Differentiation of type 1 (T1MI) from type 2 myocardial infarction (T2MI) is important as recommended treatments for each differ. Patients with T2MI may have more/earlier cardiac wall stress resulting in an increased N-terminal pro B-type natriuretic peptide (NT-proBNP)/cTnT generation 5 ratio (cTnT Gen 5).

Emergency Department (ED) patients presenting with symptoms suspicious for acute coronary syndrome (ACS) were enrolled from 2013 to 2015. Baseline blood samples were collected within 60 min of a triage ECG, with additional draws at 30, 60 and 180 min. NT-proBNP and cTnT Gen 5 levels were measured later in an independent laboratory. Acute myocardial infarction (AMI) was adjudicated using the Third Universal Definition of Myocardial Infarction.

575 patients were enrolled with 44 (7.7%) having AMI [25 T1MI (59.1%) and 18 T2MI (40.9%)]. Patient characteristics showed very few AMI type differences so accurate clinical differentiation was difficult. The median NT-proBNP/cTnT Gen 5 ratios were significantly higher in T2MI when compared to T2MI at baseline and 30, 60 and 180 min later [7.3 v 53.0 (p = 0.003), 5.8 v 49.5 (p = 0.002), 6.3 v 47.5 (p = 0.003) and 4.3 v 33.7 (p = 0.016) respectively].

The clinical determination of whether an AMI is type 1 or 2 is difficult as the ED patient characteristics of each are similar. The NT-proBNP/cTnT Gen 5 ratio can aid in making this differentiation. Additional multicenter trials are needed to validate our results.