Victor L. Serebruany

Standardized Bleeding Definitions for Cardiovascular Clinical Trials A Consensus Report From the Bleeding Academic Research Consortium

Advances in antithrombotic therapy, along with an early invasive strategy, have reduced the incidence of recurrent ischemic events and death in patients with acute coronary syndromes (ACS; unstable angina, non–ST-segment–elevation myocardial infarction [MI], and ST-segment–elevation MI).1,–,4 However, the combination of multiple pharmacotherapies, including aspirin, platelet P2Y12 inhibitors, heparin plus glycoprotein IIb/IIIa inhibitors, direct thrombin inhibitors, and the increasing use of invasive procedures, has also been associated with an increased risk of bleeding. Editorial see p 2664 Bleeding complications have been associated with an increased risk of subsequent adverse outcomes, including MI, stroke, stent thrombosis, and death, in patients with ACS and in those undergoing percutaneous coronary intervention (PCI),5,–,10 as well as in the long-term antithrombotic setting.11,12 Thus, balancing the anti-ischemic benefits against the bleeding risk of antithrombotic agents and interventions is of paramount importance in assessing new therapies and in managing patients. Prior randomized trials comparing antithrombotic agents suggest that a reduction in bleeding events is associated with improved survival.13,14 Because prevention of major bleeding may represent an important step in improving outcomes by balancing safety and efficacy in the contemporary treatment of ACS, bleeding events have been systematically identified as a crucial end point for the assessment of the safety of drugs during the course of randomized clinical trials, and are an important aspect of the evaluation of new devices and interventional therapies.15 Unlike ischemic clinical events (eg, cardiac death, MI, stent thrombosis), for which there is now general consensus on end-point definitions,16,17 there is substantial heterogeneity among the many bleeding definitions currently in use. Lack of standardization makes it difficult to optimally organize key clinical trial processes such as adjudication, and even more difficult to interpret relative …

Lack of Adverse Clopidogrel-Atorvastatin Clinical Interaction From Secondary Analysis of a Randomized, Placebo-Controlled Clopidogrel Trial

Background—Statins primarily metabolized by cytochrome P450 3A4 (CYP3A4) reportedly reduce clopidogrel’s metabolism to active metabolite, thus attenuating its inhibition of platelet aggregation ex vivo. However, the clinical impact of this interaction has not been evaluated. Methods and Results—Clopidogrel for the Reduction of Events During Observation (CREDO) was a double-blind, placebo-controlled, randomized trial comparing pretreatment (300 mg) and 1-year (75 mg/d) clopidogrel therapy (clopidogrel) with no pretreatment and 1-month clopidogrel therapy (75 mg/d) (control) after a planned percutaneous coronary intervention. All patients received aspirin. The 1-year primary end point was a composite of death, myocardial infarction, and stroke. We performed a post hoc analysis to evaluate the clinical efficacy of concomitant clopidogrel and statin administration, categorizing baseline statin use to those predominantly CYP3A4-metabolized (atorvastatin, lovastatin, simvastatin, and cerivastatin) (CYP3A4-MET) or others (pravastatin and fluvastatin) (non-CYP3A4-MET). Of the 2116 patients enrolled, 1001 received a CYP3A4-MET and 158 a non-CYP3A4-MET statin. For the overall study population, the primary end point was significantly reduced in the clopidogrel group (8.5% versus 11.5%, RRR 26.9%; P =0.025). This clopidogrel benefit was similar with statin use, irrespective of treatment with a CYP3A4-MET (7.6% clopidogrel, 11.8% control, RRR 36.4%, 95% CI 3.9 to 57.9; P =0.03) or non-CYP3A4-MET statin (5.4% clopidogrel, 13.6% control, RRR 60.6%, 95% CI −23.9 to 87.4; P =0.11). Patients given atorvastatin or pravastatin had similar 1-year event rates. Additionally, concomitant therapy with statins had no impact on major or minor bleeding rates. Conclusions—Although ex vivo testing has suggested a potential negative interaction when coadministering a CYP3A4-metabolized statin with clopidogrel, this was not clinically observed statistically in a post hoc analysis of a placebo-controlled study.

