The aim of the study is to assess whether a decision aid that is currently used in hospitals across Greater Manchester to determine how likely it is that a patient has a serious heart problem is still accurate in the pre-hospital environment.

The Investigators will aim to recruit up to 700 participants, aged 18-100, who call 999 with a complaint of chest pain and are subsequently attended by the ambulance service. A blood sample will be taken in the ambulance as well as information about the participant's symptoms, past medical history, physical examination findings and heart tracing findings. The participant will then be transferred to hospital, where another blood sample will be taken. Both of these blood samples will be analysed at a later date for the cardiac marker, troponin.

Participants will then be followed up after 30 days via screening of their clinical records and contacting their GP. The investigators will gather information on the participant's initial admission to hospital, as well as any further hospital admissions and investigations that have occurred within the 30 days since this admission. The information collected will include data on serial cardiac marker testing; other laboratory analyses; length of stay; all imaging investigations and procedures; and details of any haemorrhagic complications.

Inclusion Criteria:

• Adult patients (>18 years)
• Called 999 for an emergency ambulance because they have experienced pain, discomfort or pressure in the chest, epigastrium, neck, jaw or upper limb without an apparent non-cardiac source
• Treating paramedic suspects these symptoms may be caused by acute coronary syndromes.

Exclusion Criteria:

• Patients with unequivocal evidence of ST elevation myocardial infarction who are being immediately transferred for primary percutaneous coronary intervention
• Patients in whom an alternative diagnosis (other than acute coronary syndromes) is suspected, which would necessitate transfer to hospital
• Patients who have not experienced symptoms in the previous 24 hours
• Patients who lack the capacity to provide written informed consent, either because they lack the mental capacity to provide written informed consent or because effective communication is not possible (e.g. non-English speakers in the absence of adequate translation services)

The study will recruit patients who have called 999 with a complaint of pain, discomfort or pressure in the chest, who are then attended by an ambulance.