Effects of n-3 PUFA on endothelial function in patients with peripheral arterial disease: a randomised, placebo-controlled, double-blind trial.

As only limited evidence is available for potential benefits of n-3 PUFA supplementation in patients with peripheral arterial disease (PAD), we studied the effects of 4 g n-3 PUFA on endothelial function and inflammatory markers. Seventy patients with stable PAD classified as Rutherford stage 2 or 3 and good control of cardiovascular factors were randomised to receive either 4 g n-3 PUFA or placebo daily for 3 months in a double-blind fashion. Primary endpoint was endothelial function assessed by flow-mediated vasodilation (FMD). In addition, ankle-brachial index, maximum and pain-free walking distances were determined. Lipid parameters including the omega-3 index reflecting n-3 PUFA intake as well as pro-inflammatory, endothelial and platelet activation markers were measured over the same time interval. After 3 months of treatment with 4 g n-3 PUFA daily, a significant improvement of FMD was observed compared with placebo (n-3 PUFA, median Δ 3·7 (interquartile range (IQR) -1·8, 7·1) % v. placebo, Δ -0·5 (IQR -6·5, 3·0) %, P = 0·01 between the groups). After a 3-month washout period, this benefit was not sustained (n-3 PUFA, median Δ 0·6 (IQR -2·2, 5·6) % v. placebo, Δ -0·9 (IQR -6·6, 6·7) %, P = 0·20). In response to n-3 PUFA, an improvement of lipid parameters with a pronounced increase in the omega-3 index was seen. No changes were found for other parameters. In conclusion, in patients with PAD, 4 g/d n-3 PUFA improved cardiovascular risk in PAD patients, which needs testing in large-scale trials.

Disaggregation Following Agonist-Induced Platelet Activation in Patients on Dual Antiplatelet Therapy.

Disaggregation as the difference between maximal and final platelet aggregation by light transmission aggregometry indicates the stability of platelet aggregates. We evaluated the extent of disaggregation after platelet stimulation with adenosine diphosphate (ADP), arachidonic acid (AA), collagen, epinephrine, and thrombin receptor-activating peptide (TRAP)-6 in 323 patients on dual antiplatelet therapy with daily aspirin and clopidogrel (group 1), prasugrel (group 2), or ticagrelor (group 3) therapy. All patients in group 1 underwent elective angioplasty and stenting, whereas all patients included in groups 2 and 3 suffered from acute coronary syndromes (STEMI or NSTEMI) and underwent urgent PCI. Significant differences between maximal and final platelet aggregation were observed with all agonists throughout the groups (all p<0.001). Disaggregation was highest using AA (clopidogrel 36.5%; prasugrel/ticagrelor 100%) and ADP (clopidogrel 21.7%; prasugrel/ticagrelor 100%). In contrast, low disaggregation was observed after platelet stimulation with collagen and TRAP-6 in clopidogrel-treated patients, and after platelet stimulation with collagen and epinephrine in prasugrel- and ticagrelor-treated patients. In conclusion, pathways of platelet activation that are not inhibited by standard antiplatelet therapy allow persisting platelet aggregation and may at least in part be responsible for adverse ischemic events.

The role of intraluminal thrombus formation for expansion of abdominal aortic aneurysms.

BACKGROUND: Though the pathophysiology of initiation, formation, and expansion of abdominal aortic aneurysm (AAA) has been intensely researched, the distinct mechanisms driving these processes still remain unclear. In particular, human studies on predictors of AAA progression as a major determinant of rupture risk are scarce. METHODS: All consecutive abdominal aortic ultrasound sonographic examinations performed at the duplex laboratory of the Division of Angiology of the Medical University of Vienna between 1999 and 2012 were reviewed. Patients with repeated measurements of the infrarenal aortic diameter, who had no prior AAA repair were included. Detailed informations on AAA, including length, anterior-posterior and transversal measurements of diameter, and intraluminal thrombus formation/size were obtained from ultrasound examination; patients' comorbidities, cardiovascular risk factors, and medications were obtained from outpatient charts. The expansion rate of AAA in relation to intraluminal thrombus size, gender, age, comorbidities, cardiovascular risk factors, and pharmacotherapy was evaluated. Independent predictors of AAA growth were identified through mixed effects models. RESULTS: In total, 166 patients (123 men and 43 women, mean age 68 ± 9 years) were included. Patients were followed over a mean period of 1.4 ± 1.2 years with a mean number of follow-up investigations of 4.4 ± 2.7. Overall, mean maximum AAA diameter at baseline was 37.4 ± 8.2 mm. The average expansion rate of AAA diameter throughout the follow-up period was 2.0 mm per year (95 % confidence interval: 1.6-2.4). At initial investigation, intraluminal thrombus formation was present in 56.6 % of all patients. AAA diameter at baseline, time of follow-up as well as presence and size of intraluminal thrombus formation were identified as independent predictors of AAA expansion rate. Importantly, gender and presence of cardiovascular risk factors were not associated with AAA progression rate. CONCLUSIONS: Intraluminal thrombus formation seems to be a key determinant for progression of AAA diameter. Further prospective longitudinal studies are warranted to confirm the potential impact of thrombus formation on AAA development and its implication on monitoring and treatment decisions in patients with AAA.

