Antithrombotic Secondary Prevention After Stroke

Platelets as Predictors of Vascular Risk: Is There a Practical Index of Platelet Activity?

Activated platelets play a role in the pathogenesis of coronary heart disease (CHD). Following activation, platelets change shape, aggregate, and release several bioactive substances. The aim of this review is to identify if there is a simple and cost-effective method that indicates platelet activation and predicts the risk of CHD and vascular events. The rationale for identifying high-risk patients is to reduce their risk of vascular events by administering appropriate and effective antiplatelet treatment, like aspirin, clopidogrel, or combination regimens. Many laboratory tests estimating platelet activity have been described. Some are relatively simple, such as spontaneous or agonist-induced platelet aggregation. Other tests include measuring the mean platelet volume (MPV) or plasma soluble P-selectin levels. Some more complex tests include flow cytometry to determine platelet GP Ilb/Illa receptors, platelet surface P-selectin, plateletmonocyte aggregates, and microparticles. Only few prospective studies assessed the predictive value of platelet activation in healthy individuals. Although the MPV seems an 'easy method, there are insufficient data supporting its ability to predict the risk of a vascular event in healthy adults. Platelet aggregation, in whole blood or in platelet-rich plasma was not consistently predictive of vascular risk. Soluble P-selectin measurement is a promising method but it needs further evaluation. Flow cytometry methods are costly, time-consuming, and need specialized equipment. Thus, they are unlikely to be useful in estimating the risk in large numbers of patients. There is as yet no ideal test for the detection of platelet activation. Each currently available test has merits and disadvantages. Simple methods such as the MPV and the determination of platelet release products need further evaluation.

Low-dose acetylsalicylic acid analog and acetazolamide for prevention of acute mountain sickness

Analgesic drugs like acetylsalicylic acid, paracetamol, and ibuprofen are frequently used by subjects suffering from headache of acute mountain sickness (AMS). It is not clear if the effect is due to analgesia or prevention of AMS. We performed a randomized controlled clinical trial comparing a low dose of an acetylsalicylic acid analog, calcium carbasalate (380 mg /day), to placebo in a cohort of altitude-naïve subjects attempting a fast climb of Mt. Kilimanjaro (5896 m). A third noncontrolled open arm was proposed-the usual recommended preventive treatment of acetazolamide 500 mg/day. Of 93 potential participants, 44 chose prevention with acetazolamide, 18 refused participation, 15 received calcium carbasalate, and 16 received placebo. Mean age was 39 +/- 9 (SD) yr and 15% were female. AMS was quantified by the Lake Louise Symptom Score and physician assessment. Calcium carbasalate at 380 mg/day did not have any preventive effect on AMS and did not have any effect on the prevalence and intensity of headache. Event rate of AMS in the pooled carbasalate-placebo group was 84% and 55% in the acetazolamide group. The number needed to treat (NNT) at 500 mg/day of acetazolamide was 3. One subject on acetazolamide developed high altitude cerebral edema and was treated with dexamethasone, oxygen, and descent by evacuation. In conclusion, low-dose calcium carbasalate is not effective for prevention of AMS. In addition, these results corroborate the contention that in typical steep climbing profile settings, such as used by commercial enterprise on Mt. Kilimanjaro, acetazolamide 500 mg/day may not be sufficient to prevent AMS or to sufficiently reduce symptom intensity in almost half of subjects.

Prevalence of antiplatelet therapy in patients with diabetes

Objective

To determine the prevalence of, and patient characteristics associated with, antiplatelet therapy in a cohort of primary care patients with Type 1 or Type2 diabetes.

Methods

Subjects participating in a randomized trial of a decision support system were interviewed at home and medication usage verified by a research assistant. Eligibility for antiplatelet therapy was determined by American Diabetes Association criteria and clinical contraindications. The association between antiplatelet use and patient characteristics was examined using bivariate and multivariate logistic regression.

Results

The mean age of subjects was 64 years (range 31–93). The prevalence of antiplatelet use was 54% overall; 45% for subjects without known CVD vs. 78% for those with CVD; 46% for women vs. 63% for men; and 45% for younger subjects (age< 65) vs. 62% for senior citizens. After controlling for race/ethnicity, income, education, marital status, insurance status and prescription coverage, the following were associated with the use of antiplatelet therapy: presence of known CVD (OR 3.4 [2.2, 5.1]), male sex (OR 2.0 [1.4, 2.8]), and age > = 65 (OR 1.9 [1.3, 2.7]). The prevalence of antiplatelet therapy for younger women without CVD was 32.8% compared to a prevalence of 90.3% for older men with CVD.

