Heterogeneity after harmonisation: A retrospective cohort study of bleeding and stroke risk after the introduction of direct oral anticoagulants in four Western European countries.

PURPOSE: Database heterogeneity can impact effect estimates. Harmonisation provided by common protocols and common data models (CDMs) can increase the validity of pharmacoepidemiologic research. In a case study measuring the changes in the safety and effectiveness of stroke prevention therapy after the introduction of direct oral anticoagulants (DOACs), we performed an international comparison. METHODS: Using data from Stockholm, Denmark, Scotland and Norway, harmonised with a common protocol and CDM, two calendar-based cohorts were created: 2012 and 2017. Patients with a diagnosis code of atrial fibrillation 5 years preceding the 1-year cohort window were included. DOAC, vitamin K antagonist and aspirin treatment were assessed in the 6 months prior to the start of each year while strokes and bleeds were assessed during the year. A Poisson regression generated incidence rate ratios (IRRs) to compare outcomes from 2017 to 2012 adjusted for changes in individual-level baseline characteristics. RESULTS: In 280 359 patients in the 2012 cohort and 356 779 in the 2017 cohort, treatment with OACs increased on average from 45% to 65%, while treatment with aspirin decreased from 30% to 10%. In all countries except Scotland, there were decreases in the risk of stroke and no changes in bleeding risk, after adjustment for changes in baseline characteristics. In Scotland, major bleeding (IRR 1.09, 95% confidence interval [CI] [1.00; 1.18]) and intracranial haemorrhage (IRR 1.31, 95% CI [1.13; 1.52]) increased from 2012 to 2017. CONCLUSIONS: Stroke prevention therapy improved from 2012 to 2017 with a corresponding reduction in stroke risk without increasing the risk of bleeding in all countries, except Scotland. The heterogeneity that remains after methodological harmonisation can be informative of the underlying population and database.

Comparison of calibrated dilute thrombin time and aPTT tests with LC-MS/MS for the therapeutic monitoring of patients treated with dabigatran etexilate.

Ways to monitor dabigatran etexilate (DE) therapy would be useful in certain situations. Functional assays such as aPTT or Hemoclot® Thrombin Inhibitor (HTI) have been proposed to evaluate dabigatran concentrations, but previous findings are based on in vitro studies and results must be confirmed in clinical samples. The aim of this study was to compare aPTT and HTI measurements with liquid chromatography-tandem mass spectrometry (LC-MS/MS) measurements of dabigatran in plasma samples from DE treated patients. Seventy-one plasma samples were included. aPTT was performed using STA-CKPrest® and SynthASil®. HTI was performed according to instructions from the manufacturer. The LC-MS/MS method utilised dabigatran-d3 as internal standard. The plasma concentration range was 0 to 645 ng/ml as measured by LC-MS/MS. Overall, the HTI and LC-MS/MS analyses correlated well (r²=0.97). The Bland-Altman analysis showed a mean difference of 9 ng/ml (SD: 20 ng/ml). However, the HTI performed poorly at concentrations <50 ng/ml. LC-MS/MS was sensitive (limit of quantification 1.1 ng/ml) and specific for dabigatran. The aPTT methods did not correlate well with plasma concentrations measured by LC-MS/MS (r² = 0.59 with SynthASil® and 0.50 with STA-CKPrest®). In conclusion, the poor sensitivity, the important inter-individual variability, and the poor correlation with LC-MS/MS preclude the use of aPTT to estimate dabigatran concentrations. Due to its small inter-individual variability and good agreement with LC-MS/MS measurements, we recommend the use of HTI assays to rather accurately estimate concentrations of dabigatran >50 ng/ml. Quantification of lower dabigatran levels in DE-treated patients requires the "reference" LC-MS/MS method.

Influence of statin treatment on platelet inhibition by clopidogrel - a randomized comparison of rosuvastatin, atorvastatin and simvastatin co-treatment.

