P1411 Ultrasound-guided transseptal access in catheter ablation of left-sided tachyarrhythmias - single centre experience

Background

Transseptal puncture (TSP) for catheter ablation (CA) of left-sided tachycardias is traditionally performed with the aid of fluoroscopy. Compared to fluoroscopy, intracardiac echocardiography (ICE) can provide better orientation and imaging of soft tissue structures that are relevant to TSP.

Objective

Our aim was to evaluate feasibility and safety of ICE-guided TSP in CA treatment of left-sided tachyarrhythmias.

Methods

Consecutive fluoroless CA procedures with combined use of three-dimensional electroanatomic mapping system and ICE requiring TSP were evaluated in 357 patients (269 male, mean age 54 ± 18 years) referred to our hospital from July 2014 to November 2018. Among CA treated left-sided tachyarrhythmias 55 patients had accessory pathway, 16 had focal atrial tachycardia, 276 had atrial fibrillation or atypical atrial flutter and 10 had ventricular tachycardia. Success of transseptal access and complications related to TSP were analyzed. Adverse event requiring additional intervention was defined as major complication.

Results

Double TSPs were performed in 253 patients and single in 104 patients. Additional ablation procedures were needed in 26 patients and the rest had a single CA procedure. Altogether, 661 TSPs (274 double and 111 single) were attempted and 659 were successful (99.7%). Both TSPs failed due to severely thickened interatrial septum after previous cardiac surgery. In 14 patients (21 TSPs, 3.2%) a cardiac implantable electronic device (CEID) was present. ICE provided excellent lead visualisation and no lead dislodgements were recorded. Additional radiofrequency energy application to the transseptal needle was used for 3 challenging TSPs. Minor complications (pericardial effusions managed conservatively) occurred after 7 double TSP procedures (12/661, 1.8%). Major complication with pericardial tamponade (requiring pericardiocentesis) occurred during one double TSP (2/661, 0.3%). No TSP-related embolic complications were observed.

Conclusion

ICE-guided TSP in CA of left-sided tachyarrhythmias is safe with excellent success rates. In addition, ICE could provide additional reassurance in difficult cases and in patients with CEIDs.

Determination of the Structures of Uranyl-Tri-n-butyl-Phosphate Aggregates by Coupling Experimental Results with Molecular Dynamic Simulations

The complex structure of a plutonium uranium refining by extraction (PUREX) process organic phase was characterized by combining results from experiments and molecular dynamics simulations. For the first time, the molecular interactions between tri-n-butyl phosphate (TBP) and the extracted solutes, as well as TBP aggregation after the extraction of water and/or uranyl nitrate, were described and analyzed concomitantly. Coupling molecular dynamics simulations with small- and wide-angle X-ray scattering (SWAXS) experiments can lead to simulated organic solutions that are representative of the experimental ones, even for high extractant and solute concentrations. Furthermore, this coupling is well adapted for the interpretation of SWAXS experiments without preliminary hypothesis on the size or shape of aggregates. The results link together previous literature studies obtained for each level of depiction separately (complexation or aggregation). Without uranium, or at low metal concentration, almost no aggregation was observed. At high uranium concentration, organic phases contain small [UO₂ (NO₃ )₂ (TBP)₂ ]_n polymetallic aggregates (with n=2 to 4), in which the 1:2 U/TBP stoichiometry is preserved.

Synthesis and hydrolysis of gas-phase lanthanide and actinide oxide nitrate complexes: a correspondence to trivalent metal ion redox potentials and ionization energies

Gas-phase hydrolysis of lanthanide/actinide MO₃(NO₃)₃⁻ions relates to the stabilities of the M^IVoxidation states, which correlate with IV/III solution reduction potentials and 4th ionization energies.

Complexation-induced supramolecular assembly drives metal-ion extraction

Combining experiment with theory reveals the role of self-assembly and complexation in metal-ion transfer through the water-oil interface. The coordinating metal salt Eu(NO3)3 was extracted from water into oil by a lipophilic neutral amphiphile. Molecular dynamics simulations were coupled to experimental spectroscopic and X-ray scattering techniques to investigate how local coordination interactions between the metal ion and ligands in the organic phase combine with long-range interactions to produce spontaneous changes in the solvent microstructure. Extraction of the Eu(3+)-3(NO3(-)) ion pairs involves incorporation of the "hard" metal complex into the core of "soft" aggregates. This seeds the formation of reverse micelles that draw the water and "free" amphiphile into nanoscale hydrophilic domains. The reverse micelles interact through attractive van der Waals interactions and coalesce into rod-shaped polynuclear Eu(III) -containing aggregates with metal centers bridged by nitrate. These preorganized hydrophilic domains, containing high densities of O-donor ligands and anions, provide improved Eu(III) solvation environments that help drive interfacial transfer, as is reflected by the increasing Eu(III) partitioning ratios (oil/aqueous) despite the organic phase approaching saturation. For the first time, this multiscale approach links metal-ion coordination with nanoscale structure to reveal the free-energy balance that drives the phase transfer of neutral metal salts.

