Clinical Outcomes Comparing Eptifibatide and Abciximab in ST Elevation Acute Myocardial Infarction Patients Undergoing Percutaneous Coronary Interventions

BACKGROUND

Randomized clinical trials comparing glycoprotein IIb-IIIa inhibitors have largely excluded patients with ST segment elevation myocardial infarction (STEMI).

METHODS

We conducted an open-label, sequential comparison of in-hospital and 6-month clinical outcomes in STEMI patients receiving eptifibatide or abciximab as adjunctive therapy during percutaneous coronary intervention (PCI). Registry data were collected and compared for STEMI patients undergoing PCI and receiving eptifibatide or abciximab over a 3.5-year period. Six-month follow-up, using telephone interviews, included major adverse cardiac events and functional status.

RESULTS

Baseline characteristics were similar for patients receiving eptifibatide (n = 294) or abciximab (n = 158). No significant differences in hospital clinical outcomes were observed for reinfarction (2 vs. 3% for eptifibatide and abciximab, respectively), repeat revascularization (3 vs. 4%), bleeding complications (8 vs. 12%), congestive heart failure (5 vs. 3%), cerebrovascular accidents (0 vs. 2%), renal failure (2 vs. 3%), and all-cause mortality at discharge (5 vs. 4%). No significant difference was seen between groups in all-cause mortality at 6 months (6.5 vs. 6.4%; hazard ratio 0.976; 95% confidence interval 0.43-2.23; log-rank, p = 0.95).

CONCLUSIONS

No significant differences were observed in clinical outcomes between STEMI patients receiving eptifibatide or abciximab in the setting of PCI. Considering the substantially lower cost of eptifibatide, these data suggest that eptifibatide can be substituted for abciximab to lower overall medication costs while maintaining beneficial safety and efficacy effects.

Platelet inhibition with prasugrel (CS-747) compared with clopidogrel in patients undergoing coronary stenting: the subset from the JUMBO study

BACKGROUND

Based on the preclinical and phase 1 studies, prasugrel, a novel platelet ADP P2Y12 receptor blocker, may be a more potent platelet inhibitor than clopidogrel. This study compared the antiplatelet properties of prasugrel in a small subset of patients enrolled in the JUMBO trial, and compared with historic clopidogrel treated controls.

METHODS AND RESULTS

Nine patients undergoing coronary stenting were randomised to one of three arms of prasugrel (40 mg loading, and 7.5 mg maintenance, n = 1; 60/10 mg, n = 4; or 60/15 mg, n = 2), or clopidogrel (300/75 mg, n = 2). Aspirin and GP IIb/IIIa inhibitors were permitted. Platelet activity was assessed at baseline, at 4, and 24 hours, and at 30 days after stent implantation in substudy participants, and compared with 124 historic controls who received clopidogrel. Independent of the loading, or maintenance dose, patients treated with prasugrel exhibited significantly more potent platelet inhibition as determined by ADP, and collagen induced aggregation, Ultegra Analyser, and surface expression of PECAM-1, GPIIb/IIIa antigen, and activity with PAC-1 antibody, GPIb, P-selectin, CD40-ligand, GP37, and thrombospondin receptor expression when compared with those treated with clopidogrel. There were no differences between antiplatelet agents with regard to vitronectin, LAMP-1, PAR-1 (intact and cleaved epitopes) thrombin receptor expression, or formation of platelet-monocyte microparticles. Expression of GPIIb antigen, vitronectin, and LAMP-3 receptor were not affected by both agents. Two patients treated with prasugrel 10 mg/daily exhibited complete inhibition of collagen induced aggregation at 30 days.

CONCLUSION

At the dosing regimens chosen in the JUMBO trial, it seems that prasugrel is a more potent antiplatelet agent than clopidogrel. Two episodes of profound platelet inhibition, which are not seen with clopidogrel, raise the possibility of higher bleeding risks especially during long term prasugrel use. Whether stronger platelet inhibition will yield better clinical outcomes and/or increased bleeding remains to be determined in an ongoing comparative phase 3 superiority trial (TRITON).

