Gerinnungshemmende Therapie des akuten Koronarsyndroms

Das akute Koronarsyndrom ist eine der häufigsten kardialen Erkrankungen. Seine Behandlung stützt sich im Wesentlichen auf Koronarintervention und gerinnungshemmende Therapie. Die thrombozytenaggregationshemmende Therapie besteht zurzeit aus Azetylsalizylsäure und Clopidogrel und ggf. periinterventioneller Glykoprotein-IIb/ IIIa-Blockade. Mit Prasugrel steht ein neuer thrombozytenaggregationshemmender Wirkstoff kurz vor der Einführung in die Klinik.

Bei der antithrombotischen Therapie geht die Entwicklung zu Pharmaka mit Anti-Faktor-Xa-Aktivität (z. B. Fondaparinux) oder direkter Antithrombinwirkung (z. B Bivalirudin). In diesem Übersichtsartikel werden die Entwicklungen der vergangenen Monate auf dem Gebiet der gerinnungshemmenden Therapie des akuten Koronarsyndroms diskutiert.

[Anticoagulation in acute coronary syndrome. An update]

The acute coronary syndrome (ACS) is one of the most frequent diagnoses in cardiology. The therapeutic corner-stones of ACS are PCI (percutaneous coronary intervention) and inhibition of blood coagulation. Current antiplatelet therapy consists of aspirin in combination with clopidogrel and glycoprotein IIb/IIIa blockade if needed. Prasugel is a new antiplatelet agent that is in the process of being approved for routine clinical use. In terms of antithrombotic therapy latest developments focus on drugs with anti-factor Xa activity, such as fondaparinux, or direct anti-thrombin activity, such as bivalirudin. This review discusses latest developments in the field of anti-platelet and anti-thrombotic therapy for ACS.

Die Bedeutung von Mikropartikeln bei vaskulären Erkrankungen

Mikropartikel (MP) sind kleine Zellvesikel, die von Zellen im Rahmen von Aktivierung oder Apoptose freigesetzt werden und im Blut nachweisbar sind. MP bestehen aus Plasma und Zellmembran ihrer Ursprungszelle und können anhand ihrer Oberflächenantigene ihrer Ursprungszelle zugeordnet werden. Durch den Nachweis entsprechender MP kann somit eine Aussage über den Funktionszustand der Ursprungszelle (Aktivierung oder Apoptose) getroffen werden. Mittlerweile ist bekannt, dass MP als Vektoren spezifische biologische Informationen zwischen einzelnen Zellen austauschen können und somit ein wesentliches Bindeglied in der Pathophysiologie inflammatorischer und koagulatorischer Prozesse darstellen. Da viele Gefäßerkrankungen mit inflammatorischen und thrombotischen Prozessen einhergehen, sind MP nachweisbar und bekommen sowohl als Diagnostikum (Surrogatmarker) als auch als pathophysiologischer Baustein vaskulärer Erkrankungen zunehmende Bedeutung.

Die Rolle von Thrombin in der Blutgefäßentwicklung

Die Bildung des Blutgefäßsytems ist ein entscheidender Schritt in der Embryonalentwicklung. Blutgefäßsystem und Blut entwickeln sich in enger räumlicher Nachbarschaft. In dieser Übersichtsarbeit wird die Rolle des Blutgerinnungssystems, inbesondere von Thrombin, als Koordinator der Blutgefäßbildung diskutiert.

In Mausmodellen zeigt sich, dass der Verlust von Gerinnungsfaktoren zu verminderter Thrombinbildung führt und von einer gestörten kardiovaskulären Entwicklung begleitet ist. Ähnliche Phänotypen lassen sich in Tiermodellen beobachten, in denen die Bindung von Thrombin und seinen Zelloberflächenrezeptor PAR-1 oder die anschließende G-Protein-Signalkaskade gestört sind. Darüber hinaus wird deutlich, dass die Thrombinsignalübertragung in der Blutgefäßentwicklung nicht durch das klassische Modell der extrinsischen und intrinsischen Blutgerinnungskaskade erklärbar sind, sondern zahlreiche Quervernetzungen bestehen. Da embryonale und adulte Blutgefäßbildung ähnlichen Mechanismen folgen, ist es entscheidend diese zu verstehen, um neuartige vaskuläre Therapiestrategien entwickeln zu können.

