(Stroke. 1996;27:1473-1478.)
© 1996 American Heart Association, Inc.
Articles |
US National Survey of Physician Practices for the Secondary and Tertiary Prevention of Ischemic Stroke
Medical Therapy in Patients With Carotid Artery Stenosis
the Center for Health Policy Research and Education (L.B.G., A.J.B., D.B.M., P.W.D., G.P.S.), Divisions of Neurology (L.B.G.) and General Internal Medicine (D.B.M., G.P.S.), Department of Medicine, and Department of Community and Family Medicine (Biometry) (G.P.S.), Duke University, Durham, NC; Division of Neurology, Durham (NC) Department of Veterans Affairs Medical Center (L.B.G.); Research Triangle Institute, Research Triangle Park, NC (A.J.B.); and Center on Aging, University of Kansas, Kansas City (P.W.D.).
Correspondence to Larry B. Goldstein, MD, Box 3651, Duke University Medical Center, Durham, NC 27710. E-mail golds004@mc.duke.edu.
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Abstract |
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Background and Purpose Aspirin or other platelet antiaggregants and anticoagulants are commonly used in many types of patients at elevated stroke risk. However, relatively little is known concerning how practicing physicians use these medications in their patients with extracranial carotid artery stenosis. The identification of variations in practice may help to both direct specific educational efforts and guide further research.
Methods Between August 1993 and February 1994, we surveyed the stroke prevention practices of a stratified random sample of 2000 US physicians. The survey included clinical scenarios that probed the use of aspirin or other platelet antiaggregants and anticoagulants in symptomatic and asymptomatic patients with carotid artery stenoses of 50% to 70% or more than 70%, with and without known surgical contraindications.
Results Sixty-seven percent of those eligible completed the survey (n=1006). More than 85% of physicians responded that they always or often prescribe aspirin or other platelet antiaggregants regardless of degree of carotid artery stenosis, symptom status, or presence of surgical contraindications. However, the reported frequency of use of these medications varied independently according to physician specialty (P=.044). In contrast, in addition to physician specialty, the reported frequency of anticoagulant use varied independently with degree of carotid artery stenosis, symptom status, and presence of surgical contraindications (P<.0001 for each variable). Fifteen percent of physicians responded that they always or often use anticoagulants for asymptomatic patients with 50% to 70% carotid artery stenosis versus 43% who reported doing so for symptomatic patients with a similar degree of stenosis (P<.001); 28% often or always prescribe anticoagulants for asymptomatic patients with more than 70% carotid artery stenosis versus 49% who do so if symptoms are present (P<.001). The odds of noninternist primary care physicians responding that they always or often use anticoagulants were more than five times higher (odds ratio, 5.32; 95% confidence interval [CI], 3.79 to 7.45) than surgical specialists. Compared with surgical specialists, the odds ratios for the use of anticoagulants were 3.65 for internists (95% CI, 2.63 to 5.06) and 1.88 (95% CI, 1.40 to 2.53) for neurologists.
Conclusions These data show the following: (1) Aspirin or other platelet antiaggregants are used by most physicians regardless of degree of carotid artery stenosis, symptom status, or presence of surgical contraindications; (2) anticoagulants are prescribed selectively, with each of these variables influencing their use; and (3) the use of both classes of agents varies with physician specialty training.
