Immature platelet fraction (IPF) determined with an automated method predicts clopidogrel hyporesponsiveness

The mechanisms for the variability in antiplatelet effects of clopidogrel are not elucidated entirely. Immature (reticulated) platelets may modulate the antiplatelet effects of clopidogrel but must be measured using flow cytometry. Whether new automated detection techniques yield similar results is not known. The objectives of the study to evaluate the role of immature platelets assessed by an automated method in response to the antiplatelet effects of clopidogrel. Twenty-nine healthy volunteers had platelet studies performed before and 1 week after 75 mg daily dosing of clopidogrel. Immature platelet fraction (IPF) was determined using an automated particle counter. Subjects were stratified into tertiles based on the IPF. Platelet studies included light transmission aggregometry (LTA), and vasodilator stimulated phosphoprotein phosphorylation (VASP-P) determined by platelet reactivity index (PRI). Baseline platelet aggregation responses to 2, 5 and 20 μM ADP, were similar in all three tertiles, however they were greater in the upper than in the lower tertile of immature platelets after clopidogrel in response to 5 μM ADP (54% vs. 23%, P = 0.02), with concordant trends for the other two concentrations. PRI was also greater in the upper tertile after clopidogrel (71.2% vs. 57.8%, P = 0.04). The frequency of clopidogrel hyporesponsiveness (aggregation >50% in response to 5 μM of ADP) was also higher in the upper tertile when compared to lower tertile, (60%) versus (10%) respectively (P = 0.0001). Immature platelets measured using an automated method, are associated with impaired response to antiplatelet effects of clopidogrel.     

Effect of 450-mg loading dose of clopidogrel on platelet function in Japanese patients undergoing coronary stent placement

Usefulness of higher (>300 mg) loading doses of clopidogrel has been demonstrated in studies from the United States and Europe. The present study evaluated platelet aggregation after the administration of a 450-mg loading dose of clopidogrel in Japanese patients undergoing coronary stenting. Platelet aggregation was serially measured at baseline, and 2, 4, 6, and 8 h after 450-mg clopidogrel loading in 25 patients undergoing coronary stenting. Platelets were stimulated with 5 and 20 μmol/l adenosine diphosphate (ADP) and aggregation was assessed by optical aggregometry. Platelet aggregation (5 μmol/l ADP 42.8% ± 13.5% and 20 μmol/l ADP 51.2% ± 11.6%) was significantly suppressed ≤4 h after 450-mg clopidogrel loading. There were no adverse events except one minor nasal bleed. The present study shows that platelet inhibition is achieved ≤4 h after the administration of a 450-mg clopidogrel loading dose in Japanese patients.     

Inverse relationships between coronary blood flow obstruction and platelet reactivity in stable angina pectoris

This study investigates relationships between platelet reactivity and coronary blood flow obstruction in stable angina pectoris. Consented were 36 patients with single-vessel disease. The subjects were divided into two groups. One group (n?=?14) had less severe (<?=?80%) and the second group (n?=?22) had severe coronary flow impairment (90%). Before elective coronary angiography platelet in vitro reactivity in venous whole blood was determined using a flow cytometry technique. A thrombin-receptor activating peptide (TRAP-6) (0.77 and 0.06?g/l) and ADP (8.5 and 1.7?µmol/l) were used to activate platelets. The number of fibrinogen positive cells (%) i.e., activated platelets after stimulation was employed as experimental parameter. Less severe flow obstruction was associated with more reactive platelets. When stimulating with 0.77?g/l TRAP-6 the number of activated platelets was 64?±?15 (SD)%. The corresponding value for the group with severe flow obstruction was 40?±?17(SD)%. The difference is significant (P?<?0.001). 0.06?g/l TRAP-6 yielded similar results (P?<?0.01). Also when using 8.5?µmol/l ADP to challenge platelets less severe flow obstruction was associated with enhanced reactivity (P?<?0.01). 1.7?µmol/l ADP generated comparable results (P?<?0.05). Thus, in stable angina pectoris coronary flow obstruction is inversely related to platelet reactivity.     