[Is stent thrombosis the new Achilles heel of interventional cardiology? State of the Art clinical trials, causes and approaches for prevention]

Coronary stents are the mainstay of percutaneous coronary intervention. Stent thrombosis is a potentially catastrophic and often life-threatening complication. If it occurs it presents in up to 80% as myocardial infarction, about half of the affected patients die from this complication. The dual antiplatelet therapy has markedly reduced its occurrence. Today, stent thrombosis occurs in <1%, usually as a delayed event; but compared to bare metal stents the overall incidence has not increased in meta-analyses of randomized trials. The advent of drug-eluting stents (DES) has raised concerns regarding the occurrence of delayed stent thrombosis. Delayed arterial wall healing as well as prothrombotic characteristics of the drug eluting stent itself may contribute to stent thrombosis. In order to prevent stent thrombosis a standardized fixed dose antiplatelet therapy with ASA and clopidogrel is recommended. But, their efficacy depends on patient's individual characteristics such drug metabolism. Therefore, individual determination of platelet function in each patient undergoing stent implantation may help to avoid prothrombotic as well as bleeding complications.

Developmental fate of ovoid oocytes

BACKGROUND

Irregularities in composition, thickness and/or color of the zona pellucida may impair optimal function and result in reduced outcome. Anomalies of oocyte shape have not been investigated in detail in this respect.

METHODS

Therefore, all patients attending our clinic within a period of 1 year were screened for the presence of ovoid gametes and the corresponding developmental potential was evaluated. For all elongated gametes, a roundness index (RI; length divided by width) was calculated in order to quantify shape.

RESULTS

RI did not affect fertilizability (P > 0.05). The degree of dysmorphism was found to be related to cleavage pattern. The more ovoid a gamete was, the higher was the risk of the corresponding zygote not cleaving like a tetrahedron (P < 0.01). Abnormal cleavage (a rather flat array of blastomeres) was associated with delayed compaction (P < 0.01) and blastocyst formation (P < 0.001). The quality of blastocysts was not affected at any stage in ovoid concepti (P > 0.05).

CONCLUSIONS

Ovoid oocytes with abnormal cleavage pattern show delayed preimplantation development, probably due to a reduced number of cell-to-cell contacts.

Short-term effects of pulsed electromagnetic fields after physical exercise are dependent on autonomic tone before exposure

The therapeutic application of pulsed electromagnetic fields (PEMFs) can accelerate healing after bone fractures and also alleviate pain according to several studies. However, no objective criteria have been available to ensure appropriate magnetic field strength or type of electromagnetic field. Moreover, few studies so far have investigated the physical principles responsible for the impact of electromagnetic fields on the human body. Existing studies have shown that PEMFs influence cell activity, the autonomic nervous system and the blood flow. The aim of this study is to examine the instantaneous and short-term effects of a PEMF therapy and to measure the impact of different electromagnetic field strengths on a range of physiological parameters, especially the autonomic nervous systems, determined by heart rate variability (HRV) as well as their influence on subjects' general feeling of well-being. The study comprised experimental, double-blind laboratory tests during which 32 healthy male adults (age: 38.4+/-6.5 years) underwent four physical stress tests at standardised times followed by exposure to pulsed magnetic fields of varying intensity [HPM, High Performance magnetic field; Leotec; pulsed signal; mean intensity increase: zero (placebo), 0.005, 0.03 and 0.09 T/s]. Exposure to electromagnetic fields after standardised physical effort significantly affected the very low frequency power spectral components of HRV (VLF; an indicator for sympathetically controlled blood flow rhythms). Compared to placebo treatment, exposure to 0.005 T/s resulted in accelerated recovery after physical strain. Subjects with lower baseline VLF power recovered more quickly than subjects with higher VLF when exposed to higher magnetic field strengths. The application of electromagnetic fields had no effect on subjects' general feeling of well-being. Once the magnetic field exposure was stopped, the described effects quickly subsided. PEMF exposure has a short-term dosage-dependent impact on healthy subjects. Exposure to PEMF for 20 min resulted in more rapid recovery of heart rate variability, especially in the very low frequency range after physical strain. The study also showed the moderating influence of the subjects' constitutional VLF power on their response to PEMF treatment. These findings have since been replicated in a clinical study and should be taken into consideration when PEMF treatment is chosen.