Key Words: anticoagulants • antiplatelet agents • aspirin • carotid stenosis • stroke prevention
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Introduction |
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TopAbstractIntroductionSubjects and MethodsResultsDiscussionReferences |
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The efficacy of platelet antiaggregant therapy in patients at elevated risk of stroke has been established through several randomized, controlled trials.1 These medications are commonly recommended by physicians for secondary and tertiary stroke prevention.2 Anticoagulants are also used for stroke prevention in selected patients. However, aside from the use of warfarin in patients with atrial fibrillation,3 there is a general lack of controlled data concerning the use of anticoagulants in patients at risk for stroke.4
On the basis of the results of randomized, controlled trials, selected symptomatic5 6 7 and asymptomatic8 9 patients with stenosis of the extracranial carotid artery may now be considered potential candidates for carotid endarterectomy. These trials either specifically required5 7 8 9 or encouraged10 the use of aspirin as part of "best medical therapy" in both patients undergoing carotid endarterectomy and in nonoperated control subjects. The use of anticoagulants was not mentioned in any of the trial reports. A single survey of the opinions and practices of neurologists in the United States regarding the use of antithrombotic drugs focused on the management of acute stroke.11 Little information is available concerning how practicing physicians use platelet antiaggregants and anticoagulants in specific types of patients with stenosis of the extracranial carotid artery, including those deemed to have contraindications for carotid endarterectomy. Through a series of specific patient scenarios, the US National Survey of Physician Practices for the Secondary and Tertiary Prevention of Ischemic Stroke collected data to address these questions.2 The survey queried how frequently physicians report they use these medications in symptomatic and asymptomatic patients with defined degrees of stenosis of the extracranial carotid artery in the presence and absence of surgical contraindications. The identification of variations in practice may help to both direct specific educational efforts and guide further research.
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Subjects and Methods |
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Details of the survey methodology and analytic procedures have previously been presented.2 Briefly, the study population consisted of all physicians, excluding residents and fellows, who were practicing in the United States, actively involved in patient care, and listed in the 1993 American Medical Association's Physician Masterfile under one of the following primary specialties: Family Practice; General Practice; General Internal Medicine; Neurosurgery; Neurology; Vascular Surgery; and a group of Internal Medicine subspecialties including Diabetology, Hematology, Geriatrics, Nephrology, Rheumatology, and Endocrinology. A stratified random sample was then chosen by selecting physicians from a list ordered by region for each specialty (each specialty formed a stratum, with the group of Internal Medicine subspecialties combined to form a single stratum). Survey instruments were mailed to approximately equal numbers of the randomly selected physicians from each specialty (n=2000). Survey data were collected between August 1993 and February 1994, approximately 2 years after the results of three randomized trials indicating that endarterectomy was efficacious in selected symptomatic patients with high-grade stenosis of the carotid artery were available5 6 7 but before the results of the Asymptomatic Carotid Atherosclerosis Study9 were known.
The self-administered questionnaire included 23 items and was divided into two distinct parts. The first part of the survey consisted of items that described physician and practice characteristics and the availability of selected procedures and tests. The second part of the questionnaire consisted of 12 patient scenarios. These included eight vignettes that probed the reported use of diagnostic modalities, surgery, and medical therapies in patients with a defined stenosis of the extracranial carotid artery and who were either asymptomatic or symptomatic. In addition to queries concerning the use of carotid endarterectomy,12 physicians were asked how frequently they would use aspirin or other platelet antiaggregants or anticoagulant therapy for each type of patient for the prevention of subsequent stroke. The specified patients were as follows: (1) asymptomatic with 50% to 70% stenosis of the extracranial carotid artery; (2) asymptomatic with more than 70% stenosis of the extracranial carotid artery; (3) symptomatic (transient ischemic attack [TIA] or completed minor stroke within the last month) with 50% to 70% stenosis of the extracranial carotid artery; or (4) symptomatic with more than 70% stenosis of the extracranial carotid artery. Responses were provided separately for each of the indicated types of patients in the presence and absence of surgical contraindications. The nature of surgical contraindications was not specified but left to the respondents' judgments.
To simplify the analyses, the responses of Family Practice specialists and General Practice physicians (noninternist primary care physicians) were combined as "Primary Care," General Internal Medicine physicians and Internal Medicine subspecialists were combined as "Internal Medicine," and Neurosurgeons and Vascular Surgeons were combined as "Surgery." The physicians reported using platelet antiaggregants or anticoagulants always, often, sometimes, seldom, or never in a given clinical setting. Because the categories do not represent meaningful or exactly specified differences in clinical practice, and to further simplify the presentation of the analyses, the responses "always or often" and "seldom or never" were combined ("always/often" and "seldom/never").
Weighted data adjusted for nonresponses were used in the statistical analyses.2 This was accomplished with the SUrvey DAta ANalysis (SUDAAN) software package (Research Triangle Institute).13 These SUDAAN analyses included estimates of basic statistical parameters such as means, percentages, regression coefficients, test statistics (
2, Fisher's F, and Student's t tests), and standard errors. Multinomial multiple logistic regression analyses were used to estimate odds ratios.14 These analyses permit the assessment of the independent relationships of several factors when considered together.