OBJECTIVES: Possible interactions between clopidogrel and atorvastatin, simvastatin or rosuvastatin (a 'non-CYP3A4' metabolized statin) were investigated in a randomized prospective study using sensitive and specific ex vivo platelet function tests. METHODS: Patients with coronary artery disease participating in a double-blind study comparing lipid-lowering effects of atorvastatin (20-80 mg OD; n = 22) and rosuvastatin (10-40 mg OD; n = 24) were studied before and after 2 weeks treatment with clopidogrel 75 mg OD after completed statin dose titration. In addition, 23 patients were randomized to open-label simvastatin 40 mg OD. RESULTS: Clopidogrel inhibited 10 mumol L(-1) ADP-induced platelet aggregation by 40 +/- 27%, 57 +/- 28% and 51 +/- 29%, respectively, in patients on rosuvastatin, atorvastatin and simvastatin treatment. The other platelet tests yielded similar results. No dose-dependent effects of rosuvastatin or atorvastatin co-treatment on clopidogrel efficacy were observed. CONCLUSIONS: Treatment with CYP3A4 metabolized statins, atorvastatin or simvastatin, did not attenuate the platelet inhibitory effect of clopidogrel maintenance treatment compared with the non-CYP3A4 metabolized, rosuvastatin.

Platelet hyperprocoagulant activity in Type 2 diabetes mellitus: attenuation by glycoprotein IIb/IIIa inhibition.

BACKGROUND: Platelets are hyperactive in Type 2 diabetes mellitus (T2DM), and antiplatelet treatment with glycoprotein (GP) IIb/IIIa inhibitors provides better thrombotic protection in DM than in non-diabetic subjects. OBJECTIVE: We hypothesized that diabetic platelets are hyperprocoagulant, and that this hyperactivity can be inhibited by GPIIb/IIIa blockade. METHODS: Patients with T2DM and gender/age/body mass index-matched non-diabetic controls were recruited (n = 12 for both) to study the effect of GPIIb/IIIa blockade on platelet procoagulant activity. Platelet phosphotidylserine (PS), factor (F) Va expression, and platelet-derived microparticle (PDMP) generation were measured by whole blood flow cytometry. Platelet-dependent thrombin generation and plasma clotting time were monitored in recalcified platelet-rich plasma. RESULTS: Compared to controls, basal platelet activation was similar, while thrombin receptor activating peptide stimulated activation was enhanced in patients with T2DM. Diabetic platelets also displayed more profound elevations of platelet PS exposure, FVa binding, and PDMP generation upon stimulation. These alterations resulted in a hyperprocoagulant state, as evidenced by a marked increase in the platelet procoagulant index, enhanced thrombin generation, and a shortened plasma clotting time. GPIIb/IIIa blockade by c7E3 or SR121566 decreased platelet PS exposure and FVa binding, and diminished platelet procoagulant activity in patients with T2DM. CONCLUSIONS: Platelets have increased procoagulant activity in patients with T2DM. The hyperprocoagulant activity is counteracted by GPIIb/IIIa blockade.

Mechanisms of exercise-induced ST-segment depression in patients without typical angina pectoris.

OBJECTIVE: To evaluate if exercise-induced ST-segment depression without typical angina pectoris is related to increases in sympatho-adrenal activity or beta-adrenoceptor sensitivity. PATIENTS: Thirteen patients (four men) aged 35-62 years with ST-segment depression during exercise but atypical symptoms and normal myocardial scintigraphy, and 13 matched controls. DESIGN AND INTERVENTIONS: Patients and controls were compared regarding responses with: (i) exercise testing without treatment, (ii) exercise testing following beta-adrenoceptor blockade by propranolol (0.15 mg kg(-1) i.v.), (iii) incremental adrenaline infusions (0.1, 0.2, 0.4 and 0.8 nmol kg(-1) min(-1)) and (iv) adrenaline infusions during alpha-adrenoceptor blockade by phentolamine (0.5 mg min(-1)). MAIN OUTCOME MEASURES: ST-segment depression and tissue Doppler parameters reflecting contractility. RESULTS: Exercise lowered the ST-segment by 2.44 mm without and 0.87 mm with beta-adrenoceptor blockade (P < 0.001 for difference) amongst patients, but not amongst controls. Maximal heart rate was slightly higher amongst patients (P < 0.05), despite similar loads and plasma catecholamine responses to exercise in the two groups; this difference disappeared after beta-adrenoceptor blockade with propranolol. ST-segment depression during adrenaline infusion was greater in patients compared with controls (P < 0.01) despite similar increases in heart rate. alpha-Blockade enhanced the ST-segment depression (P < 0.001) and heart rate (P < 0.001) responses to adrenaline infusion more markedly amongst patients. Tissue Doppler imaging showed similar contractility and diastolic relaxation responses of patients and controls to adrenaline, but early diastolic movements did not increase amongst patients after phentolamine (P < 0.01). CONCLUSIONS: Exercise-induced ST-segment depression in patients with a low likelihood of ischaemic heart disease is related to increased beta-adrenergic sensitivity regarding chronotropic and electrophysiological, but not inotropic responses.

