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(Stroke. 1995;26:1607-1615.)
© 1995 American Heart Association, Inc.

Articles

US National Survey of Physician Practices for the Secondary and Tertiary Prevention of Ischemic Stroke

Design, Service Availability, and Common Practices

Larry B. Goldstein, MD; Arthur J. Bonito, PhD; David B. Matchar, MD; Pamela W. Duncan, PhD; Gordon H. DeFriese, PhD; Eugene Z. Oddone, MD; John E. Paul, PhD; Donald R. Akin, MS Gregory P. Samsa, PhD

From the Center for Health Policy Research and Education (P.W.D.) and the Divisions of Neurology (L.B.G.) and General Internal Medicine (D.B.M., E.Z.O.), Department of Medicine, Duke University, Durham, NC; the Center for Health Services Research in Primary Care (D.B.M., E.Z.O., G.P.S.) and Division of Neurology (L.B.G.), Durham Department of Veterans Affairs Medical Center, Durham, NC; Research Triangle Institute (A.J.B., J.E.P., D.R.A.), Research Triangle Park, NC; and the Cecil G. Sheps Center for Health Services Research, University of North Carolina at Chapel Hill (G.H.D.).

Correspondence to Larry B. Goldstein, MD, Box 3651, Duke University Medical Center, Durham, NC 27710. E-mail golds004@mc.duke.edu.

	Abstract

Top Abstract Introduction Subjects and Methods Results Discussion Appendix References

 
Background and Purpose Stroke is largely a preventable disease. However, there are little data available concerning the use of stroke prevention diagnostic and treatment modalities by practicing physicians. These data are critical for the rational allocation of resources and targeting of educational efforts. The purposes of this national survey were to gather information about physicians' stroke prevention practice patterns and their attitudes and beliefs regarding secondary and tertiary stroke prevention strategies.

Methods We conducted a national survey of stroke prevention practices among a stratified random sample of 2000 physicians drawn from the American Medical Association's Physician Masterfile. The survey focused on the availability of services and the use of diagnostic and preventive strategies for patients at elevated risk of stroke.

Results Sixty-seven percent (n=1006) of eligible physicians completed the survey. Diagnostic studies considered readily available by at least 90% of physicians included carotid ultrasonography, transthoracic echocardiography, Holter monitoring, and brain CT and MRI scans. MR angiography was perceived as being readily available by 68% and transesophageal echocardiography by 74% of respondents. Twelve percent of physicians reported cerebral arteriography and 10% reported carotid endarterectomy as not being readily available. Multiple logistic regression analyses showed that the availability of services varied with physician specialty (noninternist primary care, internal medicine, neurology, surgery), practice setting (nonmetropolitan versus small metropolitan or large metropolitan areas), and for carotid endarterectomy, region of the country (South, Central, Northeast, and West). The odds of carotid endarterectomy being reported as readily available were approximately 2.5 to 3.5 times greater for physicians practicing in the central, northeastern, and western regions compared with those practicing in the South, independent of practice setting and specialty. With regard to stroke prevention practices, 61% of physicians reported prescribing 325 mg of aspirin for stroke prevention, while 33% recommend less than 325 mg and 4% use doses of 650 mg or more. Seventy-one percent of physicians using warfarin reported monitoring anticoagulation with international normalized ratios, and 78% reported monitoring anticoagulated patients at least once a month. Fewer than 20% of physicians reported knowing the perioperative carotid endarterectomy complication rates at the hospital where they perform the operation themselves or refer patients to have the procedure done.

Conclusions Although all routine and most specialized services for secondary and tertiary stroke prevention are readily available to most physicians, variation in availability exists. The use of international normalized ratios for monitoring warfarin therapy has not yet become universal. Physician knowledge of carotid endarterectomy complication rates is generally lacking. Depending on their causes, these problems may be addressed through targeted physician education efforts and systematic changes in the way in which services are provided.

