Is electrical stimulation during administration of catecholamines required for the evaluation of success after ablation of atrioventricular node re-entrant tachycardias?

AbstractObjectivesThe purpose of this study was to answer the question of whether stimulation after administration of catecholamines is mandatory for identifying unsuccessful ablations of atrioventricular node re-entrant tachycardia (AVNRT).BackgroundThe success of radiofrequency (RF) catheter ablation in AVNRT is confirmed in many centers by noninducibility of tachycardias during stimulation after the administration of catecholamines.MethodsA total of 131 patients (81 women and 50 men; mean age 53.6 ± 13.7 years [range 20 to 77]) were studied. Electrical stimulation was performed without and with the beta-adrenergic amine Orciprenaline (metaproterenol) before and after RF catheter ablation.ResultsIn 100 patients (76.3%; confidence interval [CI] 68.1% to 83.3%) an AVNRT was inducible without administration of Orciprenaline. Thirty minutes after the initially successful ablation in 95 patients, tachycardia was inducible in none of these patients, not even after Orciprenaline administration. In the 31 patients (23.7%; CI 16.7% to 31.9%) in whom there was no tachycardia inducible before ablation, Orciprenaline was given, and the stimulation protocol was repeated. In only five patients (3.8%; CI 1.3% to 8.7%) was there still no tachycardia inducible. After an initially successful ablation in the 26 patients who had inducible tachycardias with Orciprenaline before ablation, no tachycardia could be re-induced. After Orciprenaline, the tachycardia was inducible again in only one patient.ConclusionsOnly patients who require catecholamines for tachycardia induction before ablation need catecholamines for control of the success of the ablation of AVNRT

Combined Surface Science and Density Functional Theory Approach towards Water Ordered Structures Formation on Magnetite

The interaction of water with iron oxide surfaces is relevant for several processes of practical interests, such as, the catalytic dehydrogenation of ethylbenzene to styrene over iron oxide based catalysts in the presence of steam, and the photocatalytic splitting of water over iron oxide electrodes. Three different adsorbed water species were distinguished on Fe-terminated Fe3O4 multilayer films using thermal desorption spectroscopy (TDS), and ultraviolet photoelectron spectroscopy (UPS) measured under adsorption-desorption equilibrium conditions [1]. By means of density functional theory (DFT) calculations, the first species (γ-water) were confirmed to correspond to dissociative water adsorption with the resulting hydroxyl (OH) groups of water on the surface iron (Fe) sites and the H-atoms adsorbed onto surface oxygen (O) sites. The DFT result for the γ-water structure is consistent with the two OH-stretch lines observed by infrared-reflection-adsorption-spectroscopy (IRAS) [2], and the UPS study [1]. The DFT calculations confirm the subsequent formation of dimeric water structures (β-water) formed by H-bonded molecular water to the surface OH-groups on surface-Fe, and the H on the surface-O sites, respectively, as suggested by the IRAS [2] and low energy electron diffraction (LEED) experiments [3]. The DFT results reveal that formation of the γ-water overlayer structure results from the diffusion of the mobile H-atoms from the initially molecular adsorbed water on iron sites followed by formation of a transition structrure with the H-atom adsorbed the nearest-neighboring oxygen sites, diffusing over the surface to adsorb on-top onto the next O-sites. This result is consistent with the proposed second-order kinetics of the recombinative adsorption process. and with scanning tunneling microscopy (STM) measurements of water adsorption on epitaxial Fe3O4 films

DFT-Rechnungen zur Adsorption und Dissoziation von Wasser auf Fe3O4(111)

Die Fe3O4(111)-Oberfläche ist regulär mit ¼ ML Eisen über einer vollen Sauerstofflage terminiert. Die anfängliche Adsorption von Wasser verläuft ungewöhnlich, nämlich dissoziativ [1,2] und ohne Aktivierungsschwelle [1]. DFT-Rechnungen zeigen, dass die Dissoziation über einen molekular auf Fe gebundenen Zwischenzustand erfolgt. Die OH-Gruppe bleibt auf diesem Platz während das abgespaltene H-Atom über zwei konkurrierende Wege zum übernächsten O-Platz gelangt, wo es eine strukturell unterschiedliche zweite OH-Gruppe bildet, in voller Übereinstimmung mit IRAS-Messungen [2]. Nach Sättigung dieser gamma-Spezies adsorbiert weiteres Wasser (beta-Spezies) molekular über Wasserstoffbrücken zu den beiden OH-Gruppen. Deren Bindungen zum Substrat bleiben erhalten sodass die gebildeten Aggregate nicht einem konventionellen Wasser-Dimer entsprechen. Die mögliche Rolle einer solchen Anordnung für die Aktivierung von Wasser in katalytischen Prozessen wird diskutiert. [1] Y. Joseph et. al., J. Phys. Chem. B 104 (2000) 3224. [2] U. Leist et al., Phys. Chem. Chem. Phys. 5 (2003) 2435