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Results |
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Information to establish eligibility status was obtained for all but 34 of the 2000 physicians who were mailed surveys. Of the 1966 physicians for whom a response to the survey was received, 465 were ineligible because they did not participate in active patient care or were not in one of the eligible specialties or because of death or retirement. Overall, 67% of eligible physicians fully responded to the survey (n=1006).2 All physician specialties and geographic regions were well represented among the respondents.2
Use of Platelet Antiaggregants
The reported frequency of use of aspirin or other platelet antiaggregants in patients with stenosis of the extracranial carotid artery did not vary with clinical characteristics that included the patient's symptom status (asymptomatic versus TIA or minor stroke within the last month), the degree of carotid artery stenosis (50% to 70% versus >70%), and the presence or absence of surgical contraindications (Table 1
; P>.05 for each variable). The reported frequency of use of these medications varied with physician specialty training (Table 1; P=.044). Neurologists (P=.009) and internists (P=.045) had approximately two thirds higher odds of responding that they used platelet antiaggregants in these clinical situations compared with surgeons. The difference in reported use of platelet antiaggregants between noninternist primary care physicians and surgeons was not significant (P=.240). Overall, more than 85% of physicians responded that they always or often use platelet antiaggregants for patients with stenosis of the extracranial carotid artery. However, for patients without surgical contraindications, more surgeons reported that they seldom or never use platelet antiaggregants for the prevention of subsequent stroke than physicians with other specialty training (Table 2).
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Use of Anticoagulants
In contrast to platelet antiaggregants, the reported frequency of use of anticoagulants varied with the patient's symptom status, the degree of carotid artery stenosis, and the presence of surgical contraindications in addition to the specialty training of the physician (Table 3). The odds of physicians responding that they would use anticoagulants in patients with stenosis of the extracranial carotid artery with recent symptoms (TIA or minor stroke) were three times higher than for similar patients who did not have symptoms (P<.0001). The odds of physicians reporting that they used anticoagulants in patients with more than 70% stenosis of the carotid artery were 50% greater than for patients with 50% to 70% stenosis, independent of both symptom status and whether or not the patient had surgical contraindications (P<.0001). The odds of physicians responding they used these medications was more than one third higher in patients with surgical contraindications than in patients without surgical contraindications, independent of both symptom status and the indicated degrees of carotid artery stenosis (P<.0001).
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The Figure gives the reported frequency of use (always or often versus seldom or never) of anticoagulants for the prevention of subsequent stroke in asymptomatic and recently symptomatic patients with either 50% to 70% or more than 70% stenosis of the extracranial carotid artery in the absence or presence of surgical contraindications. Both the degree of stenosis of the extracranial carotid artery and the presence or absence of recent symptoms affected the reported frequency of use of anticoagulants. Nearly twice the proportion of physicians responded that they always or often used anticoagulants for asymptomatic patients without surgical contraindications who had 50% to 70% carotid artery stenosis compared with similar patients with more than 70% carotid artery stenosis (16.7±2.0% versus 31.5±2.6%). In scenarios with patients without surgical contraindications and 50% to 70% carotid artery stenosis, the proportion of physicians indicating that they always or often used anticoagulants was almost three times higher if the patient had recent symptoms compared with otherwise similar patients who were asymptomatic (16.7±2.0% versus 46.4±2.7%). The presence of recent symptoms did not quite double the proportion of physicians who reported always or often using anticoagulants in patients without surgical contraindications and more than 70% carotid artery stenosis (31.5±2.6% versus 53.8±2.7%). Furthermore, the proportions of physicians reporting that they often or always used anticoagulants were higher in scenarios with patients who had surgical contraindications than for otherwise similar patients without surgical contraindications. As was found for patients without surgical contraindications, greater degrees of carotid artery stenosis and the presence of recent symptoms increased the proportion of physicians responding that they always or often used anticoagulants. For patients with surgical contraindications, 29.1±2.3% of physicians reported that they always or often used anticoagulants for an asymptomatic patient with 50% to 70% carotid artery stenosis compared with 38.7±2.6% who would do so for an asymptomatic patient with more than 70% carotid artery stenosis. The presence of recent symptoms nearly doubled the proportion of physicians who reported always or often using anticoagulants in patients with surgical contraindications and 50% to 70% carotid artery stenosis (53.4±2.7% versus 29.1±2.3% for similar asymptomatic patients). The proportion of physicians always or often using anticoagulants also increased by approximately 50% in the presence of recent symptoms in patients with surgical contraindications and more than 70% carotid artery stenosis (58.6±2.6% versus 38.7±2.6% for similar asymptomatic patients).