Key Words: anticoagulants • aspirin • carotid endarterectomy • diagnosis • stroke prevention

	Introduction

Top Abstract Introduction Subjects and Methods Results Discussion Appendix References

 
During the last three decades, epidemiological studies and clinical trials have provided critical scientific bases for both secondary prevention of cerebrovascular disease in high-risk patients and for tertiary prevention in those who have had a nondisabling stroke. For example, it is clear that the use of aspirin is beneficial in patients at risk for stroke. A meta-analysis conducted by the Antiplatelet Trialists Collaboration based on data from more than 70 000 "high-risk" individuals randomized in 142 studies found an approximately 30% reduction in the rate of nonfatal stroke, an approximately 30% reduction in the rate of nonfatal myocardial infarction, and an approximately 20% reduction in the rate of vascular death (each P<.00001).¹ The more than 10 000 patients who had a prior transient ischemic attack or stroke were treated for a mean duration of 3 years in 18 randomized trials. Treatment with aspirin resulted in an overall reduction in subsequent vascular events of 37 per 1000 patients (P<.00001).¹ Several randomized trials have now shown that long-term anticoagulation with warfarin reduces the risk of stroke in selected patients with nonvalvular atrial fibrillation.^{2 3 4 5 6} When performed with high-sensitivity thromboplastin, the use of the INR provides a reliable means of monitoring warfarin therapy.⁷ Three recent randomized trials (North American Symptomatic Carotid Endarterectomy Trial [NASCET],^{8 9} European Carotid Surgery Trial [ECST],^{10 11} and the VA Cooperative Symptomatic Carotid Surgery Trial [VACS]¹² ) each showed that when performed with acceptable rates of morbidity and mortality, carotid endarterectomy improves outcomes in selected symptomatic patients with high-grade stenosis of the extracranial carotid artery.¹³

Despite these and other advances, areas of significant controversy remain.¹⁴ The optimal dose of aspirin for prevention of stroke has not been established.^{14 15 16 17} The use of low doses of aspirin has been advocated because low doses of aspirin block platelet cyclooxygenase (and therefore platelet aggregation) but have little effect on endothelial prostacyclin (which produces vasodilatation).¹⁸ However, increasing doses of aspirin are positively correlated with increasing frequencies of gastrointestinal hemorrhage.¹⁹ The need for angiographic evaluation of all carotid endarterectomy candidates has been questioned, and proceeding to endarterectomy solely on the basis of noninvasive studies has been advocated.^{20 21 22}

There are few data available concerning the patterns of use of established or controversial stroke prevention treatment modalities by practicing physicians or the application of these treatment modalities to specific types of patients. These data are critical for the rational allocation of resources and specific targeting of educational efforts. The purposes of this national survey were to gather information about physicians' stroke prevention practice patterns and their attitudes and beliefs regarding secondary and tertiary stroke prevention strategies. The target population for the survey was actively practicing US physicians involved in secondary and tertiary prevention of stroke. The survey obtained four categories of data: (1) physician and practice characteristics; (2) perceived availability of basic and advanced stroke prevention services; (3) queries concerning basic stroke prevention strategies; and (4) a set of 12 clinical patient scenarios that probed the use of specific diagnostic and treatment modalities. This report focuses on the first three aspects of this national physician survey. The results of the remaining portion will be reported in a later publication.

	Subjects and Methods

Top Abstract Introduction Subjects and Methods Results Discussion Appendix References

