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Chapter 1 Prevention and Treatment of Ischemic Stroke: A Practical Perspective
1 Prevention and Treatment of Ischemic Stroke: A Practical Perspective Scott E. Kasner and Philip B. Gorelick
DEFINITIONS Stroke remains a broadly defined term, which includes ischemic stroke, intracerebral hemorrhage, subarachnoid hemorrhage, and cerebral venous thrombosis. This volume addresses only ischemic stroke. Ischemic stroke can be subclassified in many ways; one widely used system defines five major stroke subtypes according to the etiological mechanism: large-vessel atherothromboembolism, cardioembolism, small-vessel occlusive disease, nonatherosclerotic unusual causes of stroke, and cryptogenic (i.e., infarct of unknown cause) stroke.1 The first three of these account for the vast majority (up to 90%) of all ischemic strokes and are therefore the major thrust of this volume.
EPIDEMIOLOGY In the United States, it is estimated that there are approximately 600,000 to 750,000 strokes annually, of which 80 to 85 percent are ischemic.2,3 Stroke ranks third among causes of death and first among causes of long-term disability. Nearly 25 percent of people who have a stroke will die within a year, and another 15 to 30 percent will be permanently disabled. Given the high incidence and mortality of stroke, it should be apparent that interventions with relatively small incremental benefit may affect a large number of people. Furthermore, the incidence of stroke increases with age, roughly doubling every 5 to 10 years beyond age 55,2 and therefore stroke poses an increasing burden on the public health system as the population ages. Stroke risk is also higher in people of African and some of Hispanic origin. Although age, sex, race, and ethnicity are nonmodifiable, these factors should call attention to those people for whom 1
2
Prevention and Treatment of Ischemic Stroke
aggressive prevention measures and care are needed to minimize the risk and the complications of stroke.
PREVENTION OF ISCHEMIC STROKE Stroke prevention may be targeted at two basic levels: the “mass approach” for the population at large and the “high-risk approach” for those in the population who are believed to be at greater risk.4 Stroke-preventive strategies may be further conceptualized as being stratified into two major categories: generic or mechanism-specific. Generic prevention relates to the management of the modifiable vascular risk factors, such as hypertension, diabetes mellitus, lipid disorders, smoking, and so forth, all of which may cause injury to the large and small cerebral blood vessels and the coronary and peripheral arteries, regardless of the specific causes of stroke. Generic primary prevention is addressed in Chapter 2, whereas secondary prevention is addressed in Chapters 9 and 10. Mechanism-specific prevention addresses specific causes, such as carotid artery stenosis or atrial fibrillation, but does not address the systemic processes of atherosclerosis or other cardiovascular injury. Consequently, these mechanism-specific interventions require appropriate diagnosis of the proximate cause of stroke. The etiologies and mechanisms of stroke are defined further in Chapter 3, the diagnostic techniques are summarized in Chapter 4, and the mechanism-specific preventative strategies are discussed in Chapters 5 through 8.
ACUTE STROKE DIAGNOSIS AND TREATMENT Treatment of acute stroke has been transformed by the advent of thrombolytic therapy. Newer therapies also appear on the horizon, but the overwhelming evidence supports the “time is brain” tenet and suggests that early intervention is needed for any therapy to improve outcome. Consequently, rapid diagnosis is needed, and the clinical and radiological tools for evaluation are evolving accordingly. The traditional approach has consisted of general physical and neurological examinations, a computed tomography (CT) of the brain, and a few basic blood tests, but these may be improved on. Chapters 11 and 12 describe these methods and newer approaches that provide a framework for expedited diagnosis and initiation of acute stroke therapies. In patients who are eligible, thrombolysis can improve outcome, but it is associated with a risk of hemorrhagic complications. This risk can be minimized with careful adherence to standard protocols. Chapter 13 describes the state-of-the-art approach to thrombolysis and the relevant considerations in clinical practice. For those who do not receive thrombolysis, antiplatelet agents and possibly anticoagulant medications remain the mainstay of early stroke therapy for most patients. The evidence for and against the use of these agents is summarized in Chapter 14. Emerging therapies, although not fully tested, provide promise for alternatives to existing therapy and the possibilities of multimodal or combination therapy. These novel putative treatments are described in Chapter 15.
