient complications have been reported in 10% of these patients, but only one minor stroke and no major complications have been reported to date. These results are encouraging, although must be treated with caution as any series showing a high complication rate is less likely to have been reported. Equally successful small series of PTA for non-atheromat ous ICA stenosis (Table 2) and other cervical arteries have been reported without serious complications (Table 3).
TECHNIQUE OF PTA The technique of PTA may be vital in mm1m1z1ng embolic complications. The majority of operators, including the group in Bergarmo and ourselves, have used single balloon catheters. The balloon was inflated for a maximum of 3 or 4 occasions and the duration of balloon inflation limited to a maximum of 30 seconds, so as to limit any period of haemodynamic ischaemia. Balloon diameter was also carefully matched to fit the estimated normal vessel calibre. We have also infused heparinized blood through ·the lumen of the balloon catheter during inflation to provide some perfusion during the procedure to the ipsilateral carotid circulation. The presence of thrombus is a contraindication and all groups have used anticoagulation during the procedure and some form of platelet therapy or anticoagulation after PTA to try and prevent thrombo-embo lism. Theron eta/. recently proposed a different technique designed to prevent cerebral embolism during angioplasti 7 . These authors use a triple coaxial catheter, with an occlusive balloon positioned in the internal carotid artery above the angioplasty balloon. The occlusive balloon is inflated before the angioplasty. After deflation and withdrawal of the angioplasty balloon, debris can be aspirated ·from below the occlusive balloon before this is deflated. Cholesterol crystals were found in this debris in 4 out of 6 of Theron eta/.' s patients. However, there are serious disadvantages of this technique which include difficulty placing the introducer catheter, the increased complexity of the procedure and a considerable prolongation in the total catheter time. Most importantly, the period of total internal carotid artery occlusion is 10 minutes or more, which seriously increases the risk of haemodynamic ischaemia. All these factors will increase the. hazards of the procedure and it seems unlikely that the more complicated procedure will prove to be safer than the more simple single balloon occlusion technique.
MECHANISMS OF PTA Two main mechanisms are responsible for the increase in vessel diameter after angioplastl1 - 34 . If the diameter
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Balloon angioplasty lor cerebrovascular disease: M.M. Brown
Figure 1: An example of the excellent restoration of normal calibre of the internal carotid artery achieved by PTA in the best hands (a) stenosis before PTA; (b) good dilation after PTA (from Porta et a/. 28 and reproduced by permission of the publishers)
Table 1:
PTA for atheromatous internal carotid artery stenosis No. of patients
Transient complications
Minor stroke
0
0 0 0 0 0 0 0 0 0
Table 2:
PTA for non-atheromatous ICA stenosis Type
Hasso et a/. 15 Wiggli & Gratzl 19 Brockenheimer & Mathias20 Tsai et a/21 Theron et ai.ZZ Freitag et a/. 23 . Mathias24 Kachel et a/.25 Brown et a/. 26 Theron et a/. 27 Porta et a/28 Total
2 3 6
5 11 15 24 12 13 32 123
1 0 0
1 2 2 4 0
2
Tiersky et a/.29 Tsai et a/. 21 Theron et a/. 22 Cou rtheoux et a/. 30 Mathias 24
12 Total
of the dilated balloon is slightly greater than that of the stenosis, stretching of the vessel wall occurs with desquamation of the intima and superficial splits may occur in the atherosclerotic plaque. If the balloon diameter is much greater than that of the stenosis, then deep focal splits occur in the intima and plaque, but the elastic media usually remains intact. Retraction 0f the intima and distension of the media result in the
Fibromuscular dysplasia Post endarterectomy Fibromuscular dysplasia Post endarterectomy Post endarterectomy Fibromuscular dysplasia
No. of patients
3
5 5 4
19
permanent increase in diameter of the vessel. It is important to note that atherosclerotic plaque is not compressed, stretched or re-distributed by angioplasty, but instead the increase in luminal diameter is achieved by an increase in the outer diameter of the vessel. If the plaque is concentric, the only way the outer diameter can increase is by the occurrence of radial splits in the plaque.