 
Survey Development
A self-administered questionnaire was prepared by an interdisciplinary team of physicians, social scientists, and health services researchers. The questionnaire was intended for use in a mail survey of physicians and was designed to be completed in 15 to 20 minutes. The instrument went through pretesting and revision to both optimize the response rate and reduce the number of unanswered items. The final questionnaire included 23 items and was divided into two distinct parts. The first consisted of items that described physician and practice characteristics and the availability of selected procedures and tests. Physician characteristics included the physician's year of birth and graduation from medical school as well as primary practice specialty (see below). Practice characteristics included the following: (1) practice setting (private solo practice, private small group practice with fewer than five physicians, private group practice with more than five physicians, group or staff model health maintenance organization, community hospital, industrial clinic, public health department clinic, Veterans Affairs or military hospital, private nonprofit clinic, or academic medical center); (2) number of patients seen in an average week; (3) percentage of patients with major risk factors for stroke (defined as patients with previous transient ischemic attack or stroke, hypertension, diabetes, or cardiac disease); and (4) the physicians' estimates of the percentages of patients in their practices who were covered by Medicaid, uninsured, over age 65 years, female, white, black, or of Hispanic ancestry. With the use of the practice location and the Area Resource File, it was possible to determine whether a physician practiced within a large metropolitan area (>1 million people), a small metropolitan area (<1 million people), or a nonmetropolitan area (area not included in a metropolitan statistical area). The availability of selected services or procedures that might be used for the care of patients at risk for stroke was rated as either being provided by the physician him/herself, readily available, or not readily available. In addition, there were items concerning basic stroke prevention strategies. These included items that queried the following: (1) aspirin use for stroke prevention excluding patients with nonvalvular atrial fibrillation (viz, does not prescribe aspirin, prescribes <325 mg/d, 325 mg/d, 650 mg/d, or 975 mg/d); (2) whether the physician knew the perioperative mortality and stroke rates for carotid endarterectomy in the hospital where he/she refers patients; (3) the frequency of monitoring coagulation profiles after the initial adjustment period in patients taking warfarin (does not prescribe warfarin, once a month, once every other month, once every 3 months, once every 6 months, or once a year or less); and (4) the method used by the physician's laboratory to report the coagulation profile (does not prescribe warfarin, prothrombin time in seconds, precalculated prothrombin time ratio, INR, or does not know).

Sample Design
The study population was all physicians, excluding residents and fellows, who were practicing in the United States, actively involved in patient care, and listed in the 1993 AMA 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. The sampling frame (5000 physicians randomly drawn from the 146 665 listed in the AMA Masterfile under the indicated specialties) was obtained from Medical Marketing Systems, Inc. A stratified random sample was then chosen by first selecting physicians from a geographically ordered list for each specialty (each specialty formed a stratum, with the exception of the group of internal medicine subspecialties, which were combined to form a single stratum). Survey instruments were then mailed to approximately equal numbers of the randomly selected physicians from each specialty (n=2000).

Data Collection Process
Surveys returned as undeliverable were remailed as new addresses were identified. New addresses were obtained from former colleagues at the "old" address, State Boards of Medical Examiners, and through directory assistance. After 7 weeks, nonrespondents were sent a second mailing of the questionnaire with a reminder note from the principal investigator. After an additional 7-week period, nonrespondents were contacted by telephone and either prompted to return their questionnaire or asked to complete the questionnaire by telephone.

Statistical Analysis
Adjusted weighted responses were used to perform statistical analyses, including cross-tabulations and logistic regression analyses. The weighting procedure is described in the Appendix. This was accomplished with the SUrvey DAta ANalysis (SUDAAN) software package (Research Triangle Institute)²³ because (1) many of the parameters are ratios (requiring the use of nonlinear statistics), so that the standard error estimates could not be expressed in a closed form (the Taylor series linearization is used by SUDAAN); and (2) the SUDAAN procedures properly adjust for the complex sample design used for the survey. The statistical analyses include estimates of basic parameters such as row and column percentages, simple regression coefficients, test statistics (², Fisher's F, and Student's t tests), standard errors, and multiple logistic regression analyses (including odds ratios).

