Mean Platelet Volume and Size Distribution and Their Sensitivity to Agonists in Patients with Coronary Artery Disease and Congestive Heart Failure

Mean Platelet Volume and Its Association With In-Hospital Outcomes in Patients With Acute ST-Segment Elevation Myocardial Infarction Undergoing Primary Percutaneous Coronary Intervention

Background Mean platelet volume (MPV), reflecting platelet size and activation, has been associated with cardiovascular disease (CVD) risk and mortality. Yet, its prognostic significance in acute coronary syndrome (ACS) patients undergoing primary percutaneous coronary intervention (PCI) remains uncertain. This study investigates whether elevated MPV levels upon admission in ST-segment elevation myocardial infarction (STEMI) patients predict adverse in-hospital outcomes after primary PCI. Objectives The aim of this study was to measure MPV in patients with STEMI who underwent primary PCI and to evaluate its association with in-hospital outcomes such as death, recurrent myocardial infarction, heart failure, and bleeding. Methods We enrolled 400 consecutive patients with STEMI (mean age 56.20 years, 356 males, 44 females) who underwent primary PCI at our center. We obtained MPV values from complete blood count tests performed at admission. We divided the patients into two groups based on the normal MPV range of 7.40 to 12 fL. We compared the baseline characteristics and in-hospital outcomes of the two groups. We used Cox proportional hazards regression analysis to adjust for potential confounders and evaluate the impact of MPV on in-hospital outcomes. Results There was no significant difference in MPV values between the two groups (9.10 ± 1.20 fL vs. 9.00 ± 1.10 fL, p = 0.54). Patients who died exhibited higher age, male predominance, hypertension, diabetes, a lower left ventricular ejection fraction, lower levels of low-density lipoprotein cholesterol, and lower levels of hemoglobin and hematocrit compared to survivors. MPV was not associated with any of the in-hospital outcomes in the unadjusted or adjusted analyses. Conclusion In this cohort of patients with STEMI who underwent primary PCI, admission MPV was not a predictor of in-hospital outcomes. Further studies are needed to clarify the role of MPV in the pathophysiology and prognosis of ACS.

Mean platelet volume: a prognostic marker in heart failure with preserved ejection fraction

Heart failure (HF) with preserved ejection fraction (HFpEF) is associated with high burden of comorbidities known to increase the mean platelet volume (MPV). This parameter has been associated with morbidity and mortality in HF. However, the role of platelets and the prognostic relevance of MPV in HFpEF remain largely unexplored. We aimed to evaluate the clinical usefulness of MPV as a prognostic marker in HFpEF. We prospectively enrolled 228 patients with HFpEF (79 ± 9 years; 66% females) and 38 controls of similar age and gender (78 ± 5 years; 63% females). All subjects underwent two-dimensional echocardiography and MPV measurements. Patients were followed-up for a primary end point of all-cause mortality or first HF hospitalization. The prognostic impact of MPV was determined using Cox proportional hazard models. Mean MPV was significantly higher in HFpEF patients compared with controls (MPV: 10.7 ± 1.1fL vs. 10.1 ± 1.1fL, p = .005). HFpEF patients (n = 56) with MPV >75th percentile (11.3 fL) displayed more commonly a history of ischemic cardiomyopathy. Over a median follow-up of 26 months, 136 HFpEF patients reached the composite endpoint. MPV >75th percentile was a significant predictor of the primary endpoint (HR: 1.70 [1.08; 2.67], p = .023) adjusted for NYHA class, chronic obstructive pulmonary disease, loop diuretics, renal function, and hemoglobin. We demonstrated that MPV was significantly higher in HFpEF patients compared with controls of similar age and gender. Elevated MPV was a strong and independent predictor of poor outcome in HFpEF patients and may be relevant for clinical use.

Insight into increased risk of portal vein thrombosis in nonalcoholic fatty liver disease

Nonalcoholic fatty liver disease (NAFLD) is one of the leading chronic liver diseases with increased morbidity and mortality rates for extrahepatic diseases (including cardiovascular disease, portal vein thrombosis, etc.). There is an increased risk of thrombosis in both the portal and systemic circulation in patients with NAFLD, independent of traditional liver cirrhosis. However, increased portal pressure, the most critical factor, is frequently observed in NAFLD patients, predisposing them to portal vein thrombosis (PVT). It has been reported that there is an 8.5% incidence of PVT among patients with non-cirrhotic NAFLD in a prospective cohort study. Based on the prothrombotic status of NAFLD itself, patients combined with cirrhosis may accelerate the development of PVT and lead to a poor prognosis. Moreover, PVT has been shown to complicate the procedure and adversely affect the outcome during liver transplantation surgery. NAFLD is in a prothrombotic state, and its underlying mechanisms have not been fully understood so far. Particularly noteworthy is that gastroenterologists currently overlook the higher risk of PVT in NAFLD. We investigate the pathogenesis of NAFLD complicated with PVT from the perspective of primary, secondary, and tertiary hemostasis, and also summarize relevant studies in humans. Some treatment options that may affect NAFLD and its PVT are also explored to improve patient-oriented outcomes.

The platelet to lymphocyte ratio in heart failure: a comprehensive review

Introduction. At the crossroads of heart failure (HF) and systemic inflammation, platelets and lymphocytes are both influenced as well as actively participating in the bidirectional relationship. The platelet to lymphocyte ratio (PLR) could therefore be a marker of severity. This review aimed to assess the role of PLR in HF. Methods. We searched the PubMed (MEDLINE) database using the keywords "platelet", "thrombocyte", "lymphocyte", "heart failure", "cardiomyopathy", "implantable cardioverter defibrillator", "cardiac resynchronization therapy" and "heart transplant". Results. We identified 320 records. 21 studies were included in this review, with a total of 17,060 patients. PLR was associated with age, HF severity, and comorbidity burden. Most studies reported the predictive power for all-cause mortality. Higher PLR was associated with in-hospital and short-term mortality in univariable analysis, however, it was not consistently an independent predictor for this outcome. PLR > 272.9 associated an adjusted HR of 3.22 (95%CI 1.56 - 5.68, p<0.001) for 30-day fatality. During long-term follow-up from 6 months to 5 years, PLR was an independent predictor of mortality in most studies, with cut-off values ranging from > 150 to > 194.97 and adjusted HR from 1.47 (95%CI 1.06 - 2.03, p=0.019) to 5.65 (95%CI 2.47-12.96, p<0.001). PLR > 173.09 had an adjusted OR 2.89 (95%CI 1.17-7.09, p=0.021) for predicting response to cardiac resynchronization therapy. PLR was not associated with outcomes after cardiac transplant or implantable cardioverter-defibrillator. Conclusion: Increased PLR could be an auxiliary biomarker of severity and survival prognosis in HF patients.

Predictive Biomarkers for Postmyocardial Infarction Heart Failure Using Machine Learning: A Secondary Analysis of a Cohort Study

Background

There are few biomarkers with an excellent predictive value for postacute myocardial infarction (MI) patients who developed heart failure (HF). This study aimed to screen candidate biomarkers to predict post-MI HF.