Prognostic implications of renal dysfunction in patients with stable angina pectoris.

OBJECTIVE: Impaired renal function is emerging as an independent risk factor for cardiovascular (CV) disease. We analysed the prognostic implications of estimated renal function in patients with angina pectoris. DESIGN: Post hoc analysis of the Angina Prognosis Study In Stockholm (APSIS). The estimated creatinine clearance (eCrCl) was calculated according to the Cockcroft-Gault formula in 808 patients. Outcomes were compared for subgroups with CrCl > or =90, 60-89 and<60 mL min(-1). Setting. Hospital-based study with patients referred from primary care and hospital. SUBJECTS: A total of 809 patients (248 women) with clinically diagnosed stable angina pectoris. Intervention. Double-blind treatment with metoprolol or verapamil. RESULTS: One hundred and sixty-four patients (91 women) had an eCrCl below 60 mL min(-1). During a median follow-up of 40 months, 38 patients suffered CV death and 31 patients had a nonfatal myocardial infarction (MI). In a univariate analysis a lower eCrCl was related to a higher risk for CV death or MI amongst men (log rank P = 0.036). A multivariate Cox analysis showed an independent prognostic importance of eCrCl for CV death (P = 0.046) and for CV death or MI (P = 0.042) amongst all patients. When analysed as a continuous variable, a 1 mL min(-1) decrease in eCrCl was associated with a 1.6% (0.1-3.1) increase in the risk for CV death or MI, and a 2.1% (0-4.1) increase in the risk for CV death alone. CONCLUSION: Renal dysfunction was found to be common in patients with stable angina pectoris and estimated creatinine clearances carried significant independent prognostic information regarding CV death and nonfatal MI.

Platelet-lymphocyte conjugation differs between lymphocyte subpopulations.

BACKGROUND: Platelets can bind to, and thereby influence, lymphocyte function. OBJECTIVE: The propensities of different lymphocyte subpopulations to form platelet-lymphocyte conjugates/aggregates (P-Lym) was investigated using four-color whole blood flow cytometry. RESULTS: P-Lym constituted approximately 3% of circulating lymphocytes. Platelet conjugation was most common among large (monocyte-sized) lymphocytes. Platelet activation by ADP slightly increased platelet-T-cell conjugation, mainly to T-cytolytic (Tc) cells, but markedly elevated platelet-natural killer (NK)-cell conjugation. T-cell activation by phytohemagglutinin increased heterotypic conjugation among both T-helper (TH) and Tc cells, whilst NK-cell activation by interleukin-2 affected platelet-NK-cell aggregation little. Neither platelet activation nor lipopolysaccharides-induced B-cell activation enhanced platelet-B-cell aggregation. Activation-dependent heterotypic conjugation was mainly found among large cells, with increased percentages of conjugated cells and more platelets bound per lymphocyte. P-Lym formation initiated by platelet activation was abolished by P-selectin blockade, and tended to be reduced by inhibition of GPIIb/IIIa, CD11b, or CD40L. P-Lym formation initiated by lymphocyte activation was partially inhibited by each of these blocking agents, but more markedly inhibited when the blocking agents were combined. CONCLUSIONS: Platelets selectively bind to larger and activated lymphocytes. T-lymphocyte activation enhances platelet-T-cell aggregation. Platelet activation enhances platelet-Tc aggregation slightly and platelet-NK-cell aggregation markedly, while cellular activation affects platelet-B-cell aggregation little. P-selectin ligation is essential, but GPIIb/IIIa, CD40L, and CD11b also contribute to the heterotypic conjugation.