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In addition to these clinical variables, the reported frequency of use of anticoagulants varied independently with physician specialty training (Table 3
). The odds of noninternist primary care physicians responding they would use anticoagulants were more than five times higher than those for surgeons (P<.0001). The odds of internists reporting that they used anticoagulants were more than 3.5 times higher (P<.0001), and those for neurologists were nearly two times higher (P<.0001) than those for surgeons. This pattern of reported use based on physician specialty was similar in each clinical scenario regardless of the absence or presence of surgical contraindications (Figure). We previously reported that nearly 1 in 4 noninternist primary care physicians and 1 in 5 internists responded that they would seldom or never use carotid endarterectomy in a patient without surgical contraindications and who had a recent TIA or minor stroke and more than 70% stenosis of the ipsilateral extracranial carotid artery.12 Thirty-nine percent of noninternist primary care physicians and 22% of internists indicating that they would seldom or never use carotid endarterectomy in such patients reported that they would always or often use anticoagulants under these circumstances.
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Discussion |
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TopAbstractIntroductionSubjects and MethodsResultsDiscussionReferences |
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The central findings of the present analyses are as follows: (1) For patients with a defined stenosis of the extracranial carotid artery, most physicians report using aspirin or other platelet antiaggregants regardless of the patient's degree of carotid artery stenosis (50% to 70% versus >70%), symptom status (asymptomatic versus recent TIA or minor stroke), or the presence of surgical contraindications. (2) Physicians report using anticoagulant medications more selectively, with each of these variables independently influencing their use. (3) The reported use of both platelet antiaggregants and anticoagulants varies with physician specialty training.
Overall, more than 99% of surveyed physicians report that they use platelet antiaggregants for secondary and tertiary stroke prevention.2 More than 85% of physicians responded that they always or often use platelet antiaggregants for patients with stenosis of the extracranial carotid artery. However, the odds of neurologists and internists reporting that they used aspirin or other platelet antiaggregants to prevent subsequent stroke in patients with carotid artery stenosis were more than 1.5 times higher than for surgeons (Tables 1 and 2). Noninternist primary care physicians also reported using platelet antiaggregants more frequently than surgeons, but the difference was not significant (Table 1). The reasons for the relative lack of use of platelet antiaggregants by surgeons are not clear. The use of platelet antiaggregants is associated with an approximately 23% reduction in the risk of nonfatal stroke.1 In addition, patients with extracranial carotid artery stenosis are known to be at significant risk for ischemic cardiac disease.15 16 The use of platelet antiaggregants is associated with a significant lowering of cardiac morbidity and mortality in high-risk populations.17 Because of these data, clinical trials of carotid endarterectomy have generally included the use of aspirin as part of best medical therapy in both those undergoing carotid endarterectomy and control subjects treated without carotid endarterectomy. One surgical trial that restricted the use of aspirin in patients undergoing endarterectomy for asymptomatic carotid artery stenosis found that a significantly higher proportion of patients undergoing the operation had myocardial infarction compared with patients who did not undergo carotid endarterectomy but were given aspirin.18 Furthermore, the use of aspirin after carotid artery surgery may reduce the incidence of perioperative stroke.19 Thus, there is no reason to expect that surgeons would use platelet antiaggregants for patients at elevated stroke risk less often than physicians with other specialty training.
