Stroke Prevention Essentials

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Public Health Special Report -- May 2001  

By Desiree B. Pendergrass, MD, MPH; Peter W. Pendergrass, MD, MPH; Diane H. Solomon, MD; and Robert G. Hart, MD

Epidemiology of Stroke

Stroke is the third leading cause of death and the leading cause of serious, long-term disability in the United States. Each year, approximately 600,000 individuals suffer a new (500,000) or recurrent (100,000) stroke (1). In 1998, stroke killed 158,448 people, accounting for about one in every 14.8 deaths in the United States. 

Of those who survive an initial stroke or transient ischemic attack (TIA), 14% will have a recurrence and about 22% of men and 25% of women will die within one year. This means that on average, one person suffers a stroke every 53 seconds and one person dies from a stroke every 3.3 minutes. Note that stroke prevalence increases with age (1).

The majority of strokes are ischemic (2). Approximately 60% result from atherothrombosis in extracranial and larger intracranial vessels, 20% result from small-vessel lacunar disease, 15% are from cardiac emboli due to atrial fibrillation or myocardial infarction, and 5% are the result of other unusual causes (3).

The economic burden associated with stroke is substantial and was estimated to be $51 billion (direct and indirect costs) in 1999 (4). In 1997, Medicare paid $3.8 billion, or $5,955 per discharge, for beneficiaries discharged from short-stay hospitals for stroke (5). 

Risk Factors for Stroke

Many risk factors for stroke have been identified (Table 1). Most importantly, prior TIA or stroke identifies those patients at highest risk for stroke and those who have the most to gain by aggressive risk factor intervention. Of patients with TIAs related to severe carotid stenosis, 12% to 13% will experience a stroke within the first year after symptoms begin and 30% to 35%, before the end of five years. In addition, the presence of atrial fibrillation (AF) represents a sixfold increased risk in stroke. It is important to identify each person's risk factors for stroke.

Appropriate history, physical examination, and laboratory testing must be performed on an annual basis to identify and address newly acquired risk factors. 

Stroke Prevention

Numerous guidelines for the prevention of stroke have been published in the past five years (2). While areas of disagreement and controversy exist, it is important to focus on areas of agreement with proven efficacy. This article uses prevention guidelines developed by the American Heart Association's Stroke Council (Table 2). Once risk factors have been identified, physicians need to set therapeutic goals, institute appropriate therapy, and monitor risk factors on a routine basis to ensure that therapeutic goals are achieved and maintained. Note that prevention strategies differ in high-risk patients who have a history of TIA or stroke, i.e., secondary prevention.

The appropriate management of patients with carotid artery stenosis is controversial. Because of the marginal benefit of endarterectomy on asymptomatic stenosis in most clinical situations (20 patients would have to undergo carotid endarterectomy [CEA] to prevent one stroke over five years), recommendations vary among published guidelines, and either surgical or medical therapy is an acceptable option. Higher risk subgroups of patients with asymptomatic stenosis may exist (perhaps based on degree of stenosis and lack of collateral circulation) for whom the benefits of CEA would be greater. To date, such subgroups have not been convincingly identified.

Patients with a previous stroke or TIA and with severe (70% to 99%) carotid artery stenosis should undergo CEA by a surgeon with a documented low complication rate (e.g., morbidity and mortality less than 6%) (8,9). CEA also should be considered for patients with moderate (50% to 69%) symptomatic stenosis, depending on their surgical risk and stroke risk factors.

Aspirin reduces the risk of ischemic stroke by approximately 25% (10). Despite this fact, only 72% of Texas Medicare patients with a primary diagnosis of TIA or stroke were discharged on aspirin or other antiplatelet agent (11). While some controversy exists as to the appropriate initial therapy, an emerging consensus in North America appears to favor the use of aspirin at 325 mg/d for stroke prevention (12). All patients should be evaluated for aspirin intolerance and aspirin failure (e.g., recurrent TIA or stroke while on aspirin therapy). If either are positive, the use of another antiplatelet agent may be considered (13-15). Other agents proven to be effective include extended-release dipyridamole plus aspirin, clopidogrel, and ticlopidine (requires complete blood count [CBC] every two weeks for three months because of 1% to 2% risk of neutropenia). 

