Platelet Activation in Coronary Artery Disease

Quantification of platelet function - a comparative study of venous and arterial blood using a novel flow cytometry protocol

Studies of platelet function in surgical patients often involve both arterial and venous sampling. Possible effects of different sampling sites could be important, but have not been thoroughly investigated. We aimed to compare platelet function in arterial and venous blood samples using a novel flow cytometry protocol and impedance aggregometry. Arterial and venous blood was collected before anesthesia in 10 patients undergoing cardiac surgery of which nine was treated with acetylsalicylic acid until the day before surgery. Flow cytometry included simultaneous analysis of phosphatidylserine exposure, active conformation of the fibrinogen receptor (PAC-1 binding), α-granule and lysosomal release (P-selectin and LAMP-1 exposure) and mitochondrial membrane integrity. Platelets were activated with ADP or peptides activating thrombin receptors (PAR1-AP/PAR4-AP) or collagen receptor GPVI (CRP-XL). Leukocyte-platelet conjugates and P-selectin exposure were evaluated immediately in fixated samples. For impedance aggregometry (Multiplate®), ADP, arachidonic acid, collagen and PAR1-AP (TRAP) were used as activators. Using impedance aggregometry and in 27 out of 37 parameters studied with flow cytometry there was no significant difference between venous and arterial blood sampling. Arterial blood showed more PAC-1 positive platelets when activated with PAR1-AP or PAR4-AP and venous blood showed more monocyte-platelet and neutrophil-platelet conjugates and higher phosphatidylserine exposure with CRP-XL alone and combined with PAR1-AP or PAR4-AP. We found no differences using impedance aggregometry. In conclusion, testing of platelet function by flow cytometry and impedance aggregometry gave comparable results for most of the studied parameters in venous and arterial samples. Flow cytometry identified differences in PAC-1 binding when activated with PAR1-AP, exposure of phosphatidyl serine and monocyte/neutrophil-platelet conjugates, which might reflect differences in blood sampling technique or in flow conditions in this patient cohort with coronary artery disease. These differences might be considered when comparing data from different sample sites, but caution should be exercised if a different protocol is used or another patient group is studied.

High mean platelet volume to platelet count ratio as a predictor on poor outcomes after CABG

OBJECTIVES

To determine the effect of mean platelet volume (MPV) to platelet count (PC) ratio on postoperative poor outcomes, early mortality and long-term survival rate in patients undergoing CABG.

METHODS

Between February 2016 and September 2018, all patients undergoing CABG in our department were retrospectively reviewed. A total of 213 consecutive patients were included in the study.

RESULTS

Mean age was 61.5 ± 9.7 years and mean follow-up of all patients was 1.4 ± 0.5 years. All patients were divided into two groups as high and low MPV/PC ratio in terms of 3.825 of cut-off point. 72 patients had a high MPV/PC ratio, whereas, 141 patients had low MPV/PC ratio. The rates of reoperation for early vein-graft occlusion, low cardiac output syndrome and respiratory complication were significantly higher in group 1 (p = 0.03, 0.04 and 0.01). The mean hospital length of stay was higher in group 1 (p = 0.03). MPV/PC ratio for reoperation for early vein-graft occlusion; MPV and ejection fraction for low cardiac output syndrome; hyperlipidemia, chronic renal failure history and MPV/PC ratio for sepsis; male gender, CRF history and CPB time for atrial fibrillation; age, congestive heart failure history, myocardial infarction history and CPB time for the early mortality were found to be independent predictors. Peripheral arterial diseases, USAP and MPV/PC ratio were found to be independent predictors for the late mortality.

CONCLUSIONS

A high MPV/PC ratio is associated with early vein-graft occlusion and poor postoperative outcomes in the early period after CABG. Furthermore, it has a negative effect on late survival.