Rebound platelet activation after termination of prasugrel and aspirin therapy due to confirmed non-compliance in patient enrolled in the JUMBO Trial

Therapy with aspirin and/or adenosine diphosphate (ADP) receptor blockers is associated with better outcomes via inhibition of platelet activity, and subsequent reduction of ischemic vascular events. Non-compliance (NC) is a well-recognised hazard limiting the clinical utility of antiplatelet agents, and, probably worsening outcomes. However, comprehensive platelet characteristics of a confirmed NC patient after acute vascular event have never been reported within a major randomised trial with ADP-receptor antagonists. A 48-year-old male patient, well-educated, was among patients enrolled in the platelet sub-study for the JUMBO trial. He received 325 mg of aspirin daily for 9 months, presented with unstable angina for urgent coronary intervention, and was successfully reperfused with two intracoronary stents. The patient was randomised to a 60 mg prasugrel loading dose, and 10 mg of prasugrel daily for 30 days. Platelets were assessed at baseline, 4 and 24 h, and at 30 days after acute coronary event utilising ADP-, and collagen-induced conventional aggregometry, rapid cartridge-based analyser and flow cytometry. Loading with prasugrel resulted in significant inhibition of platelet activity during and after stenting. However, after assessing platelet biomarkers at 30 days, voluntary withdrawal from the antiplatelet agents was suspected. Based on the platelet activity characteristics, NC was later confirmed, and the patient admitted that he stopped taking both prasugrel and aspirin shortly after discharge due to minor bleeding episodes after shaving. Major platelet activity biomarkers of the index NC patient were compared with those from compliant prasugrel-, clopidogrel-treated patients, and healthy controls. The platelet tests uniformly revealed rebound activation by all platelet measures (at least twofold increase) while being especially high for ADP-, and collagen-induced aggregation, platelet/endothelial cell adhesion molecule-1 (PECAM-1), glycoprotein (GP)Ib, GPIIb/IIIa activity, P-selectin, protease activated receptor (PAR)-1 thrombin receptor (activated and intact epitopes), and thrombospondin expression. The clinical benefits of antiplatelet agents are not only denied in NC outpatients, but may put them at additional risk for worsened vascular outcomes due to the rebound platelet activation. Proclaimed 'resistance' to antiplatelet agents may at least in part be a result of NC, especially in the chronic uncontrolled setting. Enforcing compliance will improve outcomes in the clinical trials, and save lives of patients really receiving antiplatelet therapy.

Effect of statins on platelet PAR-1 thrombin receptor in patients with the metabolic syndrome (from the PAR-1 inhibition by statins [PARIS] study)

We investigated whether, in primary prevention patients with metabolic syndrome, statins affect the platelet protease-activated receptor-1 (PAR-1) thrombin receptor by performing serial measurements of its activity and the antigen expression level by flow cytometry before and during treatment. Recent data from randomized trials of statins are compatible with the possibility of clinically relevant pleiotropic effects. The use of statins is associated with a reduced thrombosis burden and diminished platelet activity, as shown in animal models and in vitro studies. Seventy patients with the metabolic syndrome who were not taking antiplatelet agents were assigned consecutively at starting doses at the discretion of the responsible clinician to 1 of 6 statins (atorvastatin, fluvastatin, lovastatin, pravastatin, rosuvastatin, or simvastatin) or to a no-statin group for 6 weeks. Platelet expression of intact (SPAN12 antibody) and cleaved (WEDE15) PAR-1 thrombin receptors were assessed by flow cytometry at baseline and at weeks 4 and 6 of treatment. At baseline, no difference was found in receptor expression. However, after 4 weeks of treatment, all statins had significantly inhibited (46% to 55%) the activated epitope of PAR-1 expression. After 6 weeks, inhibition remained, despite a slight rebound (22% to 37%). Also, a delayed pattern of inhibition of the intact PAR-1 receptor epitope was found. In conclusion, all statins inhibited the activity and antigen level of the platelet PAR-1 thrombin receptor, which has a major role in regulating platelet activity and thrombin formation. These observational data offer a plausible mechanism for the recently demonstrated pleiotropic effects of statins that may contribute to early clinical benefit.

Absence of Interaction Between Atorvastatin or Other Statins and Clopidogrel

BACKGROUND

Some, but not all, post hoc analyses have suggested that the antiplatelet effects of clopidogrel are inhibited by atorvastatin. We sought to address this issue prospectively by performing serial measurements of 19 platelet characteristics using conventional aggregometry, rapid analyzers, and flow cytometry.

METHODS

The Interaction of Atorvastatin and Clopidogrel Study (Interaction Study) was designed for patients undergoing coronary stenting. All patients (n = 75) received 325 mg of aspirin daily for at least 1 week and 300 mg of clopidogrel immediately prior to stent implantation. They had been taking atorvastatin (n = 25), any other statin (n = 25), or no statin (n = 25) for at least 30 days prior to stenting. The main outcome measure was comparison of platelet biomarkers 4 and 24 hours after clopidogrel administration between study groups.

