P3722Platelet reactivity changes following transcatheter aortic valve implantation

Introduction

Although recent studies described changes in platelet reactivity (PR) in days following transcatheter aortic valve implantation (TAVI), precise time course and duration of these changes have not been fully investigated.

Purpose

To investigate PR changes during and after TAVI.

Methods

Study included 42 consecutive patients with severe and symptomatic aortic stenosis undergoing TAVI procedure in our institution. Patients' clinical characteristics were collected from medical records. All patients who did not have chronic dual antiplatelet therapy received loading dose of aspirin and clopidogrel (300 mg) one day before the procedure followed by their standard maintenance doses for next three months. PR was measured in six time points: just before induction of anaesthesia (T1), after heparin administration (T2), at the end of procedure (T3), and on 3rd, 6th and 30th postoperative day (T4–6). PR was measured using impedance aggregometer (Multiplate® analyzer, Roche, Munich, Germany) in response to three platelet aggregation agonists: arachidonic acid (ASPItest), ADP (ADPtest) and thrombin receptor activating peptide-6 (TRAPtest).

Results

Mean patient age was 82.1 years with majority of patients being male 57.1% (N=24). Mean valve area and mean transvalvular gradient prior to procedure were 0.71±0.21 cm2 and 49.1±18.7 mmHg, respectively. All patients underwent successful TAVI procedure using either self-expandable (N=25, 59.5%) or balloon-expandable valve. Two patients (4.7%) underwent transapical TAVI, while transfemoral approach was used in all other patients. Mean postimplantation gradient was 10.2±7.1 mmHg.

Mean PR on T1 was 24.3±23.1 U for ASPItest, 41.6±26.5 U for ADPtest and 90.1±33.3 U for TRAPtest. There was no significant difference in PR on T2. However, on T3, ignificant reduction of PR in all 3 tests was observed (ASPI 9.4±10.1 U (p=0.001), ADP 23.1±15.0 U (p<0.001) and TRAP 64.5±27.3 U (p<0.001)). Lowest PR values for all tests were reached on T4, after which incline in PR has been observed. On T5, value of ASPItest reached levels not significantly different to those on T1 (15.1±17.2 U, p=0.13), while ADPtest and TRAPtest remained significantly lower (27.3±18.5 U, p=0.007 and 68.6±33.2 U, p=0.003, respectively). All PR values returned to initial levels on T6 (figure 1).

Conclusions

Our results show that successful TAVI procedure induces transient decrease in PR regardless of the platelet activation pathway. These findings add new knowledge in understanding complexed relations in intravascular milieu following TAVI. Further research on a larger number of patients is needed to confirm and asses clinical significance of these results.

Acknowledgement/Funding

Croatian Science Foundation

Bioavailability of Nutritional Resources From Cells Killed by Oxidation Supports Expansion of Survivors in Ustilago maydis Populations

After heavy exposure of Ustilago maydis cells to clastogens, a great increase in viability was observed if the treated cells were kept under starvation conditions. This restitution of viability is based on cell multiplication at the expense of the intracellular compounds freed from the damaged cells. Analysis of the effect of the leaked material on the growth of undamaged cells revealed opposing biological activity, indicating that U. maydis must possess cellular mechanisms involved not only in reabsorption of the released compounds from external environment but also in contending with their treatment-induced toxicity. From a screen for mutants defective in the restitution of viability, we identified four genes (adr1, did4, kel1, and tbp1) that contribute to the process. The mutants in did4, kel1, and tbp1 exhibited sensitivity to different genotoxic agents implying that the gene products are in some overlapping fashion involved in the protection of genome integrity. The genetic determinants identified by our analysis have already been known to play roles in growth regulation, protein turnover, cytoskeleton structure, and transcription. We discuss ecological and evolutionary implications of these results.

Drug-Eluting Balloons-A New Tool in the Treatment of Cardiac Allograft Vasculopathy: A Case Series

Percutaneous coronary intervention in patients with cardiac allograft vasculopathy is burdened with a lot of difficulties. Although they have allowed significant progress in comparison with plain balloon angioplasty and bare metal stents, drug-eluting stents have not fully overcome problems of diffuse lesions and small-vessel disease that are so common in transplant coronary artery disease. There is growing evidence that drug-eluting balloons might be a better choice for patients with small vessel atherosclerotic coronary disease and yet there is no experience with this technology in patients with cardiac allograft vasculopathy. Herein we report a case series of successful percutaneous coronary interventions in patients with cardiac allograft vasculopathy.