	Results

Top Abstract Introduction Subjects and Methods Results Discussion Appendix References

 
Survey Response
Information to establish eligibility status was obtained for all but 34 of the 2000 physicians who were mailed surveys. Sometimes the response was nothing more than an unopened returned survey marked deceased, retired, or moved. The telephone follow-up process boosted the initial mail response rates by obtaining actual interviews through that means and by identifying further ineligible physicians who did not respond because the survey did not apply to them or their patients. Of the 1966 physicians contacted, 465 were ineligible due to death, retirement, not being in active patient care, or not being in one of the eligible specialties. Of the remaining 1501 physicians, 204 actively refused to cooperate with the survey, while 235 passively refused by not completing the survey form after repeated attempts to gain their cooperation. The adjustment for refusal assumed that the 1062 physicians who at least partially completed the survey form represented the eligible physicians. Of these 1062 physicians, 1006 fully completed the survey form.

Overall, 67.0% of the eligible physicians responded fully to the survey, either by mail or telephone. There were some differences in the rates of response according to specialty (the percentages of eligible physicians that fully completed the survey were as follows: family practice, 55%; general practice, 51%; general internal medicine, 60%; neurosurgery, 86%; neurology, 70%; vascular surgery, 84%; and internal medicine subspecialties, 73%). There were no differences in response rates by age group, but physicians from the western and southern regions of the country responded at a slightly lower rate than those from the northeastern and central (midwestern) regions.²⁴ 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."

Respondent Characteristics
Table 1 shows the characteristics of respondents according to practice specialty, the main stratifying variable for sample selection. The mean age of physicians responding to the survey was similar across specialties. The respondent pool was composed of relatively more physicians from states in the central and southern regions than in the Northeast or West, but all regions of the country are well represented. The distribution of respondents varied somewhat by setting among the specialties. Most respondents (80.7% of the total) practiced in either a large metropolitan or small metropolitan area. Proportionally more primary care physicians (28.5%) practiced in nonmetropolitan areas than the other groups (11.3% of internists, 8.4% of neurologists, and 6.4% of surgeons practiced in nonmetropolitan areas; P<.001). Almost 90% of physicians had either private solo, small group, or large group practices. Less than 5% practiced in an academic health center. Overall, approximately 30% of physicians reported that more than 50% of the patients in their practice had "major" risk factors for stroke, and almost 40% reported that more than 50% of the patients in their practice were older than 65 years. As expected, practices in which more than 50% of patients were older than 65 years were also practices with more than 50% of patients having major stroke risk factors (70% of these physicians reported that more than half of their patients had major stroke risk factors).

View this table: [in this window] [in a new window]   Table 1. TABLE 1. Respondent Characteristics

Based on population estimates calculated from the survey data, approximately 36 400 US physicians have practices in which more than 50% of patients have "major" stroke risk factors. An estimated 62% of these physicians are internists, 30% are noninternist primary care physicians, 6% are neurologists, and 3% are surgeons. Thus, the vast majority of physicians providing secondary and tertiary prevention services are noninternist primary care physicians and internists. However, because noninternist primary care physicians serve a relatively younger patient population, they tend to care for proportionally fewer patients at increased risk of stroke (Table 1).

Reported Unavailability of Services
Physicians were asked whether or not specific stroke prevention or diagnostic services were performed by the physicians themselves or were readily available in their practice settings. For these analyses, physicians who responded that they either performed the procedure themselves or the service was readily available were combined and then compared with those for whom the service was not readily available. Fig 1 shows the percentage of physicians reporting that the indicated service was not readily available. TCD, used most frequently for the detection and monitoring of vasospasm in patients with subarachnoid hemorrhage, was not readily available to more than half of the surveyed physicians. The use of TCD as a tool to aid secondary and tertiary stroke prevention is under investigation. MRA and TEE, two relatively new and evolving technologies, were not available to nearly one third and one fourth of physicians, respectively. Basic imaging services, such as transthoracic echocardiography and brain MRI, were unavailable to less than 10% of physicians. Carotid duplex ultrasonography, brain CT, Holter monitoring, coagulation profiles, and electrocardiography were available to almost all physicians. However, approximately one in 10 physicians reported that cerebral arteriography and carotid endarterectomy, two stroke prevention services assumed to be routinely available throughout the western world, were not readily available.