Meal-induced platelet activation in Type 2 diabetes mellitus: effects of treatment with repaglinide and glibenclamide.

AIMS: To compare the effects of treatment with repaglinide and glibenclamide on platelet function and endothelial markers in patients with Type 2 diabetes mellitus, before and after a standardized meal. METHODS: Fifteen patients with Type 2 diabetes were investigated on three occasions: at baseline without oral hypoglycaemic drug treatment, and after 6 weeks' treatment with repaglinide or glibenclamide, respectively, in an open randomized cross-over study. Agonist-induced platelet P-selectin expression and platelet aggregation, urinary thromboxane, soluble P-selectin, von Willebrand factor (VWF), soluble E-selectin, intercellular adhesion molecule (ICAM-1) and C-reactive protein (CRP) were measured. In addition, pre-meal data were compared with non-diabetic control subjects (n = 15), matched for sex, age and BMI. RESULTS: Adenosine diphosphate (ADP)-induced platelet P-selectin expression increased post-meal in Type 2 diabetic patients both at baseline and after treatment with repaglinide and glibenclamide (P < 0.01 for all; repeated measures anova). Repaglinide treatment reduced fasting ADP-induced P-selectin expression compared with baseline (P = 0.01), but did not influence meal-induced platelet hyper-reactivity (P = 0.32). No significant anti-platelet effects of glibenclamide treatment were found. Plasma concentrations of VWF and ICAM-1 were elevated in patients with Type 2 diabetes compared with control subjects (P < 0.05 for both) and were reduced during treatment with repaglinide (P < 0.01 for both) but did not change during glibenclamide treatment. CONCLUSIONS: The post-meal state is associated with enhanced platelet reactivity in patients with Type 2 diabetes mellitus. Pre-meal treatment with repaglinide or glibenclamide does not inhibit postprandial platelet activation, but repaglinide treatment is associated with attenuated platelet and endothelial activity in the fasting state.

Favourable long term prognosis in stable angina pectoris: an extended follow up of the angina prognosis study in Stockholm (APSIS).

OBJECTIVE: To evaluate the long term prognosis of patients with stable angina pectoris. DESIGN: Registry based follow up (median 9.1 years) of patients participating in the APSIS (angina prognosis study in Stockholm), which was a double blind, single centre trial of antianginal drug treatment. PATIENTS: 809 patients (31% women) with stable angina pectoris < 70 (mean (SD) 59 (7) years at inclusion) and an age and sex matched reference population from the same catchment area. INTERVENTIONS: Double blind treatment with metoprolol or verapamil during 3.4 years (median), followed by referral for usual care with open treatment. MAIN OUTCOME MEASURES: Cardiovascular (CV) death and non-fatal myocardial infarction (MI) in the APSIS cohort and total mortality in comparison with reference subjects. RESULTS: 123 patients died (41 MI, 36 other CV causes) and 72 had non-fatal MI. Mortality (19% v 6%, p < 0.001) and fatal MI (6.6% v 1.6%, p < 0.001) were increased among male compared with female patients. Diabetes, previous MI, hypertension, and male sex independently predicted CV mortality (p < 0.001). Diabetes greatly increased the risk in a small subgroup of female patients. Male patients had higher mortality than men in the reference population during the first three years (cumulative absolute difference 3.8%) but apparently not thereafter. Female patients had similar mortality to women in the reference population throughout the 9.1 years of observation. CONCLUSIONS: Female patients with stable angina had similar mortality to matched female reference subjects but male patients had an increased risk. Diabetes, previous MI, hypertension, and male sex were strong risk factors for CV death or MI.

The impact of diabetes or elevated fasting blood glucose on cardiovascular prognosis in patients with stable angina pectoris.

