Structural Studies of Lanthanide Double Perovskites

This project focuses on the examination of the structures of lanthanide containing double perovskites of the type Ba2LnB'O6-d (Ln = lanthanide or Y3+ and B' = Nb5+, Ta5+, Sb5+ and/or Sn4+) using synchrotron X-ray and neutron powder diffraction. The first part of this project examined the relative stability of R3 rhombohedral and I4/m tetragonal structures as the intermediate phase adopted by the series Ba2LnB'O6 (Ln = lanthanide (III) or Y3+ and B' = Nb5+, Ta5+ or Sb5+). It was found that I4/m tetragonal symmetry was favoured when B' was a transition metal with a small number of d electrons, such as Nb5+ or Ta5+. This is due to the presence of p-bonding in these compounds. In the Ba2LnNbO6 and Ba2LnTaO6 series R3 rhombohedral symmetry was, however, favoured over I4/m tetragonal symmetry when Ln = La3+ or Pr3+ due to the larger ionic radius of these cations. The incompatibility of the d0 and d10 B'-site cations in this family of compounds was indicated by significant regions of phase segregation in the two series Ba2Eu1-xPrxNb1-xSbxO6 and Ba2NdNb1-xSbxO6. In the second part of this project the compounds in the series Ba2LnSnxB'1-xO6-d (Ln = Pr, Nd or Tb and B' = Nb5+ or Sb5+) were examined to understand the relative stability of oxygen vacancies in these materials compared to the oxidation of the lanthanide cations and to determine if any oxygen vacancy ordering occurred. It was found, using a combination of structural characterisation, X ray Absorption Near Edge Structure and Ultra-Violet, Visible and Near Infrared spectroscopies, that with Ln = Pr or Tb increased Sn4+ doping results in a change in the oxidation state of the Ln3+ cations to Ln4+. This leads to those series containing little or no oxygen vacancies. A loss of B site cation ordering was found to accompany this oxidation state change and phase segregation was found to occur in the Ba2PrSnxSb1-xO6-d series most likely due to the Pr3+ and Pr4+ cations segregating into different phases. The Nd3+ cations in the series Ba2NdSnxSb1-xO6-d, however, can not oxidise to the tetravalent state so the number of oxygen vacancies rises with increasing x. It was found that oxygen vacancies concentrate onto the axial site of the compounds with x = 0.6 and 0.8 at ambient temperature. In Ba2Sn0.6Sb0.4O5.7 the oxygen vacancies were found to change to concentrating on the equatorial site at higher temperatures and it is suggested that this oxygen vacancy ordering plays a role in the adoption of I2/m monoclinic symmetry

Prediction of coronary artery disease by a systemic atherosclerosis score index derived from whole-body MR angiography

<p>Abstract</p> <p>Background</p> <p>Whole-body magnetic resonance angiography (WB-MRA) has shown its potential for the non-invasive assessment of nearly the entire arterial vasculature within one examination. Since the presence of extra-cardiac atherosclerosis is associated with an increased risk of coronary events, our goal was to establish the relationship between WB-MRA findings, including a systemic atherosclerosis score index, and the presence of significant coronary artery disease (CAD).</p> <p>Methods</p> <p>WB-MRA was performed on a 1.5T scanner in 50 patients scheduled to undergo elective cardiac catheterization for suspected CAD. In each patient, 40 extra-cardiac vessel segments were evaluated and assigned scores according to their luminal narrowing. The atherosclerosis score index (ASI) was generated as the ratio of summed scores to analyzable segments.</p> <p>Results</p> <p>ASI was higher in patients with significant (> 50% stenosis) CAD (n = 27) vs. patients without CAD (n = 22; 1.56 vs. 1.28, p = 0.004). ASI correlated with PROCAM (R = 0.57, p < 0.001) and Framingham (R = 0.36, p = 0.01) risk scores as estimates of the 10-year risk of coronary events. A ROC derived ASI of > 1.54 predicted significant CAD with a sensitivity of 59%, specificity of 86% and a positive predictive value of 84%. Logistic regression revealed ASI > 1.54 as the strongest independent predictor for CAD with a 11-fold increase in likelihood to suffer from significant coronary disease. On the contrary, while 15/27 (55%) of patients with CAD exhibited at least one extra-cardiac stenosis > 50%, only 3/22 (14%) of those patients without CAD did (p = 0.003). The likelihood for an extra-cardiac stenosis when CAD is present differed between vascular territories and ranged from 15% for a carotid stenosis to 44% for a stenosis in the lower extremities.</p> <p>Conclusion</p> <p>This study provides important new evidence for the close association of extra-cardiac and coronary atherosclerosis. The novel findings that a WB-MRA derived systemic atherosclerosis score index is not only associated with established cardiovascular risk scores but is also predictive of significant CAD suggest its potential prognostic implications and underline the importance to screen for coronary disease in patients with extra-cardiac manifestations of atherosclerosis.</p

