The effect of tirofiban on fibrinogen/agonist-induced platelet shape change and aggregation

Mean Platelet Volume: A Possible Predictor for Patients with Decompensated Chronic Heart Failure

Purpose

Despite all medical efforts and discoveries, heart failure (HF) remains one of the most important and common public health problems, with high mortality and hospitalization rates, due to decompensation of HF. In the present study, we aimed to identify a predictive factor through which we can evaluate the risk of readmission and mortality in the first year, given the initial admission of a patient with decompensated heart failure.

Patients and Methods

The parameter we have investigated is the mean platelet volume (MPV). Studies have shown that there is a significant correlation between the value of MPV and the risk of cardiovascular disease (CVD) and cardiovascular (CV) death. In this study, we enrolled 130 patients hospitalized for decompensated chronic HF (NYHA class IV HF or acute pulmonary edema) and analyzed whether there is a relationship between the value of the MPV at admission and 6-month rehospitalization, and 1-year mortality, respectively.

Results

The statistical analysis revealed significantly different values (p = 0.041) for MPV at admission between the group of patients without decompensated chronic HF compared to the group of patients with decompensated chronic HF (8.74 fl vs 9.08 fl). Also, the results of our study revealed that patients with decompensated chronic heart failure who were readmitted at 6 months and died at 1 year, respectively, had a higher MPV at admission (>9 fl), compared to those without the above-mentioned events, with a statistical significance.

Conclusion

A higher MPV at admission can be considered in our study as an independent predictor for rehospitalization and 1-year mortality of patients with decompensated chronic HF.

Mean platelet volume and mortality risk in a national incident hemodialysis cohort

BACKGROUND

Higher mean platelet volume (MPV) is an indicator of larger, reactive platelets, and has been associated with a higher risk of thrombosis and cardiovascular events in the general population. Hemodialysis patients have a higher risk for cardiovascular death and predisposition to platelet dysfunction (thrombosis and bleeding diathesis), but the relationship between MPV and mortality in this population is unknown.

METHODS

Among a 5-year cohort (1/2007-12/2011) of 149,118 incident hemodialysis patients from a large national dialysis organization, we examined the association between MPV and all-cause mortality. In primary analyses, we granularly analyzed MPV across five categories: 7.2-7.5, >7.5-9.5, >9.5-11.5, >11.5-13.5, and >13.5-15.0fL. In secondary analyses, we examined MPV categorized as low, normal, and high based on thresholds in the general population: 7.2-7.5, >7.5-11.5, and >11.5fL, respectively. Associations between baseline and time-dependent MPV with mortality were estimated using traditional and time-dependent Cox models in order to determine long-term and short-term exposure-mortality associations, respectively, using three adjustment levels: unadjusted, case-mix, and case-mix+laboratory models.

RESULTS

In primary analyses, higher baseline and time-dependent MPV levels were associated with incrementally higher death risk in case-mix+laboratory analyses (reference: >9.5-11.5fL). In secondary analyses, high baseline and time-dependent MPV levels were associated with higher mortality, whereas low MPV was associated with lower death risk across all multivariable models (reference: normal MPV).

CONCLUSIONS

Hemodialysis patients with higher MPV have heightened mortality risk. Further studies are needed to determine the pathophysiologic basis for the higher risk, and if modification of MPV ameliorates mortality in this population.

Radiolabeled tirofiban - a potential radiopharmaceutical for detection of deep venous thrombosis

Aim

The aim of this study was to investigate the possibility of using ^99mtechnetium (^99mTc)-labeled tirofiban (a reversible antagonist of glycoprotein IIb/IIIa) for detection of deep venous thrombosis (DVT) in rats without causing an antiplatelet effect.

Methods

The ability of in vitro tirofiban to inhibit adenosine 5′-diphosphate (ADP)-induced platelet aggregation was evaluated using optical aggregometer. Binding of ^99mTc-tirofiban to platelets was evaluated. Serum levels of unlabeled (a validated high performance liquid chromatography method) and ^99mTc-tirofiban after single intravenous injection were evaluated in male Wistar rats with or without induced DVT (femoral vein ligation model), and the rats were also subjected to whole body scintigraphy.

Results

Tirofiban in vitro inhibits ADP-induced aggregation of human platelets in a dose- and concentration-dependent manner (10 nM to 2 μM), but only if it is added before ADP and not after ADP. ^99mTc labeling did not affect the ability of tirofiban to bind to either human or rat platelets, nor did it affect tirofiban pharmacokinetics in intact rats or in animals with induced DVT. When ^99mTc-tirofiban was injected to rats after induction of DVT, at a molar dose lower than the one showing only a weak antiaggregatory effect in vitro, whole body scintigraphy indicated localization of ^99mTc-tirofiban around the place of the induced DVT.