Interleukin-6 and asymmetric dimethylarginine are associated with platelet activation after percutaneous angioplasty with stent implantation.

Data linking in vivo platelet activation with inflammation and cardiovascular risk factors are scarce. Moreover, the interrelation between endothelial dysfunction as early marker of atherosclerosis and platelet activation has not been studied, so far. We therefore sought to investigate the associations of inflammation, endothelial dysfunction and cardiovascular risk factors with platelet activation and monocyte-platelet aggregate (MPA) formation in 330 patients undergoing angioplasty with stent implantation for atherosclerotic cardiovascular disease. P-selectin expression, activation of glycoprotein IIb/IIIa and MPA formation were determined by flow cytometry. Interleukin (IL)-6, high sensitivity C-reactive protein and asymmetric dimethylarginine (ADMA) were measured by commercially available assays. IL-6 was the only parameter which was independently associated with platelet P-selectin expression and activated GPIIb/IIIa as well as with leukocyte-platelet interaction in multivariate regression analysis (all p<0.05). ADMA was independently associated with GPIIb/IIIa activation (p<0.05). Patients with high IL-6 exhibited a significantly higher expression of P-selectin than patients with low IL-6 (p=0.001), whereas patients with high ADMA levels showed a more pronounced activation of GPIIb/IIIa than patients with low ADMA (p=0.003). In conclusion, IL-6 and ADMA are associated with platelet activation after percutaneous angioplasty with stent implantation. It remains to be established whether they act prothrombotic and atherogenic themselves or are just surrogate markers for atherosclerosis with concomitant platelet activation.

Wall shear stress in the stented superficial femoral artery in peripheral arterial disease.

OBJECTIVE: Local changes in wall shear stress (WSS) contribute to vascular wall thickening and subsequent stenosis. Restenosis after stenting is a major concern, especially in the superficial femoral artery (SFA) of patients with peripheral arterial disease (PAD). Local alterations in WSS after stenting might contribute to restenosis/reocclusion. To test the hypothesis that WSS is impaired along the stented SFA segment, we studied the profile of WSS along the femoro-popliteal axis after stent placement in a cross-sectional design. METHODS: Eighty-seven patients with PAD (89 limbs) were included one day after stenting of the SFA. Flow velocities (peak and mean) and vessel diameter were measured by duplex ultrasound in five predefined segments along the femoro-popliteal axis, at rest and after exercise (30 toe raises); WSS (peak and mean) was calculated from flow velocities, vessel diameter and whole blood viscosity. RESULTS: WSS progressively declined along the stented segment at rest (peak WSS, p < 0.0001; mean WSS, p < 0.05); after exercise, WSS increased in all segments (all p < 0.001), but, again, progressively declined along the stent (peak WSS, p < 0.0001; mean WSS, p < 0.05). The internal vessel diameter remained unchanged after exercise in the stented and in the non-stented parts of the femoro-popliteal axis (all p > 0.05). CONCLUSION: In PAD patients with SFA stenting WSS is impaired along the femoro-popliteal axis. The consequences of this finding in terms of local effects on the vessel wall that might favor restenosis/reocclusion needs further investigation.

Chronic kidney disease is associated with increased platelet activation and poor response to antiplatelet therapy.

