The aim of the present study was to compare the enantioseparation performance of chiral stationary phases (CSPs) which were derived from chitosans of different sources and molecular weights. Therefore, chitosans of shrimp and crab shells were prepared. The viscosity-average molecular weights of the chitosans both prepared from shrimp and crab shells were 2.8 × 105 and 1.4 × 105. The chitosans were isobutyrylated yielding isopropylcarbonyl chitosans which were then derivatized with 4-methylphenyl isocyanate to provide chitosan 3,6-bis(4-methylphenylcarbamate)-2-(isobutyrylamide)s. The chitosan 3,6-bis(4-methylphenylcarbamate)-2-(isobutyrylamide)s were used as chiral selectors (CSs) with which the corresponding CSPs were prepared. With the same chiral analytes and under the same mobile phase conditions, the enantioseparation capability of the CSPs was evaluated by high-performance liquid chromatography. In two CSs prepared from the same source, the one with higher molecular weight showed better enantioseparation capability; in two CSs prepared with the chitosans of the same molecular weight, the one derived from shrimp shell exhibited better performance. With regard to the two shrimp chitosan CSs, most of chiral analytes interacted more strongly with the one with lower molecular weight, and an opposite trend was found for the two crab chitosan CSs. Based on the results observed in the present study and in previous work, we believe that the influence of molecular weight on CSP enantioseparation performance is related to the substituent introduced in the CS molecule. OBJECTIVES The aim of this study was to determine the safety and efficacy of chimney stenting, a bailout technique to treat coronary artery occlusion (CAO). BACKGROUND CAO during transcatheter aortic valve replacement (TAVR) is a rare but often fatal complication. METHODS In the international Chimney Registry, patient and procedural characteristics and data on outcomes are retrospectively collected from patients who underwent chimney stenting during TAVR. RESULTS To date, 16 centers have contributed 60 cases among 12,800 TAVR procedures (0.5%). Chimney stenting was performed for 2 reasons 1) due to the development of an established CAO (n = 25 [41.6%]); or 2) due to an impending CAO (n = 35 [58.3%]). The majority of cases (92.9%) had 1 or more classical risk factors for CAO. Upfront coronary protection was performed in 44 patients (73.3%). Procedural and in-hospital mortality occurred in 1 and 2 patients, respectively. Myocardial infarction (52.0% vs. 0.0%; p  less then  0.01), cardiogenic shock (52.0% vs. 2.9%; p  less then  0.01), and resuscitation (44.0% vs. 2.9%; p  less then  0.01) all occurred more frequently in patients with established CAO compared with those with impending CAO. The absence of upfront coronary protection was the sole independent risk factor for the combined endpoint of death, cardiogenic shock, or myocardial infarction. During a median follow-up time of 612 days (interquartile range 405 to 842 days), 2 cases of stent failure were reported (1 in-stent restenosis, 1 possible late stent thrombosis) after 157 and 374 days. CONCLUSIONS Chimney stenting appears to be an acceptable bailout technique for CAO, with higher event rates among those with established CAO and among those without upfront coronary protection. OBJECTIVES The aim of this study was to evaluate the feasibility of coronary access and aortic valve reintervention in low-risk patients undergoing transcatheter aortic valve replacement (TAVR) with a balloon-expandable transcatheter heart valve (THV). BACKGROUND Younger, low-risk TAVR patients are more likely than older, higher risk patients to require coronary angiography, percutaneous coronary intervention, or aortic valve reintervention, but their THVs may impede coronary access and cause coronary obstruction during TAVR-in-TAVR. METHODS The LRT (Low Risk TAVR) trial (NCT02628899) enrolled 200 subjects with symptomatic severe aortic stenosis to undergo TAVR using commercially available THVs. Subjects who received balloon-expandable THVs and who had 30-day cardiac computed tomographic scans were included in this study. In a subgroup, the feasibility of intentional THV crimping on the delivery catheter to pre-determine commissural alignment was tested. RESULTS In the LRT trial, 168 subjects received balloon-expandable THVs and had 30-day cardiac computed tomographic scans, of which 137 were of adequate image quality for analysis.  https://www.selleckchem.com/products/gpna.html  The most challenging anatomy for coronary access (THV frame above and commissural suture post in front of a coronary ostium) was observed in 9% to 13% of subjects. Intentional THV crimping did not appear to meaningfully affect commissural alignment. The THV frame extended above the sinotubular junction in 21% of subjects, and in 13%, the distance between the THV and the sinotubular junction was  less then 2 mm, signifying that TAVR-in-TAVR may not be feasible without causing coronary obstruction. CONCLUSIONS TAVR may present challenges to future coronary access and aortic valve reintervention in a substantial number of low-risk patients. OBJECTIVES The authors sought to estimate possible interference of the Medtronic Evolut R/Pro transcatheter heart valve (THV) frame with coronary access using multislice computed tomography (MSCT) data. BACKGROUND Lower-risk patients undergoing transcatheter aortic valve replacement (TAVR) endure a high cumulative risk of coronary events, but coronary access can be challenging. METHODS In 101 patients who received an Evolut R/Pro THV, post-TAVR MSCT (performed at a median of 30 days after TAVR) was used to assess possible interference of the elements of the THV frame with coronary access. RESULTS The closest cell of the THV frame vertically aligned with the coronary ostium was located opposite the ostium in 58% and 63%, below the ostium in 22% and 30%, or above the ostium in 20% and 7% of left and right coronary arteries, respectively. The free sinus of Valsalva space between the THV frame and the coronary ostium was 0.45 ± 0.17 cm and 0.44 ± 0.17 cm for the left and right coronary arteries, respectively, and showed a stepwise decrease with decreasing THV size (p  less then  0.