Methods

This is a secondary analysis of a single-center cohort study including nine post-MI HF patients and eight post-MI patients who remained HF-free over a 6-month follow-up. Transcriptional profiling was analyzed using the whole blood samples collected at admission, discharge, and 1-month follow-up. We screened differentially expressed genes and identified key modules using weighted gene coexpression network analysis. We confirmed the candidate biomarkers using the developed external datasets on post-MI HF. The receiver operating characteristic curves were created to evaluate the predictive value of these candidate biomarkers.

Results

A total of 6,778, 1,136, and 1,974 genes (dataset 1) were differently expressed at admission, discharge, and 1-month follow-up, respectively. The white and royal blue modules were most significantly correlated with post-MI HF (dataset 2). After overlapping dataset 1, dataset 2, and external datasets (dataset 3), we identified five candidate biomarkers, including FCGR2A, GSDMB, MIR330, MED1, and SQSTM1. When GSDMB and SQSTM1 were combined, the area under the curve achieved 1.00, 0.85, and 0.89 in admission, discharge, and 1-month follow-up, respectively.

Conclusions

This study demonstrates that FCGR2A, GSDMB, MIR330, MED1, and SQSTM1 are the candidate predictive biomarker genes for post-MI HF, and the combination of GSDMB and SQSTM1 has a high predictive value.

The influence of different rewetting procedures on the thrombogenicity of nanoporous poly(ether imide) microparticles

Nanoporous microparticles prepared from poly(ether imide) (PEI) are discussed as candidate adsorber materials for the removal of uremic toxins during apheresis. Polymers exhibiting such porosity can induce the formation of micro-gas/air pockets when exposed to fluids. Such air presenting material surfaces are reported to induce platelet activation and thrombus formation. Physical or chemical treatments prior to implantation are discussed to reduce the formation of such gas nuclei. Here, we report about the influence of different rewetting procedures - as chemical treatments with solvents - on the thrombogenicity of hydrophobic PEI microparticles and PEI microparticles hydrophilized by covalent attachment of poly(vinyl pyrrolidone) (PVP) of two different chain lengths.Autoclaved dry PEI particles of all types with a diameter range of 200 - 250 μm and a porosity of about 84% ±2% were either rewetted directly with phosphate buffered saline (24 h) or after immersion in an ethanol-series. Thrombogenicity of the particles was studied in vitro upon contact with human sodium citrated whole blood for 60 min at 5 rpm vertical rotation. Numbers of non-adherent platelets were quantified, and adhesion of blood cells was qualitatively analyzed by bright field microscopy. Platelet activation (percentage of CD62P positive platelets and amounts of soluble P-Selectin) and platelet function (PFA100 closure times) were analysed.Retention of blood platelets on the particles was similar for all particle types and both rewetting procedures. Non-adherent platelets were less activated after contact with ethanol-treated particles of all types compared to those rewetted with phosphate buffered saline as assessed by a reduced number of CD62P-positive platelets and reduced amounts of secreted P-Selectin (P < 0.05 each). Interestingly, the hydrophilic surfaces significantly increased the number of activated platelets compared to hydrophobic PEI regardless of the rewetting agent. This suggests that, apart from wettability, other material properties might be more important to regulate platelet activation. PFA100 closure times were reduced and within the reference ranges in the ethanol group, however, significantly increased in the saline group. No substantial difference was detected between the tested surface modifications. In summary, rewetting with ethanol resulted in a reduced thrombogenicity of all studied microparticles regardless of their wettability, most likely resulting from the evacuation of air from the nanoporous particles.

Antithrombotic Treatment in Cardiomyopathies

:

Cardiomyopathies are a heterogeneous group of heart muscle diseases and important cause of heart failure with reduced or preserved ejection fraction. Although there is an increasing body of evidence on the incidence, pathophysiology, and natural history of heart failure (HF) in cardiomyopathies, certain aspects of the therapeutic strategies remain unclear. More particularly, there is no consensus if to whether antithrombotic therapy has a favorable risk: benefit ratio in reducing thromboembolic event rate in patients with cardiomyopathies without suffering from primary valvular disease or atrial fibrillation. Although the observational data on increased venous thromboembolic risk are supported by multiple pathophysiological mechanisms, the role of antithrombotic therapy in these patients remains unclear. This review article provides an overview of epidemiologic, pathophysiologic, clinical, and therapeutic data for the prevention of thromboembolism in heart failure due to cardiomyopathies.

Analysis of mean platelet volume and red blood cell distribution width in recurrent epistaxis

Objectives

Recurrent epistaxis is one of the most common causes of emergency department visits. Although several localized and systemic conditions has been described, the exact cause is unknown in the majority of cases. In our study, we aimed to determine the effect of mean platelet volume (MPV) and red blood cell distribution width (RDW) levels on recurrent epistaxis.

Method

One hundred and thirty six patients with recurrent epistaxis and 170 healthy cases as control group were included in the study. Demographic data, vital signs and the results of complete blood counts were recorded. The patients who had clinical conditions that might affect the levels of MPV or RDW, were excluded. MPV and RDW levels were compared between the two groups.

Results

The median level of MPV was 7.6 fL (IQR25–75%: 7.1–8.4) in the study group and 8.2 fL (IQR25–75%: 7.8–8.9) in the control group (p < 0.001). The median levels of RDW were found in the patient and control groups in order %15.4 (IQR25–75%: 14.5–15.4) and %14.3 (IQR25–75%: 13.4–15.4) (p < 0.001). Systolic blood pressure, leukocyte count, age, sex, RDW and MPV levels that were variables with p levels<0.2, were included in the multivariate analyses. It was determined that high RDW levels increased epistaxis (p < 0.001; OR:1.89 [95% CI:1.53–2.33]) and high MPV levels decreased epistaxis (p < 0.001; OR:0.54 [95% CI:0.39–0.72]).

Conclusion

Low MPV and high RDW levels caused an increased bleeding tendency in patients with recurrent epistaxis. Although exact mechanism is not known, referring those patients for the assessment of etiologic causes would be proper.

Prognostic significance of mean platelet volume on admission in an unselected cohort of patients with non ST-segment elevation acute coronary syndrome

Mean platelet volume (MPV) has been proposed as a marker of platelet reactivity and cardiovascular risk. Its prognostic significance has not been thoroughly investigated in patients with non-ST elevation acute coronary syndrome (NSTE-ACS). We included 1,041 consecutive patients with NSTE-ACS. Patients were divided in quartiles according to the MPV value on admission (fl) i.e. Q1<7.5; Q2=7.5–8.0; Q3=8.1–8.8; Q4≥8.9. The primary study endpoint was the composite of cardiovascular death and re-myocardial infarction (MI) at one year. Secondary study endpoints were individual cardiovascular death and re-MI. Patients in Q4 were older, had a higher prevalence of previous MI, peripheral artery disease and advanced Killip class compared to patients in Q1-Q3. Elevated MPV levels (Q4) was independently associated with gender, smoking status, platelet count and creatinine level. Overall, 210 patients (20.2%) reached the primary endpoint, 124 (12.1%) died from cardiovascular causes and 125 (12.0%) suffered from re-MI. On multivariable analysis patients in Q4 were at higher risk of primary endpoint (HR=1.41; 95%CI 1.06–1.89; p=0.02) whilst the association with cardiovascular death and re-MI was attenuated. MPV as continuous variable was independently associated with both primary endpoint (HR=1.19; 95%CI 1.06–1.33; p=0.003) and cardiovascular death (HR=1.23; 95%CI 1.06–1.42, p=0.006). The incorporation of MPV into a comprehensive model of risk significantly increased the likelihood ratio chi-square for prediction of both the composite endpoint (p=0.004) and cardiovascular death (p=0.009). Therefore, MPV may be useful to improve risk stratification in NSTE-ACS patients and should be included in future prospective studies evaluating the role of platelet function in promoting cardiovascular events.

