Secondary Prevention of Ischemic Stroke: Updated Guidelines From AHA/ASA Jan 2022 Flashcards
Key Points for Practice
Stroke is a common source of morbidity and mortality in the United States. Between 20% and 25% of strokes occur in patients with a previous stroke or transient ischemic attack. More than 90% of the global stroke burden can be traced to the modifiable risk factors of blood pressure, diet, physical inactivity, smoking, and abdominal obesity. The American Heart Association and American Stroke Association (AHA/ASA) published updated guidelines for preventing recurrent ischemic stroke, focusing on overall cardiovascular risk reduction and targeted secondary prevention.
- In embolic stroke of an uncertain source, further workup with long-term cardiac monitoring, transesophageal echocardiography, and cardiac magnetic resonance imaging should be considered.
- In nonembolic strokes, antiplatelet therapy and cardiovascular risk reduction can reduce recurrent stroke risk.
- Neither anticoagulation nor antithrombotic therapy appears to reduce risk in embolic stroke of uncertain source.
Stroke Subtype Classification
Ischemic strokes account for nearly 90% of strokes in the United States. The TOAST (Trial of Org 10172 in Acute Stroke Treatment) classification scheme groups ischemic strokes into lacunar or nonlacunar subtypes. Lacunar strokes present with a specific syndrome pattern and can have normal imaging or subcortical ischemic areas less than 0.6 in (1.5 cm) in diameter.
Nonlacunar strokes can be caused by cardioembolism, large artery atherosclerosis, and cryptogenic sources. Cardioembolic sources are suggested when previous or current ischemia occurs in multiple vascular territories. Large artery atherosclerotic lesions may present with cortical, brainstem, cerebellar, or larger subcortical areas of ischemia. Cryptogenic strokes defy characterization despite complete evaluations and again subdivide into embolic or nonembolic strokes of uncertain source. Embolic strokes of an uncertain source are nonlacunar and appear embolic, but no source of embolus can be identified. Figure 1 details the relative frequency of different stroke subtypes.
Diagnostic Evaluation
After a stroke, the subtype can usually be determined from initial testing, including computed tomography, magnetic resonance imaging, electrocardiography, continuous cardiovascular monitoring, echocardiography, and laboratory analyses. When initial imaging does not show ischemia after a stroke, imaging can be repeated seven days after the index event to look for ischemic changes.
Extracranial carotid imaging and contrast imaging studies can be performed with the initial evaluation. Carotid imaging is vital for strokes affecting the anterior circulation, and vertebrobasilar imaging is recommended for strokes outside of the anterior circulation.
For cryptogenic stroke without a suspected embolic source, testing for hypercoagulation and vasculitis should be considered. If an embolic source is suspected, further testing with long-term or implantable cardiac rhythm monitoring, transesophageal echocardiography, or cardiac magnetic resonance imaging is recommended. In embolic strokes of an uncertain source, findings from transesophageal echocardiography will change management in 14% of patients. Up to 16% of patients with embolic strokes of an uncertain source will have paroxysmal atrial fibrillation identified with prolonged cardiac monitoring. Evidence is insufficient to recommend a specific prolonged cardiac monitoring strategy for these patients.
Secondary Cardiovascular Prevention
Secondary stroke prevention includes cardiovascular risk reduction, as shown in Table 1. AHA/ASA guidelines recommend a blood pressure treatment goal of less than 130/80 mm Hg after all strokes and low-density lipoprotein cholesterol goals of less than 70 mg per dL (1.81 mmol per L) for nonembolic strokes. If triglycerides are greater than 135 mg per dL (1.53 mmol per L) in nonembolic strokes, adding icosapent ethyl can reduce the risk of current stroke but increase the risk of atrial fibrillation. A Mediterranean-type diet is the primary dietary recommendation, and limiting salt to 2.5 g daily is reasonable. AHA/ASA recommends at least four weekly 10-minute periods of moderate-intensity physical activity or two high-intensity 20-minute periods. Smoking cessation is strongly recommended, and alcohol cessation or reduction to no more than two drinks per day for men and no more than one per day for women is recommended.
Stroke-Specific Secondary Prevention
Antithrombotic therapy recommendations after a stroke depend on the stroke subtype and complicating conditions. In patients with stroke secondary to atrial fibrillation, direct-acting oral anticoagulants are preferred unless atrial fibrillation is complicated by moderate or severe mitral stenosis or a mechanical heart valve. Patients with minor nonembolic strokes and high-risk transient ischemic attacks should receive dual antiplatelet therapy with aspirin and clopidogrel (Plavix) for 21 to 90 days, followed by continued treatment with either medication alone. Although antiplatelet therapy reduces recurrent stroke after all nonembolic strokes, embolic strokes of an uncertain source do not appear to benefit from antiplatelet or anticoagulant therapy.
Carotid endarterectomy is beneficial after stroke when ipsilateral extracranial internal carotid stenosis is 70% or greater. Endarterectomy is reasonable with ipsilateral stenosis of 50% to 69% in patients who are at lower surgical risk. Carotid artery stenting may be a reasonable alternative to endarterectomy in certain low-risk patients.
When a patent foramen ovale is found after an embolic stroke of an uncertain source in an adult up to 60 years of age, closure may be beneficial if an exhaustive workup has been performed. Evaluation may include intracranial contrast imaging, advanced cardiac imaging, lower extremity venous ultrasonography, prolonged cardiovascular rhythm monitoring, and evaluation for infective endocarditis, hypercoagulable syndromes, antiphospholipid syndromes, and vasculitis syndromes. If the stroke is still unexplained, small trials suggest benefit from foramen ovale closure, especially with an atrial septal aneurysm or large right-to-left shunting.
Behavioral Interventions
Behavioral change interventions focusing on health and stroke literacy, lifestyle risk factors, and adherence to therapeutic strategies decrease stroke recurrence.
The views expressed are those of the authors and do not necessarily reflect the official policy or position of the Department of the Navy, Uniformed Services University of the Health Sciences, Department of Defense, or the U.S. government.
Editor’s Note: The key changes to this AHA/ASA guideline update are new recommendations for diagnostic workup after ischemic stroke and grouping of recommendations by ischemic stroke type. Angioplasty and stenting of intracranial lesions are no longer recommended, with aggressive medical management recommended instead. Closure of a patent foramen ovale is now an option in younger patients with nonlacunar stroke after a negative extended evaluation. Only anticoagulants and ticagrelor have been studied after embolic strokes of an uncertain source, and neither appears to reduce rates of recurrent stroke.
The recommendation for icosapent ethyl is controversial because benefit was demonstrated in a single trial with possible flaws, as discussed in a previous dyslipidemia guideline summary. (https://www.aafp.org/afp/2021/0415/p507.html). A subsequent large trial failed to show any benefit of icosapent ethyl, making this recommendation more questionable.1
The most recent AFP article on recurrent stroke prevention (https://www.aafp.org/afp/2017/1001/p436.html) was based on the 2015 AHA/ASA guideline.—Michael J. Arnold, MD, Contributing Editor