Silicon enhances leaf remobilization of iron in cucumber under limited iron conditions

BACKGROUND AND AIMS

Retranslocation of iron (Fe) from source tissues enhances plant tolerance to Fe deficiency. Previous work has shown that silicon (Si) can alleviate Fe deficiency by enhancing acquisition and root to shoot translocation of Fe. Here the role of Si in Fe mobilization in older leaves and the subsequent retranslocation of Fe to young leaves of cucumber (Cucumis sativus) plants growing under Fe-limiting conditions was investigated.

METHODS

Iron ((57)Fe or naturally occurring isotopes) was measured in leaves at different positions on plants hydroponically growing with or without Si supply. In parallel, the concentration of the Fe chelator nicotianamine (NA) along with the expression of nicotianamine synthase (NAS) involved in its biosynthesis and the expression of yellow stripe-like (YSL) transcripts mediating Fe-NA transport were also determined.

KEY RESULTS

In plants not receiving Si, approximately half of the total Fe content remained in the oldest leaf. In contrast, Si-treated plants showed an almost even Fe distribution among leaves with four different developmental stages, thus providing evidence of enhanced Fe remobilization from source leaves. This Si-stimulated Fe export was paralleled by an increased NA accumulation and expression of the YSL1 transporter for phloem loading/unloading of the Fe-NA complex.

CONCLUSIONS

The results suggest that Si enhances remobilization of Fe from older to younger leaves by a more efficient NA-mediated Fe transport via the phloem. In addition, from this and previous work, a model is proposed of how Si acts to improve Fe homeostasis under Fe deficiency in cucumber.

Management of heparin-induced thrombocytopenia with fondaparinux in a patient with left ventricular assist device

Heparin-induced thrombocytopenia is an immune-mediated serious adverse effect of heparin therapy. It is a relatively frequent complication among patients with mechanical circulatory support. Herein, we present a patient with severe heart failure and sepsis who developed heparin-induced thrombocytopenia shortly after implantation of left ventricular assist device as a bridge to transplantation and who was successfully treated with fondaparinux.

Silicon alleviates iron deficiency in cucumber by promoting mobilization of iron in the root apoplast

· Root responses to lack of iron (Fe) have mainly been studied in nutrient solution experiments devoid of silicon (Si). Here we investigated how Si ameliorates Fe deficiency in cucumber (Cucumis sativus) with focus on the storage and utilization of Fe in the root apoplast. · A combined approach was performed including analyses of apoplastic Fe, reduction-based Fe acquisition and Fe-mobilizing compounds in roots along with the expression of related genes. · Si-treated plants accumulated higher concentrations of root apoplastic Fe, which rapidly decreased when Fe was withheld from the nutrient solution. Under Fe-deficient conditions, Si also increased the accumulation of Fe-mobilizing compounds in roots. Si supply stimulated root activity of Fe acquisition at the early stage of Fe deficiency stress through regulation of gene expression levels of proteins involved in Fe acquisition. However, when the period of Fe deprivation was extended, these reactions further decreased as a consequence of Si-induced enhancement of the Fe status of the plants. · This work provides new evidence for the beneficial role of Si in plant nutrition and clearly indicates that Si-mediated alleviation of Fe deficiency includes an increase of the apoplastic Fe pool in roots and an enhancement of Fe acquisition.

Antioxidative enzymes in the response of buckwheat (Fagopyrum esculentum Moench) to complete submergence

Oxidative stress and antioxidative defense system activity were studied in buckwheat leaves after complete submergence and re-aeration. The levels of H2O2 and lipid peroxidation were found to be significantly higher in stressed than in untreated buckwheat leaves. Enzymes catalyzing the degradation of H2O2 and peroxides were shown to participate actively, whereas superoxide dismutase did not take part in the buckwheat leaf response to flooding stress. The most prominent increase in antioxidative enzyme activities was noticed upon return to air, when the strongest oxidative stress occurred and the need for antioxidative defense was the greatest.