Stroke Prevention in Patients with AF

The use of dose-adjusted warfarin has been shown to decrease the risk of stroke in patients with AF (16). Since 1992, several authoritative groups, including the American College of Chest Physicians (ACCP), the American Heart Association, the American College of Physicians, and the American Academy of Neurology have recommended strongly and consistently that high-risk patients with AF be prescribed dose-adjusted warfarin therapy (2,17-21). Despite these recommendations, warfarin remains underused. Multiple studies have shown that it is used in fewer than half of the patients with AF (22-26). Hospital discharge data reveal that only 44.5% of Texas Medicare patients with AF were discharged on warfarin (11). This underutilization places patients with AF at excess risk for stroke and places an increased economic burden on the health care system. Research supported by the Agency for Health Care Policy and Research found that expanded use of warfarin could reduce by half the 80,000 strokes each year due to AF and estimated that proper anticoagulation therapy could save about $600 million annually (2).

The methodology to determine which patients with AF are at high risk for stroke remains somewhat controversial. Several risk stratification schemas exist (27-29), but the most commonly recommended is that of the ACCP (21). Using the ACCP criteria (Table 3), approximately 65% of patients with AF will be eligible for warfarin therapy, and 15% will fall into the low-risk category. Note that bleeding risk must be determined for each patient. High-risk patients should be treated with dose-adjusted warfarin (INR [international normalized ratio] target, 2.5; range, 2-3). Aspirin should be reserved for low-risk patients or for those who cannot safely take warfarin. 

Patient Education

In the outpatient setting, patient education about stroke warning signs is critical in assuring a timely response to stroke symptoms. The importance of this is seen in the literature, which demonstrates that treatment with thrombolytics reduces both morbidity and mortality from stroke when administered within three hours of symptom onset (30-32). Education should be ongoing, and patients should be told to call 911 immediately if any of the following common warning signs occur (33): 

  • Sudden numbness or weakness of the face, arm, or leg, especially on one side of the body;
  • Sudden confusion or trouble speaking or understanding;
  • Sudden trouble seeing in one or both eyes;
  • Sudden trouble walking, dizziness, loss of balance, or coordination; or
  • Sudden, severe headache with no known cause.

For patients treated with warfarin, education regarding bleeding risk, dietary interactions, medication interactions, and the importance of laboratory monitoring is required. 

Stroke and Quality Improvement

The Health Care Quality Improvement Project (HCQIP) is a continuous quality improvement program implemented by the Health Care Financing Administration. It is designed to ensure the quality of care for all Medicare beneficiaries and focuses on six disease-specific topics, including acute myocardial infarction, congestive heart failure, stroke and AF, pneumonia, breast cancer screening, and diabetes mellitus.

The national stroke project focuses on the following three process-of-care measures: 

  • Warfarin at discharge for patients with AF;
  • Antithrombotics at discharge for patients with TIA or stroke; and
  • Avoidance of sublingual nifedipine in patients with an acute stroke.

For additional information on this initiative, call the Texas Medical Foundation at (800) 725-9216.

 

