Results of first stage brachiobasilic and brachiobrachial fistula creation: Implications for staged versus single procedure decision making.

INTRODUCTION: Transposed brachiobasilic AV fistulas (BVT) have increasingly been performed in two stages. Published reports give conflicting results, perhaps in part as many reports of staged procedures eliminate those patients who "fail" the first stage (i.e. are lost to follow-up in addition to anatomic failure). METHODS: A prospectively maintained database was reviewed to identify all patients at two institutions who underwent the first stage of planned two-stage BVT by the senior author. Success in this context was defined as patients who eventually underwent second stage fistula creation, leaving the operating room after the second stage with a patent, transposed fistula. RESULTS: From October 2012 to June 2020, 218 patients underwent first-stage procedures. At the first visit, 185 (85%) of fistulas were patent, 23 (11%) were occluded, 8 (4%) of patients were lost to follow-up, and 2 (1%) died. In the interval before the second operation, another eight (4%) patients were lost to follow-up, two were cancelled for medical reasons, and two declined surgery, leaving a total of 173 patients who made it to the second stage (80%). At operation, four patients were found to have unusable veins, leaving a total of 169 patients who completed both stages. If all patients who underwent first stage are included, 77% of patients entering this pathway left the OR after their second stage with patent access. If those lost to follow-up are excluded, this number increases to 84%, while if all those lost to follow-up are assumed to mature, success increases to 85%. CONCLUSIONS: Depending on results in patients lost to follow-up, between 77% and 85% of patients undergoing first stage brachiobasilic fistulae undergo successful second stage transposition. These numbers are equivalent or slightly lower than published maturation rates for single-stage BVT, so there is little margin for failure at the second stage.

A time-related parametric risk factor analysis for postoperative atrial fibrillation after heart surgery.

OBJECTIVES: Multiple mechanisms may be involved in postoperative atrial fibrillation. Therefore, our objective was to determine the risk factors for postoperative atrial fibrillation as a function of time after coronary artery bypass grafting or valve surgeries to determine which risk factors might predominate at different times. METHODS: Parametric hazard functions were determined for 1583 patients and then in subgroups (coronary artery bypass grafting alone, mitral valve procedure, and aortic valve replacement +/- coronary artery bypass grafting). Multivariable risk factor analyses were performed, and the risk for postoperative atrial fibrillation was estimated. RESULTS: The risk for postoperative atrial fibrillation for all patients was highest immediately postoperatively and at 48 hours. The initial peak risk declined to approximately zero within 18 hours postoperatively. A second peak occurred at 48 hours, followed by a slow decline over the following 4 to 7 days. The time intervals encompassing these peaks were termed phase I and phase II. Predominant risk factors in phase I were older age (relative risk [RR], 1.6; P = .006), longer crossclamp time (RR, 1.3; P = .001), and mitral valve procedure (RR, 2.5; P = .0001). In phase II, these were older age (RR, 3.0; P < .0001), greater weight (RR, 1.6; P < .0001), and Caucasian race (RR, 2.5; P = .006). For patients receiving a mitral valve procedure, the risk for postoperative atrial fibrillation in phase II was higher and remained elevated for as long as 9 days postoperatively in comparison with isolated coronary artery bypass grafting, for which the risk returned to near baseline by postoperative day 6. CONCLUSIONS: Phase I and phase II periods are associated with distinct risk factors; therefore, it is likely that the mechanisms of postoperative atrial fibrillation change over time.

Third row transition metal hexafluorides, extraordinary oxidizers, and Lewis acids: electron affinities, fluoride affinities, and heats of formation of WF6, ReF6, OsF6, IrF6, PtF6, and AuF6.

High level electronic structure calculations were used to evaluate reliable, self-consistent thermochemical data sets for the third row transition metal hexafluorides. The electron affinities, heats of formation, first (MF(6) --> MF(5) + F) and average M-F bond dissociation energies, and fluoride affinities of MF(6) (MF(6) + F(-) --> MF(7)(-)) and MF(5) (MF(5) + F(-) --> MF(6)(-)) were calculated. The electron affinities which are a direct measure for the oxidizer strength increase monotonically from WF(6) to AuF(6), with PtF(6) and AuF(6) being extremely powerful oxidizers. The inclusion of spin orbit corrections is necessary to obtain the correct qualitative order for the electron affinities. The calculated electron affinities increase with increasing atomic number, are in good agreement with the available experimental values, and are as follows: WF(6) (3.15 eV), ReF(6) (4.58 eV), OsF(6) (5.92 eV), IrF(6) (5.99 eV), PtF(6) (7.09 eV), and AuF(6) (8.20 eV). A wide range of density functional theory exchange-correlation functionals were also evaluated, and only three gave satisfactory results. The corresponding pentafluorides are extremely strong Lewis acids, with OsF(5), IrF(5), PtF(5), and AuF(5) significantly exceeding the acidity of SbF(5). The optimized geometries of the corresponding MF(7)(-) anions for W through Ir are classical MF(7)(-) anions with M-F bonds; however, for PtF(7)(-) and AuF(7)(-) non-classical anions were found with a very weak external F-F bond between an MF(6)(-) fragment and a fluorine atom. These two anions are text book examples for "superhalogens" and can serve as F atom sources under very mild conditions, explaining the ability of PtF(6) to convert NF(3) to NF(4)(+), ClF(5) to ClF(6)(+), and Xe to XeF(+) and why Bartlett failed to observe XePtF(6) as the reaction product of the PtF(6)/Xe reaction.