Diffusion and perfusion-weighted magnetic resonance imaging techniques in stroke recovery

Most of the functional recovery after stroke takes place during the first three months after the insult. The neuronal mechanisms underlying this recovery are presently mostly unknown. However, in order to create efficient rehabilitation programs, it is of great importance to uncover these mechanisms. Multiple imaging techniques have been employed for the detection and characterization of ischemic lesions in the brain as well as monitoring of processes associated with stroke recovery. Diffusion and perfusion-weighted magnetic resonance imaging techniques are easy and fast to perform and provide significant information about the ischemic lesion and the hypoperfusion surrounding the lesion at both micro and macrovascular level. More sensitive detection and accurate characterization of the lesion will help in choosing the therapeutic strategies. Methods for monitoring brain function recovery will provide a better understanding of the basic mechanisms of plasticity in the brain, and will serve as a tool for the evaluation of therapeutic interventions, which may eventually include, for example, stem cell transplantation. With the help of these diagnostic tools it may become possible to tailor individual rehabilitation programs.

The 15-Country Collaborative Study of Cancer Risk among Radiation Workers in the Nuclear Industry: estimates of radiation-related cancer risks

A 15-Country collaborative cohort study was conducted to provide direct estimates of cancer risk following protracted low doses of ionizing radiation. Analyses included 407,391 nuclear industry workers monitored individually for external radiation and 5.2 million person-years of follow-up. A significant association was seen between radiation dose and all-cause mortality [excess relative risk (ERR) 0.42 per Sv, 90% CI 0.07, 0.79; 18,993 deaths]. This was mainly attributable to a dose-related increase in all cancer mortality (ERR/Sv 0.97, 90% CI 0.28, 1.77; 5233 deaths). Among 31 specific types of malignancies studied, a significant association was found for lung cancer (ERR/Sv 1.86, 90% CI 0.49, 3.63; 1457 deaths) and a borderline significant (P = 0.06) association for multiple myeloma (ERR/Sv 6.15, 90% CI <0, 20.6; 83 deaths) and ill-defined and secondary cancers (ERR/Sv 1.96, 90% CI -0.26, 5.90; 328 deaths). Stratification on duration of employment had a large effect on the ERR/Sv, reflecting a strong healthy worker survivor effect in these cohorts. This is the largest analytical epidemiological study of the effects of low-dose protracted exposures to ionizing radiation to date. Further studies will be important to better assess the role of tobacco and other occupational exposures in our risk estimates.

The 15-Country Collaborative Study of Cancer Risk Among Radiation Workers in the Nuclear Industry: design, epidemiological methods and descriptive results

Radiation protection standards are based mainly on risk estimates from studies of atomic bomb survivors in Japan. The validity of extrapolations from the relatively high-dose acute exposures in this population to the low-dose, protracted or fractionated environmental and occupational exposures of primary public health concern has long been the subject of controversy. A collaborative retrospective cohort study was conducted to provide direct estimates of cancer risk after low-dose protracted exposures. The study included nearly 600,000 workers employed in 154 facilities in 15 countries. This paper describes the design, methods and results of descriptive analyses of the study. The main analyses included 407,391 nuclear industry workers employed for at least 1 year in a participating facility who were monitored individually for external radiation exposure and whose doses resulted predominantly from exposure to higher-energy photon radiation. The total duration of follow-up was 5,192,710 person-years. There were 24,158 deaths from all causes, including 6,734 deaths from cancer. The total collective dose was 7,892 Sv. The overall average cumulative recorded dose was 19.4 mSv. A strong healthy worker effect was observed in most countries. This study provides the largest body of direct evidence to date on the effects of low-dose protracted exposures to external photon radiation.