The Impact of Mean Platelet Volume (MPV) and JAK-2 Mutation on Thrombosis in Chronic Myeloproliferative Diseases

Thrombosis and bleeding are the main complications of chronic myeloproliferative diseases. Mean platelet volume (MPV) is an important indicator of the platelet activation. The aim of the present study was to assess the interrelationships between MPV, JAK-2 gene mutation and thromboembolic events in patients with ET and PV. Patients with ET (n = 60) and PV (n = 46) were compared to the secondary erythrocytosis group (n = 19); and a control group of age and sex matched healthy volunteers (n = 52). Besides demographic, clinical and laboratory data; thrombotic and hemorrhagic events were recorded for each patient. Platelet counts, MPV and JAK2 mutations were studied; and their relation with thromboembolic events were investigated using SPSS program for statistical analysis. There was no significant difference between groups regarding age (p = 0.188). Mean platelet count was significantly higher in ET group than other groups (p < 0.0001). Mean platelet count in PV group was significantly higher than control (p < 0.0001) and secondary erythrocytosis groups (p < 0.0001). In the ET group, MPV values were significantly lower than the control group and PV group. In the ET group, those with thromboembolia had lower platelet counts. There was no relation between MPV and thromboembolic event rate in PV, ET and secondary erithrocytosis groups; while no event was recorded in the control group. There was no relation between thromboembolic event rate and JAK 2 mutation. The association of JAK-2 mutation and high MPV especially in ET and PV groups does not contribute to the thromboembolic events.

Role of Antiplatelet Therapy and Anticoagulation in Nonischemic Cardiomyopathy

Heart failure continues to be a leading cause of morbidity and mortality throughout the United States. The pathophysiology of heart failure involves the activation of complex neurohormonal pathways, many of which mediate not only hypertrophy and fibrosis within ventricular myocardium and interstitium, but also activation of platelets and alteration of vascular endothelium. Platelet activation and vascular endothelial dysfunction may contribute to the observed increased risk of thromboembolic events in patients with chronic heart failure. However, current data from clinical trials do not support the routine use of chronic antiplatelet or oral anticoagulation therapy for ambulatory heart failure patients without other indications (atrial fibrillation and/or coronary artery disease) as the risk of bleeding seems to outweigh the potential benefit related to reduction in thromboembolic events. In this review, we consider the potential clinical utility of targeting specific pathophysiological mechanisms of platelet and vascular endothelial activation to guide clinical decision making in heart failure patients.

Role of Platelet Parameters on Neovascular Glaucoma: A Retrospective Case-Control Study in China

Purpose

Retinal vein occlusion (RVO) and diabetic retinopathy (DR) are two major sight-threatening diseases which may lead to neovascular glaucoma (NVG). The aim of this study was to explore the association between platelet parameters and NVG.

Methods

A total of 185 subjects were enrolled for the study from January, 2012 to December, 2015 at the Eye-ENT Hospital of Fudan University. Patients include those with NVG secondary to RVO (RVO group, n = 38), patients with NVG secondary to DR (DR group, n = 47), diabetics mellitus without retinopathy (DM group, n = 52), and healthy individuals (control group, n = 48). A complete ophthalmological examination including visual field examination, A-scan ultrasound, Fundus photography, and measurement of platelet parameters were performed for NVG subjects.

Results

There was no statistical difference in the mean age and gender among the RVO, DR, and control groups (p>0.05). The mean level of platelet distribution width (PDW) was higher (p<0.001) in the RVO group (15.16±2.13fl) and DR group (16.17±1.66fl) when compared with the control group (13.77±2.99fl). The mean plateletcrit (PCT) value of the RVO group (0.229±0.063%) was also higher (p = 0.049) than the control group (0.199±0.045). In the DR group, mean platelet volume (MPV) value (10.72±1.57fl) was significantly higher (p = 0.002) than the control group (9.75±0.89fl). A similar trend was observed when platelet parameters were compared among the 3 groups with respect to age. The mean level of PDW was significantly higher (p<0.001) in the DR group (16.17±1.66fl) compared with the DM group (13.80±3.32fl). Stepwise multiple logistic regression analysis revealed that PDW (OR = 1.44, 95%CI = 1.149–1.805, p = 0.002) and MPV (OR = 1.503, 95%CI = 1.031–2.192, p = 0.034) were associated with the DR group, PDW (OR = 1.207, 95%CI = 1.010–1.443, p = 0.039) and PCT (OR = 1.663, 95%CI = 1.870–2.654, p = 0.036) were associated with the RVO group.

Conclusion

Our results suggest that increased PDW and MPV are associated with the NVG secondary to DR group, elevated PDW and PCT are associated with the RVO group. It indicates that platelets might be an important factor in the onset and/or development of NVG.

Impact of Mean Platelet Volume on Long-Term Mortality in Chinese Patients with ST-Elevation Myocardial Infarction

We investigated the association between mean platelet volume (MPV) and risk of all-cause mortality in Chinese patients with ST-Elevation Myocardial Infarction (STEMI). We enrolled 1836 patients with STEMI in Xuanwu Hospital from January 2008 to December 2013. Based on MPV, patients were categorized into the following groups: <9.5 fL (n = 85), 9.5–11.0 fL (n = 776), 11.1–12.5 fL (n = 811) and >12.5 fL (n = 164), respectively. Mean duration of follow-up was 56.9 months, and 197 patients (10.7%) died during follow-up. All-cause mortality rates were compared between groups. The lowest mortality occurred in patients with MPV between 9.5–11.0 fL, with a multivariable-adjusted hazard ratio (HR) of 1.15(95%CI 0.62–1.50), 1.38(95%CI 1.20–1.68), and 1.72(95%CI 1.41–1.96) in patients with MPV of <.5, 11.1–12.5 and >12.5 fL, respectively. Therefore, increased MPV was associated with all-cause mortality in Chinese patients with STEMI. MPV might be useful as a marker for risk stratification in Chinese patients with STEMI.

A Central Role for Monocyte-Platelet Interactions in Heart Failure

Heart failure (HF) is an increasingly prevalent and costly multifactorial syndrome with high morbidity and mortality rates. The exact pathophysiological mechanisms leading to the development of HF are not completely understood. Several emerging paradigms implicate cardiometabolic risk factors, inflammation, endothelial dysfunction, myocardial fibrosis, and myocyte dysfunction as key factors in the gradual progression from a healthy state to HF. Inflammation is now a recognized factor in disease progression in HF and a therapeutic target. Furthermore, the monocyte-platelet interaction has been highlighted as an important pathophysiological link between inflammation, thrombosis, endothelial activation, and myocardial malfunction. The contribution of monocytes and platelets to acute cardiovascular injury and acute HF is well established. However, their role and interaction in the pathogenesis of chronic HF are not well understood. In particular, the cross talk between monocytes and platelets in the peripheral circulation and in the vicinity of the vascular wall in the form of monocyte-platelet complexes (MPCs) may be a crucial element, which influences the pathophysiology and progression of chronic heart disease and HF. In this review, we discuss the role of monocytes and platelets as key mediators of cardiovascular inflammation in HF, the mechanisms of cell activation, and the importance of monocyte-platelet interaction and complexes in HF pathogenesis. Finally, we summarize recent information on pharmacological inhibition of inflammation and studies of antithrombotic strategies in the setting of HF that can inform opportunities for future work. We discuss recent data on monocyte-platelet interactions and the potential benefits of therapy directed at MPCs, particularly in the setting of HF with preserved ejection fraction.

