Evaluation of parameter and model uncertainty in simple applications of a 1D sediment transport model

2011 Fall.Includes bibliographical references.This paper aims to quantify parameter and model uncertainty in simulations from a 1D sediment transport model using two methods from Bayesian statistics. The first method, Multi-Variable Shuffled Complex Evolution Metropolis - Uncertainty Analysis (MSU), is an algorithm that identifies the most likely parameter values and estimates parameter uncertainty for models with multiple outputs. The other method, Bayesian Model Averaging (BMA), determines a combined prediction based on three sediment transport equations and evaluates the uncertainty associated with the selection of a transport equation. These tools are applied to simulations of three flume experiments. Results show that MSU's ability to consider correlation between parameters improves its estimate of the uncertainty in the model forecasts. Also, BMA results suggest that a combination of transport equations usually provides a better forecast than an individual equation, and the selection of a single transport equation substantially increases the overall uncertainty in the model forecasts

A retrospective observational study to determine baseline characteristics and early prescribing patterns for patients receiving Alirocumab in UK clinical practice

Background Alirocumab is a fully human monoclonal antibody to proprotein convertase subtilisin/kexin type 9 (PCSK9) and has been previously shown, in the phase III ODYSSEY clinical trial program, to provide significant lowering of lowdensity lipoprotein cholesterol (LDL-C) and reduction in risk of major adverse cardiovascular events. However, real-world evidence to date is limited. Objective The primary objective was to describe baseline characteristics, clinical history, and prior lipid-lowering therapy (LLT) use of patients initiated on alirocumab in UK clinical practice following publication of health technology appraisal (HTA) body recommendations. Secondary objectives included description of alirocumab use and lipid parameter outcomes over a 4-month follow-up period. Methods In this retrospective, single-arm, observational, multicenter study, data were collected for 150 patients initiated on alirocumab. Results Mean (standard deviation; SD) age of patients was 61.4 (10.5) years and baseline median (interquartile range; IQR) LDL-C level was 4.8 (4.2–5.8) mmol/l. Alirocumab use occurred predominantly in patients with heterozygous familial hypercholesterolemia (HeFH) (n = 100/150, 66%) and those with statin intolerance (n = 123/150, 82%). Most patients started on alirocumab 75 mg (n = 108/150 [72%]) and 35 (23.3%) were up-titrated to 150 mg. Clinically significant reductions in atherogenic lipid parameters were observed with alirocumab, including LDL-C (median [IQR] change from baseline, − 53.6% [− 62.9 to − 34.9], P < 0.001). Conclusion This study highlights the unmet need for additional LLT in patients with uncontrolled hyperlipidemia and demonstrates the clinical utility of alirocumab in early real-world practice, where dosing flexibility is an important attribute of this therapeutic option

Osteoprotegerin and cardiovascular mortality in patients with non-ST elevation acute coronary syndromes

Objective: To assess the relationship between osteoprotegerin (OPG) and cardiovascular death, and the pathobiological mechanisms contributing to the association, in acute coronary syndromes (ACS). Design: Prospective observational. Setting: Biomarker substudy of MERLIN-TIMI 36, a randomised, placebo controlled trial of ranolazine in non-ST elevation (NSTE)-ACS. Patients: 4463 patients with NSTE-ACS. Interventions: Ranolazine or placebo. Main outcome measures: Incidence of cardiovascular death (CV death); additionally, heart failure (HF), cardiac arrhythmias, inhospital ischaemia, severe recurrent ischaemia or recurrent myocardial infarction (MI). Results: During a median follow-up of 341 days, 208 patients died of cardiovascular causes. The OPG baseline concentration was strongly associated with both 30 day and 1 year incidence of CV death. After adjustment for conventional risk markers, OPG concentrations (log transformed) remained a significant predictor of CV death by 30 days (HR (95% CI) 2.32 (1.30 to 4.17); p¼0.005) and by 1 year (HR 1.85 (1.33 to 2.59); p<0.001). Baseline levels of OPG were also an independent predictor of new or worsening HF at 30 days (HR 2.25 (1.38 to 3.69); p¼0.001) and 1 year (HR 1.81 (1.26 to 2.58) p¼0.001). By univariable analysis, higher OPG was associated with both early ischaemic and arrhythmic events. Although OPG levels were associated with recurrent MI within 12 months, this association was attenuated and no longer significant after multivariable adjustment. Conclusions: OPG is independently associated with 30 day and 1 year risk of cardiovascular mortality and HF development after NSTE-ACS. As no independent relationship between OPG levels and recurrent ischaemia or MI was observed, myocardial dysfunction may be a more important stimulus for OPG production than ischaemia in ACS