AIMS: To examine the influences of diabetes and elevated fasting blood glucose on cardiovascular prognosis in patients with stable angina pectoris. METHODS: In a prospective study of 809 patients with stable angina pectoris randomized to receive metoprolol or verapamil, a subgroup of 69 diabetic patients was compared with non-diabetic patients with respect to the risk of cardiovascular (CV) death, non-fatal myocardial infarction (MI) and revascularization. We also analysed a subgroup of 67 patients with fasting blood glucose > or = 6.1 mmol/l, defined according to the most recent revised guidelines for the diagnosis of diabetes mellitus. Fasting blood glucose was measured in venous whole blood at baseline. RESULTS: The diabetic patients had a greater risk-factor burden, with a higher prevalence of hypertension, more likely to be male, a tendency towards a higher prevalence of previous MI, and higher triglyceride and lower high-density lipoprotein (HDL)-cholesterol levels. In multivariate analyses, diabetes was an independent risk factor for CV events with a relative risk of 2.64 (CI 1.39-5.00; P < 0.001) for CV death/MI, and 1.79 (CI 1.02-3.15; P < 0.01) for revascularization. Blood glucose > or = 6.1 mmol/l without a diagnosis of diabetes mellitus was found in 67 patients, and predicted CV death/MI [relative risk 2.76 (CI 1.97-3.84)] in both univariate and multivariate analyses. The prognosis of diabetic or hyperglycaemic patients did not differ significantly with metoprolol compared with verapamil treatment. CONCLUSIONS: Diabetes mellitus is an independent risk factor for CV death/MI and for revascularization in patients with stable angina pectoris. Elevated fasting blood glucose was seen in 9% of patients without known diabetes and was an equally strong and independent risk factor for CV death/MI as diagnosed and treated diabetes.

Prothrombotic responses to exercise are little influenced by clopidogrel treatment.

AIMS: Adenosine diphosphate (ADP) is involved in shear-induced platelet activation, which may be important for platelet responses to stress. We therefore tested the hypothesis that ADP receptor antagonism by clopidogrel treatment would attenuate exercise-induced platelet activation. METHODS AND RESULTS: Fifteen healthy volunteers performed exhaustive exercise without and with clopidogrel pretreatment (75 mg/day; 7 days) in a randomised crossover study. Filtragometry readings (reflecting platelet aggregability in vivo) and 11-dehydro-thromboxane B(2) (TxM) in plasma were determined before and after exercise. Platelet and leukocyte activity, platelet-platelet (PPA), and platelet-leukocyte aggregates (PLAs) in vivo and their responsiveness to agonist stimulation in vitro were assessed by flow cytometry. Clopidogrel treatment inhibited ADP-induced platelet P-selectin expression by 72% (54-85%). Exercise increased platelet aggregation (filtragometry and PPAs), elevated plasma TxM, increased single platelet P-selectin expression, elevated circulating PLAs, and enhanced ADP and thrombin-stimulated P-selectin expression. Clopidogrel prolonged filtragometry readings and attenuated agonist stimulated P-selectin expression at rest, but did not influence TxM in plasma or urine or attenuate platelet or leukocyte responses to exercise. Clopidogrel treatment did not influence plasma CD40L (ligand) at rest or after exercise. CONCLUSION: Clopidogrel treatment attenuates platelet activity in vivo at rest, but exercise counteracts the platelet stabilizing effects of clopidogrel. The hypothesis that ADP is involved in stress-induced platelet activation was not supported.

Determination of perhexiline and hydroxyperhexiline in plasma by liquid chromatography-mass spectrometry.

A method for the quantitative determination of perhexiline and its main hydroxylated metabolites in human plasma, based on liquid chromatography-mass spectrometry (LC-MS), was developed. The method used protein precipitation with acetonitrile followed by dilution with water and subsequent direct injection of the extract into the LC-MS system. Hexadiline was used as internal standard and the intra-assay coefficients of variation were

Exercise-induced platelet and leucocyte activation is not enhanced in well-controlled Type 1 diabetes, despite increased activity at rest.