BACKGROUND: Chronic kidney disease (CKD) is a common co-morbidity of patients with atherosclerotic vascular disease, and may influence the response to antiplatelet therapy. We, therefore, sought to investigate its effect on platelet activation and on-treatment residual platelet reactivity. METHODS: We assessed platelet activation and the response to clopidogrel and aspirin in 316 patients after percutaneous intervention with stent implantation. CKD was defined as a glomerular filtration rate <60 mL/min/1.73 m(2) according to the Modification of Diet in Renal Disease formula. Surface expression of activated glycoprotein IIb/IIIa without the addition of agonists was determined to assess baseline platelet activation. GPIIb/IIIa in response to adenosine diphosphate (ADP) and arachidonic acid (AA), as well as the VerifyNow assays and light transmission aggregometry (LTA) were used to measure residual platelet reactivity. RESULTS: Baseline platelet activation was significantly increased in CKD patients compared with patients without renal insufficiency [3.1 versus 2.7 mean fluorescence intensity (MFI), P = 0.001]. Moreover, patients with CKD exhibited a more pronounced expression of GPIIb/IIIa in response to ADP (13 versus 9.6 MFI) and AA (6 versus 5.1 MFI; both P≤ 0.02) than patients without CKD. In the VerifyNow assays, CKD patients showed significantly higher platelet reactivity than patients without CKD (P2Y12 assay: 239 versus 182 P2Y12 Reaction Units; aspirin assay: 415 versus 399 Aspirin Reaction Units; both P≤ 0.03). Further, patients with CKD had significantly higher platelet reactivity by LTA in response to ADP (49.9 versus 43.2%, P = 0.01). Finally, high on-treatment residual ADP-inducible platelet reactivity by the VerifyNow P2Y12 assay and by LTA occurred significantly more frequent in patients with CKD (VerifyNow: 52.2 versus 26.2%, P < 0.001; LTA: 23.3 versus 12.1%, P = 0.01). CONCLUSIONS: Patients with CKD exhibit increased platelet activation, and an attenuated response to dual antiplatelet therapy compared with patients without renal insufficiency.

Impact of diabetes on platelet activation in different manifestations of atherosclerosis.

BACKGROUND: Atherosclerosis affects many patients with type 2 diabetes. Both are associated with platelet activation, but it remains unclear how diabetes contributes to, or even enhances, platelet activation in patients with atherosclerosis. We therefore investigated the impact of diabetes on platelet activation and protease activated receptor-1 (PAR-1) mediated platelet response in patients with symptomatic coronary artery disease (CAD), as compared with other manifestations of atherosclerosis. METHODS: Baseline P-selectin expression, thrombin receptor activating peptide-6 (TRAP-6) inducible P-selectin, and relative increase of platelet P-selectin after activation with TRAP-6 were measured using flow cytometry in platelets from 317 patients after angioplasty and stenting for symptomatic atherosclerotic disease, and from 50 healthy controls. RESULTS: Patients with symptomatic atherosclerosis exhibited significantly higher levels of baseline P-selectin expression, TRAP-6-inducible P-selectin and relative increase of platelet P-selectin after stimulation with TRAP-6 than healthy controls. Patients with symptomatic peripheral artery disease or cerebrovascular disease (PAD/CVD) had higher levels of platelet activation and PAR-1-mediated platelet reactivity than patients with symptomatic CAD. Of interest, CAD patients with diabetes responded more strongly to TRAP-6 than those without diabetes, and their platelet activation and PAR-1-mediated platelet reactivity resembled those from PAD/CVD patients. CONCLUSION: Compared with healthy controls, platelets from patients with symptomatic atherosclerotic disease are activated and susceptible to PAR-1-mediated activation. Diabetes affects platelet reactivity only in patients with symptomatic CAD, while other manifestations of atherosclerosis may have an overwhelming effect on platelet reactivity that is not further enhanced by diabetes.

Differential impact of inflammation on six laboratory assays measuring residual arachidonic acid-inducible platelet reactivity during dual antiplatelet therapy.

AIMS: Inflammation has been postulated to modify the platelet response to aspirin treatment, thereby causing high on-treatment residual platelet reactivity (HRPR). Both high levels of inflammatory markers and HRPR have been linked to adverse cardiovascular events. We aimed to study the impact of inflammation on residual arachidonic acid (AA)-inducible platelet reactivity. METHODS: In 288 patients receiving dual antiplatelet therapy, residual AA-inducible platelet reactivity was assessed using light transmission aggregometry (LTA), the VerifyNow assay, multiple electrode aggregometry (MEA) and the Impact-R. The levels of urinary 11-dehydro-thromboxane B2 (D-TXB2), serum thromboxane B2 (TXB2), interleukin-6 (IL-6) and high-sensitivity C-reactive protein (hsCRP) were determined using immunoassays. RESULTS: The IL-6 level was found to be an independent predictor of platelet reactivity as determined according to LTA and D-TXB2 using a multiple linear regression analysis. Accordingly, patients with supramedian IL-6 levels exhibited significantly higher platelet reactivity than patients with inframedian IL-6 levels when determined according to LTA and D-TXB2 (both p ≤0.02). High IL-6 levels were associated with a 3.6-fold (95%CI 2.1-6.4) increased risk of HRPR, as defined according to D-TXB2, and a 3.4-fold (95%CI 1.4-8.3) increased risk of HRPR, as defined according to MEA. The HsCRP level was found to be an independent predictor of platelet reactivity when determined according to LTA, D-TXB2, the Impact-R and TXB2 using a multiple linear regression analysis. High hsCRP levels were associated with a 3.6-fold (95%CI 1.3-10) increased risk of HRPR, as defined according to LTA, and a 2.5-fold (95%CI 1.3-4.6) increased risk of HRPR, as defined according to TXB2. CONCLUSIONS: Increased levels of inflammatory markers are independently associated with residual AA-inducible platelet reactivity in patients receiving dual antiplatelet treatment.