Comparison of the effects of pretreatment with tirofiban, clopidogrel or both on the inhibition of platelet aggregation and activation in patients with acute coronary syndromes

Objective We sought to compare platelet inhibition produced by three antiplatelet regimens. Methods and results Sixty NSTE-ACS patients undergoing coronary angiography treated with aspirin and enoxaparin were randomised to receive tirofiban 0.4 μg/kg/min over 30 min plus 0.15 μg/kg/min over 24 h (A), clopidogrel 600 mg (B), clopidogrel 300 mg plus tirofiban (C); blood samples were taken at baseline and 2, 6 and 24 h after the drug administration, and were analyzed by light transmission aggregometry and flow cytometry. Treatment with clopidogrel 600 mg significantly reduced P-selectin expression in comparison with tirofiban alone at all time points (group B vs. A: P < 0.0001). However tirofiban inhibited platelet aggregation significantly more than clopidogrel 600 mg during the first 6 h (group A vs. B: P < 0.0001), and the addition of clopidogrel 300 mg did not inhibit platelet aggregation any more than tirofiban alone throughout the 24 h (group C vs. A: P = NS). All of the changes over time within each group were highly significant (P < 0.0001). Conclusions Tirofiban leads to greater early inhibition of platelet aggregation but less suppression of P-selectin expression than clopidogrel 600 mg. The addition of clopidogrel to tirofiban does not add any anti-aggregatory effect, but reduces P-selectin expression, thus likely adding a significant biological and clinical protective effect and providing a rationale for the combined use of the two drugs. Condensed abstract We sought to compare platelet inhibition produced by three antiplatelet regimens using light transmission aggregometry and flow cytometry. Tirofiban leads to greater early inhibition of platelet aggregation but less suppression of P-selectin expression than clopidogrel 600 mg, thus providing the rationale for the combined use of the two drugs. Emilia Solinas and Giuliana Gobbi contributed equally to the study.     

Evaluation of platelet response to different clopidogrel dosing regimens in patients with acute coronary syndrome in clinical practice

High-post clopidogrel platelet reactivity in acute coronary syndrome (ACS) patients is associated with adverse outcomes and may be related to clopidogrel dosing. Clinical studies evaluating different clopidogrel doses have resulted in conflicting conclusions. Clopidogrel dosing regimens have evolved over time, enabling us to evaluate platelet reactivity in real-life ACS patients undergoing percutaneous coronary intervention and treated with three different clopidogrel doses. Platelet reactivity was assessed with light transmitted aggregometry on the third day post clopidogrel loading in 404 consecutive ACS patients. Of them, 198 were treated with a standard regimen (300?mg loading, 75?mg/day maintenance dose), 95 with a high loading regimen (600?mg loading, 75?mg/day maintenance dose) and 111 with a high loading/high maintenance regimen (600?mg loading, 150?mg/day maintenance). Compared with the standard regimen, the high loading regimen resulted in significantly lower mean platelet reactivity to adenosine diphosphate (ADP) with a lower proportion of patients exhibiting clopidogrel non-responsiveness (11% vs. 28%, p?=?0.004). Compared with the high loading regimen, the high loading/high maintenance regimen resulted in significantly lower mean platelet reactivity to ADP, but without a further drop in the number of non-responders (8.1% vs. 11%, p?=?0.16). In conclusion, greater overall inhibition can be achieved with higher loading and maintenance doses in ACS patients. However, despite high clopidogrel doses, a sizable proportion of patients remained “resistant” to the effects of clopidogrel.     

