Wioleta Stolarek

Diurnal variation in platelet inhibition by clopidogrel

Morning increase in the occurrence of myocardial infarction, stroke and sudden cardiac death is a well-recognized phenomenon, which is in line with a morning enhancement of platelet aggregation. We investigated whether platelet inhibition during clopidogrel and aspirin therapy varies during the day. Fifty-nine consecutive patients (45 men and 14 women) with first ST-segment elevation myocardial infarction (STEMI) treated with primary percutaneous coronary interventions (pPCI) on dual antiplatelet therapy were prospectively enrolled into the study. Blood samples were collected 4 days after start of clopidogrel treatment at 6.00 a.m., 10.00 a.m., 2.00 p.m. and 7.00 p.m. Arachidonic acid and adenosine diphosphate (ADP)-induced platelet aggregation were assessed by impedance aggregometry. Platelet inhibition by clopidogrel was lowest in the midmorning: median ADP-induced platelet aggregation was 55%, 17% and 27% higher at 10.00 a.m. compared to 6.00 a.m., 2.00 p.m. and 7.00 p.m., respectively (p < 0.002). Nonresponsiveness to clopidogrel defined according to the device manufacturer was 2.4-fold more frequent in the midmorning than in the early morning. We observed a more pronounced midmorning increase in ADP-induced platelet aggregation in diabetic patients when compared to non-diabetics. In contrast, no diurnal variation in the antiplatelet effect of aspirin was observed. In conclusion, in patients presenting with STEMI undergoing pPCI, platelet inhibition by clopidogrel is less strong in the midmorning hours. This periodicity in platelet aggregation in patients on dual antiplatelet therapy should be taken into consideration when assessing platelet function in clinical studies.

Prasugrel overcomes high on-clopidogrel platelet reactivity in the acute phase of acute coronary syndrome and maintains its antiplatelet potency at 30-day follow-up

BACKGROUND The aim of this study was to assess antiplatelet effect of prasugrel in acute coronary syndrome (ACS) patients with high on-treatment platelet reactivity (HTPR) on clopidogrel, undergoing percutaneous coronary intervention (PCI). METHODS A prospective, platelet reactivity-guided, parallel-group, open-label study including 71 patients pretreated with clopidogrel 600 mg and assigned either to prasugrel (30 mg loading dose, 10 mg maintenance dose; n = 46) or clopidogrel (150 mg maintenance dose for 6 days and thereafter 75 mg maintenance dose; n = 25) regimen, based on vasodilator-stimulated phosphoprotein (VASP)-assessed platelet reactivity index (PRI; > 50% vs. ≤ 50%) measured next morning post-PCI. RESULTS Median PRI value after switch to prasugrel sharply declined at 24 h (70.0 [61.3-75.6] vs. 11.9 [6.8-25.7]%; p < 0.000001) and slightly but significantly rose between 24 h and 30 days (27.9 [15.5-46.8]%; p < 0.0006). In contrast, median PRI values in the clopidogrel group were similar at baseline and at 24 h (25.1 [13.7-40.2] vs. 22.0 [18.4-36.8]%; p = NS) and then modestly rose at 30 days (30.3 [20.4-45.7]%; p < 0.03). The prevalence of HTPR decreased in the prasugrel group between baseline and 24 h measurements (100.0 vs. 4.3%; p < 0.0001). Rates of patients with HTPR at 24 h and 30 days were similar in both groups, so were the tendencies in patterns of platelet inhibition evaluated with multiple electrode aggregometry as compared with the VASP assay. CONCLUSIONS Our study indicates that prasugrel overcomes HTPR on clopidogrel in the acute phase of interventionally treated ACS and maintains its antiplatelet potency in 30-day follow-up. Potential clinical benefits of personalized antiplatelet prasugrel-based therapy warrant further investigation in clinical ACS trials.