Preserved thrombin-inducible platelet activation in thienopyridine-treated patients.

BACKGROUND: Abundant thrombin generation may be a major reason for subsequent thromboembolic events in patients with cardiovascular disease receiving dual antiplatelet therapy. We therefore investigated the susceptibility of thienopyridine responders and nonresponders to thrombin receptor-activating peptide (TRAP)-6- and adenosine diphosphate (ADP)-inducible platelet activation. MATERIALS AND METHODS: Response to clopidogrel or prasugrel was determined by the vasodilator-stimulated phosphoprotein (VASP) phosphorylation assay and multiple electrode aggregometry (MEA) in 317 patients undergoing angioplasty and stenting for cardiovascular disease. Baseline, TRAP-6-, and ADP-inducible P-selectin expression, activated glycoprotein IIb/IIIa (GPIIb/IIIa) and monocyte-platelet aggregate (MPA) formation were measured as sensitive parameters of platelet activation. RESULTS: In patients with high on-treatment residual ADP-inducible platelet reactivity (HRPR), baseline P-selectin expression, GPIIb/IIIa and MPA formation were similar to those in patients without HRPR (all P > 0.05). After platelet activation with TRAP-6 or ADP, patients with HRPR by both assays exhibited significantly higher levels of P-selectin expression, GPIIb/IIIa and MPA formation than patients with an adequate thienopyridine-mediated platelet inhibition (all P ≤ 0.02). However, high levels of TRAP-6-inducible P-selectin, GPIIb/IIIa and MPA formation also occurred in 20.4%, 19.1% and 20.1% of the good responders by the VASP assay, and in 19.6%, 16.6% and 20.6% of the good responders by MEA, respectively. CONCLUSIONS: Thienopyridine nonresponders are more susceptible to thrombin- and ADP-inducible platelet activation than patients with good platelet inhibition. However, even patients with adequate thienopyridine-mediated platelet inhibition often show a preserved responsiveness to thrombin. These patients may benefit from additional thrombin receptor blockage or inhibition of thrombin generation.

Response to antiplatelet therapy is independent of endogenous thrombin generation potential.

BACKGROUND: Thrombin is the most potent platelet activator, and achieves rapid platelet activation even in the presence of antiplatelet therapy. Since activated platelets respond stronger to additional stimuli, the extent of endogenous thrombin generation may in part be responsible for the reported response variability to aspirin and clopidogrel therapy. PATIENTS AND METHODS: Thrombin generation potential was measured with a commercially available assay, and platelet reactivity was assessed with the vasodilator-stimulated phosphoprotein (VASP) phosphorylation assay, light transmission aggregometry (LTA), the VerifyNow aspirin and P2Y12 assays, and multiple electrode aggregometry (MEA) in 316 patients on dual antiplatelet therapy undergoing angioplasty and stenting. RESULTS: Peak thrombin, the lag phase and the area under the curve of thrombin generation correlated poorly with on-treatment platelet reactivity by all test systems. High on-treatment residual platelet reactivity (HRPR) in response to arachidonic acid was seen in 33 (10.5%), 41 (13%), and 79 (25.7%) patients by LTA, the VerifyNow aspirin assay, and MEA, respectively. HRPR in response to adenosine diphosphate was seen in 150 (48.1%), 48 (15.3%), 106 (33.7%), and 118 (38.3%) patients by the VASP assay, LTA, the VerifyNow P2Y12 assay, and MEA, respectively. Peak thrombin generation did not differ between patients without and with HRPR by the VASP assay, LTA, the VerifyNow P2Y12 assay and MEA. In the VerifyNow aspirin assay, patients without HRPR had higher peak thrombin generation than patients with HRPR (p=0.01). Finally, patients without and with high peak thrombin generation exhibited similar on-treatment platelet reactivity by all test systems, and high peak thrombin generation occurred to a similar extent in patients without and with HRPR. CONCLUSION: Response to antiplatelet therapy with aspirin and clopidogrel is not associated with thrombin generation potential.