Comparison of platelet parameters in thrombocytopenic patients associated with acute myeloid leukemia and primary immune thrombocytopenia

Thrombocytopenia is caused by insufficient production and excessive destruction of platelets. Recent improvement of automated blood cell analyzers has allowed measurement of several platelet parameters, providing better understanding of the underlying mechanisms of thrombocytopenia. We investigated the significance of platelet parameters in thrombocytopenic patients. Thrombocytopenic patients (platelet <100 × 10/μl) who were newly diagnosed with acute myeloid leukemia and primary immune thrombocytopenia were enrolled, and platelet, mean platelet volume, platelet distribution width, platelet crit, mean platelet component, mean platelet mass, and large platelet count were measured, and the percentages of large platelets were calculated. The parameters were also measured in the reference population. The mean values of each parameter were as follows: platelet, 259 × 10/μl; mean platelet volume, 7.9 fl; platelet distribution width, 51.3%; platelet crit, 0.20%; mean platelet component, 26.0 g/dl; mean platelet mass, 1.9 pg; large platelet, 4.7 × 10/μl; large platelet percentage, 1.7%. In comparison with acute myeloid leukemia patients, patients with primary immune thrombocytopenia showed significantly higher mean platelet volume, platelet distribution width, mean platelet component, mean platelet mass, large platelet, and large platelet % (P < 0.05). Because of increased destruction of platelets, primary immune thrombocytopenia patients have increased mean platelet volume, platelet distribution width, mean platelet component, mean platelet mass, large platelet, and large platelet percentage compared with acute myeloid leukemia patients who have ineffective platelet production. Parameters measured by automated analyzer provide better understanding of thrombopoiesis in the bone marrow and the status of the peripheral blood in the clinical field.

Increased Formation of Monocyte-Platelet Aggregates in Ischemic Heart Failure

Background—

Cross-talk between monocytes and platelets is reflected by the formation of monocyte-platelet aggregates (MPAs). It is not known whether MPAs are affected in heart failure (HF), and we examined differences in patients with acute HF (AHF), stable HF (SHF), stable coronary artery disease (CAD) without HF, and healthy controls (HCs).

Methods and Results—

MPAs were analyzed by flow cytometry for the 3 monocyte subsets (CD14++CD16-CCR2+ [Mon1], CD14++CD16+CCR2+ [Mon2] and CD14+CD16++CCR2– [Mon3]) in patients with AHF (n=51), SHF (n=42), stable CAD (n=44), and HCs (n=40). Counts of total MPA and MPAs associated with Mon1 and Mon2 were significantly higher in AHF compared with SHF, CAD, and HCs ( P <0.001 for all). The proportion of Mon1 aggregated with platelets was increased in AHF compared with SHF ( P =0.033), CAD ( P <0.001), and HCs ( P <0.001). A higher percentage of Mon3 aggregated with platelets was also seen in AHF compared with SHF ( P =0.012) and HCs ( P <0.001) but not compared with CAD ( P =0.647). MPAs associated with Mon2 were significantly lower in patients who experienced adverse clinical outcomes of death or rehospitalization compared with those who remained free of events ( P =0.03). Mon2 count remained an independent negative predictor of combined death and rehospitalization after adjustment for age, left ventricular ejection fraction, creatinine, and brain natriuretic peptide (hazard ratio, 0.58 [95% CI, 0.34–0.98]; P =0.043).

Conclusions—

MPA formation in patients with both acute and stable HF is increased and seems to be confined to monocytes from Mon1 and Mon2 subsets. MPAs associated with Mon2 seem to be negatively predictive of a worse prognosis in AHF.

Aspirin resistance: current status and role of tailored therapy

Aspirin is integral in the primary and secondary prevention of coronary artery disease and acute coronary syndrome. Given the high clinical importance of aspirin in the management of coronary artery disease, much attention has been directed towards the concept of "aspirin resistance." Unfortunately, the term aspirin resistance is ill-defined in the literature, leading to a large variance in the reported prevalence of this phenomenon. In this review, the current understanding of aspirin resistance is discussed. Commonly used functional and diagnostic tests of platelet function, including their strengths and weakness, are reviewed. We next discuss several proposed mechanisms of aspirin resistance and special high-risk groups at risk for aspirin treatment failure. We then discuss optimal dosing and diagnostic strategies for those populations at risk for aspirin resistance with a focus on tailored aspirin therapy for high-risk groups. Finally, future topics of interest in the field of aspirin resistance are considered.

Significance of mean platelet volume on prognosis of patients with and without aspirin resistance in settings of non-ST-segment elevated acute coronary syndromes

Platelet volume is a marker of platelet function and activation. An elevated mean platelet volume (MPV) is associated with acute coronary syndromes (ACS). Recurrent cardiovascular events were found to be higher in patients with aspirin resistance. In this study, we investigated the effect of MPV on prognosis of patients with and without aspirin resistance by PFA-100 in settings of non-ST-segment elevated ACS. Two hundred and twenty patients with ACS were followed for an average of 14.86 +/- 5.93 months for the occurrence of death, myocardial infarction (MI) and revascularization. Aspirin effect on platelet function was assessed by PFA-100. According to MPV value and aspirin resistance status, patients were divided into four groups. Group 4 (with an elevated MPV and aspirin resistance) was significantly associated with worse prognosis for composite endpoint (death, MI and revascularization), death and MI (for all, log-rank P < 0.0001). Multivariate analysis showed that presence of an elevated MPV and aspirin resistance was an independent predictor of composite endpoint [hazard ratio 8.21, 95% confidence interval (CI) 3.48-19.35, P < 0.0001], death (hazard ratio 5.48, 95% CI 1.62-18.53, P = 0.006) and MI (hazard ratio 4.44, 95% CI 1.57-12.58, P = 0.005). Presence of an elevated MPV and aspirin resistance was significantly associated with death, MI and the composite endpoint, due to the lack of beneficial effect of aspirin on activated platelets. Patients with ACS, especially in the presence of an elevated MPV may benefit from the evaluation of aspirin resistance for risk stratification.

Mean platelet volume as a predictor of cardiovascular risk: a systematic review and meta-analysis

AIM

To determine whether an association exists between mean platelet volume (MPV) and acute myocardial infarction (AMI) and other cardiovascular events. Platelet activity is a major culprit in atherothrombotic events. MPV, which is widely available in clinical practice, is a potentially useful biomarker of platelet activity in the setting of cardiovascular disease.