The Adherence Scale in Chronic Diseases (ASCD). The power of knowledge: the key to successful patient — health care provider cooperation

Introduction. Autotransfusions of ozonised blood or infusions of gaseous ozone into blood vessels andbody cavities are believed to exert therapeutic effects in some pathological states. Investigations on thereaction of ozone with biological molecules and membrane structures are a subject of crucial importance. The present study aimed to yield more precise data about the alterations, which occur in different erythrocytemembrane regions subjected to medical ozone. This could provide some additional informationabout the structural changes in the membrane at a molecular level. Material and methods. Blood was obtained from 22 healthy volunteers (aged 21 to 63) by vein puncture andmixed with 1/10 volume of 0.13 M trisodium citrate. Erythrocytes were isolated from fresh blood by centrifugationat 4°C, at 1,500 × g and purified by three cycles of resuspension and washing with PBS. Ozone was generatedby passing pure gaseous oxygen at 30 l/h through an apparatus producing silent electric discharges. EPRspectra were obtained at X-band (9.4 GHz), at modulation frequency of 100 kHz. The scan time was 4 min, and the time constant 0.3 s. Since biological membranes are heterogeneous systems composed of severalcoexisting domains, EPR spectra are superimpositions of several spectra with different fluidity parameters. Results. The effects of ozone at two concentrations (10 and 45 g/m3) on fluidity and phospholipid domainstructure of erythrocyte membranes were investigated by electron paramagnetic resonance (EPR). Atincreased ozone concentration (45 g/m3), the portion of the least ordered domains (WLO) increased, witha corresponding decrease of ordered (WMO, WO), more rigid regions. The order of lipid acyl chains of twoordered (MO and O) as well as the least ordered (LO) domains diminished, as expressed by smaller orderparameters. For ozone concentration of 10 g/m3 values of order parameter were slightly increased, whichindicates a tendency to rigidisation of lipid bilayer at this ozone concentration. This change was, however,statistically insignificant. There were no statistically significant differences in the thermotropic behaviour ofweight factor of ordered domains (WMO, WO) between ozonised and control red cells. Conclusion. The obtained data shows that ozonation of erythrocytes results in cell membrane fluidisationand an increase in red cell deformability. On the other hand, these results could suggest that ozonationof erythrocytes leads to structural changes in the membranes, especially in cytoskeletal proteins, but thiseffect is probably dose-dependent.

Acetylsalicylic acid resistance risk factors in patients with myocardial infarction

BACKGROUND Despite its commonly recognized benefits in the cardiovascular disease setting, an issue of resistance to this drug has lately emerged. The aim of this research was assessment of the phenomenon of acetylsalicylic acid (ASA) resistance and its risk factors in patients treated for myocardial infarction. METHODS This study is a post-hoc analysis of a previous prospective study with approximately 200 patients treated for myocardial infarction with a coated formulation of ASA. The population was divided into two subgroups according to the response to ASA. ASA responsiveness was assessed using the arachidonic acid-dependent platelet aggregation (ASPI-test). The measurements were performed using the technique of impedance aggregometry. RESULTS The prevalence of aspirin resistance among the study population was 6.2%. All analyzed aggregometric parameters (including ASPI-test, adenosine diphosphate dependent platelet aggregation - ADP-test, bleeding time measurement) showed significant differences between both subgroups. ASA resistant patients had higher concentrations of brain natriuretic peptide (BNP), high-sensitivity C-reactive protein (hs-CRP), leukocytes (WBC) and platelets (PLT) but lower concentrations of hemoglobin (HGB). The temporal point analysis for both subgroups showed aspirin resistance incidence peak in patients at 9 months after myocardial infarction. CONCLUSIONS The prevalence of aspirin resistance in our study population is comparable with rates reported in literature among patients with cardiovascular diseases. There is a possible relation between aspirin resistance and clopidogrel resistance. Presence did not affect the incidence of the clinical end-points.