Prevention and Treatment of Ischemic Stroke: A Practical Perspective
3
Primary prevention (stroke-free population) Acute ischemic stroke Acute therapy and supportive care Rapid diagnosis
Rehabilitation and recovery Determination of stroke etiology
Secondary prevention
Time
Figure 1.1 The continuum of stroke care. Primary prevention measures are implemented in the healthy stroke-free population to limit the risk of stroke (upper bar). If an acute stroke occurs, several issues must be implemented in parallel (lower bars): treatment (acute therapy and supportive care, followed by rehabilitation), diagnostic evaluation (initial rapid diagnosis followed by determination of etiology), and secondary prevention (which ultimately depends on both etiology and recovery).
In the days to weeks after stroke, patients are at risk of suffering from a host of medical and neurological complications, many of which are preventable and can worsen the outcome of the stroke. Many of these basic issues have been rigorously evaluated in recent years, and Chapters 16 to 18 offer guidelines about how to organize and implement supportive care of the stroke patient to prevent and treat these complications. Finally, patients with neurological deficits and disability may improve after their initial hospital-based treatment. Rehabilitation of the stroke patient and advances in this field are outlined in Chapter 19.
THE CONTINUUM OF STROKE CARE Effective prevention and treatment of stroke require a comprehensive approach to each and every patient and span the full continuum of care (Figure 1.1). Clinical research has yielded a wealth of information to guide us in these efforts, and it is our hope that this text will help clinicians at all levels to transform evidence into clinical reality.
References 1. Adams HP, Bendixen BH, Kappelle LJ, et al. Classification of subtype of acute ischemic stroke. Definitions for use in a multicenter clinical trial. Stroke 1993;24:35–41. 2. Wolf PA, D’Agostino RB. Epidemiology of Stroke. In HJM Barnett, JP Mohr, BM Stein, FM Yatsu (eds), Stroke: Pathophysiology, Diagnosis, and Management (3rd ed). New York: Churchill Livingstone, 1998;3–28. 3. Broderick J, Brott T, Kothari R, et al. The Greater Cincinnati/Northern Kentucky Stroke Study: preliminary first-ever and total incidence rates of stroke among blacks. Stroke 1998;29:415–421. 4. Gorelick PB. Community Mass and High Risk Strategies. In PB Gorelick, MA Alter (eds), The Prevention of Stroke. New York: Parthenon, 2002;115–121.
DEFINITIONS Stroke remains a broadly defined term, which includes ischemic stroke, intracerebral hemorrhage, subarachnoid hemorrhage, and cerebral venous thrombosis. This volume addresses only ischemic stroke. Ischemic stroke can be subclassified in many ways; one widely used system defines five major stroke subtypes according to the etiological mechanism: large-vessel atherothromboembolism, cardioembolism, small-vessel occlusive disease, nonatherosclerotic unusual causes of stroke, and cryptogenic (i.e., infarct of unknown cause) stroke.1 The first three of these account for the vast majority (up to 90%) of all ischemic strokes and are therefore the major thrust of this volume.
EPIDEMIOLOGY In the United States, it is estimated that there are approximately 600,000 to 750,000 strokes annually, of which 80 to 85 percent are ischemic.2,3 Stroke ranks third among causes of death and first among causes of long-term disability. Nearly 25 percent of people who have a stroke will die within a year, and another 15 to 30 percent will be permanently disabled. Given the high incidence and mortality of stroke, it should be apparent that interventions with relatively small incremental benefit may affect a large number of people. Furthermore, the incidence of stroke increases with age, roughly doubling every 5 to 10 years beyond age 55,2 and therefore stroke poses an increasing burden on the public health system as the population ages. Stroke risk is also higher in people of African and some of Hispanic origin. Although age, sex, race, and ethnicity are nonmodifiable, these factors should call attention to those people for whom 1
2
Prevention and Treatment of Ischemic Stroke
aggressive prevention measures and care are needed to minimize the risk and the complications of stroke.