Mean platelet volume is associated with serum 25-hydroxyvitamin D concentrations in patients with stable coronary artery disease

There is little published data on the association of platelet function and 25(OH)D concentration. We investigated the associations between mean platelet volume (MPV) and 25(OH)D concentration in patients with stable coronary artery disease. Study population was divided into three groups: group 1-25(OH)D < 10 ng/mL (N = 22), group 2-25(OH)D 10-20 ng/mL (N = 42), and group 3-25(OH)D > 20 ng/mL (N = 14). Study groups shared similar demographics. MPV values were the highest in group 1, moderate in group 2, and the lowest in group 3 (11.1 vs 10.4 vs 9.8 fL P < 0.001). There was a negative correlation between MPV and 25(OH)D (R = - 0.38, P = 0.001). ROC analysis demonstrated a moderate predictive value (AUC 0.70) in identifying the discrimination thresholds of MPV (> 10.5 fL) for vitamin D deficiency and a weak predictive value (AUC 0.65) in identifying the discrimination thresholds of 25(OH)D concentration (≤ 15.5 ng/mL) for the presence of large platelets (MPV over the upper limit of normal). In conclusion, even though the effect of vitamin D on platelet size and function is probably multifactorial, our study provides further evidence linking vitamin D to thrombosis and hemostasis. Platelets are another potential element through which vitamin D deficiency could exert adverse cardiovascular outcomes.

Differences in high on-treatment platelet reactivity between intracoronary and peripheral blood after dual anti-platelet agents in patients with coronary artery disease

The differences of high on-treatment platelet reactivity (HPR) between the coronary arteries and peripheral veins might be associated with poor prediction of adverse cardiovascular events in patients with coronary artery diseases. HPR from the peripheral blood might not adequately reflect the platelet responses in the coronary artery. A total of 21 patients were recruited, and regional differences in HPR were compared between blood samples from the intra-coronary artery (IC), femoral artery (FA), and femoral vein (FV) by light aggregometry (agonists: arachidonic acid, LTA-AA; ADP, LTA-ADP), VerifyNow P2Y12 assays, and a platelet function analyser (PFA-100, collagen and epinephrine cartridge, PFA-CEPI). There were regional differences in the platelet reactivities observed by LTA-AA, VerifyNow P2Y12 assays, and PFACEPI. Platelets from the IC had higher platelet reactivities than those from the FV and FA by the VerifyNow P2Y12 assays but lower reactivities by LTA-AA and PFA-CEPI. HPR values from the blood in the FA were more similar to those from the IC than those from the FV by any test. The monocyte percentages were the only factors associated with differences in HPR between the FV and IC by the VerifyNow P2Y12 assays. Triglyceride levels were associated with the differences in HPR between the FV and IC by LTA-ADP. During the six-month follow-up period, two patients developed cardiovascular events and exhibited differences in HPR between different sites by VerifyNow P2Y12 assays. In conclusions, there were regional differences in HPR in patients with coronary artery diseases, which might prevent the adequate prediction of cardiovascular events.

Long-term serial changes in platelet activation indices following sirolimus elution and bare metal stent implantation in patients with stable coronary artery disease

BACKGROUND

Platelet activation is crucial in the development of stent thrombosis following percutaneous coronary intervention (PCI). We carried out a long-term assessment of multiple factors implicated in the thrombotic process and monitored markers of platelet activation after the implantation of sirolimus-eluting stents (SES) in patients with stable coronary artery disease (CAD). Additionally, we compared these findings with those after bare-metal stent (BMS) implantation.

METHODS

A cohort of 47 consecutive patients, aged <70 years, with severe stenosis (>70% narrowing of the lumen) of one major epicardial coronary artery and stable CAD underwent successful elective PCI. Patients were randomly allocated to SES (n = 25) or BMS (n = 22). Venous blood was obtained 24 hours before and 24 hours, 48 hours, 1 month, and 6 months after PCI for measurements of plasma levels of sP-selectin, von Willebrand Factor (vWF), fibrinogen, d-dimer, sCD40, factor VIII, b-thromboglobulin (b-TG) and platelet factor 4 (PF-4).

RESULTS

There were no significant differences between the two groups in levels of fibrinogen or d-dimers in peripheral blood. However, we observed a significant kinetic effect (p<0.001) and stent-effect (p<0.015) on vWF levels and a significant kinetic effect (p = 0.012) on factor VIII, sP-selectin (p = 0.04), b-TG (p<0.001), and PF4 (p = 0.016). A trend towards a significant stent effect on sCD40 was also detected (p = 0.06).

