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Accurate modelling of ash clouds from volcanic eruptions requires knowledge about the eruption source parameters including eruption onset, duration, mass eruption rates, particle size distribution, and vertical emission profiles. However, most of these parameters are unknown and must be estimated somehow. Some are estimated based on observed correlations and known volcano parameters. However, a more accurate estimate is often needed to bring the model into closer agreement to observations. This paper describes the inversion procedure implemented at the Norwegian Meteorological Institute for estimating ash emission rates from retrieved satellite ash column amounts and a priori knowledge. The overall procedure consists of five stages: (1) generate a priori emission estimates; (2) run forward simulations with a set of unit emission profiles; (3) collocate/match observations with emission simulations; (4) build system of linear equations; and (5) solve overdetermined system. We go through the mathematical foundations for the inversion procedure, performance for synthetic cases, and performance for real-world cases. The novelties of this paper includes a memory efficient formulation of the inversion problem, a detailed description and illustrations of the mathematical formulations, evaluation of the inversion method using synthetic known truth data as well as real data, and inclusion of observations of ash cloud-top height. The source code used in this work is freely available under an open source license, and is possible to use for other similar applications.

Volcanic eruptions can emit large quantities of sulphur dioxide (SO2) into the atmosphere, which can be harmful to people and the environment. Aircraft encounters with a volcanic SO2 cloud could represent a health hazard to crew and passengers onboard, depending on the dose of SO2 encountered. The recommended SO2 concentration threshold set by the World Health Organisation (WHO) is 500 µg/m3 over 10 minutes. In this study we have assessed concentration levels of volcanic SO2 in the atmosphere following eight historic eruptions and use dispersion model simulations to calculate when and where the WHO threshold is exceeded. The time and area of exceedance varies and depends on the eruption characteristics: the amount, duration and height of the SO2 release. The WHO threshold is exceeded for all historic eruptions considered. In several cases, the area delineated by the WHO threshold, that is the SO2 hazard, can be considerably larger than the volcanic ash hazard area for the same eruption. SO2 hazard areas also often extend over a longer period of time compared to the equivalent ash advisories. For example, following the 2019 eruption of Raikoke, the SO2 hazard area reached up to 1.7 million km2 and the WHO concentration value was exceeded for about two weeks, while volcanic ash was considered hazardous to aviation for about five days. These results will help the aviation industry to better understand the potential risks to their passengers and crew from volcanic SO2, and aid in defining concentration thresholds for any potential volcanic SO2 forecasts for aviation.

INTRODUCTION: MARVEL 2 assessed the efficacy of mechanical atrial sensing by a ventricular leadless pacemaker, enabling a VDD pacing mode. The behavior of the enhanced MARVEL 2 algorithm during variable atrio-ventricular conduction (AVC) and/or arrhythmias has not been characterized and is the focus of this study. METHODS: Of the 75 patients enrolled in the MARVEL 2 study, 73 had a rhythm assessment and were included in the analysis. The enhanced MARVEL 2 algorithm included a mode-switching algorithm that automatically switches between VDD and ventricular only antibradycardia pacing (VVI)-40 depending upon AVC status. RESULTS: Forty-two patients (58%) had persistent third degree AV block (AVB), 18 (25%) had 1:1 AVC, 5 (7%) had variable AVC status, and 8 (11%) had atrial arrhythmias. Among the 42 patients with persistent third degree AVB, the median ventricular pacing (VP) percentage was 99.9% compared to 0.2% among those with 1:1 AVC. As AVC status changed, the algorithm switched to VDD when the ventricular rate dropped less than 40 bpm. During atrial fibrillation (AF) with ventricular response greater than 40 bpm, VVI-40 mode was maintained. No pauses longer than 1500 ms were observed. Frequent ventricular premature beats reduced the percentage of AV synchrony. During AF, the atrial signal was of low amplitude and there was infrequent sensing. CONCLUSION: The mode switching algorithm reduced VP in patients with 1:1 AVC and appropriately switched to VDD during AV block. No pacing safety issues were observed during arrhythmias. ispartof: JOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY vol:32 issue:7 pages:1947-1957 ispartof: location:United States status: published