Conclusion

^99mTc labeling of tirofiban does not affect its ability to bind to glycoprotein IIb/IIIa or its in vivo pharmacokinetics in rats, either intact or with DVT. A low, nonantiaggregatory dose of ^99mTc-tirofiban may be used to visualize DVT at an early stage.

Prognostic significance of mean platelet volume in diabetic patients with ST-elevation myocardial infarction

PURPOSE

Mean platelet volume (MPV) is a universally available parameter with routine blood counts. It has been linked to many cardiovascular risk factors. MPV is a marker of platelet size and activity and has been linked to poor prognosis following STEMI. There has been an increasing number of reports linking diabetes mellitus (DM) to platelet dysfunction. The aim of the study was to examine the association between admission MPV and clinical outcomes in patients with DM and STEMI undergoing primary percutaneous coronary intervention (PCI). The secondary objective of the study was to evaluate whether this index can be used to determine the long-term prognosis.

METHODS

A total of 1,557 patients with STEMI undergoing primary PCI were enrolled and divided into two groups depending on their diabetes mellitus status: Group 1 - patients with diabetes mellitus (N=539) and Group 2 - patients without diabetes mellitus (N=1018).

RESULTS

MPV and peak CK-MB concentration were higher in diabetic patients as compared to non-diabetic patients. In diabetic patients, MPV was positively correlated with admission Killip class and negatively correlated with time to death during follow-up, initial TIMI flow, final TIMI flow, and erythrocyte count. In non-diabetic patients, MPV was positively correlated with the number of diseased coronary arteries, admission Killip class, and negatively correlated with time to death during follow-up and initial TIMI flow. ROC analysis revealed high diagnostic value of MPV in predicting in-hospital and one-year mortality. MPV cut-off level was lower for diabetic patients compared to non-diabetic patients.

CONCLUSIONS

Diabetic patients had higher MPV than non-diabetic patients. Both in diabetic and non-diabetic patients MPV proved to have good prognostic value for in-hospital and late mortality. MPV cut-off value for predicting mortality was lower in diabetic patients. Mortality rate was the highest in the fourth quartiles of MPV in both study groups.

Acute Effects of Intracoronary Tirofiban on No-Reflow Phenomena in Patients With ST-Segment Elevated Myocardial Infarction Undergoing Primary Percutaneous Coronary Intervention

We evaluated the acute effect of intracoronary administration of tirofiban on no-reflow phenomenon in patients with ST-segment elevated myocardial infarction undergoing primary percutaneous coronary intervention. Consecutive patients (n = 162) were randomized into 2 groups based on whether intracoronary tirofiban was administered. After the administration of intracoronary tirofiban, thrombolysis in myocardial infarction (TIMI) flow grade significantly increased ( P < .001) and successful reperfusion was achieved in 26 (32%) patients. In the placebo group, however, after the administration of intracoronary placebo the TIMI flow grade did not change ( P = .070), and successful reperfusion was achieved only in 8 (10%) patients. In-hospital major adverse cardiac events (MACE) were significantly lower in the tirofiban group (36% vs 19%, P = .013). Intracoronary administration of tirofiban significantly improves TIMI flow grade and is associated with a lower in-hospital rate of MACE.

Effects of Upstream Administration of Tirofiban Before Percutaneous Coronary Intervention on Spontaneous Reperfusion and Clinical Outcomes in Acute ST-Segment Elevation Myocardial Infarction

We assessed the effects of upstream administration of the glycoprotein IIb/IIIa inhibitor tirofiban before percutaneous coronary intervention (PCI) on spontaneous reperfusion (SR) of infarct-related artery (IRA) and the clinical outcomes in patients with ST-segment elevation myocardial infarction (STEMI). The incidence of SR of the IRA was significantly higher in the tirofiban group than in the no-tirofiban group (141 [36.5%] vs 21 [17.2%], P < .001). By multivariate logistic regression analysis, use of tirofiban (odds ratio 2.32, 95% confidence interval 1.25-4.31, P = .008) independently predicted the occurrence of SR. Kaplan-Meier survival analysis demonstrated that major adverse cardiovascular event-free survival was significantly higher in patients treated with tirofiban than in patients without tirofiban at 30-day (log rank = 11.65, P = .001) and 90-day follow-up (log rank = 16.79, P < .001). Upstream administration of tirofiban is significantly associated with increased SR of the IRA and favorable clinical prognosis in patients undergoing PCI for STEMI.

