Exploitation of the enantioselectivity space of coated amylose tris(3,5-dimethylphenylcarbamate) in mixtures of 2-propanol and acetonitrile.

Chiral stationary phases (CSPs) with coated amylose tris(3,5-dimethylphenylcarbamate) (ADMPC) selector have long been recognized for their excellent chiral recognition ability in liquid chromatography. The conformational versatility behind this feature is the source of their known hysteretic behavior, which has been previously observed in polar organic (PO) mode eluents containing 2-propanol (IPA). Mixtures of IPA and acetonitrile (MeCN), a typical PO mode eluent system, have not been examined in this aspect yet, even though hysteresis is promising for finding unique unexplored enantioselectivities. Not only was the hysteresis detectable on ADMPC using mixtures of IPA and MeCN, but it was the typical behavior in a diverse set of test compounds. The difference in the retention time of the same analyte under conditions which only differed in the eluent history on the column can go up to 20-fold. The assumed hindered conformational changes of the selector were reflected in retention drift at certain eluent compositions. On the two sides of the transitions, distinct, useful states of the selector were detected. A series of IPA - MeCN compositions with defined pretreatment was selected and recommended as an extension of the preliminary, first choice method screening set that used only alcohols. The incorporation of a solvent possessing substantially different characteristics enhances the potential in practical applications, while keeping the technical simplicity. Stability and robustness of the additional states of the CSP were characterized. The examined columns of different brands shared the observed behavior. Kinetic stability of a column state is adequate for successful application. The evaluated states of ADMPC provide multiple enantiorecognition potential by using mixtures of IPA and MeCN also considering the pretreatment of the column. Unprecedented double and triple elution order reversals along the composition range supported the versatility of the available states. Our findings further enhance the usefulness of ADMPC-containing CSPs. We provide instructions for the application of the widespread chiral selector in common eluent mixtures to avoid pitfalls regarding reproducibility and robustness.

Covered Stents as a First-Line Treatment for Vascular Access Complications During Transfemoral Transcatheter Aortic Valve Implantation: Eight-Year Experience From a Single Center.

We report 8-year experience with vascular access complications (VACs) after percutaneous transfemoral transcatheter aortic valve implantation (TAVI). From January 2010 to January 2018, patients with iliofemoral VAC treated by an intervention following percutaneous transfemoral TAVI were included. Major VAC was defined according to the Valve Academic Research Consortium 2 classification. As first-line strategy, VACs were treated using covered nitinol stents (CS). Among 795 percutaneous transfemoral TAVI, 74 (9.3%) patients (female, 57%; 82 ± 8 years) with VAC treated by CS and/or open repair were included in this study: 59 CS cases and 15 open repair cases. Two CS patients were converted to open repair. Technical success for stent implantation was 97%. The main VAC was a persistent bleeding related to percutaneous closure device failure (72%). Thirty-day mortality in the study cohort was 5.4% (4/74), including 1 VAC-related death. One patient had postoperative lower limb ischemia successfully treated by open repair. No amputation, new-onset claudication or in-stent occlusion was recorded. Endovascular intervention using self-expandable nitinol covered stent is safe and effective as a first-line strategy for the treatment of VAC in percutaneous transfemoral TAVI. However, open repair is needed in case of unfeasibility or failure of endovascular therapy.