View larger version (20K): [in this window] [in a new window]   Figure 1. Bar graph shows reported unavailability of services. Physicians were asked whether specific stroke prevention or diagnostic services were performed by the physicians themselves, were readily available, or were not readily available. The percentages of physicians reporting that the indicated service was not readily available are shown. TTE indicates transthoracic echocardiography; carotid duplex, carotid duplex ultrasonography; and EKG, electrocardiogram.

Reported unavailability of services was not uniform across specialties, practice settings, or regions of the country. Fig 2 depicts the unavailability of specific stroke prevention services by physician specialty. These services were selected because they were reported by an overall 10% or more of physicians as not being readily available to them (Fig 1). MRA, TEE, cerebral arteriography, and carotid endarterectomy were reported as not readily available by a higher proportion of primary care physicians and internists than neurologists or surgeons. For primary care physicians, the unavailability of these services may partially reflect the relatively small number of practices reporting a high proportion of patients with "major" stroke risk factors and the relatively large proportion of these practices in nonmetropolitan areas (Table 1, see below). These differences were less dramatic for internists (Fig 2).

View larger version (18K): [in this window] [in a new window]   Figure 2. Bar graphs show reported unavailability of services by specialty. The unavailability of specific stroke prevention services that were selected because they were reported as not being readily available by an overall 10% or more of physicians is shown (see Fig 1). Error bars indicate 1 SEE.

Fig 3 shows the reported availability of the selected services according to practice setting. Each of the selected services, as expected, was more frequently reported as not readily available by physicians practicing in nonmetropolitan areas.

View larger version (17K): [in this window] [in a new window]   Figure 3. Bar graphs show reported unavailability of services by practice setting. The unavailability of specific stroke prevention services that were selected because they were reported as not being readily available by an overall 10% or more of physicians is shown (see Fig 1). Error bars indicate 1 SEE.

When the availability data were analyzed by region of the country, no significant differences were found for MRA or TEE; however, both cerebral arteriography and carotid endarterectomy were reported as being relatively less readily available to physicians in the central and southern regions (Fig 4). Carotid endarterectomy was viewed as being least available in the South (where it was reported as not readily available by nearly 20% of physicians).

View larger version (20K): [in this window] [in a new window]   Figure 4. Bar graphs show reported unavailability of services by region. The unavailability of specific stroke prevention services that were selected because they were reported as not being readily available by an overall 10% or more of physicians is shown (see Fig 1). Error bars indicate 1 SEE.

Multiple logistic regression analyses were next used to determine whether specialty, region, and setting independently affected the reported availability of the selected services (Table 2).²⁵ Each model was significant at P<.01. Physician specialty and practice setting but not region independently contributed to the explained variance in the availability of MRA, TEE, and cerebral angiography. The odds of reporting each service as readily available were approximately 2 to 10 times greater for physicians practicing in small metropolitan and large metropolitan areas compared with those practicing in nonmetropolitan areas, regardless of specialty or region of the country. Compared with noninternist primary care physicians, the odds of neurologists and surgeons reporting MRA, TEE, and cerebral angiography as being readily available were approximately 3 to 6 times greater. Internists differed from noninternist primary care physicians only with regard to the perceived availability of TEE. Physician specialty, practice setting, and region each independently contributed to the explained variance in the perceived availability of carotid endarterectomy. The odds of carotid endarterectomy being reported as readily available were 11 times greater for neurologists than for noninternist primary care physicians. The availability of the procedure was not viewed differently by noninternist primary care physicians and internists. For physicians practicing in small and large metropolitan areas, the odds of reporting carotid endarterectomy as being readily available for their patients were 7 to 9 times greater than for those practicing in nonmetropolitan settings. The odds of carotid endarterectomy being reported as readily available were approximately one half to one third as great for physicians practicing in the South compared with those practicing in other regions of the country, independent of practice setting and specialty.