Predictive Value of Admission Platelet Volume Indices for In-hospital Major Adverse Cardiovascular Events in Acute ST-Segment Elevation Myocardial Infarction

Although mean platelet volume (MPV) is an independent correlate of impaired angiographic reperfusion and 6-month mortality in ST-segment elevation myocardial infarction (STEMI) treated with primary percutaneous coronary intervention (pPCI), there is less data regarding the association between platelet distribution width (PDW) and in-hospital major adverse cardiovascular events (MACEs). A total of 306 patients with STEMI pPCI were evaluated. No reflow was defined as a post-PCI thrombolysis in myocardial infarction (TIMI) flow grade of 0, 1, or 2 (group 1). Angiographic success was defined as TIMI flow grade 3 (group 2). The values of MPV and PDW were higher among patients with no reflow. In-stent thrombosis, nonfatal myocardial infarction, in-hospital mortality, and MACEs were significantly more frequent among patients with no reflow. In multivariate analysis, PDW, MPV, high-sensitivity C-reactive protein, and glucose on admission were independent correlates of in-hospital MACEs. Admission PDW and MPV are independent correlates of no reflow and in-hospital MACEs among patients with STEMI undergoing pPCI.

Plant extracts inhibit ADP-induced platelet activation in humans: their potential therapeutic role as ADP antagonists

Adenosine diphosphate (ADP) plays a pivotal role in platelet activation. Platelet hyperactivity is associated with vascular disease and also has a key role in haemostasis and thrombosis. ADP activates platelets through three purinoceptor subtypes, the G(q)-coupled P2Y(1) receptor, G(i)-coupled P2Y(12) receptor and P2X(1) ligand-gated cation channel. Platelet ADP purinergic receptors are therefore suitable targets for antiplatelet drugs. Thienopyridines such as clopidogrel and ticlopidine, as well as other ADP receptor antagonists like prasugrel, ticagrelor, cangrelor and elinogrel have demonstrated clinical benefits via the inhibition of the selective purinergic ADP receptor, P2Y(12). However, they still have limitations in their mode of action and efficacy, like increased risk of bleeding. Thus, the ongoing pursuit to develop newer and more effective antiplatelet agents continues. There is a growing interest in the purinergic antiplatelet properties exhibited by plant extracts. This article considers the following: pomolic acid isolated from Licania pittieri, brazilin isolated from the heartwood of Caesalpinia sappan L, phylligenin isolated from the twigs of Muraltia vulpina, bark oil of Gonystylus velutinus, seed and bark extracts from Aesculus hippocastanum L. and red wine phenolics and catechins isolated from green tea. Moreover, the method used to investigate platelet purinergic receptors should be considered, since using a more sensitive, high-resolution platelet sizer can sometimes detect platelet variations when the light transmission method was not able to do so. The exact mechanisms by which these plant extracts work need further investigation. They all however inhibit ADP-induced activation in human platelets. This could explain, at least in part, the protective effect of plant extracts as antiplatelet agents.

A new rapid method to measure human platelet cholesterol: a pilot study

INTRODUCTION

Platelet cholesterol (PC) could be used to assess "tissue" cholesterol of patients with vascular disease. However, the methods available so far to measure PC involve a complex extraction process. We developed a rapid method to measure PC and assessed its correlation with serum total cholesterol (TC), low-density lipoprotein cholesterol (LDL-C), high-density lipoprotein cholesterol (HDL-C), LDL-C/HDL-C ratio, triglycerides (TG), and non-HDL-C.

METHODS

We assessed repeatability (20 times, 3 participants) and reproducibility (8 times, 2 participants). A group of 47 healthy participants was studied. Blood was collected to analyze serum TC, LDL-C, HDL-C, and TG. Citrated blood was used to prepare a platelet pellet. A "clear soup" was produced (by disrupting this pellet using freeze-thaw and sonication cycles) and used to measure PC.

RESULTS

Repeatability of PC showed a coefficient of variation (CV) of 4.8%. The reproducibility of PC over a period of 2 months was CV 7.5% and 8.1% (8 measurements for 2 participants). The PC of participants with serum LDL-C >2.6 mmol/L (treatment goal recommended by the National Cholesterol Education Program Adult Treatment Panel III) was 377 ± 120 μmol/10(12) platelets (n = 25). There was a significant correlation (Spearman, correlation coefficient) of PC (n = 25) with serum LDL-C (r(s) = 0.45, P = .02), LDL-C/HDL-C (r(s) = 0.45, P = .02), TG (r(s) = 0.43, P = .03), and non-HDL-C (r(s) = 0.53, P = .007).

CONCLUSION

This technique of measuring PC has the advantage of being reproducible, fast, and simpler than previous methods. Thus, it may be useful for multiple sampling when investigating changes in PC in hypercholesterolemic patients. More extensive evaluation is necessary.