METHODS AND RESULTS

We performed a systematic review and meta-analysis investigating the association between MPV and AMI, all-cause mortality following myocardial infarction, and restenosis following coronary angioplasty. Results were pooled using random-effects modeling. Pooled results from 16 cross-sectional studies involving 2809 patients investigating the association of MPV and AMI indicated that MPV was significantly higher in those with AMI than those without AMI [mean difference 0.92 fL, 95% confidence interval (CI) 0.67-1.16, P < 0.001). In subgroup analyses, significant differences in MPV existed between subjects with AMI, subjects with stable coronary disease (P < 0.001), and stable controls (P < 0.001), but not vs. those with unstable angina (P = 0.24). Pooled results from three cohort studies involving 3184 patients evaluating the risk of death following AMI demonstrated that an elevated MPV increased the odds of death as compared with a normal MPV (11.5% vs. 7.1%, odds ratio 1.65, 95% CI 1.12-2.52, P = 0.012). Pooled results from five cohort studies involving 430 patients who underwent coronary angioplasty revealed that MPV was significantly higher in patients who developed restenosis than in those who did not develop restenosis (mean difference 0.98 fL, 95% CI 0.74-1.21, P < 0.001).

CONCLUSIONS

Elevated MPV is associated with AMI, mortality following myocardial infarction, and restenosis following coronary angioplasty. These data suggest that MPV is a potentially useful prognostic biomarker in patients with cardiovascular disease. Whether the relationship is causal, and whether MPV should influence practice or guide therapy, remains unknown.

Association between plasma asymmetrical dimethylarginine activity and saphenous vein graft disease in patients with coronary bypass

BACKGROUND

Coronary vein graft disease is an important contributor to the morbidity after coronary artery bypass graft surgery. Graft occlusion is a serious complication, which limits the use of the saphenous vein as a coronary bypass conduit. Asymmetrical dimethylarginine (ADMA) is an endogenous inhibitor of nitric oxide synthase and it reduces the bioavailability of nitric oxide and begets endothelial dysfunction. The goal of this study was to examine the association between plasma ADMA activity and saphenous vein graft disease.

METHODS

One hundred and three patients were enrolled in this study. Group 1 consisted of 42 patients (13 female, 29 male) who had diseased saphenous vein grafts and group 2 consisted of 61 patients (10 female, 51 male) with nondiseased saphenous vein grafts. ADMA activity was measured by the enzyme-linked immunosorbent assay kit.

RESULTS

Mean ADMA activity in group 1 was significantly higher than in group 2 (2.0+/-0.6 vs. 1.1+/-0.5 micromol/l, P<0.001, respectively). Mean platelet volume was also significantly higher in group 1 than in group 2 (8.7+/-1.5 vs. 8.2+/-0.6 fl, P=0.03, respectively). In a multivariate linear regression analysis, ADMA activity (beta=2.902, P<0.001) and mean platelet volume (beta=0.595, P=0.03) were found to be independent predictors of saphenous vein graft disease.

CONCLUSION

Our results showed that ADMA activity was higher in patients with saphenous vein graft disease. Increased ADMA activity might lead to the acceleration of saphenous vein graft disease. ADMA may be a precious marker for detecting late saphenous vein graft patency.

Soluble, platelet-bound, and total P-selectin as indices of platelet activation in congestive heart failure

BACKGROUND

Many complications associated with congestive heart failure (CHF) have a thrombosis-related aetiology. Platelets play an important role in thrombogenesis, but it is not clear whether circulating platelets actively participate in thrombosis-related complications associated with CHF.

OBJECTIVE

To determine whether soluble P-selectin, platelet surface P-selectin, and total platelet P-selectin as indices of platelet activation in CHF patients-compared to 'disease controls' and 'healthy controls'-and to assess their prognostic value in CHF.

METHODS

We measured soluble P-selectin (sP-sel, by enzyme-linked immunosorbent assay, ELISA), total platelet P-selectin (pP-sel, by a novel 'platelet lysate' assay), platelet surface P-selectin (CD62P%G) and platelet surface CD63 (CD63%G) expression by flow cytometry-in 108 patients with stable congestive heart failure (all with left ventricular ejection fraction (LVEF) <50%). Levels were compared with 50 healthy controls and 70 'disease controls' (patients with coronary artery disease with normal left ventricular systolic function).

RESULTS

CHF patients and disease controls had higher sP-sel, CD62P%G and CD63%G than healthy controls. There were no significant correlations between sP-sel, pP-sel, CD62P%G and CD63%G with ejection fraction (all P>0.05). There were no differences in these markers when ischaemic and non-ischaemic aetiologies of CHF were compared. After a median follow-up of 490 days (range 340-535), there were 7 deaths, 15 hospitalizations for worsening heart failure, 1 for cardiac resynchronization therapy, 4 for revascularizations, 4 for myocardial infarctions, and 1 stroke. None of the platelet markers were predictive of the composite end-point at follow-up.

CONCLUSIONS

Patients with stable CHF exhibit evidence of abnormal platelet activation, despite usage of antiplatelet agents. These abnormalities did not determine prognosis and were broadly similar to those seen in 'disease controls' indicating that platelet abnormalities in CHF may simply be related to associated comorbidities.

The effects of maximal treadmill graded exercise testing on haemorheological, haemodynamic and flow cytometry platelet markers in patients with systolic or diastolic heart failure

BACKGROUND

Acute exercise has been associated with activation of thrombosis, and this risk may be accentuated in patients with heart failure. Given the relation of platelets to atherothrombosis, we tested the hypothesis that acute exercise would adversely affect platelet indices and platelet activation markers in patients with systolic and diastolic heart failure.

MATERIALS AND METHODS

We studied 20 patients with systolic heart failure (17 men, 3 women; mean age 64 +/- 10 years, all with ejection fraction (EF) < or = 40%) and 20 patients with diastolic heart failure (14 men, 6 women; mean age 64 +/- 8 years, mean EF = 66%) who were exercised to maximal intensity, who were compared to 13 healthy controls (6 men, 7 women; mean age 60 +/- 4 years, mean EF = 73%). We measured platelet indices (platelet volume, mass and component) and platelet activation markers (platelet-bound CD62P%G, CD63%G and CD40L%G using flow cytometry, as well as plasma sCD40L and soluble P-selectin (sP-sel) levels).

RESULTS

Baseline Mean Platelet Volume (MPV), sP-sel, CD40L%G and CD63%G levels were significantly higher in patients with systolic and diastolic heart failure, when compared with controls. The mean exercise duration and VO(2 )peak in patients with systolic and diastolic heart failure were not significantly different, but lower than that seen in healthy controls. Following exercise, mean haematocrit, CD62P%G, and CD63%G significantly increased in all three subject groups (all P < 0.05). The proportional change in CD62P%G and CD63%G were not significantly different between healthy controls and heart failure patients (P > 0.05).

CONCLUSION

Acute maximal graded exercise increases platelet activation markers, with no disproportionate differences between heart failure patients and healthy controls, despite the former group having a lower exercise tolerance and VO2 peak.

Platelet activation in acute, decompensated congestive heart failure

BACKGROUND

Congestive heart failure (CHF) is associated with increased risk of venous thromboembolism, stroke and sudden death. This may be related to abnormalities of thrombogenesis and platelet activation. A comprehensive assessment of platelet (dys)function in acute decompensated heart failure (AHF) is lacking, and we hypothesised that such patients would show greater abnormalities in platelet indices, compared to stable CHF and healthy controls.