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.

Role of soluble and platelet-bound P-selectin in discriminating cardiac from noncardiac chest pain at presentation in the emergency department

BACKGROUND It has been reported that selectins participate in the pathogenesis of acute coronary syndromes by modulating platelet-leukocyte-endothelium interactions. Elevated P-selectin level also has been observed in the clinical setting of myocardial ischemia and reperfusion; however, its utility in differentiating cardiac from noncardiac origins of chest pain is unknown. METHODS AND RESULTS Soluble and platelet fractions of P-selectin were measured for 122 patients with chest pain and 14 healthy persons acting as controls. Patients with a cardiac problem (unstable angina, congestive heart failure, acute myocardial infarction) had significantly elevated levels of soluble P-selectin (156.0 +/- 58.8 ng/mL, P =.002) and platelet-bound P-selectin (11.7% +/- 6.4% positive cells, P =.013) compared with the P-selectin profile among controls (102.6 +/- 29.0 ng/mL, 4.1% +/- 1.2% positivity) and among patients with noncardiac chest pain (114.7 +/- 36.6 ng/mL, 5.7% +/- 2.9% positivity). With a cutpoint of 10% positivity for membrane and 120 ng/mL for soluble P-selectin, the sensitivities were 0.442 and 0. 558, and the specificities were 0.915 and 0.553. CONCLUSIONS When a patient arrives in the emergency department, measurement of membrane P-selectin may serve as an additional diagnostic tool to detect heightened platelet activity, which is most prevalent among patients with a cardiac origin of chest pain. However, low sensitivity limits the utility of the P-selectin profile alone in suitably differentiating acute coronary syndromes within the overall population of patients with chest pain.

The in-vitro effects of E5555, a protease-activated receptor (PAR)-1 antagonist, on platelet biomarkers in healthy volunteers and patients with coronary artery disease

E5555 is a potent protease-activated receptor (PAR-1) antagonist targeting the G-coupled receptor and modulating thrombin-platelet-endothelial interactions. The drug is currently being tested in phase II trials in patients with coronary artery disease (CAD) and has potential antithrombotic and anti-inflammatory benefits. We investigated the in-vitro effects of E5555 on platelet function beyond PAR-1 blockade in healthy volunteers and CAD patients treated with aspirin (ASA) with or without clopidogrel. Conventional aggregation induced by 5 microM ADP, 1 microg/ml collagen, 10 microM TRAP, whole blood aggregation with 1 microg/ml collagen, and expression of 14 intact, and TRAP-stimulated receptors by flow cytometry were utilised to assess platelet activity after preincubation with escalating concentrations of E5555 (20 ng/ml, 50 ng/ml, and 100 ng/ml) in healthy volunteers, CAD patients treated with ASA, and CAD patients treated with ASA and clopidogrel combination (n=10, for each group). E5555 inhibited a number of platelet biomarkers. Platelet inhibition was usually moderate, present already at 20 ng/ml, and was not seemingly dose-dependent without TRAP stimulation. E5555 caused 10-15% inhibition of ADP- and collagen-induced platelet aggregation in plasma, but not in whole blood. TRAP-induced aggregation was inhibited almost completely. PECAM-I, GP IIb/IIIa antigen, and activity with PAC-1, GPIb, thrombospondin, vitronectin receptor expression, and formation of platelet-monocyte aggregates were also significantly reduced by E5555. TRAP stimulation caused dose-dependent effects between 20 and 50 ng/ml E5555 doses. P-selectin, LAMP-1, LAMP, and CD40-ligand were not affected by E5555. In conclusion, E5555 in vitro moderately but significantly inhibits platelet activity beyond PAR-1 blockade. Antiplatelet potency of ASA alone, and the combination of ASA and clopidogrel may be enhanced by E5555 providing rationale for their synergistic use. Selective blockade of platelet receptors suggests unique antiplatelet properties of E5555 as a potential addition to current antithrombotic regimens.

Baseline platelet activity and response after clopidogrel in 257 diabetics among 822 patients with coronary artery disease.