Sulfonylureas and on-clopidogrel platelet reactivity in type 2 diabetes mellitus patients

Clopidogrel is a prodrug that needs to be converted in vivo by several cytochrome (CYP) P450 iso-enzymes to become active. Both clopidogrel and the oral hypoglycemic drug class sulfonylureas are metabolized by the iso-enzyme CYP2C9. The objective of the study was to evaluate the relationship of sulfonylureas and on-clopidogrel platelet reactivity in type 2 diabetes mellitus patients undergoing elective coronary stent implantation. In this prospective, observational study, on-clopidogrel platelet reactivity was quantified using adenosine diphosphate (ADP)-induced light transmittance aggregometry in 139 type 2 diabetes mellitus patients undergoing elective coronary stent implantation treated with clopidogrel and aspirin. High on-clopidogrel platelet reactivity was defined as >70.7% platelet reactivity to 20?µmol/L ADP. A total of 53 patients (38.1%) were on concomitant treatment with sulfonylureas. The remaining 86 patients were on other hypoglycemic drugs. On-clopidogrel platelet reactivity was significantly higher in patients with concomitant sulfonylurea treatment as compared to patients without concomitant sulfonylurea treatment (for 5?µmol/L ADP: 46.0%?±?11.8 vs. 40.6%?±?16.0; p?=?0.035, adjusted p?=?0.032 and for 20?µmol/L ADP: 64.6%?±?10.8 vs. 58.7%?±?15.5; p?=?0.019, adjusted p?=?0.017). The concomitant use of sulfonylureas was associated with a 2.2-fold increased risk of high on-clopidogrel platelet reactivity (OR 2.2, 95% CI 1.1–4.7, p?=?0.039 and after adjustment for confounders: OR_adj 2.0, 95% CI 1.0–5.7, p?=?0.048). Concomitant treatment with sulfonylureas might be associated with decreased platelet inhibition by clopidogrel in type 2 diabetes mellitus patients on dual antiplatelet therapy undergoing elective coronary stent implantation.     

Effect of colchicine compared with placebo on high sensitivity C-reactive protein in patients with acute coronary syndrome or acute stroke: a pilot randomized controlled trial

There is a need for more effective therapies to reduce morbidity and mortality from cardiovascular disease. Inflammation plays a central role in the pathogenesis of atherosclerosis but no randomized studies have evaluated anti-inflammatory therapy in patients with acute coronary or cerebrovascular disease. We performed a pilot randomized controlled trial comparing the effect of colchicine 1 mg per day with placebo on high sensitivity C-reactive protein (CRP) levels and platelet function in 80 patients with acute coronary syndrome or acute ischemic stroke who were followed for 30 days. Clinical status was ascertained for 74 (92.5%) patients and CRP levels were obtained in 68 (85%) of patients at follow up. Colchicine did not significantly reduce absolute hs-CRP at 30 days [median 1.0 mg/l (range 0.2, 162.0) versus 1.5 mg/l (0.2, 19.8), P = 0.22] or difference in CRP from baseline to 30 days [absolute difference 7.0 mg/l (−61.0, 87.8) vs. 7.1 mg/l (−1.0, 144), P = 0.64]. The proportion of patients with CRP <2 mg/l at follow up did not differ according to treatment allocation (77% vs. 62%, X ² 1.84, P = 0.18). There was also no difference in platelet function assessed using platelet aggregation with ADP (5 μmol), arachidonic acid (0.5 mmol), collagen (1 μg/ml) and collagen (5 μg/ml) (P = 0.86, P = 0.64, P = 0.76, P = 0.20, respectively), and urine dehydrothromboxane B2 (P = 0.54). Colchicine was associated with an excess of diarrhoea (X ² 4.14, P = 0.04). In conclusion, our pilot study provided no evidence that colchicine 1 mg daily for 30 days compared with placebo suppresses inflammation in patients with acute coronary syndrome or acute ischemic stroke.     

Lack of early augmentation of platelet reactivity after coronary intervention in patients treated with bivalirudin

To determine whether a regimen of aspirin pretreatment, bivalirudin during the procedure and clopidogrel (600 mg) immediately after percutaneous coronary intervention (PCI) was associated with platelet activation during and shortly after (1 and 2 h) PCI, we characterized platelet function in 10 patients with the use of flow cytometry in the absence of agonist and in response to thrombin (10 nM), ADP (1 μM), the collagen-mimetic convulxin (5 ng/ml), and platelet activating factor (10 nM). Activation of platelets in peripheral blood was rare (<0.5% of platelets) before, during and after PCI. Platelet reactivity in response to each of the agonists was lower after the PCI compared with that in blood taken before the PCI. Accordingly, platelet activation and platelet reactivity were not increased after elective PCI when patients were treated during the procedure with aspirin and bivalirudin and immediately after the procedure with a 600 mg loading dose of clopidogrel.     