METHODS

We measured soluble P-selectin (sP-sel, by ELISA); platelet surface P-selectin (CD62P%G) and CD63%G expression by flow cytometry; and platelet structural indices [mean platelet volume (MPV), mean platelet mass (MPM) and mean platelet component (MPC)] in 22 patients with AHF (pre- and posttreatment), who were compared to 68 patients with stable congestive heart failure (CHF, all with left ventricular ejection fraction (LVEF) <50%) and 23 healthy controls.

RESULTS

There were significant differences between the 3 study groups in MPV (p<0.001), MPC (p=0.001), platelet surface P-selectin (CD62P%G, p<0.0001) and platelet surface CD63P%G (p=0.017). On post-hoc analyses, AHF patients had higher platelet surface P-selectin (CD62P%G) compared to stable CHF patients and healthy controls (Tukey's test, all p<0.05), whilst CD63%P was similarly high in both disease groups, compared to healthy controls. Platelet surface P-selectin (p=0.032), CD63 (p=0.024) and CD40L (p=0.024) were significantly reduced following treatment of AHF, though platelet morphology and sP-sel levels were not significantly changed.

CONCLUSION

AHF patients demonstrate some abnormalities of platelet activation compared to stable CHF patients and healthy controls. These platelet abnormalities are modified by treatment, raising the possibility that platelets may partly contribute to the pathophysiology of adverse complications associated with AHF.

Relationship between Platelet Indexes and Coronary Angiographic Findings in Patients with Ischemic Heart Disease

To understand the mechanisms linking platelets to the risk of coronary artery disease, we investigated the relation between coronary angiographic morphology and platelet indexes--platelet count, mean platelet volume (MPV), platelet-large cell ratio (P-LCR) and platelet distribution width (PDW)--in patients with ischemic heart disease. Eighty-four patients with ischemic heart disease and 120 aged controls (AC) were enrolled in the study. The patients without any signs of acute myocardial infarction and acute coronary syndromes who underwent coronary angiography were divided into two groups, an 'angiographically negative group' (group 0) and an 'angiographically positive group' (group 1), with positive coronary obstruction depending on the diagnostic criteria in our hospital. Platelet indexes were measured in peripheral venous blood. The mean platelet counts were significantly lower in groups 1 and 0 than in AC (p = 0.0128 and p = 0.0041, respectively). MPV, P-LCR and the PDW were significantly higher in group 0 than in group 1 and AC (p = 0.0352 and 0.0433, p = 0.0059 and 0.0052, p = 0.00461 and 0.0146, respectively). The indexes of group 1 were almost the same compared with AC with respect to MPV, P-LCR and PDW. In conclusion, these findings suggest that the measurement of platelet indexes may reflect the underlying pathophysiological state and subsequent clinical events in the patients. In particular, lower P-LCR seems to identify patients with positive coronary angiography.

Relationship between Hemostatic Factors and the Platelet Index in Patients with Ischemic Heart Disease

To understand the heterogeneity of platelets, we investigated the correlation between hemostatic factors and the platelet index [platelet count, mean platelet volume (MPV), platelet-large cell ratio (P-LCR) and platelet distribution width (PDW)] in patients with ischemic heart disease (IHD). Ninety-seven patients with IHD and 120 aged controls (AC) were enrolled in the study. D-dimer, thrombin-antithrombin III complex (TAT), von Willebrand factor antigen (VWF:Ag) and platelet indexes were measured in the peripheral venous blood. The D-dimer and TAT levels in the patients were significantly elevated compared to the AC. VWF:Ag was also elevated, but not significantly so. However, no differences were observed in the platelet index between the patients and the AC. In the patients, the level of VWF:Ag was significantly inversely correlated with the platelet count, but such correlations were not observed in the D-dimer and TAT. TAT was significantly positively correlated with MPV, P-LCR and PDW. VWF:Ag was also correlated, though not significantly, with MPV, P-LCR and PDW. The D-dimer was not correlated with the platelet index. In the AC, the platelet count was inversely correlated with VWF:Ag, but not significantly so. VWF:Ag showed significant positive correlations with MPV, P-LCR and PDW. However, the D-dimer and TAT were not correlated with the platelet index in AC. These findings suggest that VWF:Ag and TAT seem to be profoundly related to platelet volume.

Antithrombotic therapy for congestive heart failure

Patients with congestive heart failure (CHF) are at increased risk of thromboembolic events. However, there is much debate and uncertainty over the use of antithrombotic therapy in these patients. The evidence for oral anticoagulation is limited, although large randomised trial data are forthcoming. Aspirin may be detrimental for heart failure due to a possible interaction with angiotensin-converting enzyme inhibitors, leading to increased hospitalisations from decompensated heart failure. The objective of this review article is to summarise the available evidence regarding the risk of stroke and thromboembolic events in CHF patients, as well as the effectiveness and risks of antithrombotic therapy in these patients.

Association Between Platelet Receptor Occupancy After Eptifibatide (Integrilin) Therapy and Patency, Myocardial Perfusion, and ST-Segment Resolution Among Patients With ST-Segment–Elevation Myocardial Infarction

Background— Paradoxically, fibrinolytic agents may systemically activate platelets, which in turn secrete plasminogen activator inhibitor (PAI-1), an antagonist of the fibrinolytic process in proportion to total body platelet mass. We hypothesized that improved epicardial patency, myocardial perfusion, and ST-segment resolution would be associated with higher levels of platelet receptor occupancy (RO) by a glycoprotein IIb/IIIa antagonist in ST-elevation MI (STEMI).

Methods and Results— Patients were drawn from the low-dose tenecteplase plus eptifibatide arm of the INTEGRITI study. Angiographic and platelet RO data were analyzed at 2 independent core laboratories. To take into account the absolute platelet count and receptors available for cross-linking, absolute platelet count was multiplied by percent of available receptors to obtain the index of the absolute number of receptors available (IANRA). Percent RO was higher among patients with a patent artery (TIMI flow grade 2/3; 78.2±9.2, n=63 versus 63.9±29.7, n=7; P =0.005), those with TIMI myocardial perfusion grade 2/3 (79.6±9.5, n=40 versus 73.0±16.2, n=30; P =0.036), and those with complete (≥70%) ST-segment resolution at 60 minutes (81.3±8.3%, n=27 versus 73.1±17.4%, n=24; P =0.034). The absolute number of glycoprotein IIb/IIIa receptors available for cross-linking was reduced (ie, the IANRA was lower) among patients with a patent artery ( P =0.0015), patients with TIMI myocardial perfusion grade 2/3 ( P =0.026), and patients with ≥70% ST-segment resolution ( P =0.029).

Conclusions— This study links restoration of epicardial flow, normal myocardial perfusion, and complete ST-segment resolution with higher levels of platelet glycoprotein IIb/IIIa receptor occupancy after therapy with eptifibatide administered with tenecteplase.