AIMS/HYPOTHESIS: Stress can evoke a prothrombotic state with activated platelets and leucocytes, and increased platelet activation at rest has been reported for diabetic subjects. Thus, prothrombotic responses to stress may be enhanced in diabetes mellitus. We therefore evaluated platelet and leucocyte responses to exercise in Type 1 diabetic patients. METHODS: Type 1 diabetes mellitus patients with good metabolic control and healthy subjects matched for age and body mass index ( n=15 for both) performed a maximal exercise test. Platelet and leucocyte activation and their heterotypic aggregation were monitored by whole blood flow cytometry. RESULTS: Diabetic platelets did not show higher basal levels of P-selectin expression, but were more reactive to ADP and thrombin stimulation. Diabetic patients had increased lymphocyte and monocyte CD11b expression, and increased circulating platelet-monocyte aggregates. Exercise evoked thrombocytosis, increased circulating platelet P-selectin expression, enhanced platelet sensitivity to ADP and thrombin, and elevated plasma levels of soluble P-selectin to a similar degree in diabetic patients and healthy subjects. Exercise induced marked leucocytosis and elevated plasma elastase, but only slightly increased leucocyte CD11b expression and leucocyte reactivity to stimulation by N-formyl-methionyl-leucyl-phenylalanine. In all of these there was no difference between diabetic patients and healthy subjects. The numbers, but not percentages of circulating platelet-leucocyte aggregates were markedly increased by exercise, but the increase was less prominent among diabetic patients. CONCLUSIONS/INTERPRETATION: Strenuous exercise evokes platelet and leucocyte activation in Type 1 diabetic patients and healthy subjects. Platelet and monocyte hyperactivity were found at rest, but responses to stress were not augmented in metabolically well-controlled Type 1 diabetes mellitus patients.

Enhanced P-selectin expression and increased soluble CD40 Ligand in patients with Type 1 diabetes mellitus and microangiopathy: evidence for platelet hyperactivity and chronic inflammation.

AIMS/HYPOTHESIS: Platelet activation, endothelial dysfunction and inflammation may be involved in early stages of diabetic microangiopathy. We therefore investigated patients with Type 1 diabetes mellitus, without ( n=19) and with ( n=20) microangiopathy, matched for glycaemic control and duration of disease, and matched with healthy control subjects ( n=27). METHODS: Platelet activation was measured as platelet P-selectin expression using whole blood flow cytometry and as soluble P-selectin by immunoassay. Von Willebrand factor antigen in plasma, serum soluble E-selectin, CD40 ligand (sCD40L) and C-reactive protein (CRP) served as markers for endothelial function and inflammation. RESULTS: Thrombin-induced platelet P-selectin expression was enhanced, and soluble P-selectin and sCD40L concentrations were increased in patients with microangiopathy compared with the control subjects ( p<0.01 for both) and with patients without microangiopathy ( p<0.05 for P-selectin expression and sP-selectin), whereas all three parameters were similar in patients without microangiopathy and in the control subjects. CRP and soluble E-selectin were increased in patients with microangiopathy, compared with the control subjects ( p<0.01 and p<0.05), whereas von Willebrand factor did not differ between the groups. CONCLUSIONS/INTERPRETATION: Microangiopathy in Type 1 diabetes is associated with platelet hyperactivity, endothelial dysfunction and low-grade inflammation, indicating an increased risk for cardiovascular disease.

Enhanced leukocyte-platelet cross-talk in Type 1 diabetes mellitus: relationship to microangiopathy.

