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In the absence of clinician overread, prehospital computer electrocardiographic (ECG) identification of ST-segment elevation myocardial infarction (STEMI) is associated with high rates of inappropriate (IA) cardiac catheterisation laboratory (CCL) activations. Perhaps surprisingly, patients with suspected STEMI and CCL nonactivation have a higher adjusted risk of death than those with CCL activation, though the reasons for these outcomes are unclear. The first two studies included in this thesis examined the utility of prehospital ECG interpretation in STEMI utilising computer interpretation and transmission for interventional cardiologist consultation and provide explanations for these outcomes. Patients with STEMI undergoing rescue percutaneous coronary intervention (PCI) are at high risk of bleeding complications. Bivalirudin is a direct thrombin inhibitor with pharmacokinetic and pharmacodynamic advantages over heparin, though this has not been investigated in patients undergoing rescue PCI. The third study was a randomised controlled trial (RCT) that aimed to determine if bivalirudin compared with heparin ± glycoprotein IIb/IIIa inhibitors (GPIs) reduces bleeding in this context. The first study examined the appropriateness of prehospital CCL activation in STEMI utilising the University of Glasgow algorithm (UGA) and transmission for interventional cardiologist consultation. This strategy accurately identified STEMI with low rates of IA CCL activations and nonactivations, whereas using UGA alone would have almost doubled CCL activations. The second study determined late outcomes among patients with prehospital ECG STEMI criteria who had CCL nonactivation compared with activation. CCL nonactivation was not primarily due to missed STEMI but due to ‘masquerading’ with high rates of non-STEMI and myocardial injury. These patients had worse outcomes than those with CCL activation, mainly due to higher rates of noncardiovascular deaths. The third study was an RCT that compared bivalirudin with heparin ± GPIs in rescue PCI. The primary safety endpoint was any ACUITY (Acute Catheterization and Urgent Intervention Triage Strategy) bleeding at 90 days. There was no significant difference in the primary safety endpoint between the two groups. The trial was terminated due to slow recruitment and futility, so whether bivalirudin compared with heparin ± GPIs reduces bleeding in patients undergoing rescue PCI could not be determined.