Conclusion

Despite clinical practice guidelines recommending antiplatelet therapy for patients with diabetes, there are still many eligible patients not receiving this beneficial therapy, particularly patients under 65, women, and patients without known CVD. Effective methods to increase antiplatelet use should be considered at the national, community, practice and provider level.

Efficacy and costs of secondary prevention with antiplatelets after ischaemic stroke

Ischaemic stroke and other atherothrombotic events substantially increase the medico-economic burden because of their high treatment costs and long-lasting disabilities with need for chronic care. Studies have shown that the cost of stroke represents approximately 3 - 5% of the annual health budget. Antiplatelet agents play a major role in secondary stroke prevention. Acetylsalicylic acid (ASA), ASA combined with extended-release dipyridamole (ER-Dip), and clopidogrel are all acceptable choices for first-line treatment in the secondary prevention of stroke. The newer antiplatelets, however, are more expensive than ASA, and their cost-effectiveness is not easily estimated. ASA has to be given to 33 stroke patients to prevent one future stroke, myocardial infarction (MI) or vascular death compared with placebo. Adding ER-Dip to ASA increases the benefit for the patients. A total of 33 stroke patients had to be treated with this combination, instead of ASA, to prevent one stroke. However, the combination of ASA plus ER-Dip does not prevent MI, vascular death or the combined end point of either stroke or death. Clopidogrel is more effective than ASA in preventing a combined end point of ischaemic stroke, MI, or vascular death, but it has not been shown to be superior to ASA in preventing recurrent stroke in transient ischaemic attack or stroke patients. Several subgroups, such as stroke patients with additional peripheral artery disease, patients with prior coronary artery bypass, patients with insulin-dependent diabetes, and patients with recurrent vascular events, were identified, in whom the benefit of clopidogrel is amplified. Taking economical aspects into account, the fixed combination of ASA and ER-Dip can be recommended for secondary stroke prevention as a first-line alternative to ASA in patients without major comorbidity. In patients with higher comorbidity, clopidogrel may be more effective for the individual patient compared with ASA, and might also be cost-effective. Furthermore, in patients with ASA intolerance clopidogrel is a useful, but expensive, alternative.

IGF-I activity may be a key determinant of stroke risk--a cautionary lesson for vegans

IGF-I acts on vascular endothelium to activate nitric oxide synthase, thereby promoting vascular health; there is reason to believe that this protection is especially crucial to the cerebral vasculature, helping to ward off thrombotic strokes. IGF-I may also promote the structural integrity of cerebral arteries, thereby offering protection from hemorrhagic stroke. These considerations may help to explain why tallness is associated with low stroke risk, whereas growth hormone deficiency increases stroke risk--and why age-adjusted stroke mortality has been exceptionally high in rural Asians eating quasi-vegan diets, but has been declining steadily in Asia as diets have become progressively higher in animal products. There is good reason to suspect that low-fat vegan diets tend to down-regulate systemic IGF-I activity; this effect would be expected to increase stroke risk in vegans. Furthermore, epidemiology suggests that low serum cholesterol, and possibly also a low dietary intake of saturated fat--both characteristic of those adopting low-fat vegan diets--may also increase stroke risk. Vegans are thus well advised to adopt practical countermeasures to minimize stroke risk--the most definitive of which may be salt restriction. A high potassium intake, aerobic exercise training, whole grains, moderate alcohol consumption, low-dose aspirin, statin or policosanol therapy, green tea, and supplementation with fish oil, taurine, arginine, and B vitamins--as well as pharmacotherapy of hypertension if warranted--are other practical measures for lowering stroke risk. Although low-fat vegan diets may markedly reduce risk for coronary disease, diabetes, and many common types of cancer, an increased risk for stroke may represent an 'Achilles heel'. Nonetheless, vegans have the potential to achieve a truly exceptional 'healthspan' if they face this problem forthrightly by restricting salt intake and taking other practical measures that promote cerebrovascular health.