Prevention of Ischemic Stroke

Introduction

Stroke is well suited for prevention as it has a high prevalence, a number of modifiable factors proven to reduce stroke risk, and a high societal economic and disability burden . An international observational study, INTERSTROKE, showed that 10 relatively common factors are associated with about 90% of stroke risk . Hypertension accounted for almost 35% of the risk. Approaches to stroke prevention include the “high-risk” and “mass” approaches . The latter approach aims to reduce risk in a population through health education, legislation, and economic measures to decrease exposure to risks in a broad manner. On the other hand, the high-risk approach is designed to screen for persons at high risk of stroke, for example, and then aggressively manage the risks which may require not only education and lifestyle modification, but also administration of medication . As an example, the high-risk approach is applied by health care providers in office practice to select out persons for treatment with medication to lower risk. The mass and high-risk approaches are viewed as complementary means to reduce occurrence of stroke. Furthermore, we have learned over time with advancement and sophistication of clinical trials in stroke prevention that identification of stroke mechanism is important as a springboard to application of evidence-based efficacious and safe stroke prevention practices.

In this chapter we discuss ischemic stroke prevention in relation to first and recurrent stroke prevention. While worldwide there are a number of important guidelines for first and recurrent ischemic stroke prevention, based on limitations in the scope of this chapter we have chosen to review the most recent first and recurrent ischemic stroke prevention guidelines from the American Heart Association/American Stroke Association (AHA/ASA) . For the sake of simplicity and clarity of discussion, AHA/ASA stroke prevention guidelines refer to three categories of stroke risk factors: generally nonmodifiable ones (e.g., age, low birth weight, race/ethnicity, and genetic factors); well-documented and modifiable risk factors (e.g., physical activity, dyslipidemia, diet and nutrition, raised blood pressure, obesity, diabetes mellitus, cigarette smoking, atrial fibrillation and other cardiac conditions, and carotid and intracranial artery stenosis); and less well-documented or potentially modifiable factors (e.g., migraine, metabolic syndrome, alcohol consumption, and sleep-disordered breathing) .

The topical discussions that follow are divided into the following key categories in relation to first and recurrent ischemic stroke prevention: (1) management of lifestyle and modifiable vascular risks; and (2) indications for aspirin and other antiplatelet medications, oral anticoagulants, closure of patent foramen ovale (PFO) and left atrial appendage device occlusion, carotid endarterectomy (CEA) and angioplasty/stenting, and extracranial to intracranial arterial bypass. Finally, determination of risk for atherosclerotic cardiovascular diseases (ASCVD), such as stroke, is deemed useful at the individual patient level. The reader is referred elsewhere for a more detailed discussion of risk prediction in ASCVD and stroke .

AHA/ASA Guideline Recommendations for Management of Lifestyle and Vascular Risks for Ischemic Stroke Prevention

Based on similarities in management of lifestyle and vascular risks for first and recurrent ischemic stroke, we discuss AHA/ASA guideline recommendations primarily from the viewpoint of first stroke prevention . We provide additional comments when there is a difference in lifestyle or vascular risk management recommendations between first and recurrent ischemic stroke prevention .

Lifestyle Factors

For healthy adults moderate to vigorous-intensity aerobic physical activity at least 40 min per day, 3–4 days per week is recommended . The recommendation is similar for recurrent ischemic stroke prevention; however, for those who cannot readily engage in physical activity due to stroke impairment or disability, a structured exercise program developed by a health care professional, such as a physiatrist or other rehabilitation specialist, may be helpful . In relation to diet and nutrition , the Mediterranean diet supplemented with nuts may be considered , which is similar to guidance for recurrent ischemic stroke prevention . In addition, reduction of intake in sodium to help lower blood pressure (e.g., 2.4 g/day or less [<1.5 g/day]) and a DASH diet are recommended as good options . Smoking cessation is recommended as is avoidance of passive smoke. Counseling, nicotine replacement therapy, and other medications (e.g., bupropion and varenicline) also may be useful . Weight reduction for those who are overweight or obese is indicated to lower blood pressure, and therefore, reduce stroke risk . Although screening for weight and determination of body mass index (BMI) is recommended, the usefulness of weight loss is uncertain in relation to recurrent stroke prevention . For alcohol consumption , there is counseling to attempt to eliminate heavy drinking, and if one does drink, the aim is for ≤2 standard drinks/day for men and up to one standard drink/day for nonpregnant women .

Well- and Less Well-documented Vascular Risk Factors

Hypertension

As referred to earlier, hypertension is the most important modifiable risk factor for stroke. AHA/ASA stroke prevention guidance now calls for regular blood pressure (BP) screening and lifestyle modification and pharmacological management . Prehypertensive persons (i.e., systolic BP (SBP) 120–139 mm Hg or diastolic BP (DBP) 80–89 mm Hg) should be screened annually. Currently, the BP target for treatment is <140/90 mm Hg, and BP lowering is considered more important than specific class of BP medication, though there may be compelling indications for administration of certain classes of BP-lowering medication . Finally, self-measurement of BP is recommended to enhance BP control. In relation to recurrent ischemic stroke prevention, the target is similar to that for primary stroke prevention (<140/90 mm Hg) with the exception of recent lacunar infarction whereby a reasonable target is a SBP <130 mm Hg .

Dyslipidemia

Based on national guidelines in the United States, statin therapy is indicated for primary prevention of ASCVD including stroke in persons with a 10-year risk ≥7.5% or for those with other indications (e.g., having clinical ASCVD, elevation of LDL-C ≥190 mg/dL, and persons aged 40–75 years with an LDL-C 70–189 mg/dL and a history of diabetes mellitus) . Recommendations for recurrent stroke prevention state that those with ischemic stroke or transient ischemic attack (TIA) of atherosclerotic origin and an LDL-C level ≥100 mg/dL should receive a statin agent . Furthermore, according to the primary stroke prevention guideline, potent statin-lowering drugs are indicated though a specific target LDL-C goal is not emphasized, whereas, in the recurrent stroke prevention guideline an LDL-C target is specified at a level of <100 mg/dL and optimally at 50–70 mg/dL or 50% of the pretreatment LDL-C value .

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