The 15-Country Collaborative Study of Cancer Risk among Radiation Workers in the Nuclear Industry: Study of Errors in Dosimetry

To provide direct estimates of cancer risk after low-dose protracted exposure to ionizing radiation, a large-scale epidemiological study of nuclear industry workers was conducted in 15 countries. As part of this study, identification and quantification of errors in historical recorded doses was conducted based on a review of dosimetric practices and technologies in participating facilities. The main sources of errors on doses from "high-energy" photons (100-3000 keV) were identified as the response of dosimeters in workplace exposure conditions and historical calibration practices. Errors related to dosimetry technology and radiation fields were quantified to derive period- and facility-specific estimates of bias and uncertainties in recorded doses. This was based on (1) an evaluation of predominant workplace radiation from measurement studies and dosimetry expert assessment and (2) an estimation of the energy and geometry response of dosimeters used historically in study facilities. Coefficients were derived to convert recorded doses to H(p) (10) and organ dose, taking into account different aspects of the calibration procedures. A parametric, lognormal error structure model was developed to describe errors in doses as a function of facility and time period. Doses from other radiation types, particularly neutrons and radionuclide intake, could not be adequately reconstructed in the framework of the 15-Country Study. Workers with substantial doses from these radiation types were therefore identified and excluded from analyses. Doses from "lower-energy" photons (<100 keV) and from "higher-energy" photons (>3 MeV) were estimated to be small.

Radiation exposure to the population of Europe following the Chernobyl accident

On the occasion of the 20th anniversary of the Chernobyl accident an attempt has been made to evaluate the impact of the Chernobyl accident on the global burden of human cancer in Europe. This required the estimation of radiation doses in each of the 40 European countries. Dose estimation was based on the analysis and compilation of data either published in the scientific literature or provided by local experts. Considerable variability has been observed in exposure levels among the European populations. The average individual doses to the thyroid from the intake of (131)I for children aged 1 y were found to vary from approximately 0.01 mGy in Portugal up to 750 mGy in Gomel Oblast (Belarus). Thyroid doses to adults were consistently lower than the doses received by young children. The average individual effective doses from external exposure and ingestion of long-lived radiocaesium accrued in the period 1986-2005 varied from approximately 0 in Portugal to approximately 10 mSv in Gomel Oblast (Belarus) and Bryansk Oblast (Russia). The uncertainties in the dose estimates were subjectively estimated on the basis of the availability and reliability of the radiation data that were used for dose reconstruction in each country.

Ist die Stentthrombose die neue Achillesferse der interventionellen Kardiologie?

Der Einsatz von Koronarstents gehört zu den Grundpfeilern der perkutanen Koronarintervention. Die Stentthrombose ist dabei eine lebensbedrohliche Komplikation. Tritt sie auf, so erleiden bis zu 80% der Betroffenen einen Myokardinfarkt, bis zu 50% versterben. Durch die duale Plättchenaggregationshemmung konnten Stentthrombosen deutlich reduziert werden; die Inzidenz liegt heute unter 1%. Mit dem Aufkommen medikamentenfreisetzender Stents hat sich die Zeitspanne des Auftretens bis hin zu mehreren Jahren nach Implantation verlängert; die Gesamtinzidenz hat sich aber in Metaanalysen der randomisierten Studien nicht erhöht.

Ursächlich ist ein verzögerter vaskulärer Heilungsprozess sowie eine Kontakt- und Medikamenten-assoziierte Thrombozytenaktivierung. Vorbeugend wird daher eine standardisierte duale plättchenhemmende Therapie mit ASS und Clopidogrel empfohlen. Ihre Wirkung hängt von individuellen Faktoren ab. Durch die Bestimmung der Thrombozytenaggregationshemmung würde eine individuelle Dosisanpassung möglich, so dass thrombotische Nebenwirkungen und Blutungskomplikationen verringert werden könnten.

Incomplete denudation of oocytes prior to ICSI enhances embryo quality and blastocyst development

BACKGROUND

Granulosa cells are essential mediators of oocyte maturation and fertilization. Because of the denudation of oocytes in preparation for ICSI, any potential positive effect of surplus cumulus cells (CCs) on further development would be unable to exert further effect. In order to evaluate the actual influence of adhering cumulus cells on further preimplantation development, this prospective study was carried out.

