Background The American College of Cardiology and the American Heart Association recommend early aspirin administration to patients with symptoms of acute coronary syndrome (ACS)/acute myocardial infarction (AMI). The primary objective of this study was to determine if Emergency Medical Dispatchers (EMD) can provide chest pain/heart attack patients with standardised instructions effectively, using an aspirin diagnostic and instruction tool (ADxT) within the Medical Priority Dispatch System (MPDS) before arrival of an emergency response crew.

Methods This retrospective study involved three dispatch centres in the UK and USA. We analysed 6 months of data involving chest pain/heart attack symptoms taken using the MPDS chest pain and heart problems/automated internal cardiac defibrillator protocols.

Results The EMDs successfully completed the ADxT on 69.8% of the 44 141 cases analysed. The patient's mean age was higher when the ADxT was completed, than when it was not (mean±SD: 53.9±19.9 and 49.9±20.2; p<0.001, respectively). The ADxT completion rate was higher for second-party than first-party calls (70.3% and 69.0%; p=0.024, respectively). A higher percentage of male than female patients took aspirin (91.3% and 88.9%; p=0.001, respectively). Patients who took aspirin were significantly younger than those who did not (mean±SD: 61.8±17.5 and 64.7±17.9, respectively). Unavailability of aspirin was the major reason (44.4%) why eligible patients did not take aspirin when advised.

Conclusions EMDs, using a standardised protocol, can enable early aspirin therapy to treat potential ACS/AMI prior to responders' arrival. Further research is required to assess reasons for not using the protocol, and the significance of the various associations discovered.