In contrast to the use of platelet antiaggregants, the reported frequency of use of anticoagulants varied independently with the patient's degree of carotid artery stenosis, symptom status, and the presence of surgical contraindications in addition to the physician's specialty training (Table 3, Figure). The reported use of anticoagulants was higher for patients with more than 70% stenosis of the extracranial carotid artery than for those with 50% to 70% stenosis, higher in patients with recent TIA or minor stroke than in asymptomatic patients, and higher in patients who had surgical contraindications than in those without such contraindications. Anticoagulants have been used for decades to prevent stroke in selected high-risk patients, but no conclusive evidence exists to support their routine use in patients with TIA4 or patients with asymptomatic high-grade carotid artery stenosis. Because no randomized trial of adequate size has been performed, the role of anticoagulation remains controversial even in patients with crescendo TIAs and in patients with TIAs who are being evaluated for carotid endarterectomy.4 Although it is not unexpected that physicians might use anticoagulants, even for a brief period, in newly symptomatic patients with severe extracranial carotid artery stenosis (Figure, bottom right panel), the basis for using these medications in asymptomatic patients and in patients with more moderate degrees of stenosis is uncertain.
The differences in the reported frequency of use of anticoagulants based on the specialty training of the physician are surprising (Figure). The present survey queried the use of anticoagulants as a group and did not explicitly ask whether the physician would specifically use heparin or warfarin for prevention of subsequent stroke in a given type of patient with stenosis of the extracranial carotid artery. Therefore, different groups of physicians may have interpreted the questions related to anticoagulant use differently. Despite this, the difference in reported anticoagulant use based on physician specialty training is striking (Table 3, Figure). Of particular concern is the relatively frequent reported use of anticoagulants by both noninternist primary care physicians and internists for patients without surgical contraindications who had a recent TIA or minor stroke and more than 70% stenosis of the ipsilateral extracranial carotid artery (Figure, bottom right panel). Nearly 1 in 4 noninternist primary care physicians and 1 in 5 internists responded that they would seldom or never use carotid endarterectomy in this setting.12 Thirty-nine percent of the noninternist primary care physicians and 22% of internists who responded that they would seldom or never use carotid endarterectomy also reported that they always or often use anticoagulants for these patients. Although this implies that an unproved therapy (anticoagulation) may be used by some physicians in place of a therapy of proven value (carotid endarterectomy in this particular clinical scenario), physician practices as reported in a survey may not reflect their actual practices.20 However, these findings suggest an important potential topic for physician education.
Physicians in practice must frequently make recommendations for patient care without the benefit of unambiguous data from well-designed and conducted clinical trials. Some of the reported variations in practice reflected in the responses of physicians to questions posed in the present survey reflect this uncertainty. However, clinical trial data are rapidly becoming available to help guide the treatment of specific types of patients at elevated risk of stroke. Some of the variations in the use of platelet antiaggregants and anticoagulants reported in the present survey raise concern that these clinical trial data have not been thoroughly incorporated into physician practices.
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Acknowledgments |
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This study was performed as part of the Stroke Prevention Patient Outcomes Research Team (PORT) and was funded through contract 282-91-0028 from the US Agency for Health Care Policy Research. The authors wish to acknowledge Gordon H. DeFriese, PhD, Eugene Z. Oddone, MD, and John E. Paul, PhD, who contributed to the design of the survey instrument.
Received April 8, 1996; revision received May 21, 1996; accepted May 21, 1996.
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References |
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1. Antiplatelet Trialists' Collaboration. Collaborative overview of randomised trials of antiplatelet therapy, I: prevention of death, myocardial infarction, and stroke by prolonged antiplatelet therapy in various categories of patients. BMJ. 1994;308:81-106.
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Goldstein LB, Bonito AJ, Matchar DB, Duncan PW, DeFriese GH, Oddone EZ, Paul JE, Akin DR, Samsa GP. US National Survey of Physician Practices for the Secondary and Tertiary Prevention of Ischemic Stroke: design, service availability, and common practices. Stroke. 1995;26:1607-1615.