On the structure of thorium and americium adenosine triphosphate complexes

PURPOSE

The actinides are chemical poisons and radiological hazards. One challenge to better appraise their toxicity and develop countermeasures in case of exposure of living organisms is to better assess pathways of contamination. Because of the high chemical affinity of those actinide elements for phosphate groups and the ubiquity of such chemical functions in biochemistry, nucleotides and in particular adenosine triphosphate nucleotide (ATP) may be considered critical target building blocks for actinides.

MATERIALS AND METHODS

Combinations of spectroscopic techniques (Fourier transformed Infra Red [FTIR], Electrospray Ionization Mass Spectrometry [ESI-MS], and Extended X-ray Absorption Fine Structure [EXAFS]) with quantum chemical calculations have been implemented in order to assess the actinides coordination arrangement with ATP.

RESULTS

We describe and compare herein the interaction of ATP with thorium and americium; thorium(IV) as a representative of actinide(IV) like plutonium(IV) and americium(III) as a representative of all heavier actinides. In the case of thorium, an insoluble complex is readily formed. In the case of americium, a behavior identical to that described previously for lutetium has been observed with insoluble and soluble complexes.

CONCLUSIONS

The comparative study of ATP complexation with Th(IV) and Am(III) shows their ability to form insoluble complexes for which a structural model has been proposed by analogy with previously described Lu(III) complexes.

Thermo-responsive Metal-chelating Surfactants: Properties and Use in Cloud Point Extraction of Uranyl Nitrate∗

The properties of new thermo-responsive functional surfactants, capable of forming a metal chelate, synthesized by grafting a diamide group (amino-acid residue) to the tip hydrophilic endgroup or in a branched position to polyoxyethylene nonionic surfactants [CiEj: CiH2i+1(OCH2CH2)jOH)], are studied. Their use in cloud point extraction of uranyl nitrate is tested. The reversible temperature-dependent behavior of classical non-ionic surfactants associated to phase separation of micellar solutions known as clouding behavior is exploited for separation based on cation specific binding to the chelating group. The functional surfactants under investigation combine surface-active properties and characteristic thermoreversible behavior with a capacity to bind uranyl cation. The influence of the complexation on the cloud points of functional surfactants is determined. The chelating surfactants are found efficient for the cloud point extraction of uranyl nitrate at low surfactant-to-uranyl ratio. These new thermoresponsive surfactants with chelating properties hold most promise for the development of new solvent free extraction processes.

Influence of gamma irradiation on hydrophobic room-temperature ionic liquids [BuMeIm]PF6 and [BuMeIm](CF3SO2)2N

Stability of neat hydrophobic Room-Temperature Ionic Liquids (RTIL) [BuMeIm]X, where [BuMeIm]+ is 1-butyl-3-methylimidazolium and X- is PF6-, and (CF3SO2)2N-, was studied under gamma radiolysis (137Cs) in an argon atmosphere and in air. It was found that the density, surface tension, and refraction index of RTILs are unchanged even by an absorbed dose of approximately 600 kGy. Studied RTILs exhibit considerable darkening when subjected to gamma irradiation. The light absorbance of ionic liquids increases linearly with the irradiation dose. Water has no influence on radiolytic darkening. A comparative study of [BuMeIm]X and [Bu4N][Tf2N] leads to the conclusion that the formation of colored products is related to gamma radiolysis of the [BuMeIm]+ cation. The radiolytic darkening kinetics of RTILs is influenced by the anions as follows: Cl- < (CF3SO2)2N- < PF6-. Electrospray ionization mass spectrometry and NMR analysis reveal the presence of nonvolatile radiolysis products at concentrations below 1 mol% for an absorbed dose exceeding 1200 kGy. Initial step of BuMeIm+ cation radiolysis is the loss of the Bu* group, the H* atom from the 2 position on the imidazolium ring, and the H* atom from the butyl chain. Radiolysis of ionic liquid anions yields F* and CF3* from PF6- and [Tf2N]-, respectively. Recombinations of these primary products of radiolysis lead to various polymeric and acidic species.