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 IIb/IIIa receptors, platelet surface P-selectin, platelet-monocyte 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.

We have investigated the effects of chronic physical training and acute intensive exercise on plasma fibrinogen levels and the relationship of these responses to beta-fibrinogen G-453-A polymorphism genotype. One hundred fifty-six male British Army recruits were studied at the start of their 10-week basic training, which emphasizes physical fitness. Cohorts were restudied between 0.5 and 5 days after a major 2-day strenuous military exercise (ME) undertaken in their final week of training. Changes in fibrinogen concentration were adjusted for the effects of age, body mass index, and smoking history. Compared with baseline values, fibrinogen concentrations were significantly lower (11.9%, P=.04) at day 5 after ME, consistent with the beneficial effect of training. However, they were higher on days 1 through 3 after ME (suggesting an "acute-phase" response to strenuous exercise) and were maximal on days 1 and 2 (27.2%, P<.001 and 37.1%, P<.001 respectively). Fibrinogen genotype was available in 149 individuals. As expected from previous studies, men with one or more fibrinogen gene A-453 alleles had plasma fibrinogen concentration slightly but significantly higher at baseline (4.5%, P=.11). During the acute-phase response (days 2 and 3), however, the degree of rise was strongly related to the presence of the A allele, being 26.7+/-5.4% (mean+/-SE), 36.5+/-11.0%, and 89.2+/-30.7 for the GG, GA, and AA genotypes, respectively (P=.01). These results confirm that chronic exercise training lowers plasma fibrinogen levels, that intensive exercise generates an acute-phase rise in levels, and that this acute response is strongly influenced by the G/A polymorphism of the beta-fibrinogen gene.

Platelet shape change (PSC) is an early phase of platelet activation that precedes platelet aggregation. This phase of platelet activation is essentially aspirin resistant. PSC was monitored, by measuring the median platelet volume (MPV) using a high resolution channelyser. Angiotensin (Ang) II, added in vitro, caused a significant (P ‫؍‬ 0.004) increase in MPV in platelet rich plasma prepared from healthy subjects (n ‫؍‬ 14). This increase in MPV was marked (Ͼ0.40 fl) in 57% (n ‫؍‬ 8) of these subjects and was significantly inhibited (P Ͻ 0.008) by losartan (a selective Ang II antagonist) at con-

We measured the serum lipid profile, together with plasma fibrinogen and serum lipoprotein(a) (Lp[a]), glucose, bilirubin, and albumin levels in 491 patients (310 men) who were referred for the management of primary dyslipidemia. All these variables have been shown to predict vascular events. The patients were not taking lipid-lowering drugs; hypertension was present in 156 (31.7%) of them. Of the hypertensive patients, 52 (33%) were not receiving any treatment to control their blood pressure. This omission was not due to a lower prevalence of established vascular disease. The treated hypertensives were divided into three groups according to their treatment: 62 were taking lipid-hostile antihypertensives (beta-blockers, thiazides), 37 were taking lipid-neutral antihypertensives (angiotensin converting enzyme inhibitors, Ca-channel blockers, angiotensin II receptor blockers, indapamide sustained release), and five were taking lipid-friendly antihypertensives (doxazosin). Lipid-hostile antihypertensive drugs were associated with a significantly higher fibrinogen concentration when compared with untreated hypertensives or those taking lipid-neutral/lipid-friendly drugs (median values: 383, 353, and 336 mg/dL, respectively; P < .01). Lipid-neutral/lipid-friendly antihypertensive drugs were associated with lower Lp(a) levels when compared with untreated hypertensives (median values: 22 and 45 mg/dL, respectively; P < .05). The serum bilirubin level was significantly lower in the untreated hypertensives when compared with normotensives or the treated hypertensives. There were no significant differences in lipids, glucose, or albumin among the groups of hypertensives or normotensives. The influence of antihypertensive drugs on additional cardiovascular risk factors should be considered when selecting medication to reduce blood pressure.