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Table 3:
PTA of other cephalic arteries Artery
Montarjeme et Vitek18 Wiggli & Gratzl19 Tsai et a/.21
a/.17
Kachel et a/. 25 Mathias24
Vertebral External carotid Common carotid External carotid Common carotid Carotid bifurcation Vertebral Common carotid Vertebral · Common carotid
Downloaded by [Australian Catholic University] at 03:18 11 August 2017
Total
No. of patients
13. 10 1 2 10 5 5 2 6 4 58
POTENTIAL RISKS OF PTA The most obvious risk is, of course, embolic stroke from thrombus or plaque disruption during balloon inflation. Stroke may also occur from haemodynamic impairmen t of perfusion during occlusion of the artery at the time of the procedure. Delayed embolic stroke may also occur as a result of thrombus forming on the damaged intima or atheromatous plaque. Dissection is a r.elatively common angiographic complicat ion of angioplasty, but some degree of dissection is an inevitable consequence of successful angioplasty since the mechanism of dilation involves cracking of the plaque, especially if it is concentric. Fortunately, the dissection is usually limited to the site of angioplasty and rarely seems to cause symptoms. Follow up angiograms show that the dissections heal in the majority of cases without complications, although pseudo-aneurysms may form as a result of persistent dissection. Reversible arterial spasm distal to the site of dilation may occur, and is presumably caused by a reaction to the catheter tip. Brief pain in the neck may accompan y balloon dilation and stimulation of the carotid sinus with bradycardia and temporary asystole may also occur. It was initially considered that ulcerated lesions would be more likely to be associated with embolism, but this has not been born out by recent experience24. On the other hand, severely calcified lesions may be less easy to treat and more likely to be associated with severe dissection. THERAPEUTIC VALUE Recurrence of symptoms after carotid PTA appears to be unusual, but the benefit in preventing subsequent stroke is unproven. Fibrotic re-stenosis may occur after carotid angioplasty in up to 15% of patients at one year8 but PTA can readily be repeated in this situation. UNSOLVED QUESTIONS At this early stage, considerable uncertaint y surrounds the whole procedure of PTA for cerebrovascular disease. Numerous catheters are available and improvements in catheter design, such as the introduction of perfusion catheters, advances faster than our capacity to study them scientifically. Technical questions, such as the optimum inflation pressure, duration of inflation, protocol for anticoagu lation and monitoring requirements, remain uncertain. Should distal proximal occlusion catheters be used? The clinical indications for treatment are equally unknown. Whether patients
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with both haemodyn amic and embolic symptoms should be treated, whether patients with ulcers or calcified lesions should be excluded, whether PTA should be offered as an alternative to carotid endartere ctomy, or only if carotid endartere ctomy is contraindi cated and whether the procedure should be limited to carotid arteries or include vertebral stenosis are further questions. It is imperative that these questions should be answered before PTA enters general use for cerebrovascular disease. Such uncertainties can only be resolved by a well designed clinical trial. A randomized prospective international multi-cent re carotid and vertebral artery transluminal angioplasty study (CAVATAS), has therefore been propose9 to determine the benefits and risks of the procedure.