BACKGROUND: Platelets and leukocytes may influence each others' function, i.e. platelet-leukocyte cross-talk. Diabetes mellitus (DM) is associated with platelet and leukocyte dysfunction. OBJECTIVE: To evaluate platelet-leukocyte cross-talk, and if this might contribute to platelet and leukocyte dysfunction and microangiopathy in DM patients. PATIENTS AND METHODS: We evaluated platelet and leukocyte function, and cross-talk between these cells in Type 1 DM patients without (n = 19) and with (n = 20) microangiopathy, and healthy subjects (n = 27), using whole blood flow cytometry. Platelet-leukocyte cross-talk was studied in hirudinized whole blood incubated at 37 degrees C with stirring. RESULTS: Basal single platelet P-selectin and leukocyte CD11b expression were similar in DM patients and healthy subjects, whilst circulating platelet-leukocyte aggregates and plasma elastase levels were elevated in DM patients. The thromboxane A2 analog U46619 (3 x 10(-7) m) induced more marked increases of platelet P-selectin expression and platelet-leukocyte aggregation in DM patients than in healthy subjects. The leukocyte-specific agonist N-formyl-methionyl-leucyl-phenylalanine (fMLP) (10(-7) m) induced more marked CD11b expression in DM patients with microangiopathy, compared with healthy subjects. Platelet-leukocyte cross-talk induced by U46619 (10(-6) m) showed no difference between DM patients and healthy subjects. fMLP (10(-6) m) evoked marked leukocyte activation, which subsequently caused mild platelet P-selectin expression. This leukocyte-platelet cross-talk was more pronounced in DM patients than in healthy subjects. Furthermore, enhanced leukocyte-platelet cross-talk was correlated to platelet hyperreactivity among DM patients with microangiopathy only. CONCLUSIONS: Type 1 DM is associated with platelet and leukocyte hyperactivity, and enhanced leukocyte-platelet cross-talk, which may contribute to platelet hyperactivity and the microvascular complications seen in Type 1 DM.

Biphasic pro-thrombotic and inflammatory responses after coronary artery bypass surgery.

Early graft failure after coronary artery bypass grafting (CABG) is related to thrombosis and inflammation in the grafted vessel(s). The time courses of, and relationships between, pro-thrombotic and inflammatory responses to CABG surgery have, however, not been well defined. Fifteen patients undergoing CABG were examined before, and 1 h, 1 day, 7 days, and 3 months after surgery. Cellular markers of platelet and leukocyte activation were monitored by whole blood flow cytometry, and plasma markers of pro-thrombotic and inflammatory responses were analyzed by immunoassays. CABG immediately increased circulating P-selectin-positive platelets, leukocyte CD11b expression, and platelet-leukocyte aggregates (PLAs). Thrombin generation (F1 + 2 levels) and cytokine release [tumor necrosis factor-alpha (TNF-alpha), interleukin (IL)-8, and IL-10], soluble P-selectin, and soluble E-selectin also increased immediately. These alterations persisted during the first week after surgery, with re-bound increases of circulating activated platelets and PLAs, TNF-alpha, and F1 + 2 on day 7. Platelet and PLA responsiveness to in vitro stimulation was suppressed immediately after CABG, but markedly enhanced 1 week after surgery. After 3 months, plasma soluble P-selectin, F1 + 2, and IL-10, and monocyte CD11b expression were still slightly elevated compared with baseline. In conclusion, CABG induces marked pro-thrombotic and inflammatory responses, which persist for at least 1 week. Platelet activation, platelet reactivity, PLA formation, thrombin generation, and TNF-alpha release show a second peak 1 week after surgery. These findings suggest that intensified and prolonged antithrombotic/inflammatory treatment should be considered after CABG surgery.

Prognostic implications of autonomic function assessed by analyses of catecholamines and heart rate variability in stable angina pectoris.