METHODS

Sibling cumulus-oocyte complexes for 57 ICSI patients were split into a study group (incomplete denudation, n = 314) and a control group (complete denudation, n = 336). According to the cumulus cell pattern after partial denudation, mature gametes from the study group were further subdivided into type A oocytes, which showed several prominent CC clusters (n = 202), and type B (n = 75), which showed a more homogeneous pattern with CC covering the whole surface of the gamete.

RESULTS

In immature oocytes, presence of adhered CCs led to a significant increase in resumption of meiosis (P < 0.01). Fertilization rate (P < 0.05) and ability to cleave (P < 0.01) was impaired in the study group, because of difficulties in ICSI of type B oocytes. By contrast, embryo morphology on days 2 (P < 0.01) and 3 (P < 0.05), as well as blastocyst formation, was better (P < 0.05) in the study group (55 blastocysts out of 88 zygotes) as compared to that in the control group (49/105).

CONCLUSION

These data indicate that co-culture of oocytes with attached CCs may enhance preimplantation development.

Basal level of anti-Müllerian hormone is associated with oocyte quality in stimulated cycles

BACKGROUND

Serum anti-Müllerian hormone (AMH) levels provide a powerful means for predicting ovarian response, which is reflected not only by the size of the primordial follicle pool but also by the quality of the oocytes. Considering a mutual interdependence between AMH-expressing somatic cells and gametes, this prospective morphological study was set up to evaluate whether extreme AMH levels represent diminished oocyte quality and developmental incompetence.

METHODS

A total of 141 consecutive ICSI patients were subdivided into three groups using the 25th and 75th percentiles of the serum AMH levels (cycle day 3). In these three groups, morphology of all oocytes and fertilization rate, embryo quality and blastocyst formation were evaluated, and FSH, LH and estradiol (E(2)) levels were also measured.

RESULTS

Cycle cancellation rate was correlated with AMH levels (P < 0.05). AMH groups 1 (<1.66 ng/ml) and 3 (>4.52 ng/ml) showed oocytes of lower quality [dark central granulation, aggregation of smooth endoplasmic reticulum (sER)] compared with the median group 2 (1.66-4.52 ng/ml). Basal serum FSH did not allow for adequate prognosis in terms of gamete appearance. Fertilization and further cleavage up to blastocyst stage was not affected by AMH levels.

CONCLUSIONS

AMH seems to be superior to FSH in predicting both oocyte number and quality.

Evidence for a differential functional regulation of the two beta(3)-integrins alpha(V)beta(3) and alpha(IIb)beta(3)

The functional regulation of integrins is a major determinant of cell adhesion, migration and tissue maintenance. The binding of cytoskeletal proteins to various sites of integrin cytoplasmic domains is a key mechanism of this functional regulation. Expression of recombinant integrin alpha(IIb)beta(3) and alpha(M)beta(2) lacking the GFFKR-region in CHO cells results in constitutively activated integrins. In contrast, CHO cells stably expressing either a GFFKR-deleted alpha(V(del))beta(3) or a FF to AA-substituted alpha(V(AA))beta(3) do not reveal a constitutively activated integrin. Adhesion to immobilized fibrinogen is strongly impaired in alpha(V(del))beta(3) or alpha(V(AA))beta(3)-expressing cells, whereas it is not impaired in alpha(IIb)beta(3) and alpha(M)beta(2), both lacking the GFFKR-region. In a parallel plate flow chamber assay, alpha(V)beta(3)-expressing cells adhere firmly to fibrinogen and spread even at shear rates of 15 to 20 dyn/cm(2), whereas alpha(V(del))beta(3) or alpha(V(AA))beta(3) cells are detached at 15 dyn/cm(2). Actin stress fiber formation and focal adhesion plaques containing alpha(V)beta(3) are observed in alpha(V)beta(3) cells but not in alpha(V(del))beta(3) or alpha(V(AA))beta(3)-expressing cells. As an additional manifestation of impaired outside-in signaling, phosphorylation of pp125(FAK) was reduced in these cells. In summary, we report that the GFFKR-region of the alpha(V)-cytoplasmic domain and in particular two phenylalanines are essential for integrin alpha(V)beta(3) function, especially for outside-in signaling. Our results suggest that the two beta(3)-integrins alpha(IIb)beta(3) and alpha(V)beta(3) are differentially regulated via their GFFKR-region.