Evidence of platelet sensitization to ADP following discontinuation of clopidogrel therapy in patients with stable coronary artery disease

Epidemiological studies have linked clopidogrel discontinuation with an increased incidence of ischemic events. This has led to the hypothesis that clopidogrel discontinuation may result in a pharmacological rebound. We evaluated the impact of clopidogrel discontinuation on platelet function. Platelet aggregation was measured by light transmission aggregometry (LTA) in response to adenosine diphosphate (ADP) 0.5, 1, 1.5, 2.5, 5 and 10?µM and by VerifyNow® P2Y₁₂, in 37 clinically stable coronary artery disease (CAD) patients scheduled to discontinue clopidogrel treatment, and 37 clinically stable CAD patients not taking clopidogrel. Platelet function was assessed the day before clopidogrel cessation and 1, 3, 7, 14, 21 and 28 days after. Clopidogrel had been initiated a median of 555 days (ranging from 200 to 2280 days) before the treating cardiologist recommended its discontinuation. All participants were taking aspirin, most commonly 80?mg daily although a minority was prescribed 325?mg daily. Following clopidogrel discontinuation, VerifyNow® P2Y₁₂ did not detect any rebound platelet activity, but ADP-induced LTA showed platelet sensitization to ADP, particularly at low ADP levels. Increased platelet activity was detectable seven days after clopidogrel cessation and remained higher than in controls 28 days after discontinuation. No clinical event occurred in any of the participants during the 28 days following clopidogrel cessation. In conclusion, platelet sensitization to ADP as a consequence of chronic clopidogrel administration may partially explain the recrudescence of ischemic events following clopidogrel discontinuation in otherwise stable coronary artery patients.     

Antiplatelet effect of 50-mg maintenance dose of clopidogrel compared to 200 mg ticlopidine: a preliminary study

In the United States and Europe, patients with coronary stents are maintained on 75 mg clopidogrel. Because the maintenance dose of ticlopidine in patients with coronary stents is 100 mg twice daily in Japan and 250 mg twice daily in the United States and Europe, in Japanese patients a lower dose of clopidogrel may achieve an antiplatelet effect comparable to 200 mg ticlopidine. Platelet aggregation was evaluated in 104 consecutive patients on 50 mg clopidogrel plus aspirin (n = 54) and 200 mg ticlopidine plus aspirin (n = 50). Platelets were stimulated with adenosine diphosphate (5 and 20 μmol/l) and aggregation was assessed by optical aggregometry. There was no significant difference in platelet aggregation induced with 5 (37% ± 11% vs 38% ± 15%, not significant) and 20 μmol/l adenosine diphosphate (48% ± 13% vs 51% ± 12%, not significant) between 50 mg clopidogrel and 200 mg ticlopidine. In Japanese patients, there is the possibility that a maintenance dose of 50 mg clopidogrel on platelet inhibition is comparable to 200 mg ticlopidine.     

The effect of cessation of 2nd generation P<Subscript>2</Subscript>Y<Subscript>12</Subscript> inhibitor therapy on platelet reactivity in patients 1 year after acute myocardial infarction

To assess the effect of cessation of dual antiplatelet therapy (DAPT) regimens containing 2nd generation P₂Y₁₂ inhibitors on platelet reactivity, in patients who completed 12 months of DAPT following an acute myocardial infarction. Clinical data has shown an increased cardiovascular risk in the 90 days following cessation of DAPT. One possible explanation is a transient platelet hyper-reactivity after cessation of treatment. Data from patients treated with 2nd generation P₂Y₁₂ inhibitors is scarce. Patients who completed 12 month DAPT with prasugrel/ticagrelor underwent serial assessment of platelet reactivity (on DAPT and 1, 4 and 12 weeks post cessation). The primary outcome was platelet reactivity, expressed as platelet reactivity units (PRU) at each time point. 41 participants were included in this study, (23 ticagrelor, 18 prasugrel). There was no statistically significant differences in baseline characteristics between prasugrel/ticagrelor treated patients . The pattern of platelet reactivity recovery after DAPT cessation differed between the ticagrelor and prasugrel: with ticagrelor, after the initial PRU increase from baseline, the PRU remained stable, while with prasugrel, there was a further increase in PRU between 1 and 4 weeks, with a return to the 1 week level by 12 weeks (p?=?0.034 for the time?×?treatment interaction between ticagrelor and prasugrel). Our results suggest there is a transient platelet hyper-reactivity after cessation of ADP receptor blockers therapy with prasugrel, but not ticagrelor. Further research is required to elucidate the pathophysiologic mechanisms behind these findings and to evaluate potential strategies to prevent or overcome this “rebound” effect.     