References

  1. American Heart Association. 2001 Heart and Stroke Statistical Update. Dallas, Texas: American Heart Association; 2000.
  2. Guidelines for medical treatment for stroke prevention. American College of Physicians. Ann Intern Med. 1994;121:54-55.
  3. Bogousslavsky J, Van Melle G, Regli F. The Lausanne Stroke Registry: analysis of 1,000 consecutive patients with first stroke. Stroke . 1988;19:1083-1092.
  4. American Heart Association. Economic Cost of Cardiovascular Diseases. Available at: www.americanheart.org/statistics/economic.html.
  5. Health Care Financing Review, Statistical Supplement. Baltimore, Md: Health Care Financing Administration; 1997.
  6. Goldstein LB, Adams R, Becker K, et al. Primary prevention of ischemic stroke: a statement for healthcare professionals from the Stroke Council of the American Heart Association. Stroke . 2001;32:280-299.
  7. American Diabetes Association. Clinical Practice Recommendations 2001: standards of medical care for patients with diabetes mellitus. Diabetes Care . 2001;24(suppl 1):S33-S43.
  8. 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.
  9. Barnett HJ, Taylor DW, Eliasziw M, et al. Benefit of carotid endarterectomy in patients with symptomatic moderate or severe stenosis: North American Symptomatic Carotid Endarterectomy Trial Collaborators. N Engl J Med . 1998;339:1415-1425.
  10. 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. Brit Med J. 1994;308:81-106.
  11. Jencks SF, Cuerdon T, Burwen DR, et al. Quality of medical care delivered to Medicare beneficiaries: a profile at state and national levels. JAMA. 2000;284:1670-1676.
  12. Goldstein LB, Bonito AJ, Matchar DB, et al. 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.
  13. Dyken ML. Aspirin dose in secondary stroke prevention. Cerebrovascular Dis. 1998;8:361-362.
  14. Grotta JC, Norris JW, Kamm B. Prevention of stroke with ticlopidine: who benefits most? TASS Baseline and Angiographic Data Subgroup. Neurology . 1992;42:111-115.
  15. Rothrock JF, Hart RG. Ticlopidine hydrochloride use and threatened stroke. West J Med . 1994;160:43-47.
  16. Hart RG, Benavente O, McBride R, Pearce LA. Antithrombotic therapy to prevent stroke in patients with atrial fibrillation: a meta-analysis. Ann Intern Med . 1999;131:492-501.
  17. Ad Hoc Committee on Guidelines for the Management of Transient Ischemic Attacks of the Stroke Council for the American Heart Association. Guidelines for the management of transient ischemic attacks. Stroke. 1994;25:1320-1335.
  18. Practice parameter: stroke prevention in patients with nonvalvular atrial fibrillation. Report of the Quality Standards Subcommittee for the American Academy of Neurology. Neurology. 1998;51:671-673.
  19. Laupacis A, Albers G, Dunn M, Feinberg W. Antithrombotic therapy in atrial fibrillation. Chest. 1992;102(4 suppl):426S-433S.
  20. Laupacis A, Albers G, Dalen J, Dunn M, Feinberg W, Jacobson A. Antithrombotic therapy in atrial fibrillation. Chest . 1995;108(4 suppl):352S-359S.
  21. Albers GW, Dalen JE, Laupacis A, Manning WJ, Petersen P, Singer DE. Antithrombotic therapy in atrial fibrillation. Sixth ACCP Consensus Conference on Antithrombotic Therapy. Chest . 2001;119:194S-206S.
  22. White RH, McBurnie MA, Manolio T, et al. Oral anticoagulation in patients with atrial fibrillation: adherence with guidelines in an elderly cohort. Am J Med . 1999;106:165-171.
  23. Brass LM, Krumholz HM, Scinto JM, Radford M. Warfarin use among patients with atrial fibrillation. Stroke . 1997;28:2382-2389.
  24. Stafford RS, Singer DE. National patterns of warfarin use in atrial fibrillation. Arch Intern Med . 1996;156:2537-2546.
  25. Albers GW, Yim JM, Belew KM, et al. Status of antithrombotic therapy for patients with atrial fibrillation in university hospitals. Arch Intern Med . 1996;156:2311-2316.
  26. Antani MR, Beyth RJ, Covinsky KE, et al. Failure to prescribe warfarin to patients with nonrheumatic atrial fibrillation. J Gen Intern Med . 1996;11:713-720.
  27. Atrial Fibrillation Investigators. Risk factors for stroke and efficacy of antithrombotic therapy in atrial fibrillation: analysis of pooled data from five randomized clinical trials. Arch Intern Med . 1994;154:1449-1457.
  28. Stroke Prevention in Atrial Fibrillation Investigators. Risk factors for thromboembolism during aspirin therapy in patients with atrial fibrillation: the Stroke Prevention in Atrial Fibrillation Study. J Stroke Cerebrovasc Dis . 1995;5:147-157.
  29. Patients with nonvalvular atrial fibrillation at low risk of stroke during treatment with aspirin: Stroke Prevention in Atrial Fibrillation III Study. The SPAF III Writing Committee for the Stroke Prevention in Atrial Fibrillation Investigators. JAMA . 1998;279:1273-1277.
  30. Tissue plasminogen activator for acute ischemic stroke. The National Institute of Neurological Disorders and Stroke rt-PA Stroke Study Group. N Engl J Med. 1995;333:1581-1587.
  31. Hacke W, Kaste M, Fieschi C, et al. Intravenous thrombolysis with recombinant tissue plasminogen activator for acute hemispheric stroke. The European Cooperative Acute Stroke Study (ECASS). JAMA . 1995;274:1017-1025.
  32. Hacke W, Kaste M, Fieschi C, et al. Randomised double-blind placebo-controlled trial of thrombolytic therapy with intravenous alteplate in acute ischaemic stroke (ECASS II). Second European-Australasian Acute Stroke Study Investigators. Lancet. 1998;352:1245-1251.
  33. National Stroke Association. Recognizing stroke symptoms. 

