Using panoramic non-invasive mapping in humans, focal or reentrant sources driving AF waves were identified, originating from multiple distinct regions and exhibiting short lifespans and periodic recurrences in the same locations. We characterized AF drivers in patients with persistent AF (lasting less than 1 year) using novel high resolution mapping, imaging and modelling approaches with the objective of evaluating their relationship to atrial structural heterogeneities. A wide spectrum of mechanisms have been described in experimental studies, ranging from a single localized stable (focal/reentrant) source, to multiple sources, up to diffuse bi-atrial wavelets. These data from clinical, imaging and computational studies strongly suggest that intermittent and spatially unstable drivers anchoring to structural heterogeneities are a major pathophysiological mechanism in human persistent atrial fibrillation.Ībstract = "The mechanisms responsible for perpetuation of human persistent atrial fibrillation (AF) are controversial and probably vary between individuals. Finally, random microstructural alterations devoid of cellular electrical changes were modelled, showing that a percolation mechanism could also explain atrial reentries and complex fractionated electrograms. In patient-specific computer simulations, sustained AF was shown to be driven by meandering transitory reentries attached to fibrosis borders expressing specific metrics in density and extent. MRI atrial imaging demonstrated that such drivers preferentially clustered at the borders of fibrotic atrial regions. The reentrant driver regions harboured long, fractionated electrograms covering most of the fibrillatory cycle lengths with varying beat-to-beat sequences suggestive of unstable trajectories attached to slow conducting heterogeneous tissue. If you're making a Scrubby dishcloth for example, it doesn't matter if the finished item is exactly the correct size or uses slightly more of the ball of Scrubby.The mechanisms responsible for perpetuation of human persistent atrial fibrillation (AF) are controversial and probably vary between individuals. Other times, instead of a gauge, there may just be a note that the gauge is not important for the project. For example, a throw made of squares might give the gauge as the finished size of a square. įor patterns made of individual pieces, the gauge might be given as the size of a finished piece. For example, for a ripple pattern, the gauge may say that from one point to another point of the ripple is 5". Sometimes the gauge is given in pattern repeats. If the pattern calls for multiple sizes of hooks, use the size mentioned in the gauge. If no pattern is given for the gauge, work in whatever the main stitch for the item is. If different gauges are given for different stitch patterns, make sure you make a swatch for each stitch pattern. Work in the same pattern that the gauge calls for. Chain enough stitches for your swatch to be 5-6 inches across and crochet enough rows to make a square. When crocheting a gauge swatch, always work with the same yarn you're using for the main item.
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