Secondary Stroke Prevention of Among People With TIA and Stroke
The principle aims in treating stroke are three-fold: (1) to reopen an occluded cerebral artery (thrombolysis), (2) to provide protection against the metabolic cascade caused by ischemic injury leading to neuronal death (neuroprotection), and (3) to prevent recurrent stroke (secondary prevention). Secondary prevention of stroke is the most important of these three since neither thrombolysis nor neuroprotection are currently practical in the majority of patients
Blood Pressure Reduction
Among the 12,000 people who have had previous TIA or stroke (in a population of 1 million people), about 6,000 (50%) have hypertension.Lowering the blood pressure of these 6000 hypertensive TLA/stroke patients by 5-6 mm Hg diastolic and 10-12 mm Hg systolic for two to three years would reduce the annual incidence of stroke in these people from about 7% (n = 420 strokes) to 4.8% (n = 288) (relative risk reduction: 28%, 95% CI: 15%–39%),53 assuming they have the same rate of stroke as individuals who do not have hypertension .This reduction of about 132 strokes per year is 6.6% all (2000) strokes occurring in the population each year. Treating 45 hypertensive TLA/stroke patients for one year (at least) would avoid one stroke each year.
Cigarette Smoking
About 30% (3,600) of TIA/stroke patients are cigarette smokers. Although there have been no randomized trials, observational studies suggest that if all 3,600 TIA/stroke patients who smoke were to stop smoking, the annual number of strokes could be reduced by at least one-third, from about 7% (252) to 4.7% (169), avoiding about 83 strokes each year (4.1% of all strokes). This means that 43 people with TIA/stroke need to stop smoking avoid one stroke of any type each year.
Aids to stop smoking may be required, such as counseling, nicotine gum, or skin patches.
Cholesterol Reduction
TIA/stroke patients, trials in different patient populations suggest that lowering serum cholesterol over a few years years with hydroxymethylglutaryl coenzyme A reductase inhibitors (or “statin†drugs) could reduce the number of strokes by about 24% (95% CI: 8% to 38%), from 7% (336) to 5.3% (255) per year. This reduction, of about 81 strokes, would be 3.4% all (2000) strokes in the population each year. About 59 TIA/stroke patients with hypercholesterolemia would need to be treated effectively avoid one stroke each year.
Antiplatelet Therapy
Antiplatelet therapy is appropriate for about 75% (7875) of people with TIA (2000) or ischemic stroke (8,500) and, if given to all, could reduce the annual incidence of stroke from about 7% (551) to 5.8% (457), thus avoiding about 94 strokes each year (4.7% of all strokes). Treating 83 TIA/ischemic stroke patients for one year (at least) would avoid one each year.
Besides clopidogrel, no single antiplatelet agent exists that is more effective than aspirin. Aspirin reduces the risk of important vascular events by about 13% from about 7.0% (551) to 6.0% (472), thus avoiding 79 strokes each year (4.0% of all strokes). Clopidogrel reduces the risk important vascular events by 8.7% (95%CI: 0.3% to 16.5%) compared aspirin, indicating that it would further reduce the risk from 6.0% (472) to 5.5% (433), thus avoiding about 39 more strokes each year, and 118 strokes compared with control.
The combination of dipyridamole and aspirin may also be more effective than aspirin alone. The addition of the second European Stroke Prevention Study (ESPS-2) to four previous studies that had compared the combination of aspirin and dipyridamole with aspirin alone reveals that the combination of aspirin and dipyridamole is associated with about a 15% relative risk reduction compared with aspirin alone.If these results can be confirmed in ongoing trials (e.g., ESPRIT), and the 7875 people with TIA/stroke take the combination of aspirin and dipyridamole for at least a year, the total number of strokes each year could be reduced from 6.0% (472) to 5.1% (402), thus avoiding about 70 more strokes each year than aspirin alone, and 188 strokes compared with control. One hundred patients need to be treated with aspirin, 66 with clopidogrel, and 53 aspirin plus dipyridamole for at least one year to avoid stroke each year.
Anticoagulant Therapy
Oral anticoagulant therapy (INR 2.0 to 3.0) is indicated for about 20% (2100) of patients with TIA/ischemic stroke who have high-risk sources of embolism from the heart to the brain. Treating these 2100 people with oral anticoagulants would reduce the number of strokes each year by about two-thirds, from 12% (252) to 4% (84),thus avoiding 168 strokes each year (8.4% of all strokes). About 12 people with TIA/stroke and a potential cardiac source of embolism need to be treated with oral anticoagulants for one year prevent one stroke each year.
CE for Symptomatic Carotid Stenosis
CE is indicated for individuals who have had recent symptoms of carotid territory TIA or mild ischemic stroke, severe (>70% in NASCET, >80% ECST) carotid stenosis, and who are fit and willing for surgery. Only about 8% (816) of TIA/ischemic stroke patients meet these criteria.If all 816 appropriate TIA/stroke patients undergo CE, the three-year risk of major stroke or death could be reduced from about 26.5% (8.8% per year) to 14.9% (5.0% year). This is an average absolute risk reduction of 3.8% per year, which equates to about 31 strokes prevented each year (1.5% of all strokes) by performing CE on 816 patients. At least 26 patients would need to be treated with CE to avoid one stroke per year. The number needed to treat prevent one stroke is higher if the perioperative risk of major stroke or death is higher than about 7%.
CE for Asymptomatic Carotid Stenosis
About 10,000 (1%) people in the population (4% of the aged 50–75 years) have asymptomatic carotid stenosis of 60%–99%.47 If these 10,000 people are accurately identified and undergo CE, the number of strokes could be reduced
from 11% (1100) at five years to 5% (500),thus avoiding up to 600 strokes over five years, or 120 strokes per year (6% of all strokes).
Carotid Angioplasty and Stenting
Carotid angioplasty and stenting is a promising but currently experimental procedure that is in duced from 11% (1100) at five years to 5% trial.
Summary of the Potential Impact of the Different Strategies of Secondary Stroke Prevention for TIA and Stroke Patients on Stroke Prevention in the Population | ||||||||||||||||||
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(John W. Norris M.D.-Vladimir Hachinski M.D.)
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