View this table: [in this window] [in a new window]   Table 2. TABLE 2. Multiple Logistic Regression Analyses and Odds Ratio Estimates for Selected Stroke Prevention Services by Specialty, Setting, and Region

Common Stroke Prevention Practices
Use of Aspirin for Stroke Prevention
Almost all physicians (99%) reported prescribing aspirin for stroke prevention. Overall, only 4% of physicians reported prescribing 650 mg or more of aspirin per day for this purpose. Relatively more neurologists prescribe aspirin at this dose level (Fig 5). The vast majority (90%) of physicians prescribe 325 mg/d or less.

View larger version (26K): [in this window] [in a new window]   Figure 5. Bar graph shows use of aspirin for stroke prevention. Physicians were asked what dose of aspirin they prescribe for stroke prevention. The figure provides a breakdown of aspirin dosing both by specialty and for all respondents combined (total). Overall, only 4% of physicians prescribe aspirin at a dose of 650 mg/d. Relatively more neurologists prescribe this dose than other groups of physicians. The most frequently prescribed dose was 325 mg/d. Error bars indicate 1 SEE.

Anticoagulation Practices
Approximately 30% of physicians did not receive coagulation profiles with INRs. The differences among specialties was not significant. Anticoagulated patients were reported as being monitored at least once a month by 80% and less frequently by 14% of physicians. Monitoring frequency differed by specialty group, with 21% of primary care physicians and only 5% to 8% of other groups of physicians reporting that they monitored anticoagulated patients at greater than a monthly interval (P<.001).

Knowledge of Perioperative Carotid Endarterectomy Complication Rates
The benefit of endarterectomy for patients with symptomatic high-grade extracranial carotid artery stenosis is highly dependent on its risk.²⁶ Physicians were asked whether they knew the complication rates at the hospital where they perform the operation or refer patients to have the procedure. Overall, only 19% of physicians reported knowing the perioperative mortality rate, and 15% reported knowing the perioperative stroke rate. Fig 6 gives breakdowns of these data by physician specialty. Significantly more neurologists and surgeons reported knowing these rates than noninternist primary care physicians and internists (P<.001).

View larger version (19K): [in this window] [in a new window]   Figure 6. Bar graph shows knowledge of perioperative carotid endarterectomy complication rates. Physicians were asked whether they knew the complication rates at the hospital where they perform the operation or refer patients to have the procedure performed. Overall, only 19% of physicians reported knowing the perioperative mortality rate, and only 15% reported knowing the perioperative stroke rate. These rates varied by specialty. Error bars indicate 1 SEE.

	Discussion

Top Abstract Introduction Subjects and Methods Results Discussion Appendix References

 
Stroke remains the third leading cause of death and the major cause of disability among adults in the United States.²⁷ Importantly, stroke is largely a preventable disease. Both general population-based and targeted approaches to stroke prevention have been tried and advocated.²⁸ The population-based approach relies on educational efforts toward lifestyle modification within the general population and represents primary prevention strategies. The targeted approach gives emphasis to specific diagnostic and therapeutic interventions for persons at elevated risk for the purpose of identifying and possibly eliminating a particular risk factor or groups of risk factors. These diagnostic or therapeutic interventions represent secondary and tertiary strategies. This study represents the first detailed, systematic, nationally based survey of physician practices relative to the secondary and tertiary prevention of stroke.

The survey was aimed at groups of physicians most likely to provide stroke prevention services. Overall, approximately 30% of physicians reported that more than half of the patients in their practice had "major" risk factors for stroke, and almost 40% reported that more than half of the patients in their practice were older than 65 years. The survey methodology was designed to optimize the response rates of busy physicians actively involved in patient care. Sixty-seven percent of the eligible physicians responded fully to the survey, either by mail or through subsequent telephone interviews. This response rate compares favorably with other physician surveys.²⁹ These data suggest that the target population for the study was effectively surveyed.