Impaired responsiveness to clopidogrel and aspirin in patients with recurrent stent thrombosis following percutaneous intervention for peripheral artery disease

Patients with peripheral artery disease (PAD) following peripheral percutaneous transluminal angioplasty (PTA) with stent implantation are prone to stent thrombosis despite treatment with aspirin and clopidogrel. Impaired clopidogrel responsiveness is associated with increased risk of ischemic events in patients following coronary stent implantation. We sought to assess platelet responsiveness to clopidogrel and aspirin in patients with PAD and recurrent stent thrombosis. Platelet aggregation induced by 5 and 20?µmol/l adenosine diphosphate (ADP) and 0.5?mmol/l arachidonic acid (AA), together with platelet reactivity index (PRI) and serum thromboxane B₂ (TXB₂), were determined in 11 patients with PAD and a history of stent thrombosis (mean, 3.1?±?1.14) after PTA and in 15 patients with PAD with no such history, also in 11 controls with coronary artery disease (CAD) and previous stent thrombosis. Platelet aggregation to 5?µmol/l ADP was higher in subjects with PAD and stent thrombosis than in those without stent thrombosis (p?=?0.0003) and CAD subjects (p?=?0.002). Aggregation induced by 20?µmol/l ADP was higher in PAD group with stent thrombosis than in PAD subjects without thrombosis (p?=?0.004). The PAD group with stent thrombosis had higher AA-induced platelet aggregation than CAD controls (p?=?0.007) and serum TXB₂ concentrations higher than PAD group without thrombosis (p?=?0.002) and CAD group (p?=?0.02). Concluding, platelet responsiveness to clopidogrel and aspirin is impaired in patients with PAD and recurrent stent thrombosis following PTA, as compared with similar individuals with CAD, and PAD with no history of stent thrombosis. This indicates that atherosclerosis burden affects platelet function and might contribute to stent thrombosis following percutaneous intervention in peripheral arteries.     

Hemostatic changes before and during electrophysiologic study and radiofrequency catheter ablation

We sought to investigate specific hemostasis activation markers during electrophysiologic study (EPS) with consequent radiofrequency catheter ablation (RFA). Sixty patients were studied prospectively during routine EPS with RFA for paroxysmal supraventricular tachycardia. Blood samples were drawn before the insertion of venous sheaths (T0), at the end of EPS (T1), and 30 min after completion of RFA (T2). To study coagulation and fibrinolytic and platelet activity, we measured concentrations of thrombin–antithrombin III (TAT), D-dimers (DD), plasminogen activator inhibitor type 1 (PAI-1), tissue-type plasminogen activator (t-PA), and circulating platelet aggregates. The results are expressed as median and show 95% confidence levels. Levels of DD increased from 0.24 mg/L at T0 to 0.37 mg/L at T1 (P < 0.001) and to 0.59 mg/L at T2 (P < 0.001). TAT levels increased from 5.29 μg/L at T0 to 35.80 μg/L at T1 (P < 0.001) and decreased to 26.30 μg/L at T2 (P < 0.001). PAI-1 concentration decreased from 30.10 μg/L at T0 to 26.4 μg/L at T1 (P < 0.001). t-PA at T2 increased to 5.10 μg/L from 4.75 μg/L at T1 (P = 0.001). No other differences between corresponding medians were statistically significant (P > 0.05). We found that concentrations of DD at T2 versus T1 depended on the number of radiofrequency energy applications (r _S = 0.387; P = 0.002). Marked platelet activation was observed from the start of the procedure, without changes during the procedure.     