Effect of conversion from ciclosporin to tacrolimus on endothelial progenitor cells in stable long-term kidney transplant recipients.

BACKGROUND: Endothelial progenitor cell (EPC) counts are proposed surrogate markers for vascular function and cardiovascular risk. The effect of tacrolimus (TAC) on EPC is unknown. METHODS: In this randomized controlled trial, we assigned 148 stable long-term kidney transplant recipients (KTR) to maintaining ciclosporin (CSA) or to commencing TAC-based immunosuppression at a 2:1 ratio. EPC counts (CD34/KDR) after 24 months were defined as primary endpoint. RESULTS: The intent-to-treat analysis included 141 KTR (estimated glomerular filtration rate, 46.7 [40.1-61.8] mL/min per 1.73 m). Median (interquartile range [IQR]) EPC counts at baseline and month 24 were 6 (2-9) and 3 (1-9) cells and 4 (2-8) and 2 (0-5) cells per 5×10 mononuclear cells in CSA and TAC, respectively. Median (IQR) circulating angiogenic cells at baseline and month 24 were 28 (10.7-57) and 44.33 (14.6-59.8) cells and 22 (10.8-41) and 21 (9.7-49.5) cells per high-power field in CSA and TAC, respectively. Median (IQR) endothelial cell colony-forming units count per well at baseline and month 24 were 10.5 (3.3-34.3) and 4.38 (1.7-26.5) in CSA and significantly declined from 9.31 (1.8-29.3) to 4.13 (1.1-9.5) in TAC (P=0.003). There were no cardiovascular events in either group. CONCLUSION: Although late conversion from CSA to TAC appears safe in KTR, conversion to TAC has no favorable effect on EPC. Low EPC levels are associated with a higher risk of subsequent cardiovascular events and are therefore of prognostic value. Their trend to decline over time deserves further examination.

Obesity is associated with poor response to clopidogrel and an increased susceptibility to protease activated receptor-1 mediated platelet activation.

Obesity is associated with a prothrombotic state resulting from increased thrombin generation, platelet hyper-reactivity, and decreased fibrinolysis. Data on the influence of obesity on clopidogrel-mediated platelet inhibition are conflicting and limited to platelet function tests. Moreover, there are no data on thrombin-inducible platelet activation in obese patients. We therefore investigated response to clopidogrel therapy and protease activated receptor (PAR)-1 mediated platelet activation in obese and nonobese patients undergoing angioplasty and stenting for cardiovascular disease. The vasodilator-stimulated phosphoprotein (VASP) phosphorylation assay, multiple electrode aggregometry (MEA) with adenosine diphosphate (ADP), and surface expressions of P-selectin and activated glycoprotein (GP) IIb/IIIa in response to ADP and thrombin receptor activating peptide (TRAP)-6 were assessed in 71 obese and 245 nonobese patients. Obesity was independently associated with higher residual platelet reactivity by the VASP assay and MEA ADP, and with platelet surface expressions of P-selectin and activated GPIIb/IIIa in response to ADP (all P ≤ 0.04). Further, high on-treatment residual ADP-inducible platelet reactivity by the VASP assay and by MEA ADP were significantly more frequent in obese patients compared with nonobese patients (both P ≤ 0.04). Finally, PAR-1 mediated platelet activation as assessed by expression of P-selectin and activated GPIIb/IIIa in response to TRAP-6 was significantly more pronounced in obese patients than in patients without obesity (both P ≤ 0.02). In conclusion, obese patients undergoing angioplasty and stenting exhibit a diminished response to clopidogrel and an increased susceptibility to TRAP-6 inducible platelet activation.

Differential impact of cytochrome 2C9 allelic variants on clopidogrel-mediated platelet inhibition determined by five different platelet function tests.

