FIELD ION EMISSION FROM LIQUID SOLUTIONS : ION EVAPORATION AGAINST ELECTROHYDRODYNAMIC DISINTEGRATION

In several ionization techniques currently applied in organic mass spectrometry a mechanism of field induced ion evaporation from charged droplets is assumed to play a dominant role in the desolvation of ions from liquids. This ion evaporation mechanism is briefly discussed regarding its competition with electrohydrodynamic disintegration of the surface of the liquid droplet under field stress. It is shown that ion evaporation is unlikely to occur for most solute/solvent systems and of no significance in the formation of gaseous ions. In contrast electro-hydrodynamic disintegration processes can contribute to the desolvation of ions from charged droplets

COMPARISON OF BARE WIRES AND ACTIVATED EMITTERS FOR FD MS OF OLIGOSACCHARIDES

Ion formation in field desorption (FD) from activated wire emitters covered with field enhancing microneedles has been compared with that from bare wires for some oligosaccharides doped with NaCl. The experiment revealed a close similarity between both types of emitters in the ion formation by electrohydrodynamic disintegration processes at temperatures near the onset of ion emission. In contrast, at higher temperatures above the melting point the sample layers are removed from smooth wires while on activated emitters they are retained in part between the microneedles. In this temperature range surface mobile molecules were found to be ionized not only by FI processes on microneedle tips but also by alkali ion attachment on charged alkali ion donating solid deposits. The latter mechanism has not been considered in FD mass spectrometry yet

ENHANCED FORMATION OF MULTIPLY CHARGED IONS IN NEGATIVE ION FIELD DESORPTION MASS SPECTROMETRY OF ORGANIC COMPOUNDS

Enhanced formation of doubly and triply charged negative ions has been obtained in negative ion field desorption mass spectrometry (NFD MS) of acids and salts by applying a matrix mixture of polyvinyl pyrrolidone (PVP) and polyethylene glycol (PEG). Abundant doubly charged ions of disaccharides could be obtained from a mixture with a quaternary ammonium salt and sodium chloride. The matrix properties leading to the formation of multiply charged ions are discussed

TEMPERATURE EFFECTS IN MATRIX ASSISTED FIELD DESORPTION MASS SPECTROMETRY

Matrix techniques are frequently applied in field desorption mass spectrometry (FD MS) to facilitate the desolvation of molecular ions and to reduce the thermal stress on molecules. For some oligosaccharides mixed with NaI and tartaric acid and for various mixtures of sucrose the onset temperature of molecular ion emission, which is close to the best emitter temperature for taking mass spectra, was determined. The onset temperatures are typically significantly below the melting point of the solvent- and matrix-free sample. Using the same mixtures the onset temperatures for positive ions were found to be slightly lower than for negative ions. The ion emission temperature is reduced by the application of a polymer matrix and by the admixture of an appropriate surface-active compound but is raised by the use of high salt concentrations. The effect is greater with LiCl than with NaI

Minimally invasive approach compared to resternotomy for mitral valve surgery in patients with prior cardiac surgery: retrospective multicentre study based on the Netherlands Heart Registration