CONCLUSIONS The preliminary evidence suggests that PTA is a feasible alternative to carotid endartere ctomy and may also be beneficial in patients with vertebral artery stenosis. The risks appear comparab le to those of carotid endartere ctomy and the procedure has considerable advantages in avoiding the discomfor t, anaesthetic risks and costs of surgery. However, the procedure cannot be generally recommen ded until the results of the CA VATAS and other trials are available. One cannot do better than quote from a recent editorial 35, carotid PTA provides 'an opportuni ty to provide a superior form of revascularization and to expand the horizons of neurovascular phsyiology'. Emphasizing the importance of careful trials, Ferguson also wrote 'the application of rigorous principles for scientific study may enable us to get it right for the first time this time', and perhaps of the greatest importanc e to the safety of our patients is that 'our techniques must be above reproach' . REFERENCES
2
Dotter CT, Judkins MP. Transluminal treatment of arteriosclerotic obstruction: description of a new technique and a preliminary report of its application. Circulation 1964; 30: 654-670 Staple TW. Modified catheter for percutaneou s transluminal treatment of arteriosclero tic obstructions. Radiology 1968; 91 :
1041 - 1043 3
4
5
6 7
Gruntzig A, Hopff H. Perkutane Rekanalisation chronischer arterieller Verschlusse mit einem neuen Dilatationska theter Modifikation der Dotter-techn ik. Otsch Med Wochenschn , 1974, 99: 2502-2510 Gruntzig AR, Senning A, $eigenthaler WE. Non-operativ e dilation of coronary artery stenosis: percutaneou s transluminal coronary angioplasty. N Eng/ 1 Med 1979; 301 : 61-68 The National Heart, Lung and Blood Institute Registry. Percutaneous transluminal coronary angioplasty in 1985-86 and 1977-81. New Eng/ 1 Med 1988; 318: 265-270 Campbell WB. Angioplasty for intermittent claudication . Br Med 1 1986; 293: 1047-1048 Easton JD, Sherman DG. Stroke and mortality rate in carotid endarterecto my: 228 consecutive operations. Stroke 1977; 8:
565-568 8
9
10
Winslow CM, Solomon DH, Chassin MR, Kosecoff J, Merrick NJ, Brook RH. The appropriateness of carotid endarterecto my. New Eng/ 1 Med 1988; 318: 721-727 Browse NL, Ross-Russell RW. Carotid endarterecto my and the )avid Shunt: the early results of 215 consecutive operations for transient ischaemic attacks. B 1 Surg 1984; 71: 53-57 European Carotid Surgery Trialists Collaboratio n Group: MRC European Carotid Surgery Trial: Interim results for symptomati c patients with severe (70-90% ) or with mild (0-29% ) carotid stenosis. Lancet 1991 ; 337: 1235-1243
Balloon angioplasty for cerebrovascular disease: M.M. Brown
1
12
13
14 15
16
17
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18 19
20
21
22
23
North American Symptomatic Carotid Endarterectomy Trial Collaborations: Beneficial effect of carotid endarterectomy in symptomatic patients with high grade carotid stenosis. New Eng/ f Med 1991; 325: 445-453 Sundt TM, Sandok BA, Whisnant JP. Carotid endarterectomy: complications and pre-operative assessment of risk. Mayo C/in Proc 1975; 50: 301-306 Kerber CW, Cromwell LD, Loehden OL. Catheter dilation of proximal carotid stenosis during distal bifurcation endarterectomy. Am f Neuroradiol 1980; 1: 348-349 Mullan S, Duda EE, Partonas Nj. Some examples of balloon technology in neurosurgery. f Neurosurg 1980; 52: 321-329 Hasso AN, Bird CR, Zinke DE, Thompson JR. Fibromuscular dysplasia of the internal carotid artery: Percutaneous transluminal angioplasty. Am f Neuroradio/ 1981 ; 2 : 175- 180 Motarjeme A, Keifer )W, Zuska A). Percutaneous transluminal angioplasty of the vertebral arteries. Radiology 1981 ; 139: 715-717 Motarjeme A, Keifer JW, Zuska A). Percutaneous transluminal angioplasty of the brachiocephalic arteries. Am f Neuroradio/ 1982; 3: 169-174 Vitek J). Percutaneous transluminal angioplasty of the external carotid artery. Am f Neuroradio/ 1983; 4: 796-799 Wiggli U, Gratz! 