CONCLUSIONS

SES and BMS did not show significant differences in relationship to markers of platelet activation and coagulation in patients with stable CAD. Although some markers showed an increase after stent implantation, they returned to the initial levels 6 months later.

Platelet activation increases in patients undergoing vascular surgery

BACKGROUND

Platelets are a major contributor to atherothrombosis and may contribute to the heightened risk of perioperative cardiovascular events. We sought to examine changes in platelet activity in subjects undergoing vascular surgery.

METHODS

Platelet activity in 18 patients (median age 74, 45% female) undergoing non-emergent open vascular surgery was assessed by light transmission aggregometry in response to saline, epinephrine and adenosine-5 diphosphate (ADP), and by flow cytometric analysis of monocyte-platelet aggregation (MPA). Platelet activity was assessed preoperatively (T1), 1-hour into the operation (T2), 1-hour (T3), 24-hours (T4) and 48-hours post-operatively (T5). Data were compared using the Wilcoxon Signed Ranks Test. Continuous variables are summarized as medians and (interquartile, IQR) ranges.

RESULTS

Spontaneous platelet aggregation increased transiently during the surgical period (T1-5.8% [2.4, 10.8], T2-13.5% [9.3, 26.5], T3-7.5% [3.3, 17], T4-10.0% [7.3, 16.3], T5-7.25% [4.5, 29.9], P=0.002). Similar trends in perioperative platelet activity were noted for platelet aggregation in response to epinephrine (P=0.035) and ADP (P=0.036). Using flow cytometry, we found an increase in MPA during the perioperative period (P=0.047), which was most significant between T1 and T3 (P=0.005).

CONCLUSIONS

Platelet activity increases significantly during and following open vascular surgery. This data may help explain the pathophysiology of increased thrombotic risk during the perioperative period of vascular surgery.

Effects of the P-selectin antagonist inclacumab on myocardial damage after percutaneous coronary intervention for non-ST-segment elevation myocardial infarction: results of the SELECT-ACS trial

OBJECTIVES

The study aimed to evaluate inclacumab for the reduction of myocardial damage during a percutaneous coronary intervention (PCI) in patients with non-ST-segment elevation myocardial infarction.

BACKGROUND

P-selectin is an adhesion molecule involved in interactions between endothelial cells, platelets, and leukocytes. Inclacumab is a recombinant monoclonal antibody against P-selectin, with potential anti-inflammatory, antithrombotic, and antiatherogenic properties.

METHODS

Patients (N = 544) with non-ST-segment elevation myocardial infarction scheduled for coronary angiography and possible ad hoc PCI were randomized to receive 1 pre-procedural infusion of inclacumab 5 or 20 mg/kg or placebo. The primary endpoint, evaluated in patients who underwent PCI, received study medication, and had available efficacy data (n = 322), was the change in troponin I from baseline at 16 and 24 h after PCI.

RESULTS

There was no effect of inclacumab 5 mg/kg. Placebo-adjusted geometric mean percent changes in troponin I with inclacumab 20 mg/kg were -24.4% at 24 h (p = 0.05) and -22.4% at 16 h (p = 0.07). Peak troponin I was reduced by 23.8% (p = 0.05) and area under the curve over 24 h by 33.9% (p = 0.08). Creatine kinase-myocardial band yielded similar results, with changes of -17.4% at 24 h (p = 0.06) and -16.3% at 16 h (p = 0.09). The incidence of creatine kinase-myocardial band increases >3 times the upper limit of normal within 24 h was 18.3% and 8.9% in the placebo and inclacumab 20-mg/kg groups, respectively (p = 0.05). Placebo-adjusted changes in soluble P-selectin level were -9.5% (p = 0.25) and -22.0% (p < 0.01) with inclacumab 5 and 20 mg/kg. There was no significant difference in adverse events between groups.