Individual variations of platelet inhibition after loading doses of clopidogrel

Abstract . Järemo P, Lindahl TL, Fransson SG, Richter A (Linköping University Hospital, Linköping, Sweden). Individual variations of platelet inhibition after loading doses of clopidogrel. J Intern Med 2002; 252: 233–238. Objective. To investigate individual variations of platelet inhibition after clopidogrel‐loading doses. Setting. Department of Cardiology, Linköping University Hospital, Linköping, Sweden. Subjects. Individuals with stable angina pectoris (n = 18) subject to percutaneous coronary interventions (PCI) and subsequent stenting were investigated. Methods and experimental protocol. A 300‐mg clopidogrel loading dose was administrated immediately after stenting (day 1) followed by an additional 75 mg clopidogrel after 24 h (day 2). The ADP‐evoked platelet fibrinogen binding was analysed to estimate platelet reactivity immediately before angiography and on day 2. A flow cytometry technique was used with two ADP solutions (final concentrations 0.6 and 1.7 μmol L^?1) employed as platelet activating agents. Soluble P‐selectin was used as a marker of platelet activity. Results. When using 1.7 μmol L^?1 ADP to activate platelets four individuals had a strong inhibition (i.e. platelet reactivity <10% of the day 1‐value day 2). In contrast, five patients demonstrated a weak inhibition (i.e. platelet reactivity >60% of the day 1‐value day 2). Similar results were obtained when using 0.6 μmol L^?1 ADP as a platelet‐activating agent. Clopidogrel, however, fails to suppress platelet activity as estimated from soluble P‐selectin. Conclusions. Clopidogrel evoked platelet inhibition exhibits a considerable individual heterogeneity. Some individuals only had weak responses whereas others displayed strong platelet inhibition. The present flow cytometry technique appears suitable for identifying patients with abnormal reactions after clopidogrel exposure.     

Sulfonylureas and on-clopidogrel platelet reactivity in type 2 diabetes mellitus patients

Clopidogrel is a prodrug that needs to be converted in?vivo by several cytochrome (CYP) P450 iso-enzymes to become active. Both clopidogrel and the oral hypoglycemic drug class sulfonylureas are metabolized by the iso-enzyme CYP2C9. The objective of the study was to evaluate the relationship of sulfonylureas and on-clopidogrel platelet reactivity in type 2 diabetes mellitus patients undergoing elective coronary stent implantation. In this prospective, observational study, on-clopidogrel platelet reactivity was quantified using adenosine diphosphate (ADP)-induced light transmittance aggregometry in 139 type 2 diabetes mellitus patients undergoing elective coronary stent implantation treated with clopidogrel and aspirin. High on-clopidogrel platelet reactivity was defined as >70.7% platelet reactivity to 20 μmol/L ADP. A total of 53 patients (38.1%) were on concomitant treatment with sulfonylureas. The remaining 86 patients were on other hypoglycemic drugs. On-clopidogrel platelet reactivity was significantly higher in patients with concomitant sulfonylurea treatment as compared to patients without concomitant sulfonylurea treatment (for 5 μmol/L ADP: 46.0% ± 11.8 vs. 40.6% ± 16.0; p=0.035, adjusted p=0.032 and for 20 μmol/L ADP: 64.6% ± 10.8 vs. 58.7% ± 15.5; p=0.019, adjusted p=0.017). The concomitant use of sulfonylureas was associated with a 2.2-fold increased risk of high on-clopidogrel platelet reactivity (OR 2.2, 95% CI 1.1-4.7, p=0.039 and after adjustment for confounders: OR(adj) 2.0, 95% CI 1.0-5.7, p=0.048). Concomitant treatment with sulfonylureas might be associated with decreased platelet inhibition by clopidogrel in type 2 diabetes mellitus patients on dual antiplatelet therapy undergoing elective coronary stent implantation.     

