The University of Glasgow ECG Analysis Algorithm is Not Specific for the Pre-hospital diagnosis of STEMI in Patients with Bundle Branch Block

Introduction: In NSW, the University of Glasgow ECG Analysis Algorithm (UGA) is used for the pre-hospital diagnosis of STEMI, because of reported high sensitivity for diagnosis of STEMI. However its specificity has been questioned. We hypothesised that in left or right bundle branch block (LBBB or RBBB), or left ventricle hypertrophy (LVH) the UGA leads to false positive pre-hospital STEMI diagnoses. Methods: ECGs were transmitted by paramedics using LIFEPAK15 units with UGA interpretation capability to interventional cardiologists at Liverpool Hospital, Australia (2010 to 2013). Independent and blinded adjudication of LBBB, RBBB, LVH and STEMI was performed retrospectively by two cardiology trainees with 20% cross-reading by an interventional cardiologist according to guideline definitions and the Third Universal Definition (3rd UD) of Myocardial Infarction. Disagreements were resolved by consensus. Results: Out of 580 UGA STEMI positive transmissions, 137 (24%) were excluded (61 with missing information and 76 were duplicate/serial transmissions). Of the 443 included transmissions, 260 (59%) were adjudicated as STEMI, 43 LBBB, 49 RBBB, and 72 LVH. STEMI was adjudicated in 16% of LBBB (7/43), 24% of RBBB (12/49) and 47% of LVH (34/72). LBBB and RBBB were associated with false positive transmissions according to the 3rd UD (Pearson Chi-Square, P = 0.01 and P < 0.001 respectively). LVH was not associated with false-positive diagnoses (P = 0.073). Conclusions: When using the UGA as a triage tool for the pre-hospital diagnosis of STEMI, LBBB and RBBB are associated with false positive diagnoses according to 3rd UD.