EPA, but not DHA, decreases mean platelet volume in normal subjects

The first indication of platelet activation is an increase in mean platelet volume (MPV). n-3 FA are known to inhibit platelet function and to reduce the risk for coronary heart disease. The purpose of this study was to determine the effects of EPA and DHA on MPV. Healthy subjects received olive oil placebo for 4 wk and then were randomly assigned to receive 4 g of ethyl esters of either safflower oil (n = 11), EPA (n = 10), or DHA (n = 12) for 4 wk. At the end of placebo run-in and treatment periods, MPV (fL; mean +/- SEM) and platelet count (PLT-CT; 10(3)/microL blood) were measured in the basal state and after ex vivo stimulation with collagen (10 microg/mL), cold (4 degrees C), and heat (37 degrees C). Unlike DHA, EPA lowered MPV as compared with safflower oil (7.2 +/- 0.1 vs. 7.5 +/- 0.1 fL; P < 0.05) and raised PLT-CT (211 +/- 18 vs.192 +/- 18 10(3)/microL; P < 0.05) in the fasting state. Collagen and cold significantly increased MPV whereas heat lowered MPV regardless of treatment. All stimuli decreased PLT-CT. EPA significantly increased platelet EPA (0.2 +/- 0.1 vs. 3.3 +/- 0.4%) and docosapentaenoic acid (DPA; 2.2 +/- 0.3 vs. 2.9 +/- 0.3%) concentrations, but not DHA. DHA treatment significantly increased DHA (1.4 +/- 0.2 vs. 4.1 +/- 0.5%) and DPA (2.0 +/- 0.4 vs. 3.0 +/- 0.4%) concentrations, but not EPA. In conclusion, EPA, but not DHA, reduces platelet activation, an early step in platelet aggregation.

Endogenous mediators and thrombophilia

Platelets are one of the most important components of primary haemostasis. Since they lack a nucleus, their functional characteristics are determined at the time of production. The role of platelets in thrombosis is further modified by the interaction with vascular mediators that are endogenously produced in response to a variety of stimuli. This chapter discusses the factors that influence platelet production, the interaction with endogenous mediators, and the potential therapeutic benefits achieved by modifying this interaction in the clinical setting.

Serotonin is associated with coronary artery disease and cardiac events

BACKGROUND

Blood platelets are related to coronary atherogenesis. Platelets secrete serotonin (5-hydroxytryptamine) which has several effects on the vascular wall and promotes thrombogenesis, mitogenesis, and proliferation of smooth muscle cells. Serotonin may therefore be one of the factors involved in the development of coronary artery disease (CAD). We have assessed serotonin among conventional predictors for CAD in patients undergoing coronary angiography for chest pain or clinically suspected angina pectoris.

METHODS AND RESULTS

Of 121 consecutive male patients (mean age 65, range 41 to 90 years) undergoing angiography, 96 had coronary artery stenosis and 25 had normal angiograms. Serotonin, blood platelet count, and conventional biochemical risk factors for CAD were determined in the morning the day before the angiography. High serotonin (cut-point 1000 nmol/L) was significantly associated with CAD with an odds ratio (OR) of 3.4 (95% confidence interval 1.2 to 9. 8). The corresponding OR for smokers was 4.8 (1.9 to 12.2); hypercholesterolemia (>7 mmol/L), 2.9 (1.1 to 7.6); high platelet count (cut-point 325 10(9)/L), 3.0 (1.0 to 9.5); and family history of heart disease, 2.3 (1.0 to 5.2). After adjustment with conventional risk factors, the OR for CAD was 3.8 (1.1 to 13.1), comparing high and low values of serotonin. The relation between serotonin and CAD was strengthened only when patients <70 years (n=82) were included in the analysis. In this age group, the occurrence of cardiac events during a mean of 3.7 years of follow-up was significantly associated with high serotonin values.

CONCLUSIONS

The study suggests that serotonin is associated with coronary artery disease and occurrence of cardiac events, particularly in younger age groups. This association seems to persist after adjustment for conventional risk factors.

Increased soluble platelet/endothelial cellular adhesion molecule-1 and osteonectin levels in patients with severe congestive heart failure. Independence of disease etiology, and antecedent aspirin therapy

BACKGROUND

Platelet-endothelial interactions modulated by adhesion molecules, may play an important role in the pathogenesis of congestive heart failure (CHF). Soluble levels of these molecules and platelet-derived substances are reportedly elevated in patients with CHF. However, no data are available on the plasma levels of Platelet/Endothelial Cell Adhesion Molecule-1 (PECAM-1), and platelet-derived osteonectin in this growing population.

METHODS AND RESULTS

Soluble levels by ELISA were prospectively determined in patients with severe CHF (n = 37) and correlated to etiology and antecedent aspirin use, and compared with 14 healthy control subjects. Left ventricular dysfunction was attributed to idiopathic dilated cardiomyopathy in 18 and coronary artery disease in 19 patients. Twenty-one patients were aspirin-free and 16 patients were using aspirin (81-500 mg daily). Elevated soluble PECAM-1 (51.31+/-2.44 ng/ml, P = 0.0001), and osteonectin (826.27+/-22.37 ng/ml, P = 0.0001) were observed in patients with CHF, as compared to healthy controls (32.56+/-1.21 ng/ml, and 478.02+/-31.32 ng/ml, respectively). Neither etiology of CHF, nor antecedent aspirin therapy significantly affects the levels of PECAM-1 or osteonectin.

CONCLUSIONS

Despite long-term aspirin therapy and independently of the etiology of the disease, soluble PECAM-1 and osteonectin were elevated in the majority of patients with severe CHF, suggesting platelet-endothelial activation. The present data provide additional evidence that more potent anti-platelet and endothelial preservation regimens deserve further study in the heart failure population.

Usefulness of soluble and surface-bound P-selectin in detecting heightened platelet activity in patients with congestive heart failure

P-selectin is an important marker of platelet activation and may be up-regulated in patients with congestive heart failure (CHF). We sought to prospectively compare simultaneously determined platelet and soluble P-selectin in patients with CHF and in healthy controls. Matched soluble levels by enzyme-linked immmunosorbent assay, and platelet-bound expression by whole blood flow cytometry of P-selectin were measured in 22 patients with CHF and compared with 14 healthy controls. Twelve patients were aspirin free and 10 patients were taking aspirin (81 to 500 mg/day). Patients with CHF had significantly elevated soluble P-selectin (186.6 +/- 82.7 ng/ml, p = 0.017) and more than twofold increased expression of platelet-bound P-selectin (9.58 +/- 7.16% of positive platelets, p = 0.021) compared with the P-selectin profile (102.6 +/- 29.0 ng/ml of plasma, and 4.06 +/- 1.21% of positive platelets, respectively) in controls. Aspirin therapy did not affect the P-selectin profile in patients with CHF. Despite antecedent aspirin therapy and interindividual variability of the P-selectin profile, soluble and platelet P-selectin were elevated in most patients with severe CHF, suggesting persistent platelet activation.

