Prehospital management of acute myocardial infarction: Electrocardiogram acquisition and interpretation, and thrombolysis by prehospital care providers

Abstract

Objective: To review prehospital management of patients with suspected ST elevation acute myocardial infarction (AMI) based on the acquisition and interpretation of electrocardiograms (ECGs), and the effects of thrombolytic therapy initiated by prehospital care providers.

Design: MEDLINE was searched by combining the search phrases 'thrombolysis,' 'paramedics' and 'myocardial infarction' to identify all pertinent articles. The bibliographies were reviewed to search for other relevant articles.

Results: The earlier that treatment is initiated in AMI, the better the prognosis. Multiple randomized and nonrandomized trials indicate that prehospital care providers (including paramedics, nurses and doctors) are able to acquire prehospital ECGs with negligible increases in on-scene time, ranging from 30 s to 7 mins. With minimal training, they are capable of accurately interpreting ECGs and diagnosing ST elevation AMI, with results comparable with control ECGs obtained by physicians. Numerous studies have investigated the role of specially trained prehospital personnel in initiating thrombolysis. Trials outside of North America have predominantly used physicians, whereas North American studies employed paramedics. Thrombolysis has been shown to be safe and effective when started outside the hospital by physicians or paramedics, with a reduction in time to treatment and no increase in complications. The further a patient with ST elevation AMI is from hospital, the greater the potential benefit of prehospital thrombolysis. The European Myocardial Infarction Project (EMIP), the largest randomized trial of prehospital thrombolysis, demonstrated a trend towards reduced mortality but was underpowered to detect significant mortality differences. The Grampian Region Early Anistreplase Trial (GREAT), a rural study, is the only randomized trial to demonstrate a statistically significant mortality difference in patients receiving prehospital thrombolysis. Despite trends in favour of prehospital diagnosis and treatment of AMI, no urban study has been sufficiently powered to demonstrate mortality benefits.

Conclusion: Prehospital treatment of patients with chest pain using ECGs and thrombolysis is safe. Though rural patients have significant reductions in total mortality when treated with thrombolysis in a prehospital setting, this has not been documented with an urban population. Prehospital identification of thrombolysis-eligible patients with ST elevation AMI via acquisition and interpretation of ECGs followed by triage to a hospital 'lytic team' has the potential to improve patient outcome and requires further investigation. A prehospital paramedic program for identifying and treating thrombolysis-eligible patients requires intensive planning, retrospective feasibility work, implementation and monitoring to establish effectiveness.