An electrocardiograph (ECG) consists of an assessment of cardiac electrophysiology and a complex diagnostic of heart health. During emergency situations, a high degree of importance is assigned to ECG interpretation. As first responders, ambulance personnel need a strong understanding of the ECG to assess a patient’s needs quickly and accurately. However, the cardiac electrophysiology of an ECG is an intangible and complex system with clinical indicators commonly deemed difficult to comprehend. Interpretation remains an ongoing challenge for new and experienced paramedics and novel ways to support interpretation are needed. An interactive Augmented Reality mobile application which conveys a 3D anatomical heart model alongside varying clinical ECG presentations to enhance user knowledge of cardiac electrophysiology, was developed. The usability and effectiveness of the application was tested on a cohort of newly qualified paramedics (NQP’s) in the SAS, using the System Usability Scale, and comparing initial and post intervention knowledge of ECG interpretation. Ten NQP’s agreed to participate. Knowledge significantly increased an average of 22% from pre- (M = 4.8 ± 1.62) to post-test (M = 7.0 ± 1.49) scoring. The application received an average usability score of 82.8, 24.8 points higher than the SUS standardised reference benchmark of 68. Improving interpretation of ECG may improve paramedics’ diagnostic accuracy and therefore impact positively on patient outcome. Our experimental findings suggest the current efficacy of the application in facilitating user knowledge and support recommendations for future research. Though, further testing is needed to confirm the current trends and validate the application in a medical context.