Transcatheter aortic valve replacement acutely improves left ventricular mechanical efficiency in severe aortic stenosis: effects of different phenotypes.

AIM: Aortic stenosis is a frequent valvular disease, with transcatheter aortic valve implantation (TAVI) being performed when surgical replacement is at increased risk. However, TAVI-induced effects on myocardial efficiency are unknown. We aimed to investigate changes in LV mechano-energetic pre-/post-TAVI and their prognostic impact. METHODS: A total of 46 patients (25 males) received transesophageal and simultaneous radial pressure plus transaortic gradient monitoring before/immediately after prosthesis deployment. Efficiency was computed as external work/potential energy, as derived from LV pressure-volume plots; myocardial oxygen consumption (MVO2) was estimated as PWImod, i.e. a noninvasively validated alternative for MVO2 estimation. RESULTS: TAVI was successful in all patients, peak transaortic gradient decreasing - 40 ± 20 mmHg (p < 0.001). Efficiency improved post-TAVI (+ 0.6 ± 0.12; p = 0.004), with a concomitant PWImod reduction (- 16 ± 31%; p < 0.001). When contextualized to fixed PWImod value (5 ml/min/100 g), efficiency significantly affected survival (p = 0.029). Over 1026 ± 450-day follow-up, a change in efficiency pre-/post-TAVI ≤ 0.021 (median of the difference) predicted more deaths from any cause (30%) as compared with a change > 0.021 (17%), particularly in those patients with a pre-TAVI mean high-gradient (HG ≥ 40 mmHg) phenotype (p < 0.05). In particular, HG patients exhibited the lowest efficiency/PWImod ratio pre-/post-TAVI (p = 0.048), relative to the other aortic stenosis patients, suggestive of an unfavourable matching between cardiac function and metabolic demand, which foreshortens some intrinsic damaged muscle condition in these patients. CONCLUSION: LV mechanical efficiency improves immediately post-TAVI, notwithstanding an inhomogeneous mechano-energetic matching among the aortic stenosis patients, which can impact negatively on their long-term prognosis, particularly in those with the HG phenotype.

A general approach to describe the antimicrobial agent release from highly swellable films intended for food packaging applications.

A mathematical model able to describe the release kinetics of antimicrobial agents from crosslinked polyvinylalcohol (PVOH) into water is presented. The model was developed by taking into account the diffusion of water molecules into the polymeric film, the counter-diffusion of the incorporated antimicrobial agent from the film into water, and the polymeric matrix swelling kinetic. To validate the model the water sorption kinetics as well as the release kinetics of three antimicrobial agents (i.e., lysozyme, nisin and sodium benzoate, all approved to be used in contact with food) were determined at ambient temperature (25 degrees C). The three investigated active agents were entrapped in four films of PVOH with a different degree of crosslink. The model was successfully used to fit all the above sets of data, corroborating the validity of the hypothesis made to derive it.