Comparison of clockwise and counterclockwise right atrial flutter using high-resolution mapping

Background To the best of our knowledge, few studies have been performed that explore the electrophysiological differences between clockwise (CW) and counterclockwise (CCW) right atrial (RA) cavotricuspid isthmus (CTI)-dependent atrial flutter (AFL) using the high-resolution Rhythmia mapping system. Objectives. Accordingly, our prospective cohort study, sought to compare CW and CCW CTI-dependent AFL in preselected pure right AFL patients (pts) using the ultra-high-definition (ultra-HD) Rhythmia mapping system. The study also aimed to mathematically develop a cartography model based on automatic velocity RA measurements to identify electrophysiological AFL specificities. Methods and results Between October 2019 and July 2020, 33 patients were recruited. The mean age was 71±13 years old. No difference was found concerning clinical variables between CCW AFL and CW AFL or regarding left ventricular ejection fraction (LVEF) (55.5±10 vs. 56.6±12; p=0.76). The AFL cycle length was very similar (248±20 vs. 252±28 ms; p=0.6). The sinus venosus (SV) block line was present in 32/33 of cases (97%) and no significant difference was found between CCW and CW CTI AFL (100% vs. 91%; p=0.7). No line was localized in the region of the crista terminalis (CT). A superior gap was present in the posterior line in 14/31 (45.2%) but this was similarly present in CCW AFL, when compared to CW AFL (10/22 [45.5%] vs. (4/10 [40%]); p=0.9). When present, the extension of the posterior line of block was observed in 18/31 pts (58%) without significant differences between CCW and CW CI AFL (12/22 [54.5%] vs. (6/10 [60%]) (p=.9) The Eustachian ridge line of block was similarly present in both groups (82% [18/22] vs. 45.5% [5/11]; p=0.2). The absence of the Eustachian ridge line of block led to significantly slowed velocity in this area (28±10cm/s; n=8),and the velocities were similarly altered between both groups (26±10 [4/22] vs. 29.8±11cm/s [4/11]; p=0.6). We created mathematical, three-dimensional RA reconstruction-velocity model measurements. In each block localization, when the block line was absent, velocity was significantly slowed (≤20cm/s). A systematic slowdown in conduction velocity was observed at the entrance and exit of the CTI in 100% of cases. This alteration to the conduction entrance was localized at the lateral side of the CTI for the CCW AFL and at the septal side of the CTI for CW AFL. The exit-conduction alteration was localized at the CTI septal side for the CCW AFL and at the CTI lateral side for the CW AFL. The only differences between CW and CCW AFL concerned activation patterns. Conclusions The ultra-HD Rhythmia mapping system confirmed the absence of significant electrophysiological differences between CCW and CW AFL. The mechanistic posterior SV and Eustachian ridge block lines were confirmed in each arrhythmia. A systematic slowing down at the entrance and exit of the CTI was demonstrated in both CCW and CW AFL, but in reverse positions. FUNDunding Acknowledgement Type of funding sources: None.

Supplemental Material: Quantitative analysis of hillshed geomorphology and critical zone function: Raising the hillshed to watershed status

Comparison of inverted terrain processing implemented in this study to TopoToolbox results for interfluve (ridge-line) extraction and hierarchical ordering. Different topographic curvature metrics are also explored at varying raster resolutions across hillshed orders.

Supplemental Material: Quantitative analysis of hillshed geomorphology and critical zone function: Raising the hillshed to watershed status

Comparison of inverted terrain processing implemented in this study to TopoToolbox results for interfluve (ridge-line) extraction and hierarchical ordering. Different topographic curvature metrics are also explored at varying raster resolutions across hillshed orders.

Recent Evolution of the Intertidal Sand Ridge Lines of the Dongsha Shoal in the Modern Radial Sand Ridges, East China

The Dongsha Shoal is one of the largest shoals in the South Yellow Sea and has important marine ecological value. The shoal extends in a south–north direction and is controlled by the regional dominating tidal currents. Recently, due to human activities and some natural factors, the geomorphic dynamics of the Dongsha Shoal has undergone drastic changes. However, few people have proposed quantitative research on the changes of tidal flat morphology, let alone the long-term sequence analysis of sand ridge lines. Hence, we attempt to take the Dongsha Shoal in the Radial Sand Ridges as the research area, and analyze the trends of the long-term morphological evolution of the sand ridge lines over the period 1973–2016 based on a high-density time series of medium-resolution satellite images. The sand ridge line generally moves from southeast to northwest, and the position distribution of the sand ridge line from north to south has gradually changed from compact to scattered. We also found that the geomorphological dynamics at different positions of the sand ridge line are inconsistent. The north and south wings are eroded on the west side, while the central area is eroded on the east side. Most of the sand ridge line is moving eastward. In addition, the change of sand ridge line is affected by multiple factors such as sediment supply, typhoon, reclamation and laver cultivation.

On the War-Path for Vicksburg

As the Federals moved from the Big Black River to Vicksburg on May 18, they experienced enormous confidence in Grant’s judgment and skills. Faced with the real prospect that the Confederates might fold if he attacked the defences of Vicksburg quickly, Grant wasted no time in planning an assault for the next day, May 19. But he did not know that Pemberton had positioned fresh troops exactly along the sectors most likely to be attacked. The defences of Vicksburg were by no means formidable in themselves. Constructed over the past few months, they were simply trenches that linked nine major forts and a greater number of smaller artillery positions. In many places, hardly a trench existed. But the most important consideration was that Maj. Samuel H. Lockett, Pemberton’s chief engineer, had placed them well along the only roughly continuous ridge line to be found in the badly eroded, loess soil that dominated the area east of Vicksburg. Confederate soldiers were busy digging in on May 18, strengthening the minimal works Lockett had managed to construct mostly with slave labor before that day. The earthworks were the only thing standing between the victorious Federals and the city.

Detection of degenerate points on the surface

Landslides, bifurcations, multi-saddles and remnants of terraces are distinctive landforms. Some points on the surfaces of these objects are degenerate points. This may help us with their automatic recognition and identification. All first-order and second-order partial derivatives of analyzed function are necessary for detection of degenerate points. Terrain slope, curvatures and Hessian are required for classification of degenerate points. The paper is aimed at detection of fossil landslides. A point of landslide surface where the concave section of thalweg is turning into convex section of ridge line is a degenerate point. Two zero isolines of Hessian and zero isoline of profile, streamline and plan or tangential curvatures pass through this point. Final result of the detection procedure depends to a great extent on the quality of DEM and accuracy of derivatives.

Detection of degenerate points on the surface

Landslides, bifurcations, multi-saddles and remnants of terraces are distinctive landforms. Some points on the surfaces of these objects are degenerate points. This may help us with their automatic recognition and identification. All first-order and second-order partial derivatives of analyzed function are necessary for detection of degenerate points. Terrain slope, curvatures and Hessian are required for classification of degenerate points. The paper is aimed at detection of fossil landslides. A point of landslide surface where the concave section of thalweg is turning into convex section of ridge line is a degenerate point. Two zero isolines of Hessian and zero isoline of profile, streamline and plan or tangential curvatures pass through this point. Final result of the detection procedure depends to a great extent on the quality of DEM and accuracy of derivatives.