NT-proBNP level before primary PCI and risk of poor myocardial reperfusion: Insight from the On-TIME II trial.

Background N-terminal fragment of the brain natriuretic peptide prohormone (NT-proBNP), a marker for neurohumoral activation, has been associated with adverse outcome in patients with myocardial infarction. NT-proBNP levels may reflect extensive ischemia and microvascular damage, therefore we investigated the potential association between baseline NTproBNP level and ST-resolution (STR), a marker of myocardial reperfusion, after primary percutaneous coronary intervention (pPCI).Methods we performed a post-hoc analysis of the On-TIME II trial (which randomized ST-elevation myocardial infarction (STEMI) patients to pre-hospital tirofiban administration vs placebo). Patients with measured NT-proBNP before angiography were included. Multivariate logistic-regression analyses was performed to investigate the association between baseline NTproBNP level and STR one hour after pPCI.Results Out of 984 STEMI patients, 918 (93.3%) had NT-proBNP values at baseline. Patients with STR 70% had higher NT-proBNP values compared to patients with complete STR (70%) [Mean +/- SD 375.2 +/- 1021.7 vs 1007.4 +/- 2842.3, Median (IQR) 111.7 (58.4-280.0) vs 168.0 (62.3-601.3), P < .001]. At multivariate logistic regression analysis, independent predictors associated with higher risk of poor myocardial reperfusion (STR < 70%) were: NT-proBNP (OR 1.17, 95%CI 1.041.31, P = .009), diabetes mellitus (OR 1.87, 95%CI 1.14-3.07, P = .013), anterior infarct location (OR 2.74, 95% CI 2.00-3.77, P < .001), time to intervention (OR 1.06, 95%CI 1.01-1.11, P = .021), randomisation to placebo (OR 1.45, 95%CI 1.05-1.99, P = .022).Conclusions In STEMI patients, higher baseline NT-proBNP level was independently associate with higher risk of poor myocardial reper fusion, suppor ting the potential use of NT-proBNP as an early marker for risk stratification of myocardial reperfusion after pPCI in STEMI patients

Characteristics and outcomes in patients with a prior myocardial infarction treated with extended dual antiplatelet therapy with ticagrelor 60 mg: findings from ALETHEIA, a multi-country observational study

