Flow cytometry is a well-established and powerful high- throughput fluorescence measurement tool that also allows for the sorting and enrichment of subpopulations of cells expressing unique fluorescence signatures. Owing to the reliance on intensity-only signals, flow cytometry sorters cannot easily discriminate between fluorophores that spectrally overlap. In this paper we demonstrate a new method of cell sorting using a fluorescence lifetime-dependent methodology. This approach, referred to herein as phase-filtered cell sorting (PFCS), permits sorting based on the average fluorescence lifetime of a fluorophore by separating fluorescence signals from species that emit differing average fluorescence lifetimes. Using lifetime-dependent hardware, cells and microspheres labeled with fluorophores were sorted with purities up to 90%. PFCS is a practical approach for separating populations of cells that are stained with spectrally overlapping fluorophores or that have interfering autofluorescence signals.
Non-rheumatic aortic stenosis (AS) is among the most common valvular diseases in the developed world. Current guidelines support aortic valve replacement (AVR) for severe symptomatic AS, which carries high morbidity and mortality when left untreated. In contrast, moderate AS has historically been thought to be a benign diagnosis for which the potential benefits of AVR are outweighed by the procedural risks. However, emerging data demonstrating the substantial mortality risk in untreated moderate AS and substantial improvements in periprocedural and perioperative mortality with AVR have challenged the traditional risk/benefit paradigm. As such, an appraisal of the contemporary data on morbidity and mortality associated with moderate AS and appropriate timing of valvular intervention in AS is warranted. In this review, we discuss the current understanding of moderate AS, including the epidemiology, current surveillance and management guidelines, clinical outcomes, and future studies.
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