Disclaimer

The analyses upon which this article was based were performed under Contract No. 500-99-TX03, entitled "Utilization and Quality Control Peer Review Organization for the State of Texas," sponsored by the Health Care Financing Administration (HCFA), Department of Health and Human Services. The content of this article does not necessarily reflect the view or policies of the Department of Health and Human Services, nor does mention of trade names, commercial products, or organizations imply endorsement by the U.S. government. The authors assume full responsibility for the accuracy and completeness of the ideas presented. This article is a direct result of the Health Care Quality Improvement Program initiated by HCFA, which has encouraged identification of quality improvement projects derived from analysis of patterns of care and, therefore, required no special funding on the part of this contractor. Ideas and contributions to the authors concerning experience in engaging with related issues are welcome.

Table 1. Primary stroke risk factors, American Heart Association Stroke Council, 2001.*

 

 
Modifiable

Nonmodifiable

Well-Documented

Probable

Age: doubling of stroke risk every 10 years after age 55 years

Race: blacks>Hispanic>whites

Sex: men>women

Family history of stroke or transient ischemic attack

Hypertension

Smoking

Diabetes

Asymptomatic carotid stenosis

Sickle cell disease

Hyperlipidemia

Atrial fibrillation

Obesity

Physical inactivity

Alcohol abuse

Hyperhomocysteinemia

Drug abuse

Hypercoagulability

Hormone replacement therapy

Oral contraceptive use

Inflammatory processes

* Reference 6.

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Table 2. Stroke prevention guidelines, American Heart Association Stroke Council, 2001.*

 

Primary Prevention

Secondary Prevention

  1. Hypertension: identify and treat (blood pressure <140/90)
  2. Smoking: cessation
  3. Diabetes: vigorous blood pressure control (blood pressure <130/80)
  4. Asymptomatic carotid artery stenosis: May consider surgery, if associated morbidity and mortality are low (see discussion of varying recommendations in text). 
  5. Atrial fibrillation: warfarin for high-risk
  6. Cholesterol: Statin if LDL >190
  7. Appropriate diet
  8. Regular exercise
  9. Weight reduction, if obese
  10. Avoid excessive alcohol intake
  1. Hypertension: treat to maintain blood pressure <140/90 (<130/80 if diabetic)
  2. Smoking: cessation
  3. Diabetes: tight control (glucose <126)
  4. Carotid artery stenosis: surgery if 70%-99%
  5. Atrial Fibrillation: anitcoagulate with warfarin
  6. Cholesterol: statin if LDL >130
  7. Antiplatelet agents: for atherothrombotic strokes
  8. Appropriate diet
  9. Regular exercise
  10. Avoid excessive alcohol intake

* References 6 and 7.

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  Table 3. American College of Chest Physicians stratification schema for patients with atrial fibrillation.*

 

Classification

Criteria

High risk

Prior stroke or TIA or systemic embolus

Hypertension

Age >75 years

Poor left ventricular systolic function

Rheumatic mitral valve disease

Prosthetic heart valve

>1 moderate risk factor

Moderate risk

Age 65 to 75 years

Diabetes

Coronary artery disease

Low risk

Age <65 years

No evidence of cardiovascular disease or other risk factors

* Reference 21.
TIA = transient ischemic attack

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