Predictors of Response to Cardiac Resynchronization Therapy (CRT) (PROSPECT) was the first large-scale, multicentre clinical trial that evaluated the ability of several echocardiographic measures of mechanical dyssynchrony to predict response to CRT. Since response to CRT may be defined as a spectrum and likely influenced by many factors, this sub-analysis aimed to investigate the relationship between baseline characteristics and measures of response to CRT.A total of 286 patients were grouped according to relative reduction in left ventricular end-systolic volume (LVESV) after 6 months of CRT: super-responders (reduction in LVESVor =30%), responders (reduction in LVESV 15-29%), non-responders (reduction in LVESV 0-14%), and negative responders (increase in LVESV). In addition, three subgroups were formed according to clinical and/or echocardiographic response: +/+ responders (clinical improvement and a reduction in LVESVor =15%), +/- responders (clinical improvement or a reduction in LVESVor =15%), and -/- responders (no clinical improvement and no reduction in LVESVor =15%). Differences in clinical and echocardiographic baseline characteristics between these subgroups were analysed. Super-responders were more frequently females, had non-ischaemic heart failure (HF), and had a wider QRS complex and more extensive mechanical dyssynchrony at baseline. Conversely, negative responders were more frequently in New York Heart Association class IV and had a history of ventricular tachycardia (VT). Combined positive responders after CRT (+/+ responders) had more non-ischaemic aetiology, more extensive mechanical dyssynchrony at baseline, and no history of VT.Sub-analysis of data from PROSPECT showed that gender, aetiology of HF, QRS duration, severity of HF, a history of VT, and the presence of baseline mechanical dyssynchrony influence clinical and/or LV reverse remodelling after CRT. Although integration of information about these characteristics would improve patient selection and counselling for CRT, further randomized controlled trials are necessary prior to changing the current guidelines regarding patient selection for CRT.

Background— Recently, magnetic resonance (MR)–conditional implantable cardioverter defibrillator (ICD) systems have become available. However, associated cardiac MR image (MRI) quality is unknown. The goal was to evaluate the image quality performance of various cardiac MR sequences in a multicenter trial of patients implanted with an MR-conditional ICD system. Methods and Results— The Evera-MRI trial enrolled 275 patients in 42 centers worldwide. There were 263 patients implanted with an Evera-MRI single- or dual-chamber ICD and randomized to controls (n=88) and MRI (n=175), 156 of whom underwent a protocol-required MRI (9–12 weeks post implant). Steady-state-free-precession (SSFP) and fast-gradient-echo (FGE) sequences were acquired in short-axis and horizontal long-axis orientations. Qualitative and quantitative assessment of image quality was performed by using a 7-point scale (grades 1–3: good quality, grades 6–7: nondiagnostic) and measuring ICD- and lead-related artifact size. Good to moderate image quality (grades 1–5) was obtained in 53% and 74% of SSFP and FGE acquisitions, respectively, covering the left ventricle, and in 69% and 84%, respectively, covering the right ventricle. Odds for better image quality were greater for right ventricle versus left ventricle (odds ratio, 1.8; 95% confidence interval, 1.5–2.2; P P P P Conclusions— FGE yields good to moderate quality in 74% of left ventricle and 84% of right ventricle acquisitions and performs better than SSFP in patients with an MRI-conditional ICD system. In these patients, cardiac MRI can offer diagnostic information in most cases. Clinical Trial Registration— URL: http://www.clinicaltrials.gov . Unique identifier: NCT02117414.

Aims Unwanted phrenic nerve stimulation (PNS) has been reported in ∼1 in 4 patients undergoing left ventricular (LV) pacing. The occurrence of PNS over mid-term follow-up and the significance of PNS are less certain. Methods and results Data from 1307 patients enrolled in pre-market studies of LV leads manufactured by Medtronic (models 4193 and 4195 unipolar, 4194, 4196, 4296, and 4396 bipolar) were pooled. Left ventricular lead location was recorded at implant using a common classification scheme. Phrenic nerve stimulation symptoms were either spontaneously reported or identified at scheduled follow-up visits. A PNS-related complication was defined as PNS resulting in invasive intervention or the termination of LV pacing. Average follow-up was 14.9 months (range 0.0–46.6). Phrenic nerve stimulation symptoms occurred in 169 patients (12.9%). Phrenic nerve stimulation-related complications occurred in 21 of 1307 patients (1.6%); 16 of 738 (2.2%) in the unipolar lead studies, and 5 of 569 (0.9%) in the bipolar lead studies ( P = 0.08). Phrenic nerve stimulation was more frequent at middle–lateral/posterior, and apical LV sites (139/1010) vs. basal–posterior/lateral/anterior, and middle–anterior sites (20/297; P = 0.01). As compared with an anterior LV lead position, a lateral LV pacing site was associated with over a four-fold higher risk of PNS ( P = 0.005) and an apical LV pacing site was associated with over six-fold higher risk of PNS ( P = 0.001). Conclusion Phrenic nerve stimulation occurred in 13% of patients undergoing LV lead placement and was more common at mid-lateral/posterior, and LV apical sites. Most cases (123/139; 88%) of PNS were mitigated via electrical reprogramming, without the need for invasive intervention.