0. Transluniinal angioplasty of stenotic carotid arteries-case reports and protocol. Am f Neuroradio/ 1983; 4: 793-795 Bockenheimer SAM, Mathias K. Percutaneous transluminal angioplasty in arteriosclerotic internal carotid artery stenosis. Am f Neuroradiol 1983; 4: 791-792 Tsai FY, Matovich V, Hiesheima G, et a/. Percutaneous transluminal angioplasty of the carotid artery. Am f Neuroradio/ 1986; 7: 349-358 Theron), Raymond ), Cassasco A, Courthoux F. Percutaneous angioplasty of atherosclerotic and post-surgical stenosis of the carotid arteries. Am f Neuroradio/ 1987, 8 : 495-500 Freitag G, Freitag ), Koch R-D, Heinrich P, Wagemann W, Henning H-P, Deike R. Transluminal angioplasty for the
24 25
26
27
28
29
30
31
32 33
34
35
treatment of carotid artery stenosis. Vasa 1987; 16: 67-71 Mathias K. Katheterbehandlung der arteriellen verschlisskrankheit supraaortaber gefasse. Radio/age 1987; 27: 547-554 Kachel R, Endert G, Basche S, Grossmann K, Glaser FH. Percutaneous Transluminal Angioplasty (Dilatation) of Carotid, Vertebral and Innominate Artery Stenoses. Cardiovasc lntervent Radio/1987; 10: 142-146 Brown MM, Butler P, Gibbs), Swash M, Waterston ). Feasibility of percutaneous transluminal angioplasty for carotid artery stenosis. J Neural, Neurosurg Psych 1990; 53 : 238-243 Theron ), Courtheoux P, Alachkar F, Bouvard G, Maiza D. New triple coaxial catheter system for carotid angioplasty with cerebral protection. Am J Neuroradio/ 1990; 11: 869-874 Porta M, Munari LM, Belloni G, Moschini L, Bonaldi G. Percutaneous angioplasty of atherosclerotic carotid arteries. Cerebrovasc Dis 1991; 1: 265-272 Tievsky AL, Druy EM, Mardiat )G. Transluminal angioplasty in post-surgical stenosis of the extracranial carotid artery. A m f Neuroradio/ 1983; 4: 800-802 Courtheoux P, Theron ), Tournade A, Maiza D, Henriet JP, Braun )P. Percutaneous endoluminal angioplasty of postendarterectomy carotid stenosis. Neuroradiology 1987; 29: 186-189 Castaneda-Zuniga WR, Formanek A, Tadavarthy M, eta/. The mechanism of balloon angioplasty. Radiology 1980; 135: 565-571 Block PC, Fallon JT, Elmer D. Experimental angioplasty-lessons from the laboratory. Am J Roentgeno/1980; 135: 907-912 Block P, Myler RK, Stertzer 5, Fallon JT. Morphology after transluminal angioplasty in human beings. New Eng! f Med 1981; 305: 382- 385 Clouse ME, Tomashefski JF, Reinhold RE, Costello P. The mechanical effect of balloon angioplasty. Case report with histology. Am f Roentgeno/1981 ; 137: 867-871 Ferguson R. Getting it right the first time. Am f Neuroradiol 1990; 11 : 875-877
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ISSN: 0161-6412 (Print) 1743-1328 (Online) Journal homepage: http://www.tandfonline.com/loi/yner20
Balloon angioplasty for cerebrovascular disease Martin M. Brown To cite this article: Martin M. Brown (1992) Balloon angioplasty for cerebrovascular disease, Neurological Research, 14:2, 159-162, DOI: 10.1080/01616412.1992.11740040 To link to this article: http://dx.doi.org/10.1080/01616412.1992.11740040
Published online: 23 Jul 2016.