RESULTS

At baseline, patients from both statin groups exhibited diminished platelet aggregation and reduced platelet expression of G-protein-coupled protease-activated thrombin receptor (PAR)-1. There were no significant differences in measured platelet characteristics among the study groups 4 and 24 hours after clopidogrel intake, with the exception of a lower collagen-induced aggregation at 24 hours and a constantly diminished expression of PAR-1 in patients treated with any statin.

CONCLUSIONS

Statins in general, and atorvastatin in particular, do not affect the ability of clopidogrel to inhibit platelet function in patients undergoing coronary stenting. These prospective data also suggest that statins may inhibit platelets directly via yet unknown mechanism(s) possibly related to the regulation of the PAR-1 thrombin receptors.

Effects of Valsartan and Valeryl 4-Hydroxy Valsartan on Human Platelets: A Possible Additional Mechanism for Clinical Benefits

Valsartan selectively blocks angiotensin II binding to the AT1 receptor. ince platelet activation plays a key role in the pathogenesis of vascular disease, and because AT1 receptors are present on the platelet surface, we assessed the in vitro effects of valsartan and its metabolite, valeryl 4-hydroxy valsartan (V4HV), on platelets in 30 subjects with multiple risk factors for cardiovascular disease. Platelet characteristics in blood samples pretreated and incubated with 10 nmol to 100 micromol concentrations of valsartan and V4HV were assessed by aggregometry, rapid platelet analyzers, and by flow cytometry. Pretreatment of blood with valsartan and V4HV resulted in inhibition of conventional plasma (ADP, P = 0.0001, valsartan; epinephrine, P = 0.0001, V4HV) and whole blood collagen-induced (P = 0.01, valsartan; P =.0001, V4HV) platelet aggregation. Closure time was delayed (P = 0.02, valsartan; P = 0.03, 4VHV), indicating platelet inhibition in whole blood under high shear conditions. Expression of many surface platelet receptors, namely GP IIb/IIIa antigen, and activity, vitronectin, p-selectin, and LAMP-1 was significantly reduced compared with autologous baseline activity. Intensity of platelet-leukocyte formation and other platelet activation markers remained unchanged. Platelet inhibition was not dose dependent and was more potent for 4VHV than valsartan in the therapeutic range.Valsartan and 4VHV exhibited significant in vitro inhibition of human platelets. Their antiplatelet properties, especially more potent activity of the metabolite appear to be independent of those of other antiplatelet agents. Whether valsartan reduces vascular ischemic events via additional pathways of platelet inhibition in patients with myocardial infarction and ischemic stroke requires further clinical research.

Effects of clopidogrel and aspirin combination versus aspirin alone on platelet aggregation and major receptor expression in patients with heart failure: the Plavix Use for Treatment Of Congestive Heart Failure (PLUTO-CHF) trial

BACKGROUND

Persistent platelet activation may contribute to thrombotic events in patients with congestive heart failure (CHF). Chronic use of mild platelet inhibitors could therefore represent an independent avenue to improve morbidity, mortality, and quality of life in this expanding population. Although clopidogrel is widely used in patients with acute coronary syndromes and ischemic stroke, the ability of this novel ADP-receptor antagonist to inhibit platelet function in patients with CHF is unknown. We assessed antiplatelet properties of clopidogrel with aspirin (C+A) versus aspirin alone (A) in patients with CHF with heightened platelet activity.

METHODS

Patients with left ventricular ejection fraction <40%, or CHF symptoms in the setting of preserved systolic function and New York Heart Association class II-IV were screened. Patients were considered to have platelet activation when 4 of the following 5 parameters were met: ADP-induced platelet aggregation >60%; collagen-induced aggregation >70%; whole blood aggregation >18 ohms; expression of GP IIb/IIIa >220 log MFI; and P-selectin cell positivity >8%. All patients were treated with 325 mg of acetylsalycilic acid (ASA) for at least 1 month. Patients receiving an antithrombotic agent other than ASA were excluded. Patients meeting clinical and laboratory criteria were randomly assigned to C+A (n=25), A (n=25) groups, or represent screen failures (n=38). Platelet studies (conventional and whole blood aggregometry, shear-induced activation, expression of 10 major receptors and formation of platelet-leukocyte microparticles) were performed at baseline and after 30 days of therapy.

