This is a feasibility study aiming to generate pilot data on safety and efficacy of a novel anticoagulant regimen (enoxaparin bolus and prolonged infusion) compared to the local standard-of-care in opiate-treated patients undergoing primary percutaneous coronary intervention.

Delayed absorption of oral P2Y12 inhibitors in patients undergoing primary percutaneous coronary intervention (PPCI) may increase the risk of stent thrombosis. Parenteral treatment is needed mitigate this risk.

We have recently shown a novel regimen of enoxaparin (bolus 0.75 mg/kg followed by an infusion of 0.75 mg/kg/6h) to provide consistent antithrombotic effects until the end of the infusion (1). We have also demonstrated the high prevalence of delayed platelet inhibition in opiate-treated patients (1).

This is a feasibility study for a larger randomised controlled trial (RCT). We aim to assess recruitment rate and collect pilot data on safety and efficacy. This will be a single-centre, open-label RCT comparing this novel regimen of enoxaparin to the local standard-of-care which usually consists of unfractionated heparin and a glycoprotein IIb/IIIa inhibitor. The study population will be opiate-treated patients undergoing PPCI. Pre PPCI, patients will be allocated in 1:1 ratio using a simple randomisation method using sealed envelopes, to either enoxaparin 0.75 mg/kg bolus followed by 0.75 mg/kg infusion over 6 hours (n=50) or the standard-of-care of UFH and tirofiban (n=50).

Inclusion Criteria:

• Age >18
• Confirmation of the diagnosis of STEMI by the clinical team on the basis of history and ECG changes
• Intention to proceed with PPCI
• Treated with opiates for analgesia
• Feasibility to obtain informed verbal consent pre PPCI

Exclusion Criteria:

• Active bleeding that cannot be controlled by local measures
• Pregnant patients
• Patients with end-stage renal failure requiring renal replacement therapy
• Patients with cardiogenetic shock
• Known thrombocytopenia (Platelet count <100,000)
• Known history of intracranial haemorrhage
• Known current treatment with oral anticoagulants
• Known history of major surgery or trauma or history of GI/GU haemorrhage within the last month
• Known intracranial malignancy or aneurysm
• Known allergy to enoxaparin
• known hypersensitivity to benzylalcohol
• Patients with known acute bacterial endocarditis
• Known active gastric or duodenal ulceration
• Inability to easily understand verbal information given in English for any reason
• Inability to give informed consent due to either temporary or permanent mental incapacity
• Current participation, or participation within the last month, in an interventional clinical trial.