Submit your article to this journal
View related articles
Citing articles: 31 View citing articles
Full Terms & Conditions of access and use can be found at http://www.tandfonline.com/action/journalInformation?journalCode=yner20 Download by: [Australian Catholic University]
Date: 11 August 2017, At: 03:18
Balloon angioplasty for cerebrovascular disease Martin M. Brown
Downloaded by [Australian Catholic University] at 03:18 11 August 2017
St George's Hospital Medical School, University of London, London SW17 ORE, UK
Percutaneous transluminal angioplasty (PTA) has become an established treatment for peripheral, renal and coronary vascular disease, where the success rate approaches 90% with complications occurring in less than 5% of patients. There has been a reluctance to recommend PTA of the internal carotid artery (ICA) because of concern about the risks of cerebral embolism. However, there are now a number of reports of technically successful PTA for ICA stenosis, as well as stenosis of other brachiocephalic arteries, demonstrating an improvement in vessel diameter and contour. Complications to date include transient neurological symptoms, asymptomatic carotid dissection and arterial spasm, but the risk of permanent stroke seems to be relatively low. The risks of embolization may be reduced by anticoagulation and avoiding arteries with obvious thrombus or ulceration. Current technical difficulties are likely to be surmounted by improvements in catheter design. PTA is most suitable for smooth ICA stenosis causing haemodynamic symptoms, fibromuscular dysplasia, surgically inaccessible stenosis, and patients with medical risk factors increasing the risks of carotid endarterectomy, such as ischaemic heart disease. Only brief admission is required, avoiding the surgical and anaesthetic risks of carotid endarterectomy. The preliminary results are encouraging enough to set up a randomized trial to determine the risks and benefits. It remains to be seen whether alterations in the calibre or contour of the vessel wall will reduce subsequent stroke. Whether cerebrovascular PTA will enter general use will depend on the balance of the risk-benefit equation. Keywords:Balloon angioplasty; carotid stenosis
INTRODUCTION The history of invasive radiology goes back to the 1920s when cardiac catheterization was first introduced. The idea of introducing a catheter through the skin and passing it along blood vessels was greeted with horror and concern that the procedure was highly dangerous, but cardiac catheterization is now an accepted part of the every day management of patients with cardiac disease. Similar anxiety is frequently expressed today about carotid angioplasty. However, there is considerable evidence to suggest that balloon angioplasty has an acceptable risk rate and may be an appropriate treatment for carotid and vertebral artery stenosis. Dotter and Judkins first described the use of co-axial Teflon catheters to dilate peripheral vascular disease in 19641 . Four years later, Staple 2 introduced a tapering catheter which was less traumatic, but the real advance was in 1974 when Gruntzig and Hopff described the use of inflatable balloon dilation catheters 3 . In 1977 the first coronary PTA was performed 4 and the technique rapidly became an accepted part of the management of patients with ischaemic heart disease, so that by 1986 approximately 150,000 angioplasties were being performed in the USA alone. Over the same period, there was a rapid improvement in the primary success rate of coronary percutaneous transluminal angioplasty (PTA), approaching 90% 5 . The risk of embolization in this large series of coronary PTA was reassuringly low with a rate of non-fatal myocardial infarction of 4%, Correspondence to: Dr Martin M. Brown, MD, Division of Clinical Neuroscience, St George's Hospit al Medical School, Atkinson Morley's Hospital, Copse Hill, Wimbledon, London SW20 ONE, UK. Accepted for publication February 1992.
© 1992 Forefront ~ublishing Group 0161 -6412/ 92/ 020159-05
and mortality rates of 0.2% for single vessel disease, 1% for double vessel disease and 2.8% for triple vessel disease5 . Similar success rates of 90% and distal embolization rates of 5% have been reported for PTA in peripheral vascular disease6 . The concern about the risks of cerebral embolism has understandably led to considerable reluctance to recommend PTA for cerebrovascular disease. However, if the rate of embolization during carotid PTA were no more than at other sites, the risks would be similar to carotid endarterectomy. RISKS OF CAROTID ENDARTERECTOMY The risks of a major stroke or death following carotid endarterectomy in the worst early published series was 21% 7 . Fortunately, this represented an unlucky surgeon, because later series with improved techniques reported risks as low as 4% in an Academic Centre8, or even 2% in the best hands9 . We now have very accurate average figures from the recent European Carotid Surgery Trial (ECST), which reported a surgical risk of stroke or death of 7.5% when European surgeons were operating on severe carotid stenosis, and from the North American Symptomatic Carotid Endarterectomy Trial (NASCET), wbich showed that the average North American surgeon did slightly better with a surgical risk of 5% 10·1 -t: Apart from the cerebrovascular complications of carotid endarterectomy, there is also the anaesthetic risk of myocardial infarction, which is increased in patients with ischaemic heart disease or severe hypertension12 . Other anaesthetic risks accompanying carotid endarterectomy include pneumonia, deep vein thrombosis and mortality from pulmonary embolism 9 . In addition, there may be morbidity from cranial
Neurological Research, 1992, Volume 14, Suppl
159
Balloon angioplasty for cerebrovascular disease: M.M. Brown
nerve in jury, particularly hypoglossal nerve palsy and occasionally facial palsy. There are also minor disadvantages, which the patient tends to complain of more than the surgeon, such as wound haematoma, infection and cutaneous nerve injury.