OBJECTIVES: Mitral valve (MV) surgery after prior cardiac surgery is conventionally performed through resternotomy and associated with increased morbidity and mortality. Alternatively, MV can be approached minimally invasively [minimally invasive mitral valve surgery (MIMVS)], but longer-term follow-up of this approach for MV surgery after prior cardiac surgery is lacking. Therefore, the aim of the current study is to evaluate short- and mid-term outcomes of MIMVS versus MV surgery through resternotomy in patients with prior sternotomy, using a nationwide registry. METHODS: Patients undergoing isolated MV surgery after prior cardiac surgery between 2013 and 2018 were included. Primary outcomes were short-term morbidity and mortality and mid-term survival. Cox proportional hazard analysis was used to investigate the association between surgical approach and mortality. Propensity score matching was used to correct for potential confounders. RESULTS: In total, 290 patients underwent MV surgery after prior cardiac surgery, of whom 205 patients were operated through resternotomy and 85 patients through MIMVS. No significant differences in 30-day mortality (3.4% vs 2%, P = 0.99) were observed between both groups. Five-year survival was 86.3% in the resternotomy group, compared to 89.4% in the MIMVS group (log-rank P = 0.45). In the multivariable analysis, surgical approach showed no relation with mid-term mortality [hazard ratio 0.73 (0.34-1.60); P = 0.44]. A lower incidence of prolonged intubation and new-onset arrhythmia was observed in MIMVS. CONCLUSIONS: MV surgery after prior cardiac surgery has excellent short- and mid-term results in the Netherlands, and MIMVS and resternotomy appear to be equally efficacious. MIMVS is associated with a lower incidence of new-onset arrhythmia and prolonged intubation

Effect of minimally invasive mitral valve surgery compared to sternotomy on short- and long-term outcomes: a retrospective multicentre interventional cohort study based on Netherlands Heart Registration

OBJECTIVES: Minimally invasive mitral valve surgery (MIMVS) has been performed increasingly for the past 2 decades; however, large comparative studies on short- and long-term outcomes have been lacking. This study aims to compare short- and long-term outcomes of patients undergoing MIMVS versus median sternotomy (MST) based on real-world data, extracted from the Netherlands Heart Registration. METHODS: Patients undergoing mitral valve surgery, with or without tricuspid valve, atrial septal closure and/or rhythm surgery between 2013 and 2018 were included. Primary outcomes were short-term morbidity and mortality and long-term survival. Propensity score matching analyses were performed. RESULTS: In total, 2501 patients were included, 1776 were operated through MST and 725 using an MIMVS approach. After propensity matching, no significant differences in baseline characteristics persisted. There were no between-group differences in 30-day mortality (1.1% vs 0.7%, P = 0.58), 1-year mortality (2.6% vs 2.1%, P = 0.60) or perioperative stroke rate (1.1% vs 0.6%, P = 0.25) between MST and MIMVS, respectively. An increased rate of postoperative arrhythmia was observed in the MST group (31.3% vs 22.4%, P < 0.001). A higher repair rate was found in the MST group (80.9% vs 76.3%, P = 0.04). No difference in 5-year survival was found between the matched groups (95.0% vs 94.3%, P = 0.49). Freedom from mitral reintervention was 97.9% for MST and 96.8% in the MIMVS group (P = 0.01), without a difference in reintervention-free survival (P = 0.30). CONCLUSIONS: The MIMVS approach is as safe as the sternotomy approach for the surgical treatment of mitral valve disease. However, it comes at a cost of a reduced repair rate and more reinterventions in the long term, in the real-world

Minimally invasive approach compared to resternotomy for mitral valve surgery in patients with prior cardiac surgery: retrospective multicentre study based on the Netherlands Heart Registration

OBJECTIVES: Mitral valve (MV) surgery after prior cardiac surgery is conventionally performed through resternotomy and associated with increased morbidity and mortality. Alternatively, MV can be approached minimally invasively [minimally invasive mitral valve surgery (MIMVS)], but longer-term follow-up of this approach for MV surgery after prior cardiac surgery is lacking. Therefore, the aim of the current study is to evaluate short- and mid-term outcomes of MIMVS versus MV surgery through resternotomy in patients with prior sternotomy, using a nationwide registry. METHODS: Patients undergoing isolated MV surgery after prior cardiac surgery between 2013 and 2018 were included. Primary outcomes were short-term morbidity and mortality and mid-term survival. Cox proportional hazard analysis was used to investigate the association between surgical approach and mortality. Propensity score matching was used to correct for potential confounders. RESULTS: In total, 290 patients underwent MV surgery after prior cardiac surgery, of whom 205 patients were operated through resternotomy and 85 patients through MIMVS. No significant differences in 30-day mortality (3.4% vs 2%, P = 0.99) were observed between both groups. Five-year survival was 86.3% in the resternotomy group, compared to 89.4% in the MIMVS group (log-rank P = 0.45). In the multivariable analysis, surgical approach showed no relation with mid-term mortality [hazard ratio 0.73 (0.34-1.60); P = 0.44]. A lower incidence of prolonged intubation and new-onset arrhythmia was observed in MIMVS. CONCLUSIONS: MV surgery after prior cardiac surgery has excellent short- and mid-term results in the Netherlands, and MIMVS and resternotomy appear to be equally efficacious. MIMVS is associated with a lower incidence of new-onset arrhythmia and prolonged intubation