Most stroke prevention services are provided by noninternist primary care physicians and internal medicine specialists. Not surprisingly, routine services that may be used for stroke prevention such as electrocardiography, coagulation profiles, Holter monitoring, carotid duplex ultrasonography, and transthoracic echocardiography are viewed by almost all physicians as being readily available. Even modern neuroimaging techniques such as brain MRI and CT are widely available (Fig 1). However, certain stroke prevention services were reported as unavailable by a surprisingly high proportion of physicians (Fig 1). Although MRA and TEE are relatively new technologies whose utilities remain somewhat debatable, cerebral angiography and carotid endarterectomy represent long-standing procedures that play key roles in the evaluation and treatment of selected patients at elevated risk of stroke. The perceived availabilities of these services varied significantly by physician specialty (being lowest for noninternist primary care physicians and internists) and practice setting, and for carotid endarterectomy, by region of the country (Figs 2 through 4, Table 2). While it is not unexpected that neurologists or surgeons performing vascular procedures in metropolitan areas would find these services to be relatively more available, the reason for the perceived relative unavailability of carotid endarterectomy to physicians practicing in the southern region of the country remains uncertain. This is of particular importance because the South represents the country's "Stroke Belt," with the highest incidence of the disease.³⁰ If the perceived unavailability of carotid endarterectomy to physicians practicing in the South is due to actual unavailability, then the problem could be addressed through the allocation of additional resources. If this is not the case, then the problem could be addressed through clarification of referral mechanisms and targeted provider education. Clarification and streamlining of referral mechanisms might also partially address the perceived unavailability of the selected services to physicians practicing in nonmetropolitan areas (Fig 3, Table 2).

Aspirin is one of the most commonly used drugs for secondary and tertiary prevention of stroke.¹⁴ There has been considerable debate concerning the optimal dose of aspirin for this purpose in patients who have had transient ischemic attack or nondisabling stroke.^{14 15 16 17} Despite this controversy between proponents of "high-dose" and "low-dose" aspirin, the survey data indicate that most physicians currently prescribe 325 mg/d, with only 4% prescribing doses of 650 mg/d or more (Fig 5).

Safe anticoagulation practices are required for therapy with warfarin to be effective in reducing the risk of stroke in patients with nonvalvular atrial fibrillation. The use of INRs that employ high-sensitivity thromboplastin is currently regarded as the optimal technique for monitoring patients anticoagulated with warfarin.^{7 31} Yet 30% of surveyed physicians did not receive coagulation profiles with INRs. This is a somewhat lower percentage than expected based on a survey of laboratory monitoring of warfarin therapy performed in Utah.³² The Utah study found that fewer than 50% of laboratories gave reports with INRs. Of additional concern, physicians in Utah had little interest in having their laboratories provide reports in this format.³² Safe anticoagulation practices also require frequent monitoring. Although complex statistical models have been developed to help determine the optimal monitoring interval for individual patients,³³ anticoagulation clinics generally monitor patients monthly.^{31 33} Approximately 80% of physicians reported monitoring their anticoagulated patients at least monthly. However, the reported monitoring frequency varied significantly by specialty, with primary care physicians more frequently monitoring at greater than monthly intervals. Physician advocacy of INRs and targeted education of optimal monitoring techniques could address these problems.