ADVANTAGES OF PTA
Downloaded by [Australian Catholic University] at 03:18 11 August 2017
Carotid PTA has several potential advantages in comparison with carotid endarterectomy. The procedure is performed under local anaesthetic and avoids an incision in the neck. Admission to hospital can be brief with financial as well as social advantages. Perhaps the major advantage is that the procedure can be considered in patients in whom carotid endarterectom y is contraindicated or has an increased risk, such as ischaemic heart disease. PTA may also be particularly useful in patients with surgical inaccessible lesions, such as high internal carotid stenosis, and for nonatheromatous causes of stenosis such as fibromuscular dysplasia or re-stenosis after endarterectom y.
EXPERIENCE OF CAROTID PTA Despite the anxiety about the risk of embolism, a number of case reports describing angioplasty for cerebrovascular disease appeared in the early 1980s. Initially these were reports of successful dilation of common carotid stenosis through an arteriotomy and then by PTA13•14 . Fibromuscular dysplasia of the internal carotid artery and other bracheocephal ic arteries were also successfully treated by PTA14- 18. With increasing experience, several case reports of PTA for atherosclerotic stenosis of the internal carotid artery appeared, suggesting that the ~rocedure might be safer than previously suggested 1 - 25 . We concluded from these reports that there was -· sufficient evidence to justify a feasibility study of percutaneous transluminal angioplasty in patients with internal carotid stenosis 26 . In our study to date of 12 patients (mean age 56, range 46-66 years), we mostly chose patients with medical or surgical contraindications to endarterectom y, including severe ischaemic heart disease (5 patients), poorly controlled hypertension (1 patient), severe arthritis preventing flexion of the neck (2 patients), arid high cervical fibromuscular dysplasia inaccessible to surgery (1 patient). There are two possible aims of treating carotid stenosis: the first is t0 remove a stenotic source for thrombo-embo lic st:r6'ke, and the second is to improve perfusion pressure to protect against haemodynamic stroke. We initially considered that the latter was more likely to be achieved by angioplasty and therefore one of our main selection criteria was that the patients had to have features suggestive of haemodynamic cerebral ischaemia, such as transient ischaemic attacks occurring during orthostasis, severe bilateral carotid stenosis or diminished cerebrovascular reserve. Our preliminary results confirmed that PTA was a feasible treatment for carotid artery stenosis. Ten arteries were successfully dilated in 8 of the patients. In two patients cannulation of the ICA proved impossible, and in one case the ICA was found to be occluded. In two patients the procedure was abandoned because of transient symptoms lasting less than 10 minutes during cannulation. Four patients also developed transient neurological deficits during balloon inflation, but only one of these lasted more than a few minutes
160
Neurological Research, 1992, Volume 14, Suppl
and the longest had recovered within two hours. No permanent complications occurred. Our results correspond with other case reports in the literature19- 28 . By far the lar~est series comes from Dr Porta' s group in Bergarmo 2 . Using single balloon dilation catheters with a diameter of 6-8 mm and 3 or 4 balloon inflations up to a pressure level not exceeding 8 atmospheres they achieve excellent anatomical and clinical results (Figure 1). To date, at least 123 patients with atheromatous internal carotid artery stenosis treated by balloon angioplasty, have been published in the literature (Table 1 ). Transient complications have been reported in 10% of these patients, but only one minor stroke and no major complications have been reported to date. These results are encouraging, although must be treated with caution as any series showing a high complication rate is less likely to have been reported. Equally successful small series of PTA for non-atheromat ous ICA stenosis (Table 2) and other cervical arteries have been reported without serious complications (Table 3).
