Introduction A chest pain pathway was introduced in 2013 using the Abbott hs-cTnI assay. This incorporates a zero hour subnormal limit of less than 2 ng/l. If a patient has a hs-cTnI of <2 ng/l at zero hours, the ECG is not ischaemic and Acute Coronary Syndrome (ACS) is clinically felt to be unlikely then an ACS is considered to have been ruled out and the patient can be discharged immediately. We also incorporated the use of a Clinical Decisions Unit (CDU) for low risk patients whilst awaiting a zero and, when indicated, a repeat 6 h hs-cTnI.

Methods We examined data from 3853 patients presenting to the Emergency Department with chest pain from July 2013 to January 2014. We also looked at 473 patients from July 2012 before the new troponin test was introduced to compare lengths of stay. All chest pain presentations and patients who had a hs-cTnI sent were included. Trauma calls, patients who did not wait and those under 16 years of age were excluded. In 2573 patients there was a clinical suspicion of ACS and hs-cTnI levels were taken immediately.

Results 1280 patients (33.2%) had an ACS ruled out clinically. 2573 (66.8%) had a zero hour hs-cTnI sent. 849 of these 2573 (32%) had a hs-cTnI of <2 ng/l – of these 161 were admitted, 51 had a second hs-cTnI sent at 6 h and 688 were discharged from the Emergency Department. 30 day follow up of these 849 patients showed 3 Major Adverse Cardiac Events (MACE) – two deaths (one unrelated malignancy and one peri-arrest sample) and one Percutaneous Cornonary Intervention (PCI), but no non-fatal myocardial infarctions (MI) and no re-presentations with ACS. 9 month follow-up showed 14 MACE. There were 11 deaths (9 unrelated malignancy, one pulmonary fibrosis and one peri-arrest sample) and three PCIs were performed, one as an in-patient and two electively. There were no non-fatal MIs and no re-presentations with ACS.

The introduction of the new hs-cTnI test at zero hours compared with a single 12 h troponin reduced admissions with chest pain from 60.9% to 53.2% (p < 0.001). The introduction of CDU in January 2014 further reduced admissions from 53.2% to 38.4% (p < 0.001). Length of stay fell from a mean of 23 h 2 min with a single 12 h troponin to 16 h 34 min with hs-cTnI (p = 0.02) and further to 9 h 36 min with the introduction of CDU (p = 0.001). The negative Predictive Value of hs-cTnI <2 ng/l at zero hours for MACE on that admissions is 99.88%, at 30 days is 99.65% and at 9 months is 98.35%.

Conclusions In patients presenting with acute chest pain who are felt unlikely to have an ACS and whose ECGs are normal, a single hs-cTnI of <2 ng/l at zero hours can safely rule out an ACS and allow early discharge with significant reductions in length of stay. Length of stay can be further reduced by utilising a CDU.