Faculty Bibliography

Background: Light transmission aggregometry (LTA) is considered the gold standard for investigating platelet activity ex vivo. However, LTA protocols are not standardized, and differences in LTA procedure are a potential source of variance in results. Centrifugation speed is an essential component of platelet preparation in LTA, has yet to be standardized, and may affect platelet aggregation results. We sought to investigate the effect of relative centrifugal force (RCF) intensity on LTA results. Methods: Ten healthy controls had venous blood drawn and centrifuged at 150, 200, 300, and 500 g for 10 min. Cell counts in whole blood and platelet-rich plasma (PRP) were measured using a hematology analyzer. LTA was performed using 1.0 mum adenosine diphosphate (ADP) and 0.4 mum epinephrine as an agonist. Aggregation (%) was compared at 60, 120, 180, and 300 s and at maximum aggregation. Results: Centrifugation speed was associated with decreasing platelet count (P < 0.001) and decreasing mean platelet volume (P < 0.001) in PRP. Maximum aggregation decreased with increasing speeds for ADP 1.0 mum (150 g- 89%, 200 g- 93%, 300 g- 71%, 500 g- 17%; P < 0.001). Similar findings were noted at 120 s (150 g- 69%, 200 g- 50%, 300 g- 35%, 500 g- 12%; P < 0.001), 180 s (150 g- 82%, 200 g- 74%, 300 g- 44%, 500 g- 13%; P < 0.001), and 300 s (150 g- 85%, 200 g- 88%, 300 g- 55%, 500 g- 14%; P < 0.001). Consistently, platelet aggregation in response to epinephrine 0.4 mum decreased significantly with increasing centrifuge RCF at 60, 120, 180, 300 s and at maximum aggregation (P < 0.05 for each comparison). Conclusion: Our data demonstrate the importance of centrifugation speed in the interpretation of LTA results, supporting the need for standardization of centrifugation RCF in LTA protocols

Almost one third of annual worldwide mortality is attributed to cardiovascular disease (CVD), making it the leading cause of global death. Dyslipidemia is a well-established risk factor for CVD and plays a pivotal role in the pathogenesis of atherosclerosis. Statins, which inhibit 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase and lower low-density lipoprotein cholesterol, have emerged as the most effective therapy to date against atherothrombotic CVD. Although their role in secondary prevention of CVD is undisputed, it remains a topic for debate as to how widely they should be used for primary prevention. The Framingham Risk Score and the National Cholesterol Education Program Adult Treatment Panel III guidelines are the cornerstones for the current guidelines for primary prevention statin therapy. Although these guidelines serve as help to evaluate cardiovascular risk and effectively identify many patients who will benefit from statin therapy, there is a growing population of "intermediate-risk" patients who may be undertreated. Additional noninvasive tests may complement the traditional risk scores, potentially expanding the indications for statins.

Cardiovascular disease is a major cause of morbidity and mortality. Numerous risk scores exist to identify healthy individuals at increased risk of developing cardiovascular disease. Although platelets are a key mediator in the pathogenesis of cardiovascular disease, the role of platelet activity measurements and the incidence of cardiovascular disease are uncertain. Platelet aggregometry-the most well studied method of platelet function testing-is associated with risk factors for cardiovascular disease. However, data supporting platelet aggregation and incident cardiovascular disease is conflicting. Plasma markers of platelet activation are promising candidates. Soluble CD40L and P-selectin are easily measured with a standardized ELISA, and there is some data to suggest an association with cardiovascular disease, but further studies are required. While mean platelet volume is a promising candidate, platelet count and bleeding time are not specific for platelet activity nor are they associated with cardiovascular disease in a healthy population. For this field to progress, we recommend large-scale, prospective studies that measure a battery of these platelet function tests in individuals without cardiovascular disease to better understand the associations, if any, between platelet activity and cardiovascular disease

BACKGROUND: The benefit of aspirin to prevent cardiovascular events in subjects without clinical cardiovascular disease relative to the increased risk of bleeding is uncertain. METHODS: A meta-analysis of randomized trials of aspirin versus placebo/control to assess the effect of aspirin on major cardiovascular events (MCEs) (nonfatal myocardial infarction, nonfatal stroke, or cardiovascular death), individual components of the MCE, stroke subtype, all-cause mortality, and major bleeding. Nine trials involving 102,621 patients were included: 52,145 allocated to aspirin and 50,476 to placebo/control. RESULTS: Over a mean follow-up of 6.9 years, aspirin was associated with a reduction in MCE (risk ratio [RR] 0.90, 95% CI 0.85-0.96, P < .001). There was no significant reduction for myocardial infarction, stroke, ischemic stroke, or all-cause mortality. Aspirin was associated with hemorrhagic stroke (RR 1.35, 95% CI 1.01-1.81, P = .04) and major bleeding (RR 1.62, 95% CI 1.31-2.00, P < .001). In meta-regression, the benefits and bleeding risks of aspirin were independent of baseline cardiovascular risk, background therapy, age, sex, and aspirin dose. The number needed to treat to prevent 1 MCE over a mean follow-up of 6.9 years was 253 (95% CI 163-568), which was offset by the number needed to harm to cause 1 major bleed of 261 (95% CI 182-476). CONCLUSIONS: The current totality of evidence provides only modest support for a benefit of aspirin in patients without clinical cardiovascular disease, which is offset by its risk. For every 1,000 subjects treated with aspirin over a 5-year period, aspirin would prevent 2.9 MCE and cause 2.8 major bleeds

BACKGROUND: The association between bleeding severity and cause of mortality in the non-acute setting is unclear. We sought to investigate the association between bleeding and mortality subtype, and assess whether this association differs in patients on dual antiplatelet therapy (DAPT) versus aspirin alone. METHODS: Using multivariable Cox proportional hazards survival regression, we examined the association between moderate or severe bleeding and all-cause, cardiovascular, and cancer mortality in 15,603 patients with cardiovascular disease or multiple risk factors enrolled in the CHARISMA trial. RESULTS: Patients with moderate or severe bleeding had a higher incidence of all-cause, cardiovascular, and cancer mortality (P < .001 for each). After multivariable adjustment, moderate/severe bleeding remained independently associated with not only all-cause mortality (adjusted hazard ratio [HR] 1.66; 95% confidence interval [CI] 1.24-2.21) and cardiovascular mortality (HR 2.05, 95% CI 1.38-3.04) but also cancer mortality (HR 4.76, 95% CI 2.60-8.69). However, there was a significant interaction between bleeding and potency of antiplatelet therapy for all-cause (P = .002), cardiovascular (P = .02), and cancer mortality (P = .03); in subjects on aspirin alone, moderate/severe bleeding was associated with all-cause (HR 5.27, 95% CI 3.56-7.80), cardiovascular (HR 4.33, 95% CI 2.55-7.37), and cancer mortality (HR 9.01, 95% CI 4.41-18.43), but not in subjects on DAPT (all-cause: HR 1.48, 95% CI 0.93-2.34; cardiovascular: HR 1.04, 95% CI 0.58-1.86; and cancer mortality: HR 1.79, 95% CI 0.56-5.74). CONCLUSIONS: In stable patients, moderate or severe bleeding is associated with a significantly increased risk of all-cause, cardiovascular, and cancer mortality. However, this risk appeared different in subjects on single antiplatelet therapy versus DAPT