Page 25 - Biomarkers for risk stratification and guidance in heart failure
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                                Chapter 2
METHODS
Study population and design
Between June 2007 and October 2009, patients who presented to the cardiology ED of the Maastricht University Medical Center with dyspnea – either at rest or during physical activity - were consecutively enrolled in this prospective study. Patients were eligible if they were ≥18 years old and dyspnea was their main complaint. Patients referred for therapeutic treatment or patients that required immediate therapeutic action (e.g percutaneous coronary intervention or electrical or chemical cardioversion) and patients with dyspnea resulting from chest trauma were excluded. Also, not all physicians in our department participated in the trial and patients that were seen by nonparticipating physicians were not included. All patient characteristics were based on clinical chart review. Left ventricular ejection fraction (LVEF) was obtained from echocardiography when available within a range of 1 year before presentation to 1 month after presentation. Presence of coronary artery disease was defined as having a history of coronary artery bypass grafting, percutaneous coronary intervention, acute myocardial infarction or obstructive coronary artery disease on coronary angiography or CT angiography. Patients were followed for 1 year. Follow-up data was obtained via chart review and, if necessary, from the general practitioner or by enquiry of the municipal register. Primary outcome measure was 90-day all-cause mortality. Secondary outcome measures encompassed 90-day cardiovascular mortality as well as in-hospital, 30 day and 1 year all-cause and cardiovascular mortality. All investigational procedures involved in this study have been approved by the institutional review board (Medical Ethical Committee MUMC) and comply with the Declaration of Helsinki.
Biochemical analysis
Blood samples were obtained on patient arrival at the ED. Measurements of several laboratory parameters, e.g NT-proBNP, conventional cTnT, blood urea nitrogen (BUN), haemoglobin and creatinine were performed immediately after blood collection. Excess of collected serum sample was frozen and aliquots were stored at -80°C until analyzed. Hs-cTnT, hs-CRP, Cys-C and Gal-3 concentrations were measured in 2010 (1 freeze-thaw cycle). Detailed information about the assays and their performance characteristics is provided in appendix 1.10, 16-20
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