Gut microbiota‐dependent trimethylamine N‐oxide and cardiovascular outcomes in patients with prior myocardial infarction: A nested case control study from the PEGASUS‐TIMI 54 trial

Background Trimethylamine N‐oxide (TMAO) may have prothrombotic properties. We examined the association of TMAO quartiles with major adverse cardiovascular events (MACE) and the effect of TMAO on the efficacy of ticagrelor. Methods and Results PEGASUS‐TIMI 54 (Prevention of Cardiovascular Events in Patients With Prior Heart Attack Using Ticagrelor Compared to Placebo on a Background of Aspirin ‐ Thrombolysis in Myocardial Infarction 54) randomized patients with prior myocardial infarction to ticagrelor or placebo (median follow‐up 33 months). Baseline plasma concentrations of TMAO were measured in a nested case‐control study of 597 cases with cardiovascular death, myocardial infarction, or stroke (MACE) and 1206 controls matched for age, sex, and estimated glomerular filtration rate [eGFR]. Odds ratios (OR) were used for the association between TMAO quartiles and MACE, adjusting for baseline clinical characteristics (age, sex, eGFR, region, body mass index, hypertension, hypercholesterolemia, diabetes mellitus, smoking, peripheral artery disease, index event, aspirin dosage and treatment arm), and cardiovascular biomarkers (hs‐TnT [high‐sensitivity troponin T], hs‐CRP [high‐sensitivity C‐reactive protein], NT‐proBNP [N‐terminal‐pro‐B‐type natriuretic peptide]). Higher TMAO quartiles were associated with risk of MACE (OR for quartile 4 versus quartile 1, 1.43, 95% CI, 1.06–1.93, P trend=0.015). The association was driven by cardiovascular death (OR 2.25, 95% CI, 1.28–3.96, P trend=0.003) and stroke (OR 2.68, 95% CI, 1.39–5.17, P trend<0.001). After adjustment for clinical factors, the association persisted for cardiovascular death (ORadj 1.89, 95% CI, 1.03–3.45, P trend=0.027) and stroke (ORadj 2.01, 95% CI, 1.01–4.01, P trend=0.022), but was slightly attenuated after adjustment for cardiovascular biomarkers (cardiovascular death: ORadj 1.74, 95% CI, 0.88–3.45, P trend=0.079; and stroke: ORadj 1.82, 95% CI, 0.88–3.78, P trend=0.056). The reduction in MACE with ticagrelor was consistent across TMAO quartiles (P interaction=0.92). Conclusions Among patients with prior myocardial infarction, higher TMAO levels were associated with cardiovascular death and stroke but not with recurrent myocardial infarction. The efficacy of ticagrelor was consistent regardless of TMAO levels. Registration URL: https://www.clini​caltr​ials.gov; Unique identifiers: PEGASUS‐TIMI 54, NCT01225562

Inflammatory Markers and Outcomes in Cardiovascular Disease

In a commentary on two new research studies in PLoS Medicine, Leonard Kritharides discusses the role of inflammatory markers in predicting cardiovascular outcomes and patients' responses to treatment

Prospective Evaluation of Pregnancy-Associated Plasma Protein-A and Outcomes in Patients With Acute Coronary Syndromes