The risk of carotid endarterectomy may vary significantly among institutions and among surgeons. Although several surgical series report perioperative (30-day) mortality rates of approximately 1% and stroke rates of approximately 3%,^{34 35 36 37} community-based studies have reported mortality rates of approximately 3%, with combined morbidity and mortality rates of approximately 6% to 20%.^{38 39 40 41 42} Randomized clinical trials have reported perioperative mortality and morbidity rates of approximately 4% to 6%.^{9 11 12 43} A recent analysis of carotid endarterectomies for symptomatic stenosis performed at 12 academic medical centers found that 8.5% of 697 patients had either stroke or myocardial infarction or died during the postoperative period of hospitalization.⁴⁴ Overall combined morbidity and mortality from carotid endarterectomy in the United States has been estimated to be between 6% and 10%.⁴⁵ Despite its clinical importance, only a small proportion (<20%) of surveyed physicians reported knowing the perioperative complication rates at the hospital where they perform the operation or refer patients to have the procedure (Fig 6). Only approximately 50% of neurologists and 60% of surgeons knew these rates. The reason for this lack of knowledge is not addressed in our survey. These data may not be systematically obtained and recorded in hospitals; if the data are available they may not be disseminated, and if they are disseminated physicians may not be noting the results. Because of its importance, careful prospective surveillance of carotid endarterectomy complication rates and their dissemination to clinical decision-makers should be advocated.

In summary, we find that routine and specialized stroke prevention services are readily available to most physicians. Those in general practice and those practicing in nonmetropolitan areas more frequently report certain services as being unavailable to their patients. The use of INRs for monitoring warfarin therapy has not yet become universal. Carotid endarterectomy is viewed as being relatively less available to physicians in the South, despite the high incidence of cerebrovascular disease in this region of the country. Physician knowledge of carotid endarterectomy complication rates is generally lacking. Depending on their causes, these problems may be addressed through targeted physician education efforts and systematic changes in the way in which services are provided.

	Selected Abbreviations and Acronyms

 

AMA = American Medical Association INR = international normalized ratio MRA = magnetic resonance angiography TCD = transcranial Doppler ultrasonography TEE = transesophageal echocardiography

	Acknowledgments

 
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.

	Appendix

Top Abstract Introduction Subjects and Methods Results Discussion Appendix References

 
The final analysis weights were computed in five steps (independently within each stratum; the strata were the physician specialty groups as described in "Subjects and Methods") starting with the computation of the sampling weights. In each of the subsequent steps, the weights from the previous step were in turn adjusted for noncontacts, refusals, partial completions, and the number of physicians listed in the specialty in the AMA Physician Masterfile.

The sampling weights were the ratios of the number of physicians sampled from the AMA Physician Masterfile (sampling frame) to the number of physicians selected for the physician survey for a stratum.

The adjustment for noncontact assumed that the contacted physicians represented all (contacted and noncontacted) physicians. The noncontact adjusted weights for the contacted physicians were the sampling weights for the contacted physicians adjusted by the ratio of the weight-sum for all selected physicians in a stratum and the weight-sum for all contacted physicians in a stratum. The noncontact adjusted weights for the noncontacted physicians were set to zero.

The refusal adjusted weights for the ineligible physicians were set equal to the noncontact adjusted weights. The refusal adjusted weights for the (partial or full) completion physicians were equal to their noncontact adjusted weights multiplied by the ratio of the weight-sum for all eligible physicians in a stratum and the weight-sum for the (partial or full) completion physicians in a stratum. The refusal adjusted weights for the refusing physicians were set to zero.

The adjustment for partial completion assumed that the physicians fully completing the survey represented the physicians partially or fully completing the form. The partial completion adjusted weights for full completion physicians were their refusal adjusted weights multiplied by the ratio of the weight-sums of the partial and full completion physicians in a stratum and the weight-sums for the full completion physicians in a stratum. The partial completion adjusted weights for the ineligible physicians were set equal to the refusal adjusted weights. The partial completion adjusted weights for partial completion physicians were set equal to zero.

The final adjustment forces the partial completion adjusted weight-sums for the ineligible and full completion physicians to equal the AMA Physician Masterfile counts for each stratum. This adjustment assumes that the ineligible and full completion physicians represent all physicians in the AMA Physician Masterfile at the time of selection.

Received May 5, 1995; revision received June 13, 1995; accepted June 13, 1995.

	References

Top Abstract Introduction Subjects and Methods Results Discussion Appendix References

 

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