Impact of the coronavirus disease 2019 pandemic on volume of thoracic aortic surgery on a national level

OBJECTIVES: The aim of this study was to evaluate the effects of the coronavirus 2019 pandemic on elective and acute thoracic aortic surgery in the Netherlands. METHODS: The Netherlands Heart Registration database was used to compare the volume of elective and acute surgery on the thoracic aorta in 2019 and 2020, starting from week 11 in both years. A sub-analysis was done to assess the impact of the pandemic on high-volume and low-volume aortic centres. RESULTS: During the pandemic, the number of elective thoracic aortic operations declined by 18% [incidence rate ratio (IRR) 0.82 [0.73-0.91]; P < 0.01]. The decline in volume of elective surgery was significant in both high-volume (IRR 0.82 [0.71-0.94]; P < 0.01) and low-volume aortic centres (IRR 0.81 [0.68-0.98]; P = 0.03). The overall number of acute aortic operations during the pandemic remained similar to that in 2019 (505 vs 499; P = 0.85), but an increased share of these operations occurred at high-volume centres. The number of acute operations performed in high-volume centres increased by 20% (IRR 1.20 [1.01-1.42]; P = 0.04), while the number of acute operations performed in low-volume centres decreased by 17% (IRR 0.83 [0.69-1.00]; P = 0.04). CONCLUSIONS: The coronavirus 2019 pandemic led to a significant decrease in elective thoracic aortic surgery but did not cause a change in the volume of acute thoracic aortic surgery in the Netherlands. Moreover, the pandemic led to a centralization of care for acute thoracic aortic surgery

Impact of the coronavirus disease 2019 pandemic on volume of thoracic aortic surgery on a national level

OBJECTIVES: The aim of this study was to evaluate the effects of the coronavirus 2019 pandemic on elective and acute thoracic aortic surgery in the Netherlands. METHODS: The Netherlands Heart Registration database was used to compare the volume of elective and acute surgery on the thoracic aorta in 2019 and 2020, starting from week 11 in both years. A sub-analysis was done to assess the impact of the pandemic on high-volume and low-volume aortic centres. RESULTS: During the pandemic, the number of elective thoracic aortic operations declined by 18% [incidence rate ratio (IRR) 0.82 [0.73-0.91]; P < 0.01]. The decline in volume of elective surgery was significant in both high-volume (IRR 0.82 [0.71-0.94]; P < 0.01) and low-volume aortic centres (IRR 0.81 [0.68-0.98]; P = 0.03). The overall number of acute aortic operations during the pandemic remained similar to that in 2019 (505 vs 499; P = 0.85), but an increased share of these operations occurred at high-volume centres. The number of acute operations performed in high-volume centres increased by 20% (IRR 1.20 [1.01-1.42]; P = 0.04), while the number of acute operations performed in low-volume centres decreased by 17% (IRR 0.83 [0.69-1.00]; P = 0.04). CONCLUSIONS: The coronavirus 2019 pandemic led to a significant decrease in elective thoracic aortic surgery but did not cause a change in the volume of acute thoracic aortic surgery in the Netherlands. Moreover, the pandemic led to a centralization of care for acute thoracic aortic surgery