BACKGROUND: The antiplatelet effect of clopidogrel is subject to considerable inter-individual variations. In vitro high on-treatment residual platelet reactivity (HRPR) has been linked to cytochrome P450 (CYP) 2C19*2 carriage, and both were significantly associated with the occurrence of adverse events after coronary stenting. It has been shown that besides CYP2C19, CYP2C9 is involved in the hepatic biotransformation of clopidogrel to its active metabolite. Consequently, CYP2C9 polymorphisms may also affect the extent of clopidogrel-mediated platelet inhibition. We therefore studied the influence of CYP2C9 allelic variants on clopidogrel-mediated platelet inhibition as assessed by 5 platelet function tests. METHODS: On-clopidogrel residual platelet reactivity was assessed by light transmission aggregometry (LTA), the VerifyNow P2Y12 assay, the VASP assay, multiple electrode aggregometry (MEA), and the Impact-R in 288 patients after angioplasty and stenting for cardiovascular disease. Allelic variants CYP2C9*2 and *3 were determined using a RealTime PCR assay. RESULTS: A significantly higher on-treatment platelet reactivity was found for patients with loss-of-function (LOF) status (wt/*3, *2/*2, *3/*3) compared to normal-function genotype (wt/wt, wt/*2) using the VerifyNow assay (P=0.01). An in trend increase was seen with LTA (P=0.06) while results did not differ for the VASP assay, MEA or the Impact-R. Further, in univariate and multivariable logistic regression analysis the LOF genotype was associated with HRPR determined by the VerifyNow P2Y12 assay (P=0.02) but not by any other assay. CONCLUSION: Results from the VerifyNow P2Y12 assay are significantly influenced by CYP2C9 LOF variants leading to decreased clopidogrel-mediated platelet inhibition and an increased rate of HRPR.

A high maintenance dose increases the inhibitory response to clopidogrel in patients with high on-treatment residual platelet reactivity.

BACKGROUND: Patients with high on-treatment residual adenosine diphosphate-inducible platelet reactivity (HRPR) despite clopidogrel therapy are at an increased risk for adverse events after coronary stenting. A higher maintenance dose of clopidogrel may increase the inhibitory response in these patients. METHODS: We randomly assigned 46 patients with HRPR in at least one of three platelet reactivity tests to 75 mg vs. 150 mg clopidogrel for 3 months after angioplasty and stenting for cardiovascular disease. Platelet reactivity was assessed by the VerifyNow P2Y12 assay, the vasodilator-stimulated phosphoprotein (VASP) phosphorylation assay, and multiple electrode aggregometry (MEA) 24h and 3 months after the intervention. RESULTS: Baseline platelet reactivity data did not differ significantly between treatment groups (all p > 0.2). At 3 months, platelet reactivities by the VerifyNow P2Y12 assay, the VASP assay, and MEA were 262 ± 74 P2Y12 reaction units (PRU), 59.5 ± 21.3%, and 46 ± 19 aggregation units (AU) in the standard dose group vs. 190 ± 78 PRU, 36.1 ± 16.8%, and 26 ± 16 AU in the high maintenance dose group (all p ≤ 0.003). Further, HRPR was significantly less frequent in patients assigned to 150 mg clopidogrel compared to patients receiving 75 mg clopidogrel per day (33% vs. 87%; p < 0.001). CONCLUSION: A high maintenance dose increases the antiplatelet effects of clopidogrel in patients with HRPR after angioplasty and stenting for cardiovascular disease. However, it needs to be shown that the higher dosage is associated with a beneficial clinical outcome in these patients.

Influence of cytochrome 2C19 allelic variants on on-treatment platelet reactivity evaluated by five different platelet function tests.

BACKGROUND: The antiplatelet effect of clopidogrel has been linked to cytochrome P450 2C19 (CYP2C19) carrier status. The presence of loss of function and gain of function variants were found to have a gene-dose effect on clopidogrel metabolism. However, genotyping is only one aspect of predicting response to clopidogrel and several platelet function tests are available to measure platelet response. Patients and methods We studied the influence of CYP2C19 allelic variants on on-treatment platelet reactivity as assessed by light transmission aggregometry (LTA), the VerifyNow P2Y12 assay, the VASP assay, multiple electrode aggregometry (MEA), and the Impact-R in 288 patients after stenting for cardiovascular disease. Allelic variants of CYP2C19 were determined with the Infiniti® CYP450 2C19+ assay and categorized into four metabolizer states (ultrarapid, extensive, intermediate, poor). RESULTS: Platelet reactivity increased linearly from ultrarapid to poor metabolizers using the VerifyNow P2Y12 assay (P = 0.04), the VASP assay (P = 0.02) and the Impact-R (P = 0.04). The proportion of patients with high on-treatment residual platelet reactivity (HRPR) identified by LTA, the VerifyNow P2Y12 assay and the VASP assay increased when the metabolizer status decreased, while no such relationship could be identified for results of MEA and Impact-R. The presence of loss of function variants (*2/*2, *2-8*/wt, *2/*17) was an independent predictor of HRPR in LTA and the VASP assay while it did not reach statistical significance in the VerifyNow P2Y12 assay, MEA, and the Impact-R. CONCLUSION: Depending on the type of platelet function test differences in the association of on-treatment platelet reactivity with CYP2C19 carrier status are observed.

Soluble p-selectin, D-dimer, and high-sensitivity C-reactive protein after acute deep vein thrombosis of the lower limb.