OBJECTIVE: To assess the prognostic impact of autonomic activity, as reflected by catecholamines and heart rate variability (HRV), in patients with stable angina pectoris. DESIGN: Double blind, randomised treatment with metoprolol or verapamil. 24 hour ambulatory ECG, used for frequency domain analyses of HRV, and symptom limited exercise tests at baseline and after one month of treatment. Catecholamine concentrations were measured in plasma (rest and exercise) and urine. SETTING: Single centre at a university hospital. PATIENTS: 641 patients (449 men) with stable angina pectoris. MAIN OUTCOME MEASURES: Cardiovascular (CV) death, non-fatal myocardial infarction (MI). RESULTS: During follow up (median 40 months) there were 27 CV deaths and 26 MIs. Patients who died of CV causes had lower total power and high (HF), low (LF), and very low (VLF) frequency components of HRV. HRV was not altered in patients who suffered non-fatal MI. Catecholamines did not differ between patients with and those without events. Metoprolol increased HRV. Verapamil decreased noradrenaline (norepinephrine) excretion. Multivariate Cox analyses showed that total power, HF, LF, and VLF independently predicted CV death (also non-sudden death) but not MI. LF:HF ratios and catecholamines were not related to prognosis. Treatment effects on HRV did not influence prognosis. CONCLUSIONS: Low HRV predicted CV death but not non-fatal MI. Neither the LF:HF ratio nor catecholamines carried any prognostic information. Metoprolol and verapamil influenced LF, HF, and catecholamines differently but treatment effects were not related to prognosis.

Insulin enhances platelet activation in vitro.

Diabetes mellitus is associated with an increased risk of atherothrombotic complications. There is accumulating evidence of platelet hyperreactivity in diabetes, which may be of importance in the pathogenesis of diabetic vascular complications. Platelets possess insulin receptors, but their physiological relevance is not clear, and data on insulin effects on platelet function in the literature are less than consistent. We therefore investigated the influence of insulin on platelet activation in vitro. Fasting blood samples were collected in 20 healthy males, using citrate or hirudin as anticoagulants. Platelet activation was measured as platelet P-selectin expression and fibrinogen binding using whole blood flow cytometry in unstimulated and adenosine diphosphate (ADP) stimulated samples, incubated with 0-10000 microU/ml insulin for 20 min. The effect of insulin (30 or 300 microU/ml, incubated for 3 min) on platelet aggregation was studied using Born aggregometry in platelet-rich plasma (PRP). Insulin enhanced platelet fibrinogen binding more than P-selectin expression in unstimulated and ADP stimulated samples (P<.001 by analysis of variance [ANOVA]; n=20). Insulin (30 or 300 microU/ml) also enhanced ADP-induced platelet aggregation in PRP (P<.01 or P<.001; n=14). The platelet activating effect of insulin was verified in hirudinized samples (n=12), indicating that it was not dependent on unphysiologically low extracellular calcium concentrations. Thus, insulin enhances platelet activation in vitro, independently of extracellular calcium concentrations. Beneficial effects of insulin treatment on platelet function in vivo are probably related to improved metabolic control, rather than to direct platelet stabilizing effects.

Feedback on prescribing rate combined with problem-oriented pharmacotherapy education as a model to improve prescribing behaviour among general practitioners.

OBJECTIVE: To develop a working model with which prescribing behaviour among general practitioners might be influenced. DESIGN: Intervention based on feedback on prescribing rates and problem-oriented educational outreach visits, using educational material and local opinion leaders. Randomised study with three parallel intervention groups of general practitioners, which also served as controls for each other. The pharmacotherapeutic fields chosen were hypertension, peptic ulcer/dyspepsia and depression. Prescription data were retrieved from the electronic patient records for periods of 1 year before and after the intervention. SETTING: Six health care centres and three continuing medical education groups in Stockholm. SUBJECTS: Forty general practitioners. MAIN OUTCOME MEASURES: Drug prescribing rates and patterns before and after the intervention. RESULTS: In the hypertension field, desired trends in fractional prescribing (favouring diuretics and beta blocking agents) were recorded, with a significant (P < 0.05) effect on prescriptions for agents acting on the renin-angiotensin system, despite a pre-existing prescribing behaviour already much in line with the goals. In the peptic ulcer/dyspepsia field, desired trends were recorded for both types of therapies addressed. The fractional prescribing rates for proton-pump inhibitors decreased from 61.0% to 52.6% in the intervention arm and increased from 68.1% to 76.0% in the control arm (not significant due to low power). The depression group focused on better general attention to the disease and only minor changes were registered. CONCLUSION: Feedback of individual prescribing rates, combined with problem-oriented educational outreach visits, is a promising model for the improvement of prescribing behaviour. Data from the electronic patient record were feasible for feedback on prescribing rates.