Platelets
-
Previous studies have reported increased platelet activation and aggregation in patients with obstructive sleep apnea (OSA). Continuous positive airway pressure (CPAP) treatment has been shown to decrease platelet activation. We aimed to study the effects of nasal CPAP therapy has on MPV values in patients with severe OSA. ⋯ The six months of CPAP therapy caused significant reductions in median (IQR) MPV values in patients with severe OSA (8.5 [8.3-9.1] to 7.9 [7.4-8.2] fL; p < 0.001). Six months of CPAP therapy caused significant increase in platelet counts when compared with baseline values (217.8 ± 45.9 to 233.7 ± 60.6 × 10⁹/L; p < 0.001). We have found that the MPV values of patients with severe OSA were significantly higher than those of the control subjects and 6 months CPAP therapy caused significant reductions in the MPV values in patients with severe OSA.
-
Thrombelastography (TEG) analyses the status of blood coagulation including abnormalities associated with low platelet count. The aim of this study was to investigate the changes in TEG parameters in idiopathic thrombocytopenic purpura (ITP) patients. Thirty nine patients with ITP (platelet count < 100 × 103 µl⁻¹) were included in the study. ⋯ Receiver operating characteristic curves to describe the critical platelet count and fibrinogen level that affect MCF revealed 31 × 103 µl⁻¹ and 375 mg dl⁻¹ as cut-off values, respectively. In conclusion, ROTEM determines the contribution of fibrinogen and platelets to clot strength in patients with ITP. MCF appears to be the most important TEG parameter in predicting bleeding in ITP patients that makes TEG superior to other hemostatic tests.
-
Randomized Controlled Trial Multicenter Study
The effects of laropiprant, a selective prostaglandin D₂ receptor 1 antagonist, on the antiplatelet activity of clopidogrel or aspirin.
Laropiprant (LRPT) is being developed in combination with Merck's extended-release niacin (ERN) formulation for the treatment of dyslipidemia. LRPT, an antagonist of the prostaglandin PGD₂ receptor DP1, reduces flushing symptoms associated with ERN. LRPT also has affinity for the thromboxane A₂ receptor TP (approximately 190-fold less potent at TP compared with DP1). ⋯ At 4 hours after the last dose, co-administration of LRPT 40 mg resulted in 3% and 41% increase in bleeding time vs. bleeding time after treatment with aspirin or clopidogrel alone, respectively. Co-administration of LPRT with clopidogrel or aspirin was generally well tolerated in healthy subjects. Co-administration of multiple doses of LRPT 40 mg and clopidogrel 75 mg or aspirin 81 mg had no clinically important effects on bleeding time or platelet aggregation.
-
Platelet size, measured as mean platelet volume (MPV), is associated with platelet reactivity. MPV has been identified as an independent risk factor for future stroke and myocardial infarction. The aim of this study was to determine the association of MPV with the development of stoke in patients with atrial fibrillation (AF). ⋯ Furthermore, AF patients with an MPV over 8.85 fL had high stroke risk without anticoagulation, especially in the low thromboembolic risk group (Log-Rank <0.0001). The results of this study show that MPV was a predictive marker for stroke; its predictive power for stroke was independent of age, gender, and other CHADS(2) score components in patients with AF. These findings suggest that anticoagulation may be needed in patients with a high MPV, even if they have low to intermediate traditional thromboembolic risk (CHADS(2) score <2).
-
Morning increase in the occurrence of myocardial infarction, stroke and sudden cardiac death is a well-recognized phenomenon, which is in line with a morning enhancement of platelet aggregation. We investigated whether platelet inhibition during clopidogrel and aspirin therapy varies during the day. Fifty-nine consecutive patients (45 men and 14 women) with first ST-segment elevation myocardial infarction (STEMI) treated with primary percutaneous coronary interventions (pPCI) on dual antiplatelet therapy were prospectively enrolled into the study. ⋯ In contrast, no diurnal variation in the antiplatelet effect of aspirin was observed. In conclusion, in patients presenting with STEMI undergoing pPCI, platelet inhibition by clopidogrel is less strong in the midmorning hours. This periodicity in platelet aggregation in patients on dual antiplatelet therapy should be taken into consideration when assessing platelet function in clinical studies.