TECHNIQUE OF PTA The technique of PTA may be vital in mm1m1z1ng embolic complications. The majority of operators, including the group in Bergarmo and ourselves, have used single balloon catheters. The balloon was inflated for a maximum of 3 or 4 occasions and the duration of balloon inflation limited to a maximum of 30 seconds, so as to limit any period of haemodynamic ischaemia. Balloon diameter was also carefully matched to fit the estimated normal vessel calibre. We have also infused heparinized blood through ·the lumen of the balloon catheter during inflation to provide some perfusion during the procedure to the ipsilateral carotid circulation. The presence of thrombus is a contraindication and all groups have used anticoagulation during the procedure and some form of platelet therapy or anticoagulation after PTA to try and prevent thrombo-embo lism. Theron eta/. recently proposed a different technique designed to prevent cerebral embolism during angioplasti 7 . These authors use a triple coaxial catheter, with an occlusive balloon positioned in the internal carotid artery above the angioplasty balloon. The occlusive balloon is inflated before the angioplasty. After deflation and withdrawal of the angioplasty balloon, debris can be aspirated ·from below the occlusive balloon before this is deflated. Cholesterol crystals were found in this debris in 4 out of 6 of Theron eta/.' s patients. However, there are serious disadvantages of this technique which include difficulty placing the introducer catheter, the increased complexity of the procedure and a considerable prolongation in the total catheter time. Most importantly, the period of total internal carotid artery occlusion is 10 minutes or more, which seriously increases the risk of haemodynamic ischaemia. All these factors will increase the. hazards of the procedure and it seems unlikely that the more complicated procedure will prove to be safer than the more simple single balloon occlusion technique.
MECHANISMS OF PTA Two main mechanisms are responsible for the increase in vessel diameter after angioplastl1 - 34 . If the diameter
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Balloon angioplasty lor cerebrovascular disease: M.M. Brown
Figure 1: An example of the excellent restoration of normal calibre of the internal carotid artery achieved by PTA in the best hands (a) stenosis before PTA; (b) good dilation after PTA (from Porta et a/. 28 and reproduced by permission of the publishers)
Table 1:
PTA for atheromatous internal carotid artery stenosis No. of patients
Transient complications
Minor stroke
0
0 0 0 0 0 0 0 0 0
Table 2:
PTA for non-atheromatous ICA stenosis Type
Hasso et a/. 15 Wiggli & Gratzl 19 Brockenheimer & Mathias20 Tsai et a/21 Theron et ai.ZZ Freitag et a/. 23 . Mathias24 Kachel et a/.25 Brown et a/. 26 Theron et a/. 27 Porta et a/28 Total
2 3 6
5 11 15 24 12 13 32 123
1 0 0
1 2 2 4 0
2
Tiersky et a/.29 Tsai et a/. 21 Theron et a/. 22 Cou rtheoux et a/. 30 Mathias 24
12 Total
of the dilated balloon is slightly greater than that of the stenosis, stretching of the vessel wall occurs with desquamation of the intima and superficial splits may occur in the atherosclerotic plaque. If the balloon diameter is much greater than that of the stenosis, then deep focal splits occur in the intima and plaque, but the elastic media usually remains intact. Retraction 0f the intima and distension of the media result in the
Fibromuscular dysplasia Post endarterectomy Fibromuscular dysplasia Post endarterectomy Post endarterectomy Fibromuscular dysplasia
No. of patients
3
5 5 4
19
permanent increase in diameter of the vessel. It is important to note that atherosclerotic plaque is not compressed, stretched or re-distributed by angioplasty, but instead the increase in luminal diameter is achieved by an increase in the outer diameter of the vessel. If the plaque is concentric, the only way the outer diameter can increase is by the occurrence of radial splits in the plaque.