BACKGROUND: Soluble p-selectin (sP-selectin), D-dimer, and C-reactive protein (CRP) are elevated in deep vein thrombosis (DVT), and may play a role as risk predictors of recurrent venous thromboembolism. However, these parameters have only been assessed at manifestation or at single time points after DVT so far. We therefore investigated the course of sP-selectin, D-dimer, and high-sensitivity (hs)-CRP after acute unprovoked DVT of the lower limb. METHODS: In this prospective, longitudinal study, sP-selectin, D-dimer, and hs-CRP were determined by enzyme-linked immunosorbent assay, quantitative latex assay, and particle enhanced immunonephelometry, respectively, in 44 patients with sonographically confirmed acute DVT at the time of diagnosis, and 1, 3, 6, and 12 months later. sP-selectin and hs-CRP were also measured in 88 age- and gender-matched healthy controls. Further, color duplex sonography was performed in all patients at each time point. RESULTS: At DVT diagnosis, sP-selectin and hs-CRP were significantly higher in patients compared with healthy controls. From baseline to 1 month, both parameters decreased significantly. In patients with oral anticoagulation (OAC) for 6 months (n = 35), levels of sP-selectin increased significantly after cessation of anticoagulant therapy (P = .002), while sP-selectin was similar to healthy controls in patients with ongoing OAC (n = 9) at 12 months (P = .49). In contrast, hs-CRP in both subgroups remained constantly low at levels seen in healthy controls. The course of D-dimer was similar to sP-selectin. Color duplex sonography showed no ongoing thrombus formation in any patient. Thirty-four (77.3%), 29 (65.9%), 26 (59.1%), and 25 (56.8%) patients had residual thrombosis 1, 3, 6, and 12 months after the acute event, respectively. D-dimer was significantly higher in patients with residual thrombosis compared with patients without residual thrombosis 1 month after DVT (0.58 µg/mL [range, 0.2-9.67 µg/mL] vs 0.25 µg/mL [range, 0.2-0.62 µg/mL]; P = .02). At all other time points, the levels of D-dimer and sP-selectin did not differ significantly between patients without and with residual thrombosis (all P > .05). CONCLUSIONS: Concentrations of sP-selectin and D-dimer after acute DVT seem to be strongly influenced by treatment with vitamin K antagonists. After withdrawal of oral anticoagulation, they rise again and could therefore reflect a prothrombotic state, which is susceptible to pharmacologic therapy.

The influencing factors for clopidogrel-mediated platelet inhibition are assay-dependent.

BACKGROUND: Influencing factors for clopidogrel-mediated platelet inhibition have only been evaluated by one or two different test systems in the same population so far. Since previous studies revealed poor correlations between the various platelet function tests, the identification of influencing variables for clopidogrel response may vary from one test system to the next. We therefore investigated whether the influencing factors for clopidogrel-mediated platelet inhibition depend on the used assay. PATIENTS AND METHODS: Adenosine diphosphate (ADP)-inducible platelet reactivity was assessed by light transmission aggregometry (LTA), the VerifyNow P2Y12 assay, the vasodilator-stimulated phosphoprotein (VASP) phosphorylation assay, multiple electrode aggregometry (MEA), and the Impact-R in 288 patients after angioplasty and stenting for cardiovascular disease. By univariate and multivariate regression analyses, we evaluated the impact of age ≥ 75, gender, body mass index (BMI), diabetes, active smoking, hypertension, hyperlipidemia, C-reactive protein, platelet count, creatinine, use of calcium-channel blockers (CCBs), statins, proton pump inhibitors, beta blockers, angiotensin converting enzyme inhibitors, and angiotensin receptor blockers on clopidogrel-mediated platelet inhibition in each test system. RESULTS: None of the independent influencing variables was consistent through all test systems. Only by LTA and the VerifyNow P2Y12 assay, age ≥ 75 and the use of CCBs were independently associated with higher on-treatment platelet reactivity. Only by the VASP assay and MEA, on-treatment platelet reactivity increased linearly with BMI. Further, only by MEA, residual ADP-inducible platelet reactivity increased linearly with platelet count, whereas an increase in platelet count was independently associated with a decrease in ADP-inducible platelet activation by the Impact-R. CONCLUSION: The influencing factors for platelet reactivity during clopidogrel therapy are assay-dependent.

Platelet-monocyte cross talk and tissue factor expression in stable angina vs. unstable angina/non ST-elevation myocardial infarction.