Background Guidelines recommend extended dual antiplatelet therapy, including ticagrelor 60 mg twice daily, in high-risk post-myocardial infarction (MI) patients who have tolerated 12 months and are not at high bleeding risk. The real-world utilization and bleeding and ischaemic outcomes associated with long-term ticagrelor 60 mg in routine clinical practice have not been well described. Methods Register and claims data from the USA (Optum Clinformatics, IBM MarketScan, and Medicare) and Europe (Sweden, Italy, UK, and Germany) were extracted. Patients initiating ticagrelor 60 mg ≥12 months after MI, meeting eligibility criteria for the PEGASUS-TIMI (Prevention of Cardiovascular Events in Patients with Prior Heart Attack Using Ticagrelor Compared to Placebo on a Background of Aspirin – Thrombolysis in Myocardial Infarction 45) 54 trial, were included. The cumulative incidence of the composite of MI, stroke, or all-cause mortality and that of bleeding requiring hospitalization were calculated. Meta-analyses were performed to combine estimates from each source. Results A total of 7035 patients treated with ticagrelor 60 mg met eligibility criteria. Median age was 67 years and 29% were females; 12% had a history of multiple MIs. The majority (95%) had been treated with ticagrelor 90 mg prior to initiating ticagrelor 60 mg. At 12 months from initiation of ticagrelor 60 mg, the cumulative incidence [95% confidence interval (CI)] of MI, stroke, or mortality was 3.33% (2.73–4.04) and was approximately three-fold the risk of bleeding (0.96%; 0.69–1.33). Conclusions This study provides insights into the use of ticagrelor 60 mg in patients with prior MI in clinical practice. Observed event rates for ischaemic events and bleeding generally align with those in the pivotal trials, support the established safety profile of ticagrelor, and highlight the significant residual ischaemic risk in this population

Early diagnosis of acute coronary syndrome.

The diagnostic evaluation of acute chest pain has been augmented in recent years by advances in the sensitivity and precision of cardiac troponin assays, new biomarkers, improvements in imaging modalities, and release of new clinical decision algorithms. This progress has enabled physicians to diagnose or rule-out acute myocardial infarction earlier after the initial patient presentation, usually in emergency department settings, which may facilitate prompt initiation of evidence-based treatments, investigation of alternative diagnoses for chest pain, or discharge, and permit better utilization of healthcare resources. A non-trivial proportion of patients fall in an indeterminate category according to rule-out algorithms, and minimal evidence-based guidance exists for the optimal evaluation, monitoring, and treatment of these patients. The Cardiovascular Round Table of the ESC proposes approaches for the optimal application of early strategies in clinical practice to improve patient care following the review of recent advances in the early diagnosis of acute coronary syndrome. The following specific 'indeterminate' patient categories were considered: (i) patients with symptoms and high-sensitivity cardiac troponin 99th percentile but without dynamic change; and (iv) patients with symptoms and high-sensitivity troponin >99th percentile and dynamic change but without coronary plaque rupture/erosion/dissection. Definitive evidence is currently lacking to manage these patients whose early diagnosis is 'indeterminate' and these areas of uncertainty should be assigned a high priority for research

Objectively measured physical activity and cardiac biomarkers: A cross sectional population based study in older men.

BACKGROUND: N-terminal pro-brain natriuretic peptide (NT-proBNP) and high sensitivity Troponin T (hsTnT) are markers of cardiac injury used in diagnosis of heart failure and myocardial infarction respectively, and associated with increased risk of cardiovascular disease. Since physical activity is protective against cardiovascular disease and heart failure, we investigated whether higher levels of physical activity, and less sedentary behaviour were associated with lower NT-proBNP and hsTnT. METHODS AND RESULTS: Cross sectional study of 1130 men, age 70-91years, from the British Regional Heart Study, measured in 2010-2012. Fasting blood samples were analysed for NT-proBNP and hsTnT. Physical activity and sedentary behaviour were measured using ActiGraph GT3X accelerometers. Relationships between activity and NT-proBNP or hsTnT were non-linear; biomarker levels were lower with higher total activity, steps, moderate/vigorous activity and light activity only at low to moderate levels of activity. For example, for each additional 10min of moderate/vigorous activity, NT-proBNP was lower by 35.7% (95% CI -47.9, -23.6) and hsTnT by 8.4% (95% CI -11.1, -5.6), in men who undertook <25 or 50min of moderate/vigorous activity per day respectively. Biomarker levels increased linearly with increasing sedentary behaviour, but not independently of moderate/vigorous activity. CONCLUSION: Associations between biomarkers and moderate/vigorous activity (and between hsTnT and light activity) were independent of sedentary behaviour, suggesting activity is driving the relationships. In these older men with concomitantly low levels of physical activity, activity may be more important in protecting against cardiac health deterioration in less active individuals, although reverse causality might be operating