PREVENTION OF ISCHEMIC STROKE Stroke prevention may be targeted at two basic levels: the “mass approach” for the population at large and the “high-risk approach” for those in the population who are believed to be at greater risk.4 Stroke-preventive strategies may be further conceptualized as being stratified into two major categories: generic or mechanism-specific. Generic prevention relates to the management of the modifiable vascular risk factors, such as hypertension, diabetes mellitus, lipid disorders, smoking, and so forth, all of which may cause injury to the large and small cerebral blood vessels and the coronary and peripheral arteries, regardless of the specific causes of stroke. Generic primary prevention is addressed in Chapter 2, whereas secondary prevention is addressed in Chapters 9 and 10. Mechanism-specific prevention addresses specific causes, such as carotid artery stenosis or atrial fibrillation, but does not address the systemic processes of atherosclerosis or other cardiovascular injury. Consequently, these mechanism-specific interventions require appropriate diagnosis of the proximate cause of stroke. The etiologies and mechanisms of stroke are defined further in Chapter 3, the diagnostic techniques are summarized in Chapter 4, and the mechanism-specific preventative strategies are discussed in Chapters 5 through 8.
ACUTE STROKE DIAGNOSIS AND TREATMENT Treatment of acute stroke has been transformed by the advent of thrombolytic therapy. Newer therapies also appear on the horizon, but the overwhelming evidence supports the “time is brain” tenet and suggests that early intervention is needed for any therapy to improve outcome. Consequently, rapid diagnosis is needed, and the clinical and radiological tools for evaluation are evolving accordingly. The traditional approach has consisted of general physical and neurological examinations, a computed tomography (CT) of the brain, and a few basic blood tests, but these may be improved on. Chapters 11 and 12 describe these methods and newer approaches that provide a framework for expedited diagnosis and initiation of acute stroke therapies. In patients who are eligible, thrombolysis can improve outcome, but it is associated with a risk of hemorrhagic complications. This risk can be minimized with careful adherence to standard protocols. Chapter 13 describes the state-of-the-art approach to thrombolysis and the relevant considerations in clinical practice. For those who do not receive thrombolysis, antiplatelet agents and possibly anticoagulant medications remain the mainstay of early stroke therapy for most patients. The evidence for and against the use of these agents is summarized in Chapter 14. Emerging therapies, although not fully tested, provide promise for alternatives to existing therapy and the possibilities of multimodal or combination therapy. These novel putative treatments are described in Chapter 15.
Prevention and Treatment of Ischemic Stroke: A Practical Perspective
3
Primary prevention (stroke-free population) Acute ischemic stroke Acute therapy and supportive care Rapid diagnosis
Rehabilitation and recovery Determination of stroke etiology
Secondary prevention
Time
Figure 1.1 The continuum of stroke care. Primary prevention measures are implemented in the healthy stroke-free population to limit the risk of stroke (upper bar). If an acute stroke occurs, several issues must be implemented in parallel (lower bars): treatment (acute therapy and supportive care, followed by rehabilitation), diagnostic evaluation (initial rapid diagnosis followed by determination of etiology), and secondary prevention (which ultimately depends on both etiology and recovery).
In the days to weeks after stroke, patients are at risk of suffering from a host of medical and neurological complications, many of which are preventable and can worsen the outcome of the stroke. Many of these basic issues have been rigorously evaluated in recent years, and Chapters 16 to 18 offer guidelines about how to organize and implement supportive care of the stroke patient to prevent and treat these complications. Finally, patients with neurological deficits and disability may improve after their initial hospital-based treatment. Rehabilitation of the stroke patient and advances in this field are outlined in Chapter 19.
THE CONTINUUM OF STROKE CARE Effective prevention and treatment of stroke require a comprehensive approach to each and every patient and span the full continuum of care (Figure 1.1). Clinical research has yielded a wealth of information to guide us in these efforts, and it is our hope that this text will help clinicians at all levels to transform evidence into clinical reality.
References 1. Adams HP, Bendixen BH, Kappelle LJ, et al. Classification of subtype of acute ischemic stroke. Definitions for use in a multicenter clinical trial. Stroke 1993;24:35–41. 2. Wolf PA, D’Agostino RB. Epidemiology of Stroke. In HJM Barnett, JP Mohr, BM Stein, FM Yatsu (eds), Stroke: Pathophysiology, Diagnosis, and Management (3rd ed). New York: Churchill Livingstone, 1998;3–28. 3. Broderick J, Brott T, Kothari R, et al. The Greater Cincinnati/Northern Kentucky Stroke Study: preliminary first-ever and total incidence rates of stroke among blacks. Stroke 1998;29:415–421. 4. Gorelick PB. Community Mass and High Risk Strategies. In PB Gorelick, MA Alter (eds), The Prevention of Stroke. New York: Parthenon, 2002;115–121.