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Atrial Fibrillation Investigators: Atrial Fibrillation Aspirin, Anticoagulation Study, Boston Area Anticoagulation Trial for Atrial Fibrillation Study, Canadian Atrial Fibrillation Anticoagulation Study, Stroke Prevention in Atrial Fibrillation Study, Veterans Affairs Stroke Prevention in Nonrheumatic Atrial Fibrillation Study. Risk factors for stroke and efficacy of antithrombotic therapy in atrial fibrillation: analysis of pooled data from five randomized controlled trials. Arch Intern Med. 1994;154:1449-1457.
4. Feinberg WM, Albers GW, Barnett HJM, Biller J, Caplan LR, Carter LP, Hart RG, Hobson RW II, Kronmal RA, Moore WS, Robertson JT, Adams HP Jr, Mayberg M. Guidelines for the management of transient ischemic attacks: from the Ad Hoc Committee on Guidelines for the Management of Transient Ischemic Attacks of the Stroke Council of the American Heart Association. Stroke. 1994;25:1320-1335.[Medline] [Order article via Infotrieve]
5. North American Symptomatic Carotid Endarterectomy Trial Collaborators. Beneficial effect of carotid endarterectomy in symptomatic patients with high-grade carotid stenosis. N Engl J Med. 1991;325:445-453.[Abstract]
6. European Carotid Surgery Trialists' Collaborative Group. MRC European Carotid Surgery Trial: interim results for symptomatic patients with severe (70-99%) or with mild (0-29%) carotid stenosis. Lancet. 1991;337:1235-1243.[Medline] [Order article via Infotrieve]
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Mayberg MR, Wilson E, Yatsu F, Weiss DG, Messina L, Hershey LA, Colling C, Eskridge J, Deykin D, Winn R. Carotid endarterectomy and prevention of cerebral ischemia in symptomatic carotid stenosis. JAMA. 1991;266:3289-3294.
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Hobson RW II, Weiss DG, Fields WS, Goldstone J, Moore WS, Towne JB, Wright CB, VA Coop Study Group. Efficacy of carotid endarterectomy for asymptomatic carotid stenosis. N Engl J Med. 1993;328:221-227.
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Executive Committee for the Asymptomatic Carotid Atherosclerosis Study. Endarterectomy for asymptomatic carotid artery stenosis. JAMA. 1995;273:1421-1428.
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11.
Marsh EE III, Adams HP Jr, Biller J, Wasek P, Banwart K, Mitchell V, Woolson R. Use of antithrombotic drugs in the treatment of acute ischemic stroke: a survey of neurologists in practice in the United States. Neurology. 1989;39:1631-1634.
12.
Goldstein LB, Bonito AJ, Matchar DB, Duncan PW, Samsa GP. US National Survey of Physician Practices for the Secondary and Tertiary Prevention of Ischemic Stroke: carotid endarterectomy. Stroke. 1996;27:801-806.
13. Shah BV, Barnwell BG, Hunt PN, LaVange LM. SUDAAN User's Manual, Release 6.00. Research Triangle Park, NC: Research Triangle Institute; 1992.
14. Barnwell BG, Bieler GS, Shah BV. SUDAAN Technical Report: The MULTILOG Procedure, Release 6.6. Research Triangle Park, NC: Research Triangle Institute; 1996.
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16. Chambers BR, Norris JW. Outcome in patients with asymptomatic neck bruits. N Engl J Med. 1986;315:860-865.[Abstract]
17. Antiplatelet Trialists' Collaboration. Secondary prevention of vascular disease by prolonged antiplatelet treatment. BMJ. 1988;296:320-331.
18. Mayo Asymptomatic Carotid Endarterectomy Study Group: results of a randomized controlled trial of carotid endarterectomy for asymptomatic carotid stenosis. Mayo Clin Proc. 1992;67:513-518.[Medline] [Order article via Infotrieve]
19.
Lindblad B, Persson NH, Takolander R, Bergqvist D. Does low-dose acetylsalicylic acid prevent stroke after carotid surgery? A double-blind, placebo-controlled randomized trial. Stroke. 1993;24:1125-1128.
20.
Montano DE, Phillips WR. Cancer screening by primary care physicians: a comparison of rates obtained from physician self-report, patient survey, and chart audit. Am J Public Health. 1995;85:795-800.
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