Conservative initial postoperative anticoagulation strategy after HeartMate 3 left ventricular assist device implantation

Introduction

Although anticoagulation therapy is mandated after implantation of a left ventricular assist device (LVAD), postoperative bleedings and reoperations occur relatively frequently and are associated with worse outcomes. We evaluated the use of a conservative postoperative anticoagulation protocol in patients implanted with a HeartMate 3 (HM3) LVAD.

Methods

In a single-centre retrospective analysis of postoperative outcomes after HM3 LVAD implantation, a standard (old) anticoagulation protocol (i.e. early, full-dose anticoagulation with low-molecular weight heparin and overlapping vitamin K antagonist) was compared with a new conservative anticoagulation protocol (i.e. slow initiation of vitamin K antagonists without overlapping heparin). Main outcomes were changes in international normalised ratio (INR), lactate dehydrogenase (LDH), bleeding and/or tamponade events requiring reoperation, length of stay and adverse events.

Results

In total, 73 patients (48 in old vs 25 in new protocol group) were evaluated. Mean age was 56 years (standard deviation 13) and most patients (78%) were males. Changes in INR and LDH in the first 14 days were similar in both groups (p?=?0.50 and p?=?0.997 for interaction, respectively). Number of bleeding/tamponade events requiring reoperation was lower in the new than in the old protocol group (4% vs 33%, p?=?0.005). Postoperative 30-day mortality was similar, and we observed no thromboembolic events. Median (25th–75th percentiles) total length of postoperative hospital stay (27 (25–41) vs 21 (19–27) days, p?<?0.001) and length of intensive care unit stay (5 (2–9) vs 2 (2–5) days, p?=?0.022) were significantly shorter in the new protocol group.

Conclusion

These retrospective data suggest that conservative slow initiation of anticoagulation therapy after HM3 LVAD implantation is associated with less bleeding/tamponade events requiring reoperation, a similar safety profile and a shorter duration of stay than the currently advised standard anticoagulation protocol.

     

Stage-specific expression of a Schistosoma mansoni polypeptide similar to the vertebrate regulatory protein stathmin

The ubiquitous vertebrate protein stathmin is expressed and phosphorylated in response to a variety of external and internal signals. Stathmin, in turn, controls cell growth and differentiation through its capacity to regulate microtubule assembly dynamics. This is the first report on the molecular cloning and characterization of a stathmin-like protein (SmSLP) in an invertebrate, the human blood fluke Schistosoma mansoni. SmSLP is first synthesized at high levels in the intermediate molluscan host and completely disappears 48 h after penetration into the mammalian host. The protein is preferentially iodinated in intact immature parasites using the Bolton-Hunter reagent, can be quantitatively extracted in high salt buffers, and remains soluble after boiling. Native SmSLP was partially sequenced, and its complete structure was derived from the cloning and sequencing of its cDNA. The sequence is up to 26% identical to vertebrate stathmin sequences and contains two potential phosphorylation sites. Native SmSLP is indeed phosphorylated because phosphatase digestion shifts its mobility in electrofocusing gels. SmSLP associates with tubulin, as suggested by immune co-precipitation results. In vitro experiments demonstrated that SmSLP inhibits tubulin assembly and causes the depolymerization of preassembled microtubules, thus probably fulfilling regulatory roles in critical steps of schistosome development.     

Flow cytometric DNA ploidy, p53, PCNA, and c-erbB-2 protein expressions as predictors of survival in surgically resected gastric cancer patients

In order to determine retrospectively the impact of some cytometric and immunohistochemical parameters on the overall survival of gastric cancer patients treated with surgery alone, paraffin-embedded tumor samples from 137 gastric carcinoma patients undergoing curative resection from 1987-1993 were analyzed by flow cytometry (FCM) and immunohistochemistry (p53, c-erbB-2, and PCNA expression). FCM-derived parameters were DNA ploidy and fraction of S-phase cells (SPF). Multiple regression analysis was applied to determine the prognostic significance of the conventional clinicopathologic findings together with the flow cytometric and immunohistochemical parameters on overall survival. When all parameters were entered simultaneously into the Cox regression model, stage and DNA ploidy (DNA index >1.35) clearly emerged as the only independent prognostic factors. When the stages were analysed separately, the independent prognostic factors resulted DNA ploidy in early stages (I-II) and grading in stage IIIA tumors. For stage IIIB tumors, no independent prognostic factor was found. These results indicate that the DNA ploidy pattern is a valuable predictor of survival in curatively resected gastric cancer patients, especially when less advanced tumors are taken into consideration.     

Identification of a 14mer RNA that recognizes and binds flavin mononucleotide with high affinity

Aptamers are nucleic acids developed by in vitro evolution techniques that bind to specific ligands with high affinity and selectivity. Despite such high affinity and selectivity, however, in vitro evolution does not necessarily reveal the minimum structure of the nucleic acid required for selective ligand binding. Here, we show that a 35mer RNA aptamer for the cofactor flavin mononucleotide (FMN) identified by in vitro evolution can be computationally evolved to a mere 14mer structure containing the original binding pocket and eight scaffolding nucleotides while maintaining its ability to bind in vitro selectively to FMN. Using experimental and computational methodologies, we found that the 14mer binds with higher affinity to FMN (K_D ~ 4 µM) than to flavin adenine dinucleotide (K_D ~ 12 µM) or to riboflavin (K_D ~ 13 µM),despite the negative charge of FMN. Different hydrogen-bond strengths resulting from differing ring-system electron densities associated with the aliphatic-chain charges appear to contribute to the selectivity observed for the binding of the 14mer to FMN and riboflavin. Our results suggest that high affinity and selectivity in ligand binding is not restricted to large RNAs, but can also be a property of extraordinarily short RNAs.     

Minimum sequence requirements for the binding of paromomycin to the rRNA decoding site A

We have recently introduced a computational methodology that combines molecular dynamics (MD) simulations, free-energy calculations, and in vitro binding assays to predict the minimum RNA structural requirements for selective, high-affinity RNA binding to small-molecule ligands. Here, we show that this methodology can be applied to the conformationally flexible aminoglycoside antibiotic paromomycin. A RNA consisting of an 11-mer:10-mer duplex that contains one 16S ribosome RNA decoding A-site bound to paromomycin was simulated for 4 ns. The methodology predicts that the 11-mer:10-mer duplex binds to paromomycin with high affinity, whereas smaller RNA duplexes lose complex stability and the ability to bind paromomycin. The predicted high-affinity binding to paromomycin of the 11-mer:10-mer duplex was confirmed experimentally (EC(50) = 0.28 microM), as well as the inability of smaller complexes to bind. Our simulations show good agreement with experiment for dynamic and structural properties of the isolated A-site, including hydrogen-bonding networks and RNA structural rearrangements upon ligand binding. The results suggest that MD simulations can supplement in vitro methods as a tool for predicting minimum RNA-binding motifs for both small, rigid ligands, and large, flexible ligands when structural information is available.