This paper is the fifth in a series dealing with reference procedures for the measurement of catalytic activity concentrations of enzymes at 37 degrees C and the certification of reference preparations. Other parts deal with: Part 1. The Concept of Reference Procedures for the Measurement of Catalytic Activity Concentrations of Enzymes; Part 2. Reference Procedure for the Measurement of Catalytic Concentration of Creatine Kinase; Part 3. Reference Procedure for the Measurement of Catalytic Concentration of Lactate Dehydrogenase; Part 4. Reference Procedure for the Measurement of Catalytic Concentration of Alanine Aminotransferase; Part 6. Reference Procedure for the Measurement of Catalytic Concentration of Gamma-Glutamyltransferase; Part 7. Certification of Four Reference Materials for the Determination of Enzymatic Activity of Gamma-Glutamyltransferase, Lactate Dehydrogenase, Alanine Aminotransferase and Creatine Kinase at 37 degrees C. A document describing the determination of preliminary upper reference limits is also in preparation. The procedure described here is deduced from the previously described 30 degrees C IFCC reference method. Differences are tabulated and commented on in Appendix 3.

This paper is the fourth in a series dealing with reference procedures for the measurement of catalytic activity concentrations of enzymes at 37 degrees C and the certification of reference preparations. Other parts deal with: Part 1. The Concept of Reference Procedures for the Measurement of Catalytic Activity Concentrations of Enzymes; Part 2. Reference Procedure for the Measurement of Catalytic Concentration of Creatine Kinase; Part 3. Reference Procedure for the Measurement of Catalytic Concentration of Lactate Dehydrogenase; Part 5. Reference Procedure for the Measurement of Catalytic Concentration of Aspartate Aminotransferase; Part 6. Reference Procedure for the Measurement of Catalytic Concentration of Gamma-Glutamyltransferase; Part 7. Certification of Four Reference Materials for the Determination of Enzymatic Activity of Gamma-Glutamyltransferase, Lactate Dehydrogenase, Alanine Aminotransferase and Creatine Kinase at 37 degrees C. A document describing the determination of preliminary upper reference limits is also in preparation. The procedure described here is deduced from the previously described 30 degrees C IFCC reference method. Differences are tabulated and commented on in Appendix 2.

This paper is the seventh in a series dealing with reference procedures for the measurement of catalytic activity concentrations of enzymes at 37 degrees C and the certification of reference preparations. Other parts deal with: Part 1. The Concept of Reference Procedures for the Measurement of Catalytic Activity Concentrations of Enzymes; Part 2. Reference Procedure for the Measurement of Catalytic Concentration of Creatine Kinase; Part 3. Reference Procedure for the Measurement of Catalytic Concentration of Lactate Dehydrogenase; Part 4. Reference Procedure for the Measurement of Catalytic Concentration of Alanine Aminotransferase; Part 5. Reference Procedure for the Measurement of Catalytic Concentration of Aspartate Aminotransferase; Part 6. Reference Procedure for the Measurement of Catalytic Concentration of Gamma-Glutamyltransferase. A document describing the determination of preliminary reference values is also in preparation. The certification of the catalytic activity concentrations as determined by the recently elaborated IFCC primary reference methods at 37 degrees C of four enzyme preparations, namely IRMM/IFCC 452 (gamma-glutamyltransferase), IRMM/IFCC 453 (lactate dehydrogenase 1), IRMM/IFCC 454 (alanine aminotransferase) and IRMM/IFCC 455 (creatine kinase) is described. Homogeneity data were derived from previous results. Stability was assessed using recently obtained data as well as data from previous stability studies. The collaborative study for value assignment was performed under a strict quality control scheme to ensure traceability to the primary reference method. Uncertainty of the materials was assessed in compliance with the Guide to the Expression of Uncertainty in Measurement. The certified values obtained at 37 degrees C are 1.90 microkat/l +/- 0.04 microkat/l (114.1 U/l +/- 2.4 U/l), for gamma-glutamyltransferase, 8.37 microkat/l +/- 0.12 microkat/l (502 U/l +/- 7 U/l), for lactate dehydrogenase 1, 3.09 microkat/l +/- 0.07 microkat/l (186 U/l +/- 4 U/l), for alanine aminotransferase and 1.68 microkat/l +/- 0.07 microkat/l (101 U/l +/- 4 U/l), for creatine kinase. The materials are intended for internal quality control as well as for the evaluation of test systems as required by recent European Union legislation. Furthermore, the materials can be used to transfer accuracy from a reference method to a routine procedure provided the procedures exhibit the same analytical specificity and the certified materials are commutable.