CONCLUSIONS

Inclacumab appears to reduce myocardial damage after PCI in patients with non-ST-segment elevation myocardial infarction. (A Study of RO4905417 in Patients With Non ST-Elevation Myocardial Infarction [Non-STEMI] Undergoing Percutaneous Coronary Intervention; NCT01327183).

Platelet function in health and disease: from molecular mechanisms, redox considerations to novel therapeutic opportunities

Increased oxidative stress appears to be of fundamental importance in the pathogenesis and development of several disease processes. Indeed, it is well known that reactive oxygen species (ROS) exert critical regulatory functions within the vascular wall, and it is, therefore, plausible that platelets represent a relevant target for their action. Platelet activation cascade (including receptor-mediated tethering to the endothelium, rolling, firm adhesion, aggregation, and thrombus formation) is tightly regulated. In addition to already well-defined platelet regulatory factors, ROS may participate in the regulation of platelet activation. It is already established that enhanced ROS release from the vascular wall can indirectly affect platelet activity by scavenging nitric oxide (NO), thereby decreasing the antiplatelet properties of endothelium. On the other hand, recent data suggest that platelets themselves generate ROS, which may evoke pro-thrombotic responses, triggering many biological processes participating in atherosclerosis initiation, progression, and complication. That oxidative stress may alter platelet function is conceivable when considering that antioxidants play a role in the prevention of cardiovascular disease, although the precise mechanism accounting for changes attributable to antioxidants in atherosclerosis remains unknown. It is possible that the effects of antioxidants may be a consequence of their enhancing or promoting the antiplatelet effects of NO derived from both endothelial cells and platelets. This review focuses on current knowledge regarding ROS-dependent regulation of platelet function in health and disease, and summarizes in vitro and in vivo evidence for their physiological and potential therapeutic relevance.

Mean platelet volume is increased in patients with deep vein thrombosis

BACKGROUND

Pulmonary thromboembolism is a serious complication in patients with deep vein thrombosis (DVT). Previous studies have demonstrated that platelet activation occurs in patients with DVT. Mean platelet volume (MPV) is a simple and easy method of assessing platelet function. The aim of this study was to assess the MPV, an indicator of platelet activation in patients with DVT.

PATIENTS AND METHODS

The study group consisted of 52 patients with newly diagnosed acute DVT. An age-, gender-, and body mass index-matched control group consisted of 30 healthy volunteers. All patients and control participants underwent ultrasonographic examination. We measured the serum MPV values in patients with DVT and control participants.

RESULTS

Mean platelet volume was significantly higher among patients with DVT when compared with the control group (8.6 ± 0.8 vs 7.7 ± 0.9 fL, respectively; P < .001).

CONCLUSION

We have shown that MPV was significantly elevated in patients with DVT compared to controls.

[Urgent percutaneous coronary intervention leads to a decrease in serum concentrations of soluble CD40 ligand]

BACKGROUND/AIM

Inflammation as a consequence of vascular injury after percutaneous coronary intervention (PCI) is a pathological substrate of restenosis and of its complications. The aim of the study was to examine perprocedural inflammatory response expressed by soluble CD40 ligand (sCD40L) and C-reactive protein (CRP) in patients treated with PCI and dual antiplatelet therapy.

METHODS

The experimental group included 52 patients (80.8% men, age 60 +/- 9 years) with angina pectoris treated by PCI (22 urgent PCI) with stent implantation, and dual antiplatelet therapy (tienopiridins and aspirin), according to the current recommendations for the execution of the intervention. The control group consisted of 8 patients (70.5% men, age 59 +/- 7 years) with angina pectoris, who had undergone coronarography taking aspirin 3 days prior to it. In all the patients 24 hours before and after the PCI concentrations of CRP and sCD40L in the blood were determined.

RESULTS

In the experimental group, the concentration of sCD40L was lower as compared to the control (p < 0.02). In 34 (65%) patients postprocedural decrease in sCD40L was recorded, in 18 (34.6%) of them increase, while in 50 (96%) patients there was a rise in CRP. The patients with postprocedural fall in sCD40L hod greater preprocedural concentration of sCD40L (p < 0.001), and less postprocedural concentration of sCD40L (p < 0.001), compared to the group with an increase in sCD40L after the PCI, while CRP levels between these groups were not statistically different. Patients treated with emergency PCI compared to elective patients had a postprocedural decrease in sCD40L (p = 0.02). Increase in the level of CRP was higher in the group with emergency PCI in relation to elective PCI (p < 0.01).

