Effect of pathological high shear exposure time on platelet activation and aggregation

The relationship between ABO blood types and clopidogrel-related low on-treatment platelet reactivity in patients with coronary artery diseases and type 2 diabetes mellitus: a secondary analysis of a prospective cohort study

BACKGROUND

The risk of bleeding associated with antiplatelet therapy in patients with coronary artery disease (CAD) has received a lot of attention. The aim of this study was to investigate the relationship between ABO blood system and low on-treatment platelet reactivity (LTPR) in patients with CAD and type 2 diabetes mellitus (T2DM).

METHODS

This study examined 10,724 consecutive patients who received percutaneous coronary intervention in China between January and December in 2013 and applied logistic regression to assess the association between ABO blood types and LTPR. These patients who were diagnosed with T2DM, had thromboelastogram (TEG) results and were administered clopidogrel were ultimately enrolled. LTPR is defined by a platelet maximum amplitude of < 31 mm on TEG, induced by adenosine diphosphate.

RESULTS

Among 3,039 patients (mean age, 59.35 ± 9.89; male, 74.60%), 1,089 (35.83%) presented with LTPR. Multivariate logistic regression revealed that blood type O was independently related to higher odds of LTPR (OR O vs. Non-O: 1.298, 95% CI 1.099-1.534) and that blood type A was independently related to lower odds of LTPR (OR A vs. Non-A: 0.804, 95% CI 0.674-0.958). For further analysis, multivariate logistic regression revealed that, compared to blood type A, type O was independently related to higher odds of LTPR (OR O vs. A: 1.409, 95% CI 1.147-1.729).

CONCLUSIONS

This study reported that in patients with CAD and T2DM, blood type O was independently associated with higher odds of LTPR, indicating a greater likelihood of bleeding, while blood type A was independently related to lower odds of LTPR, suggesting a reduced likelihood of bleeding.

The rapid change of shear rate gradient is beneficial to platelet activation

Fluid shear plays a key role in hemostasis and thrombosis, and the purpose of this study was to investigate the effect of shear gradient change rate (SGCR) on platelet reactivity and von Willebrand factor (vWF) activity and its mechanism. In this study, we developed a set of microfluidic chips capable of generating different shear gradients and simulated the shear rate distribution in the flow field by COMSOL Multiphysics software. Molecular markers of platelet activation (P-selectin, activated GPIIb/IIIa, phosphatidylserine exposure, and monocyte-platelet aggregate formation) were analyzed by flow cytometry. Platelet aggregation induced by shear gradient was studied by a microfluidic experimental platform, and plasma vWF ristocetin cofactor (vWF: RCO) activity was investigated by flow cytometry. The expression of p-Akt was studied by Western blotting. The results showed that the faster the SGCR, the higher the expression of platelet p-Akt, and the stronger the platelet reactivity and vWF activity. This indicates that fluid shear stress can activate platelets and vWF in a shear gradient-dependent manner through the PI3K/AKT signal pathway, and the faster the SGCR, the more significant the activation effect.

Effects of body posture on aortic valve hemodynamics and biomechanics using the fluid-structure interaction method

Bioprosthetic heart valve (BHV), the most widely and commonly used valves in clinical practice, are susceptible to fatigue damage. Biological valves are always in one or fewer body postures before sampling in pigs and bovines. Nevertheless, human body positions are far more than them. Variations in body position significantly affect the intrinsic environment of blood pressure (BP), heart rate (HR), and peripheral resistance (PR). Such boundary condition changes will inevitably affect the implanted biological valve. In this paper, the immersed boundary method was used to simulate the motion of the aortic valve during the entire cardiac cycle in five postural blood flow environments: upright, sitting, prone, supine and orthostatic hypotension (OH). Several hemodynamic and biomechanical parameters, including the transvalvular pressure gradient and valve displacement, were evaluated. The results showed that the OH group exhibited the worst performance of the valves, accompanied by the greatest regurgitation and high-frequency flutter, predisposing patients to thrombosis and fatigue calcification. For BHVs to serve longer, patients implanted with BHV should avoid OH in their daily routine.

Increased platelet-leucocyte complexes do not result in coagulation activation in plateletpheresis donors

BACKGROUND

Although plateletpheresis donation is commonly accepted as a safe procedure, its influence on platelet function, coagulation system and fibrinolysis is not completely elucidated.

OBJECTIVES

In this study, we tried to assess the effects of plateletpheresis on donor's hemostasis system by measuring platelet activation, development of platelet-leukocyte aggregates, and coagulation activation.

STUDY DESIGN

Prospective observational study.

METHODS

We used flow cytometry to determine the levels of platelet-monocyte complexes (PMC) and platelet-neutrophil complexes (PNC). sP-selectin and prothrombin fragment (PF) 1 + 2 values were determined by ELISA.

RESULTS

The PMC levels increased significantly seven days after apheresis in comparison with just after apheresis and 24 h after apheresis (p < 0.05). The PNC levels increased significantly seven days after apheresis compared to immediately after apheresis (p < 0.05). sP-selectin values decreased significantly immediately after apheresis (p < 0.05). While sP-selectin values increased seven days after apheresis in comparison with immediately after apheresis and 24 h after apheresis, but there were not statistically significant differences for sP-selectin levels (p > 0.05). PF1 + 2 levels decreased significantly immediately after apheresis compared to pre-apheresis (p < 0.05) and increased 24 h after apheresis and seven days after apheresis, but these differences were not statistically significant.

CONCLUSION

We concluded that plateletpheresis affects platelet activation but does not cause any change in coagulation activation.