Effect of reperfusion on vascular smooth muscle reactivity in three contraction models

BACKGROUND Ischemia and reperfusion remain inseparable elements of numerous medical procedures such as by-pass surgery, organ transplantation or other cardiology and intervention radiology. The contraction of the smooth muscle of the vessel is considered to be one of the basic components leading to impaired perfusion, an increase in the oxygen deficit of the endothelium of the vessel, and subsequently also to tissues vascularized by the vessel. Main aim of this study was to evaluate the effect of ischemia and reperfusion on vascular smooth muscle cells stimulated pharmacologically with mastoparan-7 (direct G-protein activator) in comparison to stimulation of G-protein coupled receptor agonist - phenylephrine, and direct calcium channel activator - Bay K8644. MATERIAL AND METHODS Experiments were performed on isolated and perfused tail artery of Wistar rats. Contraction force in our model was measured by increased level of perfusion pressure with a constant flow. RESULTS Concentration-response curves obtained for phenylephrine, mastoparan-7 and Bay K8644 presented a sigmoidal relation. Ischemia induced hyporreactivity of vessels, whereas during reperfusion the significant time related hyperreactivity for phenylephrine and mastoparan-7 only but not for Bay K8644. These reactions were secondary to the modulation of calcium influx from intra- and extracellular calcium stores. CONCLUSIONS Results of our experiments suggest that mastoparan-7 significantly induces contraction of vascular smooth muscle cells not only for controls but in the presence of ischemia and reperfusion too. Potential therapeutic applications of the observed reactions are important. They may include regenerative processes within the nervous system, studies on the improvement of blood flow within the microcirculation, or antimicrobial activity. Modulation of the G protein-phospholipase C response may also be an interesting point of action of future drugs modifying the response to stimulation during ischemia in particular, such activities could take place during the transport of organs for transplantation.

Therapeutic drug monitoring of digoxin–20 years of experience

BACKGROUND Digoxin is the oldest drug used in the pharmacotherapy of heart failure (HF). However, digoxin remains an important therapeutic option for patients with persistent symptoms of HF occurring despite the implementation of standard pharmacotherapy. Digoxin concentration serum (SCD) should equal 1-2ng/ml. The aim of our study was to measure of SCD among the hospitalized patients as well as to determine the selected factors influencing the concentration of the digoxin in the blood. METHODS The presented research was based on a retrospective analysis including 2149 patients treated with digoxin and hospitalized between 1980 and 2000. Was used for the determination of SCD automatic analyzer TDX ABBOTT GmbH - fluorescence polarization immunoassay (FPIA), with therapeutic range for digoxin of 0.8-2.0ng/ml. RESULTS Average SCD result in the study population was located within the therapeutic range and amounted 1.06ng/ml (55.7% of patients). Statistically significant differences in digoxin level were observed depending on the way of medicine administration (p=0.000001) and the daily amount (p=0.001). Moreover, statistically significant differences in digoxin level were observed depending on sex (p=0.00002). CONCLUSIONS An elevated level of digoxin was observed in the case of patients who received the medication both orally and intravenously, together with an increase in the daily amount of digoxin doses. It was confirmed that an elevated digoxin level occurs in the course of treatment in the case of women.

Impact of prior statin therapy on evaluation of the inflammatory process and cortisol concentration in patients with the first ST-segment elevation myocardial infarction undergoing coronary angioplasty with bare metal stent implantation

Introduction. The aim of the current study was to verify the impact of statin therapy on evaluation of the inflammatory process and cortisol concentration in patients with the first episode of ST-segment elevation myocardial infarction undergoing coronary angioplasty with bare metal stent implantation. Material and methods. The study was designed as a prospective, single-center cohort study, with a total number of 200 patients enrolled between 2005 and 2008. Results. Seventeen patients with ongoing statin therapy and 167 patients without those agents underwent pPCI with BMS implantation. The cortisol concentration on admission was significantly lower in statin therapy subgroup — median 14.9 μg/dL (9.5–23.3 IQR) vs. 28,1 μg/dL (17.2–39.9 IQR) for patients without lipid lowering drug, p = 0.01. The level of cortisol after 23h was also significantly lower in statin receiving subgroup: 10.4 μg/dL (8.3–19 IQR) vs. 17.3 μg/dL (10.1–25.9 IQR) adequately, p = 0.021. Those two groups did not differ significantly in relation to CRP, IL-6, IL-10 concentrations and to anti-inflammatory cytokine ratio [IL-6/IL-10] on admission, after 24h and at discharge. Significant differences were observed in the concentrations of cTnI and activities of CK and CK-MB. Conclusions. Ongoing statin therapy before an episode of myocardial infarction has an influence on cortisol concentration and cardiac markers. No significant effect on serum levels of cytokines has been observed.