CONCLUSION

Emergency PCI procedures in the treatment of patients with unstable angina pectoris lead to a postprocedural fall in the serum concentration of sCD40L. Dual antiplate therapy with tienopiridins and aspirin inhibits the release of sCD40L. Regardless a clinical presentation of coronary disease PCI leads to an postprocedural increase in concentrations of CRP in the serum.

Timing of clopidogrel loading before percutaneous coronary intervention in clopidogrel-naive patients with stable or unstable angina: a comparison of two strategies

BACKGROUND

Clopidogrel-naive patients subjected to coronary angiography may be candidates for percutaneous coronary intervention (PCI). Clopidogrel loading with 600 mg at least 2 hours before the procedure is advised for such patients. However, there is no direct evidence that delaying PCI for 2 hours after clopidogrel loading is superior to ad hoc PCI.

METHODS

After coronary angiography, clopidogrel-naive patients (N = 199) with stable or unstable angina, candidates for PCI, were loaded with 900 mg of clopidogrel and then randomized to ad hoc PCI (ad hoc group, n = 103) or delayed PCI 2 hours after loading (delayed group, n = 96). Combined primary end point was death/periprocedural myocardial infarction (MI)/stroke/reintervention within 30 days post-PCI. Secondary end points were periprocedural MI; periprocedural creatine kinase-MB elevation >3 x upper limit of normal; any periprocedural increase of creatine kinase-MB, troponin-I, or myoglobin above upper limit of normal; Thrombolysis in Myocardial Infarction flow <3 after PCI; thrombocytopenia with platelet count of <70,000/mL; major bleeding defined according to the Thrombolysis in Myocardial Infarction criteria; and elevation of high-sensitivity C-reactive protein and soluble P selectin.

RESULTS

Primary end point occurred in 12.6% ad hoc group versus 15.6% delayed group patients (P = .34). High-sensitivity C-reactive protein increased in both groups post-PCI (analysis of variance P < .0001) without difference between groups (P = .5). Major bleeding occurred in 2.9% ad hoc group versus 3.1% delayed group patients (P = .9). No significant difference was observed in any other secondary end point.

CONCLUSIONS

In clopidogrel-naive patients, a strategy of delaying PCI for 2 hours after high-dose clopidogrel loading does not seem to confer any benefit compared to ad hoc PCI.

The relationship of mean platelet volume with the risk and prognosis of cardiovascular diseases

BACKGROUND

Mean platelet volume (MPV) is arousing increasing interest as a new independent cardiovascular risk factor.

AIM

To provide a comprehensive review on the biological significance, the main determinants and the prognostic implications of MPV.

METHODS

A literature search was performed using key terms, such as 'MPV' or 'mean platelet volume', together with 'stroke', 'myocardial infarction' and 'diabetes and 'obesity'.

RESULTS

Large platelets are likely more reactive: elevated MPV values are associated with a shortened bleeding time and increased thromboxane B2 plasma levels. Thus, MPV could be considered an indicator of platelet function. Platelet size is mainly determined in the bone marrow during megakaryocytopoiesis, and subsequently does not substantially change. MPV is only partially regulated by thrombopoietin: in fact, growth factors and cytokines may also elicit the production of larger and more reactive platelets in the bone marrow, in the presence of conditions capable of increasing their concentrations, such as obesity, endothelial dysfunction and possibly myocardial and cerebral ischaemia. This phenomenon could play an important role in vascular diseases. In fact MPV is predictive of stroke, acute myocardial infarction (AMI) and restenosis of coronary angioplasty, is increased in the presence of obesity, diabetes mellitus, metabolic syndrome, AMI and stroke and has been shown to have a prognostic significance in patients with stroke and AMI.

CONCLUSION

In assessing whole blood count, MPV should not be undervalued, as its increase should suggest a careful assessment of cardiovascular risk.