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Effect of race on pressure recovery adjustment for prevention of aortic stenosis grading discordance;
(BMJ Group, 2023-05-05)
Objective We sought to evaluate the potential impact of racial difference (Asians vs Caucasians) on the clinical usefulness of pressure recovery (PR) adjustment for preventing discordant aortic stenosis (AS) grading in patients with severe AS. Methods Data from 1450 patients (mean age, 70.2±10.6 years; 290 (20%) Caucasians; aortic valve area (AVA), 0.77±0.26 cm2) were retrospectively analysed. PR-adjusted AVA was calculated using a validated equation. Discordant grading of severe AS was defined as AVA of <1.0 cm2 and mean gradient of <40 mm Hg. The frequency of discordant grading was assessed in the overall cohort and the propensity scorematched cohort. Results Before PR adjustment, 1186 patients showed AVA values of <1.0 cm2 ; after PR adjustment, 170 (14.3%) were reclassified as having moderate AS. PR adjustment decreased the frequency of discordant grading from 31.4% to 14.1% in Caucasians and from 13.8% to 7.9% in Asians. Patients with reclassification to moderate AS after PR adjustment had a significantly lower risk of a composite of aortic valve replacement or all-cause death than did those with severe AS after PR adjustment (HR 0.38; 95% CI 0.31–0.46; p<0.001). In propensity score-matched cohorts (173 pairs), the frequency of discordant grading before PR adjustment was 42.2% and 43.9% in the Caucasian and Asian patients, respectively, which decreased to 21.4% and 20.2%, respectively, after PR adjustment.Conclusions Clinically relevant PR occurred, regardless of race in patients with moderate to severe AS. Routine PR adjustment may be useful for reconciling discordant AS grading.
Long-term, high-resolution permafrost monitoring reveals coupled energy balance and hydrogeologic controls on talik dynamics near umiujaq (Nunavik, Québec, Canada)
(American Geophysical Union, 2023-01-17)
Rising temperatures in the Arctic and subarctic are driving the rapid thaw of permafrost by reducing permafrost cooling, increasing active layer thickness, and promoting talik formation. In this study, the cyrohydrogeology of a permafrost mound located within the discontinuous permafrost zone near Umiujaq (Nunavik, Québec, Canada) is characterized through the analysis of a dataset covering more than two decades of monitoring. This dataset captures a high degree of interannual variability in air temperature and ground thermal conditions, as well as the formation and closure of a supra-permafrost talik. Data indicate that variable saturation and advective heat transport directly contribute to the expansion and contraction of the talik. Data further indicate the presence of two distinct thermo-hydrologic settings resulting from differences in surface conditions, as well as subsurface thermal and flow regimes. The first, found at the top of the mound feature, is characterized by very low moisture contents (<0.05 m3/m3), while the second, found at the side of the mound feature, shows higher annual moisture contents that strongly influence the dynamics of heat and groundwater flow. The data were synthesized into a detailed conceptual model of the cyrohydrogeological dynamics that highlights the important role of hydrogeological characterization and long-term data sets in understanding the effects of groundwater flow on seasonal frost and permafrost dynamics. Specifically, the results presented here show that in the absence of long-term data sets, longer-period transient phenomena such as talik opening and closure may be misrepresented as uni-directional feedback loops, as opposed to highly dynamic temporary phenomena.