The National Stroke Association (NSA) has developed an evidence-based consensus statement on the prevention of a first stroke. Published in the March 24/31, 1999, issue of JAMA, the NSA consensus statement is based on a comprehensive literature review of guidelines, meta-analyses and overviews on the prevention of a first stroke, with the greatest emphasis placed on recommendations from randomized controlled trials and meta-analyses.
Members of the NSA Stroke Prevention Advisory Board, which includes experts from the disciplines of neurology, family practice, cardiology, nursing, physician assistants and health services research, reviewed guidelines from the medical literature and identified areas in the current literature that are different from those in previously published guidelines. According to the NSA, the consensus statement was written with the intent of providing a single source for up-to-date recommendations on prevention of a first stroke.
On the basis of the literature review, the Stroke Prevention Advisory Board identified six important risk factors for stroke: hypertension, myocardial infarction, atrial fibrillation, diabetes mellitus, lipid levels and asymptomatic carotid artery stenosis. The advisory board also identified four risk factors related to lifestyle: smoking, alcohol use, physical activity and diet. The following summarizes the NSA recommendations for the six risk factors (see the accompanying table).
|Hypertension||The Sixth Report of the Joint National Committee on Prevention, Detection, Evaluation and Treatment of High Blood Pressure recommendations for lifestyle modification, initiation of specific therapy and multidisciplinary management strategies.|
|Myocardial infarction||Aspirin therapy if previous myocardial infarction or warfarin at an INR of 2.0 to 3.0 in patients with atrial fibrillation, left ventricular thrombus or significant left ventricular dysfunction; and statin agents after myocardial infarction in patients with normal to high lipid levels.|
|Atrial fibrillation||Patients > 75 years with or without risk factors should be treated with warfarin; patients aged 65 to 75 years with risk factors should be treated with warfarin and those without risk factors should be treated with warfarin or aspirin; patients <65 years with risk factors should be treated with warfarin and those without risk factors should be treated with aspirin.|
|Diabetes mellitus||American Diabetes Association recommendations for control of diabetes to reduce microvascular complications (further studies needed to determine if aggressive glycemic control lowers the risk of stroke).|
|Lipid levels||Statin agents in patients with high cholesterol levels and coronary heart disease and National Cholesterol Education Program guideline principles for dietary and pharmacologic management of patients with hyperlipidemia or atherosclerotic disease.|
|Asymptomatic carotid artery disease||Carotid endarterectomy for asymptomatic carotid stenosis of ≥60 percent (but <100 percent) when surgical morbidity and mortality is <3 percent.|
|Lifestyle factors||Modification of smoking, alcohol consumption, physical activity and diet according to published guidelines.|
INR = International Normalized Ratio.
Reprinted with permission from Gorelick PB, Sacco RL, Smith DB, Alberts M, Mustone-Alexander L, Rader D, et al. Prevention of a first stroke: a review of guidelines and a multidisciplinary consensus statement from the National Stroke Association. JAMA 1999;281:1112–20.
According to the NSA, a systematic overview of 14 prospective randomized controlled trials indicates that a decrease in diastolic blood pressure of 5 to 6 mm Hg reduces the risk for stroke by 42 percent. The NSA recommends the following approaches to help decrease the risk of hypertension-related stroke: (1) control of blood pressure in patients with hypertension, (2) blood pressure measurements in all patients at every office visit and (3) blood pressure monitoring at home by patients with hypertension.
A number of guidelines from various medical organizations recommend oral anticoagulants to prevent ischemic stroke following myocardial infarction. Data show that the incidence of ischemic stroke is approximately 1 to 2 percent per year after a myocardial infarction. The risk is greatest (i.e., 30 percent) in the first month following myocardial infarction. The literature review indicated that an international normalized ratio (INR) of 2.5 to 4.8 may be associated with a 10-fold increase in hemorrhagic stroke. Conversely, an INR below 2.0 may not be effective for the prevention of ischemic stroke. Thus, the NSA recommends an INR in the range of 2.0 to 3.0, with a target goal of 2.5.
According to the NSA statement, evidence in support of the use of antiplatelet agents such as aspirin is not substantial enough to conclude that antiplatelet agents are useful in the prevention of a first stroke after myocardial infarction. While studies by the Antiplatelet Trialists' Collaboration and the North of England Aspirin Guideline Development Group show a reduction in risk, the American College of Physicians reports that the use of antiplatelet agents results in only a small absolute reduction in the risk of stroke.
Current evidence suggests that cholesterol-lowering agents, particularly statin agents, decrease the risk of stroke after myocardial infarction. The NSA supports the recommendation that pravastatin be prescribed in patients with a myocardial infarction and average cholesterol levels of less than 240 mg per dL (6.5 mmol per L) and that simvastatin be used in patients with coronary heart disease and elevated cholesterol levels to prevent stroke or transient ischemic attacks. In patients without coronary heart disease or myocardial infarction but who have had a stroke or other atherosclerotic disease, the NSA recommends following the National Cholesterol Education Program guidelines for initiating dietary or drug therapy for elevated lipid levels.
The NSA Stroke Prevention Advisory Board reviewed four guidelines and consensus statements on the prevention of a first stroke in patients with nonvalvular atrial fibrillation. These guidelines were developed by the American College of Chest Physicians in 1998, the American College of Physicians in 1994, the American Academy of Neurology in 1998 and the American Heart Association in 1996. While there is general agreement among the guidelines that warfarin is indicated in patients with nonvalvular atrial fibrillation and specific risk factors for stroke, not all of the guidelines have the same cutoff for age.
According to the NSA advisory board, the evidence points to the use of warfarin in patients with nonvalvular atrial fibrillation who are at highest risk for stroke, such as those over age 75 or those with specific risk factors such as diabetes, hypertension, previous transient ischemic attack or stroke, or heart failure. However, decisions about antithrombotic and antiplatelet therapy should be individualized, weighing the risk of stroke against the risk of hemorrhage.
According to the NSA consensus statement, studies have not conclusively shown that tight control of serum glucose levels reduces the risk of stroke in patients with diabetes mellitus. However, rigorous control of blood glucose levels are recommended in patients with type 1 (formerly insulin-dependent) and type 2 (formerly non–insulin-dependent) diabetes mellitus to prevent micro-vascular complications.
Asymptomatic Carotid Artery Disease
The NSA advisory board identified 14 guidelines and consensus statements on the prevention of a first stroke in patients with asymptomatic carotid artery disease. In all of the recommendations, the degree of carotid artery stenosis is the key determinant for performing carotid endarterectomy. No guideline supports the use of carotid endarterectomy for asymptomatic lesions in patients with less than 60 percent stenosis or for complete occlusion of the carotid artery.