ObjectivesThis study sought to investigate whether pregnancy-associated plasma protein-A (PAPP-A) is useful for risk assessment in non–ST-segment elevation acute coronary syndrome (NSTE-ACS).BackgroundPAPP-A is a high molecular weight, zinc-binding metalloproteinase that is associated with vulnerable plaque and may be a predictor of cardiovascular disease and mortality.MethodsWe measured PAPP-A at baseline in 3,782 patients with non NSTE-ACS randomized to ranolazine or placebo in the MERLIN–TIMI 36 (Metabolic Efficiency With Ranolazine for Less Ischemia in Non-ST Elevation Acute Coronary Syndromes) trial and followed for an average of 1 year. A cut point of 6.0 μIU/ml was chosen from pilot work in this cohort.ResultsPAPP-A >6.0 μIU/ml at presentation was associated with higher rates of cardiovascular death (CVD) or myocardial infarction (MI) at 30 days (7.4% vs. 3.7%, hazard ratio [HR]: 2.01; 95% confidence interval [CI]: 1.43 to 2.82; p < 0.001) and at 1 year (14.9% vs. 9.7%, HR: 1.63; 95% CI: 1.29 to 2.05; p < 0.001). PAPP-A was also associated with higher rates of CVD (HR: 1.94; 95% CI: 1.07 to 3.52, p = 0.027) and myocardial infarction (HR: 1.82; 95% CI: 1.22 to 2.71, p = 0.003) individually at 30 days. There was no difference in the risk associated with PAPP-A stratified by baseline cardiac troponin I [Accu-TnI >0.04 μg/l], p interaction = 0.87). After adjustment for cardiac troponin I, ST-segment deviation, age, sex, diabetes, smoking, hypertension, and coronary artery disease, PAPP-A was independently associated with CVD/myocardial infarction at 30 days (adjusted HR: 1.62, 95% CI: 1.15 to 2.29; p = 0.006) and 1 year (adjusted HR: 1.35, 95% CI: 1.07 to 1.71; p = 0.012). PAPP-A also improved the net reclassification for CVD/MI (p = 0.003). There was no significant interaction with ranolazine.ConclusionsPAPP-A was independently associated with recurrent cardiovascular events in patients with NSTE-ACS. This finding supports PAPP-A as a candidate prognostic marker in patients with ACS and supports investigation of its therapeutic implications

Efficacy and Safety of Evolocumab in Reducing Lipids and Cardiovascular Events

BACKGROUND: Evolocumab, a monoclonal antibody that inhibits proprotein convertase subtilisin-kexin type 9 (PCSK9), significantly reduced low-density lipoprotein (LDL) cholesterol levels in short-term studies. We conducted two extension studies to obtain longer-term data. METHODS: In two open-label, randomized trials, we enrolled 4465 patients who had completed 1 of 12 phase 2 or 3 studies ("parent trials") of evolocumab. Regardless of study-group assignments in the parent trials, eligible patients were randomly assigned in a 2:1 ratio to receive either evolocumab (140 mg every 2 weeks or 420 mg monthly) plus standard therapy or standard therapy alone. Patients were followed for a median of 11.1 months with assessment of lipid levels, safety, and (as a prespecified exploratory analysis) adjudicated cardiovascular events including death, myocardial infarction, unstable angina, coronary revascularization, stroke, transient ischemic attack, and heart failure. Data from the two trials were combined. RESULTS: As compared with standard therapy alone, evolocumab reduced the level of LDL cholesterol by 61%, from a median of 120 mg per deciliter to 48 mg per deciliter (P<0.001). Most adverse events occurred with similar frequency in the two groups, although neurocognitive events were reported more frequently in the evolocumab group. The risk of adverse events, including neurocognitive events, did not vary significantly according to the achieved level of LDL cholesterol. The rate of cardiovascular events at 1 year was reduced from 2.18% in the standard-therapy group to 0.95% in the evolocumab group (hazard ratio in the evolocumab group, 0.47; 95% confidence interval, 0.28 to 0.78; P=0.003). CONCLUSIONS: During approximately 1 year of therapy, the use of evolocumab plus standard therapy, as compared with standard therapy alone, significantly reduced LDL cholesterol levels and reduced the incidence of cardiovascular events in a prespecified but exploratory analysis. (Funded by Amgen; OSLER-1 and OSLER-2 ClinicalTrials.gov numbers, NCT01439880 and NCT01854918.)

Potentiation of thrombus instability: a contributory mechanism to the effectiveness of antithrombotic medications

© The Author(s) 2018The stability of an arterial thrombus, determined by its structure and ability to resist endogenous fibrinolysis, is a major determinant of the extent of infarction that results from coronary or cerebrovascular thrombosis. There is ample evidence from both laboratory and clinical studies to suggest that in addition to inhibiting platelet aggregation, antithrombotic medications have shear-dependent effects, potentiating thrombus fragility and/or enhancing endogenous fibrinolysis. Such shear-dependent effects, potentiating the fragility of the growing thrombus and/or enhancing endogenous thrombolytic activity, likely contribute to the clinical effectiveness of such medications. It is not clear how much these effects relate to the measured inhibition of platelet aggregation in response to specific agonists. These effects are observable only with techniques that subject the growing thrombus to arterial flow and shear conditions. The effects of antithrombotic medications on thrombus stability and ways of assessing this are reviewed herein, and it is proposed that thrombus stability could become a new target for pharmacological intervention.Peer reviewedFinal Published versio