The aim of this observational study registry is to assess the safety of a Non-ST-elevation myocardial infarction (STEMI) rapid rule-out strategy as proposed by European Guidelines in patients presenting with suspected acute coronary syndrome to the emergency department.

Design: mono-center observational study in a University chest pain unit

Duration: 12 months recruitment period starting June 2016 with end of recruitment July 2017. In the first 6 months assessment of situation, January 2017 introduction of fast protocols, i.e. 0/1 h as standard, observation of trend changes, utilization rates, safety from January 1st until July 2017. Another 90 days follow-up after last patient in.

Background: Several rule-out protocols recommended by 2015 European Society of Cardiology (ESC) guidelines, evidence supported by prospectively validated studies. However, no real life experience with ultilization rates and safety.

Particularly overcrowded emergency departments (EDs) or CPUs are likely to benefit most from fast rule-out protocols in order to discharge a substantial proportion of low risk patients.

Study group: consecutive patients presenting to CPU with suspected acute coronary syndrome (ACS) based on chest pain or chest pain equivalent symptoms

Inclusion criteria: eligible to consent, > 18 years

Exclusion criteria: rule-in, observational zone, chronic hemodialysis, no consent, atrial tachyarrhythmias with chest pain or equivalent.

Data collection on: demographics, rule-out diagnostic protocol (instant cardiac troponin+Copeptin, instant at Limit of Detection, 0-1h, 0-3 h, 0-6 hour, other; time of second sample from admission; turnaround time for first and consecutive sample(s); rates of echo, computed tomography (CT) coronary or CT pulmonary artery, CT chest or CT triple rule-out, chest X-ray, stress test performed or recommended within 3 working days; length of stay in ED, length of stay in hospital including initial referral; rates of admission, discharge or referral; rates of in-hospital percutaneous coronary Intervention (PCI) or coronary artery Bypass graft (CABG), coronary angiography findings based on a definition of obstructive coronary artery disease (CAD) ≥ 50% stenosis.

Specific data: Number of patients seeking attendance in CPU per day (crowding index), GRACE score, secondary risk factors present or not (leftventricular ejection fraction (LVEF) < 40%, glomerular filtration rate< 60 ml/min, Diabetes mellitus, previous myocardial infarction (MI), previous CABG, prior PCI, ST segment depression). Rule-out protocols are stratified by hour ± 30 min, i.e. 0-1 h (±30 min), 0-2 h (±30 min), 0-3 h (±30 min) etc.

Clinical work-up results: stress test before discharge positive or negative, transthoracic echocardiography: wall motion abnormalities, LVEF, valvular heart disease, structural heart disease, Endpoint(s): primary safety endpoint defined as survival free of all-cause death, secondary endpoints: survival free of death or MI, survival free of death/MI/re-hospitalisation for ACS, survival free of death/MI/rehospitalisation for non-elective revascularization

Follow-up: 30 days and 3 months follow-up (FU) for all-cause death, MI, re-hospitalisation for ACS, re-hospitalisation for non-elective PCI or CABG Statistical plan: no sample size calculation, Student´s T-test, ANOVA, Kaplan Meier survival, Cox proportional regression analysis

Milestones: Start immediately after contract for a recruitment period 9/16 - 9/17 (12 months) plus 3 months FU after last patient in. Additional 3 months for completion of files and FU data.

Inclusion Criteria:

• eligible to consent
• >18 years

Exclusion Criteria:

• NSTEMI rule-in
• hs-TnT in observational zone
• chronic hemodialysis
• no consent
• atrial tachyarrhythmias with chest pain or equivalent

Consecutive patients presenting to CPU with suspected ACS based on chest pain or chest pain equivalent symptoms