The objective was to describe the indices of platelet aggregation and activation in a large cohort of diabetic patients with coronary artery disease (CAD). Recently, a number of observations have indicated that patients with diabetes mellitus (DM) exhibit persistent platelet activation, and low response after antiplatelet therapy, although no randomized data exist. We sought to define the baseline platelet biomarkers, and the patterns of response to aspirin and clopidogrel therapy in DM versus non-diabetic patients. Secondary post-hoc analyses were made of platelet activity biomarkers in the dataset which consisted of patients with documented CAD (n = 822), including those with DM (n = 257). Patients with DM exhibited higher baseline platelet activity by adenosine diphosphate (ADP)- (p = 0.0002), and collagen-induced (p = 0.03) aggregometry; Ultegra- (p = 0.0001), and PFA-100 (p = 0.02) analyzers; and expression of platelet/endothelial cell adhesion molecule-1 (PECAM-1) (p = 0.01), glycoprotein (GP) IIb/IIIa antigen (p = 0.001), and activity (p = 0.02), vitronectin receptor (p = 0.03), P selectin (p = 0.02), and intact epitope of PAR-1 thrombin receptor (p = 0.02). Antiplatelet response after clopidogrel in diabetics was impaired when compared with non-diabetics. In conclusion, diabetic patients exhibit high pretreatment platelet activity, and do not respond well to the available antiplatelet regimens when compared with similar patients without DM. The clinical implications of these findings are unknown but are potentially important. Considering worsened outcomes in this high-risk population, clinical trials in DM are urgently needed in order to define the optimal degree of platelet inhibition and suitability for more aggressive antiplatelet regimens.

Assessing aspirin responsiveness in subjects with multiple risk factors for vascular disease with a rapid platelet function analyzer

Aspirin, compared with placebo, reduces the risk of cardiovascular events by 25% in populations of patients with and without known arterial vascular disease. However, the phenomena of ‘aspirin resistance’ that has been described in 5–50% of this population may critically reduce aspirins efficacy. One study has suggested that aspirin-resistant patients have a 3.5 times higher risk of cardiovascular death. Presently, there are no established, simple, broadly used methods determining antiplatelet properties of aspirin, while conventional aggregometry requires special equipment and trained personnel. We sought to determine the validity of an Ultegra analyzer with the novel aspirin-sensitive cartridge before and after one pill of non-enteric coated aspirin (325 mg) in subjects with multiple risk factors for coronary artery disease. One hundred and fifty-four volunteers were enrolled into the multicenter study, but six of them were excluded. Data from 148 participants were analyzed. Platelets were assessed twice at baseline (pre-aspirin), and after 2–30 h (post-aspirin). We employed 5 μmol/l epinephrine-induced conventional aggregometry, and aspirin response units stimulated by propyl gallate with the point-of-care Ultegra analyzer. A single pill of aspirin reduced platelet-rich plasma aggregation from 72 ± 21% to 25 ± 10%, and diminished aspirin reduction units from 647 ± 95 to 436 ± 69. The overall agreement between the two methods was 87% with 85% sensitivity for Ultegra and 88% for platelet aggregation, respectively. The correlation between the two methods was 0.902. Timely determination of aspirin resistance represents an indispensable application in current medicine. The Ultegra RPFA-ASA analyzer is a novel, fast method that could be used in clinical practice for monitoring efficacy of aspirin, and for triaging the aspirin-resistant population. The clinical implications of these data need to be proven in randomized trials.

Viewpoint: paradoxical excess mortality in the PLATO trial should be independently verified.