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Balloon angioplasty for cerebrovascular disease: M .M. Brown
Table 3:
PTA of other cephalic arteries Artery
Montarjeme et Vitek18 Wiggli & Gratzl19 Tsai et a/.21
a/.17
Kachel et a/. 25 Mathias24
Vertebral External carotid Common carotid External carotid Common carotid Carotid bifurcation Vertebral Common carotid Vertebral · Common carotid
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Total
No. of patients
13. 10 1 2 10 5 5 2 6 4 58
POTENTIAL RISKS OF PTA The most obvious risk is, of course, embolic stroke from thrombus or plaque disruption during balloon inflation. Stroke may also occur from haemodynamic impairmen t of perfusion during occlusion of the artery at the time of the procedure. Delayed embolic stroke may also occur as a result of thrombus forming on the damaged intima or atheromatous plaque. Dissection is a r.elatively common angiographic complicat ion of angioplasty, but some degree of dissection is an inevitable consequence of successful angioplasty since the mechanism of dilation involves cracking of the plaque, especially if it is concentric. Fortunately, the dissection is usually limited to the site of angioplasty and rarely seems to cause symptoms. Follow up angiograms show that the dissections heal in the majority of cases without complications, although pseudo-aneurysms may form as a result of persistent dissection. Reversible arterial spasm distal to the site of dilation may occur, and is presumably caused by a reaction to the catheter tip. Brief pain in the neck may accompan y balloon dilation and stimulation of the carotid sinus with bradycardia and temporary asystole may also occur. It was initially considered that ulcerated lesions would be more likely to be associated with embolism, but this has not been born out by recent experience24. On the other hand, severely calcified lesions may be less easy to treat and more likely to be associated with severe dissection. THERAPEUTIC VALUE Recurrence of symptoms after carotid PTA appears to be unusual, but the benefit in preventing subsequent stroke is unproven. Fibrotic re-stenosis may occur after carotid angioplasty in up to 15% of patients at one year8 but PTA can readily be repeated in this situation. UNSOLVED QUESTIONS At this early stage, considerable uncertaint y surrounds the whole procedure of PTA for cerebrovascular disease. Numerous catheters are available and improvements in catheter design, such as the introduction of perfusion catheters, advances faster than our capacity to study them scientifically. Technical questions, such as the optimum inflation pressure, duration of inflation, protocol for anticoagu lation and monitoring requirements, remain uncertain. Should distal proximal occlusion catheters be used? The clinical indications for treatment are equally unknown. Whether patients
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with both haemodyn amic and embolic symptoms should be treated, whether patients with ulcers or calcified lesions should be excluded, whether PTA should be offered as an alternative to carotid endartere ctomy, or only if carotid endartere ctomy is contraindi cated and whether the procedure should be limited to carotid arteries or include vertebral stenosis are further questions. It is imperative that these questions should be answered before PTA enters general use for cerebrovascular disease. Such uncertainties can only be resolved by a well designed clinical trial. A randomized prospective international multi-cent re carotid and vertebral artery transluminal angioplasty study (CAVATAS), has therefore been propose9 to determine the benefits and risks of the procedure.
CONCLUSIONS The preliminary evidence suggests that PTA is a feasible alternative to carotid endartere ctomy and may also be beneficial in patients with vertebral artery stenosis. The risks appear comparab le to those of carotid endartere ctomy and the procedure has considerable advantages in avoiding the discomfor t, anaesthetic risks and costs of surgery. However, the procedure cannot be generally recommen ded until the results of the CA VATAS and other trials are available. One cannot do better than quote from a recent editorial 35, carotid PTA provides 'an opportuni ty to provide a superior form of revascularization and to expand the horizons of neurovascular phsyiology'. Emphasizing the importance of careful trials, Ferguson also wrote 'the application of rigorous principles for scientific study may enable us to get it right for the first time this time', and perhaps of the greatest importanc e to the safety of our patients is that 'our techniques must be above reproach' . REFERENCES
2
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Gruntzig A, Hopff H. Perkutane Rekanalisation chronischer arterieller Verschlusse mit einem neuen Dilatationska theter Modifikation der Dotter-techn ik. Otsch Med Wochenschn , 1974, 99: 2502-2510 Gruntzig AR, Senning A, $eigenthaler WE. Non-operativ e dilation of coronary artery stenosis: percutaneou s transluminal coronary angioplasty. N Eng/ 1 Med 1979; 301 : 61-68 The National Heart, Lung and Blood Institute Registry. Percutaneous transluminal coronary angioplasty in 1985-86 and 1977-81. New Eng/ 1 Med 1988; 318: 265-270 Campbell WB. Angioplasty for intermittent claudication . Br Med 1 1986; 293: 1047-1048 Easton JD, Sherman DG. Stroke and mortality rate in carotid endarterecto my: 228 consecutive operations. Stroke 1977; 8:
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