Markedly increased serum and urinary fructose concentrations in diabetic patients with ketoacidosis or ketosis

To investigate fructose concentrations in diabetic patients with ketoacidosis or ketosis, serum fructose concentrations and daily urinary fructose excretion were measured in 23 patients with ketoacidosis (n = 16) and ketosis (n = 7) on the first day of admission. Seventeen patients were diagnosed with type 1, one patient with mitochondrial, and 4 patients with atypical diabetes. In 16 of the 23 patients, serum and urinary fructose could be assessed after starting treatments. Mean serum fructose concentration was 71.6 ± 108.1 μmol/l, and mean daily urinary fructose excretion was 352.1 ± 473.7 μmol/day. Serum fructose levels in patients with atypical diabetes were much higher (205.0 ± 213.3 μmol/l) than those in patients with type 1 diabetes (45.1 ± 44.5 μmol/l), while urinary fructose levels in atypical diabetes (249.7 ± 92.4 μmol/day) tended to be lower than those in type 1 diabetes (382.6 ± 533.2 μmol/day). Serum fructose concentrations decreased significantly (P < 0.05) from 88.1 ± 126.3 to 18.0 ± 11.0 μmol/l, and daily urinary fructose excretion also decreased significantly (P < 0.05) from 459.8 ± 530.9 to 75.1 ± 62.0 μmol/day in accordance with glycemic normalization after treatment. Marked and reversible increases in serum and urinary fructose concentrations were observed in diabetics with ketoacidosis and ketosis.     

Gender and Responses to Aspirin and Clopidogrel: Insights Using Short Thrombelastography

There is significant variability in both baseline clotting tendency and response to antiplatelet therapy. Responses are associated with outcome. We have investigated whether differences could explain the increased risk observed in women presenting with coronary artery disease. We have utilized short thrombelastography to assess (i) baseline clotting responses, (ii) response to aspirin and clopidogrel, and (iii) post‐treatment platelet reactivity in 48 young volunteers, 22 older patients and 18 patients with previous stent thrombosis. Baseline responses were significantly higher in young women than in men. While there was no difference in response to aspirin, platelet reactivity on aspirin remained higher in women (area under curve at 15 min [AUC15] of arachidonic acid channel 332 ± 122 vs. 172 ± 80, P= 0.04). Young women had less response to clopidogrel (% reduction in AUC15 with adenosine diphosphate [ADP] 36.4 ± 12.4 vs. 64.0 ± 13.2, P < 0.01) in addition to higher post‐treatment reactivity (AUC15 of ADP 714 ± 161 vs. 311 ± 146, P < 0.01) compared to men. There were no such differences between male and female patients over 50. However, young women with previous stent thrombosis had among the highest platelet reactivity observed. Compared to men, young women have greater baseline clotting tendency, reduced response to clopidogrel, and greater post‐treatment reactivity while on both aspirin and clopidogrel. Differences in clotting tendency and response to antiplatelet therapy may contribute to the excess risk observed in young women but are not observed in older female patients.     

Circulating asymmetric dimethylarginine, endothelin-1 and cell adhesion molecules in women with gestational diabetes

We measured plasma concentrations of asymmetric dimethylarginine (ADMA), endothelin-1 (ET-1), soluble vascular cell adhesion molecule-1 (sVCAM-1) and E-selectin in 56 patients with gestational diabetes (GDM), 68 pregnant women with normal glucose tolerance (NGT) and 36 healthy non-pregnant women. ADMA concentrations were markedly lower in NGT [0.48 (0.42–0.55) μmol/l] than in GDM subjects [0.50 (0.43–0.67) μmol/l] and healthy controls [0.57 (0.46–0.72) μmol/l, P = 0.005]. ET-1 levels were comparable between GDM [0.76 (0.58–0.90) pg/ml] and NGT women [0.75 (0.63–0.92) pg/ml] and significantly higher than in the non-pregnant subjects [0.62 (0.52–0.72) pg/ml, P = 0.007 and P = 0.005, respectively]. There were no differences in sVCAM-1 and E-selectin levels between the groups studied. ADMA levels were significantly associated with fasting glucose (β = 0.23, P = 0.02) and gestational age (β = 0.24, P = 0.01). Our results suggest that physiological adaptation to pregnancy is associated with a fall in circulating ADMA and an elevation of ET-1 concentrations, irrespective of the disturbances of glucose tolerance.     

Effect of clopidogrel discontinuation at 1?year after drug eluting stent placement on soluble CD40L, P-selectin and C-reactive protein levels: DECADES (Discontinuation Effect of Clopidogrel After Drug Eluting Stent): a multicenter, open-label study

Antiplatelet therapy with clopidogrel has been shown to reduce major adverse cardiac events in acute coronary syndromes and after percutaneous interventions. This effect is not only due to its anti-platelet effect but also possibly due to an anti-inflammatory effect. The effect of clopidogrel cessation after one year of therapy on markers of inflammation has been investigated in diabetics and showed an increase in platelet aggregation as well as hsCRP and surface P-selectin levels. This was an exploratory multicenter prospective open-label single arm study of 98 non-diabetic patients who had received one or more drug eluting stents and were coming to the end of their 12 months course of clopidogrel therapy. The effect of clopidogrel cessation on expression of biomarkers: sCD40L, soluble P-selectin and hsCRP was measured right before clopidogrel cessation (day 0), and subsequently at 1, 2, 3 and 4 weeks after drug withdrawal. A median increase in sCD40L expression from 224 to 324.5 pg/ml was observed between baseline and 4 weeks after clopidogrel cessation, which corresponded to a 39% mean percent change based on an ANCOVA model (P < 0.001). Over the 4 weeks observation period the change in sCD40L expression correlated weakly with soluble P-selectin levels (at 4 weeks Spearman’s correlation coefficient = 0.32; P = 0.0024). Increase in P-selectin expression from baseline was statistically significant at week 1 and 2. Conversely, hsCRP level decreased by 21% at 1 week (P = 0.008) and was still reduced by 18% by 4 weeks (P = 0.062). The change in sCD40L expression appeared to vary with the type of drug eluting stent. Patients treated with drug eluting stents at 1 year after implantation display significant increase in sCD40L and decrease in hsCRP after clopidogrel cessation. Further studies should elucidate if this increase in sCD40L levels reflects solely the removal of the inhibitory effects of clopidogrel on platelet activity or rather an increase in pro-inflammatory state. The latter hypothesis may be less likely given decrease in hsCRP levels. Randomized studies are urgently needed to establish potential link of clopidogrel discontinuation and vascular outcomes.     

Asymptomatic Mongolian middle-aged women with high homocysteine blood level and atherosclerotic disease

Growing numbers of studies have shown that hyperhomocysteinemia is an independent, modifiable risk factor for cardiovascular diseases. Hyperhomocysteinemia has been found to be negatively associated with the vitamin B group, especially folate and cobalamin. Because of the relative scarcity of fruits and vegetables in Mongolian foods, and the high cardiovascular diseases rate in Mongolia, we examined homocysteine level and its relation with atherosclerotic change in middle-aged Mongolian women. This cross-sectional study included 79 female asymptomatic residents of Ulaanbaatar, Mongolia. Besides analysis of homocysteine and chemistry tests, participants were interviewed and underwent physical and Doppler ultrasound examination of extracranial vessels. The mean homocysteine level was 9.87 ± 3.6 μmol/l, and the 2.5th and 97.5th percentiles were 2.2 μmol/l and 19.9 μmol/l. Participants with abnormal Doppler ultrasound finding had significantly higher homocysteine levels (12.8 ± 4.5 μmol/l vs 8.7 ± 2.3 μmol/l, P < 0.001) and homocysteine was significantly associated with having atherosclerotic change (odds ratio 2.2, 95% confidence interval = 1.42–3.49, P < 0.001) after adjustment for age, low-density lipoprotein, diastolic blood pressure, and body mass index. Hyperhomocysteinemia was found to be significantly associated with atherosclerotic change in female Mongolian adults. Further studies are necessary to determine factors associated with homocysteine elevation among the Mongolian population.