The PLATO trial revealed excess all-cause (4.5%) and vascular (4.0%) mortality after experimental pyrimidine, ticagrelor, and even higher death rates (5.9% and 5.1%, respectively) after clopidogrel, which have never been seen in any previous acute coronary syndrome (ACS) trial. The Food and Drug Administration (FDA) conducted, and recently released the ticagrelor review outlining some paradoxical mortality patterns in PLATO, including the existence of alive patient, who initially was reported dead. The drug was recently approved in Europe, but repeatedly delayed in the USA. The objective of this viewpoint article was to evaluate extremely high death rates in PLATO by scrutinising FDA-released evidence, and comparing mortality patterns in recent ACS trials. These data were first presented as the analytical report submitted to the FDA on October 26, 2010. The available evidence suggest that mortality rates in PLATO, so as death benefit of ticagrelor over clopidogrel are extreme, despite incomplete follow-up, short duration of the trial, frequent preloading with clopidogrel, and gross mismatch between conventional average myocardial infarction rates but disproportionally frequent vascular fatalities, and heavily imbalanced sepsis-related deaths. In contrast to the overall PLATO results, the deaths rates in the USA were much lower (3.2% vs. 3.8%) not only favouring clopidogrel, but more importanly matching very well with identical rates in TRITON (3.2%), and one-year ACUITY (3.6%-3.9%) fatalities. Since the «play of chance» cannot explain these discrepancies due to excess death rates in both PLATO arms, and considering that study sponsor self-monitored sites in most countries, but not in the USA, the mortality data are questionable, and should be independently virified. It was concluded that excess mortality rates and delayed timing of the benefit onset in PLATO do not match with any recent ACS trial, and do not look natural. Reevaluation of the survival, especially driven from the several high-volume sponsor monitored sites in Eastern Europe may reveal discrepancies between those reported in PLATO and actual vital records. Future practice of self monitoring in pivotal indication-seeking clinical trials should be completely banned.

Neuro-Glial and Systemic Mechanisms of Pathological Responses in Rat Models of Primary Blast Overpressure Compared to “Composite” Blast

A number of experimental models of blast brain injury have been implemented in rodents and larger animals. However, the variety of blast sources and the complexity of blast wave biophysics have made data on injury mechanisms and biomarkers difficult to analyze and compare. Recently, we showed the importance of rat position toward blast generated by an external shock tube. In this study, we further characterized blast producing moderate traumatic brain injury and defined “composite” blast and primary blast exposure set-ups. Schlieren optics visualized interaction between the head and a shock wave generated by external shock tube, revealing strong head acceleration upon positioning the rat on-axis with the shock tube (composite blast), but negligible skull movement upon peak overpressure exposure off-axis (primary blast). Brain injury signatures of a primary blast hitting the frontal head were assessed and compared to damage produced by composite blast. Low to negligible levels of neurodegeneration were found following primary blast compared to composite blast by silver staining. However, persistent gliosis in hippocampus and accumulation of GFAP/CNPase in circulation was detected after both primary and composite blast. Also, markers of vascular/endothelial inflammation integrin alpha/beta, soluble intercellular adhesion molecule-1, and L-selectin along with neurotrophic factor nerve growth factor-beta were increased in serum within 6 h post-blasts and persisted for 7 days thereafter. In contrast, systemic IL-1, IL-10, fractalkine, neuroendocrine peptide Orexin A, and VEGF receptor Neuropilin-2 (NRP-2) were raised predominantly after primary blast exposure. In conclusion, biomarkers of major pathological pathways were elevated at all blast set-ups. The most significant and persistent changes in neuro-glial markers were found after composite blast, while primary blast instigated prominent systemic cytokine/chemokine, Orexin A, and Neuropilin-2 release, particularly when primary blast impacted rats with unprotected body.

Hemostatic abnormalities in patients with congestive heart failure: diagnostic significance and clinical challenge

Knowledge of the pathogenesis of congestive heart failure (CHF) has improved greatly in recent years. However, this disease continues to cause one of the highest morbidities and mortalities in the Western world. The pathophysiology of heart failure is complex and much of our understanding revolves strictly around the neurohormonal mechanisms involved. Various pharmacologic interventions have significantly improved morbidity and include ACE inhibitors, beta-blockers, diuretics, and inotropic agents. Yet, no consensus has been reached regarding the use of anticoagulants or antiplatelet agents. It has been suggested that CHF is associated with altered hemostasis, but whether this prothrombotic state contributes to the pathogenesis and progression of the disease is unknown. The purpose of this review article is to discuss our current knowledge of platelet activation, thrombin generation, fibrinolysis, and endothelial dysfunction in CHF patients, and the potential role of anticoagulants and/or antiplatelet agents in preventing these hemostatic abnormalities.