Tissue factor (TF), the major procoagulant in vivo, is usually absent from blood cells. However, since both monocyte TF (MoTF) expression and platelet activation are present in acute coronary syndrome we hypothesized that MoTF expression may in part depend on monocyte platelet aggregate (MPA) formation in coronary artery disease (CAD). Patients with unstable angina/non-ST-elevation myocardial infarction (UA/NSTEMI, n = 20) had significantly higher levels of MoTF (17.4 ± 3.1MFI) and MPAs (CD42b:273 ± 183MFI; CD62P:256.3 ± 48.5MFI) than patients with stable angina (SA, n = 40; MoTF:13.2 ± 2.2MFI, p = 0.001; CD42b:160 ± 113MFI, p = 0.025; CD62P:118.7 ± 24.5MFI, p = 0.018) as measured by whole blood flow cytometry on CD14+-cells. TF-activity of isolated mononuclear cells (MNC) was elevated in UA/NSTEMI (75 ± 27 pg/mL) in comparison to SA (47 ± 17 pg/mL, p = 0.001) as determined by chromogenic assay, and TF mRNA expression in isolated MNC was more frequent in UA/NSTEMI than in SA (50% vs. 18.2%; p = 0.017). MoTF expression significantly correlated with the constitutive platelet marker CD42b (r = 0.69, p < 0.001) and the platelet activation marker CD62P (r = 0.47, p = 0.001) on CD14+-cells suggesting its association with MPAs in UA/NSTEMI. In addition, MoTF expression correlated with MoTF activity of isolated MNC (r = 0.41, p = 0.01) and plasma levels of the F1.2 prothrombin fragment (r = 0.35, p = 0.02). In conclusion, MoTF and MPAs are elevated in UA/NSTEMI compared with SA. MoTF expression correlates with platelet mass and activity attached to monocytes.

Exercise training increases endothelial progenitor cells and decreases asymmetric dimethylarginine in peripheral arterial disease: a randomized controlled trial.

BACKGROUND: Supervised exercise training (SET) is recommended as initial treatment to improve walking capacity in peripheral arterial disease (PAD) patients with intermittent claudication. Various mechanisms by which SET yields beneficial effects are postulated, however data regarding its influence on angiogenesis are scarce. Thus, we designed a prospective randomized controlled trial to study the impact of SET on markers of angiogenesis and endothelial function in PAD. METHODS: Forty PAD patients were randomized to SET on top of best medical treatment (SET+BMT) for 6 months versus best medical treatment (BMT) only. Endothelial progenitor cells (EPC) were assessed by whole-blood flow cytometry (co-expression of CD34+ CD133+ KDR+) and cell culture assays (endothelial cell-colony forming units, circulating angiogenic cells, migration assay) at baseline, 3, 6 and 12-months after inclusion. Changes of plasma levels of asymmetric dimethylarginine (ADMA), vascular endothelial growth factor (VEGF), stromal cell-derived factor-1 (SDF-1) and maximum walking distance were determined. RESULTS: EPC - measured by flow cytometric and cell culture techniques - increased significantly upon training paralleled by a significant decrease of ADMA when compared to the BMT group (p<0.05). Six months after training cessation, the beneficial effect of SET on EPC diminished, but maximum walking distance was significantly improved compared to baseline and controls (p<0.05). No significant changes were observed for VEGF and SDF-1 plasma levels in time course. CONCLUSIONS: SET increases circulating EPC counts and decreases ADMA levels reflecting enhanced angiogenesis and improved endothelial function, which might contribute to cardiovascular risk reduction.

The P-selectin gene Pro715 allele and low levels of soluble P-selectin are associated with reduced P2Y12 adenosine diphosphate receptor reactivity in clopidogrel-treated patients.

OBJECTIVE: To investigate the interrelation between the P-selectin gene (SELP) Pro715 allele, P2Y12 adenosine diphosphate (ADP) receptor reactivity and levels of soluble P-selectin (sP-selectin) in clopidogrel treated patients. METHODS: The Pro715 allele within SELP was tested by allele specific PCR, sP-selectin was determined by ELISA, and P2Y12 receptor reactivity was analyzed by the VASP assay in 156 patients after angioplasty and stenting. RESULTS: Carriers of the SELP Pro715 allele had significantly lower levels of sP-selectin and P2Y12 receptor reactivity, and high on-treatment residual P2Y12 receptor reactivity (HRPR) was significantly less frequent compared to non-carriers (both p<0.05). Further, patients within the lowest quartile of sP-selectin had significantly lower reactivity values and also less often HRPR compared to patients with higher sP-selectin (both p<0.01). CONCLUSION: The SELP Pro715 allele is linked to low levels of sP-selectin, and both are associated with decreased P2Y12 ADP receptor reactivity in patients on clopidogrel therapy.