[Hydroxethyl starch: effects on hemostasis]

HES are high-polymeric glucose compounds obtained via hydrolysis and subsequent hydroxyethylation from the highly-branched amylopectin contained in maize. Initially, the HES were only characterized by their in vitro molecular weight (Mw), without consideration of the in vivo hydrolysis by alpha-amylase. The degree of substitution and the molar substitution ratio quantify the hydroxyethylation. The glucose units can be substituted at carbon 2, 3 and 6 leading to various substitution patterns. This pattern is described with the C2/C6 hydroxyethylation ratio. The higher the degree of substitution and the C2/C6 ratio, the less the starch is metabolized. The in vitro Mw, the degree of substitution and the C2/C6 ratio are the main determinants of the in vivo Mw which is clinically relevant. Haemorrhagic complications that occur after infusing larger volumes of HES can be avoided with a starch of low in vivo Mw. This is not only due to a lesser effect on the coagulation system which prevents an acquired type I von Willebrand syndrome, but also to a smaller decrease in platelet volume, since platelet volume and platelet function are positively correlated. In addition, HES with low in vivo Mw has significantly better rheological effects than HES with a high in vivo Mw, as high Mw macromolecules affect plasma viscosity negatively. Furthermore high Mw HES macromolecules lead to a distinctive decrease in fibronectin concentration that reflects saturation of the reticuloendothelial system. Another advantage of low in vivo Mw HES is its rather short half-life. Patients with an increased bleeding risk, microcirculatory disturbance or affected RES should receive HES with low in vivo Mw. In the future, HES should be mainly characterized by the in vivo and not the in vitro Mw.

Influence of intravascular molecular weight of hydroxyethyl starch on platelets

Complications concerning the blood coagulation have been observed repeatedly after administration of highly substituted, high molecular weight hydroxyethyl starch (HES), but it has not been examined as to how intravascular molecular weight and degree of substitution of HES influence platelet number and volume after repeated administration. Thirty patients with cerebrovascular diseases were treated for 10 days with hemodilution. 500 to 1500 ml of HES 200/0.62(n=10), HES 200/0.5(n=10) or HES 40/0.5(n=10) were infused daily. During the first days, the number of platelets was not lowered beyond the dilution effect, but at the end of the therapy the number of platelets had increased in all 3 groups beyond the initial value. Platelet volume was lowered significantly in the 3 groups. HES 200/0.62 caused the largest drop in platelet volume (-10%, p<0.01). A possible explanation could be that HES macromolecules are attached to platelets or are phagocytized by them. The larger platelets are then broken down and, to compensate the loss, more thrombocytes are released. A correlation between the molecular weight of HES and the breakdown rate of the platelets can be suspected, because HES 200/0.62 has the highest intravascular mean molecular weight(121 kD) and the largest effect on platelet volume.

Lowering of body temperature affects human platelet functions and norepinephrine release

The effect of lowering body temperature on plasma epinephrine, norepinephrine, and platelet density distribution and volume was studied in a placebo-controlled double-blind study. Lowering of body core temperature was induced by either exposure to a cold environment at a temperature of 5 degrees C (CT) or by a single dose of the 5-HT1A agonist ipsapirone (IPS). A third group exposed to an ambient temperature of 28 degrees C was given placebo (PLAC). All of the three groups were investigated in a climate chamber. In the CT group the density distribution of blood platelet subpopulations was shifted to an increase in less dense platelets that were more sensitive towards aggregation-inducing agents. The mean platelet volume in this subpopulation was decreased. Epinephrine was not affected, whereas the increase of norepinephrine was correlated with an increase of platelets that were more sensitive to aggregation-inducing agents in the CT group but not in the PLAC and IPS groups.

Platelet size in stroke patients

BACKGROUND AND PURPOSE

Large platelets are more reactive, produce more prothrombotic factors, and aggregate more easily. Platelet size can be readily estimated using automated analyzers, although accurate estimation depends on precise methodology. The disparate results from previous studies of mean platelet volume in cerebral ischemia may be explained by varying methodology. We have studied these variables using a precise methodology in an unselected group of stroke patients and compared them with data from age- and sex-matched control subjects.

METHODS

We studied 58 stroke patients consecutively admitted to a geriatric medical unit. Platelet variables were measured in the acute (< 48 hours after stroke) and chronic (> 6 months) phases of cerebral ischemia and compared with control variables. Control patients, admitted to the same unit, were of similar age and sex and without evidence of acute vascular events.

RESULTS

Mean platelet volume was higher in acute stroke (11.3 compared with 10.1 fL in control subjects; P < .001, Student's t test). In addition, platelet count was reduced in stroke patients (255 x 10(9)/L) compared with control subjects (299 x 10(9)/L; P < .01). Repeated measurements of mean platelet volume and platelet count in available survivors showed no significant change from the acute phase. Platelet changes did not relate to outcome measured at 6 months.

CONCLUSIONS

With the use of more precise methodology, these findings show that an increase in mean platelet volume and a reduction in platelet count are features of both the acute and nonacute phases of cerebral ischemia. It is possible that these changes precede the vascular event, and further studies are warranted.

Endogenous mediators and thrombophilia

Platelet function is a balance between factors determined at thrombopoiesis and prothrombotic and antithrombotic mediators from the vascular wall. Nitric oxide is a crucial vasodilator and inhibitor of platelet activation synthesized constitutively by the vascular endothelium. In some pathological states this synthesis may be impaired leading to a prothrombotic state. In other situations, synthesis may be increased by a second inducible enzyme. Nitric oxide synergizes with other antithrombotic vasodilators such as prostacyclin and is opposed by prothrombotic vasoconstrictor mediators such as thromboxane. Platelets are anucleate and their reactivity is partly determined at thrombopoiesis by their progenitor cell, the megakaryocyte. In thrombotic states, such as myocardial infarction, larger, more reactive platelets from larger megakaryocytes are observed.

Platelet function defects associated with hemorrhage or thrombosis

Platelet dysfunction, especially acquired forms, is a common cause of hemorrhage, especially when associated with trauma or surgery. Although the hereditary platelet function defects are generally quite rare, hereditary storage pool disease is common enough to be suspected in an individual, usually a child, with characteristic historical and clinical findings. The acquired platelet function defects, especially those resulting from drugs, are common and should promptly be suspected in patients developing easy and spontaneous bruising, mild-to-moderate mucosal membrane hemorrhage, or unexplained bleeding associated with trauma or surgery. The template bleeding time is generally useful as a screening test of platelet function, but a normal template bleeding time, in the face of a suggestive history, suggestive clinical findings, or in a patient frankly bleeding, is not reliable, and platelet aggregation or lumiaggregation should be done in appropriate clinical situations. Also, prolongation of the template bleeding time is an unreliable predictor of clinical bleeding propensity. The mainstay of therapy for almost all these defects, if bleeding is significant, is the liberal infusion of appropriate numbers of platelet concentrates. The acquired platelet function defects should also be managed by attempts to treat or control the underlying disease, if possible, and offending drugs or potentially offending drugs should immediately be stopped.

Platelet glycoprotein IIb-IIIa and size are increased in acute myocardial infarction

Platelet aggregation, which plays an important role in acute myocardial infarction (AMI), is mediated by fibrinogen binding to the platelet membrane glycoprotein (GP)IIb-IIIa (CD41). This study measured the relative number of GPIIb-IIIa complexes on platelets from patients immediately following AMI (n = 14) compared with those from controls (n = 14). Flow cytometry was used to demonstrate that there were, on average, 20% more GPIIb-IIIa complexes on platelets after AMI compared with controls. Platelet size was also 7% greater in AMI and it is known that larger platelets are more reactive. Since platelet size and protein content are determined at thrombopoiesis the majority of these platelets must have been circulating prior to AMI. Larger platelets, with more GPIIb-IIIa may, therefore, be causally related to AMI.