RESULTS

There were no deaths, hospitalizations, or serious adverse events. There were no changes in platelet parameters in the A group. In contrast, therapy with C+A resulted in a significant inhibition of platelet activity assessed by ADP-induced (P =.00001), and epinephrine-induced (P =.0016) aggregation, closure time (P =.04), expression of PECAM-1 (P =.009), GP Ib (P =.006), GP IIb/IIIa antigen (P =.0001), GP IIb/IIIa activity with PAC-1 (P =.0021), and CD151 (P =.0026) when compared with the A group. Therapy with C+A also resulted in the reduced formation of platelet-leukocyte microparticles (P =.021). Collagen-induced aggregation in plasma and in whole blood, expression of vitronectin receptor, P-selectin, CD63, CD107a, and CD107b did not differ among groups.

CONCLUSIONS

Treatment with C+A for 1 month provides significantly greater inhibition of platelet activity than ASA alone in patients with CHF. Patients with CHF with heightened platelet activity represent a potential target population in which addition of clopidogrel may decrease mortality rates by reducing the incidence of thrombotic vascular events.

Moderate alcohol consumption is associated with decreased platelet activity in patients presenting with acute myocardial infarction

Moderate alcohol consumption (MAC) and platelet inhibition have been independently associated with a reduced risk for the development of acute myocardial infarction (AMI). The effects of MAC on the initial platelet status in patients presenting with AMI are not elucidated. Here we sought to define the effects of MAC on platelet characteristics in AMI patients before applying any reperfusion strategies. The study was designed as an analysis within the cohort study in 23 patients with AMI enrolled in the GUSTO-III. Platelets were investigated by different techniques, including aggregometry, flow cytometry, and ELISA. MAC patients exhibited mild, but consistent, inhibition of platelet aggregability, surface receptor expression, and released substances as compared to non-alcohol consuming patients. These differences were significant for 5 microM ADP (p = 0.04), 10 microM ADP-induced aggregation (p = 0.02); P-selectin (p = 0.01), and PECAM-1 (p = 0.02) platelet-bound expression. Our study confirms that moderate alcohol consumption is associated with diminished platelet activation in patients presenting with AMI. The ability of MAC to favorably modulate the pre-reperfusion platelet status in such patients is of clinical importance, and further investigation in large-scale clinical trials seem warranted.

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.

Intravenous amiodarone for the prevention of atrial fibrillation after open heart surgery: the Amiodarone Reduction in Coronary Heart (ARCH) trial

OBJECTIVES

This study was designed to test whether intravenous (i.v.) amiodarone would prevent atrial fibrillation and decrease hospital stay after open heart surgery.

BACKGROUND

Atrial fibrillation commonly occurs after open heart procedures and is thought to be a significant determinant for prolongation of hospitalization. Oral amiodarone given preoperatively appears to reduce the incidence of atrial fibrillation. This study was designed to test whether the more rapid-acting i.v. formulation of amiodarone given postoperatively would reduce the incidence of atrial fibrillation.

METHODS

Three hundred patients undergoing standard open heart surgery were randomized in a double-blind fashion to i.v. amiodarone (1 g/day for 2 days) versus placebo immediately after open heart surgery. The primary end points of the trial were incidence of atrial fibrillation and length of hospital stay. Baseline clinical variables and mortality and morbidity data were collected.

RESULTS

Atrial fibrillation occurred in 67/142 (47%) patients on placebo versus 56/158 (35%) on amiodarone (p = 0.01). Length of hospital stay for the placebo group was 8.2 +/- 6.2 days, and 7.6 +/- 5.9 days for the amiodarone group (p = 0.34). No differences were noted in baseline variables, morbidity or mortality.

CONCLUSIONS

Low-dose i.v. amiodarone was safe and effective in reducing the incidence of atrial fibrillation after heart surgery, but did not significantly alter length of hospital stay.

Plasma thromboxane and prostacyclin are linear related and increased in patients presenting with acute myocardial infarction

The role of prostanoids in patients with ischemic heart disease including acute myocardial infarction (AMI) has been recognized. However, there is very limited knowledge of the baseline TXB2 and 6-keto-PGF1a plasma levels in patients with AMI before therapy has been administered. We compared plasma levels of TXB2 and 6-keto-PGF1a by enzyme immunoassay in 18 AMI patients before thrombolysis, with those of 13 healthy controls. Plasma levels of TXB2 (319.78+/-16.50 pg/ml) and 6-keto-PGF1a (536.72+/-56.71 pg/ml) were heterogeneous, but significantly higher in the AMI patients than in controls (175.92+/-17.29 pg/ml and 192.08+/-26.11 pg/ml, respectively). In some patients, long-term aspirin therapy mildly inhibits baseline prostanoid levels, however, limited data prevents us from further speculations on this issue. Although, the contributions by prostanoids to the pathogenesis of AMI have been well proposed, their plasma concentrations are not uniformly elevated, and it is still unclear whether the resultant changes are indicative of clinically meaningful effects.

Depressed plasma platelet-activating factor acetylhydrolase in patients presenting with acute myocardial infarction

Cell membrane phospholipids, including platelet-activating factor (PAF), participate in the pathogenesis of acute myocardial infarction (AMI). The plasma level of PAF acetylhydrolase (AH) was determined in 18 patients at presentation with AMI before thrombolysis, and the administration of adjunctive therapy, and compared with 13 healthy controls. Plasma levels of PAF-AH were significantly lower in the AMI patients (23.15 +/- 1.75 nmol/min/ml) than in the controls (30.43 +/- 2.13 nmol/min/ml; p = 0.027). Considering normal plasma levels of PAF and lyso-PAF, and lack of evidence that anti-PAF antibodies are really beneficial in myocardial ischemia-reperfusion, it is reasonable to speculate that an inability of systemic PAF to 'turn on' PAF-AH enzymatic activity could contribute substantially to the observed events. Decreased PAF-AH activity in AMI patients may represent not a consequence, but rather, a risk factor for the development of acute coronary syndromes.

Antecedent aspirin therapy inhibits baseline platelet activity in patients presenting with acute myocardial infarction. The GUSTO-III Platelet Substudy

Aspirin therapy and platelet inhibition reduce the risk for the development of acute myocardial infarction (AMI). However, the effects of aspirin on baseline platelet activity in patients presenting with AMI are not known. We determined the effect of long-term aspirin use on baseline platelet activity in patients presenting with AMI, enrolled in the GUSTO-III Platelet Study. Platelet characteristics were investigated by aggregometry, flow cytometry and enzyme-linked immunosorbent assay in 23 patients before thrombolysis. Sixteen AMI patients were aspirin free, and 7 patients were using aspirin (81-500 mg/daily). The aspirin-treated patients exhibited a mild but consistent reduction of platelet activity which reached significance for 5 microM (p = 0.02), and 10 microM (p = 0.01) adenosine diphosphate induced aggregation. The surface expression of P-selectin (p = 0.02) and PECAM-1 (p = 0.03) and the plasma level of soluble P-selectin (p = 0.02) were also reduced. As previously observed in normal humans and patients with stable coronary artery disease, long-term aspirin therapy is also associated with diminished platelet activation in patients presenting with AMI. Long-term aspirin therapy mildly reduces baseline platelet activity; however, this degree of relative platelet inhibition does not appear to be cardioprotective.

Lipoprotein-cholesterol analysis during screening: accuracy and reliability

OBJECTIVE

To evaluate the accuracy and reliability of lipoprotein-cholesterol measurements obtained during screening.

DESIGN

Cross-sectional study.

PARTICIPANTS

From November 1989 to January 1990, 154 adults were screened.

MEASUREMENTS

Split venous samples from fasting participants were analyzed for total cholesterol, triglyceride, and high-density-lipoprotein (HDL) cholesterol with screening and standardized laboratory methods. Low-density-lipoprotein (LDL)-cholesterol levels were calculated using the Friedewald equation. Split venous samples from nonfasting participants were analyzed for total cholesterol. Capillary blood samples were analyzed for total cholesterol with the screening method.

MAIN RESULTS

Total cholesterol measurements in screening venous blood samples were 5.4% and 3.8% lower than the laboratory values in samples from fasting and nonfasting participants, respectively. Triglyceride and HDL-cholesterol values in venous samples obtained from fasting participants were, on average, 9.8% and 11.2% lower than the respective laboratory measurements. Screening HDL-cholesterol values varied, differing from the laboratory values by as much as 40% in 95% of participants. In fasting participants, total cholesterol in capillary samples averaged 5.5% higher than in venous samples; in nonfasting participants the capillary samples were 3.1% higher. Screening for either total cholesterol or LDL cholesterol identified 93% of the persons with LDL-cholesterol values of 3.36 mmol/L (130 mg/dL) or higher.

CONCLUSIONS

Total cholesterol can be reliably measured in samples from fasting or nonfasting persons. The values in capillary blood samples were slightly higher than those in venous samples. Screening HDL-cholesterol values were too variable to establish the HDL-cholesterol level reliably. Participants with high LDL-cholesterol levels were identified as accurately by measuring total cholesterol only when compared with calculating the LDL-